DPP4 and breast cancer: Under these conditions, the effects of VD on both cancer cells and CAFs were less intense, although a number of genes including CYP24A1, dipeptidyl peptidase-4 (DPP4) and carbonic anhydrase 2 (CA2) were still markedly up-regulated by VD in CAFs, suggesting that even physiological levels of VD given over a relatively short time-period are able to modulate the stroma in BC [100].