PTEN, RASSF1 and DAPK site‐specific hypermethylation and outcome in surgically treated stage I and II nonsmall cell lung cancer patients

Abstract

The primary objective of this study is to identify prognostic site-specific epigenetic changes in surgically treated Stage I and II nonsmall cell lung cancer (NSCLC) patients by quantifying methylation levels at multiple CpG sites within each gene promoter. Paraffin-embedded tumors from stage Ib, IIa and IIb in training and validation groups of 75 and 57 surgically treated NSCLC patients, respectively, were analyzed for p16, MGMT, RASSF1, RASSF5, CDH1, LET7, DAPK and PTEN promoter hypermethylation. Hypermethylation status was quantified individually at multiple CpG sites within each promoter by pyrosequencing. Molecular and clinical characteristics with time to recurrence (TTR) and overall survival (OS) were evaluated. Overall average promoter methylation levels of MGMT and RASSF1 were significantly higher in smokers than in nonsmokers (p 5 0.006 and p 5 0.029, respectively). Methylation levels of the p16 promoter were significantly higher in squamous cell carcinoma than in adenocarcinoma (p 5 0.020). In univariate analysis, hypermethylation of RASSF1 at CpG sites 253 and 248 and PTEN at CpG site 21310 were the significantly associated with shorter TTR (p 5 0.002 and p < 0.000, respectively). Hypermethylation of PTEN at 21310 and DAPK at 21482 were most significantly associated with outcome in multivariate analysis. These results show that methylation of specific promoter CpG sites in PTEN, RASSF1 and DAPK is associated with outcome in early stage surgically treated NSCLC.

Genetic and epigenetic changes in lung carcinoma and their clinical implications

“…In lung adenocarcinomas/squamous cell carcinomas, the frequency of p16, MGMT, RASSF1, MTHFR, and FHIT promoter methylation was significantly higher among smokers than never-smokers. [98][99][100][101] On the other hand, methylation in certain genes, such as RASSF2, TNFRSF10C, BHLHB5, and BOLL, 102,103 was higher in lung cancers from never-smokers than those from smokers, suggesting smoking may target specific genes for methylation.…”

“…Hypermethylation of RASSF1A, PTEN, DAPK, p16, Wif-1, CXCL12, DLEC1, MLH1, H-cadherin, APC, RUNX3, H-cadherin, SPARC, and DAL-1 was significantly associated with poor prognosis in patients with surgically resected lung adenocarcinomas/ squamous cell carcinomas. 101,106,[108][109][110][111][112][113] In addition, methylation of 14-3-3 sigma in pretreatment serum DNA was found to be an independent prognostic factor for survival in patients with lung adenocarcinoma, squamous cell carcinoma, and large cell carcinoma who were treated with platinum-based chemotherapy. 114 Previous researchers have reported that methylation, in addition to occurring in tumor tissues, can also be detected in blood samples or in exfoliated material of the aero-digestive tract epithelium from lung cancer patients, such as the methylation of RASSF1A, 115,116 p16, H-cadherin, 117 MAGE A1, and MAGE B2.…”

Epigenetic Control of Tumor Suppressor Genes in Lung Cancer

“…Clinical evidence also showed that TSG promoter methylation is associated with the smoking history of patients with lung cancer. In lung adenocarcinomas and squamous cell carcinomas, the frequency of p16, MGMT, RASSF1, MTHFR, and FHIT promoter methylation was significantly higher among smokers than never-smokers (42)(43)(44)(45); but the promoter methylation of other genes such as RASSF2, TNFRSF10C, BHLHB5, and BOLL was higher in never-smoker lung cancer patients than those of smokers (46,47), suggesting smoking may target specific genes for methylation. The roles of methylation in lung cancers for early detection, risk assessment, disease progression, and prognosis have also been studied.…”

Epigenetic alterations in endocrine-related cancer

“…In sporadic breast tumors, P16, MGMT, VHL, MLH1, and BRCA1 have also been shown to be important as prognostic factors (Bosviel et al 2012), and all are DNA repair and tumor suppressor genes that have been demonstrated to be epigenetically inactivated by DNA methylation in cancers. RASSF1A hypermethylation is associated with a shorter recurrence time, in ovarian, or thyroid tumors (Schagdarsurengin et al 2009, Buckingham et al 2010, Brzezianska & Pastuszak-Lewandoska 2011. P16 silencing, by this epigenetic mechanism, seems to be an early event in the development and progression of ovarian cancers (Dhillon et al 2004b).…”