DIPG-29. DFMO AND PANOBINOSTAT TARGET LIN28 AND HDAC IN DIPG DECREASING CELL VIABILITY. (23rd April 2019) - Maser, Tyler
Abstract: BACKGROUND: Diffuse intrinsic pontine glioma (DIPG) is an aggressive pediatric cancer with a poor prognosis of < 10% overall survival at 2 years from diagnosis. Due to their location DIPG presents a therapeutic challenge with radiation as the mainstay of therapy. Over 80% of DIPG tumors harbor a K27M mutation in genes encoding H3 histone variants, causing epigenetic dysregulation. Previous work has shown that treatment with the histone deacetylase (HDAC) inhibitor Panobinostat decreases DIPG tumor growth and viability in preclinical studies. In addition, LIN28 and MYCN have been shown to portend poor prognosis in CNS tumors. DFMO (α-difluoromethylornithine) has been shown to reverse this Lin28/let-7 axis and suppress MYCN in neuroblastoma cells and improve overall survival in neuroblastoma patients. Therefore, we hypothesize this may be effective in DIPG and combined with panobinostat. METHODS: DNA/RNA sequencing of 11 DIPG cell lines were evaluated for mutation and pathway analysis. High-throughput drug testing of 88 drugs was completed in DIPG cell lines which identified Panobinostat and DFMO as potential therapies for DIPG. Testing of these in combination studies using CellTiter-Glo, western blots and flow cytometry was performed to evaluate response and mechanism. RESULTS: RNA sequencing of 11 DIPG cell lines identified upregulation of HIST1H3B, HMGA2, LIN28 and MYCN. DFMO reduces cell viability of DIPG cells in a time and dose dependent manner as shown by cell viability assay and flow cytometry. This reduction in viability is further enhanced with the addition of Panobinostat. Western blot and flow cytometry confirm that DFMO suppresses LIN28 in DIPG. CONCLUSION: Due to the importance of epigenetic dysregulation and the upregulation of the LIN28 pathway in DIPG tumors we demonstrated that the combined treatment of Panobinostat and DFMO is a viable therapeutic option for DIPG and will be tested in an upcoming clinical trial.