TMOD-25. IN VIVO MODEL OF TREATMENT-RESISTANT GLIOBLASTOMA HIGHLIGHTS SEX DIFFERENCES IN SURVIVAL

Abstract BACKGROUND Sex differences independent from acute hormone action are evident in the incidence and tumorigenesis of several cancers, including glioblastoma (GBM). Malignant brain tumors with mesenchymal, proneural, and neural GBM subtypes occur twice as frequently in males than in females, implying a molecular basis for the sex disparities observed. Accordingly, response to therapy and overall survival, may also differ between male and female GBM patients. Further elucidation of these differences would benefit from a robust preclinical testing system, such as the one described here. METHODS Adult (U87-MG) GBM cells were exposed to a total radiation dose of 10 Gy, effecting an epithelial to mesenchymal transition. The resultant irradiated U87-10Gy cells were tested for cell viability and allowed to reach confluence prior to stereotactic implantation into the right striatum of male and female athymic rats. In vivo advanced MR imaging at 9.4T was carried out weekly starting two weeks after implantation. Advanced MRI parameters were processed for enhancing tumor ROIs in OsiriX 8.5.1 (lite) with Imaging Biometrics™ Software (IQ-AI, Ltd.). RESULTS Tumor take was 90% in males and 60% in females, indicating an ‘incidence’ ratio of 1.5. Overall survival was significantly higher in females (median = 48, range = 40-72 days) than in males (median = 28, range = 27-30 days) (p = 0.024). Immunohistochemical and imaging analyses are pending and will be discussed. CONCLUSION The outcomes noted in this pilot study mirror incidence and survival outcomes noted in GBM patients undergoing standard care. Our model of treatment-resistant glioma provides a robust testing system to study underlying sex differences in GBM biology and treatment response in parallel analyses of male and female data.