PRDM2 and Anaplastic (Malignant) Meningioma: Consistent with its antineoplastic effects, Riz1 knockout mice develop a variety of tumors and Riz1 is frequently lost, silenced or mutated in different human cancers including breast, liver and colon cancers and also in neuroblastoma, melanoma, osteosarcoma and malignant meningiomas (18–22).