Department of Neurosurgery, Navy General Hospital, 100048 Beijing, China.
J Exp Clin Cancer Res. 2012 May 31;31(1):52. doi: 10.1186/1756-9966-31-52.
In our previous study, we detected decreased expression of phospho-Smad1/5/8 and its upstream signaling molecule, bone morphogenetic protein receptor IB subunit (BMPR-IB), in certain glioblastoma tissues, unlike normal brain tissues. In order to clarify the functional roles and mechanism of BMPR-IB in the development of glioblastoma, we studied the effects of BMPR-IB overexpression on glioblastoma cell lines in vitro and in vivo.
We selected glioblastoma cell lines U251, U87, SF763, which have different expression of BMPR-IB to be the research subjects. Colony formation analysis and FACS were used to detect the effects of BMPR-IB on the growth and proliferation of glioblastoma cells in vivo. Immunofluresence was used to detect the differentiation changes after BMPR-IB overexpression or knocking-down. Then we used subcutaneous and intracranial tumor models to study the effect of BMPR-IB on the growth and differentiation of glioblastoma cells in vivo. The genetic alterations involved in this process were examined by real-time PCR and western blot analysis.ed.
Forced BMPR-IB expression in malignant human glioma cells, which exhibit lower expression of BMPR-IB, induced the phosphorylation and nuclear localization of smad1/5/8 and arrested the cell cycle in G1. Additionally, BMPR-IB overexpression could suppress anchorage-independent growth and promote differentiation of theses glioblastoma cells. Furthermore, overexpression of BMPR-IB inhibited the growth of subcutaneous and intracranial tumor xenografts and prolonged the survival of mice injected intracranially with BMPR-IB-overexpressing glioblastoma cells. Conversely, inhibition of BMPR-IB caused SF763 malignant glioma cells, a line known to exhibit high BMPR-IB expression that does not form tumors when used for xenografts, to show increased growth and regain tumorigenicity in a nude mouse model system, ultimately shortening the survival of these mice. We also observed significant accumulation of p21 and p27kip1 proteins in response to BMPR-IB overexpression. Our study suggests that overexpression of BMPR-IB may arrest and induce the differentiation of glioblastoma cells due to upregulation of p21 and p27kip1 in vitro and that in vivo and decreased expression of BMPR-IB in human glioblastoma cells contributes to glioma tumorigenicity. BMPR-IB could represent a new potential therapeutic target for malignant human gliomas.
在我们之前的研究中，我们发现某些脑肿瘤组织中磷酸化 Smad1/5/8 及其上游信号分子骨形态发生蛋白受体 IB 亚基（BMPR-IB）的表达降低，而正常脑组织中则没有。为了阐明 BMPR-IB 在脑肿瘤发生发展中的功能作用和机制，我们研究了 BMPR-IB 过表达对体外和体内脑胶质瘤细胞系的影响。
我们选择了具有不同 BMPR-IB 表达水平的脑胶质瘤细胞系 U251、U87、SF763 作为研究对象。利用集落形成分析和 FACS 检测 BMPR-IB 过表达对体内脑胶质瘤细胞生长和增殖的影响。免疫荧光检测 BMPR-IB 过表达或敲低后分化的变化。然后，我们利用皮下和颅内肿瘤模型研究 BMPR-IB 过表达对体内脑胶质瘤细胞生长和分化的影响。通过实时 PCR 和 Western blot 分析检测该过程中涉及的遗传改变。
在恶性人胶质瘤细胞中强制表达 BMPR-IB，这些细胞的 BMPR-IB 表达较低，可诱导 smad1/5/8 的磷酸化和核定位，并使细胞周期停滞在 G1 期。此外，BMPR-IB 过表达可抑制这些脑胶质瘤细胞的锚定非依赖性生长并促进其分化。此外，BMPR-IB 过表达抑制皮下和颅内肿瘤异种移植物的生长，并延长颅内注射 BMPR-IB 过表达脑胶质瘤细胞的小鼠的存活时间。相反，抑制 BMPR-IB 导致 SF763 恶性神经胶质瘤细胞，该细胞系已知表达高水平的 BMPR-IB，当用于异种移植时不会形成肿瘤，在裸鼠模型系统中表现出生长增加并恢复致瘤性，最终缩短了这些小鼠的存活时间。我们还观察到，BMPR-IB 过表达可导致 p21 和 p27kip1 蛋白的显著积累。我们的研究表明，BMPR-IB 过表达可能通过上调体外 p21 和 p27kip1 导致脑胶质瘤细胞停滞和分化，并且在体内，BMPR-IB 在人脑胶质瘤细胞中的表达降低有助于胶质瘤的发生。BMPR-IB 可能成为恶性人类神经胶质瘤的一个新的潜在治疗靶点。
