Graduation Date

Spring 5-5-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Programs

Biochemistry & Molecular Biology

First Advisor

Maneesh Jain

Abstract

Pancreatic Cancer (PC) is a lethal disease claiming approximately 45000 lives in the US in 2018, and it establishes an elaborate immunosuppressive tumor microenvironment that aids in disease pathogenesis. Immunotherapy has emerged as a strategy to target tumor cells by reprogramming patient’s immune system. Challenges present in PC immunotherapy are: i) identifying a tumor-associated antigen that could be targeted, ii) identifying adjuvants that could efficiently deliver antigens, iii) eliciting robust anti-tumor responses and iv) overcoming peripheral tolerance and immunosuppression elicited by the tumor.

Firstly, we detected circulating autoantibodies to MUC4 present in PC patients and observed that IgM autoantibodies to MUC4 peptides significantly correlate with overall PC patient survival, thus suggesting that MUC4 could potentially be targeted for PC immunotherapy. Our group is the first to successfully purify recombinant MUC4β protein and characterize its immunogenic activity. We addressed the challenge of protein delivery by encapsulating MUC4β in novel polyanhydride nanoparticles (MUC4 nanovaccine). In the second part of the dissertation, we characterized MUC4 nanovaccine in both in vitro and in vivo system. Our studies showed that MUC4 nanovaccine could robustly activate dendritic cells (DCs) and induce secretion of Th1 cytokines in vitro. High levels of Th1 IgG2b anti-MUC4β antibodies were detected in MUC4 nanovaccine-immunized mice.

As described in the third part of the dissertation, we observed that ex vivo T-cells activated by MUC4 nanovaccine-pulsed DCs showed enhanced cytotoxic killing of miniMUC4 tumor cells, when compared to soluble MUC4β mixed with empty nanoparticles (MUC4+NP). We validated our data in an in vivo subcutaneous PC tumor mouse model, and observed enhanced immune cells infiltration and corresponding levels of necrosis in miniMUC4 tumors corroborated with low tumor volume of miniMUC4 tumor (in comparison to contralateral vector control tumor) in MUC4-immunized mice. Furthermore, the presence of PD-L1 surface expression on miniMUC4 tumor cells indicated active immunosuppression lodged by tumor cells in response to IFNγ-secreting infiltrating cytotoxic T-cells.

Taken together, studies in this dissertation demonstrate that MUC4 nanovaccine could serve as a potential strategy for PC immunotherapy.

Available for download on Saturday, April 27, 2019

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