Abstract B41: Modeling bone development and cancer predisposition in Diamond Blackfan anemia (DBA)

DBA is an inherited bone marrow failure syndrome characterized by pure red cell aplasia, congenital physical anomalies, and cancer predisposition, in particular an increased incidence of osteogenic sarcoma (O:E 42.44). In order to investigate the mechanism of defective bone development and ultimately oncogenesis, we used an in vitro model consisting of mouse embryonic stem cells gene trapped for the Ribosomal Protein 19 gene (Rps19) and developed an in vivo transgenic conditional mouse model with floxed Rps19 alleles and a bone-specific expressing Col1a1-CreER. Using a 23-day stepwise osteoblast differentiation model, haploinsufficient Rps19+/- mouse ES cells did not show differences in the ability to develop into mesodermal progenitors based on qPCR analysis of mesodermal transcription factors, but displayed a decreased ability to produce mature osteoblasts based upon decreased alizarin red staining. In addition, higher levels of the Trp53 protein were found in Rps19+/- mouse ES cells at both the pluripotent and mesodermal stages of differentiation. Further, Rps19+/- mouse ES cells presented with aberrant WNT signaling, as represented by decreased levels of β-catenin early in osteoblast differentiation and rising to higher levels towards late osteoblast differentiation. We assessed the hypothesis of WNT signaling involvement in lineage specification and found that Rps19+/- mouse ES cell-derived osteoblasts show decreased levels of Runx2 and increased levels of Sox9. In the transgenic mouse model, tamoxifen-induced recombination of Rps19 at E15-17 did not show gross morphologic skeletal defects at E20.5 for Rps19fl/+ embryos, although Rps19fl/fl embryos displayed severe skeletal defects through alizarin red and alcian blue staining. In conclusion, haploinsufficient levels of Rps19 found in mice contribute to improper skeletal development and probably reflect the clinical scenario. We plan to utilize these in vitro and in vivo models to provide clues into the mechanism of ribosomal protein haploinsufficiency in tumor development, which may suggest surveillance and treatment strategies. Citation Format: Jimmy Hom, Brian Dulmovits, Luanne Peters, Adrianna Vlachos, Jeffrey M. Lipton, Lionel Blanc. Modeling bone development and cancer predisposition in Diamond Blackfan anemia (DBA) [abstract]. In: Proceedings of the AACR Special Conference: Pediatric Cancer Research: From Basic Science to the Clinic; 2017 Dec 3-6; Atlanta, Georgia. Philadelphia (PA): AACR; Cancer Res 2018;78(19 Suppl):Abstract nr B41.