CTSB and glioblastoma: Binding of the leucine-rich G protein-coupled relaxin receptor RXFP1 to C1q-tumor necrosis factor-related protein 8 (CTRP8) ligand mediates increased GBM cell migration, protein kinase C pathway activation, and lysosomal protease cathepsin B production in glioblastoma progenitor cells (158–160).