PROJECT SUMMARY Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal human malignancies, with a five-year survival rate of 10.8%. Lack of efficient strategies to achieve cytotoxic concentrations of chemotherapeutics in the tumor tissue and the tumor's innate resistance to chemotherapy are the significant barriers in improving treatment outcomes for PDAC. Thus, new approaches for tumor-selective delivery of chemotherapeutics can enhance the therapeutic efficacy while minimizing chemotherapy-associated toxicities. Unfortunately, current nanocarrier systems primarily rely on the inefficient passive accumulation in the tumor. Here we propose a new approach for treating PDAC with a combination of a novel histone deacetylase (HDAC) inhibitor, entinostat, and a leading chemotherapeutic agent, oxaliplatin, at their synergistic ratio. The proposed studies will evaluate nanoengineered MSC as a drug delivery platform to selectively accumulate cytotoxic agents in pancreatic tumors. Based on the existing literature and our preliminary findings, we hypothesize that MSCs-mediated tumor- targeted delivery of oxaliplatin and entinostat at their synergistic ratio would significantly reduce pancreatic tumor growth and enhance the efficacy without acute toxicity. To test our hypothesis, we propose the following Aims. Aim 1: Formulate drug-loaded nano-MSCs and determine their cellular efficacy. Our preliminary studies demonstrate a dose-dependent synergistic therapeutic interaction between free oxaliplatin and entinostat in an in vitro model of PDAC. We will encapsulate oxaliplatin and entinostat separately in the surface-functionalized polymeric nanoparticles. Nanoparticles will be characterized for their particle size, surface charge, drug loading, and in vitro drug release. The time- and dose-dependent drug loading capacity of MSCs and drug release rate and mechanism from nanoengineered MSCs will also be evaluated. Also, both nanoparticle formulation and nanoengineering protocols will be optimized to improve the drug loading capacity of MSCs without affecting their native phenotype, viability, or migratory behavior. Finally, we will determine the synergistic ratio of entinostat and oxaliplatin-loaded MSCs to kill PDAC cells. Based on our preliminary results, the working hypothesis for this Aim is that the nanoengineered MSCs will enable sustained release of oxaliplatin without introducing resistance, ensuring enhanced tumor cell killing. Aim 2: Evaluate the effectiveness of nano-MSCs using an orthotopic mouse model of PDAC. First, we will determine the maximum tolerated dose (MTD), pharmacokinetics, biodistribution, acute and subchronic toxicities of nanoengineered MSCs in an orthotopic mouse model of PDAC. Using this optimized dosing strategy, we will determine the therapeutic efficacy of oxaliplatin-loaded nanoengineered MSCs alone and combined with entinostat-loaded MSCs using an orthotopic mouse model of PDAC. We will conduct detailed histopathol...