Cell proliferative activity estimated by histone H2B mRNA level correlates with cytogenetic damage induced by radiation in human glioblastoma cell lines

Abstract

We studied the relationship between proliferative activity and radiation-induced DNA damage in human malignant gliomas in vitro. Nine human glioblastoma established cell lines were gamma-irradiated (60Co) over a dose range of 0-10 Gy. H2B and H4 histone mRNA level was assessed with quantitative RT-PCR technique (TaqMan) and histone labeling index (HLI) with in situ hybridization to define proliferation rate, while cytochalasin-block micronucleus assay was performed to measure cytogenetic damage. Micronucleus frequency correlated with H2B mRNA level (Spearman's R up to 0.82 at 8 Gy), HLI, nuclear division index (NDI) and percentage of binucleated cells (%BNC). There was a high correlation between H2B mRNA level and NDI (R = 0.80) as well as %BNC and HLI (R = 0.72). Histone H2B and H4 mRNA level (not significant), HLI, NDI, and %BNC (significant) were higher in cell lines sensitive to DNA damage. Proliferative activity correlates with radiation-induced DNA damage in human glioma cell lines. Histone H2B mRNA level and HLI may be a useful molecular predictor of the tumour response to radiation treatment in gliomas of the same histological grade, however the risk of potentially more rapid tumour-cell repopulation must be considered. Presumed protective activity of histones against radiation-induced DNA damage was not confirmed at the transcript level.