title: Retinoids induce differentiation and downregulate telomerase activity and N-Myc to increase sensitivity to flavonoids for apoptosis in human malignant neuroblastoma SH-SY5Y cells.
abstract: Human malignant neuroblastoma is characterized by poor differentiation and uncontrolled proliferation of immature neuroblasts. Retinoids such as all-trans-retinoic acid (ATRA), 13-cis-retinoic acid (13-CRA), and N-(4-hydroxyphenyl) retinamide (4-HPR) at low doses are capable of inducing differentiation, while flavonoids such as (-)-epigallocatechin-3-gallate (EGCG) and genistein (GST) at relatively high dose can induce apoptosis. We used combination of retinoid and flavonoid for controlling growth of malignant neuroblastoma SH-SY5Y cells. Cells were treated with a retinoid (1 microM ATRA, 1 microM 13-CRA, or 0.5 microM 4-HPR) for 7 days and then with a flavonoid (25 microM EGCG or 25 microM GST) for 24 h. Treatment of cells with a low dose of a retinoid for 7 days induced neuronal differentiation with downregulation of telomerase activity and N-Myc but overexpression of neurofilament protein (NFP) and subsequent treatment with a relatively high dose of a flavonoid for 24 h increased apoptosis in the differentiated cells. Besides, retinoids reduced the levels of inflammatory and angiogenic factors. Apoptosis was associated with increases in intracellular free [Ca2+], Bax expression, cytochrome c release from mitochondria and activities of calpain and caspases. Decreases in expression of calpastatin (endogenous calpain inhibitor) and baculovirus inhibitor-of-apoptosis repeat containing (BIRC) proteins (endogenous caspase inhibitors) favored apoptosis. Treatment of SH-SY5Y cells with EGCG activated caspase-8, indicating induction of the receptor-mediated pathway of apoptosis. Based on our observation, we conclude that combination of a retinoid and a flavonoid worked synergistically for controlling the malignant growth of human neuroblastoma cells.
authors.affiliation: Department of Neurosciences, Medical University of South Carolina, Charleston, SC 29425, USA.
authors.forename: Arabinda
authors.initials: A
authors.lastname: Das
authors.forename: Naren L
authors.initials: NL
authors.lastname: Banik
authors.forename: Swapan K
authors.initials: SK
authors.lastname: Ray
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002154:Calpain / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000187:drug effects; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D005419:Flavonoids / Q000494:pharmacology*; D006801:Humans; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology; D009447:Neuroblastoma / Q000188:drug therapy* / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D016271:Proto-Oncogene Proteins c-myc / Q000096:biosynthesis*; D012176:Retinoids / Q000494:pharmacology*; D019098:Telomerase / Q000096:biosynthesis / Q000378:metabolism*
chemical_list: D005419:Flavonoids; D016271:Proto-Oncogene Proteins c-myc; D012176:Retinoids; D019098:Telomerase; D002154:Calpain; D053148:Caspase 3; D053181:Caspase 8; D002118:Calcium