Identifying and Targeting Drivers of Impaired Translation in Tumor-infiltrating CD8+ T-cells.

PROJECT SUMMARY/ ABSTRACT
Immune checkpoint blockade (ICB), aimed at reinvigorating immune cells such as T-cells, has exhibited clinical
success in a subset of patients yet fails to be applicable to many tumor subtypes. These unresponsive subtypes
upregulate gene signatures associated with amino acid (AA) metabolism and deprivation. However, how AA
deprivation contribute to poor ICB response remains unclear. Upon chronic antigen stimulation, T-cells become
“exhausted”, an alternative differentiation state that entails the loss of cytotoxic effector function and proliferative
capacity. T-cell exhaustion involves extensive transcriptomic and epigenetic remodeling; however, the loss of
cytokine production occurs despite adequate expression of transcripts encoding cytokines, suggesting post-
transcriptional mechanisms of restricting effector function within tumors. The long-term goal is to elucidate the
mechanisms underlying T-cell dysfunction within the tumor microenvironment and leverage these insights to
enhance ICB efficacy. The predoctoral research (Aim 1) will aim to investigate how local AA availability limits
effector function in tumor-infiltrating T-cells. Preliminary data showed that intratumoral T-cells can not engage in
efficient translation and they experience glutamine deprivation in the tumor microenvironment. Elevated
translational demand downstream of chronic T-cell receptor signaling cannot be met when extracellular AAs are
limiting, restricting both global translation rate and cytotoxic cytokine production. Specific Aim 1.1 will seek to
determine how local AA availability impacts the exhausted T-cell proteome. Nascent transcriptomic and
translatomic alterations will be profiled to evaluate the impact of AA limitation on gene-specific translation rates,
followed by ribosomal footprinting assays to identify cell state- and AA-dependent stalling in vivo. Specific Aim
1.2 will investigate the impact of enhancing AA availability on ICB. A broad-spectrum AA transporter will be
overexpressed in T-cells to examine whether it enhances tumor control in response to ICB and overcomes the
immunosuppressive effects conferred by cancer-associated fibroblasts via restricting intratumoral AA availability.
My postdoctoral research (Aim 2) will focus on the role of non-coding RNAs in translational suppression during
terminal T-cell exhaustion. I will profile how T-cell exhaustion impact the expression of non-coding RNAs and
examine whether non-coding RNA subsequently modulates translation and cytokine production. Overall, these
two projects will unveil the distinct mechanisms driving T-cell dysfunction through translational suppression
during early tumor-infiltration and late terminal exhaustion. The research and training plan outlined in this
proposal will be completed with the joint mentorship of Dr. Santosha Vardhana and Dr. Jayanta Chaudhuri at
Memorial Sloan Kettering Cancer Center (MSK). MSK’s top-notch cancer research environment and abundant
resources in conjunction with the support of the Gerstner Sloan Kettering Graduate School will guarantee the
successful completion of the proposed research and career development plans.

Grant Number: 3F99CA294267-01S1
NIH Institute/Center: NIH
Principal Investigator: Yan-Ting Chen