The Patterns of Expression of p53, bcl-2 and Bax after Irradiation in Cell Lines of Squamous Cell Carcinoma of Head and Neck

Jung, Yoo Seok; Baek, Chung Hwan; Ko, Ye Jeung

Abstract

BACKGROUND AND OBJECTIVES: Squamous cell carcinoma of head and neck (HNSCC) undergoes a generally poor hospital course, and response of radiotherapy remains in questionable status. For this carcinoma, the clinical courses, biological behaviors and responses to radiotherapy are variable among cases and difficult to predict accurately.
MATERIALS AND METHODS
As a trial to elucidate the prognostic factors of HNSCC after radiotherapy, several responses following irradiation of HNSCC cell lines and the expressions of apoptosis-related markers, such as p53, bcl-2, and Bax, were evaluated in this study.
RESULTS
Among the eight HNSCC cell lines, the AMC-HN 1 was considered to be radioresistant, the PCI-1 was radiosensitive, and the AMC-HN 8 showed intermediate response. In immunohistochemistry of p53, AMC-HN 1 was negative, PCI-1 was strongly positive, and AMC-HN 8 was weakly positive. However, the analysis of mRNA using RT-PCR implied different expressions of p53 in the mRNA level. All 3 cell lines showed the p53 mRNA expressions. After irradiation of 2 Gy (137Cs), changes in the expressions of apoptosis-related protein (p53, bcl-2, Bax) were analyzed with the Western blot assay. The p53 and bcl-2 did not show any difference in the expressions between the irradiation group and the non-irradiation group. However, there was a significant difference in the Bax expression in the radiosensitive cell line (PCI-1) after irradiation.
CONCLUSION
Those results might imply some roles of Bax in apoptotic responses following radiotherapy. Therefore, further studies should look into finding other possible factors and markers of HNSCC after radiotherapy and the precise role of Bax.