Abstract

CTC Genetic Diversity Through Single-Cell Analysis and CDX Development

Patrycja PAWLIKOWSKA, Researcher, Gustave Roussy

Tyrosine kinase inhibitors (TKIs) tailored for oncogenic driver alterations have shown unprecedented success in patients harboring EGFR-mutations, ALK- or ROS1-gene rearrangements. However the long-term effectiveness of TKIs is invariably limited by the development of resistance. CTCs are a powerful means to identify genetic alterations predictive of sensitivity or resistance to TKIs, inform on tumor heterogeneity and resistance mechanism, and the characteristics of cancer cells with metastatic potential. Using filter-adapted FISH, we reported ALK-rearrangement detection in CTCs from ALK-rearranged patients and how CTCs with abnormal ALK FISH-patterns monitored on treatment can stratify patients at risk of early-resistance to first-line ALK inhibitor crizotinib. Recently, we developed several workflows enabling to identify resistance mutations to ALK-inhibitors. Individual CTCs were isolated by laser-microdissection of filters, fluorescence-activated cell sorting or the DEPArray, and tested for more than 2000 hotspots in cancer oncogenes and ALK-mutations. Shared mutations between CTCs and tumor biopsies at resistance to crizotinib and lorlatinib (third generation ALK inhibitor) and CTC-private (exclusively present in CTCs) mutations were thoroughly explored (Pailler et al, in revision).

CTC-derived explant (CDX) model are useful tools to explore drug resistance and improve knowledge on the genetic and phenotypical profile of CTCs that seed metastasis. Our team has recently conducted a project to develop and functionally characterize CDXs in two tumors types i.e. NSCLC and prostate cancer (PCa). In PCa, we established and completed the genetic characterization of a CDX model which was found to recapitulate a mechanism of neuroendocrine transdifferentiation and resistance to therapies targeting the androgen receptor pathway (Faugeroux et al., in revision). These results will be presented at the conference.