AL398, A Novel NSUN6 Inhibitor, Attenuates Epithelial-Mesenchymal Transition and Metastasis in Endometrial Cancer by...

Endometrial cancer (EC) constitutes a leading gynecologic malignancy for which advanced or metastatic disease presents limited therapeutic options. While RNA modifications are acknowledged as key regulatory elements in cancer, the role of 5-methylcytosine (m⁵C) and its modifying enzymes in EC is still largely unstudied. Here, it demonstrates that the m⁵C methyltransferase NSUN6 is significantly upregulated in EC tissues, and its expression correlates with higher tumor grade and unfavorable prognosis. Functional studies employing gain- and loss-of-function models revealed that NSUN6 specifically enhances EC cell migration and invasion both in vitro and in vivo, without altering proliferation or apoptosis. Mechanistically, NSUN6 drives EMT by catalyzing m⁵C modification on Snail mRNA, which in turn stabilizes the transcript of this key EMT transcription factor. AL398 was identified through structure-based virtual screening as a novel small-molecule inhibitor that binds potently to the NSUN6 active site and suppresses its methyltransferase activity. Treatment with AL398 effectively inhibited the NSUN6/m⁵C/Snail axis, reversed the EMT phenotype, and attenuated EC cell migration, invasion, and metastasis in preclinical models. Collectively, it both validates the NSUN6/m⁵C/Snail axis as a critical EC vulnerability and provides a proof-of-concept inhibitor, AL398, laying the groundwork for the development of first-in-class RNA methylation-targeted therapies against metastatic EC.