p16 is a major inactivation target in hepatocellular carcinoma

Integrated Bioinformatic Analysis Identifies TIPIN as a Prognostic Biomarker in Hepatocellular Carcinoma

Background

Gene expression and DNA methylation analyses have long been used to identify cancer markers. However, a combination analysis of the gene expression and DNA methylation has yet to be performed to identify potential biomarkers of hepatocellular carcinoma (HCC).

Methods

By matching gene expression profiles and promoter methylation data in The Cancer Genome Atlas (TCGA), genes with discrepant expression as well as genes with differential promoter methylation were identified. High-expression genes with low promoter methylation were defined as epigenetically induced (EI), while low-expression genes with high promoter methylation were defined as epigenetically suppressed (ES). The human protein interaction network was further integrated to construct the EI/ES gene interaction network, and the key genes in the subnet were identified as potential HCC biomarkers. The expression differences and prognostic values were verified in TCGA and Gene Expression Omnibus (GEO) databases, as well as with tissue chip technology.

Results

Four key genes were identified: TIPIN, RBM15B, DUSP28, and TRIM31, which demonstrated the differential gene expression and prognostic value in TCGA and GEO databases. Tissue microarray analysis (TMA) revealed that TIPIN levels were altered in HCC. The upregulated TIPIN expression was associated with worse overall survival. Univariate and multivariate analyses showed that the TIPIN expression was an independent predictor of HCC.

Conclusion

TIPIN might be a potential novel prognostic biomarker for HCC.

Primary sclerosing cholangitis and the risk of cancer, cardiovascular disease, and all-cause mortality: a systematic review and meta-analysis of cohort studies

A diagnosis of primary sclerosing cholangitis (PSC) has been associated with increased risk of hepatobiliary cancers, colorectal cancer and all-cause mortality in several studies, while associations with cardiovascular disease have been inconsistent. We conducted a systematic review and meta-analysis of published cohort studies on the topic to summarize these associations. PubMed and Embase databases were searched up to January 13th, 2020. Cohort studies on PSC and risk of cancer, cardiovascular disease, or mortality were included. Summary relative risks (RRs) and 95% confidence intervals (95% CIs) were estimated using random effects models. The summary RR (95% CI) comparing persons with PSC to persons without PSC was 584.37 (269.42-1267.51, I² = 89%, n = 4) for cholangiocarcinoma (CCA), 155.54 (125.34-193.02, I² = 0%, n = 3) for hepatobiliary cancer, 30.22 (11.99-76.17, I² = 0%, n = 2) for liver cancer, 16.92 (8.73-32.78, I² = 88%, n = 4) for gastrointestinal cancer, 7.56 (2.42-23.62, I² = 0%, n = 3) for pancreatic cancer, 6.10 (4.19-8.87, I² = 14%, n = 7) for colorectal cancer (CRC), 4.13 (2.99-5.71, I² = 80%, n = 5) for total cancer, 3.55 (2.94-4.28, I² = 46%, n = 5) for all-cause mortality, and 1.57 (0.25-9.69, I² = 79%, n = 2) for cardiovascular disease. Strong positive associations were observed between PSC and risk of CCA, hepatobiliary cancer, liver cancer, gastrointestinal cancer, pancreatic cancer, CRC, total cancer, and all-cause mortality, but not for cardiovascular disease.

Hepatitis C virus core protein activates proteasomal activator 28 gamma to downregulate p16 levels via ubiquitin-independent proteasomal degradation

Proteasomal activator 28 gamma (PA28γ), an essential constituent of the 20S proteasome, is frequently overexpressed in hepatocellular carcinoma. Hepatitis C virus (HCV) core protein is recently known to activate PA28γ expression in human hepatocytes via upregulation of p53 levels; however, its role in HCV tumorigenesis remains unknown. Here, we found that HCV core-activated PA28γ downregulates p16 levels via ubiquitin-independent proteasomal degradation. As a result, HCV core protein activated the Rb-E2F pathway to stimulate cell cycle progression from G₁ to S phase, resulting in an increase in cell proliferation. The potential of HCV core protein to induce these effects was almost completely abolished by either PA28γ knockdown or p16 overexpression, confirming the role of the PA28γ-mediated p16 degradation in HCV tumorigenesis.

Hepatocellular carcinoma: old friends and new tricks

Hepatocellular carcinoma (HCC) is the most prevalent primary liver cancer and a leading cause of cancer-related deaths worldwide. Ninety percent of HCC cases arise from cirrhosis, during which liver cells undergo chronic cycles of necrosis and regeneration. The complex genomic landscape of HCC has been extensively investigated to draw correlations between recurrently mutated pathways and patient prognosis. However, our limited success with targeted therapy shows that knowing the presence of somatic mutations alone is insufficient for us to gauge the full spectrum of their functional consequences in the context of tumor evolution. In addition, the current molecular classification of HCC offers little information on the relationship between the molecular features and immunological properties of HCC tumors and their immune microenvironment. This review introduces current challenges and advancements made in HCC surveillance, diagnosis, and treatment. We also discuss the suite of HCC-associated genetic changes and describe recent studies that provide evidence for an evolving functional model and its implications for understanding and targeting HCC progression.

Potent Activity of Composite Cyclin Dependent Kinase Inhibition against Hepatocellular Carcinoma

Alterations in cell cycle regulators are common in hepatocellular carcinoma (HCC). We tested the efficacy of composite inhibition of CDKs 1, 2, 5, and 9 through dinaciclib on HCC. In vitro, dinaciclib exhibited potent antiproliferative activities in HCC cell lines regardless of Rb or c-myc expression levels. Dinaciclib significantly downregulated the phosphorylation of Rb (target of CDKs 1 and 2), ataxia telangiectasia mutated kinase (target of CDK5), and RNA polymerase II (target of CDK9) in the HCC cells. In xenograft studies, mice receiving dinaciclib tolerated the treatment well without significant body weight changes and exhibited a significantly slower tumor growth rate than the mice receiving vehicles. RNA interference (RNAi) of CDKs 1 and 9 was more effective in inhibiting the cell proliferation of HCC cells than RNAi of CDKs 2 and 5. Overexpression of CDK9 significantly reduced the efficacy of dinaciclib in HCC cells, but overexpression of CDK1 did not. In conclusion, composite inhibition of CDKs 1, 2, 5, and 9 through dinaciclib exhibited potent in vitro and in vivo activity against HCC. CDK9 inhibition might be the crucial mechanism.

Investigation of new treatment option for hepatocellular carcinoma: a combination of sorafenib with usnic acid

Objectives

Sorafenib (SOR) is an orally administered molecular targeted agent in the systemic chemotherapy of hepatocellular carcinoma (HCC). However, the partial response of SOR is limited due to its adverse side effect and high heterogeneity and resistant phenotype of HCC. In the current study, we investigated synergistic effects of SOR and usnic acid (UA) on HCC cell lines including HepG2 and SNU-449, and a normal cell line, HUVEC.

Methods

The antiproliferative and apoptotic effects of combination therapy and SOR alone were analysed by WST-1 and Annexin V analysis, respectively. Furthermore, cell cycle, gene expression analysis of SOR-targeted kinases and acridine orange–ethidium bromide staining were also performed in combined treatments.

Key findings

Our results demonstrated that SOR and UA combination indicated a strong synergism in HCC cell lines and reduced SOR toxicity in HUVEC cells. Additionally, the combination treatment SOR and UA significantly induced much more apoptotic cell death and G0/G1 arrest through downregulation of SOR-targeted kinases.

Conclusions

Consequently, SOR and UA combination could be a new therapeutic strategy for HCC treatment.

Genomic Medicine and Implications for Hepatocellular Carcinoma Prevention and Therapy

The pathogenesis of hepatocellular carcinoma (HCC) is poorly understood, but recent advances in genomics have increased our understanding of the mechanisms by which hepatitis B virus, hepatitis C virus, alcohol, fatty liver disease, and other environmental factors, such as aflatoxin, cause liver cancer. Genetic analyses of liver tissues from patients have provided important information about tumor initiation and progression. Findings from these studies can potentially be used to individualize the management of HCC. In addition to sorafenib, other multi-kinase inhibitors have been approved recently for treatment of HCC, and the preliminary success of immunotherapy has raised hopes. Continued progress in genomic medicine could improve classification of HCCs based on their molecular features and lead to new treatments for patients with liver cancer.

The role of usnic acid-induced apoptosis and autophagy in hepatocellular carcinoma

Usnic acid (UA) is a multifunctional bioactive lichen secondary metabolite with potential anti-cancer properties. Although the promising therapeutic effects of UA have been investigated in different cancer cell lines, the mechanism driving UA-induced cell death has yet to be elucidated. As the type of cell death (apoptosis or autophagy) induced by UA may vary depending on the cancer cell type, we first studied the cytotoxic effects of UA in HEPG2 (HBV(−)) and SNU-449(HBV(+)) hepatocellular carcinoma (HCC) cell lines. HCC cell viability was considerably reduced in a dose-dependent manner at 12, 24, and 48 h after treatment with UA ( p < 0.05). However, SNU-449 cells were more sensitive to UA than HEPG2 cells. UA also induced apoptotic cell death in HCC cells with cell cycle arrest at G0/G1 and G2/M phase depending on the genetic profile of each cell type. On the other hand, we observed acidic vesicular organelles in HCC cells after 36 h of UA treatment. Taken together, these findings suggest that UA stimulates apoptosis and autophagy in HEPG2 and SNU-449 cells without damaging normal control cells. Thus, UA might be a potential therapeutic compound for HCC treatment. However, there is a need for further studies investigating the death-promoting or preventing roles for autophagy and the molecular signaling mechanisms induced by UA treatment.

Meta-analysis of CDKN2A methylation to find its role in prostate cancer development and progression, and also to find the effect of CDKN2A expression on disease-free survival (PRISMA)

BACKGROUND

Reduction of cyclin-dependent kinase inhibitor 2A (CDKN2A) (p16 and p14) expression through DNA methylation has been reported in prostate cancer (PCa). This meta-analysis was conducted to assess the difference of p16 and p14 methylation between PCa and different histological types of nonmalignant controls and the correlation of p16 or p14 methylation with clinicopathological features of PCa.

METHODS

According to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement criteria, articles were searched in PubMed, Embase, EBSCO, Wanfang, and CNKI databases. The strength of correlation was calculated by the pooled odds ratios (ORs) and their corresponding 95% confidence intervals (95% CIs). Trial sequential analysis (TSA) was used to estimate the required population information for significant results.

RESULTS

A total of 20 studies published from 1997 to 2017 were identified in this meta-analysis, including 1140 PCa patients and 530 cases without cancer. Only p16 methylation in PCa was significantly higher than in benign prostatic lesions (OR = 4.72, P = .011), but had a similar level in PCa and adjacent tissues or high-grade prostatic intraepithelial neoplasias (HGPIN). TSA revealed that this analysis on p16 methylation is a false positive result in cancer versus benign prostatic lesions (the estimated required information size of 5116 participants). p16 methylation was not correlated with PCa in the urine and blood. Besides, p16 methylation was not linked to clinical stage, prostate-specific antigen (PSA) level, and Gleason score (GS) of patients with PCa. p14 methylation was not correlated with PCa in tissue and urine samples. No correlation was observed between p14 methylation and clinical stage or GS. CDKN2A mutation and copy number alteration were not associated with prognosis of PCa in overall survival and disease-free survival. CDKN2A expression was not correlated with the prognosis of PCa in overall survival (492 cases) (P > .1), while CDKN2A expression was significantly associated with a poor disease-free survival (P < .01).

CONCLUSION

CDKN2A methylation may not be significantly associated with the development, progression of PCa. Although CDKN2A expression had an unfavorable prognosis in disease-free survival. More studies are needed to confirm our results.

p16 Methylation was associated with the development, age, hepatic viruses infection of hepatocellular carcinoma, and p16 expression had a poor survival: A systematic meta-analysis (PRISMA)

BACKGROUND

Loss of tumor suppressor gene p16 expression via promoter methylation has been reported in hepatocellular carcinoma (HCC). This meta-analysis was conducted to evaluate the correlation between p16 methylation and HCC. Additionally, we also analyzed the potential prognostic role of p16 methylation, expression or alteration-associated HCC.

METHODS

Online databases based on the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guideline were performed to analyze the role of p16 gene in HCC. The combined odds ratios (ORs) or hazard ratios (HRs) and their 95% confidence intervals (95% CIs) were summarized.

RESULTS

Final 3105 HCCs and 808 non-tumor controls (chronic hepatitis and liver cirrhosis) were performed in this meta-analysis. p16 promoter methylation in HCC was significantly higher than in chronic hepatitis and chronic hepatitis in tissue and blood samples. In addition, p16 promoter methylation was notably higher in patients >50 years' old than in patients aged <50 years, and it was higher in hepatitis B virus (HBV) or hepatitis C virus (HCV)-positive HCC than in hepatic viruses-negative HCC. However, p16 promoter methylation was not correlated with sex, cirrhosis, tumor differentiation, clinical stage. No association was found between p16 methylation or alteration and the prognosis of patients with HCC in overall survival (OS) and disease-free survival (DFS). Although p16 expression was significantly correlated with a poor prognosis in OS and DFS (P < .05) CONCLUSIONS:: Our results indicate that p16 methylation was linked to the development, age, HBV, and HCV infection of HCC. p16 methylation or alteration was not associated with the prognosis, but p16 expression was linked to a poor survival.

Bidirectional transcription of Linc00441 and RB1 via H3K27 modification-dependent way promotes hepatocellular carcinoma

The retinoblastoma gene (RB1), a known tumor-suppressor gene (TSG), was decreased in multiple cancers including hepatocellular carcinoma (HCC). Here we focused on the bidirectional transcripted long noncoding RNA (Linc00441) with neighbor gene RB1 to investigate whether Linc00441 is involved in the suppression of RB1 in HCC. We found that aberrant upregulated intranuclear Linc00441 was reversely correlated with RB1 expression in human HCC samples. The gain- and loss-of-function investigation revealed that Linc00441 could promote the proliferation of HCC cells in vitro and in vivo with an apoptosis suppression and cell cycle rearrangement. Furthermore, RNA pull-down assay indicated the decreased level of RB1 induced by Linc00441 was associated with the incidental methylation by DNMT3A recruited by Linc00441. On the contrary, the transcription factor (TCF-4) enhanced H3K27 acetylation and direct transcription factor for Linc00441 was responsible for the upregulation of Linc00441 in HCC. In conclusion, the epigenetic interaction between Linc00441 and bidirectional transcripted neighbor RB1 may be a de novo theory cutting-point for the inactivation of RB1 in HCC and may serve as targeting site for tumor therapy in the future.

Epigenetic mechanisms regulating the development of hepatocellular carcinoma and their promise for therapeutics

Hepatocellular carcinoma (HCC) is one of the most common cancers around the globe and third most fatal malignancy. Chronic liver disorders such as chronic hepatitis and liver cirrhosis often lead to the development of HCC. Accumulation of genetic and epigenetic alterations are involved in the development of HCC. Genetic research sparked by recent developments in next generation sequencing has identified the frequency of genetic alterations that occur in HCC and has led to the identification of genetic hotspots. Emerging evidence suggests that epigenetic aberrations are strongly associated with the initiation and development of HCC. Various important genes encoding tumor suppressors including P16, RASSF1A, DLC-1, RUNX3 and SOCS-1 are targets of epigenetic dysregulation during the development of HCC. The present review discusses the importance of epigenetic regulations including DNA methylation, histone modification and microRNA mediated regulation of gene expression during tumorigenesis and their use as disease biomarkers. Furthermore, these epigenetic alterations have been discussed in relationship with promising therapeutic perspectives for HCC and related cancers.

Detecting abnormal methylation of tumor suppressor genes GSTP1, P16, RIZ1, and RASSF1A in hepatocellular carcinoma and its clinical significance

Hepatocellular carcinoma (HCC) has a high rate of mortality. Further studies into epigenetic changes in HCC, particularly the abnormal methylation of tumor suppressor genes (TSGs), are required, since these changes may provide novel biomarkers for early screening and diagnosis of HCC. By using methylation-specific polymerase chain reaction (MSP), the present study detected the methylation status in the promoter region of 4 candidate TSGs, GSTP1, P16, RIZ1, and RASSF1A, respectively, in 35 paired HCC and tumor-adjacent liver tissues in addition to 20 normal liver tissues. Their effect on the initiation and progression of HCC was also investigated by analyzing the clinicopathological data. The results of the present study revealed that the methylation level of RIZ1 and GSTP1 genes in HCC was significantly increased compared with that in the adjacent tissues (P<0.01) and the normal liver tissues (P<0.01). The methylation frequency of P16 and RASSF1A genes was not significantly increased compared with that observed in the adjacent tissues (P>0.05) but was significantly increased compared with the normal tissues (P<0.01). In HCC tissues, the methylation frequency of the GSTP1 gene in tumors with capsular invasion was significantly increased compared with that in tumors without capsular invasion (P<0.05). The methylation frequency of P16 gene in hepatitis B surface antigen (HbsAg)-positive HCC patients was significantly increased compared with that in HbsAg-negative patients (P<0.05). The methylation status of RIZ1 and RASSF1A genes was not significantly correlated with the clinicopathological data (P>0.05). Previous studies have demonstrated that the methylation status of RIZ1 and GSTP1 genes is HCC-specific, and thus may be used as a biomarker to assist the clinical diagnosis of HCC. While the methylation of GSTP1 gene promoter may associate with the invasiveness of HCC, chronic hepatitis B virus infection may be the cause of methylation-induced P16 inactivation.

Mediator subunit 23 overexpression as a novel target for suppressing proliferation and tumorigenesis in hepatocellular carcinoma

BACKGROUND AND AIM

Hepatocellular carcinoma (HCC) is the fifth most frequent cancer in the world. However, the molecular mechanisms involved in HCC are still poorly understood. Here, we study the role of mediator subunit 23 (MED23), a component of the Mediator complex, in hepatocarcinogenesis.

METHODS

We detected MED23 expression in HCC samples by real-time polymerase chain reaction (PCR) and immunohistochemistry analysis. We also knocked down and overexpressed MED23 to explore its functional role in hepatoma cell growth. The cell cycle was examined by flow cytometry analysis, and protein expression was examined by Western blot. A xenograft mouse model was used to determine whether MED23 is involved in tumorigenesis.

RESULTS

MED23 was frequently upregulated in human HCC tissues compared with paired adjacent non-tumorous liver tissues. The hepatoma cells also showed increased MED23 expression. MED23 knockdown inhibited hepatoma cell growth, whereas overexpression of MED23 promoted cell growth. Knockdown of MED23 induced a G1 to S phase arrest. Moreover, MED23 regulated the expression of p16(INK) (4a) (p16) and the phosphorylation of retinoblastoma protein (Rb). p16 was transcriptionally upregulated, and its promoter was demethylated. The G1 to S phase arrest induced by MED23 knockdown was aborted after p16 was silenced. Furthermore, MED23 knockdown suppressed tumorigenesis and regulated p16/Rb signaling in vivo.

CONCLUSIONS

Taken together, our study suggests that MED23 plays an important role in hepatocarcinogenesis, and it may be a novel target for HCC therapy.

Immunohistochemical profile of ductal adenocarcinoma of the prostate

Ductal adenocarcinoma of the prostate (DAC) is considered to be an aggressive subtype of prostate cancer with greater risk of progression than acinar adenocarcinoma (AC). It has been debated whether DAC is a distinct subtype or a morphological variant of AC. Our aim was to examine the protein expression of DAC and to compare the results with AC. A tissue microarray was constructed from 60 DAC and 46 AC matched by Gleason score. The slides were stained for 28 immunomarkers (estrogen, progesterone and androgen receptor, prolactin, PSA, prostein, PSMA, PSAP, CDX2, lysozyme, villin, monoclonal CEA, CK7, CK20, HMWCK, p63, p504s, c-myc, EGFR, Ki-67, p16, p21, p27, p53, PTEN, ERG, PAX-2, and PAX-8). HMWCK was positive in 8.5 % of DAC, but negative in all cases of AC (p = 0.045). p16 was positive in 53.3 % of DAC and in 26.1 % of AC (p = 0.005). p53 was positive in 42.4 % of DAC and 26.7 % of AC (p = 0.031). A distinct patchy positivity of CK20 was seen in 23.7 % of DAC, and this pattern was also seen in 9.1 % of AC (p = 0.047). Villin was positive in 3.4 % of DAC while expression was negative in AC. Ki-67 labeling index was significantly higher in DAC than in AC (mean 9.2 % [95 % CI 6.4-12.0] and 2.6 % [1.9-3.4], p < 0.001). While there is some overlap in the immunohistochemical expression of DAC and AC, the differences between these two morphotypes of prostatic carcinoma are consistent with DAC having a more aggressive phenotype than AC.

Promoter hypermethylation of p14 (ARF) , RB, and INK4 gene family in hepatocellular carcinoma with hepatitis B virus infection

Both hepatitis B virus (HBV) and gene methylation play important roles in hepatocarcinogenesis. However, their association between HBV infection and gene methylation is not fully understood. Cell cycle control involving RB1 gene-related cell inhibitors is one of the main regulatory pathways were reported to be altered in hepatocellular carcinoma (HCC). The purpose of this research is to assess the methylation status of p14 (ARF) and INK4 gene family (p14 (ARF) , p15 (INK4B) , p16 (INK4A) , and p18 (INK4C) ) in HCC with HBV infection and HCC without it, and discuss possible role of HBV-induced hypermethylation in the mechanism of hepatocarcinogenesis. Methylation status of RB, p14 (ARF) , and INK4 gene family in 64 case of HCC with HBV infection and 24 cases without it were detected by methylation-specific polymerase chain reaction, and HBV-DNA of the plasma were detected by quantitative real-time polymerase chain reaction. p14 (ARF) , p15 (INK4B) , p16 (INK4A) , and RB hypermethylation were observed in 30 (34.1%), 50 (56.8%), 62 (70.5%), and 24(27.3%) of 88 hepatocellular carcinomas, respectively. Methylation frequencies of them between HCC with HBV infection and HCC without it were 43.8% versus 8.3 % (p14 (ARF) ), 68.9% versus 25% (p15 (INK4B) ), 90.6% versus 16.7% ( p16 (INK4A) ), and 28.1 % versus 25% (RB), respectively. In HBV-associated HCC, the numbers of methylated genes were also more than HCC without virus infection, more than two methylated genes were seen in 48 of 64 (75 %) cases; more than three methylated genes were found in 32 of 64 (50%); correspondently, no one case has more than two genes methylated. p18 (INK4C) methylation product was not found in cancerous or non-cancerous tissues of 88 HCC. HBV infection is associated with p14 (ARF) , p15 (INK4B) , p16 (INK4A) , and RB gene methylation (P = 0.048, 0.035, 0.02); HBV-DNA replication is associated with p14 (ARF) , p15 (INK4B) , p16 (INK4A) , and RB gene methylation (P = 0.048, 0.035, 0.02); high rate of p14 (ARF) , p15 (INK4B) , and p16 (INK4A) in HCC with HBV infection suggests that HBV-induced hypermethylation may be one of the mechanisms of HBV involved in hepatocellular carcinogenesis.

Anti-tumor effect of 5-aza-2'-deoxycytidine by inhibiting telomerase activity in hepatocellular carcinoma cells

AIM: To investigate the effect of the demethylating reagent 5-aza-2’-deoxycitidine (DAC) on telomerase activity in hepatocellular carcinoma (HCC) cell lines, SMMC-7721 and HepG2.

METHODS: The related gene expression in cell lines was examined by real-time reverse transcription-polymerase chain reaction and Western blotting analysis. The telomerase activity was examined by telomeric repeat amplification protocol-enzyme-linked immunosorbent assay and DNA methylation was determined by methylation-specific polymerase chain reaction.

RESULTS: The telomerase activity was significantly reduced in both cell lines treated with DAC, accompanied by downregulation of telomerase reverse transcriptase (hTERT). We also observed the effect of DAC on the methylation status of hTERT promoter and the expression of regulatory genes, such as c-myc, p15, p16, p21, E2F1, and WT1. The methylation status of hTERT promoter could be reversed in SMMC-7721 by DAC, but not in HepG2 cells. However, p16 expression could be reactivated by demethylation of its promoter, and c-Myc expression was repressed in both cell lines. Moreover, DAC could enhance the sensitivity to the chemotherapeutic agents, such as cisplatin, by induction of apoptosis of HCC cells.

CONCLUSION: The DAC exerts its anti-tumor effects in HCC cells by inhibiting the telomerase activity.

Expression of p14(ARF), p15(INK4b), p16(INK4a) and skp2 increases during esophageal squamous cell cancer progression

Esophageal carcinoma is the sixth most common cause of cancer-related mortality in the world. Senescence and apoptosis are assumed to be two main mechanisms that inhibit age-related carcinogenesis. p14(ARF), p15(INK4b) and p16(INK4a), which are known to induce senescence by regulating G(1) cell cycle arrest, have been identified as senescence markers. However, the mechanism by which senescence and apoptosis causes neoplasia in esophageal squamous cell carcinoma (ESCC) has not been identified. In this study, 20 cases of normal esophageal tissues, 11 cases of esophageal intraepithelial dysplasia (EID) and 60 cases of ESCC were obtained and pathologically diagnosed. Immunohistochemical staining was performed to assess the expression of p14(ARF), p15(INK4b), p16(INK4a), skp2, bcl-2 and ki-67. The senescence markers p14(ARF) and p16(INK4a) were found to be expressed in 15 and 10% of the normal tissues, 82 and 73% of the EID cases and 100 and 88% of the ESCC cases, respectively. The expression of p15(INK4b) was low in normal tissues, while 92% of the ESCC specimens were diffusely and markedly stained, involving the basal, middle and upper portion of the epithelium. The nuclear expression markers ki-67 and skp2 were highly expressed in ESCC tissues (100 and 72%, respectively). bcl-2 was expressed weakly in normal tissues (10%) and demonstrated various staining patterns in carcinoma specimens (strong in 60%, negative in 40%). MI was 0.09% in normal tissues and 0.95% in the ESCC specimens. Apart from the increased proliferation in esophageal carcinogenesis, as indicated in the ki-67 and skp2 indices, there was an increased expression of senescence-associated molecular markers in the ESCC specimens, which indicates that the senescence pathway may be activated and become a part of cancer development. Of greatest interest to us was that, when compared with clinical information, the expression of the senescence markers was markedly high in the poorly differentiated specimens with lymph node metastasis, indicating that senescence markers may have diagnostic potential in clinical settings.

Hepatitis C virus Core protein overcomes stress-induced premature senescence by down-regulating p16 expression via DNA methylation

Hepatitis C virus Core plays a vital role in the development of hepatocellular carcinoma; however, the mechanism is still controversial. Here, we show that Core overcomes premature senescence provoked by a reactive oxygen species inducer, H2O2, in human liver cells. For this effect, Core down-regulated levels of p16 via promoter hypermethylation and subsequently induced phosphorylation of Rb in the presence of H2O2. Levels of p21 and p27, however, were little affected by Core under the condition. The potentials of Core to inactivate Rb and suppress H2O2-mediated cellular senescence were abolished when levels of p16 were recovered by either exogenous complementation or inhibition of DNA methylation. Considering that cellular senescence provoked by oxidative stresses is an important tumor suppression process, our present study provides a new strategy by which HCV promotes development of hepatocellular carcinoma.

Hepatitis C virus Core protein stimulates cell growth by down-regulating p16 expression via DNA methylation

Hepatitis C virus Core plays a vital role in the development of hepatocellular carcinoma; however, its action mechanism is still controversial. Here, we showed that Core down-regulated levels of p16, resulting in inactivation of Rb and subsequent activation of E2F1, which lead to growth stimulation of hepatocytes. For this effect, Core inhibited p16 expression by inducing promoter hypermethylation via up-regulation of DNA methyltransferase 1 (DNMT1) and DNMT3b. The growth stimulatory effect of Core was abolished when levels of p16 were restored by either exogenous complementation or treatment with 5-Aza-2'dC, indicating that the effect is critical for the stimulation of cell growth by Core.

Molecular classification of hepatocellular carcinoma anno 2011

Hepatocellular carcinoma has an increasing incidence and high mortality. Treatment options are limited if the disease is not diagnosed in its early stage. The natural course of the disease is aggressive but not always predictable. Molecular profiling is a promising tool for classification in order to optimize prognosis prediction and treatment for an individual patient. In the last decade a large amount of studies has been conducted to better classify hepatocellular carcinomas. The focus of this review is on implications of molecular classification for prognosis and therapeutic decision making in HCC patients. Most studies used microarray technique for genome wide profiling, but other methods to detect genomic changes and microRNA are gaining interest. The whole genome profiling studies identified differences in affected signalling and tried to relate this to prognosis. Some common subgroups were identified, such as the proliferation cluster and the beta-catenin cluster. However, there is still little overlap between most studies. Better study design and bio-informatical analysis might help in this context.

The association of frequent allelic loss on 17p13.1 with early metastatic recurrence of hepatocellular carcinoma after liver transplantation

BACKGROUND AND OBJECTIVES

Identification and characterization of loss of heterozygosity (LOH) can determine putative tumor suppressor genes (TSGs) and provide a variety of molecular markers for hepatocellular carcinoma (HCC). This study aimed to investigate LOH status on chromosomes 4q, 6q, 8p, 9p, and 17p, and to explore their clinical significances in HCC post-liver transplantation.

METHODS

A total of 37 patients with HCC who underwent liver transplantation were enrolled. LOH was examined using 34 microsatellite markers located on 4q13-3q5, 6q27, 8p22-p23, 9p21-p22, and 17p12-p13.

RESULTS

The frequency of LOH at each microsatellite locus ranged from 23% to 75%, with a mean value of 53.1%. Frequencies of LOH on 4q, 6q, 8p, 9p, and 17p were 62% (23 of 37), 30% (11 of 37), 49% (18 of 37), 46% (16 of 35), and 68% (25 of 37), respectively. LOHs on certain chromosomal regions were significantly associated with age, AFP level, tumor size, tumor multiplicity, histological grade, and metastatic recurrence.

CONCLUSIONS

LOH on 17p13.1 correlated to metastatic HCC recurrence, while LOH on 4q and 8p was found to be associated with progression of HCC. Thus, potential novel biomarkers or TSGs for prognosis and treatment of HCC may harbor on these regions.

Promoter methylation of CDKN2A and lack of p16 expression characterize patients with hepatocellular carcinoma

BACKGROUND

The product of CDKN2A, p16 is an essential regulator of the cell cycle controlling the entry into the S-phase. Herein, we evaluated CDKN2A promoter methylation and p16 protein expression for the differentiation of hepatocellular carcinoma (HCC) from other liver tumors.

METHODS

Tumor and corresponding non-tumor liver tissue samples were obtained from 85 patients with liver tumors. CDKN2A promoter methylation was studied using MethyLight technique and methylation-specific PCR (MSP). In the MethyLight analysis, samples with > or = 4% of PMR (percentage of methylated reference) were regarded as hypermethylated. p16 expression was evaluated by immunohistochemistry in tissue sections (n = 148) obtained from 81 patients using an immunoreactivity score (IRS) ranging from 0 (no expression) to 6 (strong expression).

RESULTS

Hypermethylation of the CDKN2A promoter was found in 23 HCCs (69.7%; mean PMR = 42.34 +/- 27.8%), six (20.7%; mean PMR = 31.85 +/- 18%) liver metastases and in the extralesional tissue of only one patient. Using MSP, 32% of the non-tumor (n = 85), 70% of the HCCs, 40% of the CCCs and 24% of the liver metastases were hypermethylated. Correspondingly, nuclear p16 expression was found immunohistochemically in five (10.9%, mean IRS = 0.5) HCCs, 23 (92%; mean IRS = 4.9) metastases and only occasionally in hepatocytes of non-lesional liver tissues (mean IRS = 1.2). The difference of CDKN2A-methylation and p16 protein expression between HCCs and liver metastases was statistically significant (p < 0.01, respectively).

CONCLUSION

Promoter methylation of CDKN2A gene and lack of p16 expression characterize patients with HCC.

Epigenetic mechanisms involved in the pathogenesis of hepatobiliary malignancies

Primary tumors of the liver and biliary tree are increasing in frequency and portend a miserable prognosis. Epigenetic regulation of gene expression has emerged as a fundamental aspect of cancer development and progression. The molecular mechanisms of carcinogenesis in hepatocellular carcinoma and cholangiocarcinoma involve a complex interplay of both genetic and epigenetic factors. Recent studies investigating the possible epigenetic mechanisms induced in the disease have shed new light on the molecular underpinnings of hepatobiliary cancers. In addition, epigenetic modifications of DNA in cancer and precancerous lesions offer hope and the promise of novel biomarkers for early cancer detection, prediction, prognosis and response to treatment. Furthermore, the reversal of epigenetic changes represents a potential target for novel therapeutic strategies and medication design.

Methylation profiling of tumor suppressor genes and oncogenes in hepatitis virus-related hepatocellular carcinoma in northern India

Hepatocellular carcinoma (HCC) is the fifth most common cancer in India, and hepatitis B virus and hepatitis C virus infections are major risk factors. DNA methylation alterations have been linked to various carcinomas in different populations. Aberrant CpG island methylation of genes has been recognized in HCC, information is limited for hepatitis virus-related hepatocarcinogenesis. HCC risk has not previously been associated with gene-specific DNA methylation in India. Promoter region methylation of a panel of six tumor suppressor genes (CDKN2A, CDKN2B, CDH1, GSTP1, SOCS1, and APC) and three oncogenes (MYC, HRAS, and KRAS) was determined by methylation-specific PCR among 23 HCC samples and 20 control hepatitis samples. CDKN2B methylation frequency in HCC was double that for hepatitis, and methylation allele density of APC, GSTP1, and CDKN2B increased 2.2-, 2.3-, and 7.6-fold, respectively. Epigenetic silencing of tumor suppressor genes starts during viral infection and progresses toward HCC with the chronicity of the disease. Findings of altered methylation status support involvement of these tumor suppressor genes in HCC. MYC showed decreased methylation in HCC, relative to hepatitis. These observations on DNA methylation suggest the involvement of CDKN2B, SOCS1, CDH1, GSTP1, and MYC in pathogenesis of HCC in India and implicate altered DNA methylation in the molecular pathogenesis.

Accelerated cellular senescence in myelodysplastic syndrome

OBJECTIVE

To investigate the contribution of cellular senescence to the progression and prognosis of myelodysplastic syndrome (MDS).

MATERIALS AND METHODS

We have analyzed the expression of p16INK4a in bone marrow mononuclear cells or CD34(+) cells from 53 patients with MDS, 12 acute myeloid leukemia (AML), and 11 healthy controls. Additionally, We have assessed quantitatively senescence-associated beta-galactosidase (SA-beta-gal) staining on bone marrow mononuclear cells from MDS and AML patients, HL60 and SHI-1 leukemia cell lines, and healthy control cells.

RESULTS

An upregulated expression of senescence-associated molecular marker p16INK4a was found in MDS compared with healthy controls, while a lower expression of p16INK4a was observed in AML compared with healthy controls. International Prognostic Scoring System score was negatively correlated with the percentage of p16INK4a-positive cells. The SA-beta-gal activity measured by mean percentage of positive cells was significantly higher in MDS cases when compared with controls. Meanwhile, percentage of SA-beta-gal-positive cells was also remarkably higher in dysplastic cells of MDS when compared to nondysplastic cells from MDS.

CONCLUSIONS

These results of our present study suggested an accelerated cellular senescence occurred in MDS, and the cellular senescence may be involved in the progression and prognosis of MDS.

Adaptor protein Crk induces Src-dependent activation of p38 MAPK in regulation of synovial sarcoma cell proliferation

The adaptor protein Crk mediates intracellular signaling related to cell motility and proliferation and is implicated in human tumorigenesis. The role of Crk in the growth of human sarcoma has remained unclear, however. The present study shows that Crk-induced activation of Src and subsequent signaling by p38 mitogen-activated protein kinase (MAPK) contribute to the enhanced proliferation of human synovial sarcoma cells. Depletion of Crk by RNA interference markedly inhibited proliferation of the synovial sarcoma cell lines HS-SYII, SYO-1, and Fuji as well as prevented anchorage-independent growth. Conversely, reconstitution with CrkII by authentic small interfering RNA-resistant Crk gene restored proliferation in Crk-silenced SYO-1 cells. Crk-depleted synovial sarcoma cells manifested enhanced transcriptional activity and expression of the p16(INK4A) gene, resulting in their accumulation in G(1) phase of the cell cycle. In response to hepatocyte growth factor stimulation, Crk prominently induced the tyrosine phosphorylation of Grb2-associated binder 1 through activation of Src and focal adhesion kinase, and the Src family kinase inhibitor PP2 almost completely inhibited the proliferation of SYO-1 cells. Crk also induced the phosphorylation of p38 MAPK, and SB203580, a p38 MAPK-specific inhibitor, increased expression of p16(INK4A) gene in SYO-1 cells. Furthermore, SB203580 or depletion of p38 MAPK by small interfering RNA suppressed both the phosphorylation of Akt triggered by hepatocyte growth factor and the proliferation of SYO-1 cells. These results suggest that Crk promotes proliferation of human synovial sarcoma cells through activation of Src and its downstream signaling by a novel p38 MAPK-Akt pathway, with these signaling molecules providing potent new targets for molecular therapeutics.

Progression of hypermethylation of the p16(INK4A) gene from normal liver to nontumorous liver and hepatocellular carcinoma: an evaluation using quantitative PCR analysis

The aim of this study was to determine to what extent hypermethylation of the p16(INK4A) (p16) gene promoter is increased in nontumorous liver tissues compared with in normal liver, using two quantitative methylation-specific polymerase chain reaction (MS-PCR) methods and a bisulfite sequencing method. Methylation of the p16 gene was detected more frequently in nontumorous liver than in normal liver using the TaqMan PCR method. Methylation indices also were significantly higher in nontumorous than in normal liver. However, the bisulfite sequencing method did not detect significantly more methylation of the p16 gene in nontumorous than normal liver, nor was there a significant difference in the level of p16 mRNA. There may be a greater proportion of cells which contain methylated p16 in nontumorous than in normal liver. However, the difference was so small that the functional relevance to hepatocarcinogenesis remains elusive.

Differences in molecular alterations of hepatocellular carcinoma between patients with a sustained virological response and those with hepatitis C virus infection

BACKGROUND/AIMS

The mechanism of hepatocarcinogenesis remains unclear in patients in whom hepatitis C virus (HCV) disappears after interferon (IFN) therapy. We compared molecular alterations in hepatocellular carcinoma (HCC) between patients with a sustained virological response (SVR) to IFN and patients with HCV.

METHODS

The study group comprised 44 patients with HCV and 13 patients with SVR. One patient in the SVR group had two tumour nodules, both of which were examined. Mitochondrial DNA (mtDNA) mutations in displacement-loop lesions were directly sequenced. Mutation of the TP53 gene was examined by direct sequencing. The methylation status of p16, p15, p14, RB and PTEN genes was evaluated by a methylation-specific polymerase chain reaction.

RESULTS

The average number of mtDNA mutations was 4.2 in 44 HCCs with HCV and 2.0 in 14 HCCs with SVR (P=0.0021). mtDNA mutation was less frequently detected in HCCs from patients with SVR than in patients with HCV. TP53 mutations were detected in 12 (27%) of 44 HCCs with HCV and 2 (14%) of 14 SVR-HCCs. Hypermethylation of the p16, p15, p14, RB and PTEN promoters was, respectively, detected in 34, 13, 8, 12 and 11 of 44 HCCs from patients with HCV and 14, 0, 0, 2 and 2 of 14 HCCs from patients with SVR (P=0.049, 0.021, 0.085, 0.322 and 0.402). Hypermethylation of p16 was one of the most important alterations in SVR-HCC.

CONCLUSIONS

Molecular alterations in hepatocarcinogenesis of patients with SVR-HCC were different from those of patients with continuous HCV infection.

Gain of GRHL2 is associated with early recurrence of hepatocellular carcinoma

BACKGROUND/AIMS

The aim of this study is to identify genomic changes that might be implicated in hepatocellular carcinoma (HCC) progression, and evaluate the associations with clinico-pathological features.

METHODS

The genomic DNA of 17 hepatoma cell lines was analyzed using Affymetrix GeneChip Human Mapping 50K high-density oligonucleotide arrays. We selected representative genes from recurrent amplified regions and measured the copy number of these genes in 70 HCC clinical samples.

RESULTS

We found 10 recurrent high-grade gain regions spanning less than 3 Mb in at least two hepatoma cell lines, and selected 10 representative genes. The copy number was almost normal in non-cancerous tissue and frequently amplified in Edmondson grade II or III HCC compared to Edmondson grade I HCC. Gain of TAX1BP1 in 7p15.2-1 was associated with larger tumor size and positivity of HCV antibody, and gain of CCND1 in 11q13.2-3 was associated with larger tumor size by multivariate analysis. Furthermore, a gain of GRHL2 in 8q22.3 was associated with early recurrence of HCC, controlling for clinical parameters. Decreased GRHL2 expression by RNA interference inhibits the growth of hepatoma cells, suggesting its association with cell proliferation.

CONCLUSIONS

A gain of GRHL2 might be a predictive marker for HCC recurrence.

Differential roles of p16INK4A and p14ARF genes in prognosis of oral carcinoma

BACKGROUND

Oral cancer patients are found to have poor clinical outcome and high disease recurrence rate, in spite of an aggressive treatment regimen. The inactivation of INK4A/ARF loci is reported to be second to p53 inactivation in human cancers. The purpose of this study was to assess the prognostic significance of the molecular aberrations in the INK4A locus for effective identification of aggressive oral carcinoma cases needing alternate therapy.

MATERIALS AND METHODS

The study composed of 116 patients freshly diagnosed with oral carcinoma. The genetic and epigenetic status of the p16(INK4A) and p14(ARF) genes was evaluated. The relation between these genic alterations and different treatment end points, such as residual disease (initial response), disease recurrence, and overall survival, along with the standard clinical markers, were analyzed.

RESULTS

62% of the study cases had p16(INK4A) gene abnormalities, with deletion accounting for 33% and methylation for 29%. Alterations in p14(ARF) gene either by deletion (12%) and/or methylation (18%) were observed in 30% of the cases. p16(INK4A) deletion was associated with aggressive tumors, as evidenced by the nodal involvement of the disease. Low or absence of p16(INK4A) protein adversely affected the initial treatment response. Promoter methylation of p16(INK4A) was associated with increased disease recurrence and acts as an independent predictor for worse prognosis. Surprisingly, p14(ARF) methylation associated with lower recurrence rate in oral cancer patients with a good clinical outcome. Overall survival of these patients was associated with tumor size, nodal disease, and p16(INK4A) protein expression pattern. Our results indicate that p16(INK4A) and p14(ARF) alterations constitute a major molecular abnormality in oral cancer cases.

CONCLUSION

The molecular profile of INK4A/ARF locus, both at DNA and protein level, could be used as a prognostic biomarker for assessing the aggressiveness of disease in oral carcinoma patients. The study further shows the opposing clinical effect of these two genes, transcribed from the same locus, in oral cancer patients.

Acromegaly: re-thinking the cancer risk

Acromegaly is characterized by sustained elevation of circulating growth hormone (GH) and insulin-like growth factor I (IGF-I), and is clearly associated with increased morbidity and overall mortality mainly due to cardiovascular, metabolic, and respiratory diseases. Although cancer-related mortality varies widely amongst retroperspective studies, it appears to be consistently elevated mainly in patients with uncontrolled disease. We review individual tumor types including neoplasms of the colon, breast, prostate, and thyroid where in vitro, animal studies, and studies in non-acromegalic cancer patients have established a role for the GH/IGF-I axis in tumor progression and possibly initiation. We highlight deficiencies in data in acromegalic patients where the evidence is less convincing. Instead, we explore the hypothesis that acromegaly, independent of hormone secretion, is a disease that heralds genetic and/or epigenetic alterations predisposing to cancer risk elsewhere.

Differential DNA methylation associated with hepatitis B virus infection in hepatocellular carcinoma

Gene inactivation through DNA hypermethylation plays a pivotal role in carcinogenesis. This study aimed to profile aberrant DNA methylation in different stages of liver disease, namely noncirrhosis, cirrhosis and hepatocellular carcinoma (HCC), and also to clarify the influence of hepatitis B virus (HBV) infection on the aberrant DNA methylation in HCCs. Promoter methylation in p14(ARF), p16(INK4a), O(6)-methylguanine-DNA methyltransferase (MGMT), glutathione S-transferase pi (GSTP1) and E-cadherin (E-Cad) genes of 58 HCCs paired with adjacent nontumorous tissues was assayed by methylation-specific PCR. HBV infection was determined using a hepatitis B virus surface antigen (HBsAg) serological assay. The frequency of p16(INK4a) promoter methylation increased from noncirrhotic, cirrhotic, to HCC tissues (noncirrhotic vs. HCC, p < 0.001), while that of GSTP1 promoter methylation increased in cirrhotic tissues compared to noncirrhotic ones (p = 0.029). The frequency of GSTP1 promoter hypermethylation is significantly higher in HCC than in nontumorous tissues (p = 0.022) from HBsAg-positive patients, but not the HBsAg-negative controls (p = 0.289). While the frequency of E-Cad promoter hypermethylation remained high in both nontumorous tissues and HCCs from HBsAg-positive patients (p = 0.438), it was lower in HCCs than in nontumorous tissues from HBsAg-negative patients (p = 0.002). In contrast, the frequency of p16(INK4a), MGMT and p14(ARF) promoter hypermethylation in HCCs was unrelated to HBsAg status. In conclusion, aberrant DNA methylation may begin at different stages of liver disease in a gene-dependent manner. Moreover, HBV infection may enhance or maintain GSTP1 and E-Cad promoter methylation and thereby affect hepatocarcinogenesis.

Loss of p53 and Ink4a/Arf cooperate in a cell autonomous fashion to induce metastasis of hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death worldwide. HCC patients frequently present with disease that has metastasized to other regions of the liver, the portal vein, lymph nodes, or lungs, leading to poor prognoses. Therefore, model systems that allow exploration of the molecular mechanisms underlying metastasis in this disease are greatly needed. We describe here a metastatic HCC model generated after the somatic introduction of the mouse polyoma virus middle T antigen to mice with liver-specific deletion of the Trp53 tumor suppressor locus and show the cell autonomous effect of p53 loss of function on HCC metastasis. We additionally find that cholangiocarcinoma also develops in these mice, and some tumors display features of both HCC and cholangiocarcinoma, suggestive of origin from liver progenitor cells. Concomitant loss of the Ink4a/Arf tumor suppressor locus accelerates tumor formation and metastasis, suggesting potential roles for the p16 and p19 tumor suppressors in this process. Significantly, tumor cell lines isolated from tumors lacking both Trp53 and Ink4a/Arf display enhanced invasion activity in vitro relative to those lacking Trp53 alone. Thus, our data illustrate a new model system amenable for the analysis of HCC metastasis.

RB loss abrogates cell cycle control and genome integrity to promote liver tumorigenesis

BACKGROUND & AIMS

The retinoblastoma (RB) tumor suppressor is functionally inactivated in most hepatocellular carcinomas (HCC), although the mechanisms by which RB suppresses liver tumorigenesis are poorly defined. We investigated the impact of RB loss on carcinogen-induced liver tumorigenesis.

METHODS

Mice harboring liver-specific RB ablation and normal littermates were exposed to the hepatocarcinogen diethylnitrosamine (DEN). The influence of RB loss on liver tumorigenesis was assessed by evaluating tumor multiplicity, proliferation, and genome integrity within tumors arising in RB-deficient and wild-type livers. In silico analyses were used to probe the association between gene expression signatures for RB loss and chromosomal instability and the ability of genes up-regulated by RB loss to predict the survival of human HCC patients.

RESULTS

RB deficiency significantly increased tumor multiplicity in livers exposed to DEN. Although hepatocytes in nontumor regions of DEN-exposed livers were quiescent regardless of RB status, tumors arising in RB-deficient livers were significantly more proliferative than those in normal livers and expressed high levels of RB/E2F target genes. Analysis of genes up-regulated by RB loss demonstrated significant overlap with a gene expression signature associated with chromosomal instability. Correspondingly, tumors arising in RB-deficient livers were significantly more likely to harbor hepatocytes exhibiting altered ploidy. Finally, gene expression analysis of human HCCs demonstrated that elevated expression of RB-regulated genes independently predicts poor survival.

CONCLUSIONS

RB deletion in the mouse liver enhances DEN-induced tumorigenesis, associated with increased hepatocyte proliferation and compromised genome integrity. Evaluation of RB status may be a useful prognostic factor in human HCC.

Senescence and apoptosis in carcinogenesis of cervical squamous carcinoma

Senescence and apoptosis are two key mechanisms that protect against cancer development. Many cell cycle regulators, such as p14(ARF), p15(INK4b) and p16(INK4a), are important in G1 cell cycle arrest and oncogene-induced senescence. The bcl-2 protein is one of the key components that control apoptosis, while the p53 protein plays key roles in both mechanisms. The genes of these key regulator proteins are often mutated or deleted in various malignancies. It is unknown how senescence and apoptosis are regulated in one of the most common tumors of the female genital tract, cervical squamous cell carcinoma (SCC). In this study the, expression of senescence, apoptosis and proliferation markers in normal cervical epithelium, cervical intraepithelial neoplasia (CIN) and SCC are characterized via immunohistochemical staining for p14(ARF), p15(INK4b), p16(INK4a), bcl-2, p53 and Ki-67 in tissue microarray blocks containing 20 samples each of normal cervix, moderate-to-severe cervical dysplasia (CIN II-III) and invasive SCC. Samples are derived from 60 total cases of cervical biopsies and cervical conizations. Results showed that the proliferation marker, Ki-67, is markedly increased, and the senescence markers, p15(INK4b), p16(INK4a) and p14(ARF) are overexpressed in both dysplasia and carcinoma. P53 immunostain is negative in all normal cervical tissue, and positive in dysplasia and carcinoma. Although the expression of bcl-2 is increased in dysplasia, this marker is negative in approximately half of SCC cases. These results suggest that some senescence pathways are activated and are still maintained in cervical dysplasia and carcinoma. However proliferation is increased and carcinogenesis is not thwarted, leading to eventual development of cervical cancer. Other mechanisms, such as those that account for the apparent overexpression of p53 and paradoxical loss of bcl-2 expression in some SCC cases, as well as additional senescence and apoptotic pathways, may play key roles carcinogenesis of cervical SCC.

Expression of p14ARF, p15INK4b, p16INK4a, and DCR2 increases during prostate cancer progression

Prostate carcinoma is a hormonally driven age-related neoplasm. Cellular senescence is an age-related process where cells remain metabolically active but in a growth-arrested state at the G1 phase. p14(ARF), p15(INK4b), and p16(INK4a), which are known to regulate G1 cell cycle arrest, and the tumor necrosis factor receptor superfamily member decoy receptor 2 (DCR2), have been recently identified as senescence markers. The purpose of this study was to characterize and compare the expression of p14(ARF), p15(INK4b), p16(INK4a), and DCR2 in tissue microarrays containing cases of normal prostate, nodular hyperplasia, prostate intraepithelial neoplasia (PIN), and malignant prostate cancer tissue. We performed immunohistochemical staining for p14(ARF), p15(INK4b), p16(INK4a), and DCR2 in tissue microarray blocks containing 41 cores of normal prostate, 65 cores of nodular hyperplasia, 21 cores of PIN, 69 cores of low-grade prostate carcinoma, and 42 cores of high-grade prostate carcinoma, derived from 80 cases of prostatectomy with adenocarcinomas. We detected positive staining of p16(INK4a) in 19% of the PIN, 25% of the low-grade carcinoma, and 43% of the high-grade carcinoma specimens but none in the normal prostate and nodular hyperplasia specimens. Expression of p14(ARF) revealed very high levels of expression in normal tissues (83%), nodular hyperplasia (88%), PIN (89%), and cancer cells (100%). P15(INK4b) and DCR2 were found positive in 81 and 33% normal, 46 and 10% nodular hyperplasia, 74 and 36% PIN tissues, 87 and 89% low-grade carcinomas, and 100 and 93% high-grade carcinomas. There is an increased protein expression of senescence-associated molecular markers, indicating that cellular senescence might play a role in prostate carcinoma. Because p16(INK4a)-positive cells were detected only in premalignant lesions and carcinomas but not in normal or benign tissues, p16(INK4a) may aid in the diagnosis of PIN and prostate cancer in difficult cases.

Persistent infection of hepatitis B virus is involved in high rate of p16 methylation in hepatocellular carcinoma

High rate of chronic hepatitis B virus (HBV) infection and p16 promoter methylation were found in the majority of hepatocellular carcinoma (HCC). To investigate the potential linkage between high rate of p16 methylation and HBV infection, p16 methylation was detected with methylation-specific polymerase chain reaction (PCR), and HBV markers were examined with real-time PCR and immunologic method. p16 methylation was detected in 5.5% of patients with hepatitis B, 9.1% of noncancerous liver, 36.6% of cirrhotic liver tissue, and 70.5% of cancerous tissue of HCC, primarily in cirrhotic (46.7%) and cancerous tissue (90.6%) with HBV infection. In noncancerous tissue, p16 methylation could only be detected in samples with HBV infection, although no significant difference, the frequency of p16 methylation in noncancerous tissue with HBV infection was higher than those without it. The results showed that, in cancerous, cirrhotic, or noncancerous tissues, the frequency of p16 methylation in samples with HBV infection was higher than those without it, suggesting possible association between HBV infection and p16 methylation. The result of HBV-DNA analysis showed that 96.1% (49/51) samples with p16 methylation also showed detectable HBV-DNA; it signifies that replication and/or integration of HBV may contribute to high rate of p16 methylation in hepatocarcinogenesis. Generally, these results indicate that persistent HBV infection may be associated with high rate of p16 methylation, and involved in development of HCC through this way.

Genetics of hepatocellular tumors

Numerous genetic alterations are accumulated during the process of hepatocarcinogenesis. These genetic alterations can be divided into two groups. The first set of genetic alterations is specific of hepatocellular tumor risk factors. It includes integration of hepatitis B virus (HBV) DNA, R249S TP53 (tumor protein p53) mutation in aflatoxin B1-exposed patients, KRAS mutations related to vinyl chloride exposure, hepatocyte nuclear factor 1alpha (HNF1alpha) mutations associated to hepatocellular adenomas and adenomatosis polyposis coli (APC) germline mutations predisposing to hepatoblastomas. The second set of genetic alterations are etiological nonspecific, it includes recurrent gains and losses of chromosomes, alteration of TP53 gene, activation of WNT/beta-catenin pathway through CTNNB1/beta-catenin and AXIN (axis inhibition protein) mutations, inactivation of retinoblastoma and IGF2R (insulin-like growth factor 2 receptor) pathways through inactivation of RB1 (retinoblastoma 1), P16 and IGF2R. Comprehensive analyses of these genetic alterations have defined two pathways of hepatocarcinogenesis according to the presence or the absence of chromosomal instability. Hepatitis B virus and poorly differentiated tumors are related to chromosome instable tumors associated with frequent TP53 mutations, whereas non-HBV and well-differentiated tumors are related to chromosomal stable samples that are frequently beta-catenin activated. These classifications have clinical relevance as genetic alterations may also be related to prognosis.

Arsenic trioxide inhibits DNA methyltransferase and restores methylation-silenced genes in human liver cancer cells

In the present study, we investigated methylation status of the CpG islands of some major tumor suppressor genes both in human hepatocellular carcinoma and liver cancer cell lines and examined whether demethylation by arsenic trioxide (As2O3) could restore their expression in the cell lines. HepG2 and Huh-7 cells were treated with 2 to 10 micromol/L of AS2O3 and/or 1 micromol/L of 5-aza-2'-deoxycytidine for 24, 48, and 72 hours. The methylation status of the CpG island around the promoter regions of p161NK4a, RASSF1A, E cadherin, and GSTP1 was detected by a methylation-specific polymerase chain reaction (MSP). The messenger RNA (mRNA) and protein levels of these genes were determined by quantitative real-time reverse transcriptase-polymerase chain reaction, Western blot, and immunohistochemical analyses. The DNA methyltransferase (DNMT) mRNA levels and enzyme activity were also examined. The hypermethylated status of the promoter regions of p16INK4a, RASSF1A, E cadherin, and GSTP1 was observed in 10 (40%), 14 (56%), 6 (24%), and 12 (48%) of 25 patients with hepatocellular carcinoma, respectively. CpG methylation of the p16INK4a, RASSF1A, E cadherin, and GSTP1 genes was correlated to the reduction of mRNA levels in the cell lines, and mRNA expression of these 4 genes were indeed restored by low concentrations (2-6 micromol/L) of As2O3 through demethylation, as well as 1 micromol/L of 5-aza-2'-deoxycytidine. Western blot and immunohistochemical analyses confirmed that each protein was markedly enhanced after treatment with a low concentration of As2O3. In contrast, As2O3 at a high concentration (10 micromol/L) damaged cell membranes and remarkably suppressed these 4 protein levels. As2O3 decreased the mRNA expression of DNMT 1 and also dose-dependently inhibited DNMT activity. In conclusion, a low concentration of As2O3 induces CpG island demethylation of tumor suppressor genes by inhibition of DNMT and reactivates the partially/fully silenced genes in liver cancer cells.

Methylation status of p14ARF, p15INK4b, and p16INK4a genes in human hepatocellular carcinoma

BACKGROUND

The INK4 locus consisting of three genes involved in the regulation of cell cycle, p16INK4a, p15INK4b, and p14ARF is often disrupted in human neoplasms.

METHODS

We analyzed the promoter methylation of each gene by methylation-specific PCR in hepatocellular carcinoma (HCC).

RESULTS

The methylation of p16INK4a, p15INK4b, and p14ARF was found to occur in 27 (69.2%), seven (17.9%), and none out of 39 HCC tumors, respectively. Regarding corresponding nontumorous liver tissues, the promoter regions of p16INK4a, p15INK4b, and p14ARF were methylated in three (17.6%), three (17.6%), and none out of 17 samples, respectively. Analysis of mRNA expression revealed that loss of p16INK4a expression was frequently observed in HCC. In contrast, transcripts of p14ARF and p15INK4b were detected in 16 (88.9%) and 16 (88.9%) of 18 tumors, respectively.

CONCLUSIONS

The frequent loss of transcription of p16INK4a with promoter methylation not only in the advanced but also in the early stages of HCC suggests that the epigenetic alteration of p16INK4a promoter is likely to be involved in hepatocarcinogenesis. Together with the result of RT-PCR analysis, the role of aberrant methylation of p14ARF or p15INK4a promoter in hepatocarcinogenesis is thought to be limited.

Cell biological evaluation of liver cell carcinoma, dysplasia and adenoma by tissue micro-array analysis

The clinical and morphological definition of hepatocellular carcinoma (HCC), dysplasia and adenoma suffers from a lack of biological understanding. This is especially important in the histomorphological diagnosis of nodular liver lesions in needle biopsies. Therefore, we constructed a liver tissue micro-array (TMA) and evaluated 48 HCCs, 46 dysplasias, 8 adenomas, 20 cirrhotic specimens and 28 normal liver samples derived from 68 patients. Protein (over)expression by tumor suppressor genes p16, p53 and Rb1 was assessed by immunohistochemistry, the proliferative capacity was examined by immunostaining of Ki67. Further, DNA ploidy status (hyperdiploidy) was measured by fluorescent in situ hybridization (FISH) with a chromosome 1-specific repetitive DNA probe. An abnormal chromosome 1 number, i.e. the percentage of hyperdiploid cells, was 11.0, 13.7, 16.1, 23.7 and 31.3 for normal liver samples, adenomas, cirrhosis, dysplasias and HCCs, respectively. A significant difference was found for HCC versus cirrhosis (P = 0.024) or adenoma (P = 0.033), a trend (borderline significance) was seen for dysplasia versus cirrhosis (P = 0.094). Immunohistochemical protein localisation of p53 and Rb1, as well as Ki67 indicating proliferation, was clearly higher in HCC than in cirrhosis or dysplasia (all P < 0.001). Proliferation was also higher in HCC than in adenoma (P = 0.025), whereas a trend (borderline significance) was observed for Rb1 overexpression (P = 0.063). These data suggest that in the liver cell dysplasia-carcinoma pathway, changes in ploidy are followed by increased proliferation and cell biological perturbations involving p53 and Rb1. Adenomas can be distinguished from carcinomas, but not from dysplasias, based on ploidy and proliferation characteristics.

Effect of Promoter Methylation of the p16 Gene on Phosphorylation of Retinoblastoma Gene Product and Growth of Hepatocellular Carcinoma Cells

The biological significance of hypermethylation of p16 gene promoter in human hepatocellular carcinoma (HCC) cells remains to resolved. In order to clarify the significance of methylation of p16 gene promoter, we examined the methylation status of p16 gene in association with phosphorylation of retinoblastoma gene product (pRb) and cell growth in human HCC cell lines. The presence of methylation was examined by methylation-specific PCR. Expression and phosphorylation of p16 and pRb were examined by Western blot analysis. Genetic changes were analyzed by multiplex PCR and DNA sequencing. The effect of demethylation of p16 was assessed by cell growth. p16 gene promoter was methylated in HuH7 and HLF cells. The demethylating agent, 5-aza-2-deoxycytidine (5-Aza-CdR), upregulated p16 mRNA in HuH6 and HuH7 cells. 5-Aza-CdR increased p16 protein expression in HuH6, HuH7, and HLF cells, and it clearly decreased the phosphorylation level of pRb in HuH6, HuH7 and PLC/PRF/5 cells. Treatment with 5-Aza-CdR inhibited the growth of HuH7 cells. Homozygous deletion and significant mutations were absent. Methylation in the p16 promoter region is biologically significant, being associated with phosphorylation of pRb and cell growth in human HCC cells.

Analysis of p16INK4A gene promoter in male germ-cell tumors: identification of a new point mutation

Human male germ-cell tumors of seminoma type display aberrant expression of INK4-family inhibitors of the cell cycle including CDKN2-encoded p16INK4A. The mechanisms underlying the altered p16INK4A expression are not fully understood. Indeed, neither genetic/epigenetic alterations in CDKN2 coding sequence nor its promoter hypermethylation could explain all anomalies. To assess whether the aberrant p16INK4A expression could be related to the alterations in CDKN2 regulatory sequence, we screened seminoma DNAs from 19 patients for the promoter mutations. Combined polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and automated DNA-sequencing approaches indicated an adenine insertion at the position-1973 (relative to the ATG codon at+1) of CDKN2 promoter in one particular patient. The immunohistochemical analysis pointed to the correlation between the observed promoter mutation and the loss of p16INK4A protein expression. These data suggest that in addition to previously characterized anomalies, the identified CDKN2 promoter mutation may be relevant for altered p16INK4A protein expressions in at least some seminoma.

p16INK4A Hypermethylation Is Associated with Hepatitis Virus Infection, Age, and Gender in Hepatocellular Carcinoma

Purpose: The tumor suppressor gene p16INK4A is mainly inactivated by an epigenetic change involving promoter hypermethylation in hepatocarcinogenesis. The possible clinical impact of p16INK4A methylation and the potential risk factors for this epigenetic alteration have not been thoroughly investigated.

Experimental Design: We studied the methylation status and mRNA and protein expression of p16INK4A in 50 hepatocellular carcinomas and corresponding nonneoplastic liver lesions using methylation-specific PCR, reverse transcription-PCR, and immunohistochemical techniques.

Results: p16INK4A hypermethylation was observed in 58% (29 of 50) of the hepatocellular carcinomas and 16% (6 of 38) of the corresponding chronic hepatitis and cirrhosis tissue samples. p16INK4A methylation was significantly associated with mRNA and protein expression (P &lt; 0.001 and P = 0.003, respectively). All of the p16INK4A-methylated tumors were positive for hepatitis B virus or hepatitis C virus markers, but none of the virus-negative tumors exhibited p16INK4A methylation (P = 0.006). The frequency of p16INK4A hypermethylation tended to be higher in hepatitis C virus-related tumors (23 of 32, 72%) than in hepatitis B virus-related tumors (6 of 13, 46%; P = 0.1). Aberrant methylation of p16INK4A was also related significantly to increasing age, female gender, and normal levels of serum PIVKA-II (P = 0.02, 0.04, and 0.04, respectively). No statistically significant difference in survival was observed between patients with p16INK4A hypermethylation and those without.

Conclusions: Our observations suggest that p16INK4A hypermethylation may contribute to hepatocarcinogenesis from an early stage and that multiple risk factors, such as viral infections, age, and gender, may be associated with p16INK4A hypermethylation in hepatocarcinogenesis.

p16INK4A gene alterations are not a prognostic indicator for survival in patients with hepatocellular carcinoma undergoing curative hepatectomy

BACKGROUND AND AIM

Hepatocellular carcinoma (HCC) is a common malignancy worldwide that is highly associated with chronic hepatitis B or C infection and cirrhosis. The tumor suppressor gene p16INK4A is an important component of the cell cycle and inactivation of the gene has been found in a variety of human cancers. The present study was performed to determine genetic and epigenetic alterations in the p16INK4A tumor suppressor gene and the effect of these on HCC progression.

METHODS

The status of p16INK4A was evaluated in 117 HCC tumoral nodules and 110 corresponding peritumoral tissues by loss of heterozigosity (LOH) at the 9p21-22 region, homozygous deletions, single-strand conformation polymorphism-polymerase chain reaction (PCR) mutational analysis and methylation specific PCR.

RESULTS

The most frequent inactivation mechanism was hypermethylation of the promoter region, which was found in 63.2% of the tumor samples and in 28.2% of the peritumoral samples. Loss of heterozygosity at the 9p21 region was detected in 27.3% and 10% of tumor and peritumoral tissues, respectively. Homozygous deletions and mutations were less common events in hepatocarcinogenesis. The authors found 5.9% of the tumor cases with exon 2 homozygous deletions and 8.6% with mutations. Two polymorphisms were detected, one at codon 148 (GCG --> ACG, Ala --> Thr) in three cases and the other in exon 3 at 540 bp (34.2% of the samples). No association was found between inactivation of p16INK4A and clinicopathological characteristics or prognosis.

CONCLUSION

p16INK4A is altered frequently and early in HCC, being the predominant mechanism of inactivation promoter hypermethylation. The present results suggest that the p16INK4A gene plays an important role in the pathogenesis of HCC.