Patient-derived metastatic models of pancreatic cancer: An in-vivo system for modeling metastasis an preclinical drug screening

Resumen

Although new chemotherapy regimens have shown significant survival improvement in patients with metastatic or locally advanced pancreatic ductal adenocarcinoma (PDAC), metastasis still remains the leading cause of cancer-related mortality. Therefore, discovery of novel metastatic drivers for improvement of therapeutic options against metastasis is of crucial importance. Patient-derived xenografts (PDX) models have become a promising system for studying cancer disease. Orthotopic models have been shown to better mimic the metastatic disease. However, to date, only few PDX orthotopic models of pancreatic cancer have been reported to establish distant metastasis. The metastatic incidence in these models still remains relatively low, therefore development of more efficient and reproducible model for studying metastasis is urgently needed. In this thesis work, we developed several metastatic PDX models of PDAC by orthotopic transplantation of human pancreatic cancer specimens into immunodeficient NOD/SCID/IL2g-receptor null (NSG) mouse. Importantly, these preclinical models develop liver and/or lung metastasis with a high reproducibility rate. We further used these models as an In-vivo platform for isolation of the human tumor populations involved in metastatic process and their posterior functional and single-cell transcriptomic characterization. In-vivo transplantation of the circulating tumor cells (CTCs) showed that they possess high tumorigenic and metastatic potential. Single-cell RNA sequencing analysis revealed that the CTCs cluster separately from their matched primary tumor and metastatic cells, displaying low expression of cell cycle- and ECM-associated genes and enrichment for genes involved in ribosome biogenesis. In addition, CTCs and metastatic cells showed an increased expression of numerous cancer-related genes including Survivin, AURKA, AURKB among others. Moreover, Survivin protein expression was detected in primary tumors and metastatic lesions of all metastatic models. Pre-clinical treatment with YM155 (survivin suppressor) was able to decrease the metastatic tumor burden and showed beneficial effects on survival of the mice bearing metastatic ortotopic tumors. In addition, primary tumor resection in combination with YM155 resulted in significant improvement in median survival of the mice compared with control group. Finally, proteomic characterization of pancreatic cancer exosomes isolated from primary tumors and metastatic organs of PDX models revealed an organ-specific protein signatures with abundant expression of human proteins and some of them were described in the literature to have a role in metastatic organotropism.