HG-12: LIN28 AND MYC EXPRESSING PEDIATRIC GLIOBLASTOMAS ARE SENSITIVE TO INHIBITORS OF GLUTAMINE METABOLISM

We have previously shown that LIN28A protein is highly expressed in a subset of pediatric glioblastoma (GBM). Knockdown of LIN28A using lentiviral shRNA in GBM cell lines inhibits their invasion, growth and clonogenicity. LIN28A downregulates the let-7 family of tumor suppressing microRNAs, and these in turn inhibit multiple oncogenes including MYC. LIN28 is also known to regulate cellular metabolism in normal and transformed cells. We hypothesized that LIN28 would contribute to GBM tumorigenicity in part by modifying cellular metabolism. Pediatric GBM express MYC and NMYC, and these oncogenes also promote tumorigenicity through increasing proliferation, invasion and altering cellular metabolism. Addition of LIN28A to the JHH- GBM14 cell line leads to upregulation of MYC and glutaminase (GLS) as measured by western blot. The inhibitors of glutamine metabolism DON (6-Diazo-5-oxo-L-norleucine) and acivicin suppress the growth of LIN28A-transduced GBM14 cells to a greater extent than control empty-vector transduced cells in MTT assays (p = 0.008 for 5 uM DON, Student's t-test; p = 0.03, 5 uM acivicin, Student's t-test). We found that the pediatric high grade glioma cell lines SF188, UW479, SJ-GBM2, and KNS42 express varying levels of LIN28, MYC, and NMYC and have robust GLS expression by western blot. Acivicin treatment decreased the growth of SF188, KNS42 and UW479 in MTT Assays (P < .005 10 uM acivicin, Student's t-test). DON and acivicin have been tested in phase I clinical trials in children, but never extensively investigated in aggressive pediatric brain tumors. Our data suggest that LIN28 can alter GBM cellular metabolism in a way that confers sensitivity to inhibitors of glutamine metabolism and that these agents may be of therapeutic use in pediatric high grade gliomas.