Aberrant Methylation of the 1p36 Tumor Suppressor Gene RIZ1 in Renal Cell Carcinoma.

ABSTRACT

BACKGROUND: Retinoblastoma protein-interacting zinc finger gene 1(RIZ1) functions as a tumor suppressor. Hypermethylation-mediated RIZ1 silencing has been reported in several cancers, but not in renal cell carcinoma (RCC) yet. MATERIALS AND METHODS: We examined the RIZ1 expression and methylation in a panel of RCC cell lines and 50 primary tumors using semiquantitative/quantitative polymerase chain reaction (PCR), methylation specific PCR, and bisulfite sequencing genomic. We also explored the relationship between methylation status of RIZ1 and clinicopathological features in RCC patients. RESULTS: RIZ1 expression was down-regulated or lost in OS-RC-2, 769-P, Caki-1, 786-O and A498 RCC cell lines. Restored expression of RIZ1 was detected after addition of 5-aza-2'-deoxycytidine with/without trichostatin A, suggesting that DNA methylation directly mediates its silencing. The RIZ1 expression was significantly reduced in RCCs compared to adjacent non-malignant renal samples (P<0.001). Aberrant methylation was detected in 15 of 50 (30%) RCCs and in 2 of 28 (7%) adjacent non- malignant renal samples (P=0.02). No statistically significant correlation between methylated and unmethylated cases with regard to age, gender, pathological stage and grade was observed. CONCLUSIONS: RIZ1 expression is down-regulated in human RCC, and this down-regulation is associated with methylation. RIZ1 methylation may play a role in renal carcinogenesis.