Differential Expression of Proteins in Radioresistant and Squamous Carcinoma Cells

Abstract

Background: Previous studies support a genetic basis for cellular radioresistance. The associated biochemical and molecular events, however, are not fully understood. Purpose: We investigated the differential protein pattern as a molecular determinant of resistance or sensitivity of head and neck squamous carcinoma cells to ionizing radiation. Methods: Using two-dimensional polyacrylamide gel electro-phoresis followed by computer-assisted quantitative analysis, we compared the protein profiles of three relatively radioresistant and three relatively radiosensitive head and neck squamous carcinoma cell lines (previously characterized by in vitro and clinicale paraments as radioresistant or radiosensitive) to determine which proteins were consistently expressed or enhanced in the radioresistant compared with the radiosensitive phenotype. Results: Our analysis indicated that 14 proteins were preferentially expressed in the radioresistant cell lines SQ-20B, JSQ-3, andSCC-35 with one protein (molecular mass of 92 kd and pI of 5.5) distinctly expressed in the radioresistant cell lines. Four proteins were enhanced by greater than 10-fold, three were enhanced fivefold to 10-fold, and six were enhanced twofold to fivefold in the radioresistant cell lines. In addition, we observed a second set of 15 proteins preferentially expressed in the radiosensitive cell lines SQ-9G, SQ-38, and SCC-9. A 40-kd protein (pI 7.1) was distinctly expressed in the radiosensitive cell lines. The remaining radiosensitive cell-specific proteins were enhanced by greater than 10-fold (two proteins), fivefold to 10-fold (two proteins), or twofold to fivefold (10 proteins) compared with their counterparts in the radioresistant cell lysates. Conclusion : These results provide evidence for differential protein expression associated with phenotypic express of cellular radioresistance or radiosensitivity. Implications : This study will facilitate the characterization of these proteins correlated with the radiation response-specific phenotype. [J Natl Cancer Inst 84: 622–628, 1992]