ABSTRACT
BACKGROUND@#Gene promoter methylation is a major epigenetic change in cancers, which plays critical roles in carcinogenesis. As a crucial regulator in the early stages of B-cell differentiation and embryonic neurodevelopment, the paired box 5 (PAX5) gene is downregulated by methylation in several kinds of tumors and the role of this downregulation in esophageal squamous cell carcinoma (ESCC) pathogenesis remains unclear.@*METHODS@#To elucidate the role of PAX5 in ESCC, eight ESCC cell lines, 51 primary ESCC tissue samples, and eight normal esophageal mucosa samples were studied and The Cancer Genome Atlas (TCGA) was queried. PAX5 expression was examined by reverse transcription-polymerase chain reaction and western blotting. Cell apoptosis, proliferation, and chemosensitivity were detected by flow cytometry, colony formation assays, and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assays in ESCC cell lines with PAX5 overexpression or silencing. Tumor xenograft models were established for in vivo verification.@*RESULTS@#PAX5 methylation was found in 37.3% (19/51) of primary ESCC samples, which was significantly associated with age (P = 0.007) and tumor-node-metastasis stage (P = 0.014). TCGA data analysis indicated that PAX5 expression was inversely correlated with promoter region methylation (r = -0.189, P = 0.011 for cg00464519 and r = -0.228, P = 0.002 for cg02538199). Restoration of PAX5 expression suppressed cell proliferation, promoted apoptosis, and inhibited tumor growth of ESCC cell lines, which was verified in xenografted mice. Ectopic PAX5 expression significantly increased p53 reporter luciferase activity and increased p53 messenger RNA and protein levels. A direct interaction of PAX5 with the p53 promoter region was confirmed by chromatin immunoprecipitation assays. Re-expression of PAX5 sensitized ESCC cell lines KYSE150 and KYSE30 to fluorouracil and docetaxel. Silencing of PAX5 induced resistance of KYSE450 cells to these drugs.@*CONCLUSIONS@#As a tumor suppressor gene regulated by promoter region methylation in human ESCC, PAX5 inhibits proliferation, promotes apoptosis, and induces activation of p53 signaling. PAX5 may serve as a chemosensitive marker of ESCC.
Subject(s)
Animals , Humans , Mice , Carcinoma, Squamous Cell/genetics , Cell Line, Tumor , Cell Proliferation/genetics , Epithelial Cells/metabolism , Esophageal Neoplasms/genetics , Esophageal Squamous Cell Carcinoma/genetics , Gene Expression Regulation, Neoplastic , PAX5 Transcription Factor/genetics , Tumor Suppressor Protein p53/genetics , Xenograft Model Antitumor AssaysABSTRACT
Objective To study the association of ubiquitin carboxyl-terminal hydrolase L1 (UCHL1) promoter region methylation with human esophageal cancer. Methods Promoter region methylation of UCHL1 was dctcctcd by rnethylation specific PCR (MSP) in esophageal cancer cell lines and tissue samples.The expression of UCHL1 was detected by semi-quantitative RT-PCR and Western blot in esophagcal cancer cell lines.5-Aza-2'-deoxycytidine (5-Aza) was applied to reactivate methylated cell lines.ResultsComplete methylation of UCHL1 promoter region was detected in 8 cell lincs (KYSE30,KYSE150,KYSE140,KYSE450,KYSE510,TE3,TE7,TE10).Loss of UCHL1 expression was found in7 cell lines ( KYSE30,KYSE150,KYSE140,KYSE450,KYSE510,TE3,TE7).Reduced expression was found in TE10 cell line. Promoter region hypermethylation was correlated with UCHL1 expression in esophageal cancer cell lines.Re-expression of UCHL1 was induced by 5-Aza treatment in KYSE150 and TE3 cell lines.UCHL1 was frequently methylated in human primary esophageal cancer (74.51％,38/51 ),while no methylation was detected in normal esophageal mucosa (0/10). No association was found between promoter region methylation and age,gender,tumor location,tumor stage or lymph node metastasis.Conclusions UCHL1is silenced by promoter region hypermethylation in human esophageal cancer.Methylation of UCHL1 is frequently happened to primary esophageal cancer and may play an important role in the tumorigenesis.