Most of the early studies on lung and lymphoid cancers that reported the effectiveness of navitoclax against BCL-2 family protein to induce cell death in SCLC and ALL xenograft models were associated with BCL-2 anti-apoptotic proteins’ expressions, including BCL-2, BCL-XL, BCL-W and MCL-1 (Lock et al., 2008; Shoemaker et al., 2008; Tse et al., 2008). This evidence concerns the gene MCL1 and small cell lung carcinoma.