Abstract
Abstract Chondrosarcomas are malignant bone tumors that produce cartilaginous matrix. Mutations in isocitrate dehydrogenase enzymes (IDH1/2) were recently described in several cancers, including chondrosarcomas. IDH mutations detected in human cancers invariably are heterozygous missense substitutions. These mutations lead to the inability of IDH to convert isocitrate into α-ketoglutarate (α-KG). Instead, α-KG is reduced into 2-hydroxyglutarate (D-2HG), an oncometabolite. Due to the structural similarity between D-2HG and α-KG, it has been reported that high levels of D-2HG competitively inhibit α-KG-dependent dioxygenases such as TET, JHDM and PHD enzymes, thus contributing to tumorigenesis. We sought to determine the role of IDH1 mutations in the tumorigenesis of human chondrosarcomas by inactivating mutant IDH1 using pharmacological and genetic approaches. In our study, we employed two human chondrosarcoma cell lines, JJ012 and HT1080, that carry endogenous IDH1 mutations. IDH mutation analysis was performed by PCR-based DNA sequencing, and D-2HG levels were measured by tandem mass spectrometry. Mutant IDH1 was knocked down via siRNA and knocked out via CRISPR/Cas9. We analyzed the effect of mutant IDH1 on chondrosarcoma growth in murine xenograft models. We found that knockdown of mutant IDH1 via siRNA significantly reduced D-2HG production in chondrosarcoma cells. In addition, mutant IDH1 knockdown dramatically inhibited colony formation in the sarcoma cells. Consistently, genetic knockout of mutant IDH1 almost completely depleted D-2HG production and significantly inhibited colony formation in the chondrosarcoma cells. To assess the significance of these results in vivo, we implanted the mutant IDH1- knockout cells in nude mice and studied their capacity for tumor initiation and growth. In these models, we observed that loss of mutant IDH1 led to a marked attenuation of chondrosarcoma formation. Our findings clearly demonstrate that mutant IDH1 plays a vital role in chondrosarcoma tumor formation. By investigating the role of IDH mutations in the pathogenesis of chondrosarcomas, we aim to uncover the potential therapeutic targets against this aggressive cancer. Citation Format: Luyuan Li, Xiaoyu Hu, Josiane E. Eid, Joanna DeSalvo, Jonathan C. Trent. Mutant IDH1 is essential for chondrosarcoma growth [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 864.
