Inhibition of mutant IDH1 decreases D-2-HG levels without affecting tumorigenic properties of chondrosarcoma cell lines

// Johnny Suijker 1 , Jan Oosting 1 , Annemarie Koornneef 1 , Eduard A. Struys 2 , Gajja S. Salomons 2 , Frank G. Schaap 1 , Cathelijn J.F. Waaijer 1 , Pauline M. Wijers-Koster 1 , Inge H. Briaire-de Bruijn 1 , Lizette Haazen 3 , Scott M. Riester 4 , Amel Dudakovic 4 , Erik Danen 3 , Anne-Marie Cleton-Jansen 1 , Andre J. van Wijnen 4 and Judith V.M.G. Bovee 1 1 Department of Pathology, Leiden University Medical Center, Leiden, The Netherlands 2 Metabolic Unit, Department of Clinical Chemistry, VU University Medical Center, Neuroscience Campus Amsterdam, Amsterdam, The Netherlands 3 Division of Toxicology, Leiden Academic Center for Drug Research, Leiden University, Leiden, The Netherlands 4 Department of Orthopedic Surgery, Mayo Clinic, Rochester, NY, USA Correspondence to: Judith V.M.G. Bovee, email: // Keywords : isocitrate dehydrogenase, d-2-hydroxyglutarate, chondrosarcoma, sarcoma, AGI-5198 Received : February 03, 2015 Accepted : March 05, 2015 Published : March 30, 2015 Abstract Mutations in isocitrate dehydrogenase 1 (IDH1) and IDH2 are found in a subset of benign and malignant cartilage tumors, gliomas and leukaemias. The mutant enzyme causes the production of D-2-hydroxyglutarate (D-2-HG), affecting CpG island and histone methylation. While mutations in IDH1/2 are early events in benign cartilage tumors, we evaluated whether these mutations play a role in malignant chondrosarcomas. Compared to IDH1/2 wildtype cell lines, chondrosarcoma cell lines harboring an endogenous IDH1 (n=3) or IDH2 mutation (n=2) showed up to a 100-fold increase in intracellular and extracellular D-2-HG levels. Specific inhibition of mutant IDH1 using AGI-5198 decreased levels of D-2-HG in a dose dependent manner. After 72 hours of treatment one out of three mutant IDH1 cell lines showed a moderate decrease in viability , while D-2-HG levels decreased >90%. Likewise, prolonged treatment (up to 20 passages) did not affect proliferation and migration. Furthermore, global gene expression, CpG island methylation as well as histone H3K4, -9, and -27 trimethylation levels remained unchanged. Thus, while IDH1/2 mutations cause enchondroma, malignant progression towards central chondrosarcoma renders chondrosarcoma growth independent of these mutations. Thus, monotherapy based on inhibition of mutant IDH1 appears insufficient for treatment of inoperable or metastasized chondrosarcoma patients.