Fig. 1
DNA damage signaling in radioresistant 22Rv1 (RR) PCa cell lines. a Schematic representation of 22Rv1-RR in vitro generation upon 20 fractions of 2.5 Gy for 28 consecutive days for a total dose of 50 Gy. Cells recover the growth properties within ~2–3 months in culture after the acute effect of ionizing radiation. Morphological differences were observed in cells between short-term and long-term effect of ionization. b Representative images of the stained colonies submitted to a range of 0 to 8 Gy. Images were taken by stereomicroscope Olympus S2X16 using a digital camera Olympus SC180, 0.7×. c Cell survival fraction of 22Rv1-RR and parental (P) cells represented through linear-quadratic model (LQ = (S = e – (xD + BD2))), ****P value < 0.0001. d Heatmap of RT2 Profiler Human DNA Damage Signaling Pathway PCR array comparing between 22Rv1-P and 22Rv1-RR samples (four biological replicates), highlighting relative mRNA expression levels of TP53, normalized by HPRT1 gene expression levels (housekeeping). In blue, less expressed samples (−1) and in red, high expressed samples (1). Results are presented as mean ± SD of at least three independent experiments. ***P value < 0.001. e Immunofluorescence staining of γ-H2AX foci (merged with DAPI for nuclei staining) in 22Rv1-P and RR cells control (0 Gy) and after 2.5 Gy IR (30 min and 24 h after). Images were taken using Olympus IX51 microscope at ×400 magnification (scale bar 20 μm). f, g Effect of 2.5 Gy irradiation treatment in DNA damage of 22Rv1-P and RR cells by comet assay. The results are the mean of at least 100 comets per condition. ns not significant; **P value < 0.01; ***P value < 0.001; ****P value < 0.0001. Representative images of the DAPI-stained single cells were taken using Olympus IX51 microscope at 400x magnification (scale bar 20 μm). The graph represents tail moment which means tail length × % of DNA in the tail. Red line represents the median value. Fr fraction, IR ionizing radiation, P parental, RR radioresistant
