"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.
