Glucose is fundamental to the metabolism of mammalian cells. Several glucose transporter protein (Glut) isoforms have been identified and shown to function in response to insulin and IGF-1 induced signaling. GLUT- 1 is detectable in many human tissues including those of the colon, lung, stomach, esophagus, and breast. GLUT-1 immunoreactivity in some cancers, including transitional cell carcinoma of the urinary bladder, has been associated with aggressive behavior.