KDM6A downregulation promotes tumor-prone cytokines expression in cancer-associated fibroblasts by activating enhancers

Cancer-associated fibroblasts (CAFs) are activated fibroblasts that secrete numerous cytokines and chemokines to accelerate tumor progression. However, the mechanism underlying cytokine production by CAFs remains unclear. This study reports that CAFs isolated from colon cancer tissue, TGF-β1-induced CAFs, or HCT116 co-cultured CAFs secrete more cytokines and growth factors represented by IGF1, ELN, and SFRP2. Mechanistic investigations demonstrate that aerobic glycolysis metabolites fumarate and succinate can induce the transcription of IGF1, ELN, and SFRP2 in CAFs, while α-ketoglutarate (α-KG) can antagonize the induction effect of fumarate and succinate. Moreover, the downregulation of KDM6A in CAFs is observed compared to quiescent fibroblasts (NAFs). Additionally, integrated analysis of ATAC sequencing and RNA sequencing revealed altered chromatin structure during fibroblast activation. CUT-tag sequencing and co-IP assays demonstrate that KDM6A is bound to WDR5, facilitating its association with the COMPASS complex and the polycomb repressive complex at the expected target loci. Depletion of KDM6A disrupts the homeostasis between polycomb and COMPASS complexes, leading to an increase in the expression of IGF1, ELN, and SFRP2. However, the inhibitor GSK-J4, specific for both KDM6A and KDM6B, reduces IGF1 expression, indicating that KDM6B compensates for the demethylase function of KDM6A but cannot replace KDM6A to maintain the homeostasis of COMPASS and polycomb repressive complexes. These findings suggest a metabolism-related epigenetic mechanism for cytokine expression, where reduced KDM6A levels enhance the tumor-promoting effect of CAFs. This may provide insights into why colon cancer is more prevalent in men than in women, since KDM6A is an X-chromosome-associated gene.