Western blot analysis was performed by standard methods as previously described29 (link). The antibodies against BCL-2, BCL-XL, MCL-1, BAX, BAK, cleaved caspase 3, cytochrome c, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), Akt, p-Akt, and β-tubulin were purchased from Cell Signaling Technology. The antibodies against PARP, BIM, p53, MDM2, and PUMA were purchased from Santa Cruz Biotechnology (Santa Cruz, CA, USA). The antibody against BTK was purchased from ImmunoWay Biotechnology (JiangSu, China). The secondary anti-mouse and anti-rabbit antibodies were purchased from Santa Cruz Biotechnology. Antigen–antibody complexes were detected using Bio-Rad Clarity western ECL substrate, and protein level was quantified by ImageJ (Bio-Rad Laboratory, Hercules, CA, USA).