ABSTRACT
<p><b>BACKGROUND</b>Angiogenesis is a prerequisite for tumor growth and plays an important role in rapidly growing tumors, such as malignant gliomas. A variety of factors controlling the angiogenic balance have been described, and among these, the endogenous inhibitor of angiogenesis, tumstatin, has drawn considerable attention. The current study investigated whether expression of tumstatin by glioma cells could alter this balance and prevent tumor formation.</p><p><b>METHODS</b>We engineered stable transfectants from human glioma cell line U251 to constitutively secrete a human tumstatin protein with c-myc and polyhistidine tags. Production and secretion of the tumstatin-c-myc-His fusion protein by tumstatin-transfected cells were confirmed by Western blotting analysis. In the present study, we identify the anti-angiogenic capacity of tumstatin using several in vitro and in vivo assays. Student's t-test and one-way analysis of variance (ANOVA) test were used to determine the statistical significance in this study.</p><p><b>RESULTS</b>The tumstatin transfectants and control transfectants (stably transfected with a control plasmid) had similar in vitro growth rates compared to their parental cell lines. However, the conditioned medium from the tumstatin transfected tumor cells significantly inhibits proliferation and causes apoptosis of endothelial cells. It also inhibits tube formation of endothelial cells on Matrigel. Examination of armpit tumors arising from cells overexpressing tumstatin repress the growth of tumor, accompanying the decreased density of CD31 positive vessels in tumors ((5.62 ± 1.32)/HP), compared to the control-transfectants group ((23.84 + 1.71)/HP) and wild type U251 glioma cells group ((29.33 + 4.45)/HP).</p><p><b>CONCLUSION</b>Anti-angiogenic gene therapy using human tumstatin gene may be an effective strategy for the treatment of glioma.</p>