It has previously been found that LMP2 generally is down-regulated in several types of tumours such as laryngeal squamous cell carcinoma [31], head and neck squamous cell carcinoma [32], renal cell carcinoma [33], as well as in a number of tumour cell lines including small-cell lung carcinoma, hepatocellular carcinoma, colon adenocarcinoma and basophilic leukemia [34]. Here, PSMB9 is linked to head and neck squamous cell carcinoma.