Abstract SY31-04: Uncovering targetable dependencies of latent brain metastatic cells

Abstract

Abstract Uncovering Targetable Dependencies of Latent Brain Metastatic Cells Srinivas Malladi, Department of Pathology, Harold C. Simmons Comprehensive Cancer Center, UT Southwestern Medical Center, Dallas, TX, 75390, USA ABSTRACT HER2+ breast cancer patients presenting with brain metastases have poor survival outcomes. Metachronous brain metastases or relapse are observed in approximately fifty percent of HER2+ breast cancer patients considered disease free after a variable length of time post primary diagnosis and treatment. Disseminated latent residual cells that survive current therapies are responsible for these relapses or metachronous metastasis. How disseminated tumor cells survive as latent/dormant entities for extended period before initiating metachronous metastasis is poorly understood. Moreover, the basis for disparate metastatic fitness among disseminated tumor cells of similar oncotype within a distal organ is unknown and vital for better clinical management. Through a phenotypic screen in mice, we have isolated HER2+ latent (Lat) and brain metastatic (BM) cells.Transcriptomic and metabolic profiles of these brain-tropic breast cancer cells identified actionable dependencies and unique therapeutic opportunities. Brain-tropic Lat and metastatic cells have distinct metabolic profiles that determine their metastatic fitness. Both latent and metastatic cells survive in equilibrium with innate immune surveillance, oxidize glutamine and maintain cellular redox homeostasis through the anionic amino acid transporter xCT. Likewise, xCT expression was significantly higher in matched metachronous brain metastatic samples compared to primary tumors from HER2+ breast cancer patients. Genetic or pharmacological blockade of xCT eradicates residual disease and brain metastatic relapse in these preclinical models. Lactate secreted by aggressive metastatic cells limits innate immune surveillance and triggers overt metastasis. Furthermore, transcriptomic analysis identified augmented AXL expression. Depleting or inhibiting AXL in these HER2 targeted therapy resistant brain-tropic cells attenuates metastatic incidence. In sum, by investigating phenotypically distinct brain-tropic latent and metastatic cells, we uncovered the impact of metabolic diversity and adaptations on metastatic fitness and identified targetable vulnerabilities. Citation Format: Srinivas Malladi. Uncovering targetable dependencies of latent brain metastatic cells [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 SY31-04.