Differential expression of proteins in radioresistant and radiosensitive human squamous carcinoma cells.

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 electrophoresis 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 clinical parameters 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 radio-resistant cell lines SQ-20B, JSQ-3, and SCC-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 radio-sensitive 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 expression of cellular radioresistance or radiosensitivity.

IMPLICATIONS

This study will facilitate the characterization of these proteins correlated with the radiation response-specific phenotype.