XRCC5 and neoplasm: Figure 3 shows that human species-specific Ku80 biomarkers are broadly stained in tumor tissues such as epithelial cells and fibroblasts, suggesting that FaDu and CAF cells injected into the mice cheeks were well involved in tumor xenograft formation. Fibroblast-specific α-SMA staining was also detected inside the epithelial tumor cells (Figure 3).