Pyrrolidine dithiocarbamate inhibits NF-κB activation and enhances TNF-induced apoptosis in human breast cancer cells

Objective: To determine whether pyrrolidine dithiocarbamate(PDTC) enhances TNFα-induced apoptosis in cultured breast cancer cells and explore the role of NF-κB in TNFα-induced apoptosis. Methods: Human breast cancer cell lines MCF-7 and MDA-MB-435s were treated with TNFα, PDTC and combination therapy. Cell survivals were determined by MTT assay. Apoptosis was detected by TUNEL and flow cytometry. NF-κ B DNA binding activity was detected using electrophoresis mobility shift assay (EMSA). Western blots were performed to demonstrate IκBα(Inhibitor protein of nuclear factorκB) phosphorylation and degradation. Results: Cell growth was not suppressed by either TNFα(2000 U/ml or less) or PDTC alone. Both cell lines treated with TNFα (2000 U/ml) combined with PDTC(50 µmol/L) showed significant growth inhibition. PDTC inhibited TNFα-induced IκBα phosphorylation and degradation in both cell lines. EMSA showed that PDTC continuously inhibited TNFα induced NF-κ B DNA binding activity. TNFα induced apoptosis (TUNEL) was increased significantly when both cells were pretreated with PDTC, and this was confirmed by Flow cytometry. Conclusion: PDTC enhances TNFα-induced apoptosis via inhibiting IκBα phosphorylation and degradation in human breast cancer cells. NF-κ B protects against TNFα-induced apoptosis.