Low-dose chemotherapeutic agents regulate small Rho GTPase activity in dendritic cells

Conventional chemotherapy targets dividing tumor cells and might support antitumor immunity by providing tumor antigens from dying tumor cells to antigen-presenting dendritic cells (DCs). Despite emerging evidence to suggest that phagocytosis of dying tumor cells by DCs requires membrane targeting of specific small Rho guanosine triphosphatases (GTPases), nothing is known with regard to the direct effect of chemotherapeutic agents on low molecular weight Rho GTPases in DCs. Prompted by a recent observation that low-dose chemotherapeutic drug paclitaxel could up-regulate DC maturation and function, here we studied putative regulatory roles for various chemotherapeutic agents in modulating small Rho GTPases in DC. Our results demonstrate that different classes of chemotherapeutic drugs at low nontoxic concentrations regulate activity of Rac, RhoA, and RhoE in murine DC, suggesting that small Rho GTPases might serve as new targets for modulating functional activity of DC vaccines or endogenous DCs in various immunotherapeutic or chemoimmunotherapeutic strategies.