XRCC4 and lip and oral cavity carcinoma: The mRNA expressions for DNA repair signaling [24], including HR-associated genes (BRCA1 DNA repair-associated (BRCA1), BRCA2, RAD50 double-strand break repair protein (RAD50), RAD51 recombinase (RAD51), FA complementation group D2 (FANCD2), and partner and localizer of BRCA2 (PALB2)) and NHEJ-associated genes (X-ray repair cross-complementing 6 (XRCC6), XRCC5, XRCC4, and protein kinase, DNA-activated, catalytic subunit (PRKDC)), were examined for PHA-incubated oral cancer cells.