The Role Of ATM Or ISG15 In Radioresistant Cancer Cells

Section ? Acquired radioresistance:The role of ATM in radioresistance of breast cancer cellsRadioresistance includes resistance developed in the procedure of treatment and intrinsic resitance harbored by cancer itself.The development of radioresistance greatly restricts the effect of radiotherapy.In the development process of radioresistance,many pathways play important roles,such as DNA damage repair pathway and cellular autophagy.Studying the role of these pathways,and how radioresistance is generated in cancer cells,would provide new methods for radiosensitizing and better treatment for patients.To mimic the development of radisoresistance in the treatment of breast cancer,we established one radioresistant breast cancer cell line MD-PR through repeated low dose irradiation,referring to the treatment procedure of breast cancer.Western blotting and immunofluorescence are used to detect the expression and dynamic of ?-H2 AX,which could reflect the repair efficiency of broken double strand DNA after irradiation.Fluorescence reporter plasmid is used to directly reflect repair efficiency.We found that in MD-PR cells,expression of ATM is much higher than that in MD-PB cells.Through interfering the expression of ATM or using ATM specific inhibitor,we found that through elevating the expression of ATM,MD-PR cells generates higher repair efficiency of broken double strand DNA which promotes cancer cell survival after being irradiated and leads to radioresistance.In summary,through mimicking clinic procedure,we establishedone radioresistant breast cancer cell line and found a new role of ATM in radioresistance in breast cancer cells,which indicates that combination of radiotherapy with ATM-targeted inhibition might be a new way to improve the efficacy of cancer treatment.Section ? Instrinsic radioresistance:The role of ISG15 in chemo/radioresistance of pancreatic cancer cellsThrough mass spectrum analysis of protein expression profile in radioresistant MD-PR and MD-PB cells from Section I,we found that ISG15 expression was correlated with cancer radioresistance.As a ubiquitin-like protein,ISG15 plays an important role in anti-bacteria and virus immunonal response.Meanwhile,ISG15 infulences cell autophagy though the mechanism remains unclear.In recent years,ISG15 was found related with oncogenesis,development of cancer,cancer immunity and cancer treatment.In this section,we compared expression level of ISG15 in cancer and non-cancer tissue of pancreatic cancer,which harbors intrisic radioresistance.We analyzed the functionand related mechanism of ISG15 in pancreatic cell line PANC-1 and Mia Paca-2 by knock-down and overexpression ISG15.In these experiments,we found that the expression level of ISG15 was higher in cancer tissue compared with non-cancer ones,and the expression of ISG15 was correlated with prognosis of the pateints.Knock-down of ISG15 sensitized pancreatic cells to irradiation and chemicals(Gemcitabine).Experiments showed that ISG15 knock-down downregulated autophagy levels in cancer cells,especially the conversion of LC3.Further experiments showed that through influencing the expression of ATG7,ISG15 modulated LC3II/I ratio and cell autophagy level and finally impacted cell sensitivity towards irradiation and chemicals.Resutls of in vivo experiments confirmed the role of ISG15 in promoting pancreatic cancer prolifetion and resistance to Gemcitabine.In this section,we presented for the first time that ATG7 expression was modilated by ISG15.In this section,we clarified the role of ISG15 in chemo/radiopresistance of pancreatic cancer cells.