Fig. 1.

Clonogenic survival assays performed to assess the surviving fraction after 2 Gy of radiation (SF-2Gy) identified the range of radioresistance in 14 HPV(–) HNSCC cell lines (48%–72%). (A) Four radioresistant cell lines and four radiosensitive cell lines were selected based on SF-2Gy in each HPV(–) HNSCC cell line (62%–72% vs. 48%–51%; p = 0.028). On comparison of the radioresistant and radiosensitive cell lines, 41 genes with significant correlation with radioresistance were identified; 6 genes were positively correlated with radioresistance and 35 genes were negatively correlated with radioresistance. (B) Relative gene expression levels of these 41 genes in the four radioresistant and four radiosensitive cell lines are depicted. HPV, human papillomavirus; HNSCC, head and neck squamous cell carcinoma.