Study On Radiosensitization Of 4-AN In A549 Cells And Its Mechanism

It has always been an important subject to find new and highly potent radiosensitizers. However, none of drugs have been found to be an ideal radiosensitizer in the last 50 years. At present, radiosensitizers used in scientific research and clinical trials are those with both radiosensitizing and limited toxic effects. Poly (ADP-ribose) polymerase(PARP) is a kind of nuclear proteins which participates in many biological processes, such as DNA repair, replication, amplification and proliferation, differentiation and death of cells. Recently, various experimental research show that PARP inhibitors are expected to be the medicine targeting to some DNA repair-defective tumors. Furthermore it has aroused more interest as sensitizer of both radiotherapy and chemotherapy and will be a hotspot for research in the future.Objective: 4-Amino-1,8-Naphthalimide(4-AN) has been considered as a more potent PARP inhibitor in treatment of inflammatory disease, ischemic injuries and tumors in both in vitro and animal experiments. But research on 4-AN as radiosensitizer in treatment of lung cancer has rarely been reported yet. Radiosensitization of 4-AN in A549 cells and its mechanism was studied in the research.Methods: (1)A549 cells were treated with 4-AN in different concentrations and assessed for cell viability in MTT and Trypan blue exclusion assays. ( 2 )Radiosensitivity of 4-AN in A549 cells was evaluated using clonogenic assay, MTT assay, SCGE(Alki single cell gel electrophoresis) assay. (3) FCM(Flow cytometry) and Western blot were used respectively to determine cell cycle distribution and expression of corresponding CyclinsConclusion: (1) 4-AN inhibited the growth of A549 cells in a dose-dependent manner. (2) 4-AN exerted radiosensitizing effect in A549 cells exposed to both of 60Coγin A549 cells exposed both of 60Coγand UV rays. (3) SCGE assay suggested that 4-AN might exert its effect through inhibition of repair of SSBs. (4) FCM showed that 4-AN acted through inhibition of delay of G2/M phase when exposed to high doses of 60Coγand UV rays respectively. (4) Western blot assay suggested that expression of Cyclin B1 was distinctly different between the single radiation group and the group of 4-AN and radiation combined, with marked decrease in the latter group. It may be speculated that 4-AN downregulated expression of Cyclin B1 to prevent the arrest of G2/M phase induced by radiation, thus leading to unsuccessful repair and apoptosis of A549 cells.