Abstract 4416: Reversal of chemoresistance in ovarian cancer cells by the liposomal co-delivery of MDR inhibitors and paclitaxel

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Ovarian cancer is one of the most lethal gynaecologic malignancies. This can be attributed to the emergence of multidrug resistance in the clinic due to the over-expression of drug-efflux pumps such as P-gp. To overcome this, we have developed a liposomal platform for the the co-delivery of potent P-gp inhibitors with chemotherapeutic drugs. Purpose: To allow for the effective reversal of chemo-resistance in ovarian cancer cells using liposomes co-loaded with tariquidar and paclitaxel. Methods: PEGylated liposomes composed of eggphosphatidylcholine, cholesterol and DOTAP loaded with equimolar amounts of tariquidar (XR) and paclitaxel (PCT) were prepared by the thin film hydration method followed by extrusion. Evaluation of drug resistance of ovarian cancer lines SKOV3, HeyA8 and Tynku was carried out by quantifying MDR1 and MRP1 receptor expression followed by a rhodamine123 exclusion assay. The cytotoxicity of the formulations on the above cancer cell lines was evaluated using the Promega cell viability assay. The effects of the formulations were evaluated in fluorescently stained cells using the iCyte® imaging cytometer (Thorlabs, USA). Long-term kinetic analysis of unstained live cultures was perfomed by holographic imaging cytometer Holomonitor ® M4 (Phase Holographic Imaging, Sweden) and fluorescence microscopy. Results: The liposomes had a particle size distribution of about 200 nm with a zeta potential of 30 mV. As compared to MRP1, a 2.4 fold, 1.9-fold and 1.6-fold higher expression of MDR1 was seen in the HeyA8-MDR, SKOV3-TR and Tynku-R cells respectively over their drug-sensitive counterparts. Using the rhodamine exclusion assay, 14 nM of liposomal XR showed better rhodamine inclusion than 140 nM free XR. In vitro cytotoxicity experiments showed that the drug co-loaded formulation was able to effectively overcome resistance to PCT even at low PCT doses. Using live-cell imaging, paclitaxel-induced arrest of cell cycle progression and onset of apoptosis following this mitotic catastrophe was visible from 1.5 μM to 50 nM only with the co-loaded liposomes. The cell cycle arrest was further visualized using time-lapse Holomonitor M4 which showed the increasing incidence of cells arrested in mitosis over time. Using fluorescence microscopy, we were able to clearly visualize the presence of polymerized microtubules around the cell nucleus as a result of the paclitaxel-mediated microtubule dysfunction. Conclusions: Uniform liposomes co-loaded with tariquidar and paclitaxel were prepared and characterized. The co-loaded liposomes were able to effectively reverse chemoresistance and induce cytotoxicity in a variety of drug-resistant ovarian cancers. The formulations were shown to arrest cell cycle, preventing its progression to the G1 phase. This arrest of cell cycle was shown to be due to the paclitaxel-mediated micro-tubule dysfunction. Note: This abstract was not presented at the meeting. Citation Format: Shravan K. Sriraman, Yilin Zhang, Ed Luther, Ernst Lengyel, Vladimir Torchilin, Vladimir Torchilin. Reversal of chemoresistance in ovarian cancer cells by the liposomal co-delivery of MDR inhibitors and paclitaxel. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4416. doi:10.1158/1538-7445.AM2015-4416