Abstract 4698: Increased CHST15 expression follows declines in Arylsulfatase B (ARSB) and DKK3 and disinhibition of non-canonical WNT signaling

Abstract

Abstract CHST15 (carbohydrate sulfotransferase 15; chondroitin 4-sulfate-6-sulfotransferase), is the sulfotransferase enzyme which adds 6-sulfate to chondroitin 4-sulfate to make chondroitin 4,6-sulfate, known as CSE. Increased CHST15 expression has been identified in malignant pancreas, renal, colon, ovary, and prostate tissues. We now report a pathway by which expression of CHST15 is increased following decline in the enzyme ARSB (arylsulfatase B; N-acetylgalactosamine-4-sulfatase), which is required for removal of 4-sulfate groups from chondroitin 4-sulfate (C4S). Previous work has shown that decline in ARSB and the resulting increase in C4S leads to decline in activity of SHP2, a ubiquitous non-receptor tyrosine phosphatase, due to enhanced binding of SHP2 with C4S when ARSB is reduced. Decline in SHP2 leads to enhanced ERK1/2 phosphorylation and subsequent downstream effects, including hypermethylation of the DKK (Dickkopf WNT signaling pathway inhibitor)3 promoter and suppressed DKK3 expression. Since DKK3 acts to inhibit Wnt signaling, Wnt signaling is enhanced in prostate epithelium when ARSB is reduced. Experiments were performed to identify the pathway by which CHST15 expression is up-regulated when ARSB is reduced and to assess the role of Wnt. The impact of ARSB silencing on CHST15 expression was determined in normal and malignant human prostate cells, in normal and malignant prostate tissue obtained by laser-capture microdissection, in HepG2 cells, and in prostate tissue of the ARSB-null mouse. Effects of selective inhibitors of Wnt and MAPK signaling pathways on CHST15 expression were evaluated. CHST15 expression was increased in malignant prostate epithelial tissue, in ARSB-null mouse prostate tissue, and following ARSB silencing in human prostate epithelial cells. The activation of Wnt signaling which followed declines in ARSB and DKK3 was required for increased CHST15 expression. Inhibition of Wnt3A blocked the increase in CHST15 expression in prostate epithelial cells co-cultured with prostate stromal cells, whereas DKK3 antibody increased CHST15. Inhibition of Rac-1 GTPase and of phospho-p38 MAPK signaling blocked the observed increase in CHST15 expression, whereas inhibition of JNK, Sp1, or of Rho kinase had no effect. These results indicate that the increase in epithelial CHST15 occurred in the malignant prostate cells and tissue due to effects of non-canonical Wnt signaling leading to enhanced phospho-p38 MAPK. The resultant increase in CHST15 when ARSB activity is reduced may contribute to determination of epithelial vs. stromal characteristics. Citation Format: Joanne Kramer Tobacman, Sumit Bhattacharyya, Leo Feferman. Increased CHST15 expression follows declines in Arylsulfatase B (ARSB) and DKK3 and disinhibition of non-canonical WNT signaling [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4698.