The two out of 17 human cancer cell lines JAR and U251, positive for tktl1 mRNA and TKTL1 protein by immunohistochemistry and Western blot for at least one antibody showed neither an outstanding production of lactic acid nor increased resistance against the chemotherapeutic drugs paclitaxel and cisplatin or to ionizing radiation, respectively, compared to the other cell lines. The gene discussed is TKTL1; the disease is cancer.