Among these enzymes is the deubiquitinase Usp9X, which has been demonstrated to be overexpressed in various malignant tumors, including breast cancer, lung carcinoma, prostatic carcinoma, colon carcinoma, multiple myeloma, acute lymphoblastic leukemia and follicular and diffuse large B-cell lymphoma [5–9]. Here, USP9X is linked to AL amyloidosis.