ΔNp63α promotes Bortezomib resistance via the CYGB-ROS axis in head and neck squamous cell carcinoma

Bortezomib, a proteasome inhibitor, proved potent in the treatment of recurrent multiple myeloma or mantle cell lymphoma. However, slow progress was made when it was applied to treat solid tumors. We discovered that different head and neck squamous cell carcinoma (HNSCC) cell lines had significantly different sensitivities to bortezomib, and also demonstrated that individual relatively sensitive HNSCC cell lines had fewer Delta Np63 alpha expressions. Based on these findings, we speculated that Delta Np63 alpha may be a key factor in the resistance of HNSCC cells to bortezomib. Delta Np63 alpha knockdown made HNSCC more sensitive to bortezomib, while Delta Np63 alpha overexpression made it more resistant. RNA sequencing (RNA-seq) analysis of Delta Np63 alpha-knockdown cells revealed clear alterations in the subset of genes that were associated with oxidative stress and antioxidant defense. The gene CYGB was downregulated significantly. CHIP-seq detection showed that CYGB was the transcriptional regulatory site of Delta Np63 alpha. CHIP-PCR showed evidence of Delta Np63 alpha binding. The detection of the dual-luciferase reporter gene demonstrated that Delta Np63 alpha significantly enhanced the CYGB promoter activity. Furthermore, we confirmed that CYGB plays a role in clearing excess ROS induced by bortezomib to inhibit HNSCC apoptosis. Consequently, Delta Np63 alpha regulated the expression of CYGB in HNSCC. CYGB was the target of transcription regulation of Delta Np63 alpha. It reduced apoptosis by clearing excess ROS produced by bortezomib, and thus exerted drug resistance.