Phosphorylation of histone H2AX in response
to DNA damage produced by DNA interstrand
Doctoral thesis, UCL (University College London).
Interstrand crosslinking (ICL) agents such as nitrogen mustards and platinum compounds are mainstays of cancer chemotherapy. SJG-136 is a highly potent ICL agent currently in clinical trials. γ-H2AX foci form at the sites of ionizing radiation-induced double strand breaks (DSBs) and their persistence is an indication of radiosensitivity. The aim of this study was to establish if γ-H2AX is a suitable marker of ICL-associated damage. γ-H2AX foci can be detected at pharmacologically relevant doses of ICL agents (0.5 μM HN2, 5 μM cisplatin, 0.01 nM SJG-136), lower than those used to detect ICLs in the modified comet assay (5 μM HN2, 10 μM cisplatin, 1 nM SJG-136). The peak of foci formation followed the peak of ICL formation, and persistence of foci was observed in CHO and human cells defective in either ICL unhooking or homologous recombination (HR). Persistence of foci was also detected in A2780 ovarian cancer cells compared to the paired A2780 cisplatin resistant cells. γ-H2AX was found to be a sensitive marker of ICL-associated damage independent of DSB formation and a potential tool to distinguish ICL-sensitive cells in vitro. γ-H2AX has also been investigated as a pharmacodynamic endpoint in clinical studies. Maximal foci formation was observed at 24 hours post-infusion of SJG-136 in peripheral blood lymphocytes obtained from all 16 patients in a phase I clinical trial. Increased foci induction was also detected in two tumour biopsies obtained from patients treated with SJG-136. In contrast to γ-H2AX, a higher level of RAD51 foci was observed in ICL unhooking defective CHO cells compared to the wild type, whereas no foci were observed in HR defective cells following cisplatin treatment. Therefore, both γ-H2AX and RAD51 foci could be useful markers of ICL-associated damage in clinical settings.
|Title:||Phosphorylation of histone H2AX in response to DNA damage produced by DNA interstrand crosslinking agents|
|Additional information:||Authorisation for digitisation not received|
|UCL classification:||UCL > School of Life and Medical Sciences > Faculty of Medical Sciences > Wolfson Institute and Cancer Institute Administration > Cancer Institute|
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