Correlation of FDG-PET imaging with Glut-1 and Glut-3 expression in early-stage non-small cell lung cancer

Detection of glucose transporter 1 in living cells for assessment of tumor development and therapy using an electrochemical biosensor

The expression level of glucose transporter 1 (GLUT-1) is highly correlated with tumor malignancy, making it a promising therapeutic target for cancer treatment. The detection of GLUT-1 expression level is significant for cancer discovery and valuating the efficacy of drug treatments. However, current methods for GLUT-1 detection primarily rely on traditional techniques. Therefore, the development of anon-destructive in vivo monitoring system would be invaluable for assessing GLUT-1 expression and tumor responses to various drugs. In this study, an electrochemical platform for detection of GLUT-1 on living cells was established using reduced graphene oxide-multi-wall carbon nanotube composite (rGO-MWCNT) as a conductive coating and toluidine blue O (TBO)-graphene-gold nanoparticle-GLUT-1 antibody as the electrochemical probe. The sensor demonstrated excellent performance in detecting GLUT-1 on cells with a linear range of 10 - 105 cells/mL, good stability and selectivity. The sensor successfully detected GLUT-1 expressions in multiple tumor cell types, including those treated with siRNA or drugs, and the results were consistent with those obtained from traditional methods such as flow cytometry, western blotting, and immunofluorescence. The sensor is promising in evaluating the malignant level of tumor cells, distinguishing glucose uptake pathways in tumor cells, reducing medical costs, and facilitating the translation of electrochemical sensing technology to the clinical settings.

An Investigation into the Usage of Monosaccharides with GLUT1 and GLUT3 as Prognostic Indicators for Cancer

The monosaccharides, glucose, fructose and galactose, are the most common and simplest forms of carbohydrates. The aim of this study was to determine the uptake of glucose as a potential therapeutic target agent for cancer treatment. The stability and transportation calculations of the monosaccharides were carried out in the blood phase by using the density functional theory and docking. The reactivity of monosaccharides, disaccharides and their transportation with GLUT1 and GLUT3 as prognostic indicators for cancer were investigated. The theoretical results of this study were supported by those reported in the literature and used in the prediction of the mechanisms of monosaccharides and the interpretation of their reactivities.

Oxidative Stress and the Intersection of Oncogenic Signaling and Metabolism in Squamous Cell Carcinomas

Squamous cell carcinomas (SCCs) arise from both stratified squamous and non-squamous epithelium of diverse anatomical sites and collectively represent one of the most frequent solid tumors, accounting for more than one million cancer deaths annually. Despite this prevalence, SCC patients have not fully benefited from recent advances in molecularly targeted therapy or immunotherapy. Rather, decades old platinum-based or radiation regimens retaining limited specificity to the unique characteristics of SCC remain first-line treatment options. Historically, a lack of a consolidated perspective on genetic aberrations driving oncogenic transformation and other such factors essential for SCC pathogenesis and intrinsic confounding cellular heterogeneity in SCC have contributed to a critical dearth in effective and specific therapies. However, emerging evidence characterizing the distinct genomic, epigenetic, and metabolic landscapes of SCC may be elucidating unifying features in a seemingly heterogeneous disease. In this review, by describing distinct metabolic alterations and genetic drivers of SCC revealed by recent studies, we aim to establish a conceptual framework for a previously unappreciated network of oncogenic signaling, redox perturbation, and metabolic reprogramming that may reveal targetable vulnerabilities at their intersection.

L-Glucose: Another Path to Cancer Cells

Cancerous tumors comprise cells showing metabolic heterogeneity. Among numerous efforts to understand this property, little attention has been paid to the possibility that cancer cells take up and utilize otherwise unusable substrates as fuel. Here we discuss this issue by focusing on l-glucose, the mirror image isomer of naturally occurring d-glucose; l-glucose is an unmetabolizable sugar except in some bacteria. By combining relatively small fluorophores with l-glucose, we generated fluorescence-emitting l-glucose tracers (fLGs). To our surprise, 2-NBDLG, one of these fLGs, which we thought to be merely a control substrate for the fluorescent d-glucose tracer 2-NBDG, was specifically taken up into tumor cell aggregates (spheroids) that exhibited nuclear heterogeneity, a major cytological feature of malignancy in cancer diagnosis. Changes in mitochondrial activity were also associated with the spheroids taking up fLG. To better understand these phenomena, we review here the Warburg effect as well as key studies regarding glucose uptake. We also discuss tumor heterogeneity involving aberrant uptake of glucose and mitochondrial changes based on the data obtained by fLG. We then consider the use of fLGs as novel markers for visualization and characterization of malignant tumor cells.

Comparison of 3T diffusion-weighted MRI and 18F-FDG PET/CT in musculoskeletal tumours: quantitative analysis of apparent diffusion coefficients and standardized uptake values

OBJECTIVE

To determine whether the apparent diffusion coefficient (ADC) on 3T MR imaging including diffusion-weighted MR imaging (DWI) correlate with the standardized uptake value (SUV) on 18F-FDG PET/CT in musculoskeletal tumours.

METHODS

This retrospective cohort study included 57 patients (36 males, 21 females, mean age 54 years, range 12-90 years) with pathologically confirmed soft tissue (n = 32) and bone (n = 25) tumours who underwent 3T MR imaging including DWI and whole-body 18F-FDG PET/CT before treatment. 14 patients had follow-up MR imaging and 18F-FDG PET/CT after treatment. The minimum (ADC_min) and mean (ADC_mean) ADCs of musculoskeletal tumour, ADC of normal skeletal muscle (ADC_mus), SUV_max and SUV_mean of musculoskeletal tumour were obtained. Correlation between ADCs and SUVs was assessed using Pearson correlation coefficients (r). ADC_min and SUV_max were compared between pretreatment and posttreatment by t-test.

RESULTS

There was inverse correlation between SUV_max and the ratio ADC_min/ADC_mus (r = - 0.505 to - 0.495, p ≤ 0.001) and between SUV_mean and the ratio ADC_mean/ADC_mus (r = - 0.501 to - 0.493, p = 0.001). After treatment ADC was significantly increased whereas SUV was significantly decreased (p = 0.001). There was significant correlation in percent change between the initial and follow-up values of ADC_min and SUV_max (r = 0.750 to 0.773, p ≤ 0.005). The ADC_min was increased by 163% and SUV_max was decreased by 61% in 11 patients with treatment response.

CONCLUSION

ADC at 3T MR DWI and SUV at 18F-FDG PET/CT have an inverse correlation in musculoskeletal tumours.

ADVANCES IN KNOWLEDGE

Our study showed that ADC at 3T DWI and SUV at 18F-FDG PET/CT had an inverse correlation in musculoskeletal tumours.

Associations between GLUT expression and SUV values derived from FDG-PET in different tumors-A systematic review and meta analysis

Purpose

Fluorodeoxyglucose-Positron-emission tomography (FDG-PET), quantified by standardized uptake values (SUV), is one of the most used functional imaging modality in clinical routine. It is widely acknowledged to be strongly associated with Glucose-transporter family (GLUT)-expression in tumors, which mediates the glucose uptake into cells. The present systematic review sought to elucidate the association between GLUT 1 and 3 expression with SUV values in various tumors.

Methods

MEDLINE library was screened for associations between FDG-PET parameters and GLUT correlation cancer up to October 2018.

Results

There were 53 studies comprising 2291 patients involving GLUT 1 expression and 11 studies comprising 405 patients of GLUT 3 expression. The pooled correlation coefficient for GLUT 1 was r = 0.46 (95% CI 0.40–0.52), for GLUT 3 was r = 0.35 (95%CI 0.24–0.46). Thereafter, subgroup analyses were performed. The highest correlation coefficient for GLUT 1 was found in pancreatic cancer r = 0.60 (95%CI 0.46–0.75), the lowest was identified in colorectal cancer with r = 0.21 (95% CI -0.57–0.09).

Conclusion

An overall only moderate association was found between GLUT 1 expression and SUV values derived from FDG-PET. The correlation coefficient with GLUT 3 was weaker. Presumably, the underlying mechanisms of glucose hypermetabolism in tumors are more complex and not solely depended on the GLUT expression.

Can the Efficacy of [18F]FDG-PET/CT in Clinical Oncology Be Enhanced by Screening Biomolecular Profiles?

Positron Emission Tomography (PET) is a functional imaging modality widely used in clinical oncology. Over the years the sensitivity and specificity of PET has improved with the advent of specific radiotracers, increased technical accuracy of PET scanners and incremental experience of Radiologists. However, significant limitations exist—most notably false positives and false negatives. Additionally, the accuracy of PET varies between cancer types and in some cancers, is no longer considered a standard imaging modality. This review considers the relative influence of macroscopic tumour features such as size and morphology on 2-Deoxy-2-[¹⁸F]fluoroglucose ([¹⁸F]FDG) uptake by tumours which, though well described in the literature, lacks a comprehensive assessment of biomolecular features which may influence [¹⁸F]FDG uptake. The review aims to discuss the potential influence of individual molecular markers of glucose transport, glycolysis, hypoxia and angiogenesis in addition to the relationships between these key cellular processes and their influence on [¹⁸F]FDG uptake. Finally, the potential role for biomolecular profiling of individual tumours to predict positivity on PET imaging is discussed to enhance accuracy and clinical utility.

18F-FDG PET intensity correlates with a hypoxic gene signature and other oncogenic abnormalities in operable non-small cell lung cancer

BACKGROUND

18F-fluorodeoxyglucose positron emission tomography (FDG-PET) is critical for staging non-small-cell lung cancer (NSCLC). While PET intensity carries prognostic significance, the genetic abnormalities associated with increased intensity remain unspecified.

METHODS

NSCLC samples (N = 34) from 1999 to 2011 for which PET data were available were identified from a prospectively collected tumor bank. PET intensity was classified as mild, moderate, or intense based on SUVmax measurement or radiology report. Associations between genome-wide expression (RNAseq) and PET intensity were determined. Associations with overall survival were then validated in two external NSCLC cohorts.

RESULTS

Overall survival was significantly worse in patients with PET-intense (N = 11) versus mild (N = 10) tumors (p = 0.039). Glycolytic gene expression patterns were markedly similar between intense and mild tumors. Gene ontology analysis demonstrated significant enhancement of cell-cycle and proliferative processes in FDG-intense tumors (p<0.001). Gene set enrichment analysis (GSEA) suggested associations between PET-intensity and canonical oncogenic signaling pathways including MYC, NF-κB, and HIF-1. Using an external cohort of 25 tumors with PET and genomic profiling data, common genes and gene sets were validated for additional study (P<0.05). Of these common gene sets, 20% were associated with hypoxia or HIF-1 signaling. While HIF-1 expression did not correlate with poor survival in the NSCLC validation cohort (N = 442), established targets of hypoxia signaling (PLAUR, ADM, CA9) were significantly associated with poor overall survival.

CONCLUSIONS

PET-intensity is associated with a variety of oncogenic alterations in operable NSCLC. Adjuvant targeting of these pathways may improve survival among patients with PET-intense tumors.

Comparative metabolic analysis in head and neck cancer and the normal gingiva

OBJECTIVES

Chronic accumulation of lactate in malignant tumor tissue is associated with increased malignancy and radioresistance. For this study, biopsies of primary head and neck squamous cell carcinoma (HNSCC) and of the normal gingiva of the same patient were compared via metabolic profiling to the healthy gingiva from cancer-free patients.

MATERIALS AND METHODS

Cryobiopsies of 140 HNSCC patients were used to determine ATP, lactate, and glucose concentrations of the tumor and normal gingiva via induced metabolic bioluminescence imaging (imBI). Additionally, these metabolites were quantified in a collective of 79 healthy (non-tumor-bearing) patients. Furthermore, tumor samples were analyzed via immunofluorescence imaging and quantitative real-time PCR for the expression of lactate and glucose transporters.

RESULTS

There were significant differences in ATP concentrations detectable between the tumor, normal gingiva of tumor patients, and gingiva from healthy patients. Lactate concentrations were significantly increased in tumor tissue compared to the normal gingiva of tumor patients as well as the gingiva from healthy patients. Concerning glucose, there was a significant decrease in glucose concentrations detectable in the tumor biopsies compared to the normal gingiva of tumor patients. On the other hand, tumor samples from patients revealed significantly elevated relative expression levels of monocarboxylate transporters (MCT-1 and MCT-4), as well as glucose transporters (GLUT-1 and GLUT-3) compared to the corresponding normal gingiva of each patient.

CONCLUSIONS

We could demonstrate that the lactate concentration in HNSCC correlates with primary tumor (T) stage.

CLINICAL RELEVANCE

The aim of this study was to identify metabolic parameters to improve early cancer diagnosis, allow predictions on the degree of malignancy, and contribute to a personalized tumor therapy.

The distinct metabolic phenotype of lung squamous cell carcinoma defines selective vulnerability to glycolytic inhibition

Adenocarcinoma (ADC) and squamous cell carcinoma (SqCC) are the two predominant subtypes of non-small cell lung cancer (NSCLC) and are distinct in their histological, molecular and clinical presentation. However, metabolic signatures specific to individual NSCLC subtypes remain unknown. Here, we perform an integrative analysis of human NSCLC tumour samples, patient-derived xenografts, murine model of NSCLC, NSCLC cell lines and The Cancer Genome Atlas (TCGA) and reveal a markedly elevated expression of the GLUT1 glucose transporter in lung SqCC, which augments glucose uptake and glycolytic flux. We show that a critical reliance on glycolysis renders lung SqCC vulnerable to glycolytic inhibition, while lung ADC exhibits significant glucose independence. Clinically, elevated GLUT1-mediated glycolysis in lung SqCC strongly correlates with high ¹⁸F-FDG uptake and poor prognosis. This previously undescribed metabolic heterogeneity of NSCLC subtypes implicates significant potential for the development of diagnostic, prognostic and targeted therapeutic strategies for lung SqCC, a cancer for which existing therapeutic options are clinically insufficient.

Adenocarcinoma and squamous cell carcinoma are distinct subtypes of non-small cell lung cancer. Here, the authors show that increased glycolytic flux, via increased glucose transporter Glut1 expression, is a core metabolic feature of squamous cell carcinoma that renders it sensitive to glycolysis inhibition.

Regulation of glycolysis in head and neck squamous cell carcinoma

Glycolysis is highly upregulated in head and neck squamous cell carcinoma (HNSCC). HNSCC glycolysis is an important contributor to disease progression and decreases sensitivity to radiation or chemotherapy. Despite therapeutic advances, the survival rates for HNSCC patients remain low. Understanding glycolysis regulation in HNSCC will facilitate the development of effective therapeutic strategies for this disease. In this review, we will evaluate the regulation of altered HNSCC glycolysis and possible therapeutic approaches by targeting glycolytic pathways.

The role of new PET tracers for lung cancer

18F-fluorodeoxyglucose (18F-FDG) positron emission tomography-computed tomography (PET/CT) is established for characterising indeterminate pulmonary nodules and staging lung cancer where there is curative intent. Whilst a sensitive technique, specificity for characterising lung cancer is limited. There is recognition that evaluation of other aspects of abnormal cancer biology in addition to glucose metabolism may be more helpful in characterising tumours and predicting response to novel targeted cancer therapeutics. Therefore, efforts have been made to develop and evaluate new radiopharmaceuticals in order to improve the sensitivity and specificity of PET imaging in lung cancer with regards to characterisation, treatment stratification and therapeutic monitoring. 18F-fluorothymidine (18F-FLT) is a marker of cellular proliferation. It shows a lower accumulation in tumours than 18F-FDG as it only accumulates in the cells that are in the S phase of growth and demonstrates a low sensitivity for nodal staging. Its main role is in evaluating treatment response. Methionine is an essential amino acid. 11C-methionine is more specific and sensitive than 18F-FDG in differentiating benign and malignant thoracic nodules. 18Ffluoromisonidazole (18F-FMISO) is used for imaging tumour hypoxia. Tumour response to treatment is significantly related to the level of tumour oxygenation. Angiogenesis is the process by which new blood vessels are formed in tumours and is involved in tumour growth and metastatic tumour spread and is a therapeutic target. Most clinical studies have focused on targeted integrin PET imaging of which αvβ3 integrin is the most extensively investigated. It is upregulated on activated endothelial cells in association with tumour angiogenesis. Neuroendocrine tumour tracers, particularly 68Ga-DOTA-peptides, have an established role in imaging of carcinoid tumours. Whilst most of these tracers have predominantly been used in the research environment, they offer exciting opportunities for improving staging, characterisation, stratification and response assessment in an era of increased personalised therapy in lung cancer.

Integrating Tumor and Stromal Gene Expression Signatures With Clinical Indices for Survival Stratification of Early-Stage Non-Small Cell Lung Cancer

BACKGROUND

Accurate survival stratification in early-stage non-small cell lung cancer (NSCLC) could inform the use of adjuvant therapy. We developed a clinically implementable mortality risk score incorporating distinct tumor microenvironmental gene expression signatures and clinical variables.

METHODS

Gene expression profiles from 1106 nonsquamous NSCLCs were used for generation and internal validation of a nine-gene molecular prognostic index (MPI). A quantitative polymerase chain reaction (qPCR) assay was developed and validated on an independent cohort of formalin-fixed paraffin-embedded (FFPE) tissues (n = 98). A prognostic score using clinical variables was generated using Surveillance, Epidemiology, and End Results data and combined with the MPI. All statistical tests for survival were two-sided.

RESULTS

The MPI stratified stage I patients into prognostic categories in three microarray and one FFPE qPCR validation cohorts (HR = 2.99, 95% CI = 1.55 to 5.76, P < .001 in stage IA patients of the largest microarray validation cohort; HR = 3.95, 95% CI = 1.24 to 12.64, P = .01 in stage IA of the qPCR cohort). Prognostic genes were expressed in distinct tumor cell subpopulations, and genes implicated in proliferation and stem cells portended poor outcomes, while genes involved in normal lung differentiation and immune infiltration were associated with superior survival. Integrating the MPI with clinical variables conferred greatest prognostic power (HR = 3.43, 95% CI = 2.18 to 5.39, P < .001 in stage I patients of the largest microarray cohort; HR = 3.99, 95% CI = 1.67 to 9.56, P < .001 in stage I patients of the qPCR cohort). Finally, the MPI was prognostic irrespective of somatic alterations in EGFR, KRAS, TP53, and ALK.

CONCLUSION

The MPI incorporates genes expressed in the tumor and its microenvironment and can be implemented clinically using qPCR assays on FFPE tissues. A composite model integrating the MPI with clinical variables provides the most accurate risk stratification.

Oncogene pathway activation in mammary tumors dictates FDG-PET uptake

Increased glucose utilization is a hallmark of human cancer that is used to image tumors clinically. In this widely used application, glucose uptake by tumors is monitored by positron emission tomography of the labeled glucose analogue 2[(18)F]fluoro-2-deoxy-D-glucose (FDG). Despite its widespread clinical use, the cellular and molecular mechanisms that determine FDG uptake--and that underlie the heterogeneity observed across cancers-remain poorly understood. In this study, we compared FDG uptake in mammary tumors driven by the Akt1, c-MYC, HER2/neu, Wnt1, or H-Ras oncogenes in genetically engineered mice, correlating it to tumor growth, cell proliferation, and expression levels of gene involved in key steps of glycolytic metabolism. We found that FDG uptake by tumors was dictated principally by the driver oncogene and was not independently associated with tumor growth or cellular proliferation. Oncogene downregulation resulted in a rapid decrease in FDG uptake, preceding effects on tumor regression, irrespective of the baseline level of uptake. FDG uptake correlated positively with expression of hexokinase-2 (HK2) and hypoxia-inducible factor-1α (HIF1α) and associated negatively with PFK-2b expression and p-AMPK. The correlation between HK2 and FDG uptake was independent of all variables tested, including the initiating oncogene, suggesting that HK2 is an independent predictor of FDG uptake. In contrast, expression of Glut1 was correlated with FDG uptake only in tumors driven by Akt or HER2/neu. Together, these results demonstrate that the oncogenic pathway activated within a tumor is a primary determinant of its FDG uptake, mediated by key glycolytic enzymes, and provide a framework to interpret effects on this key parameter in clinical imaging.

The effect of PPAR-γ agonist on (18)F-FDG PET imaging for differentiating tumors and inflammation lesions

INTRODUCTION

(18)F-2-deoxy-2-fluoro-d-glucose ((18)F-FDG) positron emission tomography (PET) has been used for imaging human cancers for several decades. Despite its extensive use, (18)F-FDG PET imaging has limitations in the tumor findings. The goal of this study was to investigate the potential of a PPAR-γ agonist pioglitazone (PIO) to distinguish tumors and inflammatory lesions in (18)F-FDG PET imaging.

METHODS

Studies of cellular uptake of (18)F-FDG and Western blot were performed in macrophage (RAW264.7) and three tumor cell lines (A549, KB, and MDA-MB-231) after treatment with PIO. In vivo microPET/CT imaging and biodistribution were performed in animal models.

RESULTS

The uptake of (18)F-FDG in the macrophages was decreased and uptake of (18)F-FDG in the tumor cells was increased when these cells were treated with PIO. Western blot showed that the expression of Glut1 was reduced by treatment of PIO in the macrophage cells, whereas the expression of Glut1 in the tumor cells was increased. In vivo PET/CT imaging revealed that (18)F-FDG uptake (%ID/g) in the tumors was enhanced from 4.05±1.46 to 5.28±1.92 for A549, from 3.9±0.5 to 4.9±0.2 for KB, and from 9.14±0.86 to 13.48±2.07 for MDA-MB-231 tumors after treatment with PIO. Unlike tumors, the RAW264.7 xenograft model showed the reduced (18)F-FDG uptake in the inflammatory lesion from 11.74±1.19 to 6.50±1.47. The results of biodistribution also showed that (18)F-FDG uptake in the tumors were increased after treatment of PIO. However, the uptake of inflammation lesions was reduced.

CONCLUSIONS

In this study, we demonstrated the effect of a PPAR-γ agonist PIO on (18)F-FDG uptake in tumors and inflammation in vitro and in vivo. PIO has potential to differentiate tumors and inflammatory lesions on (18)F-FDG PET imaging.

Does diabetes mellitus influence standardized uptake values of fluorodeoxyglucose positron emission tomography in colorectal cancer?

Background/Aims

Hyperglycemia is associated with decreased 2-¹⁸[F]fluoro-2-deoxy-D-glucose (FDG) uptake by tumors assessed by positron emission tomography (PET). In this retrospective study we investigated a comparison of standardized uptake values (SUVs) in patients with primary colorectal cancers who either had diabetes mellitus (DM) or were otherwise healthy.

Methods

The medical records of 397 patients who were diagnosed with colorectal cancer and underwent PET-CT between January 2006 and December 2012 were analyzed. Eighty patients with DM and 317 patients without DM were included. Clinical characteristics were reviewed and maximal standardized uptake values (SUV_max) were calculated in the primary colorectal lesions.

Results

There was no significant difference between tumor SUV_max in DM patients (10.60±5.78) and those without DM (10.92±5.44). In addition, no significant difference was detected between tumor SUV_max in DM patients with glycated hemoglobin (HbA1c) levels <8% (10.34±5.17) and those with HbA1c levels ≥8% (10.61±7.27). The maximum size of the primary colorectal tumor was associated with SUV_max in a linear regression analysis.

Conclusion

The results of this study showed that DM did not influence FDG uptake values in colorectal cancer patients regardless of glucose levels.

NF-κB protein expression associates with (18)F-FDG PET tumor uptake in non-small cell lung cancer: a radiogenomics validation study to understand tumor metabolism

INTRODUCTION

We previously demonstrated that NF-κB may be associated with (18)F-FDG PET uptake and patient prognosis using radiogenomics in patients with non-small cell lung cancer (NSCLC). To validate these results, we assessed NF-κB protein expression in an extended cohort of NSCLC patients.

METHODS

We examined NF-κBp65 by immunohistochemistry (IHC) using a Tissue Microarray. Staining intensity was assessed by qualitative ordinal scoring and compared to tumor FDG uptake (SUVmax and SUVmean), lactate dehydrogenase A (LDHA) expression (as a positive control) and outcome using ANOVA, Kaplan Meier (KM), and Cox-proportional hazards (CPH) analysis.

RESULTS

365 tumors from 355 patients with long-term follow-up were analyzed. The average age for patients was 67±11 years, 46% were male and 67% were ever smokers. Stage I and II patients comprised 83% of the cohort and the majority had adenocarcinoma (73%). From 88 FDG PET scans available, average SUVmax and SUVmean were 8.3±6.6, and 3.7±2.4 respectively. Increasing NF-κBp65 expression, but not LDHA expression, was associated with higher SUVmax and SUVmean (p=0.03 and 0.02 respectively). Both NF-κBp65 and positive FDG uptake were significantly associated with more advanced stage, tumor histology and invasion. Higher NF-κBp65 expression was associated with death by KM analysis (p=0.06) while LDHA was strongly associated with recurrence (p=0.04). Increased levels of combined NF-κBp65 and LDHA expression were synergistic and associated with both recurrence (p=0.04) and death (p=0.03).

CONCLUSIONS

NF-κB IHC was a modest biomarker of prognosis that associated with tumor glucose metabolism on FDG PET when compared to existing molecular correlates like LDHA, which was synergistic with NF-κB for outcome. These findings recapitulate radiogenomics profiles previously reported by our group and provide a methodology for studying tumor biology using computational approaches.

Positron emission tomography: clinical applications in oncology. Part 1

Positron emission tomography is a functional diagnostic imaging technique, which can accurately measure in vivo distribution of a radiopharmaceutical with high resolution. The ability of positron emission tomography to study various biologic processes opens up new possibilities for both research and day-to-day clinical use. Positron emission tomography has progressed rapidly from being a research technique in laboratories to a routine clinical imaging modality becoming part of armamentarium for the medical profession. The most widely used radiotracer in positron emission tomography is 18F-fluoro-2-deoxy-D-glucose (FDG), which is an analog of glucose. FDG uptake in cells is directly proportional to glucose metabolism of cells. Since glucose metabolism is increased many fold in malignant tumors, positron emission tomography has a high sensitivity and high negative predictive value. Positron emission tomography with FDG is now the standard of care in initial staging, monitoring the response to therapy and management of lung cancer, colorectal cancer, lymphoma, melanoma, esophageal cancer, head and neck cancer and breast cancer. The aim of this article is to review the clinical applications of positron emission tomography in oncology.

Glucose conjugation for the specific targeting and treatment of cancer

Cancers of diverse origins exhibit marked glucose avidity and high rates of aerobic glycolysis. Increased understanding of this dysfunctional metabolism known as the Warburg effect has led to an interest in targeting it for cancer therapy. One promising strategy for such targeting is glycoconjugation, the linking of a drug to glucose or another sugar. This review summarizes the most salient examples of glycoconjugates, in which known cytotoxins or targeted anticancer therapeutics have been linked to glucose (or another glucose transporter substrate sugar) for improved cancer targeting and selectivity. Building on these examples, this review also provides a series of guidelines for the design and mechanistic evaluation of future glycoconjugates.

¹⁸F-fluoro-2-deoxyglucose uptake on PET CT and glucose transporter 1 expression in colorectal adenocarcinoma

AIM

To evaluate the correlation between the level of (18)F-fluoro-2-deoxyglucose ((18)F-FDG) uptake and glucose transporter 1 (GLUT1) expression in colorectal adenocarcinoma (CRA).

METHODS

Forty four patients with resected CRA and preoperative (18)F-FDG positron emission tomography - computed tomography data were investigated in this study. Comparison of maximum standardized uptake value (SUVmax) of the lesion was made with GLUT1 expression by immunohistochemistry and various clinicopathologic factors including tumor volume, invasion depth, gross finding, and lymph node metastasis.

RESULTS

SUVmax was 14.45 ± 7.0 in negative GLUT1 expression cases, 15.51 ± 5.7 in weak GLUT1 expression cases, and 16.52 ± 6.8 in strong GLUT1 expression cases, and there was no correlation between between GLUT1 expression and SUVmax. SUVmax was significantly correlated with tumor volume (P < 0.001). However, there was no significant differences in SUVmax and GLUT1 expression among other clinicopathologic factors.

CONCLUSION

GLUT1 expression does not correlates significantly with (18)F-FDG uptake in CRA. (18)F-FDG uptake was increased with tumor volume, which is statistically significant.

Differences in metabolism between adeno- and squamous cell non-small cell lung carcinomas: spatial distribution and prognostic value of GLUT1 and MCT4

BACKGROUND

Hypoxia leads to changes in tumor cell metabolism such as increased glycolysis. In this study, we examined the spatial distribution of the glycolysis and hypoxia related markers glucose transporter 1 (GLUT1) and monocarboxylate transporter 4 (MCT4) expression in relation to the vasculature in stage I, II and resectable stage IIIA NSCLC. Furthermore, associations of these markers with survival were investigated.

METHODS

GLUT1 and MCT4 expression were determined in 90 NSCLC fresh frozen biopsies using immunohistochemical techniques and a computerized image analysis system. Markers were analyzed for adenocarcinomas (n=41) and squamous cell carcinomas (n=34) separately. Eighty-four patients were retrospectively evaluated for relapse and survival.

RESULTS

Squamous cell carcinomas demonstrated higher GLUT1 expression, relative to adenocarcinomas. Also, in squamous cell carcinomas, GLUT1 and MCT4 expression increased with increasing distance from the vasculature, whereas in adenocarcinomas upregulation of MCT4 was already found at closer distance from vessels. In adenocarcinomas, high GLUT1 expression correlated with a poor differentiation grade and positive lymph nodes at diagnosis. High GLUT1 plus high MCT4 expression was associated with a poor disease-specific survival in only adenocarcinomas (p=0.032).

CONCLUSION

Analysis of GLUT1 and MCT4 expression on the histological level suggested a different metabolism for adenocarcinomas and squamous cell carcinomas. Likely, adenocarcinomas rely mainly on aerobic glycolysis for ATP production, whereas the behavior of squamous cell carcinomas is more physiologically, i.e. mitochondrial oxidation with anaerobic glycolysis under hypoxic conditions. High GLUT1 plus high MCT4 expression indicated an aggressive tumor behavior in adenocarcinomas. This subgroup of tumors may benefit from new treatment approaches, such as MCT4 inhibitors. Since this study has an exploratory character, our results warrant further investigation and need independent validation.

Correlation between glucose transporter-1 expression and 18F-fluoro-2-deoxyglucose uptake on positron emission tomography in lung cancer

PURPOSE

The aim of this study was to determine if glucose transporter-1 (Glut1) expression correlates with (18)F-FDG ((18)F-fluoro-2-deoxyglucose) uptake on positron emission tomography (PET) in lung cancer and to examine the similarities and differences between them.

METHODS

A total of 34 patients with resected primary lung cancers were investigated in this study. There were 17 adenocarcinomas, 12 squamous cell carcinomas, and 5 cancers of other cell types. Immunohistochemical Glut1 intensity was categorized into three groups: negative, positive, and strongly positive. Glut1 frequency was defined by the proportion of positive cells among all cancer cells, and it was graded on a semiquantitative scale as 0-100% in 10% increments. The data are expressed as the mean +/- SD.

RESULTS

Maximum standardized uptake values (SUVmax) were 4.8 +/- 6.3 in "negative" Glut1 intensity cases, 4.7 +/- 3.1 in "positive" Glut1 intensity cases, and 11.2 +/- 5.2 in "strongly positive" Glut1 intensity cases. Although SUVmax correlated significantly with tumor size (correlation coefficient 0.58, P = 0.00033), Glut1 frequency did not correlate significantly with tumor size (correlation coefficient 0.18, P = 0.301). Cell type and cell differentiation correlated significantly with Glut1 expression and (18)F-FDG uptake.

CONCLUSION

Glut1 expression correlates significantly with (18)F-FDG uptake. There are similarities in cell differentiation and cell type between Glut1 expression and (18)F-FDG uptake. (18)F-FDG uptake correlates significantly with tumor size, but Glut1 expression does not.

GLUT1 and GLUT3 as potential prognostic markers for Oral Squamous Cell Carcinoma

We associated clinical-pathological features of 142 OSCC with the expression pattern of GLUT1 and GLUT3 in order to estimate their prognostic value.

METHODS

Clinical-pathological features and overall survival data of 142 patients with Oral Squamous Cell Carcinoma (OSCC) were retrospectively reviewed from A.C.Camargo hospital records. A tissue microarray (TMA) was built for the immunohistochemical (IHC) analysis of GLUT 1 and GLUT 3. IHC results were evaluated according to the staining pattern and number of positive cells.

RESULTS

GLUT 1 was over expressed in 50.3% of OSSC cases showing membrane staining pattern. However, nuclear expression was observed in 49.7% of the analyzed cases. GLUT 3 over expression was detected in 21.1% of OSCC cases. The pattern of GLUT 1 expression showed significant association with alcohol consumption (p = 0.004). Positive cell membrane GLUT 3 protein expression was associated with advanced clinic-staging of tumours (p = 0.005) as well as with vascular embolization (p = 0.005). Positive expression of GLUT 3 was associated with unfavorable free-disease survival (p = 0.021).

CONCLUSION

GLUT1 and GLUT3 protein expression evaluated by immunohistochemistry are, significantly, indicators of poor prognosis outcome in oral squamous cell carcinoma, probably due to the enhanced glycolytic metabolism of more aggressive neoplastic cells.

Imaging of proliferation with 18F-FLT PET/CT versus 18F-FDG PET/CT in non-small-cell lung cancer

PURPOSE

To compare the diagnostic efficacies of (18)F-FLT and (18)F-FDG PET/CT in non-small-cell lung cancer (NSCLC), focusing on the correlation between FLT and FDG tumour uptake and tumour cell proliferation as indicated by the cyclin D1 labelling index.

METHODS

A total of 31 patients with NSCLC underwent FLT and FDG PET/CT scanning followed by surgery. PET/CT images were compared with the pathology. Tumour cell proliferation was assessed by cyclin D1 immunohistochemistry.

RESULTS

The sensitivities of FLT and FDG PET/CT for the primary lesion were 74% and 94%, respectively (p=0.031). For N staging, 77% patients were correctly staged, 6% overstaged, 16% understaged by FLT, while the values for FDG were 77%, 16% and 6%, respectively. The sensitivity, specificity, accuracy, and positive predictive value with FLT for lymph nodes were 65%, 98%, 93% and 89%, respectively, and 85%, 84%, 84% and 52% with FDG (p<0.01).Tumour SUV of FLT was significantly correlated with the cyclin D1 labelling index (r=0.644; p<0.01), but the SUV of FDG was not significantly correlated (r=0.293; p>0.05).

CONCLUSION

In terms of N staging, FLT PET/CT resulted in understaging of more patients but overstaging of fewer patients, and for regional lymph nodes showed better specificity, accuracy and positive predictive value than FDG PET/CT in NSCLC. Tumour FLT uptake was correlated with tumour cell proliferation as indicated by the cyclin D1 labelling index, suggesting that further studies are needed to evaluate the use of FLT PET/CT for the assessment of therapy response to anticancer drugs.

Imaging pharmacodynamics in oncology: the potential significance of "flares"

The clinical use of (18)F-fluorodeoxyglucose (FDG) positron emission tomography in monitoring anticancer treatment is expanding. At the same time a number of radiotracers aiming to image different aspects of tumour biology such as proliferation and apoptosis are being developed. However, the factors determining changes of radiotracer uptake parameters in response to treatment are not well understood. In many cases, cellularity may be the primary determinant of changes of FDG uptake and may confound the interpretation of metabolic changes. Early imaging assessments have in some cases showed transient increases of uptake parameters, commonly termed "flares", which are likely to be unaffected by cellularity and directly reflect pharmacodynamics at a cellular level. In this review a number of settings where molecular imaging "flares" have been described are discussed. Such changes may often be clinically informative and warrant careful study as potential predictive biomarkers.

18F-FDG uptake in lung, breast, and colon cancers: molecular biology correlates and disease characterization

It is hoped that in the not too distant future, noninvasive imaging-based molecular interrogation and characterization of tumors can improve our fundamental understanding of the dynamic biologic behavior of cancer. For example, the new dimension of diagnostic information that is provided by (18)F-FDG PET has led to improved clinical decision making and management changes in a substantial number of patients with cancer. In this context, the aim of this review is to bring together and summarize the current data on the correlation between the underlying molecular biology and the clinical observations of tumor (18)F-FDG accumulation in 3 major human cancers: lung, breast, and colon.

Glut1 and Glut3 expression in lymphoma and their association with tumor intensity on 18F-fluorodeoxyglucose positron emission tomography

OBJECTIVE

To evaluate the expression of glucose transporters (Gluts) 1 and 3 in Hodgkin and nonHodgkin lymphoma and to assess the association between their expression and the tumor intensity on 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET).

METHODS

All 31 lymphoma patients in whom the histologic diagnosis was made and who had also undergone a prechemotherapy PET scan at our institution between June 2001 and December 2005 were included in this retrospective study. The percentage of tumor cells in the various lymphoma subtypes was estimated by comparison of hematoxylin and eosin stain with a lineage-associated immunohistochemical stain on the same block of tissue. Tissue specimens were stained with Glut1 and Glut3 antibodies. The percentages of Glut1+ and Glut3+ cells in the entire cell population (lymphoma cells and nonlymphomatous cells) and among the lymphoma cells were estimated. FDG PET images were reviewed and the tumor intensity was assessed by calculating the maximum standard uptake value (SUVmax). Correlation coefficients between SUVmax and the percentage of Glut1+ and Glut3+ cells in the entire cell population were calculated.

RESULTS

In all 31 cases, tumors were visible on FDG PET and positive for Glut1 and Glut3. The correlation between the percentage of Glut1+ cells and SUVmax was statistically significant across all 31 cases (r = 0.73, P<0.0001, 95% confidence interval: 0.50-0.86) and across the 25 cases of nonHodgkin lymphoma (r = 0.71, P<0.0001, 95% confidence interval: 0.44-0.87). There was no statistically significant correlation between the percentage of Glut3+ cells and SUVmax. More importantly, in 16 of 31 cases (52%), only nonlymphomatous, benign cells expressed Glut1 or Glut3.

CONCLUSION

Intensity of lymphoma on FDG PET is likely associated with Glut1 expression. The nonlymphomatous, benign cells may play an important role in visualization of lymphoma on FDG PET.

The effect of PPAR-gamma agonist on (18)F-FDG uptake in tumor and macrophages and tumor cells

PURPOSE

The peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is a member of the nuclear receptor superfamily of ligand-dependent transcription factors, and its role in adipogenesis and glucose metabolism has been well established. PPAR-gamma agonists have been shown to inhibit many cytokines and to have anti-inflammatory effects. In pathologic conditions, enhanced fluoro-2-deoxy-D-glucose (FDG) uptake is observed not only in malignant tumors but also in inflammatory lesions, and this uptake occurs through the glucose transporter in these cells. Thus, the present study was undertaken to investigate the potential of using PPAR-gamma's glucose uptake ability as a diagnostic tool to differentiate between macrophage and tumor cells.

MATERIALS AND METHODS

Cellular uptake studies were carried out on macrophage and two tumor cell lines for comparison by using (18)F-FDG. Western blot analysis was performed to determine the expression levels of both the glucose transporter and hexokinase protein. To confirm the possibility of differentiation between tumor and inflammatory lesions using rosiglitazone based on in vitro studies, (18)F-FDG (3.7 x 10(6) Bq) uptake in A549 and RAW 264.7 xenograft mice was compared.

RESULTS

The cellular uptake study findings were quite different for macrophages and tumor cells. (18)F-FDG uptakes by macrophages decreased by about 60% but was increased twofold in tumor cells after rosiglitazone treatment. Moreover, the expressions of proteins related to glucose uptake correlated well with cellular glucose accumulation in both cell types. Higher tumor uptake was observed after the injection of rosiglitazone in A549 xenograft mice (1.58+/-0.55 to 4.66+/-1.16), but no significant change of (18)F-FDG uptake was shown in RAW 264.7 xenograft mice (4.04+/-1.16 to 4.00+/-0.14).

CONCLUSION

The present study demonstrates the roles of PPAR-gamma agonist on FDG uptake in macrophages and tumor cells in vitro and in vivo. Our findings suggest that rosiglitazone has the potential to increase the contrast between tumor and inflammatory lesions.

The maximum uptake of (18)F-deoxyglucose on positron emission tomography scan correlates with survival, hypoxia inducible factor-1alpha and GLUT-1 in non-small cell lung cancer

The purpose of this study was to investigate the relation between the standardised uptake value (SUV) on (18)F-fluoro-2-deoxy-glucose-positron emission tomography scan and hypoxia related markers (HIF-1alpha and CAIX), a proliferation-related marker (Ki-67) and glucose transporters (GLUT-1 and GLUT-3) in non-small cell lung cancer (NSCLC). One hundred and two patients, scheduled for complete resection, received a PET scan in Leuven or Maastricht/Aachen. The maximal SUV (SUV(max)) was correlated with survival and immunohistochemical staining patterns. The actuarial survival was worse for patients showing a high SUV(max), the best discriminative value being 8.0 (Leuven, p=0.032) and 11.0 (Maastricht, p=0.007). Tumours with a high SUV(max) expressed in a higher proportion HIF-1alpha (63.1% versus 37.9%, p=0.024) and GLUT-1 (82.9% versus 62.5%, p=0.025), than tumours with a low SUV(max). No significant difference was found in the expression of CAIX, Ki-67 and GLUT-3. This study supports preclinical data that hypoxia is associated with a higher uptake of FDG.

FDG uptake, glucose transporter type 1, and Ki-67 expressions in non-small-cell lung cancer: correlations and prognostic values

PURPOSE

FDG uptake mediated by glucose transporter type 1 (Glut-1) and tumor proliferative activity assessed by Ki-67 expression provide prognostic information in patients with non-small-cell lung cancer (NSCLC). Here, we compared the prognostic significances of FDG uptake, and of Glut-1 and Ki-67 expressions in patients with NSCLC.

METHODS

NSCLC patients (n=53, F:M=16:37, age 61.9+/-12.1 years) who underwent curative resection after FDG-PET were enrolled. Thirty-one patients had stage I, 15 stage II, and 7 stage III disease. Patients were treated by surgery only (n=12), surgery plus adjuvant oral chemotherapy (n=32), or surgery plus adjuvant intravenous chemo- or radio-therapy (n=9). Maximum standardized FDG uptake values (maxSUV), and the Glut-1 and Ki-67 expressions of resected tumors were analyzed for correlations and relations with tumor recurrence. The median follow-up duration was 15 months.

RESULTS

Thirteen (24.5%) of the 53 patients experienced recurrence during a median follow-up of 8 months and significant correlations were found between maxSUV, Glut-1, and Ki-67 expressions (r=0.48-0.79, p<0.001). Univariate analysis revealed that disease-free survival (DFS) was significantly correlated with maxSUV (<7 versus > or =7, p=0.001), % Ki-67 expression (<25% versus > or =25%, p=0.047), tumor size (<3 cm versus > or =3 cm, p=0.027), and tumor cell differentiation (well/moderate versus poor, p=0.011). However, multivariate Cox proportional analysis identified maxSUV as the only determinant of DFS (p=0.005). Patients with a maxSUV of > or =7 (n=14) had a significantly lower 1-year DFS rate (57.1%) than those with a maxSUV of <7 (n=39, 89.7%).

CONCLUSION

FDG uptake is more valuable than Glut-1 or Ki-67 expression in terms of predicting prognosis in patients with resected NSCLC.

Optimization of whole-body positron emission tomography imaging by using delayed 2-deoxy-2-[F-18]fluoro-D: -glucose Injection following I.V. Insulin in diabetic patients

PURPOSE

High blood glucose levels may decrease the sensitivity of 2-deoxy-2-[F-18]fluoro-D: -glucose (FDG)-positron emission tomography (PET). The goal of this study was to assess whether intravenous (i.v.) insulin followed by FDG injection 60 minutes later could decrease the blood glucose level of hyperglycemic patients without altering muscular, liver, or lung FDG uptake.

METHODS

We evaluated 53 diabetic patients with a fasting glycemia higher than 7.0 mmol/l. The control group consisted of 53 nondiabetic patients with a normal fasting glycemia. Sixty minutes before FDG injection, all diabetic patients received up to two intravenous bolus of insulin. Regions of interest were drawn over the lungs, heart, liver, skeletal muscles, and over the most active lung nodule, if present, to calculate a standardized uptake value (SUV) normalized to the lean body weight.

RESULTS

After one or two boluses of insulin (mean 3.4 units), 39 diabetic patients decreased their blood glucose level from 9.4 +/- 1.8 to 6.1 +/- 1.3 mmol/l. In 14 patients, two doses of insulin (mean 4.5 +/- 2.3 units) were not sufficient, but managed to decrease the blood glucose level from 10.6 +/- 2.1 to 9.1 +/- 2.1 mmol/l. There was no significant difference for the SUV calculated on the lung, liver, heart, and skeletal muscles. No differences were noted in lung tumor uptake in patients who received insulin compared to the control group.

CONCLUSIONS

With a sufficient waiting period between the insulin and FDG injections, an i.v. bolus of insulin makes it possible to effectively decrease glycemia of diabetic patients without increasing muscular FDG uptake.

Biological correlates of FDG uptake in non-small cell lung cancer

PURPOSE

Each pathological stage of non-small cell lung cancer (NSCLC) consists of a heterogeneous population containing patients at much higher risk than others. Noninvasive functional imaging modalities, such as 18F-fluorodeoxyglucose positron emission tomography (FDG-PET), could play a role in further characterization of NSCLCs. As many factors can influence the extent of FDG uptake, the underlying mechanisms for FDG accumulation in tumors, are still a matter of debate. The aim of the present study was to investigate these possible mechanisms in the primary site of early stage preoperatively untreated NSCLC.

METHODS

19 patients with early stage NSCLC, who had undergone both preoperative FDG-PET imaging and curative surgery, were enrolled in this study. Standardized uptake values (SUVs) were used for evaluation of primary tumor FDG uptake. Final diagnosis, tumor type, tumor cell differentiation and size of the primary tumors were confirmed histopathologically in resected specimens. Histologic sections were analyzed for amount of inflammation and necrosis. Expression of the glucose membrane transporters (GLUT-1 and GLUT-3); the isoforms of the glycolytic enzyme hexokinase (HK-I, HK-II and HK-III); and the cysteine protease caspase-3, was evaluated immunohistochemically.

RESULTS

FDG uptake was significantly higher in squamous cell carcinomas (mean SUV 13.4+/-4.9, n=8) compared to adenocarcinomas (7.1+/-3.3, n=8, p=0.007), or large cell carcinomas (5.9+/-1.9, n=3, p=0.02). The degree of FDG accumulation seemed to depend especially on GLUT-1, GLUT-3 and tumor cell differentiation. The summed standardized values of these three parameters correlated significantly with the SUV (r=0.47, p=0.05).

CONCLUSION

The present study supports the hypothesis that tumor cell differentiation in combination with overexpression of GLUT-1 and GLUT-3 determine the extent of FDG accumulation and that squamous cell carcinomas accumulate more FDG than adenocarcinomas or large cell carcinomas.

FDG uptake and glucose transporter type 1 expression in lymph nodes of non-small cell lung cancer

AIMS

FDG uptake in NSCLC is related to glucose transporter type 1 (Glut-1) expression. Here, we investigated the direct causal relationship between FDG uptake and Glut-1 expression to determine the role of Glut-1 in FDG uptake by malignant and benign lymph nodes (LNs).

METHODS

Fifty-five curative lung resections in 53 NSCLC patients (male:female=36:17, age=62.0+/-11.8 years) were included. Maximum standardized uptake values (maxSUVs) of LNs in preoperative whole body FDG-PET and Glut-1 immunostaining results were compared.

RESULTS

Of 316 pathologically confirmed LNs, 12.3% (39/316) were malignant, and in malignant LNs, FDG positive LNs were no different from FDG negative LNs in terms of size (15.0+/-6.7 mm vs 10.0+/-6.1mm, p>0.05), or in terms of the proportion of LNs occupied by tumor (60.0+/-28.8% vs 39.2+/-38.4%, p>0.05), but had greater percentages of Glut-1 positive cells in tumors (74.1+/-31.8% vs 22.7+/-18.7%, p<0.01), and Glut-1 staining intensities (3.4+/-0.9 vs 1.8+/-1.3, p<0.01). FDG negative malignant LNs featured cytoplasmic Glut-1 expression and adenocarcinoma. Glut-1 staining intensities were found to be significantly correlated with the maxSUVs of malignant LNs (rho=0.516, p<0.05), but the percentages of Glut-1 positive cells in tumors were not (r=0.2072, p>0.05). Analysis of FDG positive benign LNs showed that maxSUV was not correlated with degree of follicular hyperplasia, or Glut-1 expression (p>0.05).

CONCLUSIONS

Intense Glut-1 immunoreactivity was found to be proportionally related to the degree of FDG uptake by malignant LNs in NSCLC. However, the finding that Glut-1 expression in lymphoid hyperplasia showed no correlation with FDG uptake in benign LNs requires further investigation.

Hypoxia in head and neck cancer

A high level of hypoxia in solid tumours is an adverse prognostic factor for the poor outcome of cancer patients following treatment. This review describes the status of research into finding a practical method for measuring hypoxia and treating hypoxic tumours. The application of such methodology would enable the selection of head and neck cancer treatment based on an individual's tumour oxygenation status. This individualization would include the selection not only of surgery or radiotherapy, but also of novel hypoxia-modification strategies.

Gadopentetate dimeglumine and FDG uptake in liver metastases of colorectal carcinoma as determined with MR imaging and PET

PURPOSE

To examine the in vivo relationship between fluorine 18 fluorodeoxyglucose (FDG) uptake, as measured with positron emission tomography (PET), and functional tumor vasculature, as measured with dynamic contrast material-enhanced magnetic resonance (MR) imaging, in patients with liver metastases of colorectal cancer.

MATERIALS AND METHODS

All patients provided written informed consent, and the study was approved by the institutional review board. A total of 26 patients (12 men and 14 women; mean age, 59 years) who were suspected of having liver metastases of histologically proved colorectal cancer and underwent work-up for liver metastasectomy were included. Patients underwent whole-body FDG PET, and tumor-to-nontumor ratio of FDG uptake in metastases was calculated. Dynamic contrast-enhanced MR imaging was performed, and the rate constant k(ep) (s(-1)) of gadopentetate dimeglumine uptake in metastases was determined. Pimonidazole was used to determine tumor hypoxia and vascular density of metastases. To assess the relationship between FDG uptake, rate constant k(ep) of gadopentetate dimeglumine uptake, hypoxic fraction, and vascular density, the Pearson correlation coefficient was calculated.

RESULTS

Negative correlation between tumor-to-nontumor ratio of FDG uptake and rate constant k(ep) was observed (r = -0.421, P = .082). No correlation between tumor hypoxia and tumor-to-nontumor ratio of FDG uptake or rate constant k(ep) was found. A positive correlation was observed between vascular density and rate constant k(ep) (r = 0.458, P = .034) but not between tumor-to-nontumor ratio of FDG uptake.

CONCLUSION

Negative correlation between tumor-to-nontumor ratio of FDG uptake and rate constant k(ep) suggests that lower values of gadopentetate dimeglumine uptake imply an acutely reduced supply of oxygen, which necessitates a higher uptake of glucose to maintain tumor energy levels. The positive correlation of vascular density with rate constant k(ep), but not with tumor-to-nontumor ratio of FDG uptake, emphasizes the potential of dynamic contrast-enhanced MR imaging to enable measurement of tumor vascularity in vivo and its additional value compared with ex vivo methods.

Factors influencing [F-18] 2-fluoro-2-deoxy-D-glucose (F-18 FDG) uptake in melanoma cells: the role of proliferation rate, viability, glucose transporter expression and hexokinase activity

Using human (SK-MEL 23, SK-MEL 24 and G361) and murine (B16) melanoma cell lines, the coregulatory potential of the uptake of the positron emission tomography (PET) tracer, [Fluorine-18] 2-fluoro-2-deoxy-D-glucose (F-18 FDG) has been investigated in relationship to tumor characteristics. Comparative studies among the four melanoma cell lines demonstrated that the lowest FDG uptake in SK-MEL 24 corresponded strongly to the data for DT (population doubling time) and MTT (tetrazolium salt) cell viability as well as hexokinase (HK) activity, but was not related to the glucose transporter 1 (GLUT 1) expression level. Furthermore, the FDG uptake in each melanoma cell line measured by cell cycle kinetics was significantly positively correlated to both the proliferation index (PI=S/G2M phase fractions) and the cell viability, though with one exception relating to the PI of the lowest FDG uptake cell line, SK-MEL 24. No positive correlation was found between the expression of GLUT 1 and FDG uptake in any individual cell line. However, the HK activities in SK-MEL 23 and 24 showed considerable positive relationships with FDG uptake. Our present study suggests that both the proliferation rate and the cell viability of melanoma cells may be key factors for FDG uptake and that HK activity, rather than GLUT 1 expression, seems to be a major factor.

Dependence of FDG uptake on tumor microenvironment

PURPOSE

To investigate the factors affecting the (18)F-fluorodeoxyglucose ((18)F-FDG) uptake in tumors at a microscopic level, by correlating it with tumor hypoxia, cellular proliferation, and blood perfusion.

METHODS AND MATERIALS

Nude mice bearing Dunning prostate tumors (R3327-AT) were injected with (18)F-FDG and pimonidazole, bromodeoxyuridine, and, 1 min before sacrifice, with Hoechst 33342. Selected tumor sections were imaged by phosphor plate autoradiography, while adjacent sections were used to obtain the images of the spatial distribution of Hoechst 33342, pimonidazole, and bromodeoxyuridine. The images were co-registered and analyzed on a pixel-by-pixel basis.

RESULTS

Statistical analysis of the data obtained from these tumors demonstrated that (18)F-FDG uptake was positively correlated with pimonidazole staining intensity in each data set studied. Correlation of FDG uptake with bromodeoxyuridine staining intensity was always negative. In addition, FDG uptake was always negatively correlated with the staining intensity of Hoechst 33342.

CONCLUSIONS

For the Dunning prostate tumors studied, FDG uptake was always positively correlated with hypoxia and negatively correlated with both cellular proliferation and blood flow. Therefore, for the tumor model studied, higher FDG uptake is indicative of tumor hypoxia, but neither blood flow nor cellular proliferation.

Evaluation of F-18-labeled amino acid derivatives and [18F]FDG as PET probes in a brain tumor-bearing animal model

2-Deoxy-2-[(18)F]fluoro-d-glucose ([(18)F]FDG) has been extensively used as positron emission tomography (PET) tracer in clinical tumor imaging. This study compared the pharmacokinetics of two (18)F-labeled amino acid derivatives, O-2-[(18)F]fluoroethyl-l-tyrosine (l-[(18)F]FET) and 4-borono-2-[(18)F]fluoro-l-phenylalanine-fructose (l-[(18)F]FBPA-Fr), to that of [(18)F]FDG in an animal brain tumor model.

METHODS

A self-modified automated PET tracer synthesizer was used to produce no-carrier-added (nca) l-[(18)F]FET. The cellular uptake, biodistribution, autoradiography and microPET imaging of l-[(18)F]FET, l-[(18)F]FBPA-Fr and [(18)F]FDG were performed with F98 glioma cell culture and F98 glioma-bearing Fischer344 rats.

RESULTS

The radiochemical purity of l-[(18)F]FET was >98% and the radiochemical yield was 50% in average of 16 runs. The uptake of l-[(18)F]FET and l-[(18)F]FBPA-Fr in the F98 glioma cells increased rapidly for the first 5 min and reached a steady-state level after 10 min of incubation, whereas the cellular uptake of [(18)F]FDG kept increasing during the study period. The biodistribution of l-[(18)F]FET, l-[(18)F]FBPA-Fr and [(18)F]FDG in the brain tumors was 1.26+/-0.22, 0.86+/-0.08 and 2.77+/-0.44 %ID/g at 60 min postinjection, respectively, while the tumor-to-normal brain ratios of l-[(18)F]FET (3.15) and l-[(18)F]FBPA-Fr (3.44) were higher than that of [(18)F]FDG (1.44). Both microPET images and autoradiograms of l-[(18)F]FET and l-[(18)F]FBPA-Fr exhibited remarkable uptake with high contrast in the brain tumor, whereas [(18)F]FDG showed high uptake in the normal brain and gave blurred brain tumor images.

CONCLUSION

Both l-[(18)F]FET and l-[(18)F]FBPA-Fr are superior to [(18)F]FDG for the brain tumor imaging as shown in this study with microPET.