An innovative nuclear antigen-based approach for single-cell isolation of circulating tumor cells in adrenal cortical carcinoma

Adrenal cortical carcinoma (ACC) is a rare and aggressive endocrine tumor that originates from the adrenal cortex. Radical tumor resection remains the most effective therapy since survival dramatically drops when metastases are present at diagnosis. Hence, there is an urgent need for reliable biomarkers to enable early diagnosis, monitor minimal residual disease (MRD), and assess chemotherapy response. Circulating tumor cells (CTCs) detected via blood liquid biopsy may represent a valuable oncological marker in ACC patients. However, CTC isolation methods so far applied to ACC patients lack specificity, reproducibility and standardization, thus preventing the potential application of CTCs in the management of these patients. In this study, we present a novel method for the specific and reproducible detection and analysis of single CTCs in ACC patients. This approach combines size- and mechanical property-based enrichment via the Parsortix® system with immunofluorescent detection and isolation of single CTCs using DEPArray® technology, targeting the steroidogenic factor-1 (SF1) nuclear adrenal cortex marker. Isolated CTCs undergo low-pass copy number alteration (CNA) analysis. This is the first report of a nuclear antigen-based method for isolating single CTCs in suspension, overcoming the limitations of membrane and cytokeratin markers commonly used in other solid tumors. By exploiting the large nuclear size of CTCs, this strategy provides an alternative and more standardized approach for single-cell isolation in tumors lacking specific surface markers.