title: DNA promoter hypermethylation contributes to down-regulation of galactocerebrosidase gene in lung and head and neck cancers.
abstract: Galactocerebrosidase (GALC) is a lysosomal enzyme responsible for glycosphingolipids degradation byproducts of which are important for synthesis of apoptosis mediator ceramide. Reduced expression of GALC has been identified in human malignancies; however, molecular mechanisms underlying down-regulation of GALC expression in cancer remain unknown. We performed methylation and expression analysis on GALC gene in a panel of head and neck cancer (HNC) and lung cancer cell lines, attempting to understand the regulation of GALC in human cancer. QRT-PCR and western blot analysis were performed to detect the expression of GALC in HNC. Bisulfite DNA sequencing and real-time qMSP were used to detect the methylation of GALC in HNC and lung cancer cell lines. 5aza-dC treatment assay was used to analysis the functional effect of GALC methylation on GALC expression in HNC. Reduction or complete absence of GALC expression was observed in more than a half of the tested HNC cell lines (8/14). 7 out of 8 cell lines with down-regulated expression harbored heavy CpG island methylation, while all cell lines with abundant expression of the gene contained no methylation. Hypermethylation was also found in primary HNC tumor tissues and lung cancer cell lines whereas absent in normal oral mucosa tissues. Demethylating treatment demonstrated that 5aza-dC significantly restored GALC expression in cell lines with methylated promoter while showed no effect on cell lines without promoter hypermethylation. Our findings for the first time demonstrated that promoter hypermethylation contributed to down-regulation of GALC Gene, implicating epigenetic inactivation of GALC may play a role in tumorigenesis of cancer.
authors.affiliation: The Third Affiliated Hospital of Southern Medical University Guangzhou, P. R. China.
authors.forename: Jiangzhou
authors.initials: J
authors.lastname: Peng
authors.affiliation: Sun Yat-Sen Memorial Hospital of Sun Yat-Sen University Guangzhou, P. R. China.
authors.forename: Baishen
authors.initials: B
authors.lastname: Chen
authors.affiliation: Sun Yat-Sen Memorial Hospital of Sun Yat-Sen University Guangzhou, P. R. China.
authors.forename: Zhuojian
authors.initials: Z
authors.lastname: Shen
authors.affiliation: Sun Yat-Sen Memorial Hospital of Sun Yat-Sen University Guangzhou, P. R. China.
authors.forename: Heran
authors.initials: H
authors.lastname: Deng
authors.affiliation: The Third Affiliated Hospital of Southern Medical University Guangzhou, P. R. China.
authors.forename: Degang
authors.initials: D
authors.lastname: Liu
authors.affiliation: Sun Yat-Sen Memorial Hospital of Sun Yat-Sen University Guangzhou, P. R. China.
authors.forename: Xuan
authors.initials: X
authors.lastname: Xie
authors.affiliation: Sun Yat-Sen Memorial Hospital of Sun Yat-Sen University Guangzhou, P. R. China.
authors.forename: Xiangfeng
authors.initials: X
authors.lastname: Gan
authors.affiliation: Sun Yat-Sen Memorial Hospital of Sun Yat-Sen University Guangzhou, P. R. China.
authors.forename: Xia
authors.initials: X
authors.lastname: Xu
authors.affiliation: Sun Yat-Sen Memorial Hospital of Sun Yat-Sen University Guangzhou, P. R. China.
authors.forename: Zhiquan
authors.initials: Z
authors.lastname: Huang
authors.affiliation: Sun Yat-Sen Memorial Hospital of Sun Yat-Sen University Guangzhou, P. R. China.
authors.forename: Ju
authors.initials: J
authors.lastname: Chen
mesh_terms: D015153:Blotting, Western; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D019175:DNA Methylation / Q000235:genetics*; D015536:Down-Regulation; D005698:Galactosylceramidase / Q000096:biosynthesis* / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D006258:Head and Neck Neoplasms / Q000201:enzymology / Q000235:genetics*; D006801:Humans; D008175:Lung Neoplasms / Q000201:enzymology / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D005698:Galactosylceramidase
keywords: DNA methylation; Galactocerebrosidase; head and neck cancer; lung cancer