HUNK Regulation of Interleukin 4 in Triple Negative Breast Cancer

Abstract

Triple‐negative breast cancer (TNBC) is a type of breast cancer that does not express hormone receptors (estrogen receptor or progesterone receptor) or human epidermal growth factor receptor 2. Therefore, contrary to other types of breast cancer, TNBC is not sensitive to endocrine therapy or HER2 targeted inhibitors. Some new FDA approve as treatments for TNBC include immunotherapy targets such as immune checkpoint inhibitor (ICI). Unfortunately, inadequate anti‐tumor T‐cell effector function and high abundances of tumor‐associated macrophages (TAMs) has limited the efficacy of ICI therapy. TAMs constituted one of the most abundant immune cell population in mammary tumors. Within the tumor TAMS can be polarized to classicallyactivatedM1‐like and alternativelyactiveM2‐likephenotypes.M2‐likemacrophagescontribute to cancer progression by inducing tumor angiogenic responses, promoting tumor growth and metastasis. In cancer the polarization of macrophages toward a M2 phenotype is directed by cancer‐cell derived factors such as pleiotropic cytokines like interleukin‐4 (IL‐4). New knowledge suggests that IL‐4 expression in cancer cells is regulated by the signal transducer and activator of transcription 3 (STAT3) transcription factor. However, it is still undescribed what signaling pathways are responsible for mediating IL‐4 in breast cancer cells. Intriguingly, we observed that Hormonally Up‐Regulated Neu‐Associated Kinase (HUNK), is responsible for IL‐4 production in the 4T1 mammary tumor cell line, which is considered a metastatic TNBC model. We hypothesis that HUNK regulation of IL‐4 drives TAM’s polarization in triple negative breast cancer cells. We engineered4T1 cells expressing HUNK and HUNK knockdown by shRNA. Our current data shown that4T1 cells expressing HUNK, have elevated levels of STAT3 phosphorylation, IL‐4 production and secretion compared to 4T1 cells where HUNK has been downregulated by shRNA. Furthermore, the loss of IL‐4 secretion in 4T1 HUNK knockdown cells corresponds to a reduced ability of conditioned medium from HUNK knockdown cells to induce alternative activation of macrophages. We also observed that HUNK has a significant effect on M2‐likeTAMspresence in the tumor microenvironment, where tumors derived from HUNK knockdown 4T1 cells have reduced TAMs compared to control tumors. Therefore, our results proposed the identification of a HUNK signaling pathway that is responsible for pro‐metastatic TAM function in TNBC. Our study will evaluate HUNK as a therapeutic target for TNBC metastasis by modulating the TAM population within the tumor microenvironment.