Abstract LB200: Pdgf/Pi3k/akt axis activation by hey1-ncoa2 fusion and potential target in the treatment of mesenchymal chondrosarcoma

Abstract

Mesenchymal chondrosarcoma is a rare and often aggressive cancer mostly affecting children and young adults. Genetically, this tumor is mainly characterized by the recurrent HEY1-NCOA2 fusion. Localized tumor is managed surgically; traditional chemotherapy and radiation therapy, however, did not appear to substantially improve the event-free survival rate of mesenchymal chondrosarcoma patients. It is clear that better therapeutic options are needed for the treatment of this tumor. In our previous study, an in vitro model for studying mesenchymal chondrosarcoma tumorigenesis was developed using stably transduced iPSC-derived mesenchymal stem cells (iPSC-MSCs) with inducible-expression of HEY1-NCOA2. With the in vitro model, we performed genome-wide chromatin immunoprecipitation sequencing (ChIP-seq) and RNA-seq to identify HEY1-NCOA2-dependent transcriptional regulation and demonstrated the dramatic activation of PDGF-PDGFR and PI3K-AKT signaling pathways (manuscript in review). Our data also suggested that PDGFB is one of the direct targets of HEY1-NCOA2 fusion protein. In the present study, with the in vitro iPSC-MSC model, we verified that HEY1-NCOA2 fusion protein, but not wild-type HEY1 or NCOA2, dramatically increased phospho-AKT (Ser473, a readout of PI3K) expression by western blotting. Further on, we tested the effect of two kinase inhibitors CP-673451 and PF-04691502, a potent and selective PDGFR inhibitor and the mTOR/PI3K inhibitor, respectively. Stably transfused iPSC-MSC were treated with the kinase inhibitors, respectively, at different dosages (0.1 µM, 0.5 µM and 1.0 µM) for one week. At the concentration of 1.0 µM, CP-673451 efficiently suppressed AKT phosphorylation by ~23% as well as suppressed cell growth by ~67% which is significantly higher than that observed in the controls (e.g. ~20% suppression in HEY1- and NCOA2- expression iPSC-MSCs). Similarly, at the concentration of 0.5 µM, PF-04691502 suppressed the HEY1-NCOA2-expression iPSC-MSCs growth by ~24% more than that in the control (p=0.02). In summary, both CP-673451 and PF-04691502 were active against the in vitro mesenchymal chondrosarcoma model tested. Based on these data, the potential benefit of targeting PDGF/PI3K/AKT signaling pathways in the treatment of mesenchymal chondrosarcoma was suggested. Citation Format: Wenqing Qi, Lu Wang. Pdgf/Pi3k/akt axis activation by hey1-ncoa2 fusion and potential target in the treatment of mesenchymal chondrosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB200.