Abstract PR13: Interleukin-4 receptor α chain regulates the growth of primary and metastatic mammary tumors

Abstract

Abstract Interleukin-4 (IL-4), a cytokine produced mainly by immune cells, may promote the growth of epithelial tumors by mediating increased proliferation and survival. The IL-4 Receptor (IL-4R) is overexpressed in human and murine epithelial mammary cancers, and may be a promising target for anti-tumor therapy. Here, we show that loss of IL-4Rα, a component of the IL-4 receptor, in two murine mammary tumor cell lines (R221A and 4T1), reduces tumor cell survival and outgrowth ability, and results in attenuated growth at primary and metastatic sites. RNA interference was used to knock down the expression of IL-4Rα in both cell lines. In support of our hypothesis, reduced IL-4Rα expression in R221A cells nearly abolished tumor take after orthotopic mammary injection in vivo, decreased the median latency of 4T1 primary tumors, and resulted in a significant reduction in tumor size at endpoint. In addition, reduced IL-4Rα expression in both cell lines resulted in a decrease [>2.4 fold] in lung and [>2 fold] liver metastatic tumor burden following experimental metastasis assays in vivo. The decrease in metastatic ability of IL-4Rα knockdown cells was attributed to 1) reduced tumor cell survival as determined by seeding ability (number of tumors) and an increase in apoptosis by caspase-3 positivity, and 2) a reduction in proliferation as determined by outgrowth ability (tumor size) and a decrease in Ki67 positivity. In addition, an overall increase in immune infiltrates (macrophages, neutrophils, and T lymphocytes) within IL-4Rα knockdown tumors was observed, indicating that enhanced clearance of knock down tumor cells could also contribute to the reduction in knock down tumor size visualized at endpoint. Finally, it was determined by western blot analysis that IL-4 ligand stimulates the phosphorylation of AKT (s373) and ERK in R221a and 4T1 cells in vitro. Immunohistochemical analysis of R221a and 4T1 lung metastases showed significantly reduced levels of pAKT (s472) and pERK in IL-4Rα knock down tumors compared to control tumors, implicating a possible role for AKT and ERK in mediating pro-tumor effects IL-4Rα signaling. Collectively, our results demonstrate that the IL-4 receptor promotes the growth of mammary cancer cells at primary and metastatic sites, possibly through activated AKT and ERK signaling, and suggests that available drugs targeting IL4-Rα signaling may have potential for treating primary breast cancers and limiting metastatic disease. This abstract is also presented as poster C51. Citation Format: Katherine T. Venmar, Daniel Hwang, Ashley Dozier, Kathy Carter, Sareena Gillani, Barbara Fingleton. Interleukin-4 receptor α chain regulates the growth of primary and metastatic mammary tumors. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr PR13.