USP22 and cancer: While recent TCGA data reveal that deep/shallow USP22 deletions are more prevalent than gain/amplification and that USP22 expression is frequently reduced at the mRNA level in most cancer types [68,69,84], increased USP22 expression has also been reported in multiple cancers and USP22 has traditionally been investigated as an oncogene [85,86,87,88,89,90,91,92].