Wnt5a-Ror2 signaling in mesenchymal stem cells promotes proliferation of gastric cancer cells by activating CXCL16-CXCR6 axis.
Bottom Line: Wnt5a-Ror2 signaling has been shown to play important roles in promoting aggressiveness of various cancer cells in a cell-autonomous manner.However, little is known about its function in cancer-associated stromal cells, including mesenchymal stem cells (MSCs).Interestingly, it was found that expression of CXCL16 in MSCs is augmented by Wnt5a-Ror2 signaling, and that recombinant chemokine (C-X-C motif) ligand (CXCL)16 protein can enhance proliferation of MKN45 cells in the absence of MSCs.
Affiliation: Division of Cell Physiology, Department of Physiology and Cell Biology, Graduate School of Medicine, Kobe University, Kobe, Japan.Show MeSH
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Mentions: It has been shown that CXCR6 acts as a receptor for soluble and transmembranous forms of CXCL16.18, 19, 22 Therefore, it can be envisaged that CXCR6 might be expressed on MKN45 cells to mediate CXCL16‐induced proliferation signaling. In fact, quantitative RT‐PCR analysis revealed remarkably high levels of CXCR6 mRNA in MKN45‐Luc cells compared with those in MSCs (Fig. S5). Treatment of MKN45‐Luc cells with siRNA against CXCR6 inhibited expression of CXCR6 (Fig. 5a). Flow cytometric analysis also showed expression of cell surface CXCR6 proteins on MKN45‐Luc cells and its inhibition by the siRNA treatment (Fig. 5b). It was found that suppressed expression of CXCR6 in MKN45‐Luc cells by itself had marginal effect, if any, on proliferation of MKN45‐Luc cells (monoculture) (Fig. S6). However, suppressed expression of CXCR6 in MKN45‐Luc cells significantly inhibited the promotion of MKN45‐Luc cell proliferation by direct or indirect coculture with MSCs (Figs 5c,d,S6), indicating that CXCR6 expressed on MKN45 cells plays a critical role in the promotion of MKN45 cell proliferation by CXCL16 secreted from MSCs.
Affiliation: Division of Cell Physiology, Department of Physiology and Cell Biology, Graduate School of Medicine, Kobe University, Kobe, Japan.