Involvement of TMEM22 overexpression in the growth of renal cell carcinoma cells.

In order to clarify the molecular mechanism involved in renal carcinogenesis, and to identify molecular targets for development of novel treatments of renal cell carcinoma (RCC), we previously analyzed genome-wide gene expression profiles of clear-cell types of RCC by cDNA microarray. Among the transcativated genes, we herein focused on functional significance of TMEM22 (transmembrane protein 22), a transmembrane protein, in cell growth of RCC. Northern blot and semi-quantitative RT-PCR analyses confirmed up-regulation of TMEM22 in a great majority of RCC clinical samples and cell lines examined. Immunocytochemical analysis validated its localization at the plasma membrane. We found an interaction between TMEM22 and RAB37 (Ras-related protein Rab-37), which was also up-regulated in RCC cells. Interestingly, knockdown of either of TMEM22 or RAB37 expression by specific siRNA caused significant reduction of cancer cell growth. Our results imply that the TMEM22/RAB37 complex is likely to play a crucial role in growth of RCC and that inhibition of the TMEM22/RAB37 expression or their interaction should be novel therapeutic targets for RCC.