ROBO1 and pilocytic astrocytoma: In gliomas, Slit2 and its transmembrane receptor ROBO1 have various distribution patterns; in contrast to ROBO1, which is highly expressed in many grades of gliomas at both the mRNA and protein levels, Slit2 is weakly expressed in pilocytic astrocytoma, fibrillary astrocytoma, and glioblastoma [13].