Rac1-deficiency delays p53-deficient lymphoma growth in vivo. (A) Total bone marrow from a p53^−/−MxRac1 mouse was isolated and injected (500 000 cells) by tail vein into lethally irradiated (1175 cGy, split-dose) BOYJ recipients. Blood chimerism was assessed 1 month after transplantation and mice containing approximately 90% or greater donor cells received 3 × 300 μg of intraperitoneal PolyIC injections every other day for 4 injections to delete the Rac1 gene in hematopoietic cells in vivo or were mock-injected. Animals were bled monthly to monitor genetic deletion of Rac1 by PCR. Representative PCRs of blood from the same animals 1 month (left panel) or 5 months (right panel) after PolyIC injection are displayed. (B) Survival of animals from panel A are displayed with transgenic p53^−/− and p53^−/−Rac2^−/− animals included. (C) Representative tumors were excised from animals that underwent transplantation from panel A upon death and processed for PCR to assess levels of Rac1 DNA. (D) Tumors from panel C were snap-frozen in liquid nitrogen, lysed, and immunoblotted to determine the expression level of Rac1 protein.