Increased CHST15 follows decline in arylsulfatase B (ARSB) and disinhibition of non-canonical WNT signaling: potential impact on epithelial and mesenchymal identity

Abstract

Expression of CHST15 (carbohydrate sulfotransferase 15; chondroitin 4-sulfate-6-sulfotransferase; BRAG), the sulfotransferase enzyme that adds 6-sulfate to chondroitin 4-sulfate (C4S) to make chondroitin 4,6-disulfate (chondroitin sulfate E, CSE), was increased in malignant prostate epithelium obtained by laser capture microdissection and following arylsulfatase B (ARSB; N-acetylgalactosamine-4-sulfatase) silencing in human prostate epithelial cells. Experiments in normal and malignant human prostate epithelial and stromal cells and tissues, in HepG2 cells, and in the ARSB-null mouse were performed to determine the pathway by which CHST15 expression is up-regulated when ARSB expression is reduced. Effects of Wnt-containing prostate stromal cell spent media and selective inhibitors of WNT, JNK, p38, SHP2, β-catenin, Rho, and Rac-1 signaling pathways were determined. Activation of WNT signaling followed declines in ARSB and Dickkopf WNT Signaling Pathway Inhibitor (DKK)3 and was required for increased CHST15 expression. The increase in expression of CHST15 followed activation of non-canonical WNT signaling and involved Wnt3A, Rac-1 GTPase, phospho-p38 MAPK, and nuclear DNA-bound GATA-3. Inhibition of JNK, Sp1, β-catenin nuclear translocation, or Rho kinase had no effect. Consistent with higher expression of CHST15 in prostate epithelium, disaccharide analysis showed higher levels of CSE and chondroitin 6-sulfate (C6S) disaccharides in prostate epithelial cells. In contrast, chondroitin 4-sulfate (C4S) disaccharides were greater in prostate stromal cells. CSE may contribute to increased C4S in malignant epithelium when GALNS (N-aceytylgalactosamine-6-sulfate sulfatase) is increased and ARSB is reduced. These effects increase chondroitin 4-sulfates and reduce chondroitin 6-sulfates, consistent with enhanced stromal characteristics and epithelial-mesenchymal transition.