Abstract

Simple SummaryThis study identifies IGF2BP3 as the sole m6A reader dynamically regulated upon CDK4/6 inhibition in bladder cancer, where its high expression correlates with poor prognosis and increased proliferation. Mechanistically, IGF2BP3 stabilizes m6A-modified MYC transcripts to sustain G1/S progression and attenuate palbociclib-induced cytostasis, establishing a functional IGF2BP3–MYC axis that drives drug tolerance. The E3 ubiquitin ligase MKRN2 directly binds, ubiquitinates, and promotes proteasomal degradation of IGF2BP3, thereby limiting MYC expression and cell-cycle progression. MKRN2 overexpression synergizes with palbociclib to suppress tumor growth, reduce MYC/Ki67 expression, and induce apoptosis in vivo, effectively overcoming IGF2BP3-mediated resistance. Collectively, the MKRN2–IGF2BP3–MYC axis represents a novel post-translational mechanism modulating CDK4/6 inhibitor sensitivity, providing a rationale for biomarker-guided stratification and combination therapies targeting this pathway in bladder cancer.Background: CDK4/6 inhibitors induce G1/S cell-cycle arrest in bladder cancer; however, adaptive resistance limits their therapeutic efficacy. The role of the m6A reader IGF2BP3 in regulating sensitivity to CDK4/6 inhibition remains largely unknown. Methods: Transcriptomic profiling was performed in palbociclib-treated bladder cancer cell lines (T24, RT112, and UMUC-3) to identify m6A regulators associated with drug response. The expression and clinical significance ofIGF2BP3were evaluated using The Cancer Genome Atlas (TCGA) data and an independent clinical cohort. Gain- and loss-of-function assays were conducted to investigate the effects of IGF2BP3 on cell proliferation and cell-cycle progression. Mechanistic studies, including RNA-binding, mRNA stability, ubiquitination, and in vivo tumorigenesis assays, were performed to elucidate the underlying regulatory network. Results: IGF2BP3 was identified as the only m6A regulator differentially expres