MCL1 and small cell lung carcinoma: SCLC cell lines showed differential dependence on different BCL-2 family anti-apoptotic proteins, with a majority of them depending on BCL-XL (9/20, 45%), while some depended on a combination of BCL-XL and BCL-2 (3/20, 15%), and only a few depended on BCL-2 (2/20, 10%) or MCL-1 (2/20, 10%), as indicated by their sensitivity to these specific inhibitors (Fig. 1b).