Raf and MEK Protein Kinases Are Direct Molecular Targets for the Chemopreventive Effect of Quercetin, a Major Flavonol in Red Wine

Abstract

Considerable attention has focused on the health-promoting effects of red wine and its nonflavonoid polyphenol compound resveratrol. However, the underlying molecular mechanisms and molecular target(s) of red wine or other potentially active ingredients in red wine remain unknown. Here, we report that red wine extract (RWE) or the red wine flavonoid quercetin inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced transformation of JB6 promotion-sensitive mouse skin epidermal (JB6 P+) cells. The activation of activator protein-1 and nuclear factor-KB induced by TPA was dose dependently inhibited by RWE or quercetin treatment. Western blot and kinase assay data revealed that RWE or quercetin inhibited mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase (MEK) 1 and Raf1 kinase activities and subsequently attenuated TPAinduced phosphorylation of ERK/p90 ribosomal S6 kinase. Although either RWE or quercetin suppressed Raf1 kinase activity, they were more effective in inhibiting MEK1 activity. Importantly, quercetin exerted stronger inhibitory effects than PD098059, a well-known pharmacologic inhibitor of MEK. Resveratrol did not affect either MEK1 or Raf1 kinase activity. Pull-down assays revealed that RWE or quercetin (but not resveratrol) bound with either MEK1 or Raf1. RWE or quercetin also dose dependently suppressed JB6 P+ cell transformation induced by epidermal growth factor or H-Ras, both of which are involved in the activation of MEK/ ERK signaling. Docking data suggested that quercetin, but not resveratrol, formed a hydrogen bond with the backbone amide group of Ser 212 , which is the key interaction for stabilizing the inactive conformation of the activation loop of MEK1. [Cancer Res 2008;68(3):946-55]

Piceatannol, Natural Polyphenolic Stilbene, Inhibits Adipogenesis via Modulation of Mitotic Clonal Expansion and Insulin Receptor-dependent Insulin Signaling in Early Phase of Differentiation

“…The mixture was washed three times with 0.1 M acetated (pH 4.0) buffer and 0.1 M Tris buffer (pH 8.0), respectively, and suspended in PBS. In vitro pulldown assay was performed as described previously (27). Briefly, Histagged active IR protein (0.2 g) was incubated with piceatannol-Sepharose 4B or control Sepharose 4B beads.…”

Natural Polyphenols that Display Anticancer Properties through Inhibition of Kinase Activity

“…Luteolin (20) and apigenin (21) were able to inhibit PKC and PI3K/Akt in various prostate cancer cell lines [47,48]. Quercetin (22) was reported to inhibit MEK1, Raf1 and PKC and, thus, inhibit neoplastic cell transformation (Table 3) [48,60]. Myricetin (23) was also capable of inhibiting MEK1 but the inhibition was more potent with the MAP kinase 4 (MKK4) ( Table 3) [49].…”

“…Quercetin (22) was docked to a separate site, adjacent to the ATP-binding site of mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK1) [60]. This binding event results in stabilization of the inactive conformation of the activation loop of MEK1 [60].…”

Update on Cancer Prevention Research in the United States and China: The 2009 China—U.S. Forum on Frontiers of Cancer Research

“…Research directed toward elucidating underlying molecular mechanisms of chemoprevention or chemoprotection with edible phytochemicals present in fruits, vegetables, spices, and herbs has recognized distinct redox-sensitive transcription factors and their upstream regulators as potential targets (35). Research findings from The Hormel Institute have shown that blocking certain cellular signals with natural small molecule inhibitors can decrease UV-induced skin carcinogenesis and other cancers (32,33,(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46).…”