Inhibitory Effects of Interleukin-4 on Human Renal Cell Carcinoma Cells In Vitro: In Combination with Interferon-α, Tumor Necrosis Factor-α or Interleukin-2

Background: Immune cytokines have been shown to play important roles in regulating the growth of neoplastic cells, as well as the function of immune cells. The present study assessed the effects of interleukin (IL)-4 alone, and in combination with recombinant interferon (IFN)-α2b, or with IL-2, or with tumor necrosis factor (TNF)-α on the in vitro proliferation of human renal cell carcinoma (RCC) cell-lines.
Methods: Growth-inhibitory effects of IL-4 alone, and in combination with other cytokines, on three human RCC cell-lines, Caki-1, CURC-II, and A-498, were measured by the [³H]thymidine incorporation assay.
Results: IL-4 inhibited proliferation of all three human RCC cell-lines (P< 0.001). The maximum growth inhibition of RCC cell-lines by IL-4 alone was observed at the concentration of 1 to 3 ng/mL, depending on the cell-line. Antihuman IL-4 antisera was able to reverse the growth-inhibitory effects of IL-4 on Caki-1 in a dose-dependent manner, proving that the growth inhibition was mediated by IL-4 itself. When other cytokines were added in combination with IL-4, only IFN-α2b resulted in significant additional growth inhibition ( P < 0.005). However, when the proliferation was compared to that of RCC cells that were not treated with any cytokine, all combinations produced marked growth inhibition. Conclusion: Our data suggest that IL-4 alone, or in combination with IFN-α2b, can be used to develop new strategies for treatment of human RCC.