chrysin and Carcinoma--Squamous-Cell

The aberrant expression of claudins (CLDNs), which are tight junctional proteins, is seen in various solid tumors, but the regulatory mechanisms and their pathophysiological role are not well understood. Both CLDN1 and CLDN11 were highly expressed in human lung squamous cell carcinoma (SCC). Chrysin, found in high concentration in honey and propolis, decreased CLDN1 and CLDN11 expression in RERF-LC-AI cells derived from human lung SCC. The phosphorylation level of Akt was decreased by chrysin, but those of ERK1/2 and c-Jun were not. LY-294002, an inhibitor of phosphatidylinositol 3-kinase, inhibited the phosphorylation of Akt and decreased the expression levels of CLDN1 and CLDN11. The association between phosphoinositide-dependent kinase 1 (PDK1) and Akt was inhibited by chrysin, but the phosphorylation of PDK1 was not. Immunoprecipitation and quartz-crystal microbalance assays revealed that biotinylated-chrysin binds directly to Akt. The knockdown of CLDN1 and CLDN11 using small interfering RNAs increased the transepithelial flux of doxorubicin (DXR), an anthracycline anticancer drug. Similarly, both chrysin and LY-294002 increased DXR flux. Neither CLDN1 knockdown, CLDN11 knockdown, nor chrysin changed the anticancer drug-induced cytotoxicity in a two-dimensional culture model, whereas they enhanced cytotoxicity in a spheroid culture model. Taken together, chrysin may bind to Akt and inhibit its phosphorylation, resulting in the elevation of anticancer drug-induced toxicity mediated by reductions in CLDN1 and CLDN11 expression in RERF-LC-AI cells. We suggest that chrysin may be useful as an adjuvant chemotherapy in lung SCC.

Topics: Adenocarcinoma of Lung; Antineoplastic Agents; Carcinoma, Squamous Cell; Cell Line, Tumor; Claudin-1; Claudins; Doxorubicin; Flavonoids; Gene Expression Regulation, Neoplastic; Humans; Lung Neoplasms; Phosphorylation

To investigate the effect of chrysin on apoptosis of oral squamous carcinoma KB cell line and the possible mechanisms, and to provide new ideas for the treatment of oral cancer.
 Methods: Oral cancer KB cells were treated with different concentrations of chrysin (1, 2, 4, 8, 16, and 32 μmol/L) for 24 h. Cell proliferation was detected by MMT assay; apoptosis was detected by flow cytometry; the activity of caspase-3/7 was detected by chemiluminescent assay; mitochondrial membrane potential in KB cells was determined by JC-1 assay; and Western blotting was used to determine the activation of protein kinase B (AKT) and phosphoinositide-3-kinase (PI3K).
 Results: Chrysin inhibited the proliferation of KB cells in a concentration-dependent manner, accompanied by increase in apoptosis of KB cells, activation of caspase-3/7, decrease in mitochondrial membrane potential, and suppression of the phosphorylation of AKT and PI3K.
 Conclusion: The effect of chrysin on KB cell apoptosis may be related to mitochondrial dysfunction and inhibition of PI3K/AKT pathway.. 目的：探讨白杨素对口腔鳞状细胞癌KB细胞凋亡的影响及其机制，为临床上口腔鳞状细胞癌的治疗提供思路。方法：用不同浓度白杨素(1，2，4，8，16和32 μmol/L)处理KB细胞24 h，采用MMT法检测细胞增殖，流式细胞术检测细胞凋亡，化学发光法检测caspase-3/7活性，JC-1法检测KB细胞线粒体膜电位的变化，蛋白质印迹检测蛋白激酶B(protein kinase B，AKT)和磷脂酰肌醇3-激酶(phosphoinositide-3-kinase，PI3K)的活化。结果：白杨素以浓度依赖方式抑制KB细胞增殖并诱导其凋亡，促进caspase-3/7的活化，降低KB细胞线粒体膜电位；同时抑制AKT和PI3K磷酸化。结论：白杨素诱导KB细胞凋亡作用可能与线粒体功能障碍和抑制PI3K/AKT通路相关。.

Topics: Apoptosis; Carcinoma, Squamous Cell; Flavonoids; Humans; KB Cells; Mouth Neoplasms; Phosphatidylinositol 3-Kinases; Signal Transduction

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.

Topics: Allosteric Regulation; Animals; Binding Sites; Carcinoma, Squamous Cell; Cell Line, Tumor; Crystallography, X-Ray; Cyclin-Dependent Kinases; Epidermal Growth Factor; Flavonoids; G1 Phase; Humans; Mice; Mice, Inbred BALB C; Mice, Nude; Models, Molecular; Neoplasm Transplantation; Protein Kinase Inhibitors; Retinoblastoma Protein; S Phase; Skin Neoplasms