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[Radiation-induced apoptosis of two nasopharyngeal carcinoma cell lines]
1Radiation Biology Department, Cancer Institute (Hospital), Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing.
Objective:
To study apoptosis induced by radiation in two nasopharyngeal carcinoma (NPC) cell lines, CNE and CNE-2.
Methods:
Hoechst 33342 staining, immunocytochemical staining, RT-PCR, DNA dot blotting and Southern blotting were used to identify apoptosis.
Results:
A single dose of X-irradiation resulted in apoptosis, the apoptotic index (AI) was time- and dose-dependent. Different apoptotic responses existed in the two cell lines. Immunocytochemical staining showed that bcl-2 protein was strongly positive in CNE but negetive in CNE-2. However, RT-PCR revealed p53 mRNA in CNE-2 but not in CNE. p53 and bcl-2 genes were both present in the two cell lines as shown by DNA blotting, but the 2.8 kb fragment of the p53 gene was much lower than the 5.6 Kb fragment in CNE which was clearly shown in Southern hybridization, suggestive of partial deletion of p53 gene in CNE.
Conclusion:
Apoptotic response to radiation is different in 2 NPC cell lines. CNE is more radio-resistant than CNE-2. Overexpression of bcl-2 protein and partial deletion of p53 gene may explain their difference in radio-sensitivity.