Expression of Ku Correlates with Radiation Sensitivities in the Head and Neck Cancer Cell Lines

Lee,  Sang wook; Yu,  Eunsil; Yi,  So Lyoung; Son,  Se Hee; Kim,  Jong Hoon; Ahn,  Seung Do; Shin,  Seong Soo; Choi,  Eun Kyung

J Korean Soc Ther Radiol Oncol > Volume 22(3); 2004 > Article

Original Article

The Journal of the Korean Society for Therapeutic Radiology and Oncology 2004;22(3): 208-216.

Expression of Ku Correlates with Radiation Sensitivities in the Head and Neck Cancer Cell Lines

Sang wook Lee, Eunsil Yu, So Lyoung Yi, Se Hee Son, Jong Hoon Kim, Seung Do Ahn, Seong Soo Shin, Eun Kyung Choi

¹Departments of Radiation Oncology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea. lsw@amc.seoul.kr
²Departments of Pathology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea.

ABSTRACT

PURPOSE:
DNA-dependent protein kinase (DNA-PK) is a serine/threonine kinase consisting of a 470 kDa catalytic subunit (DNA-PKcs) and a heterodimeric regulatory complex, called Ku, which is composed of 70 kDa (Ku 70) and 86 kDa (Ku 80) proteins. The DNA-PK has been shown to play a pivotal role in rejoining DNA double-strand-breaks (dsb) in mammalian cells. The purpose of this study is to examine the relationship between the level of Ku expression and radiation sensitivity. METHODS AND MATERIALS: Nine head and neck, cancer cell lines showed various intrinsic radiation sensitivities. Among the nine, AMC-HN-3 cell was the most sensitive for X-ray irradiation and AMC-HN-9 cell was the most resistance. The most sensitive and resistant cell lines were selected and the test sensitivity of radiation and expression of Ku were measured. Radiation sensitivity was obtained by colony forming assay and Ku protein expression using Western blot analysis.
RESULTS:
Ku80 increased expression by radiation, wheres Ku70 did not. Overexpression of Ku80 protein increased radiation resistance in AMC-HN9 cell line. There was a correlation between Ku80 expression and radiation resistance. Ku80 was shown to play an important role in radiation damage response.
CONCLUSION:
Induction of Ku80 expression had an important role in DNA damage repair by radiation. Ku80 expression may be an effective predictive assay of radiosensitivity on head and neck cancer.

Key Words: Ku70/80, irradiation, Head and neck cancer cell line