No association between radiosensitivity and TP53 status, G(1) arrest or protein levels of p53, myc, ras or raf in human melanoma lines

Purpose: First, to investigate whether TP53 status and/or radiation-induced G(1) arrest are associated with radiosensitivity, and, second, to detect p ossible associations between protein levels of p53, myc, ras or raf and rad iosensitivity and to investigate whether hypoxia-induced changes in the lev els of these proteins are related to hypoxia-induced changes in radiosensit ivity in human melanoma lines. Materials and methods: Radiosensitivity was assessed by clonogenic assays. TP53 status was investigated at the genomic level by constant denaturant ge l electrophoresis and at the cDNA level by sequencing. G(1) arrest was inve stigated by flow cytometric analysis of DNA. Protein expression of hypoxia- treated and untreated cells was assessed by flow cytometric measurements an d Western blotting. Results: Considerable differences in radiosensitivity were detected among m elanoma lines with wild-type TP53. Only a fraction of the melanoma cells, d iffering between the lines, was arrested in G(1). No association between th e fraction of arrested cells and radiosensitivity was detected. Protein lev els of p53, myc, ras or raf were not associated with radiosensitivity. Hypo xia-induced changes in p53, ras and raf levels were detected in all cell li nes. Changes in the level of myc protein were detected for two of the four cell lines, while hypoxia-induced changes in radiosensitivity were observed only for one. Conclusions: Differences in radiosensitivity among melanoma lines cannot be elucidated by TP53 status, differences in G(1) arrest or different levels of p53, myc, ras or raf proteins. Hypoxia-induced changes in p53, myc, ras or raf levels do not seem to be related to hypoxia-induced changes in radio sensitivity.