Analysis of Single Circulating Tumor Cells in Renal Cell Carcinoma Reveals Phenotypic Heterogeneity and Genomic Alterations Related to Progression.

Circulating tumor cells (CTCs) are promising biomarkers for prognosis, therapeutic response prediction, and treatment monitoring in cancer patients. Despite its epithelial origin, renal cell carcinoma (RCC) shows low expression of epithelial markers hindering CTC-enrichment approaches exploiting epithelial cell surface proteins. In 21 blood samples serially collected from 10 patients with metastatic RCC entering the TARIBO trial, we overcame this limitation using the marker-independent Parsortix™ approach for CTC-enrichment coupled with positive and negative selection with the DEPArray™ with single cell recovery and analysis for copy number alterations (CNA) by next generation sequencing NGS. Two CTC subpopulations were identified: epithelial CTC (eCTC) and non-conventional CTC (ncCTC) lacking epithelial and leukocyte markers. With a threshold ≥1CTC/10 mL of blood, the positivity rates were 28% for eCTC, 62% for ncCTCs, and 71% considering both CTC types. In two patients with detectable eCTCs at baseline, progression free survival was less than 5 months. In an index case, hierarchical structure by translational oncology (TRONCO) identified three clones among 14 CTCs collected at progression and at baseline, each containing cells with a 9p21.3loss, a well-known metastasis driving subclonal alteration. CTCs detection in RCC can be increased by marker-independent approaches, and CTC molecular characterization can allow detection of subclonal events possibly related to tumor progression.

International journal of molecular sciences. 2020 Feb 21*** epublish ***

Vera Cappelletti, Elena Verzoni, Raffaele Ratta, Marta Vismara, Marco Silvestri, Rosanna Montone, Patrizia Miodini, Carolina Reduzzi, Melanie Claps, Pierangela Sepe, Maria Grazia Daidone, Giuseppe Procopio

Biomarker Unit, Department of Applied Research and Technological Development, Fondazione IRCCS Istituto Nazionale Tumori di Milano, 20133 Milano, Italy., Department of Medical Oncology, Fondazione IRCCS Istituto Nazionale Tumori, 20133 Milano, Italy., Clinical Trial Center, Fondazione IRCCS Istituto Nazionale Tumori, 20133 Milano, Italy.