PSME1 and plasma cell myeloma: Thus, PSME1 has been identified as tumor-associated protein/putative tumor biomarker/upregulated in human esophageal squamous cell carcinoma (hESCC) [69], primary and metastatic human prostate cancer (PCa) [70], skin cutaneous melanoma (SKCM) [71], and multiple myeloma (MM) [72], while it was reported as downregulated in hepatitis B virus-infected well-differentiated hepatocellular carcinoma (HCC) [74].