THU493 The Role Of Liver Receptor Homolog1 (LRH-1) In Regulating Breast Cancer Progression By Modulating The Immune Response

Disclosure: Y. Wang: None. N. Krawczynska: None. S. Bendre: None. H. Vidana Gamage: None. A. Nelczyk: None. A. Das Gupta: None. E.R. Nelson: None. Breast cancer is the most common type of cancer and the second leading cause of death among American women. While immunotherapy holds much promise, the current FDA-approved immunotherapies are effective for only a subset of patients lacking expression of estrogen receptor, progesterone receptor and HER2, but positive for PD-L1. Thus, there is strong impetus to develop novel ways to engage the immune system. We have demonstrated that cholesterol metabolism and homeostasis within myeloid cells can either promote or suppress anti-cancer immunity. One of the regulators of cholesterol homeostasis is Liver Receptor Homolog 1 (LRH-1/NR5A2). We have found that elevated LRH-1 expression in breast tumors is associated with an increased survival. LRH-1 is highly expressed in myeloid cells, particularly neutrophils, a major immune population of the tumor microenvironment. Therefore, we hypothesized that LRH-1 plays modulatory roles in myeloid cells, that subsequently impacts breast cancer progression. Specifically, we evaluated the impact of LRH-1 on myeloid cell biology, including NETosis and phagocytosis. Treatment of neutrophils with an agonist of LRH-1, DLPC, resulted in decreased NETosis, a function of neutrophils previously implicated in recurrence and metastasis. Treatment with an antagonist resulted in increased NETosis. Both the agonist and antagonist exhibited dose-depended effects, strongly suggesting that LRH-1 regulates the process of NETosis. Macrophage phagocytosis is an important initial step towards antigen presentation and activation of T cells. Bone marrow derived macrophages treated with the LRH-1 antagonist exhibited decreased phagocytosis activity, in a dose dependent manner. Treatment with the agonist (DLPC) did not alter phagocytosis, but this may be because basal phagocytosis was already very high. Collectively, our data indicate that LRH-1 plays important roles in the regulation of myeloid cell function, including NETosis in neutrophils and phagocytosis in macrophages. Overall, these findings suggest that LRH-1 activity would be beneficial for an anti-cancer immune response, and therefore position LRH-1 as a therapeutic target. Our ongoing studies will assess the role of LRH-1 in other myeloid cell-related functions including efferocytosis, T-cell expansion and differentiation. Presentation: Thursday, June 15, 2023