Abstract LB-100: Targeting TMEM205 mechanotransduction pathway using oncolytic virus therapy in ovarian clear cell carcinoma (OCCC)

Objectives: Ovarian clear cell carcinoma (OCCC) is an aggressive form of ovarian cancer and unfavorable treatment outcomes have been attributed to its relative chemoresistance & recurrence, limiting the available treatment options. Therefore, identifying novel unique protein(s) involved in OCCC chemoresistance and designing a therapeutic modality selectively targeting those proteins would make a significant impact on therapy. TMEM205 is one such protein which has been recently linked to cisplatin resistance in human epidermoid carcinoma, but the precise molecular mechanism of this resistance still needs to be elucidated. This proposed study was planned to a) identify the role of TMEM205 expression in OCCC b) mechanotransduction pathway of TMEM205 c) evaluate the in vitro and in vivo efficacy of oncolytic virus ( oHSV) as a single agent or in combination with cisplatin. Methods: Human patient tissue samples from OCCC patients, OCCC cell lines like JHOC, OVTOKO, OVISE and ES2 and exosomes were analyzed for the expression of TMEM205 using Western blot, IHC/ICC and real time qPCR. Exosomes were isolated from conditioned medium and characterized using NTA. Antibody feeding assays and plasma membrane internalization assays were conducted to address the endocytosis and recycling behavior of TMEM205. TMEM205 overexpression and knockdown experiments were performed in vitro in OVTOKO cells and in vivo in nude mice, to confirm the role of TMEM205 in OCCC. Cisplatin accumulation in cells as well as DNA and exosomes was quantified using ICP-MS and dot blot. oHSV virus therapy was further tested in vitro or in vivo -alone or combined with cisplatin treatment. Results: The OCCC tissues, cell lines and exosomes exhibit medium to high expression of TMEM205. Mechanistically, TMEM205 undergoes ligand independent constitutive endocytosis, co-localizes with Rab 11 to be a part of the late recycling endosomes with only 6% of TMEM205 being recycled back to the plasma membrane. Knockdown of TMEM205 triggers more intracellular cisplatin accumulation in comparison to the exosomes derived from them. Further, TMEM205 interacts with glycoprotein C of oHSV and both of these proteins undergo ubiquitinylation to ultimately get shuttled outside the cell via exosomes. We also report that oHSV pretreatment followed by treatment with cisplatin (CP) increases apoptosis and decreases cell survival, in vitro as well as in vivo tumor growth . Conclusions: TMEM205 imparts drug resistance via exosomes and knockdown of TMEM205 in OCCC contributes to enhanced chemotherapy sensitivity. The combination therapy of oHSV with cisplatin is more effective than oHSV or cisplatin treatment alone and reduces the overall tumor burden of OCCC mice. This will pave the way for exploring the clinical implications of TMEM205 in OCCC, and evaluating whether TMEM205 expression is key to higher risk of resistance and recurrence seen in OCCC. Citation Format: Uksha Saini. Targeting TMEM205 mechanotransduction pathway using oncolytic virus therapy in ovarian clear cell carcinoma (OCCC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-100.