The invention discloses a method of treating, preventing or ameliorating tumor or symptoms resulting from defective neurofibromatosis type-2 gene in a subject by administering to the subject a therapeutically effective amount of a ubiquitin-proteasome system inhibitor which inhibits or slows the growth of neurofibromatosis type-2-deficient tumor or associated symptoms. The invention also includes methods of diagnosis and screening of patients for neurofibromatosis type-2 and mesothelioma.
