No abstract

The primary purpose of our work was to characterize the effects of the nuclear receptor TLX (NR2E1) in triple-negative breast cancer (TNBC) in order to evaluate its potential therapeutic value in a subtype of breast cancer that has proven particularly challenging to treat, primarily due to the lack of targeted modes of intervention. Unfortunately, breast cancer continues to be the second deadliest form of cancer among women in the United States. Considering the substantial public health implications, development of new therapeutic strategies for highly aggressive breast cancer subtypes, such as TNBC, is imperative. While the function of nuclear receptors such as the estrogen and androgen receptors has been extensively characterized in cancers of the breast and prostate respectively, due in part to their amenable nature to ligand modulation, it is likely that other nuclear receptors may represent therapeutic targets for these malignancies. Indeed, probing of available clinical datasets demonstrated that nuclear receptor TLX is most highly expressed in basal and estrogen receptor (ER)-negative breast cancer patients, and that ER-negative patients with higher TLX expression had increased relapse-free and overall survival. Therefore, we hypothesized that TLX could influence the pathophysiology of TNBC. Utilizing a stable overexpression model in the TNBC cell lines, MDA-MB-231 and MDA-MB-468, we have shown that TLX can inhibit critical oncogenic properties in the in vitro setting, including proliferation, migration and invasion. Furthermore, xenograft and lung colonization studies demonstrated that TLX continued to exert anti-oncogenic effects in the in vivo environment. In agreement with these results, transcriptomic analysis of TLX-overexpressing cells and xenograft tumors showed that TLX can regulate genes and pathways that are known to play crucial roles in the growth and metastatic dissemination of cancer. As previously published works have identified several putative TLX ligands, our findings demonstrating that TLX functions as an anti-cancer factor in TNBC provides a strong rationale for future research aimed at therapeutically targeting this nuclear receptor. Citation Format: Adam T. Nelczyk, Hashni E. Vidana Gamage, Liqian Ma, Michael T. McHenry, Madeline A. Henn, Mohammed Kadiri, Yu Wang, Anasuya Das Gupta, Natalia Krawczynska, Sisi He, Michael J. Spinella, Erik R. Nelson. Nuclear receptor TLX inhibits cancer cell intrinsic properties required for triple-negative breast cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 820.

Immune checkpoint blockade (ICB) has revolutionized cancer therapy but has had limited utility in several solid tumors such as breast cancer, a major cause of cancer-related mortality in women. Therefore, there is considerable interest in alternate strategies to promote an anti-cancer immune response. We demonstrate that NR0B2, a protein involved in cholesterol homeostasis, functions within myeloid immune cells to modulate the NLRP3 inflammasome and reduce the expansion of immune-suppressive regulatory T cells (Treg). Loss of NR0B2 increased mammary tumor growth and metastasis. Small molecule agonists, including one developed here, reduced Treg expansion, reduced metastatic growth and improved the efficacy of ICB. This work identifies NR0B2 as a target to re-educate myeloid immune cells providing proof-of-principle that this cholesterol-homeostasis axis may have utility in enhancing ICB.

Breast cancer remains the second leading cause of cancer-related deaths among women. In recent years, immunotherapy has been tremendously successful in some metastatic cancers such as melanoma. However, a majority of breast cancer patients do not benefit from existing immunotherapy treatments, leaving many with an unmet need. Although undoubtedly multifactorial, one major obstacle to anti-cancer therapies, is the highly immunosuppressive breast tumor microenvironment. This phenomenon is strongly maintained by myeloid immune cells and immunosuppressive regulatory T cells (Tregs), which hinder anti-tumor immunosurveillance and promote tumor progression. Thus, strategies to ‘re-educate’ myeloid cells to inhibit Tregs is a potentially promising anti-cancer strategy. Mining clinical data, we have found that elevated mRNA expression of the nuclear receptor, NR0B2 within breast tumors is associated with an increased time to recurrence. Single cell RNA-sequencing indicates that NR0B2 is expressed within the macrophage populations of normal breast tissue, and various dendritic cell (DC) types in PBMCs. Overexpression of NR0B2 or activation with a small molecule agonist in murine bone marrow derived macrophages (BMDMs) or DCs resulted in a dichotomous T cell expansion - away from Tregs. Conversely, Treg expansion increased when NR0B2 was knocked-down. Tumor growth was markedly increased in mice lacking myeloid specific NR0B2 expression. We further investigated the downstream targets of NR0B2 mediating this anti-tumor phenotype and identified that NLRP3 inflammasome-IL1β activity is a likely modulator in re-educating myeloid cell-Treg function. Importantly, a putative small molecule agonist decreased established metastatic lesions and increased the efficacy of αPD-L1. Subsequent medicinal chemistry was used to develop a novel NR0B2 agonist with strong anti-metastatic properties when used as a single agent in a preclinical mouse model. Collectively, our data implicates NR0B2 within myeloid cells as a modulator of Tregs, a cell population that has thus far been therapeutically intractable. Therefore, NR0B2 may prove to be a promising therapeutic target to reshape the tumor microenvironment and improve breast cancer immunotherapy. This work was supported by the Era of Hope Scholar Award from the Department of Defense Breast Cancer Research Program grant (BC200206), National Cancer Institute (R01CA234025), and NIH Chemistry-Biology Interface Training Grant (T32-GM136629). Citation Format: Hashni Epa Vidana Gamage, Sayyed Hamed Shahoei, Tiffany Nguyen, Rachel Farmer, Samuel Albright, Erin Weisser, Rafael O. Bautista, Claire P. Schane, Yu Wang, Adam Nelczyk, Liqian Ma, Srishti Tiwari, Anasuya Das Gupta, Shruti Bendre, Lionel Apetoh, Paul J. Hergenrother, Erik R. Nelson. NR0B2 re-educates myeloid cells within the tumor microenvironment: Potential novel strategy for breast cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2358.