These indicate that Ink4a loss leads to a more aggressive phenotype and poor clinical outcome of MPM.84 Immunohistochemistry of the murine mesotheliomas identified the epithelioid MPM phenotype in the CKO mice Nf2;p53 and Nf2;Ink4a/Arf mice, but not in Nf2;p53;Ink4a* mice. The gene discussed is TP53; the disease is mesothelioma.