Metabolitin-based molecular drug delivery by targeting GPR158 in glioblastoma

Glioblastoma multiforme (GBM) is a lethal form of intracranial tumor. One of the obstacles to treat GBM is the blood-brain barrier which limit the transportation of drugs into the tumor site. Here, based on our previous study on metabolitin (MTL) and osteocalcin, we generated a molecular drug delivery system that consisted of metabolitin and small molecules such as fluorescent dye or peptide drugs for diagnosis and treatment. And we designed a GBM diagnostic probe (MTL-ICG) and therapeutic peptide drug (MTL-NBD) that can cross the blood-brain barrier (BBB). In a NIR animal live imaging system, we found MTL-ICG can penetrate cross BBB and label the GBM site. The in vitro experiment showed that MTL-NBD had inhibitory effect on GBM cell line (U87-MG). Besides, after orthotopic transplantation of GBM into mouse cortex, treatment of MTL-NBD intravenously showed inhibition trend, which were similar with the effect of NBD, a known anti-tumor polypeptide drug. In addition, we found the GPR158, the receptor of osteocalcin, was also high expressed in grafting site. Taken together, these findings suggest that MTL is a promising cell penetrating peptide targeting GPR158 in GBM, which provide a novel delivery tool for GBM. ### Competing Interest Statement The authors have declared no competing interest.