PTEN Promoter Hypermethylation Research Articles

Olaparib, a poly (ADP-ribose) polymerase (PARP) inhibitor, in combination with pembrolizumab and carboplatin as first-line treatment of recurrent or metastatic head and neck squamous-cell carcinoma (RM-HNSCC): A single-arm, phase 2 trial.

6016 Background: The homologous recombination deficiency (HRD) phenotype is common in HNSCC and is due to mutation and promoter hypermethylation of DNA repair genes ( BRCA1, BRCA2, ATR, ATM, and FANC) and PTEN. In pre-clinical models of HNSCC, HRD sensitizes tumor to PARP inhibition and to additive antitumor activity of PARP inhibition in combination with platinum agents. PARP inhibitors also activate the STING pathway and upregulate PD-L1 expression, resulting in synergistic antitumor activity when given with PD-1 inhibitors. Olaparib is a highly selective PARP inhibitor that has been safely combined with pembrolizumab and carboplatin. Methods: In this single-arm phase 2 trial, patients with RM-HNSCC, no prior therapy for RM disease, and adequate performance status and organ function received up to six 21-day cycles of olaparib (200 mg bid orally days 1-10), pembrolizumab (200 mg IV day 1), and carboplatin (AUC 5 IV day 1), followed by up to twenty-nine 21-day cycles of olaparib (oral 300 mg bid days 1-21) and pembrolizumab (200 mg day 1). Treatment continued until discontinuation criteria were met. The primary endpoint was objective response, assessed by an independent radiologist using iRECIST. The primary hypothesis was that this regimen would result in a higher objective response rate (ORR) than historically reported with 5-FU, pembrolizumab and a platinum agent in similar patients. A Simon optimal two-stage design tested the null hypothesis (H0 : ORR≤36%) versus the alternative hypothesis (H1 : ORR=62%) at a type I error rate of 10% and 90% power. In the first stage, up to 13 patients could be accrued. If ≥6 responses occur, 16 additional patients will be accrued. The null hypothesis will be rejected if ≥14 responses are observed in these 29 patients. At the end of the first stage, an interim analysis was be performed to assess olaparib delivery during cycles 1 and 2 with the goal of 100% delivery in ≥ 80% of patients. We report the results of the primary endpoint and olaparib delivery for the first stage of the trial. Results: Twelve patients enrolled into the first stage of the trial. Key characteristics included median age 62 years (range 59-74), tobacco history (Y-5; N-7), primary site (oropharynx-7; oral cavity-4; larynx-1), HPV status (positive: 6; negative: 6) and PD-L1 status (CPS 0: 1; 1-19: 4; ≥20: 7). Tumor response occurred in 8 patients (ORR 67%). The best tumor response to date was CR (1), PR (7), SD (3) and PD (1). Olaparib delivery during cycles 1 and 2 was 100% for all patients. Conclusions: Among patients with RM-HNSCC, first-line treatment with olaparib, pembrolizumab and carboplatin resulted in an ORR of 67% during the first stage of the trial. Olaparib delivery was 100%. Enrollment into the second stage is ongoing. Clinical trial information: NCT04643379 .

Synthetic essentiality between PTEN and core dependency factor PAX7 dictates rhabdomyosarcoma identity

PTEN promoter hypermethylation is nearly universal and PTEN copy number loss occurs in ~25% of fusion-negative rhabdomyosarcoma (FN-RMS). Here we show Pten deletion in a mouse model of FN-RMS results in less differentiated tumors more closely resembling human embryonal RMS. PTEN loss activated the PI3K pathway but did not increase mTOR activity. In wild-type tumors, PTEN was expressed in the nucleus suggesting loss of nuclear PTEN functions could account for these phenotypes. Pten deleted tumors had increased expression of transcription factors important in neural and skeletal muscle development including Dbx1 and Pax7. Pax7 deletion completely rescued the effects of Pten loss. Strikingly, these Pten;Pax7 deleted tumors were no longer FN-RMS but displayed smooth muscle differentiation similar to leiomyosarcoma. These data highlight how Pten loss in FN-RMS is connected to a PAX7 lineage-specific transcriptional output that creates a dependency or synthetic essentiality on the transcription factor PAX7 to maintain tumor identity.

Abstract 3022: Synthetic essentiality between PTEN and core dependency factor PAX7 dictates rhabdomyosarcoma indentity

Abstract Rhabdomyosarcoma (RMS) is an embryonal tumor resembling developing skeletal muscle and the most common pediatric soft-tissue sarcoma. RMS is molecularly defined by the presence or absence of a fusion oncoprotein corresponding with the histological subtypes alveolar and embryonal RMS, respectively. Embryonal, or fusion-negative, RMS (FN-RMS) is heterogeneous in its molecular alteration profile; the major exception is the near universal PTEN promoter hypermethylation found in FN-RMS corresponding with decreased PTEN expression. PTEN's functional role in FN-RMS remains unclear as does PTEN's role in defining tumor fate decisions. Organismal cancer models can help elucidate these decisions by defining the potential tumor fate landscape that can occur in transformed multipotent progenitor cells. Our laboratory leverages a highly penetrant, early onset model of FN-RMS driven by the transdifferentiation of endothelial progenitors into skeletal muscle-like RMS cells by Hedgehog pathway activation. Therefore, our model is uniquely primed to empirically determine the core regulatory factors critical in FN-RMS initiation. Here, we conditionally deleted Pten in these cells (ASPcKO). ASPcKO tumors presented earlier than wild-type tumors and more closely resemble human FN-RMS with a less differentiated skeletal muscle state. These were unique characteristics of ASPcKO tumors as mice with homozygous loss of other tumor suppressors - Cdkn2a, Trp53, and Rb1 - did not recapitulate these phenotypes. We further probed the downstream transcriptional outputs of ASPcKO tumors revealing a profound increase in expression of the neural developmental transcription factors Dbx1 and Pax7. These outputs are functionally important as human FN-RMS patient-derived xenografts are dependent on both DBX1 and PAX7. Subsequently, we also show that DBX1 is a downstream transcriptional target of PAX7 highlighting how Pten loss engages a unique transcriptional program for tumor maintenance. PAX7 is also a core FN-RMS regulatory circuit component. To further interrogate the role of PAX7 on tumor initiation, we concomitantly deleted Pten and Pax7 in our FN-RMS model and found not only that Pax7 loss rescues the survival kinetics observed when Pten is lost, but also alters the developmental trajectory of the tumors that do develop. Instead of Smoothened trans-differentiating our aP2-Cre expressing primordial endothelial cell into a skeletal-muscle like FN-RMS, Pten and Pax7 loss dictates these endothelial cells to give rise to tumors with smooth muscle-like differentiation, including human-like leiomyosarcoma. Together, this synthetic essential interaction between Pten and Pax7 in FN-RMS stresses the importance of the bifunctional role of PAX7 in tumor initiation and maintenance and how specific tumor suppressor loss can engage developmental transcriptional programs to alter tumor fate. Citation Format: Casey G. Langdon, Katherine E. Gadek, Matthew R. Garcia, Kristin B. Reed, Madeline Bush, Jason A. Hanna, Catherine J. Drummond, Matthew C. Maguire, Patrick J. Leavey, David Finkelstein, Hongjian Jin, Jerold E. Rehg, Mark E. Hatley. Synthetic essentiality between PTEN and core dependency factor PAX7 dictates rhabdomyosarcoma indentity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3022.

PTEN Promoter Hypermethylation Is Associated with Breslow Thickness in Acral Melanoma on the Heel, Forefoot, and Hallux

BackgroundAcral melanoma occurs on glabrous skin or the nail apparatus and is distinct from ultraviolet-related melanoma due to differing genetic alteration patterns. Although the pathogenesis of acral melanoma is not well understood, mechanical stress is thought to induce acral melanoma. The incidence of gene mutation and promoter methylation has been reported in tumors from acral melanoma; however, an association between genetic/epigenetic alterations and mechanical stress in acral melanoma remains unclear.ObjectiveTo investigate the relationship between clinical/genetic factors and mechanical stress in acral melanoma.MethodsA retrospective review of 52 patients diagnosed with acral melanoma was performed. We reviewed the clinical characteristics of patients, tumor status, and tumor location. Mutations in BRAF, NRAS, and the TERT promoter, along with KIT amplification and PTEN promoter methylation were analyzed in the tumors.ResultsThe heel (34/52, 65.4%) was the most common anatomical tumor site. Mutations in BRAF (6/48, 12.5%), NRAS (6/49, 12.2%), and the TERT promoter (4/33, 12.1%), along with KIT amplification (3/37, 8.1%) and PTEN promoter hypermethylation (12/48, 25.0%) were observed in the tumors. On the forefoot, heel, and hallux, PTEN promoter hypermethylation was significantly associated with Breslow thickness (p=0.001) and ulceration rate (p=0.042). On the midfoot and lesser toes, there was no significant difference in Breslow thickness or ulceration rate regardless of PTEN promoter hypermethylation (p>0.05).ConclusionPTEN promoter hypermethylation is associated with Breslow thickness and tumor ulceration on the forefoot, heel, and hallux in acral melanoma in Korean patients.

High-risk HPV infection modulates the promoter hypermethylation of APC, SFRP1, and PTEN in cervical cancer patients of North India.

Persistent infection with oncogenic HPV and downregulation of tumor suppressor genes play an essential role in the development and progression of cervical cancer. The present study aimed to identify the promoter methylation status of APC, SFRP1, and PTEN which are important regulators of Wnt pathway and their association with high-risk HPV infection and gene expression. Methylation Specific PCR (MSP) and quantitative reverse transcription PCR (RT-qPCR) were used to detect methylation status and gene expression levels of APC, SFRP1, and PTEN in cervical cancer biopsies (110) and paired non-cancerous biopsies (28). APC promoter was methylated in 38%, SFRP1 in 95%, and PTEN in 55% of the cervical cancer biopsies. Our data showed a trend of a higher rate of methylation of the gene promoters in cervical cancer biopsies while; they were majorly un-methylated in non-cancerous biopsies. Corresponding to a higher rate of methylation in cancer biopsies, the gene expression levels of APC, SFRP1, and PTEN were reduced in cervical cancer samples in comparison to normal cervix tissues. Further, we observed that 97% cancer biopsies were HPV infected and high-risk type HPV16 and 18 infections were significantly positively associated with APC (p = 0.008 and p = 0.007), SFRP1 (p = 0.003 and p = 0.0067), and PTEN (p = 0.049 and p = 0.008) promoter methylation. APC, SFRP1, and PTEN promoter hyper-methylation is positively associated with high-risk HPV infection and inversely associated with gene expression. Our findings show that high-risk HPV infection promotes methylation of these genes and further promotes their silencing.

The Relationship between the Methylation of Promoter Regions of Tumor Suppressor Genes PTEN and APC with Endometrial Cancer.

Background:Endometrial neoplasms is one of the most typical gynecologic diseases with harmful effects. Promoter hypermethylation is an important mechanism of the inactivation of tumor suppressor genes in endometrial neoplasms. Epigenetic changes of the PTEN and APC genes have shown to be present in various cancers. Therefore, in this study, we have investigated the association between the promoter hypermethylation of PTEN and APC genes with endometrial neoplasms. Methods:For this study, 28 patients with endometrial neoplasms as well as 22 controls were studied. Analysis of the promoter methylation regions of PTEN and APC genes were performed by Methylation-Specific PCR. Results:The frequency of PTEN and APC genes promoter methylation was 28.57% and 17.86% in tumor tissues, and 11.54% and 3.85% in blood samples, respectively. We found a significant relationship between blood and tissue in PTEN methylation (p = 0.0353). Additionally, we determined a closely significant difference between normal tissue and tumor tissue of the PTEN gene (p = 0.0787) and blood and tissue samples of the APC gene in methylated promoter regions (p=0.0623). Furthermore, these results suggest that there is no significant relationship between the promoter methylation of PTEN and APC with clinical characteristics.Conclusion:DNA methylation deficiency is a well known highlighted factor in tumorigenesis, therefore the promoter hypermethylation of PTEN and APC can be indicated as a risk factor in endometrial neoplasms.

Assessment of epigenetic alterations and in silico analysis of mutation affecting PTEN expression among Indian cervical cancer patients.

Genetic and epigenetic anomalies accountable for genetic dysregulation are the most common aberrations that determine the underlying heterogeneity of the tumor cells. Currently, phosphatase and tensin homolog (PTEN) incongruity has emerged as potent and persuasive malfunctioning in varied human malignancies. In this study, we have analysed the promoter hypermethylation and expression status of PTEN. We identified different mutations in the exonic region of PTEN. Functional consequences of these mutations were explored using in silico techniques. Promoter hypermethylation of PTEN was detected using methylation-specific polymerase chain reaction (MS-PCR), expression analysis was performed with immunohistochemistry (IHC) and mutation by direct sequencing in a total of 168 uterine cervix tumor cases. The findings were statistically correlated with the clinical parameters. In addition, the effect of nonsynonymous mutations was studied with molecular dynamics simulations. PTEN promoter hypermethylation (45.8%) was found to be significantly associated with the of PTEN loss (57.14%, P < 0.0001). Tumor stages, tumor size, lymph node (LN) were found to be significantly correlated with both PTEN promoter hypermethylation and PTEN loss. Histological grade, however, showed a significant association with only PTEN loss. In total, 11.76% of tumors exhibited mutations in exon 5 and 7, out of which E150K of exon 5 showed the highest deviations in the crystal structure of PTEN by in silico analysis. This study provides valuable insights into oncology and paves the path in the development of efficient biomarker and/or imperative therapeutic tool for cervical cancer treatment.

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

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

Global DNA methylation and PTEN hypermethylation alterations in lung tissues from human silicosis.

Silicosis is a respiratory disease caused by long-term silica dust exposure. Our previous study has demonstrated that silica mediates the activation of phosphatidylinositol 3-kinase (PI3K)/phosphatase and tensin homolog deleted on chromosome 10 (PTEN)/serine or threonine kinase (AKT)/mitogen-activated protein kinases (MAPK)/AP-1 pathway in human embryo lung fibroblasts (HELFs). The purpose of this study is to identify genome-wide aberrant DNA methylation profiling in lung tissues from silicosis patients. We performed Illumina Human Methylation 450K Beadchip arrays to investigate the methylation alteration in formalin-fixed, paraffin-embedded (FFPE) lung specimens, immunohistochemistry to detect the level of c-Jun and PTEN proteins; methylation specific PCR (MS-PCR) to identify PTEN and c-Jun promoter methylation in HELFs. We found 86,770 CpG sites and 79,660 CpG sites significantly differed in methylation status in early-stage and advanced-stage compared with GEO normal lung methylation data. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed the methylated status of MAPK signaling pathway was considered changed. The number of PTEN and c-Jun CpG promoter methylated-sites were increased in advanced-stage. Early-stage showed the positive expression of c-Jun and PTEN protein and negative or mild expression in advanced-stage. PTEN promoter was no differentially methylated and c-Jun promoter differed at 12 and 24 h in HELFs. Abnormal DNA methylation on genome-scale was implicated in silicosis, and PTEN promoter hypermethylation might be associated with decrease of PTEN protein.

Abstract 4449: TET1 inhibits gastric cancer metastasis by demethylation and re-expression of PTEN

Abstract TET1 is a member of ten eleven translocation enzymes, which can convert 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC), eventually to promote CpG islands demethylation of specific gene.. In this study, we found that TET1 expression and 5-hmC content were low in tumor tissues compared to its adjacent non-tumor tissues of gastric cancer. Cell proliferation, migration and invasion were enhanced when TET1 knocked down in gastric cancer cell in vitro and in vivo, while it was suppressed when TET1 over-expressed. We also found that PTENis one of the target genes of TET1. TET1 directly binds to the promoter region of PTEN, activates its transcription through demethylating its CpG islands. Knockdown of TET1 results in hypermethylation of PTEN promoter and low expression of PTEN. PTEN knockdown activates AKT and FAK pathway, which are suppressed by PTEN. The activation of PTEN downstream AKT and FAK facilitates tumor migration, invasion and accelerates cell growth. In conclution, we found a novel mechanism that TET1 suppresses tumor cell growth, migration and invasion through conversion PTEN promoter CpG island methylation to demehylation and then re-expression PTEN. Citation Format: Bingya Liu, Yao-fei Pei, Jian-fang Li, Liping Su, Ran Tao, Min Yan, Zhang-gang Zhu. TET1 inhibits gastric cancer metastasis by demethylation and re-expression of PTEN. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4449.

Role of promoter hypermethylation and epigenetic silencing of PTEN in periampullary carcinoma

Role of promoter hypermethylation and epigenetic silencing of PTEN in periampullary carcinoma

PTEN and p16 genes as epigenetic biomarkers in oral squamous cell carcinoma (OSCC): a study on south Indian population.

Phosphatase and tensin homolog (PTEN) and p16INK4a (p16) genes are tumor suppressor genes, associated with epigenetic alterations. PTEN and p16 promoter hypermethylation is a major epigenetic silencing mechanism leading to cancer. The cooperation between PTEN and p16 in pathogenesis of cancers suggest that their combination might be considered as potential molecular marker for specific subgroups of patients. Hence, the present study aimed to investigate whether PTEN and p16 promoter methylations were involved in oral squamous cell carcinoma (OSCC) in south Indian subjects. DNA methylation quantitative analyses of the two candidate tumor suppressor genes PTEN and p16 were performed by methylation-specific polymerase chain reaction (MSP). Fifty OSCC biopsy samples and their corresponding non-malignant portions as controls were studied comparatively. The methylation status was correlated with the clinical manifestations. Twelve out of 50 patients (24%) were found to be methylated for PTEN gene, whereas methylation of the p16 gene occurred in 19 out of 50 cases (38%). A statistically significant result was obtained (P = <0.0001 and 0.017) for both PTEN and p16 genes. PTEN and p16 promoter methylation may be the main mechanism leading to the low expression of PTEN and p16 genes indicating the progress of tumor development. Our data suggest that a low PTEN and p16 expression due to methylation may contribute to the cancer progression and could be useful for prognosis of OSCC. Therefore, analysis of promoter methylation in such genes may provide a biomarker valuable for early detection of oral cancer.

Association of CCND1 overexpression with KRAS and PTEN alterations in specific subtypes of non-small cell lung carcinoma and its influence on patients' outcome.

Cyclin D1 is one of the major cellular oncogenes, overexpressed in number of human cancers, including non-small cell lung carcinoma (NSCLC). However, it does not exert tumorigenic activity by itself, but rather cooperates with other altered oncogenes and tumor suppressors. Therefore, in the present study, we have examined mutual role of cyclin D1, KRAS, and PTEN alterations in the pathogenesis of NSCLC and their potential to serve as multiple molecular markers for this disease. CCND1 gene amplification and gene expression were analyzed in relation to mutational status of KRAS gene as well as to PTEN alterations (loss of heterozygosity and promoter hypermethylation) in NSCLC patient samples. Moreover, the effect of these co-alterations on patient survival was examined. Amplified CCND1 gene was exclusively associated with increased gene expression. Statistical analyses also revealed significant association between CCND1 overexpression and KRAS mutations in the whole group and in the groups of patients with adenocarcinoma, grade 1/2, and stage I/II. In addition, CCND1 overexpression was significantly related to PTEN promoter hypermethylation in the whole group and in the group of patients with squamous cell carcinoma and lymph node invasion. These joint alterations also significantly shortened patients' survival and were shown to be an independent factor for adverse prognosis. Overall results point that cyclin D1 expression cooperates with KRAS and PTEN alterations in pathogenesis of NSCLC, and they could serve as potential multiple molecular markers for specific subgroups of NSCLC patients as well as prognostic markers for this type of cancer.

RASSF1 and PTEN Promoter Hypermethylation Influences the Outcome in Epithelial Ovarian Cancer

BackgroundTo investigate the methylation pattern in promoter region of RASSF1A and PTEN genes in epithelial ovarian cancer patients in North India. Patients and MethodsFifty patients and 20 healthy controls were studied. Isolation of genomic DNA from peripheral blood and methylation-specific polymerase chain reaction (MSP) were applied for analysis. Results17 of 50 patients (34.0%) were found to be methylated for RASSF1A gene, whereas methylation of the PTEN gene occurred in 8 of 50 cases (16.0%). A statistically significant result was obtained (P = .01) for RASSF1A gene and correlated with the patients' clinicopathologic features. ConclusionHypermethylation of both RASSF1A and PTEN genes in blood DNA from ovarian cancer patients might offer an exposition for early diagnosis of the malignancy.

The importance of distinguishing pseudogenes from parental genes.

Dear Editor, The July-August 2014 issue of Clinical Epigenetics featured a research article describing PTEN promoter hypermethylation in multiple myeloma by Piras et al. [1]. The importance of the PTEN gene has resulted in significant efforts to identify sequence, expression and methylation changes in cancer. Piras et al. concluded that PTEN hypermethylation occurred in a subset of multiple myeloma cases but that hypermethylation did not correlate with reduced gene expression or clinical parameters. The PTEN mRNA shares 97.8% sequence identity with a pseudogene known as PTENP1. A 921-bp region of the promoters of these genes is also 91% identical. Consequently, careful consideration of assay design is required to avoid amplification of PTENP1 rather than PTEN sequences. However, the method used by Piras et al. for measuring PTEN mRNA did not distinguish between these homologues, despite numerous studies showing that PTENP1 mRNA is ubiquitously expressed in both normal and cancer specimens [2-5]. Furthermore, previous studies have demonstrated that apparent methylation of the PTEN promoter is likely attributable to the non-specific amplification of the highly homologous PTENP1 gene [6,7]. We have shown that the only reliable method for distinguishing between PTEN and PTENP1 promoter methylation is single-molecule bisulfite sequencing that utilizes sequence differences between the two genes to separately analyze individual promoter molecules [6,8]. These methodological challenges make comparisons between methylation and expression impossible when using assays that do not reliably discriminate between PTEN and PTENP1, and also negate the value of correlating these features with clinicopathological characteristics. The challenges posed by sequence homology with pseudogenes are by no means particular to the PTEN gene. For example, the DNA mismatch repair gene PMS2 shares >95.2% sequence identity with at least six other

Frequent mono-allelic loss associated with deficient PTEN expression in imatinib-resistant gastrointestinal stromal tumors

Insufficiency of phosphatase and tensin homolog (PTEN) occurs in numerous tumor types and has been implicated as a resistance mechanism to receptor tyrosine kinase-targeted therapies in human cancer. In this study, we have performed a comprehensive molecular and immunohistochemical characterization of PTEN in 58 imatinib-naïve and 54 imatinib-treated gastrointestinal stromal tumors (GISTs). The findings were correlated with clinicopathological data. At the genomic level, PTEN was affected mainly by mono-allelic loss, which was significantly less frequent in imatinib-naïve vs imatinib-resistant tumors (9% vs 39%, P<0.001). Neither PTEN mutations nor PTEN promoter hyper-methylation were found. By immunohistochemistry, PTEN depletion was clearly related to GIST progression. Low PTEN protein expression was common (50%) and often paralleled with total immunonegativity in imatinib-resistant tumors. The abnormal PTEN protein expression correlated with PTEN loss at the genomic level (P=0.001). In addition, the effect of small interfering RNA (siRNA) PTEN knockdown on KIT signaling was examined in GIST-T1 and GIST430 cell lines, in the absence or presence of a dual PI3K/mTOR inhibitor NVP-BEZ235, alone or in combination with imatinib. In both cell lines, siRNA silencing of PTEN resulted in the substantial upregulation of PI3K-AKT and MAPK pathways. The MAPK hyperactivation was further potentiated by NVP-BEZ235 in the imatinib-sensitive GIST-T1 cells; yet, this effect was counteracted efficiently by combined treatment. In the imatinib-resistant GIST430 cells, neither NVP-BEZ235 alone or in combination with imatinib yielded sufficient inhibition of hyper-phosphorylated MAPK and downstream intermediate S6 protein. In conclusion, depleted PTEN expression associated with mono-allelic PTEN loss occurs frequently in imatinib-resistant GIST and might serve as a biomarker for stratifying patients for optimal treatment. In vitro, the PTEN insufficiency leads to hyperactivation of AKT and MAPK pathways in tumor cells. Novel therapies targeting multiple components of the integrated KIT receptor signaling pathways in imatinib-resistant GIST warrant further studies.

Methylation analysis of the phosphates and tensin homologue on chromosome 10 gene (PTEN) in multiple myeloma.

BackgroundAberrant DNA methylation of promoter region CpG islands is an alternative mechanism that leads to genetic defects in the inactivation of tumor suppressor genes during myelomagenesis. The aim of this study was to examine the promoter methylation status of the phosphates and tensin homologue on chromosome 10 (PTEN) gene in a cohort of multiple myeloma patients.FindingsThe PTEN gene was hypermethylated in 7 out of 58 (12%) primary myeloma samples. The correlation between functional inactivation and PTEN mRNA levels was not statistically significant. The multiple myeloma subgroup with an aberrant PTEN status had a prevalence of the component IgG, Salmon Durie stage I, lower lactate dehydrogenase levels, intermediate-standard cytogenetic risk and longer overall survival with the respect to the unmethylated subgroup.ConclusionsThis is the first report demonstrating the presence of PTEN promoter hypermethylation in multiple myeloma.

Association of promoter methylation and 32-bp deletion of the PTEN gene with susceptibility to metabolic syndrome

Metabolic syndrome (MeS), a cluster of several metabolic disorders, is increasingly being recognized as a risk factor for type II diabetes (T2D) and cardiovascular disease. Genetic and epigenetic alteration of the phosphatase and tensin homolog deleted on chromosome ten (PTEN) has been associated with components of MeS. The aim of the present study was to investigate the possible association of a 32-bp deletion polymorphism and promoter methylation of the PTEN gene with MeS. DNA was extracted from the peripheral blood of 151subjects with and 149subjects without MeS. The 32-bp deletion variant of PTEN was detected by polymerase chain reaction (PCR) and PTEN promoter methylation was defined by a nested methylation‑specific PCR (MSP) method. No significant differences were found in the allelic and genotypic frequencies of the 32-bp deletion variant of PTEN between the groups [odds ratio (OR), 0.77; 95% confidence interval (CI), 0.41-1.45; P=0.431]. However, patients with MeS were identified to have lower levels of PTEN promoter hypermethylation than subjects without MeS. Promoter methylation may be a protective factor against susceptibility to MeS (OR, 0.52; 95% CI, 0.29-0.92; P=0.029). Our findings suggest that PTEN promoter methylation may be a mechanism for PTEN downregulation or silencing in MeS, which remains to be fully clarified.

DNMT1-mediated PTEN hypermethylation confers hepatic stellate cell activation and liver fibrogenesis in rats

Hepatic stellate cell (HSC) activation is an essential event during liver fibrogenesis. Phosphatase and tension homolog deleted on chromosome 10 (PTEN), a tumor suppressor, is a negative regulator of this process. PTEN promoter hypermethylation is a major epigenetic silencing mechanism in tumors. The present study aimed to investigate whether PTEN promoter methylation was involved in HSC activation and liver fibrosis. Treatment of activated HSCs with the DNA methylation inhibitor 5-aza-2′-deoxycytidine (5-azadC) decreased aberrant hypermethylation of the PTEN gene promoter and prevented the loss of PTEN expression that occurred during HSC activation. Silencing DNA methyltransferase 1 (DNMT1) gene also decreased the PTEN gene promoter methylation and upregulated the PTEN gene expression in activated HSC-T6 cells. In addition, knockdown of DNMT1 inhibited the activation of both ERK and AKT pathways in HSC-T6 cells. These results suggest that DNMT1-mediated PTEN hypermethylation caused the loss of PTEN expression, followed by the activation of the PI3K/AKT and ERK pathways, resulting in HSC activation.

DNA methylation of PTEN gene promoter region is not correlated with urocystic tumorigenesis

Tumor suppressor gene PTEN plays an important role in cell cycle. Disorder of PTEN protein can cause cell growth and division in an uncontrolled way, which can lead to the formation of tumors. It has been proven that epigenetic mechanisms, such as promoter hypermethylation, may account for inactivation of PTEN in a subset of tumors. PTEN promoter hypermethylation has been found to be involved in many kinds of cancers. Up to date, no report about the relationships between methylation of PTEN promoter region and bladder cancer has been found. To investigate the methylation pattern of PTEN gene transcriptional regulation region (TRR), bisulfite-specific (BSP) polymerase chain reaction (PCR)- based sequencing analysis was performed among 15 bladder cancer tissues and five normal bladder tissues. Analysis of PTEN gene TRR methylation showed that the methylation level in bladder cancer had no significant difference with that of normal (P = 0.4307, by unpaired Student’s t test). Key words: PTEN, promoter methylation, bladder cancer.