Proposed regulatory mechanism of clock genes in cancer. AC, adenyl cyclase; ACER2, alkaline ceramidase 2; ATG5, autophagy regulate gene 5; BC, breast cancer; CDK5, cyclin-dependent kinase 2; CSC, cancer stem cell; CRC, colorectal cancer; DOX, doxorubicin; EMT, epithelial–mesenchymal transition; GC, gastric cancer; G6PD, glucose-6-phosphate dehydrogenase; IL8, interleukin 8; ISO, isoproterenol; MDM2, mouse double minute 2; MMP2, matrix metalloproteinase-2; MMP9, matrix metalloproteinase-9; NPC, nasopharyngeal carcinoma; NSCLC, nonsmall cell lung cancer; MRP2, ATP binding cassette subfamily C member 2; OV, ovarian cancer; OSCC, oral squamous cell carcinoma; PFKFB3, 6-phosphofructokinase-2/fructose-2,6-bisphosphatase; P-gp, P-glycoprotein; PPP, pentose phosphate pathway; SP1, specific protein 1; S1P, sphingosine 1-phosphate; TNBC, triple-negative breast cancer; TNFα, tumor necrosis factorα; u-PA, urokinase-type plasminogen activator; VEGF, vascular endothelial growth factor.