Figure 2. Enhanced CSC properties in A549-RR and H1299-RR cells. (A) Radioresistant and control cells were grown in an ultra-low attachment plate as indicated for 14 days. Representative images of tumor cell spheres were taken for quantification. (B) The diameter and number of tumor cell spheres in (A). (C) CD44 and CD133 protein levels in cell lysates measured by Western blot. (D) Immunofluorescence images of CD44 and CD133 (red) in radioresistant and control cells. Nuclei are stained with PI (blue). (E) Representative images of the xenografts. (F) Tumor incidence in xenograft of A549-RR and A549-control cells. (G) Tumor volume was measured once every 2 days and was calculated as: V = (width2×length)/2. All data used in RR cell lines were based on cells between 5 and 6 weeks post radiation treatment. All results were from three independent experiments, and the data are shown as mean ± SD. P-values were calculated by student’s t-test.