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Thèse de doctorat/ PhD Thesis Citation APA:
Simonart, T. (s.d.). Sex, iron and Kaposi's sarcoma (Unpublished doctoral dissertation). Université libre de Bruxelles, Faculté de Médecine – Médecine,
Bruxelles.
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SEX, IRON AND KAPOSI’S SARCOMA
Thierry Simonart, MD
Department of Dermatology, Erasme University Hospital
Promotor; Jean-Paul Van Vooren, MD, PhD (Department of Internai Medicine) Co-promotor: Michel Heenen, MD, PhD (Department of Dermatology, Head of Department)
1/ INTRODUCTION I ...HISTORY
II ... INCIDENCE AND EPIDEMIOLOGY II.l Epidemiologlcal forms of KS
II.2 Particular features of the KS epidemiology 11.2.1 Géographie variation
11.2.2 Variation by âge
11.2.3 Variation by sexual behavior 11.2.4 Variation by sex 11.2.5 Variation by race/ethnicity III ... HISTOPATHOLOGY 111.1 Descriptive histology of KS 111.2 Immunophénotype of KS 111.3 Proliférative activitv of KS IV ...CLINICAL SPECTRUM V ...PATHOGENESIS
V. 1 Spindle cells and their Products as the driving force of KS pathogenesis V.2 Escape from programmed cell death
V.2.1 Rôle of the Bcl-2 protein V.2.2 Rôle of the p53 protein V.2.3 Rôle of the CD40 antigen
V.2.4 Résistance to Fas-mediated apoptosis V.3 Rôle of viral agents in KS
V.3.1 Epidemiology suggestive of a sexually transmitted disease V.3.2 Détection of viral agents in KS
V.3.3 Direct and indirect rôle of HIV
V. 3.4 Rôle of human herpesvirus 8 (HHV-8) VI ... TREATMENT
VI. l Local treatment VI.2 Svstemic treatment VI.2.1 Chemotherapy VI.2.2 Interferon
VI.2.3 Antiviral strategies
VI.2.6 Angiogenesis inhibitory strategies VII...SUMMARY
2/ SUMMARY OF MAIN OBSERVATIONS
Simonart Th, Van Vooren JP, Noël JC, Liesnard C, Farber CM, Parent D. High
prevalence of cutaneous infections in AIDS patients with Kaposi's sarcoma: insight into the rôle of human herpesvirus 8? AIDS 1997; 11: 824-6.
Simonart T, Noël JC, De Dobbeleer G, Parent D, Van Vooren JP, De Clercq E, Snoeck R. Treatment of classical Kaposi’s sarcoma with intralesional injections of
cidofovir: Report of a case. J Med Virol 1998; 55: 215-8.
Simonart T, Noël JC, De Clercq E, Snoeck R. Abatement of Kaposi’s sarcoma with cidofovir therapy [letter]. Clin Infect Dis, 1998; 27: 1562.
Simonart T, Degraef C, Noël JC, Fokan D, Zhou L, Pradier O, Ducarme M, Schandene L, Van Vooren JP, Parent D, Heenen M. Overexpression of Bcl-2 in Kaposi’s sarcoma-derived cells. JInvest Dermatol 1998; 111: 349-53.
Simonart T, Noël JC, Andrei G, Parent D, Van Vooren JP, Hermans P, Lunardi-Yskandar Y, Lambert C, Dieye T, Farber CM, Liesnard C, Snoeck R, Heenen M, Boelaert JR. Iron as a potential cofactor in the pathogenesis of Kaposi’s sarcoma.
Int J Cancer 1998; 78: 720-6.
Simonart T, Van Vooren JP, Herbauts J, Boelaert JR. High prevalence of Kaposi’s sarcoma in Iceland and the Faroe Islands [letter]. Br J Cancerl999; 79: 37.
Simonart T, Noël JC, Van Vooren JP, De Dobbeleer G. Classic Kaposi’s sarcoma after mutli-partner heterosexual behavior in Central Africa. J Am Acad Dermatol, in press.
Simonart T, Degraef C, Noël JC, Mosselmans R, Van Vooren JP, Parent D, Boelaert JR, Heenen M, Galand P. Iron Increases the Bcl-2/Bax Ratio in Human Dermal Microvascular Endothélial Cells. Submitted for publication.
3/ DISCUSSION
4/SUMMARY
5/ANNEXS
This Work could not hâve been accomplished without the excellent contribution of the followingpersons whom I would like to thank for both scienti/îc and human continuons
support
Dr. Van Vooren JP (Department of Internai Medicine, Hôpital Universitaire Erasme, Brussels)
Pr. Parent D, Pr. Heenen M (Department of Dermatology, Hôpital Universitaire Erasme, Brussels)
Dr. Andréi G, Dr. Snoeck R (Rega Institute for Medical Research, Katholische Universiteit Leuven, Leuven)
M. Degraef C (Laboratory of Cytology and Experimental Cancerology, Free University of Brussels, Brussels)
Dr. Noël JC (Department of Pathology, Erasme University Hospital, Brussels) Dr. BoelaertJR (Department Of Infections Diseases, Algmeen Ziekenhuis StJan, Brugge)
I am indebted to Pr. Galand P (Laboratory of Cytology and Experimental
Cancerology, Free University of Brussels, Brussels) and to Pr. De Clercq E (Rega Institute for Medical Research, Katholische Universiteit Leuven, Leuven) for their expert advice and suggestions
I am also very grateful to the following persons for their co-operation and helpful discussions
Dr. Brancart F, Dr. LiesnardC (Department ofVirology, Hôpital Universitaire Erasme, Brussels)
Pr. De Dobbeleer G (Department of Dermatology, Hôpital Universitaire Erasme, Brussels)
Mr. Decock M (Laboratory of Respiratory Physiology)
Dr. Dieye T, Dr. Farber CM (Department of Internai Medicine, Hôpital Universitaire Erasme, Brussels)
M. Ducarme M, Dr. Pradier O, Dr. Schandene L, Ms. Zhou L (Department of Immuno-haematology, Hôpital Universitaire Erasme l, Brussels)
Dr. Lambert C, Pr Lapière C (Laboratory of Connective Tissues Biology, CHU Sart Tilman, Liège, Belgium)
Pr. Lunardi-Yskandar (Institute ofHuman Virology, Baltimore, MA, USA)
Pr. Werenne J (Laboratory of Biotechnology, Solbosch, Free University of Brussels, B rus sels)
1/ INTRODUCTION
I ...HISTORY
II ... INCIDENCE AND EPIDEMIOLOGY III ... HISTOPATHOLOGY
IV ... CLINICAL SPECTRUM V ... PATHOGENESIS
In 1872, Moritz Kaposi reported five patients with blue-red cutaneous tumors which he called ‘idiopathic pigmented sarcoma of the skin’ [Kaposi, 1872], later named Kaposi’s sarcoma (KS). During the next century, this rare tumor was identified in three different settings: classic KS, Afiican-endemic KS, and iatrogénie immunosuppressive KS, seen predominantly in organ transplant récipients. KS emerged from relative anonymity in 1982 when the Centers for Disease Control (CDC) reported 26 cases in homosexual men in California and New York City, conftrming a relation between KS and the acquired immune deficiency syndrome (AIDS) [Tappero
et ai, 1993], Ail these forms of KS share a common histology characterized by
Il.l Epidemiological forms of KS
KS occurs in four distinct subsets: classic KS, African-endemic KS, iatrogénie KS and AIDS-associated KS (table 1). It remains uncertain whether these four epidemiological forms correspond to a single disease or not.
Classic KS
In its classic form, KS is an uncommon neoplasm that usually affects persons older than 50 years of âge with a distinct male prédominance. The incidence of this classic form of KS differs considerably between Caucasian populations. The highest incidence rates are noted in Ashkenazic Jews and individuals of Mediterranean origin. Reported aimual rates per 100,000 persons vary ffom 1.8 in Sardinia to 0.014 in the UK [Wahman et a/.,1991; Hjalgrim et ai, 1998]. A surprisingly high incidence of classic KS has also been registered in Iceland and the Faroe Islands [Hjalgrim et al., 1998]. A higher prevalence of this tumor among certain ethnie groups and in particular géographie régions suggests the existence of predisposing genetic or environmental factors.
Although classic KS has been reported in members of a same family, familial occurrences are very rare [Friedman-Kien and Saltzman, 1990].
African-endemic KS
One study performed in a population of young adults with endemic KS found no evidence of underlying immunodefïciency [Kestens et al., 1985].
Iatrogénie, immunosuppressive, drug-associated KS
Iatrogénie KS bas been described in organ transplant récipients and in a wide spectrum of patients receiving chronic immunosuppressive drug therapy. KS develops in approximately 0.5% of organ transplant récipients [Zalla 1996] and accounts for 3 to 6% of ail malignancies developing in this group, arising on average 16.5 months after transplantation [Penn 1983]. Rénal transplant récipients appear to be at the highest risk of developing KS, estimated to be 150-200 times the risk incurred by the general population [Harwood et al., 1979], One study found a higher prevalence of KS among liver transplant récipients [Farge 1993]. The type of immunosuppressive drug used has a bearing on the incidence of posttransplant KS. A greater incidence of KS, associated with earlier onset of the disease has been described among patients treated with cyclosporine [Farge, 1993; Penn 1983]. KS accounts for 10% of neoplasias arising de
novo posttransplant in patients treated with cyclosporine, whereas the figure for
spontaneous remission after discontinuation of immunosuppressive therapy is the norm.
AIDS-associated, épidémie KS
Cancer risk is increased with most types of immune deficiency, including congénital disorders and iatrogénie treatments to prevent allograft rejection. With AIDS, cancer risk is extraordinarily high and has an unusual spectrum. So far, three different tumors hâve been clearly associated with AIDS and are considered as AIDS- defming conditions in human immunodeficiency virus (HIV) patients: non-Hodgkin’s lymphoma, invasive cervical carcinoma and KS [CDC, 1992], Other tumors whose incidences are probably increased in HIV-infected patients are invasive squamous cell cacinoma of the anus, Hodgkin’s lymphoma, multiple myeloma, brain cancer, and seminoma [Palefsky, 1994; Goedert et al, 1998], Many other tumors hâve been reported in patients with AIDS. Causal relations between AIDS and these other cancers hâve not been defined because of potential confounding by lifestyle variables, and because of ascertainment bias resulting from the intensive diagnostic scrutiny of people with AIDS.
Epidémie AIDS-associated KS was the AIDS-defming illness in 15% of ail reported U.S. patients reported by the CDC in 1990 [Beral et al., 1990]. On the basis of KS incidence rates in the United States from 1973 to 1979, the overall risk of KS in patients with AIDS is more than 20,000 times that of the general population.
There has been a surprising décliné over time in the ffequency of KS as an AIDS-defining condition [De Jarlais et al, 1987; Beral et al., 1990; Hermans et al,
of highly active antirétroviral therapy (HAART), combining a HIV-1 protease inhibitor and two reverse transcriptase inhibitors bas contributed to a further decrease in the incidence of KS [Forrest et ai, 1998; Lebbé et ai, 1998], In a large French clinical cohort, the incidence of KS has dropped by 65% (from 23/1,000 patients-year to 8/1,000 patients-year) since the introduction of protease inhibitors [Castagliola, for the CISIH, data presented at the ECCATH meeting in Hamburg, 1997], Reporting for the Multicenter AIDS Cohort Study, Jacobson (John Hopkins) saw cases of KS as a presenting AIDS condition swoon ffom 25.6/1,000 person-years in the early 1990s to 7.5 per 1,000 person-years in 1996-1997 {P< 0.001).
Human immunodeficiency virus (HIV) transmission groups run a strikingly different risk of acquiring AJDS-KS. The frequency of KS ranges from a high 21% for homosexual men to a low of 1% for men with hemophilia [Haverkos et al., 1985; Beral et ai, 1990]. The risk of KS among HIV-infected women is markedly lower than that among men. Women who acquire HIV infection by heterosexual contact with bisexual men as opposed to heterosexual intravenous drug users are at increased risk for developing AIDS-KS [Bigger et al., 1985; Beral et al., 1990]. These épidémiologie peculiarities call into question whether a sexually transmitted agent other than HIV may be involved in the pathogenesis of KS.
AIDS-KS may appear at any stage of the viral disease, but usually after some degree of immune impairment [Lane et ai, 1985]. The probability of developing KS in AIDS patients is correlated with the baseline CD4 cell count. In patients with baseline CD4 cell counts lower than 100/mm^, the relative risk of further KS is twofold higher than in patients with cell counts of more than 200/mm^, suggesting that immunosuppression could play a rôle in KS occurrence, either directly or indirectly [Hermans et al., 1996]. Less than 20% of patients presenting with AIDS-KS hâve CD4+ T-cell counts > 500/mm^. Concomitantly with the decreased AIDS-KS incidence since the late 1980s in the United States and early 1990s in Europe, the past decade has also witnessed more frequent development of KS at a later stage of the disease [Dore et
Table 1.
Population at risk
Mean âge at onset Male/female ratio
______(yr)________________________
Classic Ashkenazic Jews, 60-70 3-15/1
Mediterraneans, Icelanders ?
African-endemic Sub-Saharan 25-40 17/1
- Benign nodular Africa Aggressive Black African
}
adults- Florid 3 - 10 1-3/1
- Lymphadenopathic Black African children
Iatrogénie Transplant 10 months (3 - 57) 2.3/1
récipients after transplant
AIDS-related Homosexual men 35-40 106/1
II.2 Particular features of the KS epidemiology
l'he epidemiology of KS is complex. Establishing a cohérent picture of the descriptive epidemiology of KS is problematic. Discussing individual risk factors is difficult because each factor influences the effects of the others, changes over time occur for each risk factor, ethnie background and geography often are strongly associated, and the séparation between the different types of KS may be difficult. For instance, because of the difficulty to distinguish African-endemic KS from AIDS- associated KS without the use of tests for HIV infection, factors such as sexual orientation and géographie location hâve often been used as surrogates to categorize a case.
II.2.1 Géographie variation
The définition of classic KS cases includes référencé to the géographie location of either the patient or the patient’s ancestors. Classic KS is found primarily in people from Mediterranean/southem European countries, and in people with ancestors from these countries. The highest prevalence rates are found in Corsica, Sardinia, Sicily and, Peloponnese. Surprisingly high incidence rates of classic KS were recently reported in Iceland and in the Faroe Islands [Hjalgrim et al, 1998].
instance, in South Africa, KS accounts for only 1% of ail malignancies among blacks [Hutt, 1984],
The high incidence rates of KS in these régions positively correlate with high rates of sero-positivity for a recently discovered human herpesvirus, known as Kaposi's sarcoma (KS)-associated herpesvirus or hmnan herpesvirus 8 (HHV-8) (see § V.3.4). We hâve suggested that another conunon denominator between ail these different régions was the presence of mafic (iron-oxide rich) minerais in the environment [Simonart et al. 1998; Simonart et ai, 1999],
11.2.2 Variation by âge
KS was originally described as occurring among patients in their sixth and seventh décades of life [Hutt, 1984]. The âge of onset of classic KS has changed very little, but some studies hâve reported cases of patients with classic KS who were much younger [Wahman et ai, 1991].
The âge of occurrence of African KS is different ffom that of classic KS. Patients range in âge between 25 and 40 years. Lymphadenopathic KS is seen almost exclusively in prepubescent black African children (mean, 3 years) [Friedmann-Kien and Saltzman, 1990].
11.2.3 Variation by sexual behavior
The possibility of KS being a disease related to sexual transmission was not investigated before the AIDS épidémie. The descriptions of KS among elderly men with classic KS indeed did not include information on sexual orientation.
Epidemiologie features strongly suggest that AIDS-associated KS may be due to a sexually transmitted pathogen distinct from HIV.
low 1% for men with hemophilia [Haverkos et ai, 1985; Beral et ai, 1990], On the whole, the disease is 7- to 15-fold more common in HIV-positive homosexual men than in other groups who acquire HIV by non-sexual routes [Petennan et al, 1993], .Aithough KS is infrequent in women with HTV infection (see II.2.4), the risk of developing the tumor is higher in those who acquire HIV infection by heterosexual contact with bisexual men than in those who are contaminated by heterosexual contact with intravenous dmg users [Bigger et al, 1985; Beral et al, 1990], Finally, homosexual men living in San Fransisco, as well as Canadian homosexual men commuting to this city were far more likely to develop KS than homosexual men not living in, or commuting to, this area [Archibald et al, 1990; Beral et al, 1990].
Studies evaluating varions types of sexual practice hâve found the risk of developing AIDS-KS to increase with oral-anal contacts (insertive anilingus or rimming), fecal contact (insertive fisting), and with réceptive anal intercourse [Archibald et al, 1990; Jacobson et al, 1990; Abrams et al, 1990; Beral et al, 1992; Peterman et al, 1992; Darrow et al, 1992; Grulich et al, 1997]. Fecal-oral transmission of the KS agent could explain the high incidence of KS in homosexual men as well as in heterosexuals in Africa, where fecal-oral transmission of disease may resuit from poor sanitation. However, other studies found no relation between particular sexual practices and KS development [Elford et al, 1992, Matondo et al, 1992, Page-Bodkin et al, 1992, Casabona 1998]. More particularly, in an European multicentric study, the only significant différence between AIDS patients with KS and those without KS was the number of lifetime sexual partners (400 vs 200, respectively) [Casabona, for the Euroshacks study, data presented at Barcelona, 1998].
of acquiring STD may therefore explain the coexistence of KS and HSV 2 infection. Since the majority of herpetic infections are thought to represent réactivation of latent infection, a particular susceptibility to herpesviruses is another possible explanation of the observed association. We hâve also found a strong association between KS and molluscum contagiosum, a common cutaneous viral infection which, among adults, is currently considered to be sexually transmitted [Fehnan and Nikitas, 1983]. Confirming previous results [Schwartz and Myskowski, 1992], we noted that only a minority of the patients had molluscum contagiosum in the génital or perianal areas. This low percentage of génital lésions in patients with AIDS calls into question sexual contacts as the main mode of transmission. Another possibility is the réactivation of a latent infection, as happens with other DNA viruses in immunocompromised individuals.
Ail together, these fmdings suggest that a sexually transmitted, presumably viral, factor plays a rôle in the pathogenesis of AIDS-KS. Several studies hâve investigated the possible relationship between viral transmissible agents and KS by testing for either sérologie evidence of viral infection in patients with KS or for the presence of viral DNA or RNA in KS tissues and KS-derived cell Unes. Hepatitis B virus, HIV, cytomégalovirus (CMV), human herpesvirus 6, human papilloma virus (HPV) and BK virus hâve been proposed as potential etiological agents for KS. The rôle of these agents in KS pathogenesis is still highly equivocal (see § V.3.2). Numerous studies suggest that a recently discovered herpesvirus, known as human herpesvirus 8 (HHV-8) is the sexually transmitted agent related to KS occurrence (see § V.3.4). Several epidemiogical data regarding the transmission of this agent are not clear-cut. Is this agent transmitted more efficiently sexually than through needle sharing or blood products? Are multiple infectious contacts necessary to transmit the infection or are multiple repeated infections necessary for the agent to manifest itself?
11.2.4 Variation by sex
This male dominance is paiticularly clear for the classic and the Afiican- endemic forms of KS (male/female ratio of 10-15/1 and 10/1, respectively) [Tappero et
ai, 1993; Grulich and Kaldor, ]. This gender différence might be less clear-cut in the
iatrogeinc form of KS, as evidenced by great variations among the reported male-to- female ratios (ranging ffom 1/2 to 41/1) [Grulich and Kaldor, ; Farge, 1993], Among people with AIDS, there is also a higher incidence of the sarcoma in men. Still in Africa, the male to-female ratio of AIDS-associated KS has fallen dramatically since the begiiming of the AIDS épidémie and is now thought to be around 2/1 [Brettle and Leen, 1991; Grulich and Kaldor, 1997]. It remains unclear whether the male prépondérance of AIDS-KS is related to male homosexuality or to male gender [Grulich and Kaldor, 1997],
The reason for this striking gender différence remains unclear. The reported disappearance of KS lésions during or just after pregnancy [Hermans and Clumeck, 1995] has led to the considération that human chorionic gonadotropin (hCG) might display protective effects against KS [Hermans and Clumeck, 1995; Lunardi-Yskandar
et al, 1994], It has also been suggested that higher oestrogen levels are involved in the
female protection against KS [Klauke et al., 1995], However, hormones are not the only feature that distinguishes women ffom men, and environmental or genetic différences could also account for the unequal frequencies of KS in the two sexes. Although the probable sexual transmission of HHV-8 may provide some explanation for the increased incidence among AIDS-men with multipartner homosexual behavior, it is uniikely to account for the consistent of KS among its different epidemiological settings and caimot explain the male prédominance of KS in populations where HHV-8 prevalence is equally distributed among males and females.
II.2.5 Variation by race/ethnicity
III.l Descriptive histology of KS
The histopathology of fully developed nodules of KS in ail types of the disease is distinctive and rarely causes diagnostic problems; it is characterized by proliferating spindle-shaped cells (considered to be the tumor cells of KS), by angiogenesis, and by the presence of haemosiderin-laden macrophages and other inflammatory cells. The diagnostic pitfalls lie mainly in the early macular lésions which are easy to misinterpret as banal inflammation or some form of minor angiomatous or lymphatic anomaly. The histologie spectrum of KS has been divided into three stages (patch, plaque and nodular) which usually correlate with the clinical appearance and progression of the lésions [Tappero et ai, 1993; Calonje and Wilson-Jones, 1997; Chor and Santa Cruz, 1992], In reality, there is some overlap between stages, and multiple biopsies taken at the same time or even a single biopsy may show features of different histologie stages. There are no différences in the pathology of the disease among the different risk groups.
Patch stage (Fig. 2)
The earliest histologie changes of KS are inconspicuous. Usually there is a patchy, sparse, upper dermal perivascular infiltrate consisting of lymphocytes and plasma cells. In conjunction with the inflammatory infiltrate, subtle vascular changes can be detected. The earliest changes consist of the prolifération of miniature or irregular, blood vessels with ‘jagged’ outlines tending to separate collagen bundles [Ruszeak et ai, 1987]. Normal adnexal structures and preexisting blood vessels often protrude into newly formed vessels (promontory sign). At this stage, red blood cell extravasation and the presence of siderophages may be encountered.
Plaque stage
superficial subcutaneous tissue. The most characteristic feature of this stage is the addition of a significant spindle cell component which is dispersed between dermal collagen bundles and around pre-existing dermal vessels. Irregular, cleft-like spaces are formcd, creating new, angulatcd vascular channels which contain small numbers of érythrocytes. Hemosiderin deposits are typically présent. The histogenetic origin of the spindle cells remains controversial. A widely held view is that these cells dérivé ffom endothélial cells (EC), though they express macrophage antigens and fïbroblast markers [Kaaya et al, 1995].
Nodular stage
II1.2 Immunophénotype of KS
III.3 Proliférative activity of KS
The kinetics of tumor growth dépends on the number of cells actively engaged in the cell cycle (growth fraction), the duration of the cell cycle, and the rate of cell death and removal. Since the prolifération index of tumors may carry therapeutic implications, the question of the proliférative activity of KS goes beyond mere academie exercise.
Ki-67, a nuclear matrix cell protein which is expressed through ail phases of the cell cycle, but not in noncycling (Gq) cells [Cattoretti et ai, 1992], is predominantly
KS develops in four distinct populations as described previousiy (see § II).
Classic KS is predominantly a skin disease of the legs, although lymph node and
viscéral involvement may occur.
The disease is chronic and typically affects the lower legs, especially the ankles and soles. The initial lésions présent more often as macules or papules that may be pink, red, purple, violaceous or brown in color (Fig. I). The tumors are likely to progress to nodular or infiltrated forms. The lésions gradually coalesce, spread proximally and may in time ulcerate or become exophytic. S orne may invade underlying bone. Involvement of the lymphatics may cause lymphedema of the lower extremities and occasionally of the genitals. The edema is commonly ‘woody’ and may interfère with walking.
After the lower extremities, the upper limbs are most commonly affected. Lésions may aiso occur on the head and neck, upper trunk, or any skin surface.
There is about a 10% incidence of internai organ involvement, most commonly involving lymph nodes of the gastro-intestinal tract [Anthony and Koneman, I960]. Ail organs can be affected, but the brain is usually spared. Individuals with classic KS generally die of unrelated causes although patients may occasionally die ffom involvement of the gastrointestinal or pulmonary Systems.
African-endemic KS présents in one of the following clinically distinct patterns
[Taylor et a/., 1971]:
(1) benign nodular cutaneous disease closely mimicking classic KS; (2) aggressive localized cutaneous disease invading soft tissue and bone; (3) florid muco-cutaneous and viscéral disease;
fatal within 1 to 3 years, despite treatment with aggressive therapeutic regimens, including systemic chemotherapy or radiation or both, to which most other forms of KS usually respond [Friedmann-Kien and Saltzman, 1990].
Iatrogénie KS is primarily a cutaneous complication of immunosuppressive drug
therapy. Like classic KS, iatrogénie KS is often limited to the skin of the lower extremities but more diffuse cutaneous involvement (e.g., trunk and upper limbs) is not uncommon [Lesnoni La Parola et al, 1996], The most distinctive feature of posttransplant KS is its usual régression after réduction or withdrawal of immunosuppressive drugs.
AIDS-KS is characterized by a broad clinical spectrum of disease with
overlapping features encompassing ail varieties of non-AIDS KS [Friedman-Kien et
al, 1990, Tappero et al, 1993].
may be a rare cause of fever of unknown origin [Zalla 1996], In autopsy studies, death of most patients with AIDS-associated KS is attributed to opportunistic infections, and only 12% of the patients die of KS, either through massive gastrointestinal and respiratory hemorrhage or respiratory failure [Welch et al, 1984; Niedt and Schinella,
The pathogenesis of KS, regardless of its setting remains unclear. It is still unknown whether KS is a true malignancy or a reactive polyclonal process.
Many cells in the lésion are normal cells that hâve infiltrated the tumor, such as leukocytes. The prédominant cell in the tumor is a spindle-shaped cell, which is accompanied by abnormal blood vessel development and leakage of blood. It seems reasonable to call the spindle cell the ‘tumor celT, but there is no direct evidence that this cell is an autonomously growing neoplastic cell rather than a hyperproliferating but otherwise normal cell (hyperplasia) [Gallo 1998],
Although the question of the mono- or polyclonality of KS lésions remains controversial [Rabkin et ai, 1997, Gill et al, in press], several Unes of evidence suggest that KS is a polyclonal prolifération rather than a true malignancy;
- KS usually lacks anaplastic features.
- Early lésions hâve an inflammatory appearance and the variety of cell types involved suggests a polyclonal prolifération.
- KS has a tendency to preserve the architecture of the organs it involves. - KS shows multicentric origin and generally has an indolent course.
- Spontaneous remissions may sometimes take place [Real and Krown, 1985].
- Studies on classic, African-endemic and AIDS-related KS found low incidence or absence of DNA aneuploidy [Fukunaga and Silverberg, 1990; Eto et ai, 1992; Bisceglia et al, 1992], which does not fit one of the définitions of malignant neoplasms [Quirke 1990; Friedlander et al, 1984; Simonart et al, 1997], However, one study demonstrated that patients on steroid treatment had an aneuploid pattern on flow cytometry [Reizis et al, 1995].
V. 1 Spindle cells and their Products as the driving force of KS pathogenesis
Several features suggest that, at least in early stages, KS is a cytokine-mediated discasc promotcd by the coopération of inflammatoiy' cytokines and angiogenic factors [Barillari et al, 1992; Fiorelli et ai, 1995; Samaniego et al, 1998], The very early stage of KS is characterised by the presence of activated endothélial cells, angiogenesis and inflammatory cell infiltration [McNutt et al, 1983; Ruszcak et al, 1987, Schwartz 1985], This histologie pattern closely resembles granulation tissue whose pathogenesis is known to be mediated by cytokines and growth factors. In fact, elevated levels of tumor necrosis factor (TNF)-a, interleukin (IL)-ip, 11-6, oncostatin M, basic fibroblast growth factor (bFGF), vascular endothélial growth factor (VEGF) and interferon (IFN)-y hâve been detected in KS lésions [Oxholm et al, 1989; Li et al, 1993; Cai et
al, 1994; Ensoli et al, 1994; Siranni et al, 1998], In addition, high sérum levels of
inflammatory cytokines and growth factors, including TNF-a, IL-ip, IFN-y and nerve growth factor (NGF) are présent in HIV-mfected homosexual men before KS development [Samaniego et al, 1998; Pica et al, 1998; Gallo 1998], Similarly, high sérum levels of NGF are detected in HIV-negative patients with classic KS [Pica et al, 1998], The probable relationship between immune dysrégulation and KS is also supported by clinical findings showing that KS progresses more rapidly during acute infection [Mitsuyasu 1993] or after administration of inflammatory cytokines such as TNF-a or IFN-y [Aboulafia et al, 1989; BCriegel et al, 1989; Samaniego et al, 1998],
Benelli et ai, 1994; Pammer et ai, 1996], Thus, their immunophénotype appears more similar to that of myofibroblasts cells than to that of activated endothélial cells.
Initial studies identified supematants from activated T cells or from reùovirus- infected cell lincs as bcing important in the long-term maintenance of these cultures. These supematants contain the same inflammatory cytokines whose levels are found elevated in HIV-1 infected patients [Barillari et al., 1992; Fiorelli et al, 1995], The growth of KS cells in culture is markedly increased if cytokines and growth factors such as TNF-a, IL-ip, the soluble IL-6 receptor (sIL-6Ra)/IL-6 complex, oncostatin M, bFGF and NGF are added exogenously [Nakamura et al, 1988; Miles et ai, 1992; Murakami-Mori et al, 1998; Pica et al, 1998],
KS spindle cells also elaborate by their own a variety of angiogenic growth factors and cytokines, such as TNF-a, IL-ip, lL-6, oncostatin M, and bFGF (Ensoli 1989, Miles 1990, Nair 1992). Other angiogenic products released by KS cells are the 72-kDa and 92-kDa type IV collagenases/gelatinases [Blankaert et al, 1998], These enzymes digest denatured collagens (gelatins), intact type IV basement membrane collagen, native collagen type V, and are thought to play a critical rôle in the process of angiogenesis, tumor invasion and metastasis [Liotta et al, 1991; Sato et al, 1995; Karelina e/a/., 1995],
Recent studies hâve shown an in vivo overexpression of Bcl-2 among the spindle-shaped tumor cells of cutaneous KS lésions [Bohan Morris et al, 1996; Dada et
al, 1996], Another study has revealed weak Bcl-2 immunoreactivity but overexpression
of Bcl-xi, another protein tliat prevents apoptosis [Foreman et al, 1996],
V.2.2 Rôle of the p53 protein
lhas also been suggested that the p53 protein plays a rôle in the pathogenesis of KS. Indeed, mutations of the p53 gene hâve been detected in up to 29% of KS [Scinicariello et al, 1994], Now, classically, it has been shown that the loss of the p53 function, by allelic loss or by mutations of its corresponding gene, results in an increased cell prolifération or in a defective apoptosis in numerous human cancers [Hollstein e/a/., 1991],
However, p53 mutation or wild-type p53 accumulation appears as a late event in the pathogenesis of KS and could probably not explain the hyperplasie vascular prolifération of the early stage pSfoel et al, 1997; Noël and Simonart, 1998], These data are supported by the fact that the p53 overexpression is principally confined to spindle cells which are generally the histological major component of the late stages of KS [Bergman et al, 1996; Li et al, 1997], This indicates that p53 alterations, probably in association with alterations of other oncogenes such as K-ras or Bcl-2, might be involved in the progression of KS from a benign hyperplastic prolifération initiated by a viral infection such as HHV-8 to a lésion which could behave as a classical malignancy.
V.2.3 Rôle of the CD40 antigen
The CD40 antigen is a member of the tumor necrosis factor/nerve growth factor receptor superfamily and is involved in cell prolifération, différentiation, and survival. CD40 antigen is expressed by endothélial cells and tumor cells in KS lésions [Pammer
et al, 1995], As signaling through CD40 is able to increase cell survival, expression of
V.2 Escape from programitied cell death
Under normal physiological conditions as well as under many conditions of stress, cells die by a morphologically distinctive process known as apoptosis. This genetically programmed cell death sculpts many tissues during early development, maintaining organ homeostasis and ensuring the proper development and function of complex cellular Systems such as the immune System [Wyllie 1980], Interférence with the intrinsic capacity for cell suicide is central to the pathogenesis of many diseases [Thompson 1995], Enhanced cell survival can contribute to tumor development and autoimmune diseases, while enhanced apoptosis underlies many neurodegenerative diseases [Reed 1994], Consequently, there is great interest in the mechanisms that normally regulate cell death and their perturbations in neoplasia.
V.2.1 Rôle of the Bcl-2 protein
hybridization, which underlines the importance to perform high stringency PCR on KS samples [Simonart et ai, 1997], Even if the sensibility and specificity of the techmque could be improved, one fundamental question remains: does the irregular détection of some copies of vimses argue for their involvement in the pathogenesis of the KS lésion.
V.3.3 Direct and indirect rôle of HIV
Although not necessary for the development of KS, infection with HIV-1 is associated with at least a 20,000 fold increase in the incidence of KS [Beral et al, 1990], The strong association of KS with AIDS naturally led to early efforts to link HIV to KS etiology. Long-term growth of KS-derived cell cultures is accomplished with the use of conditioned media ffom retrovirally infected CD4 T-cell Unes (see V. 1), which suggests an indirect rôle for a retrovirus in the development of AIDS-KS.
There are multiple mechaitisms through which HIV may promote the development and/or progression of KS.
- HIV-1 infection may promote the réplication of other vimses by impairing the immunity of the host
- HIV-1 infection is characterized by aberrant cytokine production, including a marked increase of inflammatory cytokines, notably TNF-a, IL-ip, IL-6 and IFN-y [Nakamura
et ai, 1988, Ensoli et ai, 1989; Siraimi et al, 1998 Gallo 1998], Some of these
cytokines promote activation and growth of endothélial cells and the production and release of angiogenic molécules (bFGF and VEGF). Close examination of TNF-a and IL-ip levels shows that major increases in circulating levels are closely associated with the development of opportunistic infections. KS growth dramatically increases in times of opportunistic infections, and it is possible that the increase in rate of growth is related to increased expression of cytokines [Miles 1996].
V.3 Rôle of viral agents in KS
V.3.1 Epideitiiology suggestive of a sexually transmitted disease
Epidemiologie features strongly suggest that AIDS-assoeiated KS may be due to a sexually transmitted pathogen distinet from HIV (see II.2.3).
V.3.2 Détection of viral agents in KS
Several studies hâve investigated the possible relationship between viral transmissible agents and KS by testing for either sérologie evidence of viral infection in patients with KS or for the presence of viral DNA or RNA in KS tissues and KS- derived cell lines. Hepatitis B virus, human immunodeficiency virus (HIV), cytomégalovirus (CMV), human herpesvirus 6, human papilloma virus (HPV) and BK virus hâve been detected in KS tissues, and those varions viruses hâve been proposed as potential etiological agents for KS [Siddiqui, 1983; Andersen et al., 1991; Mahoney et al., 1991; Huang et al., 1992; Bovenzi et al., 1993; Adams et al., 1995; Monini et al., 1996a]. The détection of these agents in KS tissues, and hence their etiological rôle, is however highly equivocal: for example, the reported results regarding the rate of HPV infection in KS range from anecdotal case reports to 70% positivity [Noël et
al, 1997]. The reasons for these conflicting results are unclear; possible explanations
cross-is generally not expressed on cultured KS-derived ceils [Pammer et al, 1995; Simonart
étal, 1996],
V.2.4 Résistance to Fas-mediated apoptosis
The escape of KS cells firom programmed cell death is also supported by a study showing that AIDS-KS-derived cells resist to Fas-mediated apoptosis [Mon et al,
lésions when both are injected subcutaneously in nude mice [Ensoli et ai, 1994; Albini
et al, 1995], Tat can also transactivate some other viral promoters [Kim and Risser,
1993] and some cellular genes such as TNF-P, lL-6 and TGF-P [Buonaguro et al, 1992; Buonaguro et al, 1994; Cupp et al, 1993], Tat may also induce inflammatory response genes in KS cells., which could promote further leukocytes infiltration [Kelly
et al, 1998], These infiltrated leukocytes could provide additional Tat, HHV-8 (see §
V.3.4) and cytokines to KS cells.
Several épidémiologie data still suggest that HIV is unlikely to be the sole factor in KS development. Transplant récipients as well as patients with classic or endemic KS hâve no evidence of exposure to HIV. There are also homosexual men who are not infected with HIV and who get KS [Friedmann-Kien et al, 1990]. Thus, although HIV markedly increases the incidence of KS (by a factor of 20,000 to 50,000) [Haverkos et
al, 1990; Gallo 1998], it appears to play an auxiliary rôle in the development of the
tumor. In addition, KS is not uniformly distributed among AIDS patients: the disease is 7- to 15-fold more common in HIV-positive gay men than in other groups who acquire HIV by non-sexual routes (e.g., hemophiliacs). Thus, another agent or co-factor, Irkely sexually transmitted, is involved in KS etiology.
V.3.4 Rôle of human herpesvirus 8 (HHV-8)
Motivated by these considérations, Chang et al searched for DNA sequences that were présent in KS lésions and absent in uninvolved tissues. In 1994, they detected a new human herpesvirus type, known as KS-associated herpesvirus or human herpesvirus 8 (HHV-8) [Chang et al, 1994]. The sequence reveals HHV-8 to be a member of the herpes family’s lymphotropic subgroup, whose best-known member is Epstein-Barr virus (EBV) (table 2). This discovery changed the face of KS research and ignited a passionate debate about the rôle of this agent in the etiology of the tumor.
The détection of this gamma-2 herpesvirus in ail the epidemiological and histological forms of KS makes it an attractive candidate causative agent [Chang et ai,
1994; Noël et ai, 1996]. Sequence analysis of the PCR products from the different forms of KS reveals only few nucleic acid variations, suggesting that the virus is highly conserved. Therefore the different forms of KS are probably not caused by sequence variations of HHV-8 [Moore et al, 1995; Kemény et ai, 1996], Unlike HIV, HHV-8 can directly infect the KS spindle cells: in situ hybridization studies show viral DNA and transcripts in the vast majority of spindle cells in KS lésions [Boschoff et ai, 1995; Staskus et ai, 1997], The fiat endothélial cells lining the vascular spaces of KS lésions may be other targets for HHV-8 infection [Boschoff et ai, 1995],
HHV-8 is présent not only in cutaneous KS but also in a wide range of other cells and tissues in patients with KS. The virus exerts tropism for CD 19+ circulating B lymphocytes and is présent (in low copy numbers) in peripheral blood mononuclear cells [Ambroziak et ai, 1995; Whitby et ai, 1995]. The presence of HHV-8 in these cells may even predict the subséquent development of KS in HIV-infected patients [Whitby et ai, 1995]. Howard et al. demonstrated HHV-8 DNA in bronchoalveolar lavage fluid firom patients with HIV (with and without pulmonary KS) and suggested that these results correlated with the clinical diagnosis of pulmonary KS [1995]. The sensory ganglia and saliva of patients with KS are other sites of infection [Corbellino
et ai, 1996; LaDucaeta/., 1998].
Détection of HHV-8 in the uro-genital tract and in séminal sécrétions.
Diamond et ai, 1998], which raises crucial questions regarding the sexual transmission of HHV-8. An about 20% détection rate bas been reported in semen of HIV-infected gay men [Viviano et al, 1997; Howard et al, 1997], Intennittent réplication of HHV-8 in the prostate and subséquent shedding of the virus in semen may be reasons why détection of the virus in semen is inconsistent. Fluctuations in virus réplication may also be affected by host immunity, as is the case with other herpesviruses. Another caveat to these studies is that men provided samples by masturbation, and semen specimens obtained by masturbation might contain fewer prostatic sécrétions than semen obtained through sexual intercourse [Diamond et al, 1998], Similarly, intermittent viral shedding may explain the low détection rate (27%) of HHV-8 DNA in cervical brush srapes from HHV-8 sero-positive women [Whitby et al, 1999],
Studies conceming the prevalence of HHV-8 in the génital tract and semen from the general population hâve given diverse and conflicting data [Blackboum et al,
1997], Italian investigators hâve detected HHV-8 m a large proportion of ejaculates (30 of 33; 91%) and prostate specimens (7 of 16%; 44%) from men at low risk for HIV infection [Monini et al, 1996], Similar results were foimd by Staskus et al. [1997] who detected HHV-8 RNA by in situ hybridization in prostatic autopsy tissue from 9 of 11 adult HIV-negative men, suggesting widespread infection with the virus in the male urogénital tract. In contrast, other authors did not detect or detect low rates of HHV-8 in semen, prostate specimens or in cervical brush scrapes from HIV-seronegative patients without KS [Lebbé et al., 1997; Howard et al, 1997; Diamond et al, 1998; Whitby et al, 1999], Some of the widespread disparity in prevalence rates may be related to laboratory techniques as well as to différences in the geographical distribution of HHV-8 seropositivity.
Détection of HHV-8 in lymphoproliférative lésions
Because of an increased risk of lymphoid cancer in patients with KS [Martin et
al, 1993; Biggar et al, 1994], different lymphoma were also investigated for the
patients with a rare form of diffuse B-cell lymphoma called body cavity-based lymphoma (BCBL) [Cesarman et al, 1995], recently renamed primary effusion lymphoma [Ceserman et ai, 1996], These tumors represent a distinct subgioup of l>Tnphomas that lack the c-myc gene rearrangement but often (although not always) contain EBV as well as HHV-8 [Knowles et al, 1989; Walts et al, 1990], Ail eight investigated BCBL contained HHV-8, whereas 185 other lymphomas lacked HHV-8 DNA [Ceserman et al, 1995], A high degree of conservation of HHV-8 sequences in KS and BCBL tumors suggests the presence of the same agent in both lésions.
Another lymphoproliférative disease in which HHV-8 was detected is multicentric Castleman’s disease, also called multicentric angiofollicular lymphoid hyperplasia [Soulier et al, 1995], This usually benign polyclonal lymphoid prolifération with vascular hyperplasia has also been reported to be associated with KS [Chen 1984],
Détection of HHV-8 in vascular tumors other than KS
The association of KS with HHV-8 raised the question of whether the virus can also be associated with other endothélial cell-derived vascular neoplasms. HHV-8 DNA was detected in angiolymphoid hyperplasia with eosinophilia (ALHE) (Gyulai
endothélial cells suggests that the virus alone is not sufficient to produce a spécifie lésion.
Sero-epidemiology of HHV-8
This putative rôle is supported by seroepidemiologic studies indicating that infection with HHV-8 tracks strikingly with the risk for KS development [Melbye et
al., 1998, Renwick et al., 1998], A variety of sérologie tests for HHV-8 infection has
been developed [Ganem 1996], Most involve détection of a latency-associated antigen (LANA) présent in infected B cell cultures; other tests hâve examined reactivity to lytic-cycle antigens. The tests for anti-LANA are highly spécifie but only about 80% are sensitive enough to detect infection in KS patients. Prevalence figures based on this test must be considered minimal estimâtes. By several criteria, HHV-8 apppears to be the agent predicted by the epidemiology of KS: infection précédés development of the tumor, tracks tightly with KS risk, and specifically targets the cell thought to be at the heart of the lésion. Further evidence in favor of this could corne either from the transmission of both infection and disease to a suitable animal or from the démonstration that a spécifie intervention (e.g., vaccination), that blocks infection, reduces the incidence of the disease in man, but neither resuit is just around the corner.
Characterization of HHV-8
At the beginning of the HHV-8 studies, a fmding that confrised investigators and hampered fiirther progress was that KS cell cultures lacked the viral DNA sequences [Lebbé et ai, 1995; Ambroziak et al., 1995; Simonart et al., 1996; Gallo
of apoptosis (i.e., Bcl-2) [Cheng et ai, 1997; Sarid et al, 1998] or in the control of cellular prolifération and/or différentiation (i.e., cyclin D, G protein-coupled receptors) [Ceserman et ai, 1996]. Additionally, HHV-8 encodes homologs of host genes known to function in cytokine signaling (CC chemokines, CXC chemokine receptors, interferon-regulatory factor 1, lL-6) [Neipel et ai, 1997].
Rôle of HHV-8 still unclear
The existence of virally encoded cytokines and cytokine receptors in a tumor in which paracrine signaling has long been suspected is particularly provocative. But we are still in the dark as to whether and how such genes might function during pathogenesis; in other words, the transforming potential of the virus is not clear-cut. For example, ORF 74, a HHV-8 homolog of a G protein-coupled receptor, is expressed in some KS tissues and induces expression of the angiogenic cytokine VEGF and cell growth [Guo et ai, 1997; Arvanitakis et a/., 1997]; although these fmdings are of interest, they cannot be taken as evidence that HHV-8 is oncogenic or is responsible for angiogenesis in KS lésions [Gallo 1998]. Expression of ORF 74 is generally restricted to lytic phase réplication so that the cells in which it is expressed are probably destined to die, not to grow. This model is opposite to what we know about other oncogenic herpesviruses, for which it is latency-associated genes that are primarily responsible for tumorigenesis. Furthermore, in some lésions, expression is not detected at ail by reverse transcription polymerase chain reaction [Guo et al,
1997]. Expression of VEGF in a tumor composed of many newly fomting blood vessels is notable, but because ORF 74 is not expressed in some KS tumors whereas VEGF is regularly found, the origin of VEGF expression must be more complex than simple induction by ORF 74. Indeed, VEGF (and bFGF) production is also stimulated by inflammatory cytokines induced by HlV-1 infection [Masood et al, 1997].
Recently, the first evidence was presented for in vitro growth promotion of endothélial cells by HHV-8 with implications for neoplastic transformation [Flore et
high concentrations of VEGF, but they were continuously dépendent on VEGF, exhibited unusual requirements for growth on soft agar (supplemented with 40% fêtai calf sérum and high concentrations of endothélial growth supplément), and did not show tumorigenicity in an animal model, leaving serions doubts as to whether these effects can be called transformation, or even immortalization [Gallo 1998], Nonetheless, this study clearly shows a direct growth-promoting effect of HHV-8 on the main proliferating cells of KS, the endothélial cells.
Several additional data make the rôle of HHV-8 in KS unclear.
First, HHV-8 DNA sequences cannot be detected neither in KS-derived cell cultures nor in KS cell Unes [Lebbé et ai, 1995; Ambroziak et al., 1995; Simonart et
ai, 1996; Gallo 1998], This may suggest that the putative HHV-8 ‘transformed’ cells
immediately die in culture and that the studied cultured spindle-like cells are not the récipient cells of the virus. One can also wonder whether these conflicting results between the in vivo lésions and their derived cell culture are due to différences in the enviromnent of the cells studied. HIV-infected homosexuals are known to hâve increased levels of inflammatory cytokines which may play a critical rôle in the progression of KS. Since the same cytokines can upregulate virus expression, it is possible that they are involved in both KS induction and HHV-8 maintenance.
Secondly HHV-8 DNA has been found in normal tissues and in a variety of proliférative conditions other than KS, in both immunocompromised and immunocompétent patients [Gyulai et al, 1996; Gyulai et ai, 1996; Bigoni et al, 1996; Viviano et al, 1997]. In addition, HHV-8 has ben identified in pemphigus lésions, in sarcoid tissues, in bone marrow dendritic cells of patients with multiple myeloma, and in a variety of lymphoid disorders [Drago and Rebora, 1999]. The latter include multicentric Castleman disease and primary effusion lymphomas.
In conclusion, there is still no ultimate évidence for a direct causal rôle of a defined viral agent in KS. The possible rôle of multiple viral infections as cofactors and transactivators in KS, as suggested for HHV-6 and other herpesviruses [Henghold
et al., 1997], should not be dismissed. It remains likely that viral infection per se is not
cases per 100,000 men, the HHV-8 rate would be one case of KS in every 17,000 HHV-8 infections (Gallo 1998). In addition, seroprevalence in different géographie areas do not correlate with KS development. Eighty-four percent to 100% of sérum samples fiom the general population in non-KS-endemic African areas proved to bc positive; such a rate is higher than the one of endemic régions, and is the same among patients with KS [Gompels and Kasolo, 1996].
Fourthly, if HHV-8 were directly involved in the pathogenesis of KS, it would potentially represent an attractive therapeutic or préventive target. Current data addressing this point are not conclusive. Rétrospective analyses of KS incidence among HIV-infected patients, together with anecdotal reports of remission of KS, suggest that foscamet may he of value in preventing or treating KS [Jones et al., 1995; Mocroft et al., 1996; Morfeldt and Torssander, 1994]. At the same time, many other patients with KS hâve received foscamet or other anti-herpesvims dmgs without apparent resolution of their KS [Costagliola and Mary-Krause, 1995]. In addition, the use of intravenous foscamet or ganciclovir does not appear to affect the HHV-8 DNA load [Boivin et al, 1999]. Recent studies hâve demonstrated that several acyclic nucleoside phosphonate (ANP) analogs hâve a potent in vitro activity against HHV-8, suppressing its lytic DNA synthesis in BCBL-1 cell Unes [Kedes and Ganem, 1997; Medveczky et al., 1997; Neyts and De Clercq, in press]. The in vivo activity of ANP analogs on KS remains conflicting. Therapy with cidofovir (Vistide*^), a nucléotide analog with antiangiogenic activity [Liekens et al., submitted for publication] and with a hroad spectrum antiviral activity against DNA vimses (herpesviridae, adenoviridae, poxviridae, hepadnaviridae and papovaviridae) [Hitchock et ai, 1996, Snoeck et ai,
Table 2. Members of the family Herpesviridae Alphaherpesviruses
Herpes simplex virus 1 (HSV-1) Herpes simplex virus 2 (HSV-2) Equine herpesvirus 1 (EHV-1) Varicella-zoster virus (VZV) Pseudorabies virus (PRV) Betaherpesviruses Human cytomégalovirus (HCMV) Human herpesvirus 6 (HHV-6) Human herpesvirus 7 (HHV-7)
Gammaherpesviruses (lymphotropic subgroup) Herpesvirus saimiri (HVS)
Epstein-Barr virus (EBV) Equine herpesvirus 2 (EHV-2)
The therapeutic strategies of KS remain under debate and dépend in part on the subtype of KS.
Iatrogénie immunosuppression-related KS usually résolves without spécifie treatment by decrcasing the dose or discontinuating immunosuppressive médication, when possible.
Vl.l Local treatment
Patients with cosmetically bothersome lésions and those with limited numbers of symptomatic lésions are candidate for local therapy.
Cryotherapy yields complété or partial remission in up to 85% of patients,
lasting as long as 6 months, presumably due to superficial scarring that masks residual dermal disease [Tappero et al, 1991], Cryotherapy is most effective for papules and macules less than 1 cm in diameter.
Surgical excision of small symptomatic lésions has been effective [Webster,
1995], as has argon and pulsed dye laser photocoagulation, although récurrence is common within 3 months after the latter [Wheeland et al, 1985; Tappero et al, 1992], These modalities are occasionally limited by the Koebner phenomenon displayed by KS. Oral lésions hâve been succesflilly treated with the C02 laser [Marcusen and Sooy, 1985], although caution is required since HIV DNA has been detected in the C02 (and argon) laser smoke [Baggish et al, 1991],
Intralesional Vinblastine or vincristine provides complété or partial response in
60-88% of the lésions, though récurrences may be noted within 4-6 months in 40% of patients [Odom and Goette, 1978; Brambilla et al, 1984; Webster, 1995; Boudreaux et
al, 1993], As with cryotherapy, residual KS is found histologically despite
acceptablecosmetic results. Advantages of intralesional chemotherapy over cryotherapy include a higher response rate for papulonodular lésions greater than 1 cm in diameter and the ability to treat symptomatic oral lésions to reduce pain associated with mastication and prevent pain and bleeding [Epstein et al, 1991], Diadvantages for the patient include frequent lesional postinflammatory pigmentation [Boudreaux et al, 1993], Pain lasting for 1 to 2 days after injection is the most common side effect. Patients should be informed about infrequent complications, including intense edema, blistering and ulcération, and alopecia for lésions injected at hear-bearing sites [Tappero et al, 1993], Finally, injections at sites adjacent to large peripheral nerves shoud be avoided because transient mononeuropathy has been reported [Tappero et al,
Intralesional interferon alfa has also been used with success in AIDS-KS and
classic KS [Myskowsky, 1992; Trattner et al, 1993; Dupuy et al, 1993], Interferon is significantly more expensive than Vinblastine and requires more frequent treatments, limiting its useflilness somewhat.
Radiation therapy has been a mainstay in the local treatment of classic, endemic
African and AIDS-KS. Response rates of 80-100% hâve been reported, employing varions types of radiation applied in differing dosages and firactionation regimens [Tappero et al, 1993], Radiation therapy appears best suited for symptoms caused by mass effects (e.g., large intraoral lésions, localized painful lymphadenopathy, and localized lymphedema of the extremities and pénis) because lésions irradiated solely for cosmetic purposes hâve less than a 50% reuction in size in most patients [Chak et
VI.2 Systemic treatment
Patients who are not easily managed with local therapeutic strategies frequently respond to systemic therapy, despite the increased risk of significant side effects. The systemic treatment modalities of KS include chemotherapy, interferon, and a variety of non-cytotoxic médications.
VI.2.1 Chemotherapy
Debilitating cutaneous or viscéral lésions are currrently treated with systematically administered cytotoxic drugs. They are given either alone or in combination, although no clear benefit on survival has been demonstrated with either regimen [Lilenbaum and Ratner, 1994], Most usual anti-KS chemotherapie agents are bleomycin, vinca alcaloids and adriamycin. Single-agent chemotherapy with liposomal formulations of anthracyclines (doxorubicin and daunorubicin) has received significant attention [Harrison et ai, 1994], based upon theoretic sélective uptake of these agents by tumor tissue. For patients who cannot tolerate anthracyclines, such as those with liver disease or cardiac dysfunction, bleomycin and vincristine may be a resonable alternative [Lee and Mitsuyasu, 1996],
Single-agent therapy with Taxol® (paclitaxel) can be administered as a rescue therapy for patients who failed to respond to other regimens or as a first line agent in countries where it is available [Saville et ai, 1995],
VI.2.2 Interferon
survival or whether responding patients simply hâve better overall disease status [Zalla, 1996], Features associted to a poor response t interferon include low CD4+ counts (less than 200/mm^), prior opprtunistic infection, and ‘B’ symptoms (weight loss, fever, night sweats) [Pluda et ai, 1995; Zalla 1996],
Interferon-alppha commonly cuses a flu-like syndrome of anorexia, high fevers, chills, malaise, and myalgias. The side effects are usually réversible upon discontinuation of the drug and may be minimized by initiation of therapy at low dose followed by graduai escalation, with concomitant acetaminophen [Pluda et ai, 1995; Zalla 1996], Interferon-alpha may also cause distal paresthesias, decreased concentration, and dépréssion. Neutropenia is common and hepatic enzyme élévations and thrombocytopenia hâve also been noted [Pluda et ai, 1995; Zalla 1996],
VI.2.3 Antivirai strategies
Both HIV-1 and HHV-8 are potential targets for anti-KS therapy. Although HIV-1 infection is not a requirement for development or progression of KS, active infection with HIV-1 is associated with high levels of inflammatory cytokines implicated in the develoment of KS lésions. In addition, the HIV-1 Tat protein, which is released into the extracellular milieu by infected cells, also serves as a mitogen for KS-derived spindle cells in vitro and acts synergistically with growth factors and inflammatory cytokines to increase KS cell prolifération (see § V.3.3).
Wansbrough-Jones, 1997] and neither clinical nor virological effect of indinavir therapy was shown in a patient with multicentric Castleman’s disease [Dupin et al,
1997], The précisé mode of action of HAART remains so far undetermined. The absence of clear association bcts\cen HAART and HHV-8 load suggests that antiviral therapy does not act through HHV-8 spécifie effects [De Milito et ai, 1999], Since KS probably results ffom a complex interaction of viral and immunological factors, the favorable effects of HAART on AIDS-related KS may be explained by factors other than HHV-8 load, including restoration of the immune System and decrease in HIV-1 réplication. For example, HAART might lead to decreased expression of Tat protein, whose angiogenic properties are well established, or might interfère with the interaction between HHV-8 and HIV [Harrington et ai, 1997],
Anecdotal reports that established KS regressed after treatment with foscamet [Morfeldt and Torssander, 1994] and studies that showed a decreased incidence of subséquent KS in patients treated with foscamet [Jones et al, 1995; Mocroft et al, 1996; Robles et al, 1999] suggest that, under some circumstances, inhibition of HHV-8 may also be of therapeutic or prophylactic value. However, this dmg is not spécifie for HHV-8 (the treatments were directed against cytomegalovims and the studies were not designed to evaluate effects on HHV-8), so that the mechanism of KS inhibition in these cases is entirely spéculative.
VI.2.4 Human chorionic gonadotrophin (hCG) préparations
1999], Several clinical trials hâve been set up to establish the activity of these préparations in patients with KS. So far, the results of the different studies conducted in US and in Europe hâve appeared conflicting, showing remission, absence of effect or even progression of KS lésions under hCG therapy [Gill et al, 1996; Tirelli et al, 1997, Hermans e/a/., 1998],
VI.2.5 Cytokine inhibition strategies
A number of proinflammatory cytokines, whose production is increased in patients with HIV infection, hâve also been considered as targets for KS therapy. TNF and IL-1 hâve each been shown to stimulate KS cell prolifération in vitro, either directly or through the induction of IL-6 (see), and varions agents that modify their production or action hâve either been tested in clinical trials or proposed as candidate therapeutic agents. Of particular note are the retinoids, which are multifunctional agents among whose many attributes are down-regulation of both lL-6 receptors and lL-6 production [Sidell étal, 1991], Thalidomide is another inhibitor of TNF production [Moreira et al, 1993], Preliminar clinical data suggest that both retinoic acid and thalidomide may hâve substantial anti-KS activity [Krown, 1998],
Vl.2.6 Angiogenesis inhibitory strategies
A large number of strategies aimed at the inhibition of angiogenesis hâve been proposed. Some of these approaches hâve not yet been tested clinically, but candidate agents are already in development. These include, for example, inhibitors of matrix metalloproteinases (which are enzymes that facilitate capillary budding and invasion [Blankaert et al, 1998] and agents targeted at distinctive endothélial cell surface molécules présent on proliferating tumor-associated vasculature [Krown, 1998].
KS is an angioproliferative disease that has aroused considérable interest of late, as it is one of the major clinical manifestations foimd in patients with AIDS. Until the AIDS épidémie, this tumor was identified in three different settings: classic KS, Aliican-endemic KS and immunosuppressive drug-rclatcd KS.
The hypothesis that KS is a sexually transmitted disease has received considérable attention. Several lines of evidence suggest that a new herpesvirus designated human herpesvirus 8 (HHV-8) or KS-associated herpesvirus is involved in the pathogenesis of KS. Its précisé rôle still remains unclear. More particularly, co factors may be required for the development of the disease.
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MAIN OBSERVATIONS
Simonart Th, Van Vooren JP, Noël JC, Liesnard C, Farber CM, Parent D. High prevalence of cutaneous infections in AIDS patients with Kaposi's sarcoma; insight into the rôle of human herpesvirus 8? AIDS 1997; 11 ; 824-6.
Background and objective: As KS is considered to be a sexually transmitted disease, this study was undertaken to détermine whether AIDS patients with KS were more likely to hâve cutaneous viral infections and other infections markers of multi- partner sexual activities than those without KS.
Design and Methods: The study involved 153 patients who were followed from December 1987 to May 1996, and for whom medical records were available from the documentation of AIDS to their death. Since 1987, ail cutaneous fmdings hâve been systematically registered by dermatologists in those patients. Clinical records were retrospectively reviewed and patients with KS were compared to patients without KS for the prevalence of a variety of HIV-related diseases.
Comparison of data was made using odds ratios (OR), corresponding 95% confidence intervals and contingency table analysis based on chi-square suimnary statistics.
