In vitro studies illustrated that curcumin treatment limited the proliferation and caused cell cycle arrest in HT-29 colon cancer cells and PLC/PRF/5 liver cancer cells via the inhibition of cyclin D1, with the downregulation of NF-κB and cyclooxygenase-2 (COX-2) signalling [50,51,52,53]. This evidence concerns the gene PTGS2 and liver cancer.