VAV1-GSS fusion induces targetable RAC1 dependence. (A) VAV1-GSS fusion induces Rac activation in Jurkat cells. (B) Rac activation data summarizing 3 independent experiments as shown in A. (C) RAC1 knock-down abrogates effect of VAV1-GSS fusion on cell growth. (D) Jurkat cells transfected with VAV1-GSS exhibit greater sensitivity to azathioprine than cells transfected with wild-type VAV1 or an empty vector control.