Polymorphisms in genes encoding the iP subunits β1i (PSBM9) and β5i (PSMB8) have been associated with an increased risk of tumor development, including the development of esophageal carcinoma [115], cervical carcinoma [116], oral squamous cell carcinoma [81,117], prostate cancer [118], and colon cancer [119]. This evidence concerns the gene PSMB8 and neoplasm.