The invention relates to the use of the ubiquitous vertebrate glucose transporter GLUT1, or of fragments or sequences derived thereof, for the in vitro diagnosis of cancers, when used as a tumor marker, or for the screening of compounds useful for the preparation of drugs for the prevention or the treatment of pathologies linked to an infection of an individual with a PTLV, or pathologies linked to an overexpression of GLUT1 on cell surfaces, or the in vitro detection of GLUT1 on cell surfaces. The invention also relates to pharmaceutical compositions containing GLUT1, or fragments or sequences derived thereof, and to their uses such as in the frame of the prevention or the treatment of pathologies linked to an infection of an individual with a PTLV.