Bhlhe40 shapes distinct T cell reponses to anti PD1 and anti CTLA4 immune checkpoint therapy

The transcriptional programs that enable CD4 and CD8 T cells to sustain anti-tumor immunity are not fully defined. We investigated the role of the transcriptional regulator Bhlhe40 in shaping CD4 and CD8 T cell responses during anti-PD-1 and anti-CTLA-4 immune checkpoint therapy (ICT). Using conditional knockout mice, we found that anti-PD-1 efficacy depends on CD8 T cell-intrinsic Bhlhe40, with potential contribution from CD4 T cells. In contrast, anti-CTLA-4 relies primarily on CD4 T cell-intrinsic Bhlhe40 and remains effective even without Bhlhe40 in CD8 T cells. Loss of Bhlhe40 skewed CD8 T cells toward TCF-1+ naïve/progenitor exhausted-like states, impairing IFNgamma production, glycolysis, and mitochondrial fitness. CD8 T cell-intrinsic Bhlhe40 was also required for ICT-driven macrophage remodeling from suppressive CX3CR1 + to iNOS + macrophages. Analysis of human cancer datasets showed that BHLHE40 is enriched in tumor-reactive and activated/exhausted CD8 T cells, correlating inversely with TCF7 (TCF-1) and positively with TOX and IFNG . Importantly, higher BHLHE40 expression was observed in responders to ICT in a cohort of patients with basal cell cancer. Together, these findings show Bhlhe40 is a subset- and therapy-specific regulator of T cell programs, controlling effector differentiation, metabolism, and ICT efficacy, providing a mechanistic basis for the divergent modes of action of anti-PD-1 versus anti-CTLA-4.