title: 5-Hydroxy-3,6,7,8,3',4'-hexamethoxyflavone induces apoptosis through reactive oxygen species production, growth arrest and DNA damage-inducible gene 153 expression, and caspase activation in human leukemia cells.
abstract: This study examined the growth inhibitory effects of structurally related polymethoxylated flavones in human cancer cells. Here, we report that 5-hydroxy-3,6,7,8,3',4'-hexamethoxyflavone (5-OH-HxMF) induces growth inhibition of human cancer cells and induction of apoptosis in HL-60 cells through modulation of mitochondrial functions regulated by reactive oxygen species (ROS). ROS generation occurs in the early stages of 5-OH-HxMF-induced apoptosis, preceding cytochrome c release, caspase activation, and DNA fragmentation. The changes occurred after single breaks in DNA were detected, suggesting that 5-OH-HxMF induced irreparable DNA damage, which in turn triggered the process of apoptosis. Up-regulation of Bax was found in 5-OH-HxMF-treated HL-60 cells. In addition, a caspase-independent pathway indicated by endonuclease G also contributed to apoptosis caused by 5-OH-HxMF. Antioxidants suppress 5-OH-HxMF-induced apoptosis. 5-OH-HxMF markedly enhanced growth arrest DNA damage-inducible gene 153 (GADD153) protein in a time-dependent manner. N-acetylcysteine (NAC) and catalase prevented up-regulation of GADD153 expression caused by 5-OH-HxMF. These findings suggest that 5-OH-HxMF creates an oxidative cellular environment that induces DNA damage and GADD153 gene activation, which in turn helps trigger apoptosis in HL-60 cells. Meanwhile, ROS were proven an important inducer in this apoptotic process. The C-5 hydroxyl on the ring of 5-OH-HxMF was found to be essential for the antiproliferative and apoptosis-inducing activity. Our study identified the novel mechanisms of 5-OH-HxMF-induced apoptosis and indicated that these results have significant applications as potential chemopreventive and chemotherapeutic agents.
authors.affiliation: Department of Seafood Science, National Kaohsiung Marine University, Kaohsiung 811, Taiwan. mhpan@mail.nkmu.edu.tw
authors.forename: Min-Hsiung
authors.initials: MH
authors.lastname: Pan
authors.forename: You-Syuan
authors.initials: YS
authors.lastname: Lai
authors.forename: Ching-Shu
authors.initials: CS
authors.lastname: Lai
authors.forename: Ying-Jan
authors.initials: YJ
authors.lastname: Wang
authors.forename: Shiming
authors.initials: S
authors.lastname: Li
authors.forename: Chih-Yu
authors.initials: CY
authors.lastname: Lo
authors.forename: Slavik
authors.initials: S
authors.lastname: Dushenkov
authors.forename: Chi-Tang
authors.initials: CT
authors.lastname: Ho
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects*; D004249:DNA Damage / Q000235:genetics*; D004789:Enzyme Activation / Q000187:drug effects; D047309:Flavones / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D018922:HL-60 Cells; D006801:Humans; D017382:Reactive Oxygen Species / Q000378:metabolism*; D051742:Transcription Factor CHOP / Q000235:genetics*
chemical_list: D000975:Antioxidants; D047309:Flavones; D017382:Reactive Oxygen Species; C521815:5-hydroxy-3,6,7,8,3',4'-hexamethoxyflavone; D051742:Transcription Factor CHOP; D020169:Caspases