Nuclear miR-451a activates KDM7A and leads to cetuximab resistance in head and neck squamous cell carcinoma.

Cetuximab resistance has been a major challenge for head and neck squamous cell carcinoma (HNSCC) patients receiving targeted therapy. However, the mechanism that causes cetuximab resistance, especially microRNA (miRNA) regulation, remains unclear. Growing evidence suggests that miRNAs may act as "nuclear activating miRNAs" for targeting promoter regions or enhancers related to target genes. This study elucidates a novel mechanism underlying cetuximab resistance in HNSCC involving the nuclear activation of KDM7A transcription via miR-451a. Herein, small RNA sequencing, quantitative real-time polymerase chain reaction (qRT‒PCR) and fluorescence in situ hybridization (FISH) results provided compelling evidence of miR-451a nuclear enrichment in response to cetuximab treatment. Chromatin isolation via RNA purification, microarray analysis, and bioinformatic analysis revealed that miR-451a interacts with an enhancer region in KDM7A, activating its expression and further facilitating cetuximab resistance. It has also been demonstrated that the activation of KDM7A by nuclear miR-451a is induced by cetuximab treatment and is AGO2 dependent. Logistic regression analyses of 87 HNSCC samples indicated the significance of miR-451a and KDM7A in the development of cetuximab resistance. These discoveries support the potential of miR-451a and KDM7A as valuable biomarkers for cetuximab resistance and emphasize the function of nuclear-activating miRNAs.