Western blot but not immunohistochemistry reveals downregulation of COX2 expression in association with EBV infection. Monclonal antibody was used to semiquantitatively measure COX2 protein. A. Western blot of AGS cell lysates (loaded onto the gel at 50, 100, or 150 ug per lane) showed that EBV positive AGS cells had lower expression of COX2 than did EBV negative cells. However, COX2 immunohistochemistry revealed no discernible difference between EBV negative (B) and EBV positive (C) AGS cell lines. Likewise, COX2 immunohistochemistry of primary gastric adenocarcinoma tissue revealed no visible difference in COX2 expression between EBV negative cancer (D) versus EBV positive cancer (E).