Stomatin-like Protein 2 Is Overexpressed in Cancer and Involved in Regulating Cell Growth and Cell Adhesion in Human Esophageal Squamous Cell Carcinoma

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Abstract
Purpose: Stomatin-like protein 2 (SLP-2) is a novel and unusual stomatin homologue of unknown functions. It has been implicated in interaction with erythrocyte cytoskeleton and presumably other integral membrane proteins, but not directly with the membrane bilayer. We show here the involvement of SLP-2 in human esophageal squamous cell carcinoma (ESCC), lung cancer, laryngeal cancer, and endometrial adenocarcinoma and the effects of SLP-2 on ESCC cells. Experimental Design: Previous work of cDNA microarray in our laboratory revealed that SLP-2 was significantly up-regulated in ESCC. The expression of SLP-2 was further evaluated in human ESCC, lung cancer, laryngeal cancer, and endometrial adenocarcinoma by semiquantitative reverse transcription-PCR, Western blot, and immunohistochemistry. Mutation detection of SLP-2 exons was done by PCR and automated sequencing. Antisense SLP-2 eukaryotic expression plasmids were constructed and transfected into human ESCC cell line KYSE450. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, clonogenecity assay, flow cytometry assay, nude mice tumorigenetic assay, and cell attachment assay were done to investigate the roles of SLP-2 gene. Results: All tumor types we tested showed overexpression of SLP-2 compared with their normal counterparts (P ≤ 0.05). Moreover, immunohistochemistry analysis of mild dysplasia, severe dysplasia, and ESCC showed that overexpression of SLP-2 occurred in premalignant lesions. Mutation analysis indicated that no mutation was found in SLP-2 exons. KYSE450 cells transfected with antisense SLP-2 showed decreased cell growth, proliferation, tumorigenecity, and cell adhesion. Conclusions: SLP-2 was first identified as a novel cancer-related gene overexpressed in human ESCC, lung cancer, laryngeal cancer, and endometrial adenocarcinoma. Decreased cell growth, cell adhesion, and tumorigenesis in the antisense transfectants revealed that SLP-2 may be important in tumorigenesis.