Recognizing that all FDA-approved antifolates enter cells via the RFC that is expressed in virtually all human cell types, and that FRα is expressed primarily on cancer cells with little-or-no expression on other human cell types except the proximal tubule cells of the kidneys, Jackman designed a new antifolate BTG945 that is transported into cells almost exclusively via FRα. This evidence concerns the gene FOLR1 and cancer.