Abstract 3303: Radioresistance in glioma stem cells driven by Rad51 dependent homologous recombination repair

We examined co-expression of stem cell markers with RAD51 protein at whole population level using western blotting, immunocytochemistry and RT-PCR in cultured cells and immunohistochemistry in tumor material. Single cell expression was analysed using the Fluidigm C1 platform. We examined the effect of two specific inhibitors of RAD51 (B02, RI-1) on the same cell pairs in vitro and used the γH2AX assay to assess differences in repair kinetics. We used subcutaneous models of glioma to evaluate the effect of one of these agents (RI-1) on tumour growth delay with and without fractionated radiation doses in vivo.Primary glioma stem cells expressed high levels of RAD51 protein and exhibited high numbers of foci per nucleus following radiation exposure. Levels of both protein and repair foci fell after cells were transferred to differentiating conditions (serum+BMP4), as did expression of stem cell markers (NESTIN, SOX2). Single cell analysis showed a highly significant association between SOX2 and RAD51 expression (P< 0.0001). A similar association between RAD51 expression and stem cell marker expression was demonstrated in a series of glioblastoma specimens. When primary glioma cultures were treated with B02, RI-1 or siRNA targeting RAD51 in vitro, significant radiosensitisation was achieved with dose modifying factors ∼1.4 after single radiation doses. Delayed repair of DNA double strand breaks was also apparent, with a higher proportion of γH2AX foci unresolved in treated ce...
Source: Cancer Research - Category: Cancer & Oncology Authors: Tags: Tumor Biology Source Type: research