A Continued Study on the Stealth Liposomal Topotecan Plus Amlodipine: In Vitro and In Vivo Characterization in Non-Resistant Solid Tumors

Abstract

We have previously established a type of anti-resistant stealth liposomal topotecan plus amlodipine for overcoming the multi-drug resistance (MDR) in resistant leukemia cells. The objective of the present study was to further characterize it in the diversified non-resistant solid tumors in vitro and in vivo. Stealth liposomal topotecan plus amlodipine was re-prepared and physicochemically characterized. The in vitro drug release assays of topotecan and amlodipine from liposomes were performed using a dialysis method. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assays were performed in murine sarcoma S180 cells and human breast cancer MCF-7 cells, respectively. Apoptotic percentages of S180 cells were evaluated using flow cytometry. In vivo anti-tumor activity study and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) analysis were performed in male Institute of Cancer Research (ICR) mice with S180 xenografts. Stealth liposomal topotecan plus amlodipine exhibited high drug encapsulation efficiencies, suitable particle size distribution, negatively charged zeta potential and prolonged release profiles for both topotecan and amlodipine. Amlodipine potentiated the antiproliferative effect and inducing apoptotic effect of topotecan on the tumor cells, exhibiting an additive anti-tumor effect. Stealth liposomal topotecan plus amlodipine showed the optimal anti-tumor activity and inducing apoptotic effect in the in vivo studies. Stealth liposomal topotecan plus amlodipine demonstrated an overt anti-tumor activity in non-resistant solid tumors, suggesting that it deserves further clinical evaluations.