Abstract 1345: Interleukin-4 promotes cancer cell proliferation through the activation of the p38-mitotic activated protein kinase (MAPK) signaling pathway

Abstract

Abstract Introduction There is increasing data supporting the idea that tumor cells take advantage of the signaling molecules of the immune system to proliferate, survive, and invade other tissues. The cytokine, interleukin (IL)-4 plays a critical role in the regulation of immune responses and has been observed at high levels in the tumor microenvironment and in the peripheral blood mononuclear cells of cancer patients, correlating with the grade of malignancy. IL-4 has been associated with increased cell survival in tumor development; however, its effect on cancer cell proliferation has not been thoroughly explored. Here we investigated the signaling pathways activated by IL-4 that induce cancer cell proliferation. Experimental Procedures Prostate cancer PC3 cells, breast cancer MDA-MB-231 and salivary gland carcinoma A-253 cells were synchronized by serum starvation and plated in media containing 0.5% FBS alone or in combination with IL-4 (100 ng/ml). Proliferation was assessed using the WST-1 cell viability assay (Roche) and the activated pathways were analyzed with phosphospecific antibodies. Proliferation was also evaluated in PC3 cells treated with MAP kinase kinase (MEK1/2) inhibitor, U0126 (10 µM) or p38 MAPK-specific inhibitor, SB 220025 (0.5 µM) (Calbiochem), alone or in the presence of IL-4. Results A time course analysis of cancer cells (PC3, MDA-MB-231 and A-253) stimulated with IL-4 demonstrated an enhanced cell proliferation compared to the untreated cells. To analyze the signaling pathways induced by IL-4 that caused proliferation, PC3 and A253 cells were stimulated with IL-4 and subsequently evaluated by Western blot for the activation of common signaling molecules. It was found that IL-4 significantly enhanced the activation of MAPK/Erk1/2 and the p38 MAPK pathways in both cell types. In contrast, IL-4-dependent activation of Akt signaling was only induced in the PC3 cells. It was further demonstrated that the specific p38-MAPK inhibitor significantly affected the IL-4 induced cell proliferation in PC3 cells. Meanwhile, the MEK1/2 inhibitor (U0126) did not show a significant effect on the proliferation of IL-4 stimulated cells. Inhibition of phospho-p38 by using SB 220025 (0.5 µM) was confirmed by Western Blot. Conclusions Increased levels of IL-4 and phosphorylated p38 have been correlated with malignancy in several cancer types. Our results suggest that hyperactivation of p38-MAPK by IL-4 induces a potent proliferation response in various cancer cells from different origins. In addition to its important role in cancer cell survival, we propose that IL-4 enhances cell proliferation via potent activation of p38-MAPK, which is essential in the neoplastic progression. Currently, investigations are underway to further elucidate the interaction of the p38-MAPK signaling with other pathways that could play a critical role in this mechanism. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1345.