Cancer Stem Cells from Tumor Cell Lines Activate the DNA Damage Response Pathway after Ionizing Radiation More Efficiently Than Noncancer Stem Cells

Figure 1

HeLa SP are positive for cancer stem cell markers. (a) Microscopy of cultures derived from the HeLa cell line growing as monolayer (HeLa ML) and as spheres (HeLa SP), objectives 20x and 40x, respectively. (b) Flow cytometry analysis of HeLa ML and HeLa SP cultures for CD49f and high ALDH activity, with the gates representing the percentage of cell populations positive for staining. For HeLa SP, 87% of cells were positive for CD49f, nearly 12% were positive for high ALDH activity, and for both markers, 11% were positive. In HeLa ML, 88% of cells were negative for both markers, while less than 1% were positive for the latter.

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