At this point, the majority of NRAS-injected Cox2-knockout animals develop macroscopic liver tumors (Figures 3E–3G) with microscopic features of hepatocellular carcinoma (HCC) (Figure 3F), whereas most NRAS-injected animals with normal Cox2 function have no tumors (Figure 3G). Here, PTGS2 is linked to hepatocellular carcinoma.