The tumor growth originating from ptgs2- or ptges-KO cells was significantly slower than that of tumors originating from scramble or ptgs1-KO cells (Fig. 2B), whereas the tumor growth was not significantly different between ptgs1 KO- and scramble-derived tumors and between ptgs2 KO- and ptges KO-derived tumors. Here, PTGS2 is linked to neoplasm.