The Study On The Radiosensitizing Effective And Its Mechanisms Of PARP-1 Inhibitor On Lung Cancer Cells

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 researches show that PARP inhibitors are expected to be the medicine targeting to some DNArepairdefective 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 The aim of this study was to determine whether or not HS-10160,a novel potent poly(ADP-ribose)polymerase(PARP)inhibitor,could enhance the radiation sensitivity of lung cancer cells both in vivo and in vitro model.Methods The radiosensitizing effect of PARP-1 inhibitor was evaluated on the basis of cell death,clonogenic survival and tumor xenograft progression.The mechanism was explored by the expressed changes of key proteins(WB),DNA DSB repair after irradiation(?H2AX,IF),silence XRCC1 gene(XRCC1-sh RNA,WB)and the radiosensitizing effect tumor xenografts of mice.We chose 35 nude mice,injected H460 tumor cells into their right legs,until the tumor diameter grew to 8mm we stared to treatthem.The mice were put into different groups: blank control group,medicine group,radiotherapy group and the medicine combined with radiotherapy group.The medicinegroup wastreated with PARP-1 inhibitors dose: 2ug/0.1ml/d/;on the eighth day after the injection;radiotherapy group were treated with irradiation dose is 2Gy * 5Fin tenth days with 6MV-X-ray.The drug was lavaged to the mice.The combined group received the treatment the same as the medicine and radiotherapy group,2 hours lavaged before radiotherapy.Medicine group and combined group were given 7 days of continuous administration.Since every l days after the end of treatment were measured with vernier caliper diameter of tumor,observe the growth status of different groups of mice transplanted tumor,draw survival curve and the tumor growth curve,observe the anti-tumor effect of PARP-1 inhibitors in miceResults PARP-1 inhibitor alone was slightly toxic to human lung cell lines.Apoptosis was increased and clonogenic survival was decreased when PARP-1 inhibitor was combined with ionizing radiation(IR).The mechanism of radiosensitizing effect of PARP-1 inhibitor is related with increasing cell death and apoptosis,preventing DNA repairing,regulating cell cycle.In vivo,PARP-1 inhibitor as a single agent had no effect on tumor growth,whereas 2 Gy alone once daily for 7 days markedly delayed tumor growth,and no severe toxicity was observed.Conclusion This study suggests that HS-10160 warrants consideration for further development in combination with radiotherapy in clinical oncology settings such as lung cancer.