PTGS2 and cancer: To investigate whether TS and single saponins 1–5 from A. flaccida can inhibit COX-2/PGE2 pathway which may be involved in their proapoptotic effects on cancer cells, we first measured COX-2 mRNA with or without TS and triterpenoid saponins treatments in cancer cells by performing quantitative real-time PCR assay and also evaluated COX-2 expression in tumor cells at the protein level using western blot.