PO-233 DOCK1 as a novel molecular target for controlling cancer cell survival and invasion

Introduction Oncogenic Ras contributes to malignant phenotypes of cancer cells by stimulating nutrient uptake via macropinocytosis and promoting invasive migration. Because these cellular activities require remodelling of the actin cytoskeleton, which is regulated by the Rho family GTPase Rac, molecules involved in Rac activation may be valuable targets for cancer therapy. DOCK1 is a Rac-specific guanine nucleotide exchange factor (GEF) implicated in malignancy of various cancers. Here we examined the effect of interference with DOCK1 function on Ras-driven cancer cell survival and invasion. Material and methods Endogenous expression of DOCK1 in various mouse and human cancer cells harbouring oncogenic Ras mutations was ablated by gene targeting, shRNA expression, and CRISPR-mediated genome editing. Invasive activity was measured by using the Matrigel invasion chambers. Macropinocytic activity was assessed by measuring the cellular uptake of fluorescent dextran. Cell survival was assessed under glutamine-deprived conditions. For in vivo metastasis, cells were injected into the tail vein of C57BL/6 mice. In vivotumour growth was assessed by inoculating cancer cells into the back of BALB/c nude mice. TBOPP, a selective inhibitor of DOCK1 that binds to the catalytic domain of DOCK1 and blocks its GEF activity, was administered into mice intravenously or by using microinfusion pump. Results and discussions Interfering with DOCK1 function by genetic inactivation and pharmacological inhibition markedly suppressed invasion, macropinocytosis, and survival under low nutrient conditions in various cancer cells. Furthermore, TBOPP treatment suppressed cancer metastasis and growth in vivo in mice. Conclusion Our results demonstrate that DOCK1 plays a critical role in malignant phenotypes of Ras-driven cancer cells. Thus, selective inhibition of DOCK could be an effective approach to target cancer cell survival and invasion.