Sunday, May 11, 2025
5/11/2025
"Post-translational modification of non-histone proteins as a mechanism of pMHC-I neo-ligand generation" - Project Summary Abstract The advancement of cancer vaccines requires a deeper understanding of T cell recognition of malignant vs non-malignant cells. Though the T cell immune repertoire is developmentally regulated by negative and positive selection, T cells capable of recognizing self-proteins do exist and are critical effectors for many cancer immunotherapies. What remains unclear is how CD8+ CTLs elicited against tumor-self proteins are capable of recognizing malignant cells yet remain blind to healthy cells that also express the self-protein. Lack of clarity on this issue may inhibit the advancement of cancer vaccines that target non-mutated, oncogenic, tumor-self proteins. Our long-term goal is a deeper understanding of how tumor-self antigen vaccine elicited CTLs recognize cancer cells but do not recognize normal cells that also express the antigen. Our immediate objective, defining the first critical step toward our long-term goal, is to determine if a difference in malignant and non-malignant cell post-translation modification of a relevant, model tumor-self antigen generates pMHC-I- neo-ligand(s) recognized on cancer cells by vaccine elicited CTLs. We hypothesize that post-translational deacetylation of lysine residues within a relevant, model tumor-self protein naturally differs between malignant and non-malignant cells resulting in the generation of pMHC-I-neo-epitopes on malignant cells. Guided by supportive preliminary data, our hypothesis will be tested with two specific aims: 1) Determine if tumor-self antigen-lysine deacetylation in malignant cells enables recognition by tumor-self antigen vaccine elicited CTLs. Using mass spectroscopy, we expect to define differential acetylation of lysine residues in the relevant, model, oncogenic tumor-self protein D52 expressed in malignant and non-malignant cells. We expect to demonstrate that D52 lysine acetylation effects D52 vaccine elicited CTL recognition of malignant cells resulting in differential CTL discrimination of malignant and non-malignant cells. Using a specific panel of peptides derived from D52, we anticipate that we will define D52 vaccine elicited CTL pMHC-I-neo-epitopes. 2) Determine if tumor-self antigen-lysine deacetylation in malignant cells impacts vaccine induced protective tumor immunity. Using malignant cells incubated with deacetylase inhibitor prior to inoculation into D52 vaccinated mice with monitoring of tumor growth overtime and endpoint assessment of lung metastases, we expect to demonstrate that inhibition of natural deacetylation of D52 in malignant cells impacts pMHC-I- epitopes that are recognized by CTLs possibly resulting in failure of the vaccine to protect against tumor growth and metastases. Impact: The results of this proof of concept project are expected to positively impact the development of more effective next-generation vaccines that target oncogenic tumor-self proteins for the safe treatment or prevention of cancer. Equally important is a deeper understanding of immunotherapy elicited CTLs and malignant, non-malignant cell discrimination that may impact auto-immune-related toxicities as has been reported for immune checkpoint blockade, and may be associated with next-generation vaccines.
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