DDB2 and xeroderma pigmentosum: Exposure to hyperoxic conditions significantly increased the expression of damage-specific DNA binding protein 2 (DDB2) and xeroderma pigmentosum, complementation group C (XPC) (Figures 8(a) and 8(f)) in Ctr, CMV-NQO1, NQO1-NQO1, and SNP-transfected cells.