Methylation-associated inactivation of LATS1 and its effect on demethylation or overexpression on YAP and cell biological function in human renal cell carcinoma

Large tumor suppressor 1 (LATS1) gene is one of the key factors in Hippo signaling pathway. Inactivation of LATS1 by promoter methylation was found in colorectal cancer (CRC), head and neck squamous cell carcinoma (HNSCC), astrocytoma, breast cancer and it was proved to be a tumor suppressor. However, its role is unclear in renal cell carcinoma (RCC). In this study, the expression of LATS1 was determined by reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry in 30 pairs of RCC tissues and matched normal kidney tissues and RCC cells. We found that the expression of LATS1 was markedly reduced in RCC tissues and cells, in the RCC tissue in 46.7% (14/30), while in the normal kidney tissues in 76.7% (23/30), and was associated with pathological grade and clinical stage of RCC. We detected methylation status of LATS1 by bisulfite sequence-PCR (BSP) in renal cancer cell line 786-O which lowers expression of LATS1, and we found it hypermethylated (in 97.5%). In addition, pharmacological demethylation using 5-Aza-2'-deoxycytidine (5-Aza) restored the expression of LATS1 mRNA and protein in 786-O cells, both LATS1 demethylation and overexpression of LATS1 downregulated the expression of Yes-associated protein (YAP), inhibited cell proliferation, induced cell apoptosis and cell cycle G1 arrest in 786-O cells. Thus, this report for the first time demonstrates the inactivation of LATS1 by promoter methylation and it is a tumor suppressor in kidney cancer. LATS1 may serve as a biomarker for possible early diagnosis and as a potential therapeutic target for human RCC.