Fig. 5

Principal component analysis of the clonogenic survival data enables the extraction of scores of radioresistance. Standardized clonogenic survival data were subjected to principal component analysis (PCA). In (a), the proportions of variance for the six PCs and the scaled loadings of the variables on the first PC that accounts for 76.9 % of the total variability in the data are shown. The first PC exhibits well-balanced loadings for the measured variables. The scores of the nine cell lines on the first two PCs are presented in (b). The resulting two-cluster solution is displayed in the space of the first two PCs that reflect 90.04 % of the total variability in the data (c). Pearson correlation analyses of the first PC were conducted with the estimated parameters extracted from the fitted regression models (d, e, f)