PTEN hypermethylation profiles of Chinese Kazakh patients with esophageal squamous cell carcinoma

PTEN: A Thrifty Gene That Causes Disease in Times of Plenty?

The modern obesity epidemic with associated disorders of metabolism and cancer has been attributed to the presence of "thrifty genes". In the distant past, these genes helped the organism to improve energy efficiency and store excess energy safely as fat to survive periods of famine, but in the present day obesogenic environment, have turned detrimental. I propose PTEN as the likely gene as it has functions that span metabolism, cancer and reproduction, all of which are deranged in obesity and insulin resistance. The activity of PTEN can be calibrated in utero by availability of nutrients by the methylation arm of the epigenetic pathway. Deficiency of protein and choline has been shown to upregulate DNA methyltransferases (DNMT), especially 1 and 3a; these can then methylate promoter region of PTEN and suppress its expression. Thus, the gene is tuned like a metabolic rheostat proportional to the availability of specific nutrients, and the resultant "dose" of the protein, which sits astride and negatively regulates the insulin-PI3K/AKT/mTOR pathway, decides energy usage and proliferation. This "fixes" the metabolic capacity of the organism periconceptionally to a specific postnatal level of nutrition, but when faced with a discordant environment, leads to obesity related diseases.

DNMT1 mediates metabolic reprogramming induced by Epstein-Barr virus latent membrane protein 1 and reversed by grifolin in nasopharyngeal carcinoma

Cancer cells frequently adapt fundamentally altered metabolism to support tumorigenicity and malignancy. Epigenetic and metabolic networks are closely interactive, in which DNA methyltransferases (DNMTs) play important roles. Epstein–Barr virus (EBV)-encoded latent membrane protein 1 (EBV-LMP1) is closely associated with nasopharyngeal carcinoma (NPC) pathogenesis because it can trigger multiple cell signaling pathways that promote cell transformation, proliferation, immune escape, invasiveness, epigenetic modification, and metabolic reprogramming. Our current findings reveal for the first time that LMP1 not only upregulates DNMT1 expression and activity, but also promotes its mitochondrial translocation. This induces epigenetic silencing of pten and activation of AKT signaling as well as hypermethylation of the mtDNA D-loop region and downregulation of oxidative phosphorylation (OXPHOS) complexes, consequently, leading to metabolic reprogramming in NPC. Furthermore, we demonstrate that grifolin, a natural farnesyl phenolic compound originated from higher fungi, is able to attenuate glycolytic flux and recover mitochondrial OXPHOS function by inhibiting DNMT1 expression and activity as well as its mitochondrial retention in NPC cells. Therefore, our work establishes a mechanistic connection between epigenetics and metabolism in EBV-positive NPC and provides further evidence for pathological classification based on CpG island methylator phenotype (CIMP) in EBV-associated malignancies. In addition, grifolin might be a promising lead compound in the intervention of high-CIMP tumor types. The availability of this natural product could hamper tumor cell metabolic reprogramming by targeting DNMT1.

Basal progenitor cells bridge the development, malignant cancers, and multiple diseases of esophagus

The esophagus is a pivotal organ originating from anterior foregut that links the mouth and stomach. Moreover, its development involves precise regulation of multiple signal molecules and signal transduction pathways. After abnormal regulation of these molecules in the basal cells of the esophagus occurs, multiple diseases, including esophageal atresia with or without tracheoesophageal fistula, Barrett esophagus, gastroesophageal reflux, and eosinophilic esophagitis, will take place as a result. Furthermore, expression changes of signal molecules or signal pathways in basal cells and the microenvironment around basal cells both can initiate the switch of malignant transformation. In this review, we highlight the molecular events underlying the transition of normal development to multiple esophageal diseases. Additionally, the animal models of esophageal development and related diseases, challenges, and strategies are extensively discussed.

Association of genetic polymorphisms in PTEN and additional gene-gene interaction with risk of esophageal squamous cell carcinoma in Chinese Han population

This study aims to investigate the association of five single nucleotide polymorphisms (SNPs) in the phosphatase and tensin homologue (PTEN) gene and additional role of gene-gene interaction with esophageal squamous cell carcinoma (ESCC), based on a Chinese case-control study. A total of 871 subjects (420 males and 451 females) were selected, including 425 ESCC cases and 446 controls. Five SNPs were selected for genotyping in the case-control study: rs2735343, rs555895, rs2299939, rs17431184 and rs701848. Logistic regression model was used to examine the association between five SNP and ESCC, and additional interaction among five SNP, odds ratio (OR) and 95% confident interval (95%CI) were calculated. All genotypes were distributed according to Hardy-Weinberg equilibrium in controls. The carriers of homozygous mutant of rs2735343 and rs701848 polymorphism revealed increased ESCC risk than those with wild-type homozygotes, and OR (95%CI) were 1.27 (1.09-2.08) and 1.45 (1.17-1.98), respectively. We also found a potential gene-gene interaction between rs2735343 and rs701848 (P = 0.0010), and a potential gene-gene interaction among all five SNP (P = 0.0107) after covariates adjustment. Subjects with TC or CC of rs2735343 and TC or CC of rs701848 genotype have highest ESCC risk, compared to subjects with TT of rs2735343 and TT of rs701848 genotype, OR (95% CI) was 2.76 (1.37-3.45) after covariates adjustment. The carriers of homozygous mutant of rs2735343 and rs701848 polymorphism revealed increased ESCC risk. We also found a potential gene-gene interaction between rs2735343 and rs701848 and a potential gene-gene interaction among all five SNPs.

Grifolin directly targets ERK1/2 to epigenetically suppress cancer cell metastasis

Grifolin, a secondary metabolite isolated from the fresh fruiting bodies of the mushroom Albatrellus confluens, has been reported by us and others to display potent antitumor effects. However, the molecular target of grifolin has not been identified and the underlying mechanism of action is not fully understood. Here, we report that the ERK1/2 protein kinases are direct molecular targets of grifolin. Molecular modeling, affinity chromatography and fluorescence quenching analyses showed that grifolin directly binds to ERK1/2. And in vitro and ex vivo kinase assay data further demonstrated that grifolin inhibited the kinase activities of ERK1/2. We found that grifolin suppressed adhesion, migration and invasion of high-metastatic cancer cells. The inhibitory effect of grifolin against tumor metastasis was further confirmed in a metastatic mouse model. We found that grifolin decreased phosphorylation of Elk1 at Ser383, and the protein as well as the mRNA level of DNMT1 was also down-regulated. By luciferase reporter and ChIP assay analyses, we confirmed that grifolin inhibited the transcription activity of Elk1 as well as its binding to the dnmt1 promoter region. Moreover, we report that significant increases in the mRNA levels of Timp2 and pten were induced by grifolin. Thus, our data suggest that grifolin exerts its anti-tumor activity by epigenetic reactivation of metastasis inhibitory-related genes through ERK1/2-Elk1-DNMT1 signaling. Grifolin may represent a promising therapeutic lead compound for intervention of cancer metastasis, and it may also be useful as an ERK1/2 kinase inhibitor as well as an epigenetic agent to further our understanding of DNMT1 function.

The association of PTEN hypermethylation and breast cancer: a meta-analysis

OBJECTIVE

Phosphatase and tensin homolog (PTEN) deleted on chromosome 10, as a tumor suppressor gene, is crucial for the development of both familial and sporadic breast cancer (BC). The aim of this study was to perform a meta-analysis to evaluate the clinicopathological significance of PTEN promoter hypermethylation in BC.

METHODS

A comprehensive literature search was made in PubMed, Embase, Google Scholar, Chinese database (China National Knowledge Infrastructure [CNKI]), and Web of Science. The analysis of pooled data was performed with Review Manager 5.2. The fixed-effects or random-effects models were used to evaluate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

The meta-analysis included eight studies and a total of 923 patients. The frequency of PTEN promoter hypermethylation was significantly increased in ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC) compared to normal breast tissues (OR =22.53, P=0.0002 and OR =22.86, P<0.00001, respectively). However, the frequency of PTEN promoter hypermethylation was similar between IDC and DCIS. Additionally, PTEN methylation was not significantly correlated to estrogen receptor (ER) or human epidermal growth factor type 2 (HER-2) status in patients with BC.

CONCLUSION

PTEN promoter hypermethylation is significantly associated with the risk of DCIS and IDC, suggesting PTEN promoter hypermethylation is a valuable biomarker for diagnosis of BC.

Association between Ras association domain family 1A promoter methylation and esophageal squamous cell carcinoma: a meta-analysis

RASSF1A has been reported to be a candidate tumor suppressor in esophageal squamous cell carcinoma (ESCC). However, the association between RASSF1A promoter methylation and ESCC remains unclear. Eligible studies were identified through searching PubMed, Medline, Web of Science, and the China National Knowledge Infrastucture database. Studies were pooled and odds ratios (ORs) with corresponding confidence intervals (CIs) were calculated. Funnel plots were also performed to evaluate publication bias. Twelve studies involving 859 cases and 675 controls were included in this meta-analysis. A significant association was observed between RASSF1A methylation and ESCC overall (OR = 11.7, 95% CI: 6.59-20.9, z=8.36, P<0.00001). Subgroup analysis showed that the OR for heterogeneous tissues was 5.35 (95% CI = 2.95-9.71) while for autologous tissues it was 16.0 (8.31-30.96). For patient sample size, the OR for the <50 subgroup was 9.92 (95% CI = 2.88-34.2) and for the 50 case group was 13.1 (95% CI = 6.59-25.91). The OR for a relationship between RASSF1A methylation and TNM stages was 0.27 (95% CI=0.10-0.77), whereas there were no significant differences in RASSF1A methylation in relation to gender and differentiation among ESCC cases. This meta-analysis suggests a significant association between RASSF1A methylation and ESCC.

PTEN gene is infrequently hypermethylated in human esophageal squamous cell carcinoma

Whether promoter hypermethylation of phosphatase and tensin homologue deleted from chromosome 10 (PTEN) is associated with loss of PTEN expression was not yet elucidated in esophageal squamous cell carcinoma (ESCC). The methylation status of PTEN gene was evaluated in 74 ESCC specimens and four esophageal cancer cell lines. Its association with clinicopathological factors or the prognosis was investigated by statistical analysis. We further measured messenger RNA (mRNA) and protein level of PTEN by quantitative RT-PCR and immunohistochemistry and studied the role of PTEN hypermethylation in loss of PTEN expression in clinical samples. Next, demethylation of PTEN gene with 5-azaC in EC9706 was performed to confirm the clinical findings. PTEN methylation was only found in 14 (18.9 %) of 74 ESCC tumor samples and one (EC9706) of four esophageal cancer cell lines. PTEN methylation was not statistically associated with clinicopathological factors and the prognosis (p > 0.05). In addition, 41 patients (55.4 %) and 38 patients (51.4 %) showed reduced mRNA level of PTEN and negative expression of PTEN protein in ESCC tumors, respectively. Detailed analysis indicated that PTEN methylation was a possible mechanism of loss of PTEN expression in ESCC, and further 5-azaC demethylation revealed inversed methylation status and increased mRNA or protein level of PTEN in EC9706. However, the role of PTEN methylation in loss of PTEN expression was still limited due to low frequency of methylation in ESCC. PTEN hypermethylation is a rare event and did not play an important role in the prognosis and loss of PTEN expression in ESCC.

Clinical implications of PTEN and VEGF expression status, as well as microvessel density in esophageal squamous cell carcinoma

There are limitations to the use of single biomarker levels, for example phosphate and tensin homology (PTEN) or vascular endothelial growth factor (VEGF), in the diagnosis of esophageal squamous cell carcinoma (ESCC). The present study therefore aimed to evaluate the clinical implications of combined detection of multiple biomarkers. The associations between PTEN and VEGF expression status, microvessel density (MVD), and the pathological characteristics of 50 patients with ESCC were determined using χ², analysis of variance, and t-tests. The results indicated that the PTEN-positive rate was negatively correlated with ESCC histological grade (P<0.01), depth of ESCC invasion (P<0.01) and lymph node metastasis status. Furthermore, the VEGF-positive rate was correlated with lymph node metastasis status, while MVD was correlated with the depth of ESCC invasion (P<0.01) and lymph node metastasis status (P<0.05). The PTEN-positive rate was negatively correlated with the VEGF-positive rate. A higher MVD was identified in ESCC samples than that of the normal esophageal mucosa, particularly in VEGF-positive ESCC specimens compared with those of VEGF-negative specimens, and PTEN-negative ESCC specimens compared with that of the PTEN-positive ESCC specimens. These results suggested that combined detection of PTEN and VEGF levels, as well as evaluation of MVD in patients with ESCC may provide essential information for improvements in the diagnosis and prognosis of ESCC.

Molecular mechanisms of ethanol-associated oro-esophageal squamous cell carcinoma

Alcohol drinking is a major etiological factor of oro-esophageal squamous cell carcinoma (OESCC). Both local and systemic effects of ethanol may promote carcinogenesis, especially among chronic alcoholics. However, molecular mechanisms of ethanol-associated OESCC are still not well understood. In this review, we summarize current understandings and propose three mechanisms of ethanol-associated OESCC: (1) Disturbance of systemic metabolism of nutrients: during ethanol metabolism in the liver, systemic metabolism of retinoids, zinc, iron and methyl groups is altered. These nutrients are known to be associated with the development of OESCC. (2) Disturbance of redox metabolism in squamous epithelial cells: when ethanol is metabolized in oro-esophageal squamous epithelial cells, reactive oxygen species are generated and produce oxidative damage. Meanwhile, ethanol may also disturb fatty-acid metabolism in these cells. (3) Disturbance of signaling pathways in squamous epithelial cells: due to its physico-chemical properties, ethanol changes cell membrane fluidity and shape, and may thus impact multiple signaling pathways. Advanced molecular techniques in genomics, epigenomics, metabolomics and microbiomics will help us elucidate how ethanol promotes OESCC.