Knockdown of the mitochondrial thymidine kinase TK2 via siRNA increased the capacity of TS siRNA to sensitize cervical carcinoma cancer cells as well as breast epithelial adenocarcinoma cancer cells towards the active metabolite 5-fluorodeoxyuridine (5FUdR) of the traditional anti-cancer agent 5-FU. The gene discussed is TYMS; the disease is cancer.