G proteins and their regulators (RGS proteins) are known to modulate cell growth and proliferation via complex signaling mechanisms. In order to obtain a better understanding of how these proteins affect tumor formation and progression, specific RGS proteins will be overexpressed in mammalian cell lines or their expression in cancer cells knocked down by siRNA, and the growth characteristics of these cells will then be determined. Changes in the ability of these cells to proliferate in culture will be correlated to alterations in G protein signaling where appropriate.