Cigarette smoke induces promoter methylation of single‐stranded DNA‐binding protein 2 in human esophageal squamous cell carcinoma

Abstract

Esophageal squamous cell carcinoma (ESCC) is the sixth most frequent cause of cancer death in the world, and cigarette smoke is a key factor in esophageal carcinogenesis. To identify molecular changes during cigarette smoke-induced ESCC, we examined the methylation status of 13 gene promoters in the human immortalized, nontumorigenic esophageal epithelial cell line (Het-1A) that were exposed to mainstream (MSE) or sidestream cigarette smoke extract (SSE) for 6 months in culture. The promoter of sequence-specific single-stranded DNA-binding protein 2 (SSBP2) was methylated in the Het-1A cells exposed to MSE (MSE-Het-1A). Promoter methylation (86%, 56/70) and downregulation of SSBP2 expression were frequently detected in tumor tissues from ESCC patients. In addition, reintroduction of SSBP2 in an ESCC cell line (TE1) that does not express SSBP2 and in the MSE-Het-1A cells inhibited expression of LRP6 and Dvl3, which are mediators of the Wnt signaling pathway. SSBP2 expression markedly decreased the colony-forming ability of ESCC cell lines and significantly inhibited cell growth of the MSEHet-1A cells. Our results indicate that cigarette smoking is a cause of SSBP2 promoter methylation and that SSBP2 harbors a tumor suppressive role in ESCC through inhibition of the Wnt signaling pathway.Esophageal squamous cell carcinoma (ESCC) is the eighth most common type of caner, accounting for more than 90% cases of esophageal cancer worldwide. 1 Most patients with ESCC are diagnosed at an advanced stage, and metastasis to the regional lymph nodes occurs frequently. 2 There is considerable epidemiological evidence suggesting that alcohol, tobacco, diets deficient in vitamins/protective antioxidants, carcinogens and thermal injuries are important in the pathogenesis of ESCC. 3,4 Among all these, tobacco smoking is a key risk factor for the development of ESCC, 5 and the risk increases with long-term and/or passive smoking and rises markedly for people who both smoke and drink.The progressive transformation of a normal cell to a malignant cell is accompanied by a series of genetic/epigenetic changes, which include inactivation of tumor suppressor genes (TSGs) and activation of oncogenes. 6 One of major epigenetic events involved in functional inactivation of TSG in the process of malignant transformation is loss of gene expression by aberrant DNA methylation, which has appeared as an emerging molecular marker in human cancer. 7 We have identified novel TSGs inactivated by promoter methylation in ESCC; e.g., N-methyl-D-aspartic acid receptor 2B (NMDAR2B) 8,9 and neurofilament heavy chain polypeptide (NEFH). 8 In addition, correlations between aberrant gene methylation and smoking exposure are often observed in smoking-related human cancer; for example, hypermethylation of the APC and p16 promoters is associated with tobacco smoking in nonsmall cell lung carcinoma, 10 colon cancer 11 and cervical squamous cell carcinoma. 12 The methylation level of NEFH in noncancerous esophageal mucosa has a significant correlation with smokin...

Current Genetics and Epigenetics of Smoking/Tobacco-Related Cardiovascular Disease

“…Wet laboratory work, which could experimentally address the presence and consequences of methylation changes in cardiovascular candidate genes that could be caused by tobacco smoke exposure in appropriate cell cultures, seems to be altogether lacking. Successful proof-of-concept for such investigations can be found in the literature on malignant sequelae of smoking, 41 including follow-up studies to support the functional relevance of hits from an epigenome-wide methylation screen. 42 …”

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone Induces Retinoic Acid Receptor β Hypermethylation through DNA Methyltransferase 1 Accumulation in Esophageal Squamous Epithelial Cells

“…Tobacco contains more than 60 carcinogens (Hoffmann et al, 1990;Hecht et al, 2006) and tobacco exposure is known to induce genetic and epigenetic changes in esophageal squamous and lung cancer cells (Hecht et al, 1999;Soma et al, 2006;Liu et al, 2007;Lin et al, 2010;Huang et al, 2011). NNK is a key ingredient of tobacco smoke carcinogens.…”

SSBP2 Variants Are Associated with Survival in Glioblastoma Patients

“…As further evidence of the biologic plausibility of these findings, SSBP2 has been reported to be involved in the maintenance of genome stability (29) and has been implicated in transcriptional signatures in several cancers including leukemia, (30) pancreatic cancer, (31) oligodendroglial tumors, (32) and esophageal squamous cell carcinoma. (29) A direct confirmation of the link between SSBP2 and survival in brain cancer is further proffered by Shaw et al, (32) in which the expression of SSBP2 was shown to be associated with response to chemotherapy in patients with oligodendroglial tumors.…”