Development and Characterization of an Orthotopic Pancreatic Ductal Adenocarcinoma (PDAC) Tumor Model for Evaluation of Drug-Combination Nanomedicine and Targeted Therapeutics

Abstract

Pancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest cancers, with a dismal 5-year 10% pancreatic cancer survival rate. The lack of clinically relevant preclinical models that recapitulate the complex tumor microenvironment and metastatic patterns observed in pancreatic cancer patients has hindered the development of effective therapeutic strategies. To address this limitation, this thesis describes the research, development and characterization of a novel PDAC tumor model syngeneic C57BL/6 mice that suitable for evaluation of therapeutic interventions. Mice produced tumor consistently in the pancreas after intraperitoneal (IP) inoculation with Pan02 cell of PDAC origin. With luciferase expressed Pan02-luc cells, time-course studies of this orthotopic pancreatic tumor model, we found that Pan02 cells first localize in the pancreas, invade and grow in the pancreas before metastatically spread to other tissue and organ. The critical role of the inoculation route in determining tumor formation and metastatic patterns was established. Only inoculation of Pan02-luc cells through IP, but not IV route consistently leading to tumor development in the pancreas, followed by metastatic spread to the liver, gastrointestinal tract, and peritoneal wall. Time-course histological analysis revealed dynamic remodeling of the tumor stroma over time, mimicking the desmoplastic reaction observed in human PDAC. To elucidate the homing mechanisms driving Pan02 cell localization to the pancreas focused on evaluating the role of the epidermal growth factor receptor (EGFR) pathway, with flow cytometry experiments confirming EGFR expression on Pan02 cells. The introduction of the luciferase reporter gene did not significantly impact the sensitivity of Pan02 cells to gemcitabine but led to a striking 10-fold decrease in sensitivity to paclitaxel, highlighting the potential influence of genetic modifications on drug response mechanisms. Pharmacokinetic studies revealed that a novel gemcitabine-and-paclitaxel drug-combination-nanoparticle formulation (GT-in-DcNP) significantly improved the exposure and bioavailability of soluble gemcitabine and paclitaxel. Following IP administration in C57BL/6 mice, the study results suggest that the IP route, combined with drug combination nanoparticle formulation referred to as DcNP, may enhance the therapeutic index of gemcitabine-and-paclitaxel combination in the treatment for pancreatic cancer. Future research directions include transcriptomic or proteomic profiling to identify additional therapeutic targets, evaluation of combination therapies targeting multiple signaling pathways, longitudinal studies investigating the tumor microenvironment, mechanistic studies on paclitaxel sensitivity alterations, and preclinical evaluation of the GT-in-DcNP formulation as a novel product for the treatment of pancreatic cancer. This thesis research provides a novel pancreatic tumor model that is simple, robust that mimic many of characteristic of human pancreatic cancer of PDAC origin through a simple IP inoculation of Pan02 PDAC cell in syngeneic mouse. The subsequent investigation of two current chemotherapeutic drugs, gemcitabine and paclitaxel combination presented in DcNP nanoparticles suggest that DcNP nanoparticles may enhance exposure and effectiveness in the treatment of pancreatic cancer based on the newly established Pan02 orthotopic tumor model. Together, the model and novel GT-in-DcNP may offer a clinically relevant platform for advancing the development of novel targeted therapeutic strategies and improving the prognosis of pancreatic cancer.