Importantly, while BAK displayed similar colocalization coefficients in CLL and RS cells (P = .11), BAX, BIM and BID were less likely to colocalize with mitochondria in RS as compared to CLL (P < 0.0001; Fig. 6B–E), suggesting high-grade cells need a second hit to bring these pro-apoptotic molecules onto the mitochondria for apoptosis induction. The gene discussed is BAK1; the disease is B-cell chronic lymphocytic leukemia.