A) RT-PCR analysis of Casp9 splice variants from A549, H838, and H460 cells treated with erlotinib. Clonogenic plate assays of B) A549 cells, C) H838 cells and D) HCC827 cells expressing ectopic Casp9b cDNA, vector control, Casp9b shRNA or control shRNA after 24hr in the presence of erlotinib. Data are mean ± S.E. represented as percent control.