Abstract 595: Patterns and dynamics of genome instability drive metastatic activity in non-small cell lung cancer (NSCLC) circulating tumor cell (CTC)-derived xenograft (CDX) models
Authors: Tayoun Tala , Faugeroux Vincent , Oulhen Marianne , Pailler Emma , Deas Olivier , Mezquita Laura , Brulle-Soumare Laura , Cairo Stephano , Scoazec Jean-Yves , Marty Virginie , Aberlenc Agathe , NgoCamus Maud , Nicotra Claudio , Planchard David , Kannouche Patricia , Besse Benjamin , Judde Jean-Gabriel , Pawlikowska Patrycja , Farace Françoise 
Published: July 2021

Abstract
Background: CDX models have emerged as tractable systems to explore mechanisms involved in metastatic progression and tumor-initiating properties of CTCs. However, their development is challenging due to low prevalence of CTCs in patient blood. We report the genomic and functional characterization of 4 NSCLC CDX models and their derived cell lines. We focus on genome and chromosomal instability (CIN) mechanisms operating in the CDX-derived cell lines and decipher relevant therapeutic targets.
Methods: CTCs were enriched from 30mL blood samples of 58 advanced NSCLC patients and implanted subcutaneously into Nod/Scid-IL2Rγ-/- (NSG) mice. Tumors were palpable within a median of 108 days. Among the 4 CDX models established, 3 CDX-derived cell lines (GR-CDXL1, GR-CDXL3 and GR-CDXL4) were obtained. Cell lines were characterized by immunofluorescence (IF), immunohistochemistry and whole-exome sequencing (WES). CIN and DNA damage response (DDR) activity were evaluated using IF and western blot. Tumorigenic potential of CDX-derived cell lines was assessed in the chick embryo chorioallantoic membrane (CAM) and NSG mice engrafted intravenously. IC50 was assessed using CellTiter-Glo®.
Results: All CDX models had an epithelial phenotype. CDX and cell lines recapitulated the corresponding tumor histological features (available for 3 patients). WES revealed multiple copy number alterations (CNAs) in driver genes implicated in diverse genome instability mechanisms. GR-CDXL1 presented BRCA2 mutation and FANCA promoter deletion, while AKT gain was detected in GR-CDXL3 in addition to whole genome doubling. This led us to investigate the DDR in the cell lines. Homologous recombination deficiency and unrepaired DNA damage post-mitosis were observed in GR-CDXL1. GR-CDXL3 presented numerical CIN and centrosome clustering. GR-CDXL4 showed high levels of DNA damage and CIN.
CNA and functional analysis provided a biological rationale for the selection of drug candidates in pharmacological testings on the CDX-derived cell lines. The assays mirrored patients' response to chemotherapy and revealed olaparib efficiency in GR-CDXL1 and GR-CDXL4 cells, which was validated in the CAM. GR-CDXL3 cells were sensitive to phosphoinositide 3-kinase-α inhibitor alpelisib, suggesting tumor dependence on PI3K/AKT pathway. Cell lines were tumorigenic in the CAM and mice. Notably, GR-CDXL3 seeded multiple metastases, which is concordant with its distinguished CIN characteristics and WGD. In ovo and in vivo validation of candidate therapeutic strategies is ongoing and will be presented.
Conclusion: This study reveals distinct genome and CIN patterns operating in our CDX-derived cell lines that may play a critical role in CTC seeding capacity. Our CDX models offer new tools for designing therapeutic strategies targeting metastatic progression in NSCLC.
Citation Format: Tala Tayoun, Vincent Faugeroux, Marianne Oulhen, Emma Pailler, Olivier Deas, Laura Mezquita, Laura Brulle-Soumare, Stephano Cairo, Jean-Yves Scoazec, Virginie Marty, Agathe Aberlenc, Maud NgoCamus, Claudio Nicotra, David Planchard, Patricia Kannouche, Benjamin Besse, Jean-Gabriel Judde, Patrycja Pawlikowska, Françoise Farace. Patterns and dynamics of genome instability drive metastatic activity in non-small cell lung cancer (NSCLC) circulating tumor cell (CTC)-derived xenograft (CDX) models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 595.