epidermal-growth-factor and kaempferol

Topics: Antineoplastic Agents, Phytogenic; bcl-X Protein; Cell Survival; Computer Simulation; Coumarins; Epidermal Growth Factor; ErbB Receptors; HCT116 Cells; HeLa Cells; Hep G2 Cells; Humans; In Vitro Techniques; Inhibitory Concentration 50; Kaempferols; Molecular Docking Simulation; Myeloid Cell Leukemia Sequence 1 Protein; Phytochemicals; Plant Extracts; Zygophyllaceae

JAK1/STAT3 pathway has been suggested to play a role in cell transformation and carcinogenesis. In the present study, we found that myricetin (3, 3', 4', 5, 5', 7-hexahydroxyflavone), a typical flavonol existing in many fruits and vegetables, could directly bind to JAK1/STAT3 molecules to inhibit cell transformation in epidermal growth factor (EGF)-activated mouse JB6 P(+) cells. Colony assay revealed that myricetin had the strongest inhibitory effect on cell transformation among three flavonols including myricetin, quercetin and kaempferol. Molecular data revealed that myricetin inhibited DNA- binding and transcriptional activity of STAT3. Furthermore, myricetin inhibited the phosphorylation of STAT3 at Tyr705 and Ser727. Cellular signaling analyses revealed that EGF could induce the phosphorylation of Janus Kinase (JAK) 1, but not JAK2. Myricetin inhibited the phosphorylation of JAK1 and increased the autophosphorylation of EGF receptor (EGFR). Moreover, ex vivo and in vitro pull-down assay revealed that myricetin bound to JAK1 and STAT3, but not EGFR. Affinity data further demonstrated that myricetin had a higher affinity for JAK1 than STAT3. Thus, our data indicate that myricetin might directly target JAK1 to block cell transformation in mouse JB6 cells.

Topics: Animals; Antioxidants; Cell Line; Cell Transformation, Neoplastic; DNA; Epidermal Growth Factor; Flavonoids; Janus Kinase 1; Kaempferols; Mice; Phosphorylation; Protein Binding; Quercetin; STAT3 Transcription Factor; Transcription, Genetic

Our previous findings indicated that RSK2 plays a critical role in proliferation and cell transformation induced by tumor promoters, such as epidermal growth factor or 12-O-tetradecanoylphorbol-13-acetate, and that kaempferol, a natural compound found in edible plants, selectively inhibits RSK2 activity. However, the molecular mechanism for RSK2 activation is unclear. Herein, we provide evidence showing that NH(2)-terminal kinase domain (NTD) activation of RSK2 is required for the activation of the extracellular signal-regulated kinase-mediated COOH-terminal kinase domain (CTD). We also found that the NTD plays a key role in substrate phosphorylation and that kaempferol binds with the NTD but not the CTD in both the active and inactive forms. Homology modeling of the RSK2 NH(2)-terminal domain and small-molecule docking, validated by mutagenesis experiments, clearly showed that Val(82) and Lys(100) are critical amino acids for kaempferol binding and RSK2 activity. Furthermore, immunohistofluorescence and Western blot results indicated that the RSK2 protein level is markedly higher in cancer cell lines as well as cancer tissues compared with nonmalignant cell lines or normal tissues. In addition, kaempferol inhibited proliferation of malignant human cancer cell lines, including A431, SK-MEL-5 and SK-MEL-28, and HCT-116. These results indicate that targeting RSK2 with natural compounds, such as kaempferol, might be a good strategy for chemopreventive or chemotherapeutic application.

Topics: Binding Sites; Cell Division; Cell Line, Tumor; Cell Transformation, Neoplastic; Epidermal Growth Factor; Humans; Kaempferols; Kinetics; Lysine; Neoplasms; Phosphorylation; Protein Kinases; Recombinant Proteins; Reference Values; Ribosomal Protein S6 Kinases, 90-kDa; Skin; Tetradecanoylphorbol Acetate; Tissue Array Analysis; Valine

Many plant-derived substances have estrogenic activities. Due to their ability to bind the estrogen receptor (ER), these compounds have the potential to counteract the deleterious effects of estrogen deficiency on bone. In this study, we investigated the in vitro effect of two widespread flavonols, quercetin and kaempferol, on alkaline phosphatase (ALP) activity in MG-63 cultured human osteoblasts. We found that both flavonols significantly increased ALP activity. This effect was markedly reduced by PD 98059, an inhibitor of the extracellular regulated kinase (ERK) pathway, and by ICI 182780, an antagonist of ERs. Western blot studies confirmed that ERK is rapidly activated in cells treated by both flavonols. Finally, ICI 182780 markedly inhibits the flavonol-induced ERK activation. The data presented in this study support the conclusion that, in MG-63 osteoblasts (i) the increase in ALP activity by flavonols involves a rapid stimulation of ERK activation but also involves the ER, and that (ii) the activation of ERK by flavonols occurs most likely downstream of the ERs activation. Taken together, these results suggest that flavonols derivatives as quercetin and kaempferol can stimulate osteoblastic activity. Such compounds may represent new pharmacological tools for the treatment of osteoporosis.

Topics: Alkaline Phosphatase; Cells, Cultured; Enzyme Activation; Epidermal Growth Factor; Estradiol; Flavonoids; Humans; Kaempferols; MAP Kinase Signaling System; Mitogen-Activated Protein Kinases; Osteoblasts; Quercetin; Receptors, Estrogen; Signal Transduction