Mechanisms of action of combination curcumin and chemotherapy drugs in vitro and in vivo. Co-treatment with curcumin and chemotherapy drugs such as docetaxel, metformin, 5-fluorouracil, doxorubicin, cisplatin, and celecoxib enhance the synergistic effect via modulating several signaling pathways and thus inhibit cancers such as prostate, hepatocellular, gastric, Hodgkin lymphoma, bladder, and colorectal. Akt: protein kinase B; COX-2: cyclooxygenase-2; EGFR: epidermal growth factor receptor; MMP2/9: matrix metalloproteinase-2/9; mTOR: mammalian target of rapamycin; NF-κB: nuclear factor kappa B; p-ERK1/2: phospho-extracellular signal-regulated kinase 1/2; PI3K: phosphoinositide 3-kinase; p-MEK: phospho-mitogen-activated protein kinase; STAT3: signal transducer and activator of transcription 3; VEGF: vascular endothelial growth factor; VEGFR2: vascular endothelial growth factor receptor 2.