Apoptosis, including Ca2+-induced apoptosis, is known to occur by both capspase-dependent and -independent mechanisms.36 In addition, Ca2+ elevation activates a variety of targets involved in mediating Ca2+-induced cell death.36 Ca2+-induced apoptosis in certain cell types is mediated by members of the calpain family of Ca2+-activated cysteine proteases.36, 40 Here we find that the calpain inhibitor PD150606 inhibits BIRD-2 induction of apoptosis in SCLC cells. Here, CTSB is linked to small cell lung carcinoma.