P04.03.A TARGETING SCD TRIGGERS LIPOTOXICITY OF CANCER CELLS AND ENHANCES ANTI-TUMOR IMMUNITY IN BREAST CANCER BRAIN METASTASIS MOUSE MODELS

• Published in: Neuro-oncology (Charlottesville, Va.) Va.), 2024-10, Vol.26 (Supplement_5), p.v42-v42
• Main Authors: Sammarco, A, Guerra, G, Eyme, K M, Kennewick, K, Qiao, Y, El Hokayem, J, Williams, K J, Su, B, Zappulli, V, Bensinger, S J, Badr, C E
• Format: Article
• Language: English
• ISSN: 1522-8517; 1523-5866
• DOI: 10.1093/neuonc/noae144.134

Abstract BACKGROUND Breast cancer brain metastases (BCBM) are a significant cause of mortality and are incurable. Thus, identifying BCBM targets that reduce morbidity and mortality is critical. BCBM upregulate Stearoyl-CoA Desaturase (SCD), an enzyme that catalyzes the synthesis of monounsaturated fatty acids. This finding highlights a potential metabolic vulnerability of BCBM, but the lack of brain-penetrant inhibitors of SCD has precluded their pre-clinical effectiveness. Additionally, increasing evidence suggests that fatty acid homeostasis in immune cells represents a key regulatory node to control inflammation, and manipulation of fatty acid metabolism has significant effects on immune cell functions. In this study, we tested the effect of a brain-penetrant clinical-stage inhibitor of SCD (SCDi), on breast cancer cells and mouse models of BCBM. MATERIAL AND METHODS Lipidomic analyses, qPCR, and western blot were used to study the in vitro effect of SCDi on breast cancer cells. Single-cell RNA sequencing (scRNAseq) was used to explore the effects of SCDi on cancer and immune cells in the tumor microenvironment (TME) in a BCBM mouse model. RESULTS Pharmacological inhibition of SCD markedly reshaped the lipidome of breast cancer cells and resulted in endoplasmic reticulum stress, DNA damage, loss of DNA damage repair, and cytotoxicity. Importantly, SCDi alone or combined with a PARP inhibitor prolonged the survival of BCBM-bearing mice. When tested in a syngeneic mouse model of BCBM, scRNAseq revealed that pharmacological inhibition of SCD enhanced antigen presentation by dendritic cells, was associated with a higher interferon signaling, increased the infiltration of cytotoxic T cells, and decreased the proportion of exhausted T cells and regulatory T cells in the TME. Additionally, interaction analysis between immune cells in the TME revealed that pharmacological inhibition of SCD decreased engagement of immunosuppressive pathways, including the PD-1:PD-L1/PD-L2 and PVR/TIGIT axes. CONCLUSION These findings suggest that SCD inhibition could be an effective strategy to intrinsically reduce tumor growth and reprogram anti-tumor immunity in the brain microenvironment to treat BCBM.