Document Type

Dissertation - Open Access

Award Date

2024

Degree Name

Doctor of Philosophy (PhD)

Department / School

Pharmaceutical Sciences

First Advisor

Joshua J Reineke

Abstract

Pancreatic cancer is one of the deadliest cancers to treat. The primary cause for the drug resistance is the dense extracellular matrix (ECM) that surrounds the tumor and restricts blood supply. Gemcitabine (GEM) and paclitaxel (PTX) are drugs that are clinically used in the treatment of pancreatic cancer. GEM, however, is rapidly metabolized by cytidine deaminase (CDA) and eliminated from the body, and paclitaxel is a substrate for P- glycoprotein (P-gp) efflux receptors. Drug delivery using nanoparticles has been reported to help improve drug half-lives and bypass efflux receptors. This thesis aims to encapsulate PTX in PLGA nanoparticles (PTX-NP) and evaluate it along with GEM and stearoyl gemcitabine (St.GEM) in monolayer cell cultures and desmoplastic 3D co-culture model, with a focus on the responsiveness of the ECM. We also aim to understand the effects of PTX-NP by correlating drug release, toxicity, and cellular pharmacokinetic profiles with the PTX-NP’s degradation data. Lastly, we aim to evaluate our collaborators pH sensitive polymersomes in the co-cultures. PTX-NP had a particle size of ~242nm and an encapsulation efficiency of ~92%, an incomplete drug release in non-sink conditions and burst release under sink conditions. Cytotoxicity was highest for PTX-NP, followed by PTX, St.GEM and GEM. Except in BxPC-3 cells, synergy was seen when PTX or PTX-NP were dosed first followed by GEM or St.GEM. GEM’s cytotoxicity was independent of CDA expression. In 3D cultures, PTX and PTX-NP resulted in debris formation from the spheroids. The ECM was found to be responsive to therapy, with collagen showing a rise and fall in response to increasing GEM concentrations. Fibronectin seemed most susceptible with a consistent fall in intensity with rising drug concentration. Cellular pharmacokinetics was evaluated for PTX and showed a mass balance between unabsorbed extracellular and absorbed intracellular concentration, indicating P-gp involvement is unlikely. In spheroids, PTX-NP shows efficacy despite incomplete drug release. The pH sensitive polymersomes exhibited dose dependent toxicity to the spheroids. Overall, our findings demonstrate ECM sensitivity and call for more work exploring the feasibility of fibronectin as a future drug target to examine its potential in treating pancreatic cancer.

Publisher

South Dakota State University

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Rights Statement

In Copyright