The Mechanisms Of PTTG Induced Glioma Angiogenesis Modulation

Glioma is the most malignant primary tumor of central nerve system. Despite greatadvance of tumor diagnosis and therapy have been brought out recent years, the prognosis ofglioma patients are still not optimism. Biotherapy of glioma has been researched extensivelylast decades, including immunotherapy and gene interference. New born micro-vessels areimportant component of tumor mesenchymal, which is crucial for tumor growth, as well astumor metastasis and invasion. Maniotis brought out a new definition of Vasculogenicmimicry to describe a kind of microtube which formed by high aggressive tumor cell in1999.VM could be detected in most malignances, which might be responsible for poor prognosis.VM is an important supplementary of tumor angiogenesis, which provide a new target foranti-angiogenesis treatment.Pituitary Tumor Transforming Gene (PTTG) was isolated from rat pituitary cell and wasproved to be one member of pituitary derivative transforming gene. PTTG belongs tooncogene family, and overexpression of PTTG could induce tumor formation, developmentand invasion. We would like to investigate PTTG expression and glioma grade, as well asMVD in this study. Then we used special siRNA to silence PTTG expression to study effectsof PTTG on glioma proliferation, invasion, metastasis and angiogenesis both in vitro and invivo. We also would like to explore the underlying mechanisms of the modulations.Objective： The aim of this study is to reveal the relationship between PTTG expressionand glioma angiogenesis. First, the correlations between PTTG expression and glioma gradewere studied, as well as PTTG expression and MVD. Then we used specific siRNA targetPTTG to silence PTTG expression in glioma cell lines U87, U251or SHG44, to research thechanges of glioma proliferation, metastasis, invasion and angiogenesis, and explored theunderlying mechanisms of the modulations.Methods: Glioma samples were obtained from72patients, and were divided into fourgroup according histological results, and the expression of PTTG was detected by immunohistochemistry. Then all samples were classified by PTTG expression, andendothelial cells were marked with CD31, the relationship between MVD and PTTGexpression was studied. Following siRNAs target PTTG were designed and connected toplasmid vector and tranfected into glioma cell lines U87, U251or SHG44, the proliferation,metastasis, invasion, vasculogenic mimicry and proteins which are response for the changeswere investigated. Then we established nude mice model with U251cells subcutaneousinjection. The growth of glioma tissue was examined, as well as MVD and vasculogenicmimicry. However, the proteins which are important for angiogenesis were also detected.Results: The positive cell rate of PTTG expression in normal brain tissue, WHO I-IVglioma tissue were20%,67%,80%,85%,100%respectively, and significance was detected(p<0.05); MVD in WHO I-IV glioma tissue were18.58±6.97,26.25±8.56,39.45±12.12,53.45±13.07respectively, and significance was detected (p<0.05); however, MVD in differentPTTG expression group were17.91±6.89,27.14±9.16,43.43±14.97,56.56±6.57respectively,and significance was detected (p<0.05); when siRNA target PTTG was applied, theexpression of PTTG was inhibited, and the proliferation, metastasis, invasion andvasculogenic mimicry of glioma cell lines were suppressed by the transduction in vitro; Inanimal models, glioma tissue growth and MVD down-regulated by the silencing; however, theapoptosis proteins such as p53were up-regulated after transfection, the proteins which induceanti-apoptosis and invasion/angiogenesis were down-regulated.Conclusions: PTTG expression was significantly up-regulated in glioma, and hadpositive correlation with glioma grade and MVD. Silencing of PTTG inhibited glioma cellproliferation, migration/invasion and angiogenesis, induced cell apoptosis, suppressed cellinvasion and arrested cell cycle at G0/G1stage. Also silencing of PTTG could inhibit tumorgrowth, invasion and angiogenesis in vivo. Our data indicated that PTTG could be regarded asa potential target for glioma treatment.