Abstract 6150: The role of oxidative phosphorylation in a novel iPSC &lt;-&gt;derived model of osteosarcomagenesis
Authors: Jewell Brittany Ellis , Xu An , Zhu Dandan , Lu Linchao , Zhao Ruiying , Wang Lisa L. , Lee Dung-Fang 
Published: September 2020

Abstract
Osteosarcoma is the most common bone malignancy in childhood and early adolescence. Thirty percent of patients with the rare genetic disorder Type II Rothmund- Thomson Syndrome (RTS) develop osteosarcoma. Patients with Type II RTS have biallelic mutations in the RECQL4 gene, which encodes an ATP dependent DNA helicase. Unfortunately, many attempts to model RTS associated osteosarcoma have not been successful. Here, we describe a patient-derived induced pluripotent stem cell (iPSC) model capable of recapitulating the process of osteosarcomagenesis. The main goal of our inquiry is to develop a new model to study osteosarcoma in order to elucidate cellular pathways important in osteosarcomagenesis that are potential therapeutic targets.
RTS patient fibroblasts were reprogrammed to iPSCs, then subsequently differentiated to mesenchymal stem cells. These cells were validated as pluripotent and then further differentiated to early and late osteoblasts, the potential precursors of osteosarcoma. This model of osteoblast development provides an unlimited resource for inquiry into the molecular mechanism of osteosarcomagenesis. Clear advantages of the iPSC derived osteoblasts include the isogenic nature of the cells, as these iPSC-derived osteoblasts retain the genetic fidelity of the patient from which they were derived. We have also isolated matched parental cells and similarly reprogrammed and differentiated them in order to provide ideal matched controls with clinical relevance, as the parents are heterozygous for the same RECQL4 mutation, yet do not develop osteosarcoma. We believe these cells are the ideal model to study the molecular mechanism associated with RTS-associated osteosarcoma.
In order to gain better insight into osteosarcoma pathophysiology, we utilized the iPSC-derived osteoblasts to perform RNAseq and subsequent GSEA and DEseq2 analyses. From these transcriptional studies, we have found dysregulation of oxidative phosphorylation in the RTS patient samples compared to their parental controls. We specifically observe differences in complexes I, III, and IV of the electron transport chain. Interestingly, we also observe changes in vacuolar ATPases that are function to increase proton concentration in the cell and within the extracellular environment. This is consistent with phenomena observed in other cancers, which have been observed to have a similar increase in v-ATPases on the plasma membrane. Inhibitors of these complexes provide us with a starting point to address new therapeutic options for patients.
Citation Format: Brittany Ellis Jewell, An Xu, Dandan Zhu, Linchao Lu, Ruiying Zhao, Lisa L. Wang, Dung-Fang Lee. The role of oxidative phosphorylation in a novel iPSC &lt;-&gt;derived model of osteosarcomagenesis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6150.