FOXM1 influences DNA methylation to augment TACC3 alternative splicing directed by KAT2A in hepatocellular carcinoma

BACKGROUND/AIMS: Hepatocellular carcinoma (HCC) is characterized by profound transcriptomic dysregulation, yet the mechanism(s) by which DNA methylation is coordinated with chromatin modifications to regulate alternative splicing during tumorigenesis remains poorly understood. METHODS: Using prospectively paired multi-omics data obtained from metabolic dysfunction-associated steatotic liver disease (MASLD)-HCC patients and coupled with a premalignant MASLD cohort, we have uncovered a previously unrecognized gene-regulatory axis centered on TACC3 isoform-switching. RESULTS: In the non-tumoral context, the TACC3-201 isoform directly engages the histone acetyltransferase KAT2A to coordinate the regulation of NOTCH4 signaling. In HCC, this regulatory axis is disrupted whereby FOXM1 overrides DNMT1-mediated methylation, upregulating TACC3, and decoupling TACC3 from the KAT2A-associated NOTCH4 co-expression module. This rewiring is licensing tumor-specific cell-cycle progression and epigenetic plasticity. Thus, FOXM1 reshapes the TACC3-KAT2A interaction, while DNMT1 drives context-dependent DNA methylation, activating the CDK1-inhibitory kinase PKMYT1. CONCLUSIONS: We uncovered TACC3-KAT2A as an emerging regulatory axis caused by alternative splicing in HCC and propose FOXM1-driven TACC3 inhibition to synergistically disrupt mitotic fidelity and transcriptional regulation, potentially offering new therapeutic avenues for HCC with reduced toxicity to the normal liver.