Figure 2.
Long-term expression of p21Waf1/Cip1 is essential for radiation-induced senescence in HNSCC cells. (a) quantitative RT-PCR analysis of p21 mRNA expression in HNSCC cells treated with 4-Gy ionizing radiation and collected at indicated time points. Error bars represent S.D. of each sample performed in duplicate. (b) Western blot showing differences in p21 expression between wtp53 and mutp53 HNSCC cells when treated with 4-Gy ionizing radiation; protein lysates collected at the indicated time points. (c) Western blot results confirming lentiviral p21 knockdown in HN30 cells and their lack of response to ionizing radiation (d) Clonogenic assay showing resistance to ionizing radiation in HN30 cells with knockdown of p21 when compared with Lenti control. (e) SA-β-gal staining was performed 4 days after the cells were exposed to 4-Gy ionizing radiation. (f) Quantitation of SA-β-gal-positive senescent cells (those staining blue) from four randomly selected fields