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 (IFNalpha) with a secondary effector (5-fluorouracil, 5 FU) is the only promising treatment for advanced renal cell carcinoma (RCC). With IFNalpha, besides the activation mechanisms of the immunosystem, a direct antitumor effect on tumor cells is expected.


METHODS
NF-kB activity in three permanent cell lines (Hep2, HepG2, HT29) and in primary RCC cell lines was measured after incubation with tumor necrosis factor-alpha (TNFalpha), IFNalpha, IFN-gamma, TNFalpha+IFNalpha, and IFNgamma+TNFalpha, 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 TNFalpha is suppressed by IFNalpha and IFNgamma in the permanent cell lines and in the primary RCC tumor cell cultures. In an in vitro ICT model we show that pretreatment of RCC with IL-2 and IFNalpha leads to a diminished NF-kB response to TNFalpha. 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/IFNalpha 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 IFNalpha. The described effect, however, applies only to a selection of primary cell cultures.


CONCLUSIONS
Besides the immunomodulation effects, treatment of RCC with IL-2/IFNalpha leads to a proapoptotic state in certain tumors. The relevant mediator seems to be IFNalpha by suppression of the antiapoptotic effect of NF-kB. These data can provide an experimental base for correlation with real patient outcome after ICT.
Steiner
T
T
Department of Urology, Friedrich Schiller University, Jena, Germany. thomas.steiner@med.uni-jena.de
Junker
U
U
Henzgen
B
B
Nuske
K
K
Durum
S K
SK
Schubert
J
J
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002292:Carcinoma, Renal Cell / Q000188:drug therapy*; D006801:Humans; D016898:Interferon-alpha / Q000494:pharmacology*; D016328:NF-kappa B / Q000037:antagonists & inhibitors*; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D016898:Interferon-alpha; D016328:NF-kappa B