Figure 1. Distribution of HBV integration breakpoints throughout the human genomes in 426 paired samples.

(a) Distribution of integration breakpoints across the human genome in 426 paired samples. Each bar represents the sample frequency of HBV integration breakpoints at a particular locus in the human genome (hg19). Tumour (red) and non-tumour (dark blue) samples with HBV integrations are shown on the inner and outer circles, respectively. Histogram axis units represent number of samples. Some loci with a high frequency of integration are marked. GENE. (b) Comparison of the breakpoints in the CpG island region of 426 paired samples. The expected (assuming uniform, random distribution, yellow) and the observed (actual numbers, tumour: blue; normal liver tissue: purple) percentages of HBV integration breakpoints of tumour and non-tumour samples in CpG islands region are shown. P values were calculated by χ² test. (c) Distribution of integration breakpoints in the fragile region (FR) of 426 paired tumor and non-tumor tissues. The expected (assuming uniform, random distribution, yellow) and the observed (actual numbers, tumour: blue; normal liver tissue: purple) ratios of HBV integration breakpoints in common fragile region, rare fragile region and non-fragile region are shown. P values were calculated by χ² test. Common: common FR; rare: rare FR; NFRs: non-fragile regions.