Promoter methylation assay of SASH1 gene in breast cancer.

PURPOSE To analyze the relationship between the expression of SASH1 and its methylation level of SASH1 gene promoter in human breast cancer. METHODS Expression levels of SASH1 were examined in breast cancer tissues and adjacent normal tissues with immunohistochemistry and with real time PCR (RT-PCR) methylation analysis was performed with MassArray. RESULTS Immunohistochemistry showed that SASH1 expression was strongly reduced in breast cancer compared with adjacent normal tissues. Quantitative methylation analysis by MassArray revealed that CpG sites in SASH1 promoter shared similar methylation pattern in tumor tissue and adjacent normal tissue. The CpG sites with significant difference in methylation level were CpG_26.27 and CpG_54.55. Moreover, 5-aza-2'-deoxycytidine (5-Aza-dc) treatment of tumor cell line MDA-MB-231 caused significant elevation of SASH1 mRNA. CONCLUSION Based on these data, we propose that increase of DNA methylation level in the promoter region of gene SASH1, particularly CpG_26.27 or CpG_54.55 sites, possibly repressed SASH1 expression in breast cancer.