Article
Reference
PTEN in liver diseases and cancer
PEYROU, Marion, BOURGOIN, Lucie, FOTI, Michelangelo
Abstract
The phosphoinositide 3-kinase (PI3K)/phosphatase and tensin homolog (PTEN)/Akt axis is a key signal transduction node that regulates crucial cellular functions, including insulin and other growth factors signaling, lipid and glucose metabolism, as well as cell survival and apoptosis. In this pathway, PTEN acts as a phosphoinositide phosphatase, which terminates PI3K-propagated signaling by dephosphorylating PtdIns(3,4)P(2) and PtdIns(3,4,5)P(3).
However, the role of PTEN does not appear to be restricted only to PI3K signaling antagonism, and new functions have been recently discovered for this protein. In addition to the well-established role of PTEN as a tumor suppressor, increasing evidence now suggests that a dysregulated PTEN expression and/or activity is also linked to the development of several hepatic pathologies. Dysregulated PTEN expression/activity is observed with obesity, insulin resistance, diabetes, hepatitis B virus/hepatitis C virus infections, and abusive alcohol consumption, whereas mutations/deletions have also been associated with the occurrence of hepatocellular carcinoma. Thus, it appears that [...]
PEYROU, Marion, BOURGOIN, Lucie, FOTI, Michelangelo. PTEN in liver diseases and cancer.
World Journal of Gastroenterology , 2010, vol. 16, no. 37, p. 4627-33
PMID : 20872961
Available at:
http://archive-ouverte.unige.ch/unige:33147
Disclaimer: layout of this document may differ from the published version.
PTEN in liver diseases and cancer
Marion Peyrou, Lucie Bourgoin, Michelangelo Foti Marion Peyrou, Lucie Bourgoin, Michelangelo Foti, Depart- ment of Cellular Physiology and Metabolism, Geneva Medical Faculty, Centre Médical Universitaire, 1211 Geneva 4, Switzerland Author contributions: All authors contributed equally to the preparation, writing, and editing of this article; all authors read and approved the final manuscript.
Supported by The Swiss National Science Foundation (Grant 310000-120280/1), the Foundation for Cancer Research in Swit- zerland (Grant KFS - 02502-08-2009), the Eagle Foundation and the Gertrude von Meissner Foundation (to Foti M)
Correspondence to: Michelangelo Foti, PhD, Department of Cellular Physiology and Metabolism, Geneva Medical Faculty, Centre Médical Universitaire, 1, rue Michel-Servet, 1211 Geneva 4, Switzerland. michelangelo.foti@unige.ch
Telephone: +41-22-3795204 Fax: +41-22-3795260 Received: May 6, 2010 Revised: June 21, 2010 Accepted: June 28, 2010
Published online: October 7, 2010
Abstract
The phosphoinositide 3-kinase (PI3K)/phosphatase and TENsin homolog deleted on chromosome 10 (PTEN)/Akt axis is a key signal transduction node that regulates cru- cial cellular functions, including insulin and other growth factors signaling, lipid and glucose metabolism, as well as cell survival and apoptosis. In this pathway, PTEN acts as a phosphoinositide phosphatase, which terminates PI3K- propagated signaling by dephosphorylating PtdIns(3,4)P2 and PtdIns(3,4,5)P3. However, the role of PTEN does not appear to be restricted only to PI3K signaling antago- nism, and new functions have been recently discovered for this protein. In addition to the well-established role of PTEN as a tumor suppressor, increasing evidence now suggests that a dysregulated PTEN expression and/or activity is also linked to the development of several he- patic pathologies. Dysregulated PTEN expression/activ- ity is observed with obesity, insulin resistance, diabetes, hepatitis B virus/hepatitis C virus infections, and abusive alcohol consumption, whereas mutations/deletions have also been associated with the occurrence of hepatocel- lular carcinoma. Thus, it appears that alterations of PTEN expression and activity in hepatocytes are common and
recurrent molecular events associated with liver disorders of various etiologies. These recent findings suggest that PTEN might represent a potential common therapeutic target for a number of liver pathologies.
© 2010 Baishideng. All rights reserved.
Key words: Phosphatase and TENsin homolog deleted on chromosome 10; Obesity; Insulin resistance; Non-alcohol- ic fatty liver diseases; Steatosis; Steatohepatitis; Fibrosis;
Hepatocellular carcinoma; Viral hepatitis; Alcohol
Peer reviewers: Thomas Kietzmann, Professor, Department of Biochemistry, University of Oulu, Oulu 90014, Finland; Dr.
Juan Carlos Laguna Egea, Catedràtic de Farmacologia/Pharma- cology Professor, Unitat de Farmacologia/Pharmacology labo- ratory, Facultat de Farmàcia/School of Pharmacy, Universitat de Barcelona/University of Barcelona, Avda Diagonal 643, Barce- lona 08028, Spain; Dr. Joao Batista Teixeira Rocha, Department of Toxicological Biochemistry, Universidade Federal De Santa Maria, Santa Maria 97105-900, Brazil
Peyrou M, Bourgoin L, Foti M. PTEN in liver diseases and can- cer. World J Gastroenterol 2010; 16(37): 4627-4633 Available from: URL: http://www.wjgnet.com/1007-9327/full/v16/i37/
4627.htm DOI: http://dx.doi.org/10.3748/wjg.v16.i37.4627
INTRODUCTION
Obesity, metabolic syndrome, hepatitis virus infections, and abusive alcohol consumption are major etiological factors contributing together, or independently, to the development of severe liver diseases[1-3]. Interestingly, the hepatic pathologies induced by these various factors are associated with common metabolic disorders, i.e. insulin resistance and dysregulated lipid metabolism, and en- compass similar histological abnormalities, ranging from hepatic steatosis to steatohepatitis, fibrosis, and cirrhosis[4]. Hepatocellular adenoma (HCA) or hepatocellular carcino- ma (HCC) might then occur as a likely end stage of these diseases[5].
EDITORIAL
© 2010 Baishideng. All rights reserved.
doi:10.3748/wjg.v16.i37.4627
Peyrou M et al. PTEN in liver diseases and cancer Deregulations of numerous signaling pathways leading to insulin resistance, steatosis, inflammation, fibrosis, ab- errant cell proliferation, and resistance to cell death have been reported. Among these, abnormal signaling through the phosphoinositide 3-kinase (PI3K)/phosphatase and TENsin homolog deleted on chromosome 10 (PTEN)/
Akt pathway critically contributes to the development of non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), alcoholic liver disease (ALD), viral hepatitis [hepatitis B virus (HBV) and hepatitis C virus (HCV)], and HCC[6-10]. Of particular interest in this signaling pathway is the role of PTEN, an important tu- mor suppressor having a protein and phosphoinositide phosphatase activity. Indeed, PTEN switches off signal- ing through the PI3K-Akt axis and by doing that, controls growth factor signaling, thereby acting as a potent tumor suppressor. In the context of hepatic metabolic disorders and cancer, increasing evidence now supports a crucial role of PTEN in the development of these diseases.
PTEN
The PTEN protein was first identified as a potent tumor suppressor that was frequently mutated or deleted in sever- al human cancers, including HCC[11-16]. The best-character- ized function of PTEN is its phosphoinositide phospha- tase activity, where it dephosphorylates the PtdIns(3,4)P2
and PtdIns(3,4,5)P3 second messengers on the 3’-position of the inositol ring. PTEN thus antagonizes PI3K activa- tion and acts as a potent regulator of growth factor signal- ing, in particular insulin/insulin-like growth factor (IGF)-1 signaling, in peripheral tissues such as the liver[8,17]. In vitro studies also suggested that PTEN might have a protein phosphatase activity; however additional studies are re- quired to confirm this enzymatic activity[18-20].
Compared to other classical tumor suppressor, PTEN represents a particular case, as loss of heterozygocity, or partial inhibition of its expression/activity, is sufficient to promote carcinogenesis, in addition to affecting critical cellular functions, such as glucose and lipid metabolism.
Consistent with these observations, PTEN expression and activity appears to be regulated by numerous and complex mechanisms. Among these mechanisms, epigenetic silenc- ing by hypermethylation of its promoter[11,21] or histone deacetylase activity[22] strongly affect PTEN expression.
Several transcription factors, including Egr1[23], p53[24], peroxisome proliferator-activated receptor γ[25], Spry2[26], Atf2[27], and Myc[28], have been shown to directly bind the PTEN promoter and to upregulate PTEN transcription.
On the other hand, transcription factors such as nuclear factor (NF)-κB[29,30], p300/CBP[29], Hes-1[28], Cbf-1[31,32], and c-Jun[33] have been shown to negatively regulate PTEN transcription. Adding to the complexity of PTEN expression regulation, recent evidence also indicated that the PTEN mRNA undergoes post-transcriptional repres- sion/degradation by specific microRNAs (miRNAs).
Several miRNAs, including miR-21, miR-19a, miR-17-92, miR-214, miR-216a, and miR-217, have been shown to
specifically modulate PTEN mRNA expression[34-39]. Fi- nally, additional processes, whereby the PTEN protein level and activity are modulated, occur post-translationally.
These include modifications of the protein, such as phos- phorylation, acetylation, ubiquitination, and the REDOX state, which affect PTEN stability, degradation and en- zymatic activity[21,40,41]. Similarly, PTEN sequestration in specific subcellular compartments or membranes through interactions with distinct proteins, i.e. FAK[42], MAGI proteins[43], MAST proteins[44], p53[45], NHERF1/2[46], and PICT1[47] likely represent additional mechanisms control- ling PTEN stability and/or activity.
PTEN IN HEPATIC INSULIN RESISTANCE
Functional defects of key intracellular signaling pro- teins, in particular in the mammalian target of rapamycin (mTOR)/PI3K/PTEN/Akt pathways, are clearly as- sociated with insulin unresponsiveness of peripheral tis-
sues[48,49]. Indeed, the imbalance between propagation and
termination of signaling through mTOR/PI3K/PTEN/
Akt represents basal molecular dysfunctions triggering the development of insulin resistance and type II diabetes.
Given the enzymatic activity of PTEN, dysregulation of its activity/expression are potentially important mecha- nisms contributing to insulin resistance in tissues such as the liver[8].
Several in vivo studies, where PTEN expression was genetically altered in various organs of mice, support a crucial role for PTEN expression/activity in insulin sensi- tivity. PTEN haploinsuficiency and PTEN muscle-specific deletion were shown to improve skeletal muscle insulin sensitivity and to protect mice from insulin resistance and diabetes caused by high fat feeding, respectively[50,51]. Dele- tion of PTEN in the adipose tissue prevented the devel- opment of streptozotocin-induced diabetes[52]. Treatment of db/db mice with PTEN antisense oligonucleotides nor- malized plasma glucose levels in these animals[53].
Interestingly, liver-specific PTEN knockout mice also have an improved systemic insulin sensitivity and glucose tolerance[54,55]. However, whether this is related to increased insulin sensitivity specifically in the liver, or to a complex in vivo systemic crosstalk between a PTEN-deficient liver and other peripheral tissues, remains unclear. In support of this latter hypothesis, PTEN deletion in the liver is ac- companied by decreased circulating levels of leptin and body fat content[55]. In addition, we observed that although constitutive Akt activity is increased in cultured hepatoma cells having downregulated PTEN, insulin signaling up- stream of Akt, i.e. insulin receptor/IRS1 expression and phosphorylation, is impaired, as it has been previously de- scribed in cancer cells[30,56]. Consistent with these findings, we observed a lack of insulin responsiveness in terms of gene expression in PTEN deficient hepatocytes[30]. These data raise the hypothesis that PTEN downregulation in hepatocytes might, paradoxically, cause insulin resistance despite an increased activation of specific insulin effectors, such as Akt. Further studies are needed to clarify whether
PTEN downregulation in hepatocytes is a causal factor for insulin resistance in this organ.
PTEN IN NAFLD
Although liver-specific PTEN knockout mice have an overall improved systemic insulin sensitivity, they develop an important steatosis in the liver, suggesting that PTEN is required for an appropriate control of the hepatic lipid metabolism[54,55]. Consistent with these studies, he- patic PTEN expression is downregulated in obese and insulin resistant rat animal models and in humans hav- ing steatosis[30]. Further studies indicate that high levels of circulating free fatty acids, but not glucose or insulin, downregulate PTEN expression in hepatocytes[30]. PTEN downregulation by free fatty acids is triggered by an in- crease in miR-21, a miRNA targeting PTEN mRNA for degradation, through mTOR/NF-κB-dependent mecha- nisms[30,36]. In addition to an excess of circulating free fatty acids, a deregulated production of inflammatory cytokines by immune cells and/or of adipokines by the adipose tis- sue, as observed with NAFLD[57], can also independently, or synergistically with fatty acids, alter PTEN expression.
Indeed, inflammatory cytokines, such as transforming growth factor β[39,58-60], tumor necrosis factor (TNF)α[29,61], interleukin (IL)-6[62], IL-1[63], or adipokines such as leptin, resistin and adiponectin[64,65], have been reported to either up- or downregulate PTEN expression or activity in vari- ous cells. Although most of these cytokines/adipokines are clearly involved in liver insulin sensitivity and steato- sis/fibrosis/inflammation[57,66], it remains to be firmly established whether these factors modulate PTEN ex- pression/activity in the liver and whether there is a causal relationship between potential PTEN alterations induced by these cytokines/adipokines and their beneficial/detri- mental effects on the liver physiology.
PTEN loss of function in the liver leads to a progres- sive and step-wise development of steatohepatitis and fibrosis[54,55,67]. Consistent with studies using liver-specific PTEN knockout mice, decreased PTEN expression was also observed in the liver of rodents with hepatic fibrosis induced either by biliary stenosis or a choline-deficient
diet[68,69]. Finally, PTEN depletion in hepatoma cells in-
duces the expression of genes promoting inflammation, epithelial-to-mesenchymal transition, and fibrosis[70]. Taken together, these studies suggest that pathological dysregula- tion of PTEN expression/activity causing steatosis might also promote progression of this disorder towards differ- ent clinical stages of increasing severity. The molecular mechanisms by which PTEN deficiency triggers steatosis, inflammation, and fibrosis development in hepatocytes are still poorly defined. However, evidence indicates that de novo fatty acids synthesis is enhanced[54,55] in liver-specific PTEN knockout mice, whereas in cultured cells, accumu- lation of neutral lipids seems to rely mainly on increased fatty acids uptake and esterification[30]. These discrepant data might originate either from the different methodolo- gies used to investigate fatty acid metabolism or, more
likely, from the different extents of PTEN repression, i.e.
complete deletion in knockout mice vs 40%-80% down- regulation induced by fatty acids or silencing RNAs in cultured cells. Partial PTEN downregulation or total dele- tion can indeed mediate very different effects, as it was elegantly demonstrated in studies examining the role of PTEN in prostate tumor progression[41,71].
PTEN IN LIVER CARCINOGENESIS
The first evidence supporting a critical role for PTEN in liver cancer came from genetic studies in mice, where heterozygous deletion of PTEN was shown to induce atypical adenomatous liver hyperplasia[72]. Additional stud- ies then demonstrated that PTEN deficiency in the liver induces hepatomegaly, HCA, and HCC with ageing[54,55]. Weak expression or mutation/deletion of PTEN, as well as upregulation of miRNAs specifically targeting PTEN for degradation, are also frequently observed in human
HCC[11,1316,34,73-76]. However, the tumor suppressor activ-
ity of PTEN seems to principally involve its antagonistic effects on the anti-apoptotic, proliferative, and hypertro- phic activity of PI3K[77]; recent studies demonstrated that PTEN also plays an essential role in the nucleus to main- tain chromosomal stability and for DNA repair[78]. In ad- dition, there is evidence indicating that PTEN can modu- late cancer cell invasiveness by stabilizing E-cadherin/
β-catenin adherens junctional complexes[79,80]. Finally, we demonstrated that fatty acids-mediated PTEN downregu- lation in hepatocytes promotes cell proliferation, migra- tion, and invasiveness, in addition to modulating a set of genes involved in cell cycle regulation and HCC[70]. As inflammation, EMT and genomic alterations are typical features of HCC[81,82], impaired PTEN expression or activ- ity can thus represent an important step in progression of NAFLD towards HCC. Further studies are however still needed to confirm the relevance of PTEN as a prognos- tic marker for the risk of HCA/HCC development.
PTEN IN VIRAL HEPATITIS
Infections by HBV and HCV are major contributors to the high incidence of HCC, particularly in South-East Asia and Africa[83,84]. Similarly to NAFLD and NASH, HCV infection is strongly associated with liver insulin resistance and causes steatosis and fibrosis[85,86]. However, whether HBV infection causes similar liver disorders re- mains unclear[87].
Only a few studies have examined the involvement of PTEN in HBV/HCV-associated hepatocyte dysfunc- tion. The HBV-X protein (HBx) was shown to trigger uncontrolled Akt activation by downregulating PTEN expression in Chang liver cells, thereby enhancing the invasive potential of these cells[88,89]. In accordance with these data, PTEN overexpression in Chang cells reversed pro-survival signaling and inhibited apoptosis induced by HBx[90]. In addition, PTEN was also shown to prevent HBx-mediated induction of IGF-Ⅱ expression in hepa-
toma cell lines[91]. IGF-Ⅱ plays an essential role in HCC development; therefore, these data suggest that PTEN downregulation might make an important contribution to cell proliferation induced by HBx.
Direct evidence implicating a PTEN loss or gain of function in HCV-mediated liver diseases is scarce and only few studies investigate this issue. PTEN inactivation by post-translational phosphorylation was suggested to contribute to transactivation of SREBPs, which are ma- jor regulators of the lipid metabolism, in HCV-infected Huh-7 cells[92]. Correlative immunohistochemical analyses of human HCV-positive cirrhotic HCC also indicated that PTEN is downregulated in these tumors and that its expression was inversely correlated with expression of inducible nitric oxide synthase and cyclooxygenase Ⅱ. Interestingly, high PTEN expression was evaluated as a positive independent prognostic factor for the survival of HCV-positive cirrhotic HCC patients[93].
Further molecular, clinical, and epidemiological studies are now warranted to understand the detailed mechanisms by which HBV/HCV infections alter PTEN expression or activity in the liver, as well as the pathological outcomes of PTEN dysfunctions in HBV/HCV infections.
PTEN IN ALD
ALD also encompass a spectrum of histological and func- tional liver disorders, ranging from a relatively benign ste- atosis to alcoholic hepatitis, cirrhosis, and cancer[2]. Given the outcomes of alcohol abuse in the liver, and the effects of PTEN deletion or downregulation for the liver physiol- ogy, it could be expected that ethanol induces alterations of PTEN expression/activity in the liver. Surprisingly, increased apoptosis and decreased insulin signaling in he- patocytes of Long-Evans rats chronically fed with ethanol (serum ethanol levels is about 50 mmol/L) was associated with increased levels of PTEN mRNA and protein, thus suggesting that ethanol upregulates PTEN expression in the liver[94]. Increased hepatic PTEN expression was
also observed in rats exposed to alcohol in utero[95]. Con- sistent with these studies, chronic exposure of hepatoma HepG2E47 cells to ethanol increased PTEN expres- sion and subsequently increased the sensitivity of cells to TNFα-induced cytotoxicity and apoptosis[96]. In contrast, acute ethanol exposure did not affect PTEN expression in Huh-7 hepatoma cells. However, in these cells, ethanol increased the physical association between PTEN and the PI3K regulatory subunit p85a, which functionally resulted in a decreased Akt and downstream effectors activity[97].
Taken together, these studies indicated that, in contrast to the PTEN downregulation occurring with NAFLD, PTEN expression/activity is upregulated with ALD. This opposite regulation of a critical signaling effector strongly suggests that the mechanisms of insulin resistance and steatosis development in the context of NAFLD and ALD are distinct. In addition, PTEN might represent a differential diagnostic marker to distinguish between liver disorders with these different etiologies.
CONCLUSION
Accumulating evidence indicates that PTEN is a major dysregulated cellular factor contributing to the develop- ment of a broad spectrum of hepatic disorders, i.e. insulin resistance, steatosis, steatohepatitis, fibrosis, cirrhosis, and cancer (Figure 1). Indeed, hepatic PTEN expression/ac- tivity is altered in liver diseases associated with obesity, metabolic syndrome, viral infection, and alcohol con- sumption. Thus, it appears that dysregulation of PTEN expression/activity in hepatocytes represents an important and recurrent molecular mechanism contributing to the development of liver disorders with distinct etiologies.
Although hepatic steatosis is currently regarded as a begnin disease, progression to inflammation, fibrosis, and cirrhosis can lead to liver failure and development of HCC. There are multiple molecular factors involved in the progression of hepatic steatosis towards more severe stages and among those, dysregulation of PTEN expres-
Fatty acids Cytokines Adipokines microRNAs HBV, HCV Downregulation
inhibition
Mutations deletion
Upregulation stimulation Ethanol
Insulin resistance apoptosis Normal
expression
Steatosis, steatohepatitis Fibrosis HCA, HCC, CC Insulin sensitivity?
Glucose tolerance?
PTEN PTEN PTEN
Figure 1 Alterations of phosphatase and TENsin homolog deleted on chromosome 10 expression/activity in the liver by various etiological factors and associated liver disorders. HBV: Hepatitis B virus; HCV: Hepatitis C virus; HCA: Hepatocellular adenomas; CC: Cholangiocellular carcinomas; HCC: Hepatocellular carcinomas; PTEN: Phosphatase and TENsin homolog deleted on chromosome 10.
Pathological alterations of PTEN expression/activity in the liver and outcomes
Peyrou M et al. PTEN in liver diseases and cancer
sion/activity, more than PTEN mutations or deletions, could be a critical step in the occurrence and develop- ment of these diseases. In addition, PTEN alterations induced by high levels of free fatty acids or inflammatory cytokines, provide an interesting link between insulin re- sistance and steatosis, which might also explain, at least in part, the high risk factor for HCA/HCC associated with diabetes and obesity[98,99]. Given the tumor suppressor ac- tivity of PTEN, the role of steatosis and steatohepatitis as preneoplastic states in the hepatocyte malignant transfor- mation should also be re-evaluated. Additional studies are now required to carefully evaluate PTEN as a differential prognostic marker in liver pathologies with distinct etiolo- gies and to assess the pertinence of future therapeutic interventions to restore physiological PTEN expression in the liver to prevent, or to alleviate, hepatic metabolic dis- orders and HCC.
REFERENCES
1 Williams R. Global challenges in liver disease. Hepatology 2006;
44: 521-526
2 Yip WW, Burt AD. Alcoholic liver disease. Semin Diagn Pathol 2006; 23: 149-160
3 Marchesini G, Babini M. Nonalcoholic fatty liver disease and the metabolic syndrome. Minerva Cardioangiol 2006; 54:
229-239
4 Contos MJ, Choudhury J, Mills AS, Sanyal AJ. The histologic spectrum of nonalcoholic fatty liver disease. Clin Liver Dis 2004; 8: 481-500, vii
5 Farazi PA, DePinho RA. Hepatocellular carcinoma patho- genesis: from genes to environment. Nat Rev Cancer 2006; 6:
674-687
6 Avila MA, Berasain C, Sangro B, Prieto J. New therapies for hepatocellular carcinoma. Oncogene 2006; 25: 3866-3884 7 Thorgeirsson SS, Grisham JW. Molecular pathogenesis of
human hepatocellular carcinoma. Nat Genet 2002; 31: 339-346 8 Vinciguerra M, Foti M. PTEN and SHIP2 phosphoinositide
phosphatases as negative regulators of insulin signalling.
Arch Physiol Biochem 2006; 112: 89-104
9 Vinciguerra M, Foti M. PTEN at the crossroad of metabolic diseases and cancer in the liver. Ann Hepatol 2008; 7: 192-199 10 He L, Hou X, Kanel G, Zeng N, Galicia V, Wang Y, Yang J,
Wu H, Birnbaum MJ, Stiles BL. The critical role of AKT2 in hepatic steatosis induced by PTEN loss. Am J Pathol 2010; 176:
2302-2308
11 Wang L, Wang WL, Zhang Y, Guo SP, Zhang J, Li QL. Epi- genetic and genetic alterations of PTEN in hepatocellular carcinoma. Hepatol Res 2007; 37: 389-396
12 Chow LM, Baker SJ. PTEN function in normal and neoplastic growth. Cancer Lett 2006; 241: 184-196
13 Hu TH, Huang CC, Lin PR, Chang HW, Ger LP, Lin YW, Changchien CS, Lee CM, Tai MH. Expression and prognostic role of tumor suppressor gene PTEN/MMAC1/TEP1 in he- patocellular carcinoma. Cancer 2003; 97: 1929-1940
14 Dong-Dong L, Xi-Ran Z, Xiang-Rong C. Expression and significance of new tumor suppressor gene PTEN in primary liver cancer. J Cell Mol Med 2003; 7: 67-71
15 Fujiwara Y, Hoon DS, Yamada T, Umeshita K, Gotoh M, Sakon M, Nishisho I, Monden M. PTEN / MMAC1 mutation and frequent loss of heterozygosity identified in chromosome 10q in a subset of hepatocellular carcinomas. Jpn J Cancer Res 2000; 91: 287-292
16 Yao YJ, Ping XL, Zhang H, Chen FF, Lee PK, Ahsan H, Chen CJ, Lee PH, Peacocke M, Santella RM, Tsou HC. PTEN/
MMAC1 mutations in hepatocellular carcinomas. Oncogene
1999; 18: 3181-3185
17 Downes CP, Perera N, Ross S, Leslie NR. Substrate specificity and acute regulation of the tumour suppressor phosphatase, PTEN. Biochem Soc Symp 2007; 69-80
18 Weng LP, Brown JL, Eng C. PTEN coordinates G(1) arrest by down-regulating cyclin D1 via its protein phosphatase activ- ity and up-regulating p27 via its lipid phosphatase activity in a breast cancer model. Hum Mol Genet 2001; 10: 599-604 19 Cai XM, Tao BB, Wang LY, Liang YL, Jin JW, Yang Y, Hu
YL, Zha XL. Protein phosphatase activity of PTEN inhibited the invasion of glioma cells with epidermal growth factor receptor mutation type III expression. Int J Cancer 2005; 117:
905-912
20 Davidson L, Maccario H, Perera NM, Yang X, Spinelli L, Tibarewal P, Glancy B, Gray A, Weijer CJ, Downes CP, Leslie NR. Suppression of cellular proliferation and invasion by the concerted lipid and protein phosphatase activities of PTEN.
Oncogene 2010; 29: 687-697
21 Tamguney T, Stokoe D. New insights into PTEN. J Cell Sci 2007; 120: 4071-4079
22 Pan L, Lu J, Wang X, Han L, Zhang Y, Han S, Huang B. His- tone deacetylase inhibitor trichostatin a potentiates doxoru- bicin-induced apoptosis by up-regulating PTEN expression.
Cancer 2007; 109: 1676-1688
23 Virolle T, Adamson ED, Baron V, Birle D, Mercola D, Mus- telin T, de Belle I. The Egr-1 transcription factor directly ac- tivates PTEN during irradiation-induced signalling. Nat Cell Biol 2001; 3: 1124-1128
24 Stambolic V, MacPherson D, Sas D, Lin Y, Snow B, Jang Y, Benchimol S, Mak TW. Regulation of PTEN transcription by p53. Mol Cell 2001; 8: 317-325
25 Zhang W, Wu N, Li Z, Wang L, Jin J, Zha XL. PPARgamma activator rosiglitazone inhibits cell migration via upregula- tion of PTEN in human hepatocarcinoma cell line BEL-7404.
Cancer Biol Ther 2006; 5: 1008-1014
26 Edwin F, Singh R, Endersby R, Baker SJ, Patel TB. The tumor suppressor PTEN is necessary for human Sprouty 2-mediated inhibition of cell proliferation. J Biol Chem 2006; 281: 4816-4822 27 Shen YH, Zhang L, Gan Y, Wang X, Wang J, LeMaire SA, Co- selli JS, Wang XL. Up-regulation of PTEN (phosphatase and tensin homolog deleted on chromosome ten) mediates p38 MAPK stress signal-induced inhibition of insulin signaling.
A cross-talk between stress signaling and insulin signaling in resistin-treated human endothelial cells. J Biol Chem 2006; 281:
7727-7736
28 Palomero T, Sulis ML, Cortina M, Real PJ, Barnes K, Ciofani M, Caparros E, Buteau J, Brown K, Perkins SL, Bhagat G, Agarwal AM, Basso G, Castillo M, Nagase S, Cordon-Cardo C, Parsons R, Zúñiga-Pflücker JC, Dominguez M, Ferrando AA. Mutational loss of PTEN induces resistance to NOTCH1 inhibition in T-cell leukemia. Nat Med 2007; 13: 1203-1210 29 Vasudevan KM, Gurumurthy S, Rangnekar VM. Suppres-
sion of PTEN expression by NF-kappa B prevents apoptosis.
Mol Cell Biol 2004; 24: 1007-1021
30 Vinciguerra M, Veyrat-Durebex C, Moukil MA, Rubbia- Brandt L, Rohner-Jeanrenaud F, Foti M. PTEN down-regula- tion by unsaturated fatty acids triggers hepatic steatosis via an NF-kappaBp65/mTOR-dependent mechanism. Gastroen- terology 2008; 134: 268-280
31 Chappell WH, Green TD, Spengeman JD, McCubrey JA, Akula SM, Bertrand FE. Increased protein expression of the PTEN tumor suppressor in the presence of constitutively ac- tive Notch-1. Cell Cycle 2005; 4: 1389-1395
32 Whelan JT, Forbes SL, Bertrand FE. CBF-1 (RBP-J kappa) binds to the PTEN promoter and regulates PTEN gene ex- pression. Cell Cycle 2007; 6: 80-84
33 Hettinger K, Vikhanskaya F, Poh MK, Lee MK, de Belle I, Zhang JT, Reddy SA, Sabapathy K. c-Jun promotes cellular survival by suppression of PTEN. Cell Death Differ 2007; 14:
218-229
34 Meng F, Henson R, Wehbe-Janek H, Ghoshal K, Jacob ST, Pa- tel T. MicroRNA-21 regulates expression of the PTEN tumor suppressor gene in human hepatocellular cancer. Gastroenter- ology 2007; 133: 647-658
35 Pezzolesi MG, Platzer P, Waite KA, Eng C. Differential ex- pression of PTEN-targeting microRNAs miR-19a and miR-21 in Cowden syndrome. Am J Hum Genet 2008; 82: 1141-1149 36 Vinciguerra M, Sgroi A, Veyrat-Durebex C, Rubbia-Brandt L,
Buhler LH, Foti M. Unsaturated fatty acids inhibit the expres- sion of tumor suppressor phosphatase and tensin homolog (PTEN) via microRNA-21 up-regulation in hepatocytes.
Hepatology 2009; 49: 1176-1184
37 Xiao C, Srinivasan L, Calado DP, Patterson HC, Zhang B, Wang J, Henderson JM, Kutok JL, Rajewsky K. Lymphopro- liferative disease and autoimmunity in mice with increased miR-17-92 expression in lymphocytes. Nat Immunol 2008; 9:
405-414
38 Yang H, Kong W, He L, Zhao JJ, O'Donnell JD, Wang J, Wenham RM, Coppola D, Kruk PA, Nicosia SV, Cheng JQ.
MicroRNA expression profiling in human ovarian cancer:
miR-214 induces cell survival and cisplatin resistance by tar- geting PTEN. Cancer Res 2008; 68: 425-433
39 Kato M, Putta S, Wang M, Yuan H, Lanting L, Nair I, Gunn A, Nakagawa Y, Shimano H, Todorov I, Rossi JJ, Natarajan R.
TGF-beta activates Akt kinase through a microRNA-depen- dent amplifying circuit targeting PTEN. Nat Cell Biol 2009; 11:
881-889
40 Wang X, Jiang X. Post-translational regulation of PTEN. On- cogene 2008; 27: 5454-5463
41 Salmena L, Carracedo A, Pandolfi PP. Tenets of PTEN tumor suppression. Cell 2008; 133: 403-414
42 Tamura M, Gu J, Matsumoto K, Aota S, Parsons R, Yamada KM. Inhibition of cell migration, spreading, and focal adhe- sions by tumor suppressor PTEN. Science 1998; 280: 1614-1617 43 Wu X, Hepner K, Castelino-Prabhu S, Do D, Kaye MB, Yuan
XJ, Wood J, Ross C, Sawyers CL, Whang YE. Evidence for regulation of the PTEN tumor suppressor by a membrane- localized multi-PDZ domain containing scaffold protein MAGI-2. Proc Natl Acad Sci USA 2000; 97: 4233-4238
44 Valiente M, Andrés-Pons A, Gomar B, Torres J, Gil A, Tap- parel C, Antonarakis SE, Pulido R. Binding of PTEN to spe- cific PDZ domains contributes to PTEN protein stability and phosphorylation by microtubule-associated serine/threonine kinases. J Biol Chem 2005; 280: 28936-28943
45 Tang Y, Eng C. p53 down-regulates phosphatase and tensin homologue deleted on chromosome 10 protein stability par- tially through caspase-mediated degradation in cells with proteasome dysfunction. Cancer Res 2006; 66: 6139-6148 46 Takahashi Y, Morales FC, Kreimann EL, Georgescu MM.
PTEN tumor suppressor associates with NHERF proteins to attenuate PDGF receptor signaling. EMBO J 2006; 25: 910-920 47 Okahara F, Ikawa H, Kanaho Y, Maehama T. Regulation of
PTEN phosphorylation and stability by a tumor suppressor candidate protein. J Biol Chem 2004; 279: 45300-45303
48 Sesti G, Federici M, Hribal ML, Lauro D, Sbraccia P, Lauro R.
Defects of the insulin receptor substrate (IRS) system in hu- man metabolic disorders. FASEB J 2001; 15: 2099-2111 49 Shepherd PR. Mechanisms regulating phosphoinositide 3-ki-
nase signalling in insulin-sensitive tissues. Acta Physiol Scand 2005; 183: 3-12
50 Wijesekara N, Konrad D, Eweida M, Jefferies C, Liadis N, Giacca A, Crackower M, Suzuki A, Mak TW, Kahn CR, Klip A, Woo M. Muscle-specific Pten deletion protects against insulin resistance and diabetes. Mol Cell Biol 2005; 25: 1135-1145 51 Wong JT, Kim PT, Peacock JW, Yau TY, Mui AL, Chung SW,
Sossi V, Doudet D, Green D, Ruth TJ, Parsons R, Verchere CB, Ong CJ. Pten (phosphatase and tensin homologue gene) haploinsufficiency promotes insulin hypersensitivity. Diabe- tologia 2007; 50: 395-403
52 Kurlawalla-Martinez C, Stiles B, Wang Y, Devaskar SU,
Kahn BB, Wu H. Insulin hypersensitivity and resistance to streptozotocin-induced diabetes in mice lacking PTEN in adi- pose tissue. Mol Cell Biol 2005; 25: 2498-2510
53 Butler M, McKay RA, Popoff IJ, Gaarde WA, Witchell D, Murray SF, Dean NM, Bhanot S, Monia BP. Specific inhibi- tion of PTEN expression reverses hyperglycemia in diabetic mice. Diabetes 2002; 51: 1028-1034
54 Horie Y, Suzuki A, Kataoka E, Sasaki T, Hamada K, Sasaki J, Mizuno K, Hasegawa G, Kishimoto H, Iizuka M, Naito M, Enomoto K, Watanabe S, Mak TW, Nakano T. Hepatocyte- specific Pten deficiency results in steatohepatitis and hepato- cellular carcinomas. J Clin Invest 2004; 113: 1774-1783 55 Stiles B, Wang Y, Stahl A, Bassilian S, Lee WP, Kim YJ, Sher-
win R, Devaskar S, Lesche R, Magnuson MA, Wu H. Liver- specific deletion of negative regulator Pten results in fatty liver and insulin hypersensitivity [corrected]. Proc Natl Acad Sci USA 2004; 101: 2082-2087
56 Lackey J, Barnett J, Davidson L, Batty IH, Leslie NR, Downes CP. Loss of PTEN selectively desensitizes upstream IGF1 and insulin signaling. Oncogene 2007; 26: 7132-7142
57 Tilg H, Moschen AR. Insulin resistance, inflammation, and non-alcoholic fatty liver disease. Trends Endocrinol Metab 2008;
19: 371-379
58 Zhang L, Yu Q, He J, Zha X. Study of the PTEN gene expres- sion and FAK phosphorylation in human hepatocarcinoma tissues and cell lines. Mol Cell Biochem 2004; 262: 25-33 59 Mahimainathan L, Das F, Venkatesan B, Choudhury GG.
Mesangial cell hypertrophy by high glucose is mediated by downregulation of the tumor suppressor PTEN. Diabetes 2006; 55: 2115-2125
60 Yang Y, Zhou F, Fang Z, Wang L, Li Z, Sun L, Wang C, Yao W, Cai X, Jin J, Zha X. Post-transcriptional and post-translational regulation of PTEN by transforming growth factor-beta1. J Cell Biochem 2009; 106: 1102-1112
61 Kim S, Domon-Dell C, Kang J, Chung DH, Freund JN, Evers BM. Down-regulation of the tumor suppressor PTEN by the tumor necrosis factor-alpha/nuclear factor-kappaB (NF- kappaB)-inducing kinase/NF-kappaB pathway is linked to a default IkappaB-alpha autoregulatory loop. J Biol Chem 2004;
279: 4285-4291
62 Löffler D, Brocke-Heidrich K, Pfeifer G, Stocsits C, Hacker- müller J, Kretzschmar AK, Burger R, Gramatzki M, Blumert C, Bauer K, Cvijic H, Ullmann AK, Stadler PF, Horn F. Interleu- kin-6 dependent survival of multiple myeloma cells involves the Stat3-mediated induction of microRNA-21 through a highly conserved enhancer. Blood 2007; 110: 1330-1333 63 Barbieri SS, Ruggiero L, Tremoli E, Weksler BB. Suppressing
PTEN activity by tobacco smoke plus interleukin-1beta mod- ulates dissociation of VE-cadherin/beta-catenin complexes in endothelium. Arterioscler Thromb Vasc Biol 2008; 28: 732-738 64 Ning K, Miller LC, Laidlaw HA, Burgess LA, Perera NM,
Downes CP, Leslie NR, Ashford ML. A novel leptin signal- ling pathway via PTEN inhibition in hypothalamic cell lines and pancreatic beta-cells. EMBO J 2006; 25: 2377-2387 65 Lam JB, Chow KH, Xu A, Lam KS, Liu J, Wong NS, Moon
RT, Shepherd PR, Cooper GJ, Wang Y. Adiponectin haplo- insufficiency promotes mammary tumor development in MMTV-PyVT mice by modulation of phosphatase and tensin homolog activities. PLoS One 2009; 4: e4968
66 Budhu A, Wang XW. The role of cytokines in hepatocellular carcinoma. J Leukoc Biol 2006; 80: 1197-1213
67 Suzuki A, de la Pompa JL, Stambolic V, Elia AJ, Sasaki T, del Barco Barrantes I, Ho A, Wakeham A, Itie A, Khoo W, Fuku- moto M, Mak TW. High cancer susceptibility and embryonic lethality associated with mutation of the PTEN tumor sup- pressor gene in mice. Curr Biol 1998; 8: 1169-1178
68 Hao LS, Zhang XL, An JY, Karlin J, Tian XP, Dun ZN, Xie SR, Chen S. PTEN expression is down-regulated in liver tissues of rats with hepatic fibrosis induced by biliary stenosis. AP- MIS 2009; 117: 681-691
Peyrou M et al. PTEN in liver diseases and cancer
69 Wang B, Majumder S, Nuovo G, Kutay H, Volinia S, Patel T, Schmittgen TD, Croce C, Ghoshal K, Jacob ST. Role of mi- croRNA-155 at early stages of hepatocarcinogenesis induced by choline-deficient and amino acid-defined diet in C57BL/6 mice. Hepatology 2009; 50: 1152-1161
70 Vinciguerra M, Carrozzino F, Peyrou M, Carlone S, Monte- sano R, Benelli R, Foti M. Unsaturated fatty acids promote hepatoma proliferation and progression through down- regulation of the tumor suppressor PTEN. J Hepatol 2009; 50:
1132-1141
71 Trotman LC, Niki M, Dotan ZA, Koutcher JA, Di Cristofano A, Xiao A, Khoo AS, Roy-Burman P, Greenberg NM, Van Dyke T, Cordon-Cardo C, Pandolfi PP. Pten dose dictates cancer progression in the prostate. PLoS Biol 2003; 1: E59 72 Podsypanina K, Ellenson LH, Nemes A, Gu J, Tamura M,
Yamada KM, Cordon-Cardo C, Catoretti G, Fisher PE, Par- sons R. Mutation of Pten/Mmac1 in mice causes neoplasia in multiple organ systems. Proc Natl Acad Sci USA 1999; 96:
1563-1568
73 Wan XW, Jiang M, Cao HF, He YQ, Liu SQ, Qiu XH, Wu MC, Wang HY. The alteration of PTEN tumor suppressor expres- sion and its association with the histopathological features of human primary hepatocellular carcinoma. J Cancer Res Clin Oncol 2003; 129: 100-106
74 Cotler SJ, Hay N, Xie H, Chen ML, Xu PZ, Layden TJ, Guz- man G. Immunohistochemical expression of components of the Akt-mTORC1 pathway is associated with hepatocellular carcinoma in patients with chronic liver disease. Dig Dis Sci 2008; 53: 844-849
75 Wu SK, Wang BJ, Yang Y, Feng XH, Zhao XP, Yang DL.
Expression of PTEN, PPM1A and P-Smad2 in hepatocellular carcinomas and adjacent liver tissues. World J Gastroenterol 2007; 13: 4554-4559
76 Hu TH, Wang CC, Huang CC, Chen CL, Hung CH, Chen CH, Wang JH, Lu SN, Lee CM, Changchien CS, Tai MH.
Down-regulation of tumor suppressor gene PTEN, overex- pression of p53, plus high proliferating cell nuclear antigen index predict poor patient outcome of hepatocellular carci- noma after resection. Oncol Rep 2007; 18: 1417-1426
77 Yuan TL, Cantley LC. PI3K pathway alterations in cancer:
variations on a theme. Oncogene 2008; 27: 5497-5510
78 Shen WH, Balajee AS, Wang J, Wu H, Eng C, Pandolfi PP, Yin Y. Essential role for nuclear PTEN in maintaining chro- mosomal integrity. Cell 2007; 128: 157-170
79 Kotelevets L, van Hengel J, Bruyneel E, Mareel M, van Roy F, Chastre E. The lipid phosphatase activity of PTEN is critical for stabilizing intercellular junctions and reverting invasive- ness. J Cell Biol 2001; 155: 1129-1135
80 Kotelevets L, van Hengel J, Bruyneel E, Mareel M, van Roy F, Chastre E. Implication of the MAGI-1b/PTEN signalosome in stabilization of adherens junctions and suppression of in- vasiveness. FASEB J 2005; 19: 115-117
81 Laurent-Puig P, Zucman-Rossi J. Genetics of hepatocellular tumors. Oncogene 2006; 25: 3778-3786
82 Lee TK, Poon RT, Yuen AP, Ling MT, Kwok WK, Wang XH, Wong YC, Guan XY, Man K, Chau KL, Fan ST. Twist overex- pression correlates with hepatocellular carcinoma metastasis through induction of epithelial-mesenchymal transition. Clin
Cancer Res 2006; 12: 5369-5376
83 Michielsen PP, Francque SM, van Dongen JL. Viral hepatitis and hepatocellular carcinoma. World J Surg Oncol 2005; 3: 27 84 Tan A, Yeh SH, Liu CJ, Cheung C, Chen PJ. Viral hepato-
carcinogenesis: from infection to cancer. Liver Int 2008; 28:
175-188
85 Negro F, Alaei M. Hepatitis C virus and type 2 diabetes.
World J Gastroenterol 2009; 15: 1537-1547
86 Negro F, Sanyal AJ. Hepatitis C virus, steatosis and lipid abnormalities: clinical and pathogenic data. Liver Int 2009; 29 Suppl 2: 26-37
87 Wang CC, Hsu CS, Liu CJ, Kao JH, Chen DS. Association of chronic hepatitis B virus infection with insulin resistance and hepatic steatosis. J Gastroenterol Hepatol 2008; 23: 779-782 88 Chung TW, Lee YC, Ko JH, Kim CH. Hepatitis B Virus X
protein modulates the expression of PTEN by inhibiting the function of p53, a transcriptional activator in liver cells. Can- cer Res 2003; 63: 3453-3458
89 Chung TW, Lee YC, Kim CH. Hepatitis B viral HBx induces matrix metalloproteinase-9 gene expression through activa- tion of ERK and PI-3K/AKT pathways: involvement of inva- sive potential. FASEB J 2004; 18: 1123-1125
90 Kang-Park S, Im JH, Lee JH, Lee YI. PTEN modulates hepa- titis B virus-X protein induced survival signaling in Chang liver cells. Virus Res 2006; 122: 53-60
91 Kang-Park S, Lee YI, Lee YI. PTEN modulates insulin-like growth factor II (IGF-II)-mediated signaling; the protein phosphatase activity of PTEN downregulates IGF-II expres- sion in hepatoma cells. FEBS Lett 2003; 545: 203-208
92 Waris G, Felmlee DJ, Negro F, Siddiqui A. Hepatitis C virus induces proteolytic cleavage of sterol regulatory element binding proteins and stimulates their phosphorylation via oxidative stress. J Virol 2007; 81: 8122-8130
93 Rahman MA, Kyriazanos ID, Ono T, Yamanoi A, Kohno H, Tsuchiya M, Nagasue N. Impact of PTEN expression on the outcome of hepatitis C virus-positive cirrhotic hepatocellular carcinoma patients: possible relationship with COX II and inducible nitric oxide synthase. Int J Cancer 2002; 100: 152-157 94 Yeon JE, Califano S, Xu J, Wands JR, De La Monte SM. Poten-
tial role of PTEN phosphatase in ethanol-impaired survival signaling in the liver. Hepatology 2003; 38: 703-714
95 Yao XH, Nyomba BL. Hepatic insulin resistance induced by prenatal alcohol exposure is associated with reduced PTEN and TRB3 acetylation in adult rat offspring. Am J Physiol Regul Integr Comp Physiol 2008; 294: R1797-R1806
96 Shulga N, Hoek JB, Pastorino JG. Elevated PTEN levels ac- count for the increased sensitivity of ethanol-exposed cells to tumor necrosis factor-induced cytotoxicity. J Biol Chem 2005;
280: 9416-9424
97 He J, de la Monte S, Wands JR. Acute ethanol exposure inhib- its insulin signaling in the liver. Hepatology 2007; 46: 1791-1800 98 Caldwell SH, Crespo DM, Kang HS, Al-Osaimi AM. Obesity
and hepatocellular carcinoma. Gastroenterology 2004; 127:
S97-S103
99 El-Serag HB, Hampel H, Javadi F. The association between diabetes and hepatocellular carcinoma: a systematic review of epidemiologic evidence. Clin Gastroenterol Hepatol 2006; 4:
369-380
S- Editor Wang JL L- Editor Stewart GJ E- Editor Zheng XM