Proliferation is associated with 2-deoxy-D-[1-3H]glucose uptake by T47D breast tumour and SW480 and SW620 colonic tumour cells

EGF receptor stimulation shifts breast cancer cell glucose metabolism toward glycolytic flux through PI3 kinase signaling

Breast cancers that express epidermal growth factor (EGF) receptors (EGFRs) are associated with poor prognosis. Our group recently showed in breast cancer patients that EGFR expression is strongly correlated with high tumor uptake of the glucose analogue, ¹⁸F-fluorodeoxyglucose (FDG). Here, we explored the cellular mechanism and signaling pathways that can explain the relation between EGFR and breast cancer cell glucose metabolism. FDG uptake, lactate production and hexokinase (HK) activity were measured, and proliferation assays and western blots were performed. EGF stimulated an increase of FDG uptake in EGFR-positive T47D and MDA-MB-468 cells, but not in MCF-7 cells. In T47D cells, the effect was dose-dependent and was accompanied by increased lactate production, indicating a shift toward glycolytic flux. This metabolic response occurred through enhanced HK activity and upregulated glucose transporter 1 (GLUT1) expression. EGFR stimulation also increased T47D cell proliferation. Blocking EGFR activation with BIBX1382 or gefitinib completely abolished both FDG uptake and proliferation effects. EGFR stimulation induced MAP kinase (MAPK) and PI3 kinase (PI3K) activation. Increased cell proliferation by EGFR stimulation was completely abolished by MAPK inhibition with PD98059 or by PI3K inhibition with LY294002. Increased FDG uptake was also completely abrogated by PI3K inhibition but was uninfluenced by MAPK inhibition. These findings suggest that the association between breast tumor EGFR expression and high FDG uptake might be contributed by stimulation of the PI3K pathway downstream of EGFR activation. This was in contrast to EGFR-mediated cell proliferation that required MAPK as well as PI3K signaling.

17beta-estradiol augments 18F-FDG uptake and glycolysis of T47D breast cancer cells via membrane-initiated rapid PI3K-Akt activation

Use of (18)F-FDG uptake as a surrogate marker of therapeutic response requires the recognition of biologic factors that influence cancer cell glucose metabolism. Estrogen is a potent stimulator of breast cancer proliferation, a process that requires sufficient energy, which is likely met by increased glycolysis. We thus explored the effect of estrogen on (18)F-FDG uptake in responsive breast cancer cells and investigated the mediating molecular mechanisms.

METHODS

T47D breast cancer cells were stimulated with 17β-estradiol (E(2)) or bovine serum albumin (BSA)-E(2) and measured for (18)F-FDG uptake, lactate release, and mitochondrial hexokinase activity. The effects of antiestrogens, cycloheximide, and major protein kinase inhibitors were investigated. Immunoblots were performed for membrane glucose transporter type 1, phosphorylated phosphatidylinositol 3-kinase (PI3K), and Akt.

RESULTS

E(2) augmented T47D cell (18)F-FDG uptake in a dose- and time-dependent manner that preceded and surpassed its proliferative effect. With exposure to 10 nM E(2), protein content-corrected (18)F-FDG uptake reached 172.7% ± 6.6% and 294.4% ± 9.5% of controls by 24 and 48 h, respectively. Lactate release reached 110.9% ± 7.3% and 145.2% ± 10.5% of controls at 24 and 48 h, and mitochondrial hexokinase activity increased to 187.1% ± 31.6% at 24 h. Membrane glucose transporter type 1 expression was unaltered. The effect was absent in estrogen receptor (ER)-negative breast cancer cells and was abrogated by ICI182780, indicating ER dependence. The E(2) effect was not blocked by tamoxifen and was mimicked by membrane-impermeable BSA-E(2), consistent with nongenomic membrane-initiated E(2) action. Inhibition by cycloheximide demonstrated the requirement of a new protein synthesis. Immunoblots displayed rapid phosphorylation of PI3K and Akt within minutes of E(2) treatment, and the specific PI3K inhibitors wortmannin and LY294002 abolished the ability of E(2) to elevate (18)F-FDG uptake.

CONCLUSION

Estrogen augments breast cancer cell (18)F-FDG uptake by stimulating glycolysis and hexokinase activity via membrane-initiated E(2) action that activates the PI3K-Akt pathway. These findings yield important insight into our understanding of the biology of breast cancer metabolism and may have potential implications for (18)F-FDG uptake as a surrogate marker of therapeutic response.

Comparison of cisplatin sensitivity and the 18F fluoro-2-deoxy 2 glucose uptake with proliferation parameters and gene expression in squamous cell carcinoma cell lines of the head and neck

Background

The survival of patients with locally advanced head and neck cancer is still poor, with 5-year survival rates of 24–35%. The identification of prognostic and predictive markers at the molecular and cellular level could make it possible to find new therapeutic targets and provide "taylor made" treatments. Established cell lines of human squamous cell carcinoma (HNSCC) are valuable models for identifying such markers.

The aim of this study was to establish and characterize a series of cell lines and to compare the cisplatin sensitivity and 18F fluoro-2 deoxy 2 glucose (18F-FDG) uptake of these cell lines with other cellular characteristics, such as proliferation parameters and TP53 and CCND1 status.

Methods

Explant cultures of fresh tumour tissue were cultivated, and six new permanent cell lines were established from 18 HNSCC cases. Successfully grown cell lines were analysed regarding clinical parameters, histological grade, karyotype, DNA ploidy, and index and S-phase fraction (Spf). The cell lines were further characterized with regard to their uptake of 18F-FDG, their sensitivity to cisplatin, as measured by a viability test (crystal violet), and their TP53 and CCND1 status, by fluorescence in situ hybridization (FISH), polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) with DNA sequencing and, for cyclin D1, by immunohistochemistry.

Results

Patients with tumours that could be cultured in vitro had shorter disease-free periods and overall survival time than those whose tumours did not grow in vitro, when analysed with the Kaplan-Meier method and the log-rank test. Their tumours also showed more complex karyotypes than tumours from which cell lines could not be established. No correlation was found between TP53 or CCND1 status and 18F-FDG uptake or cisplatin sensitivity. However, there was an inverse correlation between tumour cell doubling time and 18F-FDG uptake.

Conclusion

In vitro growth of HNSCC cells seem to be an independent prognostic factor, with cell lines being more readily established from aggressive tumours, a phenomenon more dependent on the molecular genetic characteristics of the tumour cells than on tumour location or TNM status.

Is transketolase like 1 a target for the treatment of differentiated thyroid carcinoma? A study on thyroid cancer cell lines

Radioactive iodine-refractory [(18)F] fluorodeoxy-glucose-positron emission tomography-positive thyroid carcinomas represent especially aggressive tumors. Targeting glucose metabolism by the transketolase isoenzyme transketolase like 1 (TKTL-1) which is over-expressed in various neoplasms, may be effective. The correlation of TKTL-1 expression and the response to oxythiamine as the currently best-characterized inhibitor of transketolases was studied in differentiated thyroid cancer cell lines. We determined TKTL-1 expression, proliferation, glucose uptake and GLUT-1 expression in non-treated thyroid cells and recorded the effect of oxythiamine on iodide uptake and on thymidine uptake. TKTL 1 was highest expressed in cell lines derived from more invasive tumors but the expression level was not strongly correlated to proliferation rate, to GLUT-1 expression or to the response to oxythiamine. Oxythiamine showed only a weak effect in the TKTL-1 expressing cell lines. Over-expression of TKTL-1 is not an indicator for responsiveness to oxythiamine. More specific inhibitors should be tested.

Obesity-related promotion of aberrant crypt foci in DMH-treated obese Zucker rats correlates with dyslipidemia rather than hyperinsulinemia

BACKGROUND

Obesity and energy restriction modulate the development of precancerous aberrant crypt foci (ACF) in animal models of colon cancer.

AIM

Investigation of the major obesity-associated determinants for ACF-development and underlying mechanisms leading to ACF-modulation, such as changes in DNA damage or colonocytes hyperproliferation.

METHODS

Lean and obese Zucker rats fed ad libitum (a.l.) or obese pair fed (p.f.) were induced with 1,2-dimethylhydrazine (DMH) for colon cancer. Multiple regression analyses were performed to identify major metabolic factors correlated with ACF number and size (aberrant crypts/ACF). DNA damage is analyzed by the comet-assay, epithelial proliferation by immunohistochemistry.

RESULTS

Aberrant crypt foci number was significantly elevated in Zucker obese a.l. (205.7+/-65.4 vs. lean 9.5+/-6.3, P<0.05) and is reduced by pair feeding in Zucker obese rats (81.4+/-28.5 vs. obese a.l., P<0.05). Compared to lean the ACF size was higher in Zucker obese a.l. (2.1+/-0.3 vs. lean 1.3+/-0.2., P<0.05) but is not reduced by pair feeding (1.7+/-0.2; P>0.05). While ACF number and size were modulated by genotype and/or pair feeding the DMH-induced DNA damage and hyperproliferation in colonocytes did not differ significantly between groups. Regression analysis showed that plasma parameters associated with lipid-metabolism (triglycerides, cholesterol, malondialdehyde) significantly correlated with the ACF number and size while parameters linked to carbohydrate-metabolism (glucose, insulin) were weaker determinants.

CONCLUSION

Obesity or pair feeding-associated modulation of ACF correlate with parameters related to lipid-metabolism but is not accompanied by changes in DNA damage and proliferation.

Hyperinsulinemia, but not other factors associated with insulin resistance, acutely enhances colorectal epithelial proliferation in vivo

The similarity in risk factors for insulin resistance and colorectal cancer (CRC) led to the hypothesis that markers of insulin resistance, such as elevated circulating levels of insulin, glucose, fatty acids, and triglycerides, are energy sources and growth factors in the development of CRC. The objective was thus to examine the individual and combined effects of these circulating factors on colorectal epithelial proliferation in vivo. Rats were fasted overnight, randomized to six groups, infused iv with insulin, glucose, and/or Intralipid for 10 h, and assessed for 5-bromo-2-deoxyuridine labeling of replicating DNA in colorectal epithelial cells. Intravenous infusion of insulin, during a 10-h euglycemic clamp, increased colorectal epithelial proliferation in a dose-dependent manner. The addition of hyperglycemia to hyperinsulinemia did not further increase proliferation. Intralipid infusion alone did not affect proliferation; however, the combination of insulin, glucose, and Intralipid infusion resulted in greater hyperinsulinemia than the infusion of insulin alone and further increased proliferation. Insulin infusion during a 10-h euglycemic clamp decreased total IGF-I levels and did not affect insulin sensitivity. These results provide evidence for an acute role of insulin, at levels observed in insulin resistance, in the proliferation of colorectal epithelial cells in vivo.

Factors influencing [F-18] 2-fluoro-2-deoxy-D-glucose (F-18 FDG) accumulation in melanoma cells: is FDG a substrate of multidrug resistance (MDR)?

In order to specify the influence of multidrug-resistance (MDR) on the accumulation of the PET tracer, F-18 FDG ([Fluorine-18] 2-fluoro-2-deoxy-D-glucose, in melanoma cells, both the MDR function and expression of two human melanoma cell lines SK-MEL 23 and 24, were evaluated. The effects of MDR modulators on FDG accumulation and efflux were also investigated. A functional analysis using representative MDR fluorescent substrates and inhibitors clarified the following characteristics: 1) SK-MEL 23 possesses a highly active function of MRP, but not P-gp. 2) SK-MEL 24 possesses weak functions of both MRP and P-gp. Western blot analysis using monoclonal antibodies for MDR expression demonstrated an exceedingly high MRP expression of SK-MEL 23 and only slight P-gp and MRP expression of SK-MEL 24, corresponding to the functional data. The efflux inhibition assay using F-18 FDG revealed a considerable retention of FDG in SK-MEL 23 in the presence of the MRP inhibitor probenecid. It was also found that the P-gp inhibitor verapamil depressed the FDG efflux of SK-MEL 24. Our present in vitro study suggests that FDG may be a substrate of MDR in some melanoma cells and further MDR may be one of the important factors affecting FDG-PET melanoma imaging.

Opposing effects of estradiol- and testosterone-membrane binding sites on T47D breast cancer cell apoptosis

Classical steroid mode of action involves binding to intracellular receptors, the later acting as ligand-activated nuclear transcription factors. Recently, membrane sites for different steroids have been also identified, mediating rapid, non-genomic, steroid actions. Membrane sites for estrogen and androgen have been found in a number of different cell types, bearing or not classical intracellular receptors. In the present study, with the use of radioligand binding, flow cytometry and confocal laser microscopy, we report that T47D human breast cancer cells express specific and saturable membrane receptors for both estrogen (K(D) 4.06 +/- 3.31 nM) and androgen (K(D) 7.64 +/- 3.15 nM). Upon activation with BSA-conjugated, non-permeable ligands (E(2)-BSA and testosterone-BSA), membrane estrogen receptors protect cells from serum-deprivation-induced apoptosis, while androgen receptors induce apoptosis in serum-supplemented T47D cells. In addition, co-incubation of cells with a fixed concentration of one steroid and varying concentrations of the other reversed the abovementioned effect (apoptosis for androgen, and anti-apoptosis for E(2)), suggesting that the fate of the cell depends on the relative concentration of either steroid in the culture medium. We also report the identification of membrane receptors for E(2) and androgen in biopsy slides from breast cancer patients. Both sites are expressed, with the staining for membrane E(2) being strongly present in ER-negative, less differentiated, more aggressive tumors. These findings suggest that aromatase inhibitors may exert their beneficial effects on breast cancer by also propagating the metabolism of local steroids towards androgen, inducing thus cell apoptosis through membrane androgen receptor activation.

Deoxyglucose uptake by a head and neck squamous carcinoma: influence of changes in proliferative fraction

PURPOSE

Positron emission tomography, using the glucose analogue fluorodeoxy-D-glucose (FDG), is proving to be useful in the early response detection of head and neck tumors. Presently mechanisms underlying changes in FDG uptake after therapy are poorly understood. Response of tumors to therapy is often accompanied by a decrease in tumor cell proliferation. The purpose of this study was to assess whether or not changes in the uptake of deoxyglucose (DG) may reflect differences in proliferative fraction independent of other metabolic changes induced by using therapeutic agents.

METHODS AND MATERIALS

HN5 head and neck tumor cells were grown to different cell densities producing populations of cells with different proliferative indices without the need for exogenous agents to manipulate cell-cycle kinetics. (3)H-DG uptake, S-phase fraction (Spf), and lactate production were determined in each population of cells.

RESULTS

Large differences in Spf between populations of cells were associated with differences in DG incorporation. Lactate production was also found to correlate strongly with DG uptake.

CONCLUSION

Therapy-induced changes in FDG uptake by tumors may be partly due to changes in proliferation.

Uptake of glucose analogues by colonic tumour cells during growth and after treatment with hydroxyurea

SW620 cells were grown in tissue culture flasks to various cell densities producing populations of cells with a range of proliferative indices. The uptake of the two glucose analogues, deoxy-D-glucose (DG) and 3-O-methylglucose (OMG) was determined and found to be associated with S-phase fraction. The strong correlation between DG and OMG uptakes suggested that proliferation-related changes in transmembrane transport accounted for the association with S-phase fraction. Treatment of SW620 cells with the cell cycle inhibitor hydroxyurea was found to increase the uptake of DG and OMG in a time-dependent manner.