Nuclear miR-451a activates KDM7A and leads to cetuximab resistance in head and neck squamous cell carcinoma [miRNA-Seq]

Cetuximab resistance has been a major challenge for head and neck squamous cell carcinoma (HNSCC) during target therapy. Yet the mechanism that caused cetuximab resistance, especially the miRNA regulation therein remains unclear. With growing evidence suggests that miRNAs may function within the cell nucleus and act as “nuclear activating miRNAs” for targeting the promoter region or enhancers related to target genes. They are believed to regulate diseases development including tumorigenesis. 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, qRT-PCR and FISH results provide compelling evidence of miR-451a nuclear enrichment with cetuximab treatment. ChIRP-seq, microarray, bioinformatic analysis and dual luciferase reporter assay results show that miR-451a interacts with an enhancer region in KDM7A, activating its expression and further facilitating cetuximab resistance. It is also demonstrated that activation of KDM7A by nuclear miR-451a is induced by cetuximab treatment and is AGO2 dependent. Analyses of HNSCC samples through logistic regression indicated the significance of miR-451a and KDM7A in cetuximab resistance. These discoveries hold promise for the potential utilization of miR-451a and KDM7A as valuable biomarkers for cetuximab resistance and emphasize the function of nuclear activating miRNAs. Overall design: to investigate the differentially expressed miRNAs in cytoplasm and in nucleus in cetuximab resistant HNSCC cell compared to the sensitive HNSCC cell. We first cultivated cetuximab resistant CAL27 cells, and performed nucleus-cytoplasm seperation to each sample. Small RNA sequencing were performed on cytoplasmic, nuclear and total RNAs of CAL27 and its cetuximab resistant cell line.