Determination of CD117 Expression in Glial Tumors and Its Comparison between High Grade and Low Grade Tumors

Background and Objective: Gliomas are the most common primary brain tumors. Despite therapeutic advances, the majority of gliomas do not respond to either chemo or radiotherapy. CD117, the gene product of c-kit has been expressed in cells of glial tumors. Because gastrointestinal stromal tumors (GISTs) that express CD117 respond dramatically to treatment with tyrosine kinase inhibitors, identification of glial tumors that express CD117 might open new therapeutic approaches for treatment of these tumors. Material and Methods: CD117 expression was investigated in 69 glial tumors of different types and grades. This protein was visualized by immunohistochemistry with commercially available antibody. The comparison of CD117 expression between high and low-grade tumors was evaluated with SPSS V16 soft ware and Chi square test. Results: Forty two percent of the tumors were positive for CD117 expression. There was a statistically significant difference in CD117 immunoreactivity between high grade and low-grade tumors (61.1% versus 21.2%, P=0.001). 96.6% of the positive cases had cell membranous and/ or cytoplasmic staining. All except two of the positive cases showed strong expression intensity. In 26.1% of cases, CD117 also expressed in endothelial cells of tumor vessels that 88.9% of them was in high-grade tamors. Glioblastoma, anaplastic oligodendroglioma and anaplastic ependymoma showed the highest staining grade. Conclusion: CD117 has an important role in growth of glial tumors, especially high grade ones and that patients with CD117 expressing glial tumors might benefit from tyrosine kinase inhibitors. This finding should be further studied.