FBXO4 and papilloma: IHC revealed elevated Fxr1 in normal tissues from Fbxo4−/− and + /− mice relative to that in Fbxo4 + / + mice; an obvious elevation of Fxr1 was noted in papilloma of Fbxo4 + /− and −/− mice compared to that in + / + mice (Fig. 5c–e).