Abstract 444: Slit2 stimulation induces a chemorepellent effect on the migration of human GBM brain tumor initiating cells

Gioblastoma (GBM) is the most common and aggressive form of primary brain tumor in adults. Despite the use of radiotherapy, chemotherapy, and surgery, survival still averages 14 months. GBM has a recurrence of almost 100% due to highly invasive brain tumor initiating cells (BTICs) left behind after surgery. As reported by our group and others, survival expectancy of GBM patients is greatly affected by tumor location. Specifically, tumors in close proximity to the lateral ventricles (LV) show a higher incidence of distant recurrence, as well as worse survival expectancy. This location is the site of the subventricular zone (SVZ), the largest neurogenic niche in the adult brain of mammals, which maintains continuous production of neural stem cells (NSCs) throughout adult life. The cause for worse prognosis in patients whose tumors are in close proximity to the SVZ is not known, but one hypothesis is that regulators of the neurogenic niche might be influencing tumor cells to become more invasive and migratory. In rodents, Slit-Robo is one of these signals which functions as a chemorepulsive ligand-receptor system involved in guiding the migration of newly generated NSCs from the SVZ to other regions of the central nervous system. Further, it has been found that Slit2 affects the migration of glioma and medulloblastoma commercial cell lines. We have previously demonstrated that primary cultured human GBM BTICs respond to slit stimulation in a chemorepellant manner. However, the robo receptor implicated in this response as well as the intracellular mechanisms affected by Slit stimulation in BTICs have not been described. Here we propose to study the effects of Slit-2 stimulation on the migration of human GBM BTICs obtained from intraoperative samples. Furthermore we evaluated the activity of Rac1 and CDC42 in GBM BTICs upon slit stimulation. We determined that Robo1 is expressed by multiple primary human GBM samples. BTICs obtained from these samples present a migratory behavior in vitro that presents a chemorepellent response upon slit2 stimulation. This chemorepellant response is not due to a decrease of cell migration as Slit2 stimulation also induced an increase in BTIC migration speed. This migratory response of BTICs to Slit2 is decreased when the Robo1 receptor is knocked down using shRNA transduction. Intracellularly, we observed that Slit2 stimulation induces a decrease in the active (GTP-bound forms) of Rac1 and CDC42. Our findings demonstrate that Slit2 can induce a chemorepellent effect on the migration of human GBM BTICs through the activation of Robo1 receptor and the subsequent modulation of the Small GTPases Rac1 and CDC42. Our results indicate that regulators of SVZ cells migration can also affect GBM cells behavior and could potentially contribute to the more aggressive behavior of SVZ-contacting GBMs. Citation Format: Hugo Guerrero-Cazares, Emily Lavell, Gabrielle Drummond, Sural Ranamukhaarachchi, Vivian Capilla-Gonzalez, Paula Schiapparelli, Alfredo Quinones-Hinojosa. Slit2 stimulation induces a chemorepellent effect on the migration of human GBM brain tumor initiating cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 444. doi:10.1158/1538-7445.AM2015-444