Hypoxia is a feature of most tumours, albeit with variable incidence and severity within a given patient population. It is a negative prognostic and predictive factor owing to its multiple contributions to chemoresistance, radioresistance, angiogenesis, vasculogenesis, invasiveness, metastasis, resistance to cell death, altered metabolism and genomic instability. Given its central role in tumour progression and resistance to therapy, tumour hypoxia might well be considered the best validated target that has yet to be exploited in oncology. However, despite an explosion of information on hypoxia, there are still major questions to be addressed if the long-standing goal of exploiting tumour hypoxia is to be realized. Here, we review the two main approaches, namely bioreductive prodrugs and inhibitors of molecular targets upon which hypoxic cell survival depends. We address the particular challenges and opportunities these overlapping strategies present, and discuss the central importance of emerging diagnostic tools for patient stratification in targeting hypoxia.

Targeting hypoxia in cancer therapy

ESPEN guidelines on nutrition in cancer patients

The National Cholesterol Education Program’s Adult Treatment Panel III (ATP III) report [1] added the metabolic syndrome, a multidimensional risk factor for cardiovascular disease (CVD), as a coequal partner of elevated low-density lipoprotein (LDL) cholesterol for risk-reduction therapies. Interest in the metabolic syndrome has increased greatly since the publication of the ATP III report. There are several aspects to the metabolic syndrome that deserve consideration for clinical practice: 1) major clinical outcomes, 2) metabolic components, 3) pathogenesis, 4) clinical criteria for diagnosis, 5) risk for clinical outcomes, and 6) therapeutic interventions.

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(05)66378-7.pdf

The Metabolic Syndrome

https://www.cell.com/cancer-cell/pdf/S1535-6108(09)00087-7.pdf

Hypoxia-Inducible Factors Regulate Tumorigenic Capacity of Glioma Stem Cells

Genetic events in cancer activate signalling pathways that alter cell metabolism. Clinical evidence has linked cell metabolism with cancer outcomes. Together, these observations have raised interest in targeting metabolic enzymes for cancer therapy, but they have also raised concerns that these therapies would have unacceptable effects on normal cells. However, some of the first cancer therapies that were developed target the specific metabolic needs of cancer cells and remain effective agents in the clinic today. Research into how changes in cell metabolism promote tumour growth has accelerated in recent years. This has refocused efforts to target metabolic dependencies of cancer cells as a selective anticancer strategy.

/pdf/targeting-cancer-metabolism-a-therapeutic-window-opens-4eayk4wjss.pdf

Targeting cancer metabolism: a therapeutic window opens

Malignant cells are known to have accelerated metabolism, high glucose requirements, and increased glucose uptake. Transport of glucose across the plasma membrane of mammalian cells is the first rate-limiting step for glucose metabolism and is mediated by facilitative glucose transporter (GLUT) proteins. Increased glucose transport in malignant cells has been associated with increased and deregulated expression of glucose transporter proteins, with overexpression of GLUT1 and/or GLUT3 a characteristic feature. Oncogenic transformation of cultured mammalian cells causes a rapid increase of glucose transport and GLUT1 expression via interaction with GLUT1 promoter enhancer elements. In human studies, high levels of GLUT1 expression in tumors have been associated with poor survival. Studies indicate that glucose transport in breast cancer is not fully explained by GLUT1 or GLUT3 expression, suggesting involvement of another glucose transporter. Recently, a novel glucose transporter protein, GLUT12, has been found in breast and prostate cancers. In human breast and prostate tumors and cultured cells, GLUT12 is located intracellularly and at the cell surface. Trafficking of GLUT12 to the plasma membrane could therefore contribute to glucose uptake. Several factors have been implicated in the regulation of glucose transporter expression in breast cancer. Hypoxia can increase GLUT1 levels and glucose uptake. Estradiol and epidermal growth factor, both of which can play a role in breast cancer cell growth, increase glucose consumption. Estradiol and epidermal growth factor also increase GLUT12 protein levels in cultured breast cancer cells. Targeting GLUT12 could provide novel methods for detection and treatment of breast and prostate cancer.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/jcp.20166

Molecular and cellular regulation of glucose transporter (GLUT) proteins in cancer

Facilitative glucose transporters exhibit variable hexose affinity and tissue-specific expression. These characteristics contribute to specialized metabolic properties of cells. Here we describe th...

https://www.physiology.org/doi/pdf/10.1152/ajpendo.2002.282.3.E733

Identification of a novel glucose transporter-like protein-GLUT-12.

Glucose plays a major role in mammary gland function during lactation as it is used both as a fuel and as a precursor of milk components. In rats, previous studies have shown that the facilitative glucose transporter GLUT1 is expressed in mammary epithelial cells. We have used confocal immunofluorescence to localise GLUT1 and GLUT12, a recently identified member of the sugar transporter family, in pregnant and lactating rat mammary gland. GLUT12 staining was observed in the cytoplasm of mammary epithelial cells at day 20 of pregnancy, and at 1 and 6 days postpartum. Furthermore, GLUT12 staining was present at the apical plasma membrane of epithelial cells during lactation. In contrast, GLUT1 protein localised to the cytoplasm and basolateral surface of mammary epithelial cells. Forced weaning resulted in decreased cytoplasmic GLUT1 staining intensity, but no change in GLUT12 staining. The results suggest a possible role for GLUT12 in the metabolism of mammary epithelial cells during pregnancy and lactation.

Expression and localisation of GLUT1 and GLUT12 glucose transporters in the pregnant and lactating rat mammary gland.

Glucose is an essential molecule for most mammalian cells, and is particularly important during fetal development, when cells are rapidly dividing and differentiating. In rats, GLUT1 is present at high levels in most fetal tissues, with levels decreasing after birth. We used immunohistochemistry to localise GLUT12 protein, a recently identified member of the sugar transporter family, and GLUT1 during rat fetal development. GLUT12 staining was observed in heart muscle from gestational days 15 to 21. GLUT12 staining in skeletal muscle increased from gestational days 17 to 21, and GLUT12 was also detected in brown adipose tissue. The expression of GLUT12 in insulin-responsive tissues supports a potential role for GLUT12 in the provision of glucose to these tissues before the appearance of GLUT4. GLUT12 protein was also expressed in fetal chondrocytes from gestational day 15 onward, in kidney distal tubules and collecting ducts from day 19, and in lung bronchioles from day 19. The specific pattern of expression observed in the rat fetus suggests that GLUT12 may be important in hexose delivery to developing tissues.

https://link.springer.com/content/pdf/10.1007%2Fs00429-002-0303-4.pdf

Expression during rat fetal development of GLUT12 – a member of the class III hexose transporter family

/pdf/expression-during-rat-fetal-development-of-glut12-a-member-4anfekgq4g.pdf

Maria L. Macheda

Papers

Molecular and cellular regulation of glucose transporter (GLUT) proteins in cancer

Identification of a novel glucose transporter-like protein-GLUT-12.

Expression and localisation of GLUT1 and GLUT12 glucose transporters in the pregnant and lactating rat mammary gland.

Expression during rat fetal development of GLUT12 – a member of the class III hexose transporter family

Expression during rat fetal development of GLUT12 – a member of the class III hexose transporter family