TYMS and breast cancer: TYMS catalyses the methylation of dUMP to dTMP, and is a target for the chemotherapy drug 5-FU, one of the most commonly used drugs to treat cancer, including breast cancer.44 Notably, it has been found that YES1 and TYMS are usually co-amplified and consequently co-overexpressed in cancer,43,45 findings similar to those of this study.