Triptolide sensitizes human breast cancer cells to tumor necrosis factor-κ-induced apoptosis by inhibiting activation of the nuclear factor-κB pathway

Tumor necrosis factor-alpha (INF-alpha) can act as either a tumor promoter, linking inflammation with carcinogencsis, or a tumor inhibitor, inducing cancer cell death. However, several types of cancer, including breast cancer, are resistant to TNF-alpha therapy. Triptolide, a diterpene triepoxide, has been reported to exert anti-inflammatory and antiproliferative effects, associated with the inhibition of nuclear factor-kappa B-KB (NF-kappa B). The present study investigated the effects of triptolide sensitization on human breast cancer cells to INF-alpha-induced apoptosis by inhibiting activation of the NF-kappa B pathway. Human breast cancer MDA-MB-231 cells and MCF-7 cells were treated with different concentrations of triptolide, with or without 10 ng/mi TNF-alpha, for different durations, followed by measurement of cell proliferation using a 3 44,5-dime thyltiazol-2-y11-2. 5-diphenyl-tetrazolium bromide assay, apoptosis induction, through determination of caspase-3 activity and poly (ADP-ribose) polymerase (PARP) cleavage, and NF-kappa B pathway activation, through determination of inhibitor of NF-kappa B (IKB) and the NF-kappa B downstream genes, X-linked inhibitor of apoptosis protein (XIAP) and cellular inhibitor of apoptosis protein 1/2 (cIAP1/2)] using Western blot and reverse transcription-quantitative polymerase chain reaction analyses. INF-alpha, When combined with triptolide, was observed to inhibit the activation of IKBa, increase the level of cleaved PARP, and further activate caspase-3 in the breast cancer cells. Triptolide also inhibited the expression levels of the downstream anti-apoptotic genes of NF-kappa B activation, XIAP and cIAPIL2. The results of the present study demonstrated that triptolide sensitized human breast cancer cells to INF-alpha-induced apoptosis, which may provide a promising combination strategy for human breast cancer therapeutics.