Abstract 4998: Lipolysis-stimulated lipoprotein receptor (LSR) can be a novel therapeutic target of ovarian cancer

Abstract Objective:Ovarian cancer is the most lethal gynecological malignancy. Five-year survival of advanced ovarian cancer patients remains less than 50% and the mortality rate has not changed in recent years. This study is aimed to screen for novel ovarian cancer therapeutic targets using quantitative proteomic approach and to develop antibody-based medicine targeting novel ovarian cancer antigens. Method:Exhaustive quantitative proteome analysis focused on cell surface membrane proteins were performed by isobaric tags for relative and absolute quantitation(iTRAQ) using a normal ovarian surface epithelial cell line and 7 ovarian cancer cell lines. By this approach, ovarian cancer-specific membrane proteins were identified. We confirmed the expression of lipolysis-stimulated lipoprotein receptor (LSR) using immunohistochemical staining, western blotting method, and flow cytometry. By modified MTT assay, cell growth inhibition was performed in LSR-knock down cells compared with control cells. Cell adhesion assay was also performed in vitro. Anti-LSR monoclonal antibody (anti-LSR mAb) was generated to evaluate the efficacy of the LSR targeted antibody therapy in vivo. For subcutaneous xenograft experiments, ovarian cancer cell line (RMG-1) was injected subcutaneously into the CB17/SCID mice. Mice were then randomly divided into two groups and administrated intraperitoneally anti-LSR mAb or control IgG antibody twice a week for 6 times. In addition, luciferase transfected ovarian cancer cell line (A2780-luc) was implanted intraperitoneally into the CB17/SCID mice. Mice were administrated anti-LSR mAb or control IgG antibody intraperitoneally twice a week for 5 times. Result:By iTRAQ analysis, we identified 1685 proteins and one of the ovarian cancer candidates protein, LSR was identified. We confirmed the expression of LSR in 8 out of 11 ovarian cancer cell lines and all of ovarian cancer clinical specimens. We performed proliferation assay using siRNA against ovarian cancer cell lines. When expression of LSR was suppressed, a tumor growth was significantly inhibited at day 4(p<0.01). In adhesion assay, we observed significant inhibition of cell adhesion in LSR knockdown cells. These results suggested that LSR is related to cell proliferation and adhesion. A significant anti-tumour effect with 78% was observed in the anti-LSR mAb antibody administrated group compared with control IgG antibody administrated group after 25 days (p <0.001). Furthermore, in intraperitoneal xenograft model, anti-LSR antibody administration group significantly decreased signal intensities compared with the control antibody administration group at day 22 after implantation. Conclusion:We showed that the LSR is related to cell proliferation and adhesion in vitro in ovarian cancer cells and proved the antitumor effect of anti-LSR mAb. These results suggested that LSR can be a new therapeutic target of ovarian cancer. Citation Format: Satoko Matsuzaki, Kosuke Hiramatsu, Satoshi Serada, Satoshi nakagawa, Shinya Matsuzaki, Yutaka Ueda, Minoru Fujimoto, Kiyoshi Yoshino, Tadashi Kimura, Tetsuji Naka. Lipolysis-stimulated lipoprotein receptor (LSR) can be a novel therapeutic target of ovarian cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4998.