Some groups have associated the 3R/3R genotype with higher TS mRNA expression compared to 2R/2R or 2R/3R genotypes[17]; others found no such relationship, but did find that cancer tissues with the 3R/3R genotype had higher expression of TS protein than those with the 2R/3R genotype.[42] These results, together our observations, suggest that TS genotyping, without determination of TS mRNA and protein expression levels, may be insufficient to predict patient responses to 5-FU-based chemotherapy. Here, TYMS is linked to cancer.