Therapeutic implications of CD73-sirna delivery on glioblastoma surgical treatment: a histopathological approach

Introduction: Glioblastoma is the most devastating form of brain tumor, characterized by an average survival of 10 months. Standard therapy consists of cytoreductive surgery followed by radio and chemotherapy. Although the therapeutic procedures are already well established, clinical practice has shown that extensive surgeries are not related to increased patient survival rate. In addition, frequent recurrences are seen due to tumor infiltration to cerebral parenchyma. Thus, it is necessary to establish new therapies that increase surgery success, avoiding tumor recurrences. In tumor microenvironment, nucleotides are released by a variety of cell types in response to stress signals. These nucleotides are hydrolized by ectonucleotidases located on cell surface, including the NTPDases which metabolize ATP and ADP to AMP and ecto-5’-nucleotidase/CD73 that converts AMP to adenosine.

Method: Studies have shown that CD73 play a crucial role in tumor progression and its modulation may be an interesting strategy for glioblastoma therapy. Here we evaluated the impact of CD73 inhibition on in vivo tumor growth in a pre-clinical rat glioblastoma model. C6 glioma cells were implanted in Wistar rat brain by stereotactic surgery. Animals were gruped as follow: vehicle control, GFP-SIRNA (control scramble) and CD73-SIRNA (CD73 knockdown group); and they were treated via intracerebroventricular route using lipofectamine as carrier on 7, 14 and 21th day after glioma implant. Rats were euthanasied at 23th day. Tissues were stained by HE, tumor volume was measured using ImageJ software and histopathological analysis was performed by a pathologist in a blided manner (Approval protocol number 293/14).

Conclutions: Results indicate that CD73 knockdown using SIRNA strategy reduced 45% tumor volume when compared to control groups. Moreover, 80% of treated tumors exhibited lymphocytic infiltration and coagulative necrosis, compared to 20% and 40% of control groups, respectively. Therefore, as CD73 silencing decreased tumor volume and improved histological characteristics related to better prognosis, CD73-SIsRNA treatment may be considered as neoadjuvant therapy to increase surgery success. Such strategy may reduce not only herniations and postoperative edema, a fact observed in tumors of large volume, but also the technique of partial resection, preventing the syndrome of injured glioma.