ZCCHC4-mediated m6A methylation regulates the UHRF1/CDO1 axis to inhibit ferroptosis and promote osteosarcoma malignant progression.
TL;DR
This study reveals for the first time the complete molecular mechanism by which ZCCHC4-mediated UHRF1 m6A methylation promotes OS progression through epigenetic suppression of CDO1 transcription and inhibition of ferroptosis.
Abstract
Background
Osteosarcoma (OS) represents a common primary malignant bone tumor associated with unfavorable clinical outcomes. Growing evidence underscores the crucial involvement of N6-methyladenosine (m6A) modifications in tumor development, but the specific mechanisms underlying the m6A regulatory network in OS remain to be elucidated.
Methods
Potential key target genes in OS were identified through bioinformatic analyses, followed by the characterization of m6A-related regulatory proteins, specifically, writer and reader proteins, which showed significant associations with these targets. To elucidate the mechanistic role of m6A methylation in regulating UHRF1 expression, a series of in vitro assays were conducted. These included RNA pull-down, MeRIP-PCR, dot blot, dual-luciferase reporter assays, and RNA stability assays, which collectively confirmed the interaction between m6A regulatory proteins and UHRF1 mRNA. For functional investigations, OS cell lines (U2OS, Saos2, and 143B) with gene silencing or overexpression were established, and the role of UHRF1 in cellular proliferation, migration, and invasion was assessed using CCK-8 assays, Transwell migration and invasion assays, flow cytometry, and wound healing assays. In addition, GSH/GSSG ratio, Fe2+ concentration, and ROS levels were measured using commercial assay kits to explore ferroptosis-related functional mechanisms. To validate the in vivo relevance of our findings, a xenograft mouse model was established. Finally, functional rescue experiments were performed to mechanistically confirm the critical role of the ZCCHC4-UHRF1-CDO1 regulatory axis in OS progression.
Results
ZCCHC4, functioning as an m6A methyltransferase, enhances the stability of UHRF1 mRNA by catalyzing its m6A modification, thereby promoting increased expression of UHRF1. In parallel, IGF2BP3, an established m6A reader protein, specifically recognizes and binds to the m6A-modified sites on UHRF1 mRNA, further stabilizing the transcript and modulating its downstream biological functions. METTL3/METTL14 knockdown experiments ruled out the contribution of classical m6A methyltransferases, confirming that ZCCHC4 is the primary methyltransferase for UHRF1. Dual-luciferase assays and bisulfite sequencing revealed that UHRF1 suppresses CDO1 transcription by inducing high methylation of its promoter, thereby reducing ROS/Fe2+ levels and increasing GSH, which in turn blocks ferroptosis. In U2OS, Saos2, and 143B cells, silencing UHRF1 or ZCCHC4 inhibited proliferation, migration, and invasion while activating ferroptosis. Overexpression of UHRF1 had the opposite effect. In vivo models confirmed that UHRF1 silencing inhibited tumor growth. Furthermore, UHRF1 overexpression partially reversed the phenotypes induced by ZCCHC4 knockdown.
Conclusion
In summary, this study reveals for the first time the complete molecular mechanism by which ZCCHC4-mediated UHRF1 m6A methylation promotes OS progression through epigenetic suppression of CDO1 transcription and inhibition of ferroptosis. This regulatory axis (ZCCHC4-IGF2BP3-UHRF1-CDO1-ferroptosis) provides multiple therapeutic targets for OS and lays a solid foundation for the future development of anticancer strategies based on the regulation of ferroptosis, while also offering a promising pathway for clinical translation.