Mutant IDH is sufficient to initiate enchondromatosis in mice Makoto Hirata a , Masato Sasaki b , Rob A. Cairns b , Satoshi Inoue b , Vijitha Puviindran c , Wanda Y. Li b , Bryan E. Snow b , Lisa D. Jones b , Qingxia Wei a , Shingo Sato a , Yuning J. Tang a , Puviindran Nadesan c , Jason Rockel a , Heather Whetstone a , Raymond Poon a , Angela Weng a , Stefan Gross d , Kimberly Straley d , Camelia Gliser d , Yingxia Xu e , Jay Wunder f , Tak W. Mak b,1,2 , and Benjamin A. Alman a,c,1,2 a Program in Developmental and Stem Cell Biology, Hospital for Sick Children, Toronto, ON, Canada, M5G 0A4; b The Campbell Family Institute for Breast Cancer Research, Ontario Cancer Institute, University Health Network, Toronto, ON, Canada, M5G 2C1; c Department of Orthopedic Surgery, Duke University, Durham, NC 27710; d Agios Pharmaceuticals, Cambridge, MA 02139; e Chempartner, Shanghai 201203, China; and f Department of Orthopedic Surgery, Mount Sinai Hospital, Toronto, ON, Canada, M5G 1X5 Contributed by Tak W. Mak, December 29, 2014 (sent for review November 11, 2014; reviewed by Navdeep S. Chandel, Nicholas C. Denko, and Jorge Moscat) Enchondromas are benign cartilage tumors and precursors to malignant chondrosarcomas. Somatic mutations in the isocitrate dehydrogenase genes (IDH1 and IDH2) are present in the majority of these tumor types. How these mutations cause enchondromas is unclear. Here, we identified the spectrum of IDH mutations in human enchondromas and chondrosarcomas and studied their effects in mice. A broad range of mutations was identified, includ- ing the previously unreported IDH1-R132Q mutation. These mu- tations harbored enzymatic activity to catalyze α-ketoglutarate to D-2-hydroxyglutarate (D-2HG). Mice expressing Idh1-R132Q in one allele in cells expressing type 2 collagen showed a disordered growth plate, with persistence of type X-expressing chondrocytes. Chondrocyte cell cultures from these animals or controls showed that there was an increase in proliferation and expression of genes characteristic of hypertrophic chondrocytes with expression of Idh1-R132Q or 2HG treatment. Col2a1-Cre;Idh1-R132Q mutant knock-in mice (mutant allele expressed in chondrocytes) did not survive after the neonatal stage. Col2a1-Cre/ERT2;Idh1-R132 mu- tant conditional knock-in mice, in which Cre was induced by tamox- ifen after weaning, developed multiple enchondroma-like lesions. Taken together, these data show that mutant IDH or D-2HG causes persistence of chondrocytes, giving rise to rests of growth-plate cells that persist in the bone as enchondromas. isocitrate dehydrogenase | cartilage tumor | hedgehog E nchondromas, one of the most common benign tumors oc- curring in bone, are present in more than 3% of the popula- tion (1, 2). They are composed of cells derived from chondrocytes and occur as solitary lesions or multiple lesions in enchon- dromatosis syndromes (Ollier disease or Maffucci syndrome—in the latter, enchondromas are associated with vascular malfor- mations). Clinical problems caused by enchondromas include pain, fractures, and skeletal deformity. There is a potential for malignant progression to chondrosarcoma that may be greater than 50% in some cases of multiple enchondromatosis (i.e., Maffucci syndrome) (3–7). Many chondrosarcomas are thought to derive from enchondromas, and such sarcomas are termed central chondrosarcomas (3). The hedgehog (Hh) signaling pathway is constitutively active in enchondromas and chondrosarcomas (8, 9). Hh is important in growth-plate chondrocyte differentiation, where it cooperates with parathyroid hormone-like hormone in a negative feedback loop to inhibit the differentiation of proliferative growth-plate chondrocytes (6, 10–14). Disruption of this feedback loop can result in either skeletal dysplasias with abnormal bone growth or enchondromas; 5% of enchondromas harbor mutation in para- thyroid hormone-like hormone receptor (PTHR1), resulting in activation of Hh signaling (6, 10–14), and expression of a mutant PTHR1 or overexpression of the Hh-regulated transcription factor Gli2 under the Col2a1 promoter causes enchondroma-like cartilage lesions to develop adjacent to the growth-plate cartilage in mice (8). The majority of enchondromas and chondrosarcomas harbor somatic isocitrate dehydrogenase 1 (IDH1) or IDH2 mutations (15–18). Mutations in IDH genes are common in several other neoplasms, including glioma, glioblastoma, acute myeloid leu- kemia, angioimmunoblatic T-cell lymphoma, and intrahepatic cholangiocarcinomas (19–22). Biochemical studies in these cancer types identified a neomorphic enzymatic activity of the mutant IDH that converts α-ketoglutarate (α-KG) to D-2-hydrox- yglutarate (D-2HG), which builds up to high concentrations in IDH mutant cells. D-2HG can competitively inhibit the func- tion of a large group of α-KG–dependent enzymes and thereby, modulate a number of cellular processes, including DNA methylation, histone methylation, and activity of hypoxia- inducible factor 1α (23–25). However, how IDH mutations contribute to enchondroma and chondrosarcoma tumorigenesis is unclear. We previously established tissue-specific Idh1 mutant knock-in (KI) mice and reported the pathological phenotypes in the he- matopoietic system and the brain. Specifically, the Idh1-KI mu- tant mouse lines showed brain hemorrhage, increased numbers Significance Current genomic and biochemical analysis revealed mutations in isocitrate dehydrogenase (IDH) genes associated with sev- eral neoplasms and a novel enzymatic activity of IDH mutations to catalyze α-ketoglutarate to D-2-hydroxyglutarate, contrib- uting to tumorigenesis. We identified a broad range of IDH1 mutations, including a previously unidentified IDH1-R132Q mutation, in cartilage tumors. Cartilage-specific Col2a1-Cre/ ERT2;Idh1-R132 mutant knock-in mice developed multiple enchondroma-like lesions. These data show that mutant Idh in growth-plate cells causes persistence of chondrocytes, giving rise to enchondromas adjacent to the growth cartilage in bone. Author contributions: M.H., M.S., R.A.C., S.I., V.P., S.G., J.W., T.W.M., and B.A.A. designed research; M.H., R.A.C., S.I., V.P., W.Y.L., B.E.S., L.D.J., Q.W., S.S., Y.J.T., P.N., J.R., H.W., R.P., A.W., S.G., K.S., C.G., Y.X., and J.W. performed research; M.S. contributed new reagents/ analytic tools; M.H., R.A.C., S.I., V.P., Q.W., S.S., Y.J.T., P.N., J.R., H.W., R.P., A.W., S.G., K.S., C.G., J.W., T.W.M., and B.A.A. analyzed data; and M.H., R.A.C., and B.A.A. wrote the paper. Reviewers: N.S.C., Northwestern University; N.C.D., Ohio State University School of Medicine; and J.M., Sanford-Burnham Medical Research Institute. The authors declare no conflict of interest. Freely available online through the PNAS open access option. 1 T.W.M. and B.A.A. contributed equally to this work. 2 To whom correspondence may be addressed. Email: [email protected] or [email protected]. This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. 1073/pnas.1424400112/-/DCSupplemental. www.pnas.org/cgi/doi/10.1073/pnas.1424400112 PNAS | March 3, 2015 | vol. 112 | no. 9 | 2829–2834 MEDICAL SCIENCES Downloaded from https://www.pnas.org by 117.3.248.167 on June 21, 2023 from IP address 117.3.248.167.
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