Abstract IA18: Molecular signatures of circulating tumor cells

Circulating tumor cells (CTCs) are shed from primary cancers, as well as from metastatic deposits, into the blood circulation, where they may travel either as single cells or as CTC clusters, facing both mechanical and oxidative stress. Only a small subset of CTCs remain sufficiently viable to initiate metastatic growth upon dissemination to distant organs; their detection in patients with localized invasive cancer may present an opportunity for early detection, while their analysis in advanced cases provides a “whole cell biomarker,” enabling single-cell DNA, RNA, and protein studies, as well as functional drug-sensitivity testing using cultured CTCs. We have applied microfluidic technologies to deplete normal hematopoietic cells from blood specimens of patients with cancer, enhancing the ability of unmanipulated CTCs to proliferate ex vivo and recapitulating features of metastatic-competent cancer cells. Cultured CTCs from patients with either breast cancer or melanoma are highly tumorigenic when injected orthotopically at low inoculum into immunosuppressed mice. However, they display sensitivity to ROS and appear to upregulate compensatory mechanisms that are not commonly observed in primary tumors. In addition, they may undergo prolonged dormancy when lodged within distant organs. By combining single-cell RNA seq of patient-derived CTCs together with CRISPR and other genome-wide screens for modulators of metastasis phenotypes, we have sought to identify novel vulnerabilities in these cellular initiators of metastasis. While CTCs transit only very briefly through the blood circulation, these exceptional conditions may present new therapeutic opportunities to suppress the metastatic recurrence of cancer. Citation Format: Daniel Haber, Xin Hong, Richard Ebright, Doug Micalizi, Aditya Bardia, Ryan Sullivan, Mehmet Toner, Shyamala Maheswaran. Molecular signatures of circulating tumor cells [abstract]. In: Proceedings of the AACR Special Conference on Advances in Liquid Biopsies; Jan 13-16, 2020; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(11_Suppl):Abstract nr IA18.