As for RRM1, an inverse correlation between RRM1 mRNA and protein levels was found: tissue samples from pancreatic cancer biopsies of the nude mice with higher levels of RRM1 mRNA (mice treated with gemcitabine, fasting or fasting plus gemcitabine treatment) displayed lower levels of the protein (Figure 7B), suggesting the existence of a post-transcriptional feedback mechanism within xenograft tumor between mRNA and protein levels of RRM1. This evidence concerns the gene RRM1 and familial pancreatic carcinoma.