Molecular Mechanisms And Signaling Transduction Pathways Of Cell Cycle Arrest Induced By Lidamycin In Human Cancer Cells

Lidamycin (LDM, originally named C-1027) is a member of the enediyne antibiotic family, which was isolated from a Streptomyces globisporus C-1027 strain in China. It consists of a chromophore and an apoprotein, and the former has the activity to attack DNA, whereas the latter plays the role in protecting chromophore. Our previous studies have demonstrated that LDM has highly potent cytotoxicity in tumor cells and it is currently being evaluated in phase I clinical trials as a potential cancer chemo-therapeutic agent. Like other DNA damage agents, LDM induces cell cycle arrest, apoptosis and mitotic cell death. But the detailed molecular mechanisms of LDM-induced cell cycle arrest have not been defined. In the present study, we elucidate the mechanisms and signaling pathways of LDM-induced cell cycle arrest in human cancer cells and provide further evidence to support the use of this new drug in clinical cancer therapy.1. LDM-induced cell cycle arrest in human breast cancer cells(1) After treatment with LDM for 21k 41k 24h , then continuously incubation in drug-free medium to 48h, or treatment with LDM for 48h, IC50 values of LDM determined by MTT assay were 0.46±0.14 nM, 0.32±0.12 nM, 0.24±0.08 nM and 0.48± 0.11 nM, respectively.(2) Human breast cancer MCF-7 and MCF-7/DOX cells were treated with increasing concentrations of LDM for 24h before being incubated in fresh medium for an additional three days. Results showed that LDM induced a dose-dependent growth inhibition in both MCF-7 and MCF-7/DOX cells. When Tteatment with 0.1 nM LDM, cell growth was inhibited by 89.93±4.5% and 89.77±3.9% in MCF-7 and MCF-7/DOX cells, respectively, indicating that multidrug-resistant MCF-7/DOX cells was sensitive to LDM.(3) Flow cytometry analysis showed that the effect of LDM on cell cycle regulation was dose-dependent. At lower concentration (0.01 nM), LDM induced G1 arrest (increased from 60.7% to 74.8%) and less G2/M arrest in MCF-7 cells. However, treatment with higher concentrations of LDM (0.1 and 1 nM), the G2/M population was increased with a decrease in S-phase cells and without obvious change in the Gl population, indicating LDM might be induced Gl and G2/M arrests at the both...