3-6-dihydroxyflavone and Uterine-Cervical-Neoplasms

Previously we have shown that 3,6-dihydroxyflavone (3,6-DHF) is a potent agonist of the human peroxisome proliferator-activated receptor (hPPAR) with cytotoxic effects on human cervical cancer cells. To date, the mechanisms by which 3,6-DHF exerts its antitumor effects on cervical cells have not been clearly defined. Here, we demonstrated that 3,6-DHF exhibits a novel antitumor activity against HeLa cells with IC50 values of 25 μM and 9.8 μM after 24 h and 48 h, respectively. We also showed that the anticancer effects of 3,6-DHF are mediated via the toll-like receptor (TLR) 4/CD14, p38 mitogen-activated protein kinase (MAPK), Jun-N terminal kinase (JNK), extracellular-signaling regulated kinase (ERK), and cyclooxygenase (COX)-2 pathways in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. We found that 3,6-DHF showed a similar IC50 (113 nM) value to that of the JNK inhibitor, SP600125 (IC50 = 118 nM) in a JNK1 kinase assay. Binding studies revealed that 3,6-DHF had a strong binding affinity to JNK1 (1.996 × 105 M-1) and that the 6-OH and the carbonyl oxygen of the C ring of 3,6-DHF participated in hydrogen bonding interactions with the carbonyl oxygen and the amide proton of Met111, respectively. Therefore, 3,6-DHF may be a candidate inhibitor of JNKs, with potent anticancer effects.

Topics: Female; Flavonoids; Gene Expression Regulation, Neoplastic; Humans; Hydrogen Bonding; JNK Mitogen-Activated Protein Kinases; Neoplasm Proteins; Phosphorylation; Uterine Cervical Neoplasms

High-risk strains of human papillomaviruses (HPVs) cause nearly all cases of cervical cancer as well as a growing number of head and neck cancers. The oncogenicity of these viruses can be attributed to the activities of their two primary oncoproteins, E6 and E7. The E6 protein has among its functions the ability to prevent apoptosis of infected cells through its binding to FADD and caspase 8. A small molecule library was screened for candidates that could inhibit E6 binding to FADD and caspase 8. Flavonols were found to possess this activity with the rank order of myricetin>morin>quercetin>kaempferol=galangin≫(apigenin, 7-hydroxyflavonol, rhamnetin, isorhamnetin, geraldol, datiscetin, fisetin, 6-hydroxyflavonol). Counter screening, where the ability of these chosen flavonols to inhibit caspase 8 binding to itself was assessed, demonstrated that myricetin, morin and quercetin inhibited GST-E6 and His-caspase 8 binding in a specific manner. The structure-activity relationships suggested by these data are unique and do not match prior reports on flavonols in the literature for a variety of anticancer assays.

Topics: Apoptosis; Caspase 8; Caspase Inhibitors; Fas-Associated Death Domain Protein; Female; Flavones; Flavonols; Host-Pathogen Interactions; Human papillomavirus 16; Humans; Oncogene Proteins, Viral; Papillomavirus Infections; Repressor Proteins; Small Molecule Libraries; Uterine Cervical Neoplasms

We conducted in silico screening for human peroxisome proliferator-activated receptor gamma (hPPARgamma) by performing an automated docking study with 450 flavonoids. Among the eight flavonoids as possible agonists of hPPARgamma, only 3,6-dihydroxyflavone (4) increased the binding between PPARgamma and steroid receptor coactivator-1 (SRC-1), approximately 5-fold, and showed one order higher binding affinity for PPARgamma than a reference compound, indomethacin. The 6-hydroxy group of the A-ring of 3,6-dihydroxyflavone (4) participated in hydrogen-bonding interactions with the side chain of Tyr327, His449, and Tyr473. The B-ring formed a hydrophobic interaction with Leu330, Leu333, Val339, Ile341, and Met364. Therefore, 3,6-dihydroxyflavone is a potent agonist of hPPAR with cytotoxic effects on human cervical and prostate cancer cells.

Topics: Antineoplastic Agents; Drug Screening Assays, Antitumor; Female; Flavonoids; HeLa Cells; Humans; Male; Models, Molecular; PPAR gamma; Prostatic Neoplasms; Uterine Cervical Neoplasms