m⁶A-modified circMELK regulates nasopharyngeal carcinoma progression via a YTHDF1/circMELK-miR-4775-HMGA2 feedback loop.

BACKGROUND: Circular RNAs (circRNAs) are emerging regulators in tumor biology. However, their roles in nasopharyngeal carcinoma (NPC) remain poorly defined.

METHODS: By analyzing GSE190271, we identified hsa_circ_0138742 (circMELK) as significantly upregulated in NPC. Functional assays in vitro and in vivo were performed to explore its biological role. Mechanistic studies included RIP, ChIP, RNA pull-down, dual-luciferase assays, and rescue experiments.

RESULTS: circMELK was markedly elevated in NPC tissues and cells. Silencing circMELK inhibited NPC cell proliferation, migration, and invasion, while overexpression enhanced these malignant traits. Mechanistically, YTHDF1-mediated m6A modification serves as a key determinant for the cytoplasmic export of circMELK. There, circMELK acts as a ceRNA for miR-4775, relieving suppression of HMGA2. Elevated HMGA2 upregulates YTHDF1 by transcriptional activation, forming a YTHDF1/circMELK-miR-4775-HMGA2 positive feedback loop that drives epithelial-mesenchymal transition (EMT) and promotes metastasis.

CONCLUSION: circMELK promotes NPC progression via a novel m6A-dependent ceRNA regulatory loop. Targeting this axis may offer new therapeutic opportunities.