The role of RhoG in migration and invasion of glioblastoma cells. (c2017)

Abstract

Metastasis is the movement of a tumor from its original site to a secondary site. The ability of cancer cells to metastasize depends on their motility and actin-rich membrane protrusions. These protrusions and motility are regulated by Rho GTPases. Rho GTPases are 20KD proteins that act as molecular switches. RhoG, our protein of interest, belongs to this family and is known to almost have the same sequence and function as Rac1. Literature states that RhoG is involved in cell motility, actin cytoskeleton, and many signaling mechanisms. Previous studies showed that RhoG plays a role in the invasive behavior of glioblastoma cells. Also, RhoG was found to be overexpressed in many tumor tissues. In this paper, we studied the role of RhoG in migration and invasion of glioblastoma cells. To study the effect of RhoG on motility, cells were transfected either with si-Luciferase or with si-RhoG (oligo 5 and 8). The results show that upon RhoG knockdown, the motility of Snb-19 cells decreased. This characteristic was further elucidated through immunostaining. Here, the cells were knocked down using si-RhoG and stimulated with PMA. Our results showed that the ruffles are RhoG independent and that the inhibition of RhoG forms stress fibers. Invasion assay also showed a decrease in cell invasion when RhoG was knocked down. Similarly, the adhesion assay revealed a decrease in adhesion of Snb-19 cells upon RhoG knockdown. Finally, a pull-down assay was done for the Rho family of GTPases which showed that RhoG downregulates RhoA and Rac1 activation levels. Indeed, RhoG like other previously tested Rho GTPases is involved in cancer metastasis. It does so by positively regulating cell motility and invasion. Further studies need to be done to elucidate the exact function of RhoG on such characteristics.