Propagated Circulating Tumor Cells Uncover the Potential Role of NFκB, EMT, and TGFβ Signaling Pathways and ICOP1/I in Metastasis

Metastasis is the primary cause of cancer-related deaths, but is poorly understood. Circulating tumor cells (CTCs) seed distant sites are a promising model system for studying metastasis. Unfortunately, CTCs are very rare and there are few methods for efficiently establishing in vitro and in vivo CTC models. We extended our recently published method for routinely establishing CTC cultures from liquid biopsies (blood draws) of breast cancer patients to diverse cancers, i.e., colon, lung, and pancreatic. We also successfully established CTC-derived xenograft (CDX) models from the expanded CTCs. We used these models to identify genomic markers and pathways associated with metastases. Circulating tumor cells (CTCs), a population of cancer cells that represent the seeds of metastatic nodules, are a promising model system for studying metastasis. However, the expansion of patient-derived CTCs ex vivo is challenging and dependent on the collection of high numbers of CTCs, which are ultra-rare. Here we report the development of a combined CTC and cultured CTC-derived xenograft (CDX) platform for expanding and studying patient-derived CTCs from metastatic colon, lung, and pancreatic cancers. The propagated CTCs yielded a highly aggressive population of cells that could be used to routinely and robustly establish primary tumors and metastatic lesions in CDXs. Differential gene analysis of the resultant CTC models emphasized a role for NF-κB, EMT, and TGFβ signaling as pan-cancer signaling pathways involved in metastasis. Furthermore, metastatic CTCs were identified through a prospective five-gene signature (BCAR1, COL1A1, IGSF3, RRAD, and TFPI2). Whole-exome sequencing of CDX models and metastases further identified mutations in constitutive photomorphogenesis protein 1 (COP1) as a potential driver of metastasis. These findings illustrate the utility of the combined patient-derived CTC model and provide a glimpse of the promise of CTCs in identifying drivers of cancer metastasis.