KISS1methylation and expression as predictors of disease progression in colorectal cancer patients

AIM: To examine the effect of aberrant methylation of the KISS1 promoter on the development of colorectal cancer (CRC) and to investigate reversing aberrant methylation of the KISS1 promoter as a potential therapeutic target. METHODS: KISS1 promoter methylation, mRNA expression and protein expression were detected by methylation-specific polymerase chain reaction (PCR), real-time quantitative PCR and Western blotting, respectively, in 126 CRC tissues and 142 normal colorectal tissues. Human CRC cells with KISS1 promoter hypermethylation and poor KISS1 expression were treated in vitro with 5-aza-2'-deoxycytidine (5-Aza-CdR). After treatment, KISS1 promoter methylation, KISS1 mRNA and protein expression and cell migration and invasion were evaluated. RESULTS: Hypermethylation of KISS1 occurred frequently in CRC samples (83.1%, 105/126), but was infrequent in normal colorectal tissues (6.34%, 9/142). Moreover, KISS1 methylation was associated with tumor differentiation, the depth of invasion, lymph node metastasis and distant metastasis (P < 0.001). KISS1 methylation was also associated with low KISS1 expression (P < 0.001). Furthermore, we observed re-expression of the KISS1 gene and decreased cell migration after 5-Aza-CdR treatment in a CRC cell line. CONCLUSION: These data suggest that KISS1 is down-regulated in cancer tissues via promoter hypermethylation and therefore may represent a candidate target for treating metastatic CRC.