BCL2 and renal cell carcinoma: In the intrinsic apoptosis pathway, pro‐apoptotic proteins of the BCL‐2 family integrate into the mitochondrial outer membrane and oligomerize to form pores, enabling the release of pro‐apoptotic factors from the mitochondrial intermembrane space into the cytosol.[39] Accordingly, cytosolic and mitochondrial fractions were isolated from drug‐treated RCC cells, and the highest cytochrome c release was detected in the DOX/BT2 combination group (Figure 6G, upper panel).