Sphingosine‐1‐phosphate receptor 2 is a negative regulator of epithelial cell proliferation and intestinal tumorigenesis
Authors: Petti Luciana , Piontini Andrea , Arena Vincenzo , Danese Silvio , Vetrano Stefania 
Published: November 2023

Sphingosine‐1‐phosphate (S1P) is a bioactive sphingolipid metabolite, involved in several cellular processes through the activation of the five G protein‐coupled receptors (S1PR1‐5). Among these receptors, we have observed that S1PR2 is the highest receptor expressed by human and murine intestinal epithelial cells. S1PR2 regulates several processes such as cell proliferation, migration, but its role on intestinal epithelial cells is not completely known. Emerging evidences have been revealed the involvement of S1P2 in the development and progression of different type of cancers. However, so far no data report the involvement of S1PR2 in the colorectal cancer (CRC). Aim of this study is to explore S1PR2 epithelial function and S1PR2 involvement in the intestinal tumorigenesis.

S1PR2 expression was analysed at mRNA and protein levels. Intestinal permeability was measured in WT and S1PR2 knock‐out (ko) mice. S1PR2 ko and WT mice were given a single administration of the carcinogenic agent azoxymethane, followed by three cycles of 2.5% dextran sodium sulphate. Mice were daily monitored for weight loss, presence of fecal blood, and diarrhoea, whereas weekly for the presence of tumors by endoscopy. The inflammation score and the tumor number were evaluated by a blinded histological analysis. Apc+/min and Apc+/min/S1PR2 ko mice were characterized for the presence of intestinal and colonic tumor number. In vitro cell proliferation and TEER measurements were performed on Caco‐2 cells in presence and in absence of JTE013, a specific S1PR2 inhibitor, by BrdU incorporation assay and voltmeter, respectively. S1PR2 is the most highly S1P receptor expressed in intestinal epithelial cells and, interestingly, the immunostaining of S1PR2 performed on murine colonic mucosa evidenced a strong positive signal by epithelial cells located at the top and not at the bottom of the crypts, suggesting that only more differentiated epithelial cells expresses S1PR2. No differences in terms of intestinal permeability and expression of epithelial adhesion molecules have been observed in vivo between WT and S1PR2 ko mice, and in vitro in presence and absence of JTE013. On the contrary, an increased proliferative rate was found both in vitro and in vivo. The colitis‐induced and genetic Apc+/min mouse models of colorectal cancer showed higher incidence in size and number of tumors or high‐grade dysplasia in S1PR2 ko and Apc+/min/S1P2 ko mice compared to WT controls. Overall these results exclude the role of S1PR2 in regulating epithelial paracellular permeability, but suggest that S1PR2 negatively regulates the proliferation of colonic epithelial cells and plays a role in the development of colorectal cancer. Since S1PR2 is mostly expressed on differentiated epithelial cells and its expression increases in benign adenomas, but significantly decreased in carcinomas, we hypothesize that S1PR2 acts as a tumor suppressor blocking the epithelial cell cycle and the de‐differentiation process.

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MFAG 2015 Id.17795 to S.V