Author ORCID Identifier

https://orcid.org/0000-0001-8445-8948

Date of Award

Fall 9-11-2024

Document Type

Thesis (Ph.D.)

Department or Program

Microbiology and Immunology

First Advisor

Steven Fiering

Abstract

Cancer is a disease in which normal cells have become altered such that they divide uncontrollably, ultimately leading to tissue destruction. While efficacious cancer therapies have been developed in recent decades, many of them come with drawbacks such as cost and systemic toxicity. Additionally, solid tumors remain difficult to treat due to the immunosuppressive tumor microenvironment. Intratumoral immunotherapy (ITIT) strives to generate effective antitumor immunity by directly administering immunostimulatory adjuvants into tumors to reverse local tumor-mediated immune suppression and generate systemic immune responses against metastases. Intratumoral immunotherapy utilizing in vivo expression of interleukin-12 (IL-12) via plasmid electroporation has been investigated in Phase II clinical trials for metastatic melanoma, yielding minimal clinical results. We sought to improve the efficacy of in vivo IL-12 electroporation via the addition of a CD154 (CD40 ligand)-expressing plasmid, assessing the efficacy against solid tumors. Mice with intradermal B16F10 melanoma or MC38 murine colon carcinoma tumors received 2 weekly intratumoral (IT) injections of plasmids encoding IL-12 and/or CD154, followed by in vivo electroporation. The addition of CD154 to IL-12 was superior to IL-12 alone, resulting in frequent tumor clearance of treated tumors. Tumor clearance coincided with an increase in total CD8 T cells as well as tumor-specific CD8 T cells in the tumor. This expansion of the CD8 T cell compartment corresponded with a drastic reduction in T regulatory cells in the tumor microenvironment, shifting the ratio of CD8 to Tregs in the TME. Tumor treatment responses were abrogated in mice which lack type I conventional dendritic cells (BatF3 KO) or lack CD8 T cells. These findings highlight the potential of adding CD154 and other plasmid combinations to revitalize interest in IL-12 electroporation as a therapeutic platform.

Original Citation

Ho, G.W. (2024) Efficacy and Mechanism of Action of CD40 Ligand and Interleukin-12 Plasmid Electroporation Intratumoral Immunotherapy. PhD thesis. Dartmouth College

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