Establishing Circulating Tumor Cell-Derived Xenografts Following a Period of in Vitro Culture

Abstract Cancer metastasis—the spread of cancer cells from a primary node to a distant site—is responsible for as much as 90% of all cancer-associated deaths due to treatment resistance and increased tumor burden. Once established, metastatic nodules oftentimes exhibit distinct molecular phenotypes from their original primary tumor, undermining gold-standard methods for determining treatments for patients, which typically rely on molecular characterization of the primary tumor. Unfortunately, a lack of robust, scalable, and appropriate models for studying differences in patient-derived primary and metastatic tumors has hindered progress in identifying metastasis-specific therapies. Previously, we reported the ability to establish in vitro cultures of circulating tumor cells (CTCs), a unique precursor population of cells that exhibits an ability to escape the primary tumor but not yet fully complete metastasis. We have since expanded the application of this GU-CTC platform to culture CTCs from the blood of patients diagnosed with a variety of metastatic cancers, resulting in the successful culture of 31 unique patient-derived CTC cell lines. Furthermore, following an initial short-term culture period, we also performed subcutaneous injection of mixed CTC cultures into immunocompromised mice, resulting in not only primary tumor formation, but also systemic metastatic nodule formation in as short as 3 months. These resulting CTC-derived xenografts (CDXs) have been demonstrated using metastatic pancreatic, colorectal, and lung adenocarcinoma-derived CTCs. Encouragingly, all CDX models also exhibited replicable metastatic patterns upon reimplantation, reinforcing the important role of CTCs as precursors to metastasis. Bulk RNA-sequencing of patient-matched whole blood, cultured CTCs, and CDX-derived primary tumor and metastatic tissues further identified enrichment of an epithelial-mesenchymal transition as well as several cancer-specific gene signatures consistent with an invasive phenotype. This extended GU-CTC platform therefore enables not only the robust and rapid expansion of CTCs through both in vitro and in vivo methods, but also offers an avenue for personalized drug screens in the effort to target cancer metastasis. Citation Format: Jerry Xiao, Richard Schlegel, Seema Agarwal. Establishing circulating tumor cell-derived xenografts following a period of in vitro culture [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5123.