Rhamnetin and Cirsiliol Induce Radiosensitization and Inhibition of Epithelial-Mesenchymal Transition (EMT) by miR-34a-mediated Suppression of Notch-1 Expression in Non-small Cell Lung Cancer Cell Lines

• Published in: The Journal of biological chemistry Vol. 288; no. 38; pp. 27343 - 27357
• Main Authors: Kang, JiHoon, Kim, EunGi, Kim, Wanyeon, Seong, Ki Moon, Youn, HyeSook, Kim, Jung Woo, Kim, Joon, Youn, BuHyun
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 20.09.2013; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; Cancer Therapy; Carcinoma, Non-Small-Cell Lung - metabolism; Carcinoma, Non-Small-Cell Lung - pathology; Carcinoma, Non-Small-Cell Lung - therapy; Cell Line, Tumor; Cell Proliferation - drug effects; Cell Proliferation - radiation effects; Cirsiliol; EMT; Epithelial-Mesenchymal Transition - drug effects; Epithelial-Mesenchymal Transition - radiation effects; Flavones - pharmacology; Gamma Rays; Gene Expression Regulation, Neoplastic - drug effects; Gene Expression Regulation, Neoplastic - radiation effects; Humans; Lung Cancer; Lung Neoplasms - metabolism; Lung Neoplasms - pathology; Lung Neoplasms - therapy; Male; Mice; Mice, Inbred BALB C; Mice, Nude; MicroRNAs - biosynthesis; miR-34a; Natural Products; NF-kappa B - metabolism; Notch-1; Quercetin - analogs & derivatives; Quercetin - pharmacology; Radiation Biology; Radiation Tolerance - drug effects; Radiation Tolerance - radiation effects; Radiosensitization; Receptor, Notch1 - biosynthesis; Rhamnetin; RNA, Neoplasm - biosynthesis; Signal Transduction; Tumor Suppressor Protein p53 - metabolism; Rhamnetin; Cancer Therapy; Natural Products; Lung Cancer; Radiosensitization; miR-34a; Radiation Biology; EMT; Notch-1; Cirsiliol
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M113.490482

Radioresistance is a major cause of decreasing the efficiency of radiotherapy for non-small cell lung cancer (NSCLC). To understand the radioresistance mechanisms in NSCLC, we focused on the radiation-induced Notch-1 signaling pathway involved in critical cell fate decisions by modulating cell proliferation. In this study, we investigated the use of Notch-1-regulating flavonoid compounds as novel therapeutic drugs to regulate radiosensitivity in NSCLC cells, NCI-H1299 and NCI-H460, with different levels of radioresistance. Rhamnetin and cirsiliol were selected as candidate Notch-1-regulating radiosensitizers based on the results of assay screening for activity and pharmacological properties. Treatment with rhamnetin or cirsiliol reduced the proliferation of NSCLC cells through the suppression of radiation-induced Notch-1 expression. Indeed, rhamnetin and cirsiliol increased the expression of tumor-suppressive microRNA, miR-34a, in a p53-dependent manner, leading to inhibition of Notch-1 expression. Consequently, reduced Notch-1 expression promoted apoptosis through significant down-regulation of the nuclear factor-κB pathway, resulting in a radiosensitizing effect on NSCLC cells. Irradiation-induced epithelial-mesenchymal transition was also notably attenuated in the presence of rhamnetin and cirsiliol. Moreover, an in vivo xenograft mouse model confirmed the radiosensitizing and epithelial-mesenchymal transition inhibition effects of rhamnetin and cirsiliol we observed in vitro. In these mice, tumor volume was significantly reduced by combinational treatment with irradiation and rhamnetin or cirsiliol compared with irradiation alone. Taken together, our findings provided evidence that rhamnetin and cirsiliol can act as promising radiosensitizers that enhance the radiotherapeutic efficacy by inhibiting radiation-induced Notch-1 signaling associated with radioresistance possibly via miR-34a-mediated pathways. Background: Notch-1 plays a critical role in cell fate decisions by modulating cellular processes under irradiation. Results: Irradiation-induced Notch-1 overexpression promoted survival and EMT in NSCLC, whereas rhamnetin and cirsiliol inhibited these effects via miR-34a-mediated Notch-1 down-regulation. Conclusion: Rhamnetin and cirsiliol suppress Notch-1-mediated radioresistance and EMT phenotypes in NSCLC. Significance: Rhamnetin and cirsiliol can act as novel radiosensitizers by inhibiting radiation-induced Notch-1 signaling.