RRAS and skin neoplasm: To investigate the role of R-Ras in skin tumour formation, we treated the back skin of adult mice deficient for R-ras gene expression (R-Ras KO10,) and wild-type mice (WT, as control) once with a local application of the mutagen DMBA, and then repeatedly with the growth-promoting histone deacetylase inhibitor TPA, twice weekly for a period of 19 weeks.