The invention is in the field of medicine and molecular therapeutics. The invention provides means and measures for diagnosis and treatment, in particular for diagnosis and treatment of tumors, more in particular for determining the level of hypoxia in a tumor and for reducing the risk of metastasis of a tumor in a subject. The invention comprises a method wherein a level of exosome-associated GABARAPL1 is determined in a bodily fluid of the subject and wherein an elevated level of exosome-associated GABARAPL1 is indicative of an increased level of hypoxia of the tumor. The invention also comprises an antibody directed against GABARAPL1 for use in the treatment or prevention of cancer.
