Enhancement of IL-2-Induced Cytotoxicity by Interferon-α in Renal Cell Carcinoma
Metastatic renal cell carcinoma (mRCC) treatment consists of molecular targeted agents and cytokines that have fundamentally different mechanisms of action. Clinical responses also differ; complete response is rare with molecular targeted agents but is sometimes achieved with cytokine
therapies. Because of the relatively high efficacy of combination therapy with low-dose interleukin-2 (IL-2) and interferon-α (IFN-α) against mRCC, it is important to reevaluate cytokine therapies in vitro. Here, we show that when IL-2 is administered in combination with IFN-α,
a stronger cytotoxic effect of PBMCs on RCC cell lines is observed than when IL-2 is administered alone. The upregulation of TNF-related apoptosis-inducing ligand on NK cell by IL-2 and suppression of regulatory T cells (Tregs) by IFN-α were recognized at the same time when cytotoxicity
of peripheral blood mononuclear cells (PBMCs) was enhanced. IL-2 is known to activate natural killer cell cytotoxicity; however, IL-2 also stimulates Treg expansion, which enhances immunosuppression. On the other hand, IFN-α negatively regulates Treg cells, thereby increasing the function
of immune effector cells. Our in vitro results may explain, at least in part, the clinical efficacy of combination low-dose IL-2 and IFN-α therapy against mRCC.