Abstract 15: Targeting vismodegib-resistant medulloblastoma using novel hedgehog pathway inhibitor and miR-29b mimic

Abstract

Abstract The purpose of this study to develop targeted liposomes of MDB5 and miR-29b combination for medulloblastoma (MB) treatment. Due to high heterogeneity and diverse genetic make-up, MB treatment is a challenge. Aberrant activation of hedgehog (Hh) pathway regulates cell growth, cancer stem cell (CSC) proliferation, and tumorigenicity in sonic Hh subgroup of MB. Further, Hh signaling regulates yes-associated protein 1 (YAP1) and glutaminolysis for energy need of tumor cells. GDC-0449 a smoothened receptors (SMO) antagonist treats (SHH)-MB initially, but resistance develops after repeated administration. Cholesterol potentiates Hh pathway independent of SHH by binding directly to the SMO. On the other hand, our RNA-seq and miRNA profiling confirmed downregulation of tumor suppressor miR-29b-3p in human MB samples. miR-29b control genes of apoptosis; p53, MDM2, AKT2, and cholesterol biosynthesis including HMGCR and SREBP1. We recently synthesized a potent GDC-0449 analog MDB5 (SMO inhibitors), which binds strongly to various Smo-mutants compared to GDC-0449. We found that a combination of MDB5 and miR-29b can treat MB synergistically. When we modified miR-29b backbone with 2-O’-methoxyethyl phosphorothioate (OMe-PS-miR-29b-3p), it showed enhanced stability in 50% serum. We designed a cationic lipid MDC2 for liposomal delivery of MDB5 and miR-29b1 simultaneously. Liposomes were prepared using film hydration technique and characterized for particle size and zeta potential, drug loading and release profile, miRNA complexation, stability, and transfection efficiency. These liposomes incorporated 88% MDB5 when the drug to phospholipid molar ratio was kept at 5%. Complete complexation was observed at N/P ratio of 3:1. These liposomes when loaded with green fluorescent protein (GFP) siRNA, resulted in 70% of signal silencing into DAOY MB cells (Shh driven). Liposomal MDB5 had higher cytotoxicity in DAOY cells compared to GDC-0449. Further, MDB5 and OMe-PS-miR-29b loaded liposomes resulted in higher, cytotoxicity and % of apoptosis, G0-G1 phase arrest, and decreased target gene expression in DAOY cells. Combination of drugs to simultaneously target multiple pathways related to Hh, glutaminolysis, cholesterol biosynthesis, and apoptosis has the potential to treat MB. Successful completion of this study will provide a nanomedicine for treating SHH-MB and other brain tumors. Citation Format: Virender Kumar, Bharti Sethi, Vinod Kumar, Timothy R. Mcguire, Don W. Coulter, Ram I. Mahato. Targeting vismodegib-resistant medulloblastoma using novel hedgehog pathway inhibitor and miR-29b mimic [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 15.