In addition, structures of riboflavin biosynthesis reductases were shown to be very similar to dihydrofolate reductases [7], [8], [9], and inhibitors of dihydrofolate reductases such as methotrexate, pyrimethamine, and trimethoprim, have long been used clinically in the treatment of cancer and bacterial and fungal infections [10]. Here, DHFR is linked to cancer.