The establishment of the novel mouse mesothelioma cell line RN5 originated from a heterozygote Nf2+/− mouse on a C57Bl/6J background is expected to be useful also for in vivo investigations on (1) the modulation of tumor growth by decreased merlin levels (possibly linked to loss of heterozygosity), (2) the role of the immune system in asbestos-mediated mesothelioma development, and (3) the role of other stromal components in tumorigenesis. The gene discussed is NF2; the disease is mesothelioma.