PTGS2 and cancer: PTGS2 was reported to be overexpressed in cancer cells and associated with the resistance of cancer cells to IR.23 Eberhart et al find that PTGS2 was upregulated in a number of human cancers.16, 17 Petersen et al18 found that inhibitors of PTGS2 could act as radiosensitizing agents and reduce the proliferation rate of tumor cell lines.