Glutaryl Polyamidoamine Dendrimer for Overcoming Cisplatin-Resistance of Breast Cancer Cells

Objective: Cisplatin has limited clinical applications due to drug resistance. PAMAM dendrimer was chosen as a vehicle to counteract cisplatin-resistance and its mechanism was assessed. Methods: Generation 5 Polyamidoamine dendrimer ( G5) was modified by glutaric anhydride ( GA) and then conjugated with cisplatin. The cisplatin release of G5-GA-cisplatin was evaluated at pH 5.5 and pH 7.4. The cytotoxicity of G5-GA-cisplatin and free cisplatin was compared in cisplatin-resistant breast cancer cell line MCF-7R. The intracellular platinum content of MCF-7R was determined using ICP-MS . The expression of Ctr1 and ATP7B of MCF-7R cells was also evaluated. Results: An average of 75 amino groups present in the G5 PAMAM surface were converted into glutaric acid (G5-GA(75)) and platinum loading was 350 +/- 21 mu g per 1 mg of G5-GA(75). G5-Ac-75-cisplatin complex exhibited controlled release of cisplatin at different pH over a period of 96 h. After 96 h incubation with G5-Ac-75-cisplatin, cell viability was 27.47 +/- 2.53%, 12.18 +/- 0.65% and 11.62 +/- 0.84% using platinum concentration of 1 mu g/ml, 3 mu g/ml and 5 mu g/ml, respectively. Meanwhile, 46.33 +/- 5.06% cells survived even in the high platinum concentration of 5 mu g/ml after 96 h incubation with free cisplatin. G5-GA(75) led to 3-6 times higher cisplatin accumulation than free cisplatin in MCF-7R cells, because MCF-7R cells exhibited lower Ctr1 expression and higher ATP7B expression than MCF-7 cells. Conclusion: The G5-GA(75)-cisplatin complex displayed greater anticancer activity than free cisplatin in the cisplatin-resistant breast cancer cell line MCF-7R. The low levels of Ctr1 and high levels of ATP7B in MCF-7R caused G5-GA(75) to allow the accumulation of cisplatin, which in turn increased the cytotoxicity. Results indicated that glutaryl G5 PAMAM may be a potential carrier for cisplatin targeting in breast cancer.