Relationship Between The Expression Of DNA-PK And Radiosensitivity In Nasopharyngeal Carcinoma

Background and objectives:Nasopharyngeal carcinoma (NPC) is one of the common malignant tumors in China, especially in the southern part of the country. Owing to its special anatomic site and characteristic of radiosensitivity, integrated treatment pattern which radiotherapy contributes mostly was still a prevalent means presently. The 5- year survival rate was over 50% with radiotherapy alone. These years,the curative effect of NPC was improved by the development of radiation equipments, radiotherapy techniques, radiophysics and radiobiology. As we all known, pathologic category, clinical stage, age and status impact the progonosis of NPC patients, but in our common clinical work, we can see the similar character of above factors patients had so different curative effect. One of the therapy failure reason is radioresisitant. So, to explore mechanism of radioresistance and to search for some radiosensitizing approaches are one way to improve the curative effect. At present, to predict the radiosensitivity before radiotherapy is one of the hot issues in radiobiology.It was well known that the radiosensitivity is mainly determined by the number of DSB induced by irradiation and the extent of its repair. In mammalian cells, the nonhomologous end joining (NHEJ) is the predominant DSBs repair system which is composed of DNA-PK, XRCC4, and DNA ligaseâ…£. DNA-PK is a component trimetric enzyme consisting of a 460 kDa catalytic subunit (DNA-PKcs), which can phosphorylates XRCC4 and DNA ligaseâ…£to rejoin DSB, and a heterodimeric modulated component called Ku which playing a role in identifying, combining, arranging the DNA ends and recruiting...