Mechanism of Regulation and Suppression of Melanoma Invasiveness by Novel Retinoic Acid Receptor-γ Target Gene Carbohydrate Sulfotransferase 10

Abstract

Retinoic acid (RA) induces growth arrest and differentiation of S91 murine melanoma cells and serves as a valuable model for this disease. RA acts through activation of RA receptors (RAR), which are members of the nuclear receptor superfamily of ligand-inducible transcription factors. Interestingly, differentiation is mediated by RARγ, but not by RARα or RARβ, suggesting that RARγ possesses unique and uncharacterized molecular properties. To address this question, DNA microarrays in combination with RAR isoform-specific agonists were employed to identify novel RARγ target genes that may play a role in this process. Here, we identified and validated carbohydrate sulfotransferase 10 (CHST10) as a novel RARγ target gene in S91 cells. The RARγ-inducible CHST10 promoter was obtained, and two atypical, independently functioning RA response elements were identified in a 425 bp region. Surprisingly, this fragment is bound by RARγ, but not by RARα or RARβ, thus providing a mechanism for the observed RARγ-specific regulation. CHST10 is a sulfotransferase that forms HNK-1 glycan on neural cell adhesion proteins and glycolipids, and HNK-1 is thought to modulate cell adhesion and possibly metastasis. We show that CHST10 is also regulated by RARγ in a significant subset of human melanoma cells, and three-dimensional cell culture migration assays suggest that CHST10 functions as a suppressor of invasiveness, but not proliferation, in these cells. Induction of CHST10 by RARγ-activating retinoids may present a novel therapeutic strategy to inhibit invasiveness in a subset of melanoma patients. [Cancer Res 2009;69(12):5218-25]

Human Natural Killer-1 Sulfotransferase (HNK-1ST)-induced Sulfate Transfer Regulates Laminin-binding Glycans on α-Dystroglycan

“…Following treatment with 1 M RA, a marked increase of HNK-1ST mRNA was detected using RT-PCR (Fig. 1, A and B), consistent with a previous report (6). However, neither of the glucuronyltransferases (GlcAT-P and GlcAT-S) responsible for producing HNK-1 was observed (Fig.…”

“…Apparent confounding issues are that HNK-1ST functions as a tumor suppressor, although the resulting product, the HNK-1 epitope, promotes metastasis. However, it should be noted that whereas Zhao et al (6) reported that HNK-1ST functions as a tumor suppressor, they failed to detect the HNK-1 epitope in 56 primary and 20 metastatic melanomas. This means that HNK-1ST might regulate invasiveness through an HNK-1 epitope-independent pathway.…”

“…Glycosylation of ␣-DG in RA-treated Melanoma Cells-To investigate whether HNK-1ST governs tumor-related phenotypes of melanoma cells via production of the HNK-1 carbohydrate or not, we evaluated the mRNA expression of the enzymes synthesizing HNK-1 in S91 murine melanoma cells, which undergo RA-mediated differentiation (6,36). Following treatment with 1 M RA, a marked increase of HNK-1ST mRNA was detected using RT-PCR (Fig.…”

“…Therefore, the aberrant expression of various genes involved in glycan synthesis or degradation, which causes compositional changes of the glycocalyx, is frequently associated with malignant transformation (3)(4)(5). Recently, Zhao et al (6) reported the expression of human natural killer-1 sulfotransferase (HNK-1ST) to be strongly up-regulated in several subsets of murine and human melanoma cells during retinoic acid (RA) 2 mediated differentiation. The expression of HNK-1ST is activated via an RA receptor-␥ pathway, and the invasiveness of melanoma cells is suppressed along with HNK-1ST induction (6).…”

“…Recently, Zhao et al (6) reported the expression of human natural killer-1 sulfotransferase (HNK-1ST) to be strongly up-regulated in several subsets of murine and human melanoma cells during retinoic acid (RA) 2 mediated differentiation. The expression of HNK-1ST is activated via an RA receptor-␥ pathway, and the invasiveness of melanoma cells is suppressed along with HNK-1ST induction (6). HNK-1ST is a sulfotransferase involved in the biosynthesis of the HNK-1 carbohydrate, a neural glyco-epitope exhibiting abundant expression during brain development (7).…”