title: Nutrient transporters in cancer: relevance to Warburg hypothesis and beyond.
abstract: Tumor cells have an increased demand for nutrients; this demand is met by increased availability of nutrients through vasculogenesis and by enhanced cellular entry of nutrients through upregulation of specific transporters. This review focuses on three groups of nutrient transporters relevant to cancer: glucose transporters, lactate transporters, and amino acid transporters. Tumor cells enhance glucose uptake via induction of GLUT1 and SGLT1, and coordinate the increased entry of glucose with increased glycolysis. Since enhanced glycolysis in cancer is associated with lactate production, tumor cells must find a way to eliminate lactic acid to prevent cellular acidification. This is achieved by the upregulation of MCT4, a H+-coupled lactate transporter. In addition, the Na+-coupled lactate transporter SMCT1 is silenced in cancer. SMCT1 also transports butyrate and pyruvate, which are inhibitors of histone deacetylases. The silencing of SMCT1 occurs in cancers of a variety of tissues. Re-expression of SMCT1 in cancer cell lines leads to growth arrest and apoptosis in the presence of butyrate or pyruvate, suggesting that the transporter may function as a tumor suppressor. Tumor cells meet their amino acid demands by inducing xCT/4F2hc, LAT1/4F2hc, ASCT2, and ATB0,+. xCT/4F2hc is related primarily to glutathione status, protection against oxidative stress, and cell cycle progression, whereas the other three transporters are related to amino acid nutrition. Pharmacologic blockade of LAT1/4F2hc, xCT/4F2hc, or ATB0,+ leads to inhibition of cancer cell growth. Since tumor cells selectively regulate these nutrient transporters to support their rapid growth, these transporters have potential as drug targets for cancer therapy.
authors.affiliation: Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, USA. vganapat@mcg.edu
authors.forename: Vadivel
authors.initials: V
authors.lastname: Ganapathy
authors.forename: Muthusamy
authors.initials: M
authors.lastname: Thangaraju
authors.forename: Puttur D
authors.initials: PD
authors.lastname: Prasad
mesh_terms: D026905:Amino Acid Transport Systems / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D027682:Cation Transport Proteins / Q000378:metabolism / Q000502:physiology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D004734:Energy Metabolism; D005947:Glucose / Q000378:metabolism*; D051246:Glucose Transport Proteins, Facilitative / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D019344:Lactic Acid / Q000096:biosynthesis; D008954:Models, Biological; D027501:Monocarboxylic Acid Transporters / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D009369:Neoplasms / Q000188:drug therapy / Q000503:physiopathology*
chemical_list: D026905:Amino Acid Transport Systems; D027682:Cation Transport Proteins; D051246:Glucose Transport Proteins, Facilitative; D027501:Monocarboxylic Acid Transporters; C476760:SLC5A8 protein, human; D019344:Lactic Acid; D005947:Glucose