Surprisingly, the PCR product of SLC19A1 was not detected at all in A549/PEM cells, whereas there was no marked difference in the PCR product of FOLR1. We next examined whether A549/PEM cells have resistance to fluorouracil, another antifolate drug, and other types of anti-cancer drugs, namely docetaxel and gemcitabine. This evidence concerns the gene FOLR1 and cancer.