Single Nuclei Sequencing Reveals Intratumoral Cellular Heterogeneity and Replication Stress in Adrenocortical Carcinoma

Adrenocortical carcinoma (ACC) is a rare endocrine malignancy with a poor prognosis and limited treatment options. Bulk genomic characterization of ACC has not yielded obvious therapeutic or immunotherapeutic targets, yet novel therapies are needed. We hypothesized that elucidating the intratumoral cellular heterogeneity by single nuclei RNA sequencing analyses would yield insights into potential therapeutic vulnerabilities of this disease. In addition to characterizing the immune cell and fibroblast landscape, our analyses of single nuclei gene expression profiles identified an adrenal cortex cell cluster exhibiting a program of replication stress and DNA damage response in primary and metastatic ACC. In vitro assessment of replication stress and DNA damage response using an ACC cell line and a series of newly-derived hormonally active patient-derived tumor organoids revealed ATR sensitivity. These findings provide novel mechanistic insight into ACC biology and suggest that an underlying dependency on ATR may be leveraged therapeutically in advanced ACC.