Role of Bcl-2 family proteins (Bax, Bcl-2 and Bcl-X) on cellular susceptibility to radiation in pancreatic cancer cells

• Published in: European journal of cancer (1990) 1999-09, Vol.35 (9), p.1374-1380
• Main Authors: Lee, J.-U, Hosotani, R, Wada, M, Doi, R, Kosiba, T, Fujimoto, K, Miyamoto, Y, Tsuji, S, Nakajima, S, Nishimura, Y, Imamura, M
• Format: Article
• Language: English
• Subjects: apoptosis; Biological and medical sciences; Blotting, Western; cell line; Gastroenterology. Liver. Pancreas. Abdomen; Humans; Liver. Biliary tract. Portal circulation. Exocrine pancreas; Medical sciences; Mutation - genetics; oncoproteins; pancreatic cancer; Pancreatic Neoplasms - genetics; Pancreatic Neoplasms - radiotherapy; Proto-Oncogene Proteins c-bcl-2 - genetics; Proto-Oncogene Proteins c-bcl-2 - physiology; radiation; Radiation Tolerance; Staining and Labeling; Tumor Cells, Cultured; Tumors
• ISSN: 0959-8049; 1879-0852
• DOI: 10.1016/S0959-8049(99)00134-3

The aim of this study was to examine Bax, Bcl-2 and Bcl-X L proteins in human pancreatic cancer cell lines and to clarify the mechanism of radiation resistance. PANC-1 and AsPC-1 pancreatic cell lines were used, both having mutated p53. Radioresistant PANC-1/Rad cells and AsPC-1/Rad cells were obtained by repeated 5 Gy irradiation of PANC-1 cells and AsPC-1 cells, respectively. Radiation was found to inhibit the growth of PANC-1 cells and AsPC-1 cells. After exposure to radiation, detached cells were subjected to FITC-TUNEL staining to calculate the ratio of apoptosis. TUNEL positive ratios increased dose-dependently in both cell lines. Western blotting showed that the basal level of the Bax/Bcl-2 ratio reflected the radiosensitivity of these cell lines, and Bax expression was obviously upregulated after irradiation in the presence of mutated p53, but Bcl-2 expression remained almost constant. Both PANC-1/Rad and AsPC-1/Rad cells had greater Bcl-X L expression than the parental cells, and the basal level of the Bax/Bcl-2 ratio was no longer predictive of radiosensitivity. Upregulated expression of Bax protein after irradiation was not related to induction of apoptosis in these cells, suggesting that overexpression of Bcl-X L and functional reconstruction of Bcl-2 family proteins are important factors in acquired radioresistance.