engleski

Characterization of human primary lung fibroblasts exposed to repeated low doses of gamma-rays

Tumor cells exposed to fractionated ionizing irradiation, with a high total dose (15 Gy or more), may become resistant to chemotherapeutic agents. The aim of the present study was to determine whether the same phenomenon will occur in normal human cells after exposure to a low total dose of 1, 7 Gy of irradiation divided in a small number of fractions. Since c-myc, c-Ha-ras and p53 oncogenes are involved in both drug-resistance phenomena and the process of neoplastic transformation, we also examined their expression in parallel experiments. Primary human lung fibroblasts were irradiated five days with daily dose of 0, 17 Gy of gamma rays. The sensitivity of preirradiated cells (after 5 or 10 gamma-ray-fractions) to different cytostatics was determined by colorometric MTT dye assay and compared to the sensitivity of control cells. The expression of c-myc, c-Ha-ras and p53 oncogenes in control and preirradiated cells was detected immunocytochemically. The results show that preirradiated normal cells with low total dose became resistant to vincristine and vinblastine, but did not change their sensitivity to cisplatin. The expression of examined oncogenes was the same in preirradiated and contol group of cells. Our results suggest that irradiation of normal cells with multiple small doses of gamma rays may change the susceptibility to chemical agents. These data have practical application to radiation protection.

human primary lung fibroblasts ; gamma-rays

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