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 interferon-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 antitumor effect on tumor cells is expected. Materials and Methods: NF-kappaB activity in th ree permanent cell lines (Hep2, HepG2, HT29) and in primary RCC cell lines was measured after incubation with tumor necrosis factor-alpha (TNF alpha), IFN alpha, IFN-gamma, TNF alpha +IFN alpha, and IFN gamma +TNF alpha, respectively. NF-kB activity and induction of apoptosis by chemotherapeutic drugs (5FU and doxorubicin) were determined in cells transfected with a constitutively active NF-kB p65 or a dominant negative IkB. Results: NF-kB signaling induced by TNF alpha is suppressed by IFN alpha and IFN gamma in the permanent cell fines and in the primary RCC tumor cell cultures. 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 certain tumors, this correlates with increased susceptibility to investigated chemotherapeutic drugs as shown by annexin stain and cell elimination. Modulation of the cellular NF-kB state by a constitutively active p65 or a dominant negative IkB mimics this effect. The IkB construct leads to the same effects as IL-2/IFN alpha pretreatment as shown by predominant elimination of the transfected cells from the overall population, while introduction of p65 leads to a partial rescue from the effect of IL-2 and IFN alpha. The described 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 of NF-kB. These data can provide an experimental base for correlation with real patient outcome after ICT. Copyright (C) 2001 S. Karger AG. Basel.

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