18F-FDG uptake in primary gastric malignant lymphoma correlates with glucose transporter 1 expression and histologic malignant potential. Int J Hematol. 2013;97:43-49. [PMID: 23212465 DOI: 10.1007/s12185-012-1225-4]

Is There a Role for [18F]FDG PET-CT in Staging MALT Lymphoma?

Simple Summary

MALT lymphoma represents a relatively rare lymphoma subtype that arises in different extranodal anatomic locations. In the current paper we summarize our experience in assessing disease extent and metabolic characteristics of MALT lymphomas with [¹⁸F]FDG PET-CT at staging, and aim to highlight the strengths and challenges this imaging modality poses. In our data, all extranodal lesions located in subcutaneous-tissue, lung and liver were detected on PET, while some of those located in other tissues (such as along the digestive tract) were not detected on PET. We also evaluated the predictive role of PET in these patients, and found that increased [¹⁸F]FDG-uptake in extranodal lesions was associated with worse disease progression.

Abstract

The role of ¹⁸F-fluorodeoxyglucose ([¹⁸F]FDG) positron emission tomography—computed tomography (PET-CT) in assessing mucosa-associated lymphoid tissue (MALT) lymphoma is debatable. We retrospectively explored the role of [¹⁸F]FDG PET-CT in staging and predicting progression-free-survival (PFS) of patients with newly-diagnosed MALT lymphoma. Sixty-six studies were included. The maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV) and total lesion glycolysis (TLG) were documented in the “hottest” extranodal and nodal lesions. Extranodal lesions and accompanying nodal disease were detected on PET in 38/66 (57.6%) and 13/66 (19.7%) studies, respectively. Detection rate of extranodal lesions differed significantly between those located in tissues with high/heterogeneous (e.g., stomach) vs low/homogenous (e.g., subcutaneous-tissue, lung) physiologic [¹⁸F]FDG-uptake (40.4% vs. 100%, p < 0.01). Nodal lesions had significantly lower SUVmax, MTV and TLG compared with extrandodal lesions in the same patients. Detection and [¹⁸F]FDG-avidity of extranodal lesions were higher in patients with advanced, bulky disease and concomitant marrow/nodal involvement. Increased SUVmax of extranodal lesions predicted shorter PFS (HR 1.10, 95% CI 1.01–1.19, p = 0.02). Higher SUVmax and TLG showed trends towards shorter PFS in patients with localized disease. In conclusion, detection rate of extranodal MALT lymphoma lesions located in tissues with low/homogeneous physiologic [¹⁸F]FDG-uptake is excellent on [¹⁸F]FDG PET-CT. When detected, SUVmax of extranodal lesions may predict PFS.

Gastric Cancer Stem Cells: A Glimpse on Metabolic Reprogramming

Gastric cancer (GC) is one of the most widespread causes of cancer-related death worldwide. Recently, emerging implied that gastric cancer stem cells (GCSCs) play an important role in the initiation and progression of GC. This subpopulation comprises cells with several features, such as self-renewal capability, high proliferating rate, and ability to modify their metabolic program, which allow them to resist current anticancer therapies. Metabolic pathway intermediates play a pivotal role in regulating cell differentiation both in tumorigenesis and during normal development. Thus, the dysregulation of both anabolic and catabolic pathways constitutes a significant opportunity to target GCSCs in order to eradicate the tumor progression. In this review, we discuss the current knowledge about metabolic phenotype that supports GCSC proliferation and we overview the compounds that selectively target metabolic intermediates of CSCs that can be used as a strategy in cancer therapy.

Positron emission tomography and magnetic resonance imaging in primary central nervous system lymphoma-a narrative review

This review addresses the challenges of primary central nervous system (CNS) lymphoma diagnosis, assessment of treatment response, and detection of recurrence. Primary CNS lymphoma is a rare form of extra-nodal non-Hodgkin lymphoma that can involve brain, spinal cord, leptomeninges, and eyes. Primary CNS lymphoma lesions are most commonly confined to the white matter or deep cerebral structures such as basal ganglia and deep periventricular regions. Contrast-enhanced magnetic resonance imaging (MRI) is the standard diagnostic modality employed by neuro-oncologists. MRI often shows common morphological features such as a single or multiple uniformly well-enhancing lesions without necrosis but with moderate surrounding edema. Other brain tumors or inflammatory processes can show similar radiological patterns, making differential diagnosis difficult. [18F]-fluorodeoxyglucose (FDG) positron emission tomography (PET) has selected utility in cerebral lymphoma, especially in diagnosis. Primary CNS lymphoma can sometimes present with atypical findings on MRI and FDG PET, such as disseminated disease, non-enhancing or ring-like enhancing lesions. The complementary strengths of PET and MRI have led to the development of combined PET-MR systems, which in some cases may improve lesion characterization and detection. By highlighting active developments in this field, including advanced MRI sequences, novel radiotracers, and potential imaging biomarkers, we aim to spur interest in sophisticated imaging approaches.

Prognostic Impact of Pretreatment 2-[18F]-FDG PET/CT Parameters in Primary Gastric DLBCL

Background and Objectives: Primary gastric diffuse large-B cell lymphoma (DLBCL) is an aggressive lymphoma subtype with high ¹⁸F-FDG avidity but unclear criteria for 2-[¹⁸F]-FDG PET/CT in the evaluation of treatment response and prognostication. Our aim was to investigate whether the pretreatment 2-[¹⁸F]-FDG PET/CT variables may predict treatment response (at end of first-line therapy) and prognosis in primary gastric DLBCL. Materials and Methods: we included 57 patients with a diagnosis of primary gastric DLBCL and a baseline 2-[¹⁸F]-FDG PET/CT and an end of treatment PET/CT after 6 cycles of R-CHOP chemotherapy. We analyzed PET images qualitatively and semi-quantitatively by deriving the maximum standardized uptake value body weight (SUVbw), the maximum standardized uptake value lean body mass (SUVlbm), the maximum standardized uptake value body surface area (SUVbsa), lesion to liver SUVmax ratio (L-L SUV R), lesion to blood-pool SUVmax ratio (L-BP SUV R), metabolic tumor volume and total lesion glycolysis of gastric lesion (gMTV and gTLG), and total MTV (tMTV) and TLG. Survival curves were plotted according to the Kaplan–Meier analysis. Results: at a median follow up of 80 months, the median PFS and OS were 69 and 80 months. Baseline gMTV, gTLG, tMTV, and TLG were significantly higher in patients with incomplete response (partial response and progression) compared to complete response group. tMTV and TLG were confirmed to be independent prognostic factors both for PFS (p = 0.023 and p = 0.038) and OS (p = 0.038 and p = 0.026); instead, the other metabolic parameters were not related to outcome survival. Conclusions: high tMTV and TLG were significantly correlated with shorter survival (PFS and OS) and may predict incomplete response after therapy.

Carbonic Anhydrase Inhibitor Acetazolamide Enhances CHOP Treatment Response and Stimulates Effector T-Cell Infiltration in A20/BalbC Murine B-Cell Lymphoma

The inhibition of cancer-related carbonic anhydrase (CA) activity is a promising way to intensify anti-tumor responses. In vitro data suggest improved efficacy of cytotoxic drugs in combination with CA-inhibitors in several cancer types. Despite accumulating data on CA-expression, experimental or clinical studies towards B-cell lymphoma therapy are missing. We therefore decided to test the effect of the CA-inhibitor acetazolamide (AA) on the conventional CHOP treatment regimen using the A20/BalbC in vivo syngeneic mouse lymphoma model. Tumor growth characteristics, 18F-MISO-PET activity, histomorphology, cell proliferation, and T-cell immune infiltrate were determined following single or multiple dose combinations. All results point to a significant increase in the anti-tumor effect of CHOP+AA combinations compared with the untreated controls or with the single CHOP or AA treatments. CD3+ and CD8+ T-cell immune infiltrate increased 3–4 times following CHOP+AA combination compared with the classical CHOP protocol. In conclusion, CA-inhibitor AA seems to act synergistically with the anti-tumor treatment CHOP in aggressive lymphoma. Further to a cytotoxic effect, AA and other more selective blockers potentially support tumor-associated immune responses through the modification of the microenvironment. Therefore, CA-inhibitors are promising candidates as adjuvants in support of specific immunotherapies in lymphoma and other malignancies.

Sustain, Adapt, and Overcome-Hypoxia Associated Changes in the Progression of Lymphatic Neoplasia

Irregular perfusion and related tissue hypoxia is a common feature of solid tumors the role of which in the survival and progression cancer has been gradually recognized. Adaptation and selection mechanisms in hypoxic areas in solid tumors are regulated by Hypoxia Inducible transcriptional factor 1 (HIF1) and other hypoxia mediators and are associated with aggressive clinical behavior in a large spectrum of malignancies. Aggressive forms of lymphatic neoplasias present with solid tumor-like features, also including rapid cell growth, necrosis and angiogenesis, the clinical potential of which is still underestimated. While the role of regional hypoxia in normal B-cell maturation and malignant transformation is becoming evident, the impact of tissue hypoxia on their behavior is not well-understood. Compared to some of the common solid cancer types data for some of the key regulators, such as HIF1 and HIF2, and for their downstream effectors are available in a limited fashion. In the current review we aim to overview the physiological aspects of major hypoxia pathways during B-cell maturation and adaptation-related changes reported in lymphatic neoplasia covering important targets, such as carbonic anhydrases IX and XII (CAIX, CAXII), glucose transporter 1 (GLUT-1) and vascular endothelial growth factor (VEGF). In conclusion, experimental and clinical results direct to important but currently unexploited role of hypoxia-driven resistance mechanisms especially in aggressive forms of B-cell neoplasia.

18F-FDG PET/CT or PET Role in MALT Lymphoma: An Open Issue not Yet Solved-A Critical Review

Mucosa-associated lymphoid tissue (MALT) lymphoma involves the mucosa-associated lymphoid tissue potentially arising from any mucosal site, with the stomach as the most common site of involvement. MALT lymphoma is not usually an aggressive disease with a good prognosis except for selected cases. Fluorine-18 (¹⁸F) fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) is a noninvasive imaging tool used for staging, restaging, and evaluation of the treatment response in non-Hodgkin and Hodgkin lymphoma. However, its effective role in MALT lymphoma is not yet clear. The open question is whether these lymphomas are ¹⁸F-FDG avid or not, with conflicting results reported in the literature. Consequently, the possible clinical role of ¹⁸F-FDG PET/CT for staging and restaging purposes is under debate. The aim of the present review was to analyze the reported data about the role of ¹⁸F-FDG PET or PET/CT in patients with MALT lymphoma. We performed a comprehensive computer literature search of the Scopus, Cochrane, PubMed/MEDLINE, and Embase databases, including articles reported up to August 2019. We included 32 studies that had analyzed ¹⁸F-FDG PET or PET/CT for patients with MALT lymphoma. We analyzed the metabolic behavior of MALT lymphoma using ¹⁸F-FDG PET and the effect of the PET findings in the staging, treatment response evaluation, and prognosis.

18F-FDG PET/CT in splenic marginal zone lymphoma

PURPOSE

The detection rate and the metabolic behavior of 18F-FDG-PET/CT in splenic marginal zone lymphoma (SMZL) are not yet clear. Our aim was to investigate the metabolic behavior of SMZL and whether the tumor stage (acc. Ann Arbor) epidemiological (age, gender), histological (Ki-67 index, plasmacytic differentiation), and morphological (splenic diameter maximum) features might be related to 18F-FDG PET/CT results.

METHODS

Fifty-one patients (34 male, 17 female; average age 70 years) with histologically confirmed SMZL who underwent a 18F-FDG PET/CT for initial staging were included: PET/CT images were analyzed visually and semi-quantitatively (SUVmax, lesion-to-liver SUVmax ratio, and lesion-to-blood pool SUVmax ratio). Splenic uptake was divided as diffuse or focal.

RESULTS

Thirty-nine patients (76%) had FDG-avid SMZL (7 with focal splenic lesions and 32 with diffuse splenic uptake), while the remaining 12 had no increased splenic uptake. Among patients with FDG-avid lesions, average SUVmax was 4.3, lesion-to-liver SUVmax ratio 2.3, and lesion-to-blood pool SUVmax ratio 3. 18F-FDG avidity was significantly associated with Ki-67 index and not correlated with other features. Semiquantitative PET/CT parameters (SUVmax, lesion-to-liver SUVmax ratio, and lesion-to-blood pool SUVmax ratio) did not correlate significantly with any variable. Progression-free survival time was not influenced by FDG avidity of SMZL.

CONCLUSIONS

18F-FDG avidity was noted in 76% of SMZL with diffuse splenic uptake as main pattern of presentation and is correlated with Ki-67 score only.

Glucose transporters in cancer - from tumor cells to the tumor microenvironment

Solute carriers of the glucose transporter (GLUT) family mediate the first step for cellular glucose usage. The upregulation of GLUTs has been reported in numerous cancer types as a result of perturbation of gene expression or protein relocalization or stabilization. Because they enable to sustain the energy demand required by tumor cells for various biochemical programs, they are promising targets for the development of anticancer strategies. Recently, important biological insights have come from the fine crystal structure determination of several GLUTs; these advances will likely catalyze the development of new selective inhibitory compounds. Furthermore, deregulated glucose metabolism of nontumor cells in the tumor mass is beginning to be appreciated and could have major implications for our understanding of how glucose uptake by specific cell types influences the behavior of neighboring cells in the same microenvironment. In this review, we discuss some of the deregulation mechanisms of glucose transporters, their genetic and pharmacological targeting in cancer, and new functions they may have in nontumor cells of the tumor environment or beyond glucose uptake for glycolysis.

18F-FDG PET/CT in gastric MALT lymphoma: a bicentric experience

PURPOSE

The role of 18F-FDG-PET/CT in evaluating gastric MALT lymphoma is still controversial. In the literature the detection rate of 18F-FDG-PET/CT in patients with gastric MALT lymphoma is variable, and the reason for this heterogeneity is not still clear. Our aim was to investigate the particular metabolic behavior of these lymphoma.

MATERIALS AND METHODS

Sixty-nine patients (26 female, 43 male) with histologically confirmed gastric MALT lymphoma who underwent a 18F-FDG-PET/CT for initial staging from two centers were included. The PET images were analyzed visually and semi-quantitatively by measuring the maximum standardized uptake value (SUVmax), lesion-to-liver SUVmax ratio, and lesion-to-blood pool SUVmax ratio and compared with Ann Arbor stage, epidemiological (age, sex), histological (presence of gastritis, ulcer, H. pylori infection, plasmacytic differentiation, Ki-67 index), and morphological (tumor size, superficial lesions or mass-forming) characteristics.

RESULTS

Thirty-six patients (52 %) had positive PET/CT (average SUVmax was 9±6.7; lesion-to-liver SUVmax ratio 3.7±2.6, lesion-to-blood pool SUVmax ratio 4.8±3.3) at the corresponding gastric lesion; the remaining 33 were not 18F-FDG-avid. In the univariate analysis, 18F-FDG avidity was significantly associated with morphological features (mass forming p<0.001 and high maximum diameter p<0.001), Ann Arbor stage (p=0.010), and Ki67 index (p<0.001) and not correlated with age, sex, presence of gastritis, ulcer, Helicobacter pylori infection, and plasmacytic differentiation. In the multivariate analysis, the correlations with gross morphological appearance, Ann Arbor stage, and Ki-67 score were confirmed. SUVmax, lesion-to-liver SUVmax ratio, and lesion-to-blood pool SUVmax ratio correlated significantly only with Ki67 index (p=0.047; p=0.012; p=0.042).

CONCLUSIONS

18F-FDG avidity was noted in 52 % of gastric MALT lymphoma and this avidity is correlated with gross morphological characteristics, tumor stage, and Ki-67 index. SUVmax, lesion-to-liver SUVmax ratio, and lesion-to-blood pool SUVmax ratio are correlated only with Ki-67 index, and only lesion-to-liver SUVmax ratio was independently associated with Ki-67 score.

Preoperative evaluation of renal cell carcinoma by using 18F-FDG PET/CT

PURPOSE

This study aimed to characterize the FDG uptake of renal cell carcinoma (RCC) by the pathological subtype and nuclear grade.

PATIENTS AND METHODS

We retrospectively identified patients who underwent F-FDG PET and subsequent partial or radical nephrectomy for renal tumors. The relationships of the SUV of renal tumor with subtypes, nuclear grade, and clinicopathological variables were investigated.

RESULTS

Ninety-two tumors were analyzed, including 52 low-grade (G1 and G2) and 18 high-grade (G3 and G4) clear cell RCC; 7 chromophobe, 5 papillary, and 1 unclassified RCC; and 9 benign tumors (7 angiomyolipoma and 2 oncocytoma). The SUVs of high-grade clear cell RCC (mean ± SD, 6.8 ± 5.1) and papillary RCC (6.6 ± 3.7) were significantly higher than that of the controls (2.2 ± 0.3). The SUV of high-grade clear cell RCC was higher than that of low-grade tumors (median, 4.0 vs. 2.2; P < 0.001). The optimal SUV cutoff value of 3.0 helped to differentiate high-grade from low-grade clear cell RCC, with 89% sensitivity and 87% specificity. On multiple regression analysis, a high grade was the most significant predictor of SUV for clear cell RCC.

CONCLUSIONS

FDG uptake higher than that observed in normal kidney tissues suggests a high-grade clear cell RCC or papillary RCC subtype. FDG-PET using SUV may have a role in prediction of pathological grade of renal tumor.

Dual time-point FDG PET/CT and FDG uptake and related enzymes in lymphadenopathies: preliminary results

PURPOSE

The purpose of this study was to determine the ability of dual time-point (DTP) PET/CT with (18)F-FDG to discriminate between malignant and benign lymphadenopathies. The relationship between DTP FDG uptake and glucose metabolism/hypoxia markers in lymphadenopathies was also assessed.

METHODS

Patients with suspected lymphoma or recently diagnosed treatment-naive lymphoma were prospectively enrolled for DTP FDG PET/CT (scans 60 min and 180 min after FDG administration). FDG-avid nodal lesions were segmented to yield volume and standardized uptake values (SUV), including SUVmax, SUVmean, cSUVmean (with partial volume correction), total lesion glycolysis (TLG) and cTLG (with partial volume correction). Expression of glucose transporter-1 (GLUT-1), hexokinase-II (HK-II), glucose-6-phosphatase (G6Pase) and hypoxia-inducible factor-1alpha (HIF-1alpha) were assessed with immunohistochemistry and enzyme activity was determined for HK and G6Pase.

RESULTS

FDG uptake was assessed in 203 lesions (146 malignant and 57 benign). Besides volume, there were significant increases over time for all parameters, with generally higher levels in the malignant lesions. The retention index (RI) was not able to discriminate between malignant and benign lesions. Volume, SUVmax, TLG and cTLG for both scans were able to discriminate between the two groups statistically, but without complete separation. Glucose metabolism/hypoxia markers were assessed in 15 lesions. TLG and cTLG were correlated with GLUT-1 expression on the 60-min scan. RI-max and RI-mean and SUVmax, SUVmean and cSUVmean on the 60-min scan were significantly correlated with HK-II expression.

CONCLUSION

RI was not able to discriminate between malignant and benign lesions, but some of the SUVs were able to discriminate on the 60-min and 180-min scans. Furthermore, FDG uptake was correlated with GLUT-1 and HK-II expression.

Glucose metabolism in gastric cancer: The cutting-edge

Glucose metabolism in gastric cancer cells differs from that of normal epithelial cells. Upregulated aerobic glycolysis (Warburg effect) in gastric cancer meeting the demands of cell proliferation is associated with genetic mutations, epigenetic modification and proteomic alteration. Understanding the mechanisms of aerobic glycolysis may contribute to our knowledge of gastric carcinogenesis. Metabolomic studies offer novel, convenient and practical tools in the search for new biomarkers for early detection, diagnosis, prognosis, and chemosensitivity prediction of gastric cancer. Interfering with the process of glycolysis in cancer cells may provide a new and promising therapeutic strategy for gastric cancer. In this article, we present a brief review of recent studies of glucose metabolism in gastric cancer, with primary focus on the clinical applications of new biomarkers and their potential therapeutic role in gastric cancer.

Assessment of cell proliferation in renal cell carcinoma using dual-phase 18F-fluorodeoxyglucose PET/CT

The present study aimed to examine the association between ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake and cell proliferation markers; in addition, the correlation between ¹⁸F-FDG uptake and biological characteristic in patients with renal cell carcinoma (RCC) was investigated using dual-phase ¹⁸F-FDG-positron emission tomography/computed tomography (PET/CT). Dual-phase ¹⁸F-FDG PET/CT was performed on 31 RCC patients and the maximum standardized uptake values at 1 h (SUV1) and 2 h (SUV2) as well as the retention index (RI; %) in the primary tumors were calculated. Monoclonal antibodies for Ki-67, minichromosome maintenance 2 (MCM2) and topoisomerase II α (topo II α) were used to assess the expression levels of their respective proteins in excised tumor tissue using immunohistochemistry. The results demonstrated that RI and SUV2 in patients with Stage I/II + grade 1 (G1) RCC were significantly decreased compared with all patients with other stages/grades (RI, P=0.0065; SUV2, P=0.043); in addition, significantly increased uptake and RI were detected in patients with metastases compared with patients without metastases (SUV1, P=0.029; SUV2, P=0.0003; RI, P<0.001). All proliferation markers significantly correlated with RI (Ki-67, r=0.501, P=0.004; MCM2, r=0.359, P=0.047; topo II α, r=0.402, P=0.024), while SUV1 and SUV2 correlated with Ki-67 only. In conclusion, the results of the present study demonstrated that dual-phase ¹⁸F-FDG-PET/CT was more useful for predicting cell proliferation in RCC compared with single-phase imaging alone. However, follow-ups are required in order to determine whether dual-phase ¹⁸F-FDG-PET/CT provides independent prognostic information.

Correlation between in vivo 18F-FDG PET and immunohistochemical markers of glucose uptake and metabolism in pheochromocytoma and paraganglioma

Pheochromocytomas and paragangliomas (PPGLs) can be localized by (18)F-FDG PET. The uptake is particularly high in tumors with an underlying succinate dehydrogenase (SDH) mutation. SDHx-related PPGLs are characterized by compromised oxidative phosphorylation and a pseudohypoxic response, which mediates an increase in aerobic glycolysis, also known as the Warburg effect. The aim of this study was to explore the hypothesis that increased uptake of (18)F-FDG in SDHx-related PPGLs is reflective of increased glycolytic activity and is correlated with expression of different proteins involved in glucose uptake and metabolism through the glycolytic pathway.

METHODS

Twenty-seven PPGLs collected from patients with hereditary mutations in SDHB (n = 2), SDHD (n = 3), RET (n = 5), neurofibromatosis 1 (n = 1), and myc-associated factor X (n = 1) and sporadic patients (n = 15) were investigated. Preoperative (18)F-FDG PET/CT studies were analyzed; mean and maximum standardized uptake values (SUVs) in manually drawn regions of interest were calculated. The expression of proteins involved in glucose uptake (glucose transporters types 1 and 3 [GLUT-1 and -3, respectively]), phosphorylation (hexokinases 1, 2, and 3 [HK-1, -2, and -3, respectively]), glycolysis (monocarboxylate transporter type 4 [MCT-4]), and angiogenesis (vascular endothelial growth factor [VEGF], CD34) were examined in paraffin-embedded tumor tissues using immunohistochemical staining with peroxidase-catalyzed polymerization of diaminobenzidine as a read-out. The expression was correlated with corresponding SUVs.

RESULTS

Both maximum and mean SUVs for SDHx-related tumors were significantly higher than those for sporadic and other hereditary tumors (P < 0.01). The expression of HK-2 and HK-3 was significantly higher in SDHx-related PPGLs than in sporadic PPGLs (P = 0.022 and 0.025, respectively). The expression of HK-2 and VEGF was significantly higher in SDHx-related PPGLs than in other hereditary PPGLs (P = 0.039 and 0.008, respectively). No statistical differences in the expression were observed for GLUT-1, GLUT-3, and MCT-4. The percentage anti-CD 34 staining and mean vessel perimeter were significantly higher in SDHx-related PPGLs than in sporadic tumors (P = 0.050 and 0.010, respectively). Mean SUVs significantly correlated with the expression of HK-2 (P = 0.027), HK-3 (P = 0.013), VEGF (P = 0.049), and MCT-4 (P = 0.020).

CONCLUSION

The activation of aerobic glycolysis in SDHx-related PPGLs is associated with increased (18)F-FDG accumulation due to accelerated glucose phosphorylation by hexokinases rather than increased expression of glucose transporters.

Correlation between positron emission tomography findings and glucose transporter 1, 3 and L-type amino acid transporter 1 mRNA expression in primary central nervous system lymphomas

Primary central nervous system lymphoma (PCNSL) is an aggressive form of non-Hodgkin lymphoma with a poor prognosis. [¹⁸F] 2-fluoro-2-deoxy-D-glucose (FDG) and L-(methyl-¹¹C)-methionine (MET) are the most widely used tracers in oncological positron emission tomography studies for PCNSL and commonly identify hypermetabolic lesions through increased uptake of FDG and MET. However, the mechanisms underlying the uptake of FDG and MET in PCNSL have not been clearly determined. The present study aimed to investigate the mRNA expression levels of glucose transporter (GLUT)1, GLUT3 and L-type amino acid transporter 1 (LAT1) in resected PCNSL specimens, in order to identify whether these transporters are associated with the increased uptake of FDG and MET. A total of 7 patients diagnosed with PCNSL were investigated. The uptake of FDG and MET by the tumors was evaluated based on the maximum standardized uptake value (SUVmax). The quantity of GLUT1, GLUT3 and LAT1 mRNA in the PCNSL specimens was measured to determine whether GLUT1, GLUT3 and/or LAT1 are involved in the increased uptake of FDG and MET in PCNSL. Furthermore, microvessel density (MVD) and cell density (CD) were measured in all the cases. Our results indicated that the expression of GLUT3, but not GLUT1, was significantly correlated with FDG SUVmax and the expression of LAT1 was significantly correlated with MET SUVmax. However, neither MVD nor CD were found to be significantly associated with the uptake of FDG and MET. GLUT3 was identified as a key determinant of FDG accumulation, whereas LAT1 was a key determinant of MET accumulation in PCNSL. Therefore, GLUT3 and LAT1 may represent potential targets for the future development of novel therapeutic agents for PCNSL.

Diagnosis and evaluation of gastric cancer by positron emission tomography

Gastric cancer is the second leading cause of cancer mortality worldwide. The diagnosis of gastric cancer has been significantly improved with the broad availability of gastrointestinal endoscopy. Effective technologies for accurate staging and quantitative evaluation are still in demand to merit reasonable treatment and better prognosis for the patients presented with advanced disease. Preoperative staging using conventional imaging tools, such as computed tomography (CT) and endoscopic ultrasonography, is inadequate. Positron emission tomography (PET), using ¹⁸F-fluorodeoxyglucose (FDG) as a tracer and integrating CT for anatomic localization, holds a promise to detect unsuspected metastasis and has been extensively used in a variety of malignancies. However, the value of FDG PET/CT in diagnosis and evaluation of gastric cancer is still controversial. This article reviews the current literature in diagnosis, staging, response evaluation, and relapse monitoring of gastric cancer, and discusses the current understanding, improvement, and future prospects in this area.