ABT-263 disrupts Bcl-2/Bcl-xl interactions with pro-death proteins (e.g. Bim), leading to the initiation of apoptosis within 2 h post treatment.140 Initial analyses showed that the oral administration of ABT-263 alone induces complete tumor regressions in xenograft models of small cell lung cancer (SCLC) and ALL. This evidence concerns the gene BCL2L1 and small cell lung carcinoma.