XRCC6 and head and neck squamous cell carcinoma: Interestingly, most CIDGS-related genes, such as XRCC6, ST13, PES1, EFHD2, APOL2, ACTR2, and CDCP1, were markedly upregulated in HNSCC tumor samples, whereas several other genes, such as MARCO, MRC1, and CD83, were upregulated in healthy samples (Figure 6A).