OBJECTIVETo screen methylations of CpG islands in prostate cancer using restriction landmark genomic scanning (RLGS).

METHODSThe DNA was extracted from homogeneous cells captured by laser capture microdissection in 20 prostate cancer and 18 benign prostatic hyperplasia (BPH) tissues for scanning the CpG islands using RLGS. The methylation status of each CpG island was compared between the cancer and BPH samples to screen the genes involved in prostate cancer development. The screened genes were uploaded to DAVID database for GO analysis, and the genes with the most significant methylation were analyzed by pyrosequencing.

RESULTS AND CONCLUSIONAmong all the tested CpG islands, 10245 (37.2%) in prostate cancer and 8658 (30.3%) in BPH samples were found to be abnormally methylated, and >60% of the methylated CpG islands were in the promoter region. Compared with BPH samples, the prostate cancer samples showed differential methyation in 735 CpG islands, including 458 hepermethyated and 256 hypomethelated ones. Seven genes (DPYS, P16, APC, GSTP1, TMEM122, RARB, and ARHGAP20) in prostate cancer were identified to have distinct methylations. Bioinformatics analysis suggested that these genes were associated with several biomolecular and biological processes, and among them DPYS gene was involved in 13 GO anotated biologic functions, development of 50 diseases and 47 protein interactions. Pyrosequencing of 7 sites of the CPG island in DPYS gene showed a methylation frequency of 32.7%, suggesting the importance of DPYS gene in the carcinogenesis and progression of prostate cancer.