NF-κ B mediated apoptosis induced by TNF/IFN-α

最近，我们报道了TNF/IFN-α联合应用抑制人结肠腺癌细胞的体内外增殖。免疫染色和EMSA显示，在人结肠腺癌细胞系RPMI 4788中，与单独TNF相比，TNF/IFN-α强烈激活NF-κB。虽然通过使用NF-κB诱饵抑制活化的NF-κB，在仅用TNF处理后降低细胞活力，但NF-κB诱饵导致TNF/IFN-α处理后细胞活力的恢复。TNF/IFN-α诱导的细胞Caspase-3活性升高，而转染NF-κB decoy后再经TNF/IFN-α处理的细胞Caspase-3活性降低。另一方面，TNF/IFN-α可显著增强Fas的表达，用NF-κB诱饵抑制TNF/IFN-α诱导的NF-κB活化，可降低Fas的表达。TNF/IFN-α和抗FasL抗体处理的细胞活力和caspase-3活性降低。综上所述，我们的研究结果表明，激活NF-κB诱导的TNF和IFN-α之间的串扰是一种新的促凋亡信号，通过增强Fas的表达。我们的观察提供了肿瘤细胞中的第一个证据，表明TNF诱导的NF-κB活化具有抗凋亡功能，可能通过TNF和IFN-α之间的细胞因子串扰而被修饰为促凋亡功能。TNF/IFN-α和FasL可有效诱导肿瘤细胞凋亡，或联合上调FasL可能成为一种具有临床应用价值的肿瘤治疗新策略。

Recently, we reported that TNF/IFN-α combined treatment inhibited the in vitro and in vivo proliferation of human colon adenocarcinoma cells. Immunostaining and EMSA revealed that NF-κB was activated strongly by TNF/IFN-α compared to TNF alone in a human colon adenocarcinoma cell line, RPMI4788. Although inhibition of activated NF-κB, by using a NF-κB decoy, reduced cell viability after treatment with TNF only, NF-κB decoy resulted in recovery of cell viability after TNF/IFN-α treatment. Caspase-3 activity was increased in cells induced by TNF/IFN-α, while suppression of caspase-3 activity was observed in cells transfected with NF-κB decoy and then treated by TNF/IFN-α. On the other hand, Fas expression was strongly enhanced by TNF/IFN-α, and inhibition of TNF/IFN-α-induced NF-κB activation, by using NF-κB decoy, decreased Fas expression. Cell viability and caspase-3 activity decreased in cells treated with TNF/IFN-α and anti-FasL antibody. Taken together, our findings suggest that activated NF-κB induced by the cross-talk between TNF and IFN-α is a novel pro-apoptotic signal acting via enhancement of Fas expression. Our observations provide the first evidence in carcinoma cells indicating that TNF-induced NF-κB activation, which has an anti-apoptotic function, may be modified to a pro-apoptotic function by cytokine cross-talk between TNF and IFN-α. Such actions might be of clinicopharmacological value, where apoptosis of tumor cells could be efficiently induced by TNF/IFN-α and FasL, or up-regulators of FasL in combination might become a clinically applicable new strategy in cancer therapy.