Targeting Cbx3/HP1γ Induces LEF-1 and IL-21R to Promote Tumor-Infiltrating CD8 T-Cell Persistence

Abstract

Immune checkpoint blockade (ICB) relieves CD8(+) T-cell exhaustion in most mutated tumors, and TCF-1 is implicated in converting progenitor exhausted cells to functional effector cells. However, identifying mechanisms that can prevent functional senescence and potentiate CD8(+) T-cell persistence for ICB non-responsive and resistant tumors remains elusive. We demonstrate that targeting Cbx3/HP1 gamma in CD8(+) T cells augments transcription initiation and chromatin remodeling leading to increased transcriptional activity at Lef1 and Il21r. LEF-1 and IL-21R are necessary for Cbx3/HP1 gamma-deficient CD8(+) effector T cells to persist and control ovarian cancer, melanoma, and neuroblastoma in preclinical models. The enhanced persistence of Cbx3/HP1 gamma-deficient CD8(+) T cells facilitates remodeling of the tumor chemokine/receptor landscape ensuring their optimal invasion at the expense of CD4(+) Tregs. Thus, CD8(+) T cells heightened effector function consequent to Cbx3/HP1 gamma deficiency may be distinct from functional reactivation by ICB, implicating Cbx3/HP1 gamma as a viable cancer T-cell-based therapy target for ICB resistant, non-responsive solid tumors.