XRCC5 and neoplasm: Figure 6B shows that human-specific Ku80 biomarkers were widely stained in tumor tissues, including epithelial cells and fibroblasts, suggesting that FaDu and CAF cells injected into the mice cheeks were well involved in xenograft tumor formation. FaDu-derived mice tumor tissues co-injected with CAF-D showed higher COL3A1, COL6A6, COL25A1, and COL26A1 expression levels than those co-injected with CAF-P (Figure 6C). Interestingly, MMP2, MMP9, and MMP14 mRNA expression was opposite to that of the collagen mRNA level (Figure 6D).