Promoter Hypermethylation of the p16 Gene Is Associated with Poor Prognosis in Recurrent Early-Stage Hepatocellular Carcinoma

A Study of Prognostic Factors in Young Patients With Non-HPV Oral Cancer in Central Europe

The etiological factors of squamous cell carcinomas of the head and neck have been well known for a long time. It is also well known that the incidence of oral cancer diagnosed in younger patients is on the rise. Due to the young age of these patients, the increase in the number of these cases and the fact that many of them neither smoke nor drink alcohol it has been suggested that other factors might be at play in the carcinogenesis of oral cancer. Thus, along the classic etiological factors of smoking and alcohol abuse certain molecular marker anomalies and the human papilloma virus (HPV) have emerged as potential factors. The aim of the present study is to verify the potential prognostic factors and to map the differences in biomarker expression between the young and the old patient groups. In the present study the immunohistochemical profile of samples obtained from oral squamous cell carcinomas was studied and compared with various clinico-pathological parameters. In 88 samples the expressions of p16, p53, Ki67, EGFR were studied with a tissue microarray technique under standard reaction conditions as well as the detection and typing of HPV infection with the Full Spectrum HPV DNA method. The biomarker expression profile of young patients with oral squamous cell carcinoma was compared to that of older patients (above 50). A significant difference was found between the immunohistochemical profile of the young and old patient groups in p16, Ki67 expression. The overall survival and progression free survival were influenced by p16 expression in young age.

Current and Emerging Tools for Hepatocellular Carcinoma Surveillance

Hepatocellular carcinoma (HCC) is a leading cause of cancer‐related mortality worldwide. Early detection of HCC enables patients to avail curative therapies that can improve patient survival. Current international guidelines advocate for the enrollment of patients at high risk for HCC, like those with cirrhosis, in surveillance programs that perform ultrasound every 6 months. In recent years, many studies have further characterized the utility of established screening strategies and have introduced new promising tools for HCC surveillance. In this review, we provide an overview of the most promising new imaging modalities and biomarkers for the detection of HCC. We discuss the role of imaging tools like ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) in the early detection of HCC, and describe recent innovations which can potentially enhance their applicability, including contrast enhanced ultrasound, low‐dose CT scans, and abbreviated MRI. Next, we outline the data supporting the use of three circulating biomarkers (i.e., alpha‐fetoprotein [AFP], AFP lens culinaris agglutinin‐reactive fraction, and des‐gamma‐carboxy prothrombin) in HCC surveillance, and expand on multiple emerging liquid biopsy biomarkers, including methylated cell‐free DNA (cfDNA), cfDNA mutations, extracellular vesicles, and circulating tumor cells. These promising new imaging modalities and biomarkers have the potential to improve early detection, and thus improve survival, in patients with HCC.

Detection of Circulating Antibodies to p16 Protein-Derived Peptides in Hepatocellular Carcinoma

OBJECTIVE

This study aimed at confirming the alteration of circulating anti-p16 immunoglobulin G (IgG) levels in hepatocellular carcinoma (HCC).

METHODS

An in-house-developed enzyme-linked immunosorbent assay was used for determining plasma IgG antibodies against p16-derived antigens in 122 HCC patients and 134 healthy controls.

RESULTS

Plasma anti-p16 IgG levels were significantly higher in HCC patients than in the controls (Z = 3.51, P = 0.0004), with no difference between males and females. A trend of increasing plasma anti-p16 IgG levels was associated with increasing HCC stage, with group 3 patients having the highest anti-p16 IgG levels (Z = 3.38, P = 0.0008). Group 3 exhibited the best sensitivity (19.6%) and specificity (95%) for plasma anti-p16 IgG detection, with an area under the receiver operating characteristic curve of 0.659 (95% confidence interval, 0.564-0.754).

CONCLUSION

Circulating IgG antibody to p16 protein might be a useful biomarker for HCC prognosis assessment rather than for early malignancy diagnosis.

Oncogene PLCE1 may be a diagnostic biomarker and prognostic biomarker by influencing cell cycle, proliferation, migration, and invasion ability in hepatocellular carcinoma cell lines

Hepatocellular carcinoma (HCC) is a lethal malignancy worldwide. HCC has traits of late diagnosis and high recurrence. This study explored potential diagnosis and prognosis significance of phospholipase C epsilon 1 (PLCE1) in HCC. The messenger RNA (mRNA) levels and diagnostic value of PLCE1 were determined by real-time polymerase chain reaction and online databases GEPIA, oncomine, and GSE14520 data set. Survival analysis used the Kaplan-Meier Plotter website. Cell cycle, proliferation, migration, and invasion assays were performed with downregulated PLCE1 expression in HCC-M and HepG2 cell lines. PLCE1 was differentially expressed and highly expressed in tumors and had low expression in nontumor tissues (all p < .05). The diagnostic value of PLCE1 was validated with the datasets (all p < .01, all areas under curves > 0.7). PLCE1 mRNA expression was associated with the overall and relapse-free survival (both p < .05). Functional experiments indicated that downregulation of PLCE1 expression led to increased G1 stage in cell cycle and decreased cell proliferation, migration, and invasion compared with a negative control group (all p ≤ .05). The oncogene PLCE1 was differentially expressed in HCC and non-HCC tissues. It is a candidate for diagnosis and serves as prognosis biomarker. PLCE1 influenced survival by affecting the cell cycle, proliferation, migration, and invasion ability.

Epigenomic biomarkers for prognostication and diagnosis of gastrointestinal cancers

Altered epigenetic regulation is central to many human diseases, including cancer. Over the past two decade, major advances have been made in our understanding of the role of epigenetic alterations in carcinogenesis, particularly for DNA methylation, histone modifications and non-coding RNAs. Aberrant hypermethylation of DNA at CpG islands is a well-established phenomenon that mediates transcriptional silencing of tumor suppressor genes, and it is an early event integral to gastrointestinal cancer development. As such, detection of aberrant DNA methylation is being developed as biomarkers for prognostic and diagnostic purposes in gastrointestinal cancers. Diverse tissue types are suitable for the analyses of methylated DNA, such as tumor tissues, blood, plasma, and stool, and some of these markers are already utilized in the clinical setting. Recent advances in the genome-wide epigenomic approaches are enabling the comprehensive mapping of the cancer methylome, thus providing new avenues for mining novel biomarkers for disease prognosis and diagnosis. Here, we review the current knowledge on DNA methylation biomarkers for the prognostication and non-invasive diagnosis of gastrointestinal cancers and highlight their clinical application.

Application of multiplex methylated-specific PCR with capillary electrophoresis to explore prognostic value of TSGs hypermethylation for hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is a malignant tumor that severely threatens human health. To date, early detection for HCC patients is particularly significant due to their poor survival rates even after liver resection.

METHODS

Therefore, an efficient and sensitive detection method for monitoring liver cancer, multiplex methylation-specific PCR (MSP) coupled with capillary electrophoresis, is developed.

RESULTS

Simulations demonstrated that the methylation status of RASSF1A, p16, SFRP1, and ELF could be detected even when DNA equaled or exceeded 12.5 ng simultaneously. Also, its accuracy for methylation detection outweighed polyacrylamide gel electrophoresis (87.5%) and agarose electrophoresis (84.3%), reaching 92.1%. Subsequently, we implemented multiplex MSP with capillary electrophoresis to investigate methylation status of the four tumor suppressor genes in tissue specimens and explore the prognostic value for HCC patients. As the data suggested, multivariate cox regression analysis revealed that the recurrence-free survival of 46 patients was greatly associated with portal vein tumor thrombus (PVTT) and p16 methylation and receiver operating characteristic (ROC) curves demonstrated that the predictive range of portal vein tumor thrombus (PVTT) combined with p16 hypermethylation was more sensitive than that of either PVTT or p16 hypermethylation alone with regard to disease recurrence in patients with HCC, which could be testified as a valuable biomarker in Clinical application.

CONCLUSION

Multiplex MSP coupled with capillary electrophoresis has an excellent prospect of clinical application for monitoring early liver cancer and screening valuable biomarkers for prognosis of HCC patients.

Expression of the tumor suppressor gene p16, and lymph node metastasis in patients with ovarian cancer

This study examined the relationship between the expression of p16, a tumor suppressor gene, and lymph node metastasis, as well as patient prognosis, in cases with ovarian cancer. SKOV-3, an ovarian cancer cell line, and IOSE80, a normal human ovarian cell line, were selected for testing. Western blot analysis was used to detect the p16 expression in ovarian cell culture samples. In the study, 20 cases with normal ovarian tissue and 64 cases with ovarian cancer tissue, including 38 cases with lymph node metastasis and 26 cases without lymph node metastasis, were also selected for testing. Immunohistochemical techniques were used to detect the expression of p16 protein in ovarian tissue samples. The influence of p16 protein on SKOV-3 cell invasion ability was studied using p16 gene high-expression vector transfection. Clinical and prognosis data were summarized and the influence of p16 on patient prognosis was analyzed through Kaplan-Meier single-factor survival analysis. The results showed that p16 expression in SKOV-3 was decreased significantly compared with that in IOSE80. The positive rate of p16 protein expression in ovarian cancer tissue was notably decreased compared with that in normal ovarian tissue. The positive rate of p16 protein expression in ovarian cancer tissue of patients with lymph node metastasis was significantly decreased compared with that of patients without lymph node metastasis. Therefore, transfection of the p16 gene significantly inhibited the protein expression and invasion ability of p16 in SKOV-3. Correlation analyses between p16 and survival prognosis demonstrated that lower expression of p16 was negatively correlated with the prognosis of patients with ovarian cancer. Overall, the abnormal expression of p16 in ovarian cancer is associated with an increased invasion ability of ovarian cancer and the lower expression of p16 in tissue samples indicates a poor prognosis in patients with ovarian cancer.

High expression of long non-coding RNA ZEB1-AS1 promotes colorectal cancer cell proliferation partially by suppressing p15 expression

This study aims to investigate the function of long non-coding RNA ZEB1-AS1, reveal its molecular mechanism in colorectal cancer cell growth, and evaluate its clinical significance in colorectal cancer patients. ZEB1-AS1 has reported in the development of several cancers, but the biological role of it in colorectal cancer has not been discussed. In this report, ZEB1-AS1 expression level was measured with quantitative real-time polymerase chain reaction in 63 pairs of colorectal cancer tissues and paired adjacent non-tumor colorectal tissues. The relationship between ZEB1-AS1 expression and overall survival was analyzed by virtue of Kaplan-Meier analysis. Subsequently, small interfering RNA or lentivirus vector-mediated lncRNA ZEB1-AS1 was transfected into colorectal cancer cell lines. Cell viability and apoptosis were examined. Later, nude mouse transplantation experiment was conducted to evaluate the effect of ZEB1-AS1 on colorectal cancer development in vivo. It turns out that ZEB1-AS1 is upregulated in colorectal cancer tissues and its expression is significantly associated with overall survival rate and recurrence-free survival. Upregulation of ZEB1-AS1 colorectal cancer promotes cell proliferation and inhibits cell apoptosis. In addition, cell cycle inhibitory protein p15 participates in the oncogenic function of ZEB1-AS1. Collectively, ZEB1-AS1 has asignificant effect on colorectal cancer pathological process and serves as a valuable prognostic biomarker for colorectal cancer.

Meta-analysis of possible role of cadherin gene methylation in evolution and prognosis of hepatocellular carcinoma with a PRISMA guideline

BACKGROUND

Cadherins (CDHs) have been reported to be associated with cancer. However, the clinical significance of CDH gene methylation in hepatocellular carcinoma (HCC) remains unclear.

METHODS

Based on the preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement criteria, available studies were identified from online electronic database. The overall odds ratio (OR) and the corresponding 95% confidence interval (95% CI) were calculated and analyzed.

RESULTS

A total of 29 eligible studies with 2562 HCC samples and 1685 controls were included. E-cadherin (CDH1) hypermethylation was observed to be significantly higher in HCC than in benign, adjacent, or normal samples. Moreover, CDH1 hypermethylation was not associated with gender, tumor grade, clinical stage, hepatitis B virus (HBV), or hepatitis C virus (HCV) infection in HCC patients. H-cadherin (CDH13), protocadherin-10 (PCDH10), P-cadherin (CDH3), and M-cadherin (CDH15) methylation may have an increased risk of HCC in fewer than 4 studies, and methylated cadherin 8, type 2 (CDH8) and OB-cadherin (CDH11) had a similar OR in HCC and adjacent samples. When HCC samples were compared with normal samples, the analysis of sample type revealed a significantly higher OR in normal blood samples than in normal tissues for hypermethylated CDH1 (50.82 vs 4.44).

CONCLUSION

CDH1 hypermethylation may play a key role in the carcinogenesis of HCC. However, CDH1 hypermethylation was not correlated with clinicopathological features. Methylated CDH13, PCDH10, CDH3, and CDH15, but not methylated CDH8 or CDH11, may lead to an increased risk of HCC. Hypermethylated CDH1 may become a noninvasive blood biomarker. Further studies with more data are necessary.

The Correlation Relationship between P14ARF Gene DNA Methylation and Primary Liver Cancer

Background

Primary liver cancer is a common malignant tumor that causes serious damage to human health. DNA methylation is common in epigenetics. DNA methylation plays an important role in the process of primary liver cancer occurrence and development. The P14^ARF gene is an important tumor suppressor gene. It was found that P14^ARF methylation is associated with the degree of malignancy in multiple tumors. Therefore, this study aimed to investigate the relationship between P14^ARF methylation level and primary liver cancer malignant degree.

Material/Methods

Carcinoma tissues and adjacent tissues were collected from 87 primary liver cancer patients. Pyrosequencing was applied to obtain P14^ARF methylation. Real-time PCR was used to detect P14^ARF mRNA level.

Results

P14^ARF methylation level in cancerous tissue was significantly higher than in the adjacent tissue (t=76.54, P<0.001). P14^ARF methylation showed no significant difference in patients with different age, sex, smoking status, or drinking status. It did not present an obvious difference in tumors with different size. Its methylation level increased following the improvement of TNM stage (P<0.05). Compared with the adjacent tissue, P14^ARF mRNA in carcinoma tissue decreased by 31% (t=28.91, P<0.001). P14^ARF methylation showed a significant negative correlation with mRNA expression in cancerous tissue (r=−0.43, P<0.01).

Conclusions

P14^ARF mRNA level is regulated by DNA methylation in primary liver cancer. P14^ARF gene DNA methylation may be associated with the occurrence of primary liver cancer occurrence and TNM staging.

DNA methylation: potential biomarker in Hepatocellular Carcinoma

Hepatocellular Carcinoma (HCC) is one of the most common cancers in the world and it is often associated with poor prognosis. Liver transplantation and resection are two currently available curative therapies. However, most patients cannot be treated with such therapies due to late diagnosis. This underscores the urgent need to identify potential markers that ensure early diagnosis of HCC. As more evidences are suggesting that epigenetic changes contribute hepatocarcinogenesis, DNA methylation was poised as one promising biomarker. Indeed, genome wide profiling reveals that aberrant methylation is frequent event in HCC. Many studies showed that differentially methylated genes and CpG island methylator phenotype (CIMP) status in HCC were associated with clinicopathological data. Some commonly studied hypermethylated genes include p16, SOCS1, GSTP1 and CDH1. In addition, studies have also revealed that methylation markers could be detected in patient blood samples and associated with poor prognosis of the disease. Undeniably, increasing number of methylation markers are being discovered through high throughput genome wide data in recent years. Proper and systematic validation of these candidate markers in prospective cohort is required so that their actual prognostication and surveillance value could be accurately determined. It is hope that in near future, methylation marker could be translate into clinical use, where patients at risk could be diagnosed early and that the progression of disease could be more correctly assessed.

Metastasis-related miR-185 is a potential prognostic biomarker for hepatocellular carcinoma in early stage

We previously reported that miR-185 is associated with hepatocellular carcinoma (HCC) venous metastasis analysed by miRNA-array profile. The aim of this study is to further investigate the clinicopathological significance and prognostic value of miR-185 in early stage HCC. We classified 95 patients with early stage HCC into treated recurrence group (TR) and none treated recurrence group (NTR), and detected the miR-185 expression levels in TR and NTR groups. We found that low miR-185 expression correlated with more tumor recurrence (37/46), while high miR-185 level led to lower recurrence rate (17/49) (P<0.05). There was no direct relationship between miR-185 and clinicopathological features, including age, gender, ALT, AFP, liver cirrhosis, tumor size, tumor encapsulation, tumor differentiation (P>0.05). Kaplan-Meier analysis showed that low miR-185 group had a remarkable lower survival rate and shorter time to recurrence than high miR-185 group (P<0.05). Univariate and multivariate analysis, using Cox's proportional hazards model, also indicated that low miR-185 expression was a sensitive prognostic factor for survival and recurrence in early stage HCC (P<0.05). We upregulated or downregulated miR-185 expression by transfected miR-185 mimics or inhibitor into HCC cell lines, and observed the influence of miR-185 on HCC cells in vitro. Our results manifested that miR-185 could suppress the tumor cell growth and invasive ability (P<0.05). Therefore, miR-185 might be an effective and sensitive biomarker of HCC in early stage, and the upregulation of miR-185 might be considered to be a potentially important molecular treatment strategy for patients with HCC.

Folate malabsorption and its influence on DNA methylation during cancer development

The folate transport across the epithelial of the intestine, colon, kidney, and liver is essential for folate homeostasis. The relative localization of transporters in membranes is an important determinant for the vectorial flow of substrates across the epithelia. Folate deficiency is a highly prevalent vitamin deficiency in the world, and alcohol ingestion has been the major contributor. It can develop because of folate malabsorption in tissues, increased renal excretion dietary inadequacy, and altered hepatobiliary metabolism. Additionally, folate-mediated one-carbon metabolism is important for various cellular processes, including DNA synthesis and methylation. In this regard, the contribution of alcohol-associated and dietary folate deficiency to methylation patterns is under intense investigation, especially in cancer. The epigenetic events have increasing relevance in the development of strategies for early diagnosis, prevention, and treatment of cancer.

Promoter methylation and loss of p16(INK4a) gene expression in head and neck cancer

BACKGROUND

Silencing of tumor suppressor genes plays a vital role in head and neck carcinogenesis. In this study we aimed to evaluate aberrant p16(INK4a) gene promoter methylation in patients with head and neck cancer.

METHODS

Methylation of the gene was investigated by bisulfite modification/methylation-specific polymerase chain reaction and gene expression levels were analyzed by quantitative reverse transcription-polymerase chain reaction in tumors and matched normal tissue samples from Turkish patients with head and neck cancer.

RESULTS

The promoter region of the p16(INK4a) gene was methylated in 67.5% and 28.6% of the primary tumors and the corresponding normal tissue, respectively. This difference was highly significant. In concordance, p16(INK4a) gene expression was downregulated in 67.5% of the tumor samples. Methylation and the absence of expression in the tumors were observed in 48% of the patients.

CONCLUSIONS

Our data indicate that methylation of the p16(INK4a) gene is a frequent event in primary head and neck cancer and that it plays a major role in the silencing of p16(INK4a) gene expression during tumor development.

Epigenetics, development, and cancer: zebrafish make their mark

Zebrafish embryos are an exceptional system for studying vertebrate development. Historically, studies using zebrafish to uncover key players in developmentally regulated gene expression have entailed detailed analysis of transcription factors. It is now apparent that epigenetic modifications of both DNA and histone tails are equally important in the regulation of gene expression during development. As such, blocking the function of key epigenetic modifiers impairs development, albeit with surprising tissue specificity. For instance, DNA methylation is an important epigenetic mark that is depleted in embryos lacking dnmt1 and uhrf1. These embryos display developmental defects in the eye, liver, pancreas, and larval lethality. Interestingly, human tumors derived from these same organs have aberrant changes in DNA methylation and altered expression of genes that are thought to contribute to formation of these cancers. These observations have provided a mechanistic basis for treating cancer with drugs that block the enzymes that facilitate DNA and histone modifications. Thus, it is important to understand the consequences of targeting these factors in a whole animal. We review the use of zebrafish for probing the genetic, cellular, and physiological response to alterations in the epigenome and highlight exciting data illustrating that epigenetic studies using zebrafish can inform and impact cancer biology.

Comparative analysis of promoter methylation and gene expression endpoints between tumorous and non-tumorous tissues from HCV-positive patients with hepatocellular carcinoma

Transcriptional silencing of tumor suppressor genes and other cancer-related genes induced by promoter CpG island hypermethylation is an important epigenetic mechanism of hepatocarcinogenesis. Previous studies have established methylation profiles of hepatocellular carcinomas (HCCs) and demonstrated that methylation of several candidate genes in resected tissues may be associated with time to recurrence. The goals of our study were to test whether specific promoter methylation and mRNA levels of candidate genes, as well as global changes in DNA methylation, can be linked with time to recurrence and clinicopathological variables in a homogenous study group of HCC patients. Forty-three tumorous and 45 non-tumorous liver tissue samples from the surgical margin were obtained from HCV-positive, HBV-negative HCC patients who underwent tumor resection surgery and who were monitored for tumor recurrence thereafter (median follow-up time: 16 months (range, 0-79 months)). Methylation-specific PCR was used to assess the promoter methylation status of P16(INK4a), SOCS-1, RASSF1A, APC, GSTP1, RIZ1, and MGMT genes, while the level of LINE-1 methylation was used as marker of global DNA methylation levels. Methylation frequencies in P16(INK4a), RASSF1A, APC, GSTP1, and RIZ1 genes were significantly greater in tumorous versus non-tumorous tissues. Methylation of RIZ1 in non-tumorous tissues was significantly associated with time to recurrence. Additionally, genomic DNA was significantly more hypomethylated in tumorous tissues, and this change was associated with shorter recurrence, but not with clinicopathological features. In conclusion, this study supports the role of aberrant methylation in the pathobiology of HCV-positive HCCs. The finding that RIZ1 methylation and increased levels of LINE-1 hypomethylation in non-tumorous tissues are associated with time to recurrence underscores the importance of assessing the epigenetic state of the liver remnant.

CpG island methylator phenotype associated with tumor recurrence in tumor-node-metastasis stage I hepatocellular carcinoma

BACKGROUND

CpG island methylator phenotype (CIMP), characterized by simultaneous methylation of multiple tumor suppressor genes (TSGs), has been reported to be associated with biological malignancy in many cancers. Whether CIMP is potentially predictive of clinical outcome in hepatocellular carcinoma (HCC) remains unknown.

METHODS

We investigated the methylation status of ten TSGs and CIMP in 115 samples of HCC and 48 samples of corresponding nonneoplastic liver tissues using a methylation-specific polymerase chain reaction.

RESULTS

The methylation frequencies of the ten genes examined in HCC were 40.0% for p14 ( ARF ), 60.9% for p15 ( INK4b ), 70.4% for p16 ( INK4a ), 34.8% for p73, 70.4% for GSTP1, 64.3% for MGMT, 13.0% for hMLH1, 59.1% for RARbeta, 82.6% for SOCS-1, and 80.9% for OPCML. CIMP+ (with six or more methylated genes) was detected in 68 (59.1%) of 115 HCCs and none of 48 nonneoplastic liver tissues. On stratified univariate analysis, patients with tumor-node-metastasis (TNM) stage I HCC with CIMP+ had significantly shorter overall survival (OS) (P = 0.002) and recurrence-free survival (RFS) (P = 0.042) than those with CIMP-. Furthermore, multivariate analysis revealed CIMP+ as an independent prognostic factor for both OS [hazard ratio (HR), 12.266; P = 0.015] and RFS (HR, 2.275; P = 0.032) in TNM stage I patients.

CONCLUSIONS

CIMP+ may specifically define a subgroup of patients with unfavorable outcome in TNM stage I HCC. Examination of CIMP status may be useful for stratifying prognosis of patients with early-stage HCC and identifying patients who are at higher risk for recurrence.

Effects of 5-Aza-CdR on the proliferation of human breast cancer cell line MCF-7 and on the expression of Apaf-1 gene

Hypermethylation in the promoter region of tumor suppressor genes is a common mechanism of gene silencing, which tends to occur in cancer. The effects of 5-Aza-2'-deoxycytidine (5-Aza-CdR), a specific DNA methyltransferase inhibitor, on the cell proliferation of human breast cancer cell line MCF-7 and on the expression of Apaf-1 gene were investigated. Human MCF-7 cells were incubated with increasing concentrations of 5-Aza-CdR for 12 to 120 h. The growth inhibition rates of MCF-7 cells were detected by MTT assay. Changes of cell cycle distribution and apoptotic rates of MCF-7 cells were determined by flow cytometry. The expressions of DNA methyltransferase 3b mRNA and Apaf-1 mRNA were measured by reverse transcription polymerase chain reaction (RT-PCR). Meanwhile, the expression of Apaf-1 protein was detected by Western blotting. The results showed that 5-Aza-CdR significantly inhibited the growth of MCF-7 cells and the growth inhibition rate of MCF-7 cells was significantly enhanced with the concentration of 5-Aza-CdR and the action time. Flow cytometry indicated that 5-Aza-CdR could significantly induce G(1)/S cell cycle arrest and increase the apoptosis rate of MCF-7 cells. The mRNA and protein expressions of Apaf-1 were up-regulated in MCF-7 cells treated with 5-Aza-CdR, which was accompanied by down-regulation of DNA methyltransferase 3b mRNA. It is concluded that 5-Aza-CdR might retard the growth of tumor cells and promote the apoptosis of MCF-7 breast cancer cells by inhibiting the expression of DNA methyltransferase 3b and re-activating the Apaf-1 gene expression.

Assessment of the effect of betaine on p16 and c-myc DNA methylation and mRNA expression in a chemical induced rat liver cancer model

Background

The development and progression of liver cancer may involve abnormal changes in DNA methylation, which lead to the activation of certain proto-oncogenes, such as c-myc, as well as the inactivation of certain tumor suppressors, such as p16. Betaine, as an active methyl-donor, maintains normal DNA methylation patterns. However, there are few investigations on the protective effect of betaine in hepatocarcinogenesis.

Methods

Four groups of rats were given diethylinitrosamine (DEN) and fed with AIN-93G diets supplemented with 0, 10, 20 or 40 g betaine/kg (model, 1%, 2%, and 4% betaine, respectively), while the control group, received no DEN, fed with AIN-93G diet. Eight or 15 weeks later, the expression of p16 and c-myc mRNA was examined by Real-time PCR (Q-PCR). The DNA methylation status within the p16 and c-myc promoter was analyzed using methylation-specific PCR.

Results

Compared with the model group, numbers and areas of glutathione S-transferase placental form (GST-p)-positive foci were decreased in the livers of the rats treated with betaine (P < 0.05). Although the frequency of p16 promoter methylation in livers of the four DEN-fed groups appeared to increase, there is no difference among these groups after 8 or 15 weeks (P > 0.05). Betaine supplementation attenuated the down-regulation of p16 and inhibited the up-regulation of c-myc induced by DEN in a dose-dependent manner (P < 0.01). Meanwhile, increases in levels of malondialdehyde (MDA) and glutathione S-transferase (GST) in model, 2% and 4% betaine groups were observed (P < 0.05). Finally, enhanced antioxidative capacity (T-AOC) was observed in both the 2% and 4% betaine groups.

Conclusion

Our data suggest that betaine attenuates DEN-induced damage in rat liver and reverses DEN-induced changes in mRNA levels.

Senescence induction; a possible cancer therapy

Cellular immortalization is a crucial step during the development of human cancer. Primary mammalian cells reach replicative exhaustion after several passages in vitro, a process called replicative senescence. During such a state of permanent growth arrest, senescent cells are refractory to physiological proliferation stimuli: they have altered cell morphology and gene expression patterns, although they remain viable with preserved metabolic activity. Interestingly, senescent cells have also been detected in vivo in human tumors, particularly in benign lesions. Senescence is a mechanism that limits cellular lifespan and constitutes a barrier against cellular immortalization. During immortalization, cells acquire genetic alterations that override senescence. Tumor suppressor genes and oncogenes are closely involved in senescence, as their knockdown and ectopic expression confer immortality and senescence induction, respectively. By using high throughput genetic screening to search for genes involved in senescence, several candidate oncogenes and putative tumor suppressor genes have been recently isolated, including subtypes of micro-RNAs. These findings offer new perspectives in the modulation of senescence and open new approaches for cancer therapy.