Abstract LB285: Single cell characterization of the adjacent primed tissues and metastatic microenvironment of adrenocortical carcinoma reveals profound molecular and cellular reprograms that dictate metastatic progression and disease outcome

Abstract Metastasis is the strongest predictor of outcome in cancer; and early interventions are needed to alter disease course and patient outcome. Adrenocortical carcinoma (ACC) is a rare adrenal cancer that has high mortality due to high rate of metastasis. The therapeutic options of metastatic-ACC include surgery and combination of chemotherapeutic regimens, but with very poor outcomes. The heterogeneous composition of immune and stromal cells in the metastatic microenvironment (MME) and adjacent primed tissues, and their crosstalk with malignant cells are critical determinants of cancer metastatic progression and response to therapies, which remain poorly understood for ACC. Therefore, to comprehensively characterize ACC-MME and adjacent primed tissues, and to identify global and tissue-specific reprogramming, we performed single cell RNA sequencing of metastatic-ACC and adjacent primed tissues from the liver and lung. Our studies revealed that ACC-MME undergoes aberrant vascularization with global depletion of capillary endothelial cells (ECs) and enrichment for Tip/Stalk-like ECs, which are significantly associated with poor disease outcome. Moreover, ECs in ACC-MME are highly pro-tumorigenic, showing global upregulation of tumor-promoting gene signatures, and key signaling pathways responsible for angiogenesis, proliferation, migration, and immune suppression, as well depletion of effective anti-tumor immune response programs such as antigen presentation and interferon gamma signaling. Furthermore, there is a major shift in tissue-specific and universal myeloid populations in ACC-MME and adjacent primed tissues, exhibiting global enrichment of dysfunctional DCs and immunosuppressive macrophages, and liver specific pDCs in MME, whereas, MDSCs are broadly enriched in both MME and adjacent primed tissues suggesting these primed for metastasis environments are immune suppressive. CD8 T-cells in ACC-MME express a dysfunctional gene signature, showing downregulation of key effector function genes. We also found an enrichment of immunosuppressive CD4-T-regs in ACC-MME that represent dysregulation of immune checkpoint molecules including CTLA4 and LAG3. Finally, immune and stroma cell populations in ACC MME and adjacent primed tissues show a commonality in reprogramming, favorable for tumor growth and metastasis, across diverse cell and tissue types in comparison to normal tissue samples. Taken together, these findings suggest that ACC-MME and its adjacent primed tissue microenvironments are reprogrammed to immunosuppressive and tumor-promoting states that orchestrate metastasis of ACC. Citation Format: Mohd Omar Faruk Sikder, Vishaka D. Gopalan, Sridhar Hannenhalli, Rosandra N. Kaplan. Single cell characterization of the adjacent primed tissues and metastatic microenvironment of adrenocortical carcinoma reveals profound molecular and cellular reprograms that dictate metastatic progression and disease outcome [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB285.