Routes of tumor-specific CD4 T cell elimination of pancreatic cancer

Abstract public domain (NIH RePORTER)

PROJECT ABSTRACT Pancreatic ductal adenocarcinoma (PDA) is the fourth leading cause of cancer related deaths in the United States and has a dismal 5-year survival rate of 12%. Antibody-based immunotherapy shows benefit in a small subset of PDA patients, suggesting that these therapies could be improved to benefit a larger fraction of the patient population. Increasingly recognized as a critical component of antitumor immunity, conventional antigen-experienced CD4 T cells are associated with better prognosis and immunotherapy efficacy. However, the effects of immunotherapy on CD4 T cell fate, antigen-recognition, antitumor function, and immune interactions are poorly understood. As such, this grant seeks to deepen our understanding of tumor-specific CD4 T cell dynamics following immunotherapy with the goal of identifying novel therapeutic opportunities to improve the efficacy of immunotherapy against PDA. Using a novel peptide:MHC II tetramer, my preliminary data indicates tumor infiltrating antigen-specific CD4 T cell numbers, particularly the T helper 1 (Th1) subset, significantly decrease at late tumor growth stages. Treating mice with agCD40 monotherapy or in combination with αPD-L1 restores intratumoral Th1 frequency and decreases immunosuppressive tumor-specific regulatory CD4 T cells (Treg). One consideration is that these preliminary findings are from a CD4 T cell specific to a subdominant epitope. Therefore, for my first Aim, I propose leveraging an anti-PDA CD4 TCR transgenic mouse strain to investigate CD4 T cell phenotype, function, and antigen-recognition following immunotherapy. I generated a Trac-inserted TCR exchange transgenic mouse strain (TrexCB440) where CD4 T cells target a likely immunodominant model neoepitope (CB440) engineered in our KPC PDA cell lines. I will characterize thymic and peripheral CD4 T cells development in TrexCB440 mice to confirm normal lymphocyte development. TrexCB440 will enable the study of tumor-specific CD4 T cell fate, persistence, and polarization in PDA. This strain will be used to determine whether macrophage MHC-II is essential for shaping the CD4 T cell phenotype induced by immunotherapy. Our recently published results suggest CD4 T cell recognition of tumor antigen through tumor-associated macrophages (TAMs) MHC-II drives the antitumor effects of TAMs. Thus, in my second Aim, I will identify the macrophage-CD4 cell-to-cell signals that drive antitumor activity. I will perform physically interacting cell sequencing (PIC-seq) of intratumoral CD4 T cell-TAM doublets to identify CD4 T cell immunotherapy-induced signals that result in macrophage activated phenotype. Finally, I will conduct an in vivo CRISPR gene knockout assay to define specific mechanisms through which immunotherapy induces CD4 T cell tumor control. Successful completion of the proposed research strategy will reveal novel routes by which antigen-specific CD4 T cells contribute to pancreatic tumor control and the longevity of the immunotherapy response.

Public health relevance public domain (NIH RePORTER)

PUBLIC HEALTH RELEVANCE Pancreatic cancer is the 4th leading cause of cancer related deaths in the United States and has a dismal 5- year survival rate of 12%. Pancreatic cancer is refractory to emerging immunotherapy strategies, with only a small subset of patients exhibiting survival in recent clinical trials evaluating chemoimmunotherapy for metastatic disease. This study will provide insight into how immunotherapy fundamentally modulates antitumor immunity in pancreatic cancer, with the ultimate goal of identifying new strategies to improve immunotherapy and benefit pancreatic cancer patients.