Celecoxib suppresses the phosphorylation of STAT3 protein and can enhance the radiosensitivity of medulloblastoma-derived cancer stem-like cells.

Meng-Yin Yang,Chiung-Chyi Shen,Hsin-I Ma,Hsu-Tung Lee,Chien-Min Chen

doi:10.3390/ijms150611013

Abstract

Medulloblastoma (MB) is a malignant primary brain tumor with poor prognosis. MB-derived CD133/Nestin double-positive cells (MB-DPs) exhibit cancer stem-like cell (CSC)-like properties that may contribute to chemoradioresistance, tumorigenesis and recurrence. In various tumors, signal transducer and activator of transcription 3 (STAT3) upregulation including MB which can regulate the expression of Nestin. Celecoxib, a selective COX-2 inhibitor, has been shown to potentially reduce STAT3 phosphorylation. The aim of the present study was to investigate the role of celecoxib in enhancing the effects of ionizing radiotherapy (IR) on MB-DP. MB-DPs and MB-derived CD133/Nestin double-negative cells (MB-DNs) were isolated from medulloblastoma cell line Daoy. Then, both of them were treated with celecoxib in different concentrations, and cell viability was assessed. The assays of cell survival, sphere formation, radiosensitivity, colony formation, apoptotic activity and mouse xenografting experiments in MB-DPs and MB-DNs treated with celecoxib alone, radiation alone, or celecoxib combined with radiation were further evaluated. We isolated MB-DPs from MB cell line Daoy, which exhibited typical CSC-like characteristics. Microarray analysis and Western blotting both indicated the upregulation of Janus kinase (JAK)-STAT cascade and STAT3 phosphorylation. Incubation with celecoxib dose-dependently suppressed the CSC-like properties and enhanced the IR effect on the induction of apoptosis, as detected by TUNEL assay and staining for Caspase 3 and Annexin V. Finally, celecoxib also enhanced the IR effect to suppress tumorigenesis and synergistically improve the recipient survival in orthotopic MB-derived CD133/Nestin double-positive cells (MB-DP cells) bearing mice.

Highlights

Medulloblastoma (MB), a highly malignant primary brain tumor, comprises 13%–20% of all childhood brain tumors which is the most common pediatric brain tumor [1]
Previous evidences have demonstrated that cancer stem cells can be cultured and enriched without affecting their self-renewal capabilities in serum-free media with basic fibroblast growth factor and epidermal growth factor (EGF) [33,34,35]
We cultured and maintained these parental cells (Figure 1A, upper, representative morphology indicates Daoy) in serum-free media supplemented with basic fibroblast growth factor (bFGF) and EGF for 1 month, and these cancer cells stably proliferated and formed floating spheroid-like bodies (SBs) (Figure 1A, lower, representative morphology indicates Daoy)

Summary

Introduction

Medulloblastoma (MB), a highly malignant primary brain tumor, comprises 13%–20% of all childhood brain tumors which is the most common pediatric brain tumor [1]. Researchers have described that MB invades the embryonic posterior fossa of the cerebellum and this is believed to arise from the precursor cells of the external granule layer or neuroepithelial cells from the cerebellar ventricular zone of the developing cerebellum. Recent studies described that MBs can divide as different diseases originating from different locations within the cerebellum depending on molecular subgroup [2,3,4,5,6]. If patients do not receive active treatment, these patients are inclined to have recurrence and die within 3 years [7,8]. Since surgical excision alone is usually ineffective and may provide a poor overall survival for infants and young children, the standard treatment for of MB consists of aggressive surgery, craniospinal radiotherapy and chemotherapy [9]. The precise mechanisms underlying the pathogenesis of MB are still unclear, and the development of effective therapeutic strategies for MB is undoubtedly urgent

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