Overexpression of membrane glucose transporters belonging to GLUT family, is a common feature of different malignancies. It has been found that the level of expression of some members of this large family correlates with invasiveness of some malignant tumors. GLUT1 is an example of the most often studied and best known members of GLUT receptors. We attempted to compare the expression level of GLUT1 gene in two breast cancer cell lines: hormone-positive MCF-7 and hormone-resistant, less differentiated and more aggressive MDA-MB-231.
A multiplex PCR (after RT) was performed in order to semiquantiatively compare differences in the expression of GLUT1 in both cell lines.
We found a difference in mRNA expression of GLUT1 in two cell lines. Densitometric optical analysis of bands resulted in the following results: in MCF-7 for GLUT1: 0.624; and in MDA-MB-231 0.875.
In our studies we showed differences in GLUT1 receptor mRNA expression in two breast cancer cell lines with higher expression in MDA-MB-231. The results show that invasiveness of cancer cells may be to some extent associated with the expression of glucose transporters, including GLUT1.
"The ascitic fluid in which AS-30D grow has a micromolar concentration of glucose (Rodríguez-Enríquez et al., 2000) making necessary to have a high affinity glucose transporter, whereas HeLa cells are cultured in a medium with a high glucose content of 25 mM, thus, only requiring a low affinity glucose transporter. GLUT1 and GLUT3 over-expression has also been detected in other cancer cells (HeLa hybrids CGL4, choriocarcinoma Jar, A431, MDA-MB, CaCo-2, MCF-7) (Clarson et al., 1997; Suzuki et al., 1999; Laudanski et al., 2003). Although the other GLUT isoforms were also expressed (Fig. 3), the kinetic analysis clearly showed the prevalence of one isoform on activity. "
[Show abstract][Hide abstract] ABSTRACT: Metabolic control analysis of tumor glycolysis has indicated that hexokinase (HK) and glucose transporter (GLUT) exert the main flux control (71%). To understand why they are the main controlling steps, the GLUT and HK kinetics and the contents of GLUT1, GLUT2, GLUT3, GLUT4, HKI, and HKII were analyzed in rat hepatocarcinoma AS-30D and HeLa human cervix cancer. An improved protocol to determine the kinetic parameters of GLUT was developed with D-[2-(3)H-glucose] as physiological substrate. Kinetic analysis revealed two components at low- and high-glucose concentrations in both tumor cells. At low glucose and 37 degrees C, the V(max) was 55 +/- 20 and 17.2 +/- 6 nmol (min x mg protein)(-1), whereas the K(m) was 0.52 +/- 0.7 and 9.3 +/- 3 mM for hepatoma and HeLa cells, respectively. GLUT activity was partially inhibited by cytochalasin B (IC(50) = 0.44 +/- 0.1; K(i) = 0.3 +/- 0.1 microM) and phloretin (IC(50) = 8.7 microM) in AS-30D hepatocarcinoma. At physiological glucose, GLUT1 and GLUT3 were the predominant active isoforms in HeLa cells and AS-30D cells, respectively. HK activity in HeLa cells was much lower (60 mU/mg protein) than that in AS-30D cells (700 mU/mg protein), but both HKs were strongly inhibited by G6P. HKII was the predominant isoform in AS-30D carcinoma and HeLa cells. The much lower GLUT V(max) and catalytic efficiency (V(max)/K(m)) values in comparison to those of G6P-sensitive HK suggested the transporter exerts higher control on the glycolytic flux than HK in cancer cells. Thus, GLUT seems a more adequate therapeutic target.
[Show abstract][Hide abstract] ABSTRACT: Breast cancers increase glucose uptake by increasing expression of the facilitative glucose transporters (GLUTs), mainly GLUT1. However, little is known about the relationship between GLUT1 expression and malignant potential in breast cancer. In this study, expression and subcellular localization of GLUT1 was analysed in vivo in breast cancer tissue specimens with differing malignant potential, based on the Scarff-Bloom-Richardson (SBRI, II, III) histological grading system, and in vitro in the breast cancer cell lines, MDA-MB-468 and MCF-7, and in MDA-MB-468 cells grown as xenografts in nude athymic BALB/c male mice. In situ hybridization analyses demonstrated similar levels of GLUT1 mRNA expression in tissue sections from breast cancers of all histological grades. However, GLUT1 protein was expressed at higher levels in grade SBRII cancer, compared with SBRI and SBRIII, and associated with the expression of the proliferation marker PCNA. Immunolocalization analyses in SBRII cancers demonstrated a preferential localization of GLUT1 to the portions of the cellular membrane that faced neighbouring cells and formed 'canaliculi-like structures', that we hypothesize could have a potential role as 'nutritional channels'. A similar pattern of GLUT1 localization was observed in confluent cultures of MDA-MB-468 and MCF-7, and in MDA-MB-468 cells grown as xenografts, but not in the normal breast epithelial cell line HMEC. However, no relationship between GLUT1 expression and malignant potential of human breast cancer was observed. Preferential subcellular localization of GLUT1 could represent a physiological adaptation of a subset of breast cancer cells that form infiltrative tumours with a nodular growth pattern and that therefore need a major diffusion of glucose from blood vessels.
Journal of Cellular and Molecular Medicine 11/2008; 13(9B):3973-84. DOI:10.1111/j.1582-4934.2008.00544.x · 4.01 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Several clinical studies have shown low or no expression of GLUT1 in breast cancer patients, which may account for the low clinical specificity and sensitivity of 2-deoxy-2-[18F]fluoro-d-glucose ([18F]FDG) used in positron emission tomography (PET). Therefore, it has been proposed that other tumor characteristics such as the high expression of GLUT2 and GLUT5 in many breast tumors could be used to develop alternative strategies to detect breast cancer. Here we have studied the in vitro and in vivo radiopharmacological profile of 6-deoxy-6-[18F]fluoro-d-fructose (6-[18F]FDF) as a potential PET radiotracer to image GLUT5 expression in breast cancers.
Nuclear Medicine and Biology 05/2011; 38(4):461-75. DOI:10.1016/j.nucmedbio.2010.11.004 · 2.41 Impact Factor
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