Abstract 3865: Targeting MYC high osteosarcoma through EYA2 modulation

Abstract Osteosarcoma is the most common bone cancer in children, adolescent and young adults. Recent large scale genomic studies have started to reveal that Osteosarcoma (OS) patients who have tumors that highly express the transcription factor MYC, are significantly at high risk of treatment failure. However, MYC has long been known to be extremely difficult to target with drugs. The EYA protein is an evolutionarily conserved transcriptional co-activator of the SIX1 family of homeobox proteins, which also has phosphatase activity. Multiple studies have shown that EYA is involved in the initiation and progression of various cancers. EYA Tyrosine Phosphatase has been shown to regulate MYC expression and protein stability in Brain tumors. In OS cells, EYA2 is highly expressed and has been indicated to be involved in tumor progression and invasion, but the interaction between EYA2 and MYC is unknown. The major goal of our study is to clarify the effect of EYA2 on the expression of MYC in OS cells, and evaluate it as a therapeutic target. First, EYA2 and MYC expression in various OS cell lines were confirmed using western blotting. Next, we established EYA2 shRNA knock-down in 143B cells and CHCO-OS1 cells, which highly express both EYA2 and MYC. Interestingly, in these cells, EYA2 knock-down led to decreased MYC expression, decreased clonogenicity and proliferation. Furthermore, EYA2 knock-down led to decreased cell migration in 143B cells when measured by a scratch assay using the Incucyte live cell imaging. Next, we also tested 9987, an allosteric EYA2 phosphatase inhibitor. Here, 9987 was shown to inhibit the clonogenicity, proliferation and migration compared to DMSO control. These results indicate that in MYC-high OS cells, EYA2 knockdown leads to decreased MYC expression, decreased proliferation, clonogenicity, and migration, and EYA2 phosphatase inhibition is a promising therapeutic strategy for this tumor. We are currently confirming whether the EYA2 inhibitor 9987 can reduce metastatic rate and extend overall survival in our orthotopic-implantation-amputation mouse model, and further identifying the mechanisms of how EYA2 regulates MYC activation in OS. Citation Format: Ryota Shirai, Sydney Hakim, Avery Bodlak, Masanori Hayashi. Targeting MYC high osteosarcoma through EYA2 modulation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3865.