Transcriptional repression of Mad-Max complex by human umbilical cord blood stem cells downregulates extracellular signal-regulated kinase in glioblastoma.
Transcriptional repression of Mad-Max complex by human umbilical cord blood stem cells downregulates extracellular signal-regulated kinase in glioblastoma.
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DOI：
10.1089/scd.2011.0424
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发表时间：
2012-07
影响因子：
4
通讯作者：
K. Velpula;V. R. Dasari;A. Tsung;D. Dinh;J. S. Rao
中科院分区：
文献类型：
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作者：
K. Velpula;V. R. Dasari;A. Tsung;D. Dinh;J. S. Rao
以前，我们已经表明，人脐带血干细胞（hUCBSC）治疗下调神经胶质瘤细胞中的细胞周期蛋白D1。为了研究细胞周期进程并研究调控细胞周期蛋白D1表达的上游分子，我们分析了细胞外信号调节激酶（ERK）的参与及其在hUCBSC处理后的功能。我们观察到hUCBSC处理后pERK在转录和翻译水平的下调。在胶质瘤细胞中观察到ERK从细胞质向细胞核的易位增加，而与胶质瘤细胞共培养的hUCBSC显示出抑制的核易位。这一发现表明hUCBSC通过抑制磷酸化Thr（202）/Tyr（204）的磷酸化来调节ERK，从而阻滞pERK核转位。ERK启动子分析显示c-Myc结合位点，表明可能的转录相互作用，调节细胞周期蛋白D1和ERK表达水平。用MEK/ERK抑制剂U 0126处理U251和5310胶质瘤细胞，pERK和c-Myc水平下降。在另一个实验中，用10074-G5，c-Myc/Max抑制剂处理的U251和5310细胞显示pERK和c-Myc水平降低，提示ERK/c-Myc/Max分子之间的正反馈环。在本研究中，我们发现，胶质瘤细胞表现出丰富的c-Myc表达和增加c-Myc/Max活性。与此相反，与hUCBSC共培养的胶质瘤细胞表现出高Mad 1表达，其竞争性结合Max以抑制c-Myc/Max介导的基因转录。因此，我们的研究阐明了hUCBSC通过限制Max与c-Myc的结合来控制胶质瘤细胞周期进展和侵袭的潜在作用，从而通过增加Mad 1表达水平来调节胶质瘤细胞周期和侵袭相关分子如ERK、整合素的表达。
Previously, we have shown that human umbilical cord blood stem cell (hUCBSC) treatment downregulate cyclin D1 in glioma cells. To study the cell cycle progression and investigate the upstream molecules regulating cyclin D1 expression, we analyzed the involvement of extracellular signal-regulated kinase (ERK) and its functionality after treatment with hUCBSC. We observed downregulation of pERK after hUCBSC treatment at both transcriptional and translational levels. Increased translocation of ERK from cytoplasm to the nucleus was observed in glioma cells, whereas hUCBSC cocultures with glioma cells showed suppressed nuclear translocation. This finding suggests that hUCBSC regulates ERK by suppressing its phosphorylation at phospho-Thr(202)/Tyr(204) retarding pERK nuclear translocation. ERK promoter analysis has shown c-Myc binding sites, indicative of possible transcriptional interactions that regulate cyclin D1 and ERK expression levels. Treatment of U251 and 5310 glioma cells with U0126, a MEK/ERK inhibitor receded pERK and c-Myc levels. In another experiment, U251 and 5310 cells treated with 10074-G5, c-Myc/Max inhibitor displayed reduction in pERK and c-Myc levels suggestive of a positive feedback loop between ERK/c-Myc/Max molecules. In the present study, we show that glioma cells exhibit abundant c-Myc expression and increased c-Myc/Max activity. In contrast, the glioma cells cocultured with hUCBSC demonstrated high Mad1 expression that competitively binds to Max to repress the c-Myc/Max mediated gene transcription. Our studies thus elucidate the potential role of hUCBSC in controlling glioma cell cycle progression and invasion by limiting Max binding to c-Myc, thus regulating the expression of glioma cell cycle and invasion associated molecules such as ERK, integrins via increased levels of Mad1 expression.