The objective of these in vitro and in vivo studies was to validate Lemur Tyrosine Kinase 3 (LMTK3) as a specific target and predictor of clinical outcome in ovarian cancer. LMTK3 belongs to a family of regulated tyrosine kinases with three structurally related isoforms, LMTK1, LMTK2, and LMTK3. Both nuclear and cytoplasmic LMTK3 expressions correlated with tumor grade and patient survival in cancers such as breast and colorectal cancer. We tested the clinical significance of the LMTK3 gene by immunohistochemistry (IHC) using LMTK3 monoclonal antibody on formalin-fixed paraffin-embedded sections (FFPE) collected from 204 early-stage (stage I-II) ovarian cancer patients. Results from this IHC LMTK3 study revealed a higher cytoplasmic to nuclear localization of LMTK3 correlated with worse overall survival (P<0.01). Further investigation of LMTK3’s prognostic value by screening LMTK3 signaling in 270 stage III-IV ovarian cancer patients is ongoing. We utilized the MTT ((3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay for testing the killing efficacy of targeting LMTK3 by a monoclonal antibody, siRNA, and specific LMTK3 binding peptides (LMTK3BP) in ovarian cancer cell lines SKOV3, MDAH-2774, A2780, and TOV-21G. Treatment with LMTK3 specific monoclonal antibody, siRNA, and LMTK3BP significantly induced killing of both chemosensitive and chemoresistant ovarian cancer cells without affecting normal cells in vitro. Moreover, we observed this killing as synergistic with both Cisplatin and Taxotere treatment in vitro. Lastly, we used an A2780 cell line derived orthotopic xenograft mouse model of ovarian cancer to test the efficacy of specific LMTK3BP in vivo. Strikingly, LMTK3BP 20 mg/kg IV dose given three times a week for three weeks showed a 35% tumor reduction. Furthermore, in vivo safety studies showed no signs of toxicity of the LMTK3BP, even at a very high dose of 40 mg/kg. Thus, with dose optimization in ongoing experiments, we could expect a higher efficacy. In conclusion, this study highlighted the importance of LMTK3 as a predictor of patient clinical outcome and potential target for treatment in ovarian cancer.

Citation Format: Thea K. Kirsch-Mangu, Axel S. Tullberg, Anna Portela, Khalil Helou, Ghassan M. Saed. Lemur tyrosine kinase 3 serves as a predictor of patient outcome and a target for the treatment of ovarian cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5556.