Abstract 2944: Decline in arylsulfatase B (N-acetylgalactosamine-4-sulfatase) leads to increased expression of the transmembrane glycoprotein GPNMB
Authors: Bhattacharyya Sumit , Feferman Leo , Tobacman Joanne Kramer 
Published: May 2015

The enzyme arylsulfatase B (ARSB; N-acetylgalactosamine-4-sulfatase), which removes 4-sulfate groups from chondroitin-4-sulfate (C4S) and dermatan sulfate, is reduced in malignant human epithelial breast, colonic, and prostate cells and tissues. Lower ARSB immunohistochemical scores have been associated with shorter intervals to recurrence in paired cases of prostate cancer and with propensity for metastasis in malignant colonic cells. The transmembrane glycoprotein GPNMB has been shown to be increased in malignant melanoma, glioblastoma multiforme, and mammary carcinoma, and is a target of antibody therapy in triple-negative breast cancers. In the ARSB-deficient mouse, cDNA microarray of prostate tissue demonstrated 9.53-fold increase in expression of GPNMB, compared to age- and gender- matched C57BL/6J wild-type controls. Measurements by ELISA of GPNMB protein in the ARSB-null mouse liver and prostate tissues showed significant increases, compared to C57BL/6J wild-type controls. In the liver of female ARSB-deficient mice, the gpnmb increased to 47.1 ± 5.7 ng/mg protein from 8.5 ± 1.2 ng/mg protein in the control mouse liver (n=5 in each group), and similar six-fold increases occurred in the male ARSB-null mouse liver. Prostate gpnmb increased more that three-fold, and serum levels in female and male null mice were significantly greater. When ARSB was silenced by siRNA in the normal human prostate stromal cell line (WPMY-1), GPNMB increased from 3.6 ± 0.3 ng/mg protein to 18.3 ± 1.1 ng/mg protein, and in the normal human prostate epithelial cell line (WPE1-NB14) from 4.8 ± 0.4 to 24.7 ± 1.6 ng/mg protein. Similarly in the human hepatic cell line, HepG2, GPNMB increased greater than five-fold.

Decline in ARSB leads to increased chondroitin-4-sulfation and reduced galectin-3 binding to C4S, enabling increased nuclear translocation of galectin-3. We have shown that the increase in nuclear galectin-3 following decline in ARSB impacts on transcriptional events mediated by AP-1 in human epithelial cells, including increases in HIF-1α and versican. However, in the prostate stromal and epithelial cell lines, AP-1 inhibitors, including a c-Jun mimetic peptide and an oligonucleotide inhibitor of c-Fos DNA-binding, did not reduce the increase in GPNMB expression that followed ARSB silencing. Although the mechanism for the decline in GPNMB expression is unknown at this time, the findings support a critical role for ARSB in vital cell processes and suggest that ARSB may be useful as a therapeutic target in malignancy.

Citation Format: Sumit Bhattacharyya, Leo Feferman, Joanne Kramer Tobacman. Decline in arylsulfatase B (N-acetylgalactosamine-4-sulfatase) leads to increased expression of the transmembrane glycoprotein GPNMB. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2944. doi:10.1158/1538-7445.AM2014-2944