Vitamin D and Wnt3A have additive and partially overlapping modulatory effects on gene expression and phenotype in human colon fibroblasts.

The Wnt/β-catenin signalling pathway is essential for intestinal epithelium homeostasis, but its aberrant activation is a hallmark of colorectal cancer (CRC). Several studies indicate that the bioactive vitamin D metabolite 1α,25-dihydroxyvitamin D (1,25(OH)D) inhibits proliferation and promotes epithelial differentiation of colon carcinoma cells in part through antagonism of the Wnt/β-catenin pathway. It is now accepted that stromal fibroblasts are crucial in healthy and pathologic intestine: pericryptal myofibroblasts are constituents of the stem cell niche and cancer-associated fibroblasts (CAFs) contribute to CRC progression. However, studies on the combined action of 1,25(OH)D and Wnt factors in colon fibroblasts are lacking. Here we show by global transcriptomic studies that 1,25(OH)D and Wnt3A have profound, additive, partially overlapping effects on the gene expression profile of CCD-18Co human colon myofibroblasts. Moreover, 1,25(OH)D and Wnt3A inhibit CCD-18Co cell proliferation and migration, while 1,25(OH)D reduces, but Wnt3A increases, their capacity to contract collagen gels (a marker of fibroblast activation). These data were largely confirmed in patient-derived primary colon normal fibroblasts and CAFs, and in fibroblasts from other origins. Our results indicate that 1,25(OH)D and Wnt3A are strong regulators of colon fibroblast biology and contribute to a better knowledge of intestinal homeostasis and stromal fibroblast action in CRC.