CHEK2 and central nervous system cancer: For example, CD133-expressing glioma cells are more resistant to radiation treatment than CD133-negative cell subpopulations and that the preferential checkpoint response in CD133-positive cells is responsible for this radioresistance.22 Consistent with this result, we found increased radioresistance and CHK2 phosphorylation specifically in mH2A1-depleted bladder cancer cells.