Mechanisms of LY6K-NSC243928 action in anti-tumor immune response in triple negative breast cancer

Summary: Triple negative breast cancer (TNBC) is a lethal subtype of breast cancer, which lacks targeted therapies, it affects younger women and has the worst overall survival rate among breast cancer subtypes. Although immune- oncology (IO) has led to a paradigm shift in cancer therapeutics, its effect in TNBC has been modest. There is an urgent need to identify and develop novel, effective and safe approaches to treat TNBC. We and others have shown that the cell surface protein Lymphocyte antigen 6K (LY6K) is heavily expressed in 80% of TNBC clinical samples and that the increased mRNA expression is associated with poor survival outcome in TNBC. LY6K is mostly expressed in testes tissue and LY6K knockout mice remain healthy. R01CA227694, grant allowed us to validate LY6K protein as a therapeutic target in TNBC. We showed that NSC243928 small molecule can bind with LY6K molecule physically and exhibit anti-tumor properties in LY6K-dependent manner. NSC243928 could inhibit tumor progression and offered long-term tumor protection (unpublished). We show that the that the anti-tumor properties of NSC243928 may be associated with anti-tumor immune cell distribution in tumor microenvironment (TME) in vivo and its direct effect on chromatin modulation. The data from R01 resulted in grant of Canadian Patent No. 3082397 and U.S. Patent No. 12,134,601B2, for the use NSC243928 in “LY6K-targetted therapies using small molecules” award. The goal of the revised renewal application is to identify the mode of action underlying NSC24328-LY6K interaction, identify the most effective rationale treatments in combination with NSC243928 for phase 1 clinical trials and Investigational New Drug (IND) filing. The signaling events in cell-extrinsic and cell-intrinsic effects of LY6K and its regulatory mechanisms remains poorly defined. The first knowledge gap is the lack of mechanistic insight in LY6K-NSC243928 induced anti-tumor immune response such as immune cell infiltration, survival and differentiation of anti-tumor immune cells in TME. A second mechanistic gap remains in understanding the direct effect of LY6K-NSC243928 in chromatin remodeling and cell cycle. TGF-β and Aurora B have been known as important oncogenic signaling pathways. LY6K is the first identified cancer cell specific protein which can regulate both TGF-β and Aurora-B kinase, thus LY6K-targeting small-molecule can be powerful anti-cancer agent active only in cancer context due to cell-specific LY6K expression.