Lack of a correlation between p53 protein expression and radiation response in human tumor primary cultures

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Abstract
We investigated the possible relationship between immunohistochemically detected p53 expression and in vitro response to γ‐irradiation in 24 primary cultures of human ovarian cancers and cutaneous melanomas. The frequency of p53‐positive tumors was around 60% within each tumor histotype. The range of the surviving fraction at 2 Gy (SF2) was similar in p53‐positive (0.10‐0.76) and p53‐negative (0.23‐0.65) tumors, with median values of 0.36 and 0.33, respectively. No differences were observed in the accumulation of DNA‐double strand breaks, assessed by neutral filter elution after exposure to 50 Gy, between p53‐positive and p53‐negative tumors. As regards DNA lesion repair, after 2 h of recovery the percentage of rejoined DNA‐double strand breaks ranged from 19% to 99% in the different cultures, but again the distribution of values was similar for p53‐positive and p53‐negative tumors. Specifically, the median percentage of repaired DNA‐double strand breaks was 70% and 74% in the two groups. On the whole, our data do not support the hypothesis that p53 overexpression is a major determinant of in vitro radiation response.

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