The MEK1/2-IRF4 axis fosters T follicular helper cell differentiationand antitumor humoral immune response

Emerging evidence has underscored the significance of antitumor humoral immunity, which is associated with the development of T follicular helper (Tfh) cell. However, the molecular mechanisms underlying Tfh differentiation in antitumor immunity remains poorly understood. We analyzed publicly available RNA-seq data across various representative immune models to identify signature pathways of Tfh cells. Subsequently, we generated T-cell-specific Mek1/2 knockout mice and investigated the functional phenotypes through Tfh cell polarization, adoptive transfer, and flow cytometry assays. Next, we employed multi-omics sequencing and overexpression experiments to delineate the underlying mechanisms of cellular phenotypes. Finally, by integrated analysis of scRNA-seq datasets combined with MEK inhibitor intervention studies, we elucidated the anti-tumor humoral responses of MEK inhibitors in both murine tumor models and TCGA-SKCM patient cohort. Mitogen-activated protein kinase kinase 1/2 (MEK1/2) signaling was identified as a potential regulator of Tfh cells and antitumor humoral response. Codeletion or pharmacological inhibition of MEK1/2 effectively promoted Tfh cell development in vitro and in vivo. Mechanistically, ATAC-seq and RNA-seq integrative analysis revealed interferon regulatory factor 4 (IRF4)-dependent epigenetic modulation of characteristic Tfh cell genes, thereby driving Tfh differentiation. Overexpression of Irf4 counteracted Mek1/2 ablation-mediated Tfh cell generation. Moreover, MEK1/2 inhibitor therapy enhanced Tfh infiltration coupled with humoral immune responses in murine melanoma model and was correlated with favorable clinical prognosis in melanoma patients. Our study revealed the MEK1/2-IRF4 axis potentiates Tfh development to enhance the antitumor humoral response. These findings may provide an unprecedented strategy to improve antitumor immunotherapy efficacy by harnessing humoral immune responses.