A chrysin derivative suppresses skin cancer growth by inhibiting cyclin-dependent kinases.

Abstract

Chrysin (5,7-dihydroxyflavone), a natural flavonoid widely distributed in plants, reportedly has chemopreventive properties against various cancers. However, the anticancer activity of chrysin observed in in vivo studies has been disappointing. Here, we report that a chrysin derivative, referred to as compound 69407, more strongly inhibited EGF-induced neoplastic transformation of JB6 P(+) cells compared with chrysin. It attenuated cell cycle progression of EGF-stimulated cells at the G1 phase and inhibited the G1/S transition. It caused loss of retinoblastoma phosphorylation at both Ser-795 and Ser-807/811, the preferred sites phosphorylated by Cdk4/6 and Cdk2, respectively. It also suppressed anchorage-dependent and -independent growth of A431 human epidermoid carcinoma cells. Compound 69407 reduced tumor growth in the A431 mouse xenograft model and retinoblastoma phosphorylation at Ser-795 and Ser-807/811. Immunoprecipitation kinase assay results showed that compound 69407 attenuated endogenous Cdk4 and Cdk2 kinase activities in EGF-stimulated JB6 P(+) cells. Pulldown and in vitro kinase assay results indicated that compound 69407 directly binds with Cdk2 and Cdk4 in an ATP-independent manner and inhibited their kinase activities. A binding model between compound 69407 and a crystal structure of Cdk2 predicted that compound 69407 was located inside the Cdk2 allosteric binding site. The binding was further verified by a point mutation binding assay. Overall results indicated that compound 69407 is an ATP-noncompetitive cyclin-dependent kinase inhibitor with anti-tumor effects, which acts by binding inside the Cdk2 allosteric pocket. This study provides new insights for creating a general pharmacophore model to design and develop novel ATP-noncompetitive agents with chemopreventive or chemotherapeutic potency.

• Authors: Haidan Liu, Kangdong Liu, Zunnan Huang, Chan-Mi Park, N R Thimmegowda, Jae-Hyuk Jang, In-Ja Ryoo, Long He, Sun-Ok Kim, Naomi Oi, Ki Won Lee, Nak-Kyun Soung, Ann M Bode, Yifeng Yang, Xinmin Zhou, Raymond L Erikson, Jong-Seog Ahn, Joonsung Hwang, Kyoon Eon Kim, Zigang Dong, Bo-Yeon Kim
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 288 Issue 36 Pg. 25924-25937 (Sep 06 2013) ISSN: 1083-351X [Electronic] United States
• PMID: 23888052 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Flavonoids
• Protein Kinase Inhibitors
• Retinoblastoma Protein
• chrysin
• Epidermal Growth Factor
• Cyclin-Dependent Kinases

Topics

• Allosteric Regulation (drug effects)
• Animals
• Binding Sites
• Carcinoma, Squamous Cell (drug therapy, enzymology, genetics, pathology)
• Cell Line, Tumor
• Crystallography, X-Ray
• Cyclin-Dependent Kinases (antagonists & inhibitors, genetics, metabolism)
• Epidermal Growth Factor (genetics, metabolism)
• Flavonoids (chemistry, pharmacology)
• G1 Phase (drug effects, genetics)
• Humans
• Mice
• Mice, Inbred BALB C
• Mice, Nude
• Models, Molecular
• Neoplasm Transplantation
• Protein Kinase Inhibitors (chemistry, pharmacology)
• Retinoblastoma Protein (genetics, metabolism)
• S Phase (drug effects, genetics)
• Skin Neoplasms (drug therapy, enzymology, genetics, pathology)