Effect of osthole on proliferation and radiosensitivity of poorly differentiated CNE2 stem cells from nasopharyngeal carcinoma / 中草药

ABSTRACT

Objective To investigate the effect and the underlying mechanism of osthole on the proliferation and radiosensitivity of CNE2 stem cells, one of the poorly differentiated cell lines from nasopharyngeal carcinoma. Methods Poorly differentiated CNE2 stem cells were isolated and cultured in serum-free medium (SFM). Flow cytometry was used to detect biomarkers (CD44+/CD24-low) of stem cells and the activity of ALDH. CNE2 stem cells was treated with different concentrations of osthole (0, 20, 40, 80 μg/mL), and then subject to MTT assay. Additionally, CNE2 stem cell was treated with 40 μg/mL osthole plus different dose of radiation (0, 2, 5 Gy) followed by colony formation assay. Consequently, Western blotting was used to detect the difference of pGSK-3β, β-catenin, and Cyclin D1 protein expression in CNE2 stem cells after the treatment of osthole with or without radiation. Results Poorly differentiated CNE2 stem cells isolated and cultured in serum-free medium (SFM) could be passaged stably. The ratio of CD44+/CD24-low and the activity of ALDH were significantly higher in CNE2 stem cells than that in the parental cells (P < 0.05). Compared to the control group, osthole could obviously suppress the proliferation of CNE2 stem cells in a dose and time dependent manner (P < 0.05). Moreover, colony formation assay revealed that inhibition rate of CNE2 stem cell colony formation was highest after the treatment of osthole plus radiation, followed by the treatment of osthole or radiation alone (P < 0.05). Western blotting indicated that in contrast to the controls, the expression of pGSK-3β, β-catenin, and Cyclin D1 protein was mostly down-regulated in the CNE2 stem cells treated with osthole plus radiation, followed by that treated with osthole or radiation alone (P < 0.05). Conclusion Osthole effectively inhibited the proliferation and increased the radiosensitivity of CNE2 stem cells, probably due to the down-regulation of pGSK-3, β-catenin, and Cyclin D1 in tumor stem cells by osthole.