MD/PhD Student Vanderbilt Univ. Sch. of Med. Nashville, Tennessee, United States
Disclosure(s):
Zachary Ewell: No financial relationships to disclose
Introduction/Rationale: Tumor-specific CD8 T cells (TST) are often dysfunctional and fail to produce IFNγ, a cytokine essential for tumor elimination. How transcriptional and translational mechanisms contribute to this defect remains unclear.
Methods: We analyzed Ifng transcription and translation in adoptively transferred antigen-specific CD8 T cells in acute infection and liver tumors. Using an Ifng fluorescent reporter together with intracellular cytokine staining, we measured Ifng mRNA and protein at the single-cell level by flow cytometry.
Results: Early after antigen encounter, both TST and Listeria-primed effector T cells (Teff) expressed Ifng mRNA. In contrast to Teff, TST did not produce IFNγ protein, suggesting an early translational block. At later time points, Teff rapidly and robustly upregulated Ifng mRNA and IFNγ protein upon antigen restimulation. However, with continued tumor exposure, TST failed to upregulate Ifng mRNA in response to antigen, demonstrating a TST-specific Ifng transcriptional block. Consequently, IFNγ production in TST is impaired at both the transcriptional and translational level. Although the Ifng locus underwent similar chromatin remodeling in TST and Teff upon activation, chromatin accessibility diverged over time, suggesting epigenetic mechanisms may engender the Ifng transcriptional defect.
Conclusion: In future studies, we will epigenetically target the Ifng locus to restore IFNγ mRNA expression and further study and target the Ifng translational block to improve TST IFNγ production. Understanding these regulatory mechanisms in TST will potentially lead to new strategies to strengthen antitumor T cell immunity.
