Abstract 3359: HEY1::NCOA2 fusion disturbs the transcriptional program of chondrogenic differentiation and activates oncogenes in mesenchymal chondrosarcoma tumorigenesis
Authors: Qi Wenqing , Rosikiewicz Wojciech , Xu Beisi , Wang Lu 
Published: March 2024

Abstract
Mesenchymal chondrosarcoma (MCS) is a rare high-grade mesenchymal neoplasm occurring in bone and soft tissue. It accounts for 2%~10% of all chondrosarcomas and affects mainly adolescents and young adults. Genetically, this tumor is characterized by the recurrent HEY1::NCOA2 fusion. To functionally characterize the fusion in MCS tumorigenesis, we generated stably transduced iPSC-derived mesenchymal stem cells (iPSC-MSC) with inducible expression of HEY1::NCOA2. We previously demonstrated that the expression of HEY1::NCOA2 significantly enhanced cell proliferation, upregulated PDGFB/PI3K/AKT signaling, and induced genes that are involved in chondrocyte differentiation. In this study, we evaluated the impact on chondrogenic lineage differentiation and dysregulated pathways resulting from HEY1::NCOA2 expression and further elaborated oncogenic pathways in MCS tumorigenesis. We first successfully established the differentiation culture of inducing iPSC-MSC on chondrogenic lineage differentiation, showing an increase in glycosaminoglycans and the expression of differentiation markers (COL1A1, COL2A1, ACAN, COMP, SOX9 and COL10A1) at 7-, 14-, and 21-days post treatment with differentiation medium. The iPSC-MSC-HEY1::NCOA2 cells and control cells were cultured for chondrogenic lineage differentiation. During differentiation culture, we collected cells from each condition at multiple time points to (1) monitor the expression of differentiation markers and (2) perform transcriptomic profiling. Principal component analysis showed that cells with the expression of HEY1::NCOA2 possessed a distinct feature from parental cells and control cells, however, HEY1::NCOA2 did not simply suppress chondrogenic differentiation. The differential gene expression indicated that HEY1::NCOA2 fusion disrupted genes related to fine tuning of chondrogenic differentiation (SOX9, COMP, and IGF1) and activated oncogenes (PDGFB, BCL2, CCND1, IGF2, etc.). Notably, we demonstrated that both BCL2 (an anti-apoptotic protein) and COMP (possess antiapoptotic function that protects chondrocytes against death and blocks activation of caspase 3) were directly targeted and consistently upregulated by HEY1::NCOA2 fusion. In addition, the functional classification of genes (n=86) consistently increased with HEY1:: NCOA2 expression through differentiation of the chondrogenic lineage demonstrated that the PI3K/AKT pathway was the most significantly enriched, which further supports targeting the PDGFB/PI3K/AKT axis in MCS therapy. Together, this study sheds light on how HEY1::NCOA2 fusion shapes key mechanisms of chondrogenic differentiation and exerts oncogenic activation. Our findings provide the rationale for anti-apoptosis along with anti-PDGFB/PI3K/AKT signaling in the treatment of mesenchymal chondrosarcoma.
Citation Format: Wenqing Qi, Wojciech Rosikiewicz, Beisi Xu, Lu Wang. HEY1::NCOA2 fusion disturbs the transcriptional program of chondrogenic differentiation and activates oncogenes in mesenchymal chondrosarcoma tumorigenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3359.