Abstract 3153: Slit-2 directs the migration of primary cultured human GBM tumor initiating cells

Abstract

Abstract Glioblastoma multiforme (GBM), the most aggressive and proliferative primary brain tumor, has an extremely high recurrence incidence. This is mainly due to cancer cell invasion of brain parenchyma beyond surgical boundaries. Brain tumor initiating cells (BTICs) are stem-like cells with properties of self-renewal and multipotency. BTICs are able to migrate to initiate tumor formation away from the original tumor and are highly resistant to chemo and radiotherapy, suggesting that they are responsible for tumor recurrence. Understanding the mechanisms affecting the migration of BTICs may shed light on mechanisms for preventing GBM recurrence. Cell migration and proliferation events present during brain development are recapitulated in the fundamental hallmarks of cancer. In rodents, Slit-Robo signaling functions as a chemorepulsive ligand-receptor system involved in guiding the migration of newly generated cells from the subventricular zone to other regions of the central nervous system. In neural cancers, Slit2 affects the migration of glioma and medulloblastoma cell lines. We hypothesized that Slit proteins have a chemorepellant effect on primary-cultured human GBM-derived BTICs, which promotes tumor dispersal. Primary BTIC cultures were established from GBM intraoperative samples and maintained in neurosphere culture media containing EGF and bFGF, heparin and LIF, which maintains the presence of stem cells. Expression of Slit and Robo was then evaluated at the mRNA and protein level. Our results revealed that Slit2 induces a chemorepulsive effect on Robo-expressing BTICs, as evaluated by transwell migration and chemotaxis assays (p<0.05). Slit2 also induces a significant increase in cell speed (p<0.05). Moreover, we did not see any effects of Slit2 on cell proliferation or viability. We further observed that Slit2 stimulation of BTICs induces a decrease in AKT activity and an increase in MYPT1/MLC2; proteins involved in actin polymerization. In summary, we demonstrated that Robo1 is expressed in different primary human GBM BTICs. As result, Slit2 acts on the migration of these cells in a chemorepellant manner, while increasing speed. The mechanisms responsible for these observations involve actin polymerization and Akt signaling. While further research is required, the effects of Slit-2 proteins on the migration behavior of human GBM BTIC cells may be related to the invasive nature of these tumors. Citation Format: Hugo Guerrero-Cazares, Vivian Capilla-Gonzalez, Emily A. Lavell, Alejandro Ruiz-Valls, Linda Chen, Gabrielle Drummond, Sural Ranamukhaarachchi, Alfredo Quinones-Hinojosa. Slit-2 directs the migration of primary cultured human GBM tumor initiating cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3153. doi:10.1158/1538-7445.AM2014-3153