Overexpression of DLC-1 induces cell apoptosis and proliferation inhibition in the renal cell carcinoma

The lack of effective anti-tumor therapy for renal cell carcinoma (RCC) has stimulated the search for novel target whose inhibition could block tumorigenesis. Recently, reduced DLC-1 has been shown to be associated with aggressive and highly metastatic renal cell carcinoma. In this study, the biological role of DLC-1 on cell growth, migration and cell cycle progression in RCC cells was investigated. Over-expression of DLC-1 was associated with a marked inhibition of cell growth (P < 0.01). The inhibitory effect was partly due to the induction of apoptosis and cell cycle arrest in G0/G1 accompanied by up-regulation of the intracellular signal proteins of p27 and down-regulation of cyclin D1 and cyclin E. Furthermore, DLC-1 induced FAK dephosphorylation of focal adhesion proteins inhibited cell migration (P < 0.05). Decreased DLC-1 expression strongly correlated with proliferative activity, as indicated by the elevated levels of Ki67. Restoration of DLC-1 expression in RCC cells led to Bcl-2 and caspase-3 mediated apoptosis as well as attenuated the ability of the cells to form RCC tumors in athymic nude mice (P < 0.05). Taken together, these results suggest that DLC-1 plays a crucial role in signal transduction pathway regulating the cell proliferation, migration, and carcinogenesis of human RCC.