Abstract 4363: Silencing of JAM-A inhibits cell growth through cell cycle arrest in endometrial cancer.

Endometrial cancer is one of the most common malignancies of the female genital tract. The identification of proteins for prognostic assessment and therapeutic targets in this disease is of significant clinical importance. We have previously reported a novel proteomic method for discovering potential therapeutic targets in endometrial cancer. We used a biotinylation-based approach for cell-surface protein enrichment combined with isobaric tags for relative and absolute quantitation (iTRAQ) technology using nano liquid chromatography-tandem mass spectrometry analysis to identify specifically overexpressed proteins in endometrial cancer cells compared with normal endometrial cells. We identified a total of 272 proteins, including 11 plasma membrane proteins, whose expression was increased more than twofold in at least four of seven endometrial cancer cell lines compared with a normal endometrial cell line. In addition to the identification of previously reported tumor antigens such as NCAML1, we also identified JAM-A as a novel tumor antigen in endometrial cancer by this methodology. JAM-A is a member of the immunoglobulin superfamily found at intercellular junctions of endothelial cells and epithelial cells. Some investigators have studied the role of JAM-A in carcinogenesis. However, the role of JAM-A in tumor growth and dissemination is still a debated issue. In this study, our goal is to investigate the role of JAM-A in tumor growth as well as the potential value in cancer therapeutic target. To confirm the altered expression of JAM-A in endometrial cancer, we performed flow cytometry and western blotting analysis using one immortalized normal endometrial cells (EM-E6/E7/TERT) and nine endometrial cancer cell lines (HEC-1, HEC-1A, HEC-6, HEC-88nu, HEC-108, HEC-116, SNG-II, and SNG-M). Protein expression of JAM-A was not detected in normal endometrial cells. In contrast, a considerably higher level of JAM-A expression was detected in all the nine endometrial cancer cell lines. Furthermore, to test the functional significance of JAM-A in endometrial cancer cell proliferation, the effect of JAM-A siRNA treatment was evaluated using WST-8 assay. Compared with non-target siRNA control, siRNA targeting JAM-A dramatically inhibits endometrial cancer cell proliferation. Flow cytometry with propidium iodide-staining revealed that JAM-A siRNA treatment induces cell cycle arrest in endometrial cancer cells. Taken together, our findings suggest that JAM-A may play a regulatory role in proliferation of endometrial cancer cells. Further studies are underway to identify the signal transduction pathway involved in JAM-A siRNA induced growth inhibition. Citation Format: Takuhei Yokoyama, Takayuki Enomoto, Kousuke Hiramatsu, Akiko Morimoto, Yutaka Ueda, Kiyoshi Yoshino, Masami Fujita, Tadashi Kimura, Satoshi Serada, Tetsuji Naka. Silencing of JAM-A inhibits cell growth through cell cycle arrest in endometrial cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4363. doi:10.1158/1538-7445.AM2013-4363