Endocrine Abstracts

JOINT894

Adrenocortical carcinoma (ACC) is a rare endocrine malignancy with very poor prognosis due to the lack of successful therapies for patients with metastatic or recurrent tumors. However, the urgent need for the development of new therapies clashes with the lack of preclinical models that accurately represent ACC. Using Cre-loxP technology to mimic inactivation of ZNRF3 and TP53, the most commonly found alterations in ACC patients from the most aggressive subgroup, we developed a new clinically relevant mouse model allowing for the study of the molecular basis of metastatic ACC. Using a combination of Kaplan Meier analysis, bulk RNA sequencing and immunohistochemistry, we demonstrate that adrenal cortex specific ablation of Trp53 and Znrf3 results in development of metastatic and lethal ACC over a 6-month time course. This is associated with other characteristics observed in most aggressive ACC patients, as the molecular signature of C1A subgroup, immune poor, steroidogenic high, and proliferation high signatures or the overexpression of the EZH2 methyltransferase and a constitutive activation on WNT pathway. Single nucleus RNA sequencing of primary tumors showed that acquisition of aggressive features is associated with amplification of a population of proliferative cells characterized by expression of Dab2, Wnt4, Lef1, Mki67, Rad51 and Ezh2. These molecular features are also found in lung metastases, as assessed by both immunohistochemistry and spatial transcriptomic analysis, suggesting that these originate from dissemination of this set of cells. In addition, metastatic dissemination is associated with upregulation of senescence-related signatures. Immunolabeling for P16 and SA-β-galactosidase revealed the presence of senescent macrophages in the most aggressive primary tumors and their corresponding metastases. Single cell transcriptomic analysis of the immune compartment showed that senescent macrophages also express immune-checkpoint and pro-tumoral signatures, suggesting a role for senescent cells in promoting metastatic progression by inhibiting the anti-tumor response. Interestingly, multi-omics analyses of TCGA data have correlated senescence with poor prognosis and survival, highlighting this process as a new ACC therapeutic target. We are therefore currently evaluating the therapeutic potential of senolytics in our ACC mouse model. Altogether, these data shed light on the underpinnings of metastatic dissemination and establish these mice as a good in vivo model to investigate novel therapeutic options.