Serum ELISA of antibody subtypes from AID-Cre-YFP KrasG12DArf −/−, AID-Cre-YFP KrasG12DArf +/−, and control AID-Cre-YFP Arf −/− also showed small but significant changes between baseline and 12 weeks in IgM and IgG isosubtypes (Figure S4B), perhaps related to infected, fungating papillomas in these mice. This evidence concerns the gene CDKN2A and papilloma.