A kelch family protein Nd1-L functions as a metastasis suppressor in cancer cells via Rho family proteins mediated mechanism.

The BTB-kelch protein Nd1-L acts as an actin cytoskeleton stabilizer expressed ubiquitously in mouse tissues. We examined the effect of Nd1-L on cancer cell invasion and metastasis. Over-expression of Nd1-L in murine colon carcinoma cell line Colon 26 and murine melanoma cell line B16 resulted in suppression of pulmonary and liver metastasis after inoculation of these cells to syngeneric mice and in increased survival in an animal model. On the other hand, knock down of Nd1-L by RNA interference promoted metastasis ability of these cells. Increased expression of Nd1-L inhibited migration and Matrigel invasion capacity of cancer cell lines in vitro. Thus, Nd1-L expression inversely correlated with invasive and metastasis capacity of cancer cells. Furthermore, increased expression of Nd1-L in NIH3T3 cells inhibited growth factor induced activation of Rho family small GTPases such as Rho, Rac and cdc42. These results suggest that Nd1-L is involved in invasion and metastasis of cancer cells by regulating the actin cytoskeleton and Rho family proteins.