Chemotherapy resistance in ovarian cancer remains a current issue. Ti(IV)-derivatives represent a new alternative for platinum-resistant tumour treatment. They have demonstrated low toxicity and high efficacy in vitro and in vivo. However, their low stability and solubility in biological media have impeded its clinical application. Therefore, we have developed Ole-Ti, a new titanium complex with an oleic-like aliphatic chain, improving stability and solubility through non-covalent binding with serum albumin. In this study, we report some results about in vitro and in vivo effects of Ole-Ti.

Ole-Ti cytotoxicity was tested on A2780 and A2780Cis (cisplatin resistant) ovarian tumour cells lines by MTT assays. Intracellular Ti(IV) accumulation was quantified by TXRF. DNA interaction was studied by electrophoretic mobility assays. Apoptosis and oxidative stress were evaluated by flow cytometry with AnnexinV and DCFH-DA cell staining. Moreover, Caspase-3 protein level was assessed by western blot. PCR and qPCR were used to analysed the expression of endoplasmic reticulum stress mediators. For in vivo studies, A2780 cells were subcutaneously injected into nude-Foxn1 mice model. Mice were treated with Ole-Ti for two weeks and tumors volume were measured daily.

Ole-Ti showed greater cytotoxic activity than its precursor (TiCp2Cl2) on A2780 and A2780Cis cells. Based on IC50 and resistance factor values, we determined that Ole-Ti had high potency on A2780Cis cells. This seems to be related to elevated Ole-Ti uptake into cells. Thus, apoptotic cells increased significantly after Ole-Ti treatment. As well, some molecular mechanisms proposed for other titanium derivatives were evaluated with Ole-Ti. DNA does not seem to be the main target of Ole-Ti since no conformational change was observed in the electrophoretic mobility assay. In addition, we inspected Ole-Ti ability to induce cellular stress. The endoplasmic reticulum stress pathway was not activated in tumour cell lines after Ole-Ti treatment for 48 hours. Although Ti(IV) is a non-redox metal, oxidative stress production was significant in Ole-Ti treated cells. Taking in further, the addition of N-acetyl-L-cysteine significantly decreased the cytotoxic activity of Ole-Ti, suggesting that ROS could be responsible for cell death. Finally, the in vivo Ole-Ti potential was demonstrated as treatment with Ole-Ti reduced tumour size more effectively and earlier compared to cisplatin, leading to an increase in the mice survival.

Overall, Ole-Ti displays strong antitumor activity in ovarian cancer cells both in vitro and in vivo. Nevertheless, the cellular mechanism of Ole-Ti is still uncertain. We anticipated that oleic-like aliphatic chain might play a key role in Ole-Ti molecular activity. Hence, further research is required to identify additional pathways and molecular targets.