PSME4 and hepatocellular carcinoma: Recently, PA200 has been shown to be highly expressed in non-small cell lung cancer (NSCLC), hepatocellular carcinoma, multiple myeloma, gastric cancer, esophageal squamous cell carcinoma, esophageal adenocarcinoma, oral squamous cell carcinoma (OSCC), and lung cancer [2,88,89,90,91,92,93,94,95].