(A) An equal number of wild type (wt) and B-Raf−/− MEFs depleted or not for RKIP were plated on Day 0, and cells were counted by Hematocyte Counter through Day 6. Columns, mean of triplicate dishes; error bars, SD. *p<0.01. (B) Athymic mice were injected with MEFs (5 x 106 cells) wild type or knock out for B-Raf that were depleted for RKIP (shRKIP), Raf-1 (shRaf-1) or both (shRKIP shRaf-1) by shRNA as indicated in the figure. Allograft size was measured using a caliper after 4 days from the time of injection and volume calculated as described in Experimental Procedures. (C–D) pErk and Ki67 immunoreactivity in the allografts described in panel B. Immunostaining was measured as described in Experimental Procedures. Left Panel: Representative photomicrographs. Right Panels: Quantification of immunohistochemical staining of allografts slices; n=8 for each treatment group; a.u.= arbitrary units. Error bars, S.E. *p<0.05.