Interferon-alpha suppresses the antiapoptotic effect of NF-kB and sensitizes renal cell carcinoma cells in vitro to chemotherapeutic drugs

Background Immunochemotherapy (ICT) with interleukin-2 (IL-2) and interfero n-alpha (IFN alpha) with a secondary effector (5-fluorouracil, 5 FU) is the only promising treatment for advanced renal cell carcinoma (RCC). With IFN alpha, besides the activation mechanisms of the immunosystem, a direct ant itumor effect on tumor cells is expected. Materials and Methods: NF-kappaB activity in th ree permanent cell lines (H ep2, HepG2, HT29) and in primary RCC cell lines was measured after incubati on with tumor necrosis factor-alpha (TNF alpha), IFN alpha, IFN-gamma, TNF alpha +IFN alpha, and IFN gamma +TNF alpha, respectively. NF-kB activity an d induction of apoptosis by chemotherapeutic drugs (5FU and doxorubicin) we re determined in cells transfected with a constitutively active NF-kB p65 o r a dominant negative IkB. Results: NF-kB signaling induced by TNF alpha is suppressed by IFN alpha an d IFN gamma in the permanent cell fines and in the primary RCC tumor cell c ultures. In an in vitro ICT model we show that pretreatment of RCC with IL- 2 and IFN alpha leads to a diminished NF-kB response to TNF alpha. In certa in tumors, this correlates with increased susceptibility to investigated ch emotherapeutic drugs as shown by annexin stain and cell elimination. Modula tion of the cellular NF-kB state by a constitutively active p65 or a domina nt negative IkB mimics this effect. The IkB construct leads to the same eff ects as IL-2/IFN alpha pretreatment as shown by predominant elimination of the transfected cells from the overall population, while introduction of p6 5 leads to a partial rescue from the effect of IL-2 and IFN alpha. The desc ribed effect, however, applies only to a selection of primary cell cultures . Conclusions: Besides the immunomodulation effects, treatment of RCC with IL -2/IFN alpha leads to a proapoptotic state in certain tumors. The relevant mediator seems to be IFN alpha by suppression of the antiapoptotic effect o f NF-kB. These data can provide an experimental base for correlation with r eal patient outcome after ICT. Copyright (C) 2001 S. Karger AG. Basel.