 For example, of the 100 primary breast carcinomas, approximately 41% have p14ARF defects.In a separate study, 32% of colorectal adenomas (non-cancerous tumors) were found to have p14ARF inactivation due to hypermethylation of the promoter.Mouse models lacking p19Arf, p53, and Mdm2 are more prone to tumor development than mice without Mdm2 and p53, alone.