H2AX and gastric cancer: Western blot analysis indicated that DNA-PKcs, ATR, Phospho-ATR, ATM, Phospho-ATM, γH2AX, and H2AX were upregulated in oxaliplatin-resistant gastric cancer cells, indicating that DNA damage repair response was activated in SGC-7901-R and KATO III-R cells (Fig. 4A, B).