Nano-carrier Polyamidoamine Dendrimer G4 Induces Mitochondrialdependent Apoptosis in Human Multidrug-resistant Breast Cancer Cells through G0/G1 Phase Arrest

Background: Multidrug-resistant tumor cells have special drug detoxification/inactivation mechanisms. The terminal amino groups of the polyamidoamine (PAMAM-NH2), which is cytotoxic to tumor sensitive cells, may have no cytotoxicity in tumor resistant cells with a mechanism different from tumor sensitive cells. Objective: This study aimed to investigate the cytotoxic effects of PAMAM-G4-NH2 on human multidrug- resistant breast cancer cells (MCF-7/ADR cells) and identify the possible molecular mechanisms. Methods: The cytotoxicity of PAMAM-G4-NH2 (10-1000 μg/mL) against MCF-7 and MCF-7/ADR cells was detected. Then, MCF-7 and MCF-7/ADR cells were treated with PAMAM-G4-NH2 (10, 100 and 1000 μg/mL), and apoptosis, reactive oxygen species (ROS) production, mitochondrial membrane potential (MMP), activities of caspase-3, -8 and -9 and cell cycle distribution were determined. Results: Within 48 h, the cell viabilities in MCF-7/ADR cells after treatment with PAMAM-G4-NH2 were significantly higher than that in MCF-7 cells in the concentration range of 200-500 μg/mL (P < 0.05). Viabilities of MCF-7/ADR cells treated with PAMAM-G4-OH and PAMAM-G4-COOH for 48 and 72 h were much higher than that of MCF-7/ADR cells treated with PAMAM-G4-NH2. Treated with high concentration (1000 μg/mL) of PAMAM-G4-NH2 for 24 h, the apoptosis ratio, ROS levels, as well as caspase-3 and -9 activities in MCF-7 and MCF-7/ADR cells increased, while MMP decreased, and the cells were arrested in the G0/G1 phase. Conclusion: PAMAM-G4-NH2 induced concentration-dependent cytotoxicity in MCF-7/ADR cells via G0/G1 arrest, and acted through h the mitochondria-dependent apoptotic pathway, which was similar to those in tumor sensitive cell, MCF-7 cells. The results suggest that PAMAM-G4-NH2, instead of PAMAM-G4-OH and PAMAM-G4-COOH, can be used as a carrier for drug delivery, concomitantly, it can also induce apoptosis in multidrug-resistant cancer cells in combination with the loaded drug through multiple apoptotic pathways.