Causal interaction of HDAC and BCL-2 in survival of TAMR
cells. (A) Tamoxifen-resistant cells derived from MCF7 (TAMRM) cells were treated with increasing doses of ABT.263 in presence of 200 nM PCI-24781 (PCI) or increasing doses of PCI in presence of 1 μM ABT.263 and assayed by western blot for PARP cleavage. (B) MCF7 and TAMRM cells were treated with vehicle (C), 200 nM PCI, 1 μM ABT.263 or the combination for 96 hours and analyzed for cell death. (C) MCF7 and TAMRM cells were transfected with either scramble or a Bcl-2-specific small interfering RNA (siRNA) and extent of knockdown is represented by BCL-2 mRNA levels. (D) Treatment of the transient BCL-2 knockdown MCF7 and TAMRM cells were treated with 200 nM PCI for 72 hours and analyzed for cell death and PARP cleavage. Asterisk (*) indicates significant difference (P value <0.05) whereas (#) indicates insignificant difference (P value >0.05) compared to control group. HDAC, histone deacetylase.