Synthesis and Evaluation of [18F]SiFA-Conjugated Ligands for Fibroblast Activation Protein Imaging.

In recent years, fibroblast activation protein (FAP) has emerged as an important target for the diagnosis and therapy of various tumors due to its high expression on the cell surface of cancer-associated fibroblasts, which are the major components of the tumor stroma. In this study, we synthesized and evaluated 18F-labeled FAP inhibitors (FAPIs) for FAP imaging. Two silicon fluoride acceptor (SiFA)-conjugated FAPIs were synthesized: one containing a γ-carboxy-l-glutamic acid (Gla) residue (1) and another containing two Gla residues (2). Both ligands exhibited high binding affinities for FAP. 18F/19F exchange reactions on both ligands were performed in the presence of 2% water. This resulted in the formation of radioligands [18F]1 and [18F]2 in high radiochemical yields. Radioligand [18F]2, with a more favorable partition coefficient, was selected for the U87MG cell binding study, and the results showed FAP-specific binding of the radioligand to the cells. An ex vivo biodistribution study in U87MG tumor-bearing mice 60 min after injection demonstrated a 5.8-fold higher tumor accumulation of [18F]2 than that of [18F]1. Furthermore, PET and ex vivo biodistribution studies of [18F]2 in U87MG tumor-bearing mice showed high and persistent tumor uptake over time, which was significantly blocked by the preinjection of FAPI-04. Our results indicate that [18F]SiFA-(Gla)2-conjugated FAPI ([18F]2) has the potential for FAP imaging.

Enzyme-responsive macrocyclic metal complexes for biomedical imaging.

Metal chelator-based contrast agents are used as tumor navigators for cancer diagnosis. Although approved metal chelators show excellent contrast performance in magnetic resonance imaging (MRI), large doses are required for cancer diagnoses due to rapid clearance and nonspecific accumulation throughout the body, which can compromise safety. The present study describes an enzyme-responsive metal delivery system, in which enzyme overexpressed in the tumor microenvironment selectively activates the tumor uptake of gadolinium (Gd). Gd was loaded into enzyme-responsive macrocyclam (ErMC) modified with a PEGylated enzyme-cleavable peptide resulting in Gd@ErMC. The PEGylated shell layer protected Gd@ErMC from nonspecific binding in the blood, increasing the half-life of the contrast agent. Specific cleavage of the PEGylated shell layer by the enzyme selectively liberated Gd from Gd@ErMC at the tumor site. Evaluation of the in vivo distribution of Gd@ErMC in tumor-bearing mice by MRI and positron emission tomography (PET) showed that Gd@ErMC had an extended half-life and was highly specific. Histological and serological analysis of Gd@ErMC-treated mice showed that this agent was safe. This novel enzyme-responsive contrast agent delivery system shows promise as specific theranostic agent for MR-guided radiotherapy.

Methionine metabolism and endocrine function of the pituitary gland in patients with suprasellar germinoma.

PURPOSE: The aim of this study was to investigate the association between methionine (MET) metabolism and endocrine function of the pituitary gland in patients with suprasellar region tumor. MATERIALS AND METHODS: Twenty patients with intracranial germinoma were included in this study. Initial staging and all surveillance MET PET/CT scans and comparable serum levels of follicle stimulating hormone (FSH), luteinizing hormone (LH), and thyroid stimulating hormone (TSH) were analyzed. The patients were divided into two groups according to tumor location, with tumors in the suprasellar region (condition) or not (control). MET uptake of the pituitary gland (i.e., SUVR [standardized uptake value ratio]) and levels of FSH, LH, TSH were compared in the condition and control groups and in the before and after treatment phases of each group. RESULTS: The SUVR in the control group was like that found in normal pituitary glands in previous studies, whereas the SUVR of the untreated condition group was high and that of treated condition group was low with significance compared to the control group. Serum levels of pituitary hormones in before and after treatment condition groups were significantly lower than those in the control group. The FSH and LH levels of curatively treated patients in the control group were positively correlated with SUVR with respective ß values of 3.71 and 0.98 (p < .001). The TSH level of the treated condition group was negatively correlated with SUVR (ß = -1.02, p < .001). CONCLUSION: This study is the first known investigation to examine the association between MET metabolism and endocrine function of the pituitary gland, and it confirmed that MET metabolism reflects endocrine function. A future study validating the result of correlation analysis is warranted.

A High-Affinity 64Cu-Labeled Ligand for PET Imaging of Hepsin: Design, Synthesis, and Characterization.

Hepsin, a cell surface serine protease, is a potential biomarker for the detection of prostate cancer due to its high expression in prostate cancer but not in normal prostate. This study aimed to develop a radioligand for positron emission tomography (PET) imaging of hepsin. Six leucine-arginine (Leu-Arg) dipeptide derivatives (two diastereomers for each of three ligands) were synthesized and evaluated for their binding affinities and selectivity for hepsin. Based on the binding assay, a natCu-1,4,7,10-tetraazacyclododecane-N,N',N″,N‴-tetraacetic acid (DOTA)-conjugated ligand (3B) was selected for the development of a PET radioligand. [64Cu]3B was synthesized by labeling the DOTA-conjugated compound 11B with [64Cu]CuCl2 at 80 °C for 20 min. The radioligand was evaluated for prostate cancer cell binding and PET imaging in a prostate tumor mouse model. The results demonstrated that [64Cu]3B exhibited high binding to LNCaP cells, intermediate binding to 22Rv1 cells, and low binding to PC3 cells. PET studies of [64Cu]3B in mice, implanted with 22Rv1 and PC3 cells on each flank, revealed that the radioligand uptake was high and persistent in the 22Rv1 tumors over time, whereas it was low in PC3 tumors. The results of this study suggest that [64Cu]3B is a promising PET radioligand for hepsin imaging.

Value of C-11 methionine PET/CT in patients with intracranial germinoma.

PURPOSE: The purpose of this study was to investigate the value of C-11 methionine (MET) positron emission tomography (PET)/computed tomography (CT) in patients with intracranial germinoma (IG). MATERIAL AND METHODS: We conducted a retrospective analysis of 21 consecutive patients with pathologically confirmed IGs and eight patients with intracranial non-germinomas (INGs) located in a similar region. Clinical characteristics, imaging findings, and tumor markers such as α-fetoprotein (AFP) and ß-human chorionic gonadotropin (HCG) were used as clinical variables. Maximum standardized uptake value (SUVmax), tumor-to-normal tissue (T/N) ratio, and visual scoring of tumor were used as MET PET parameters. RESULTS: All IGs were well visualized on MET PET with a three-grade visual scoring system. In addition, SUVmax of IGs was higher than that of INGs (P = 0.005). Pre-treatment (Pre-Tx) T/N ratio was significantly correlated with pre-Tx serum HCG (P = 0.031). Moreover, MET PET parameters showed significant associations with tumor location, sex, KRAS variant, and symptoms. CONCLUSION: MET PET/CT could be a useful diagnostic tool in patients suspected of having IGs. In addition, the MET avidity of tumor is a potential surrogate biomarker of HCG, which has been used as a diagnostic marker for IGs. Tumor MET parameters also had significant differences according to tumor locations, sex, symptoms, and KRAS mutation. However, MET avidity of tumors had no significant prognostic value.

Tannic acid-functionalized boron nitride nanosheets for theranostics.

Here, we report a tannic acid-Fe3+ coordination complex coating that confers magnetic resonance imaging (MRI) theranostic properties to inert nanomaterials. Boron nitride nanosheets (BNS), which lack magnetic field and light responsiveness, were used as a model nonfunctional nanomaterial. Among various catechol derivatives tested (i.e., dopamine, 3,4-dihydroxyphenylacetic acid, gallic acid, and tannic acid), a coating of tannic acid-Fe3+ coordination complex provided the highest magnetic field relaxivity and near infrared (NIR) laser light responsiveness. An in vitro study showed that KB tumor cells treated with tannic acid-Fe3+ coordination complex adsorbed on BNS (TA-Fe/BNS) exhibited higher T1-weighted magnetic resonance contrast compared with plain BNS, and BNS coated with tannic acid or Fe alone. NIR irradiation at 808 nm caused a significant increase in KB tumor cell death after treatment with TA-Fe/BNS compared with other treatments. In vivo MRI imaging revealed tumor accumulation of intravenously administered TA-Fe/BNS. Guided by MRI information, application of focused laser irradiation onto tumor tissues resulted in complete tumor ablation. These results support the potential of TA-Fe/BNS for MRI theranostics. Moreover, this study suggests the wide applicability of TA-Fe noncovalent coating as biocompatible and facile tool for converting nonfunctional early-generation nanomaterials into functional new nanomaterials, opening new opportunities for their use in translational biomedical applications such as MRI theranostics.

Synthesis and characterization of 64Cu- and Cy5.5-labeled tetraiodothyroacetic acid derivatives for tumor angiogenesis imaging.

It was previously reported that tetraiodothyroacetic acid (tetrac) inhibits angiogenesis by binding to the cell surface receptor for thyroid hormone on integrin αVß3. Therefore, we synthesized and evaluated two 64Cu-labeled tetrac derivatives and a Cy5.5-labeled tetrac derivative for tumor angiogenesis imaging. Tetrac was structurally modified to conjugate with 1,4,7,10-tetraazacyclododecane-N,N',N″,N″'-tetraacetic acid (DOTA) via its hydroxy or carboxylic acid end, and the resulting DOTA-conjugated tetrac derivatives were then labeled with 64Cu. Tetrac was also conjugated with Cy5.5 via its carboxylic acid end. All three tetrac derivatives (1-3) exhibited greater inhibitory activity than tetrac against endothelial cell tube formation. The U87MG cell binding of [64Cu]2 showed a time-dependent increase over 24 h and it was inhibited by 38% at 4 h in the presence of tetrac, indicating specificity of [64Cu]2 to the thyroid hormone receptor site on integrin αVß3. Positron emission tomography (PET) images of U87MG tumor-bearing mice injected with [64Cu]1 and [64Cu]2 revealed that high radioactivity accumulated in the tumors, and that the tumor uptake and tumor-to-nontarget uptake ratio were higher in small tumors than in large tumors. In addition, the Cy5.5-labeled tetrac derivative (3) displayed a strong near-infrared (NIR) signal in the tumors. Taken together, these results suggest that these ligands hold promise as imaging agents for visualization of tumor angiogenesis.

Clinical Significance of Incidental Focal 18F-FDG Uptake in the Spinal Cord of Patients with Cancer.

PURPOSE: We investigated the incidence, location, and clinical significance of focal 18F-FDG uptake of the spinal cord in patients with cancer. METHODS: We reviewed the medical records of 22,937 consecutive adult patients with known or suspicious malignancy who underwent 18F-FDG PET/CT. PET/CT scans with incidental focal spinal cord uptake were selected and retrospectively reviewed to determine the presence, location, number, and maximum standardized uptake value (SUVmax) of any focal hypermetabolic lesions of the spinal cord. In subjects with focal spinal uptake, clinical characteristics and clinical follow-up results, including follow-up PET/CT, were reviewed. RESULTS: Incidental focal spinal cord uptake was observed in 69 of 22,937 adult patients (incidence = 0.3%; M:F = 31:38; age, 55.8 ± 14.7 years). Seventy-eight focal hypermetabolic lesions on spinal cord in the PET/CT scans of the 69 study subjects were analyzed. The most common sites of focal spinal cord uptake were the T12 vertebra (47/78; 60.3%) and L1 vertebra (20/78; 25.6%). Multifocal cord uptake was found in 8 of 69 patients (11.6%). The average SUVmax for cord uptake was 2.5 ± 0.5 (range, 1.4∼3.9). There was no clinical or imaging evidence of abnormalities in the spinal cord, both at the time of PET/CT and during clinical follow-up. CONCLUSIONS: Although incidental focal 18F-FDG uptake of the spinal cord is rare in patients with cancer, it may be physiological or benign, but it should not be considered as malignant involvement. Common sites for the uptake were in the T12 and L1 spine levels.

Value of interim FDG PET/CT for predicting outcome of patients with angioimmunoblastic T-cell lymphoma.

Subjects were 45 patients with angioimmunoblastic T-cell lymphoma (AITL) who underwent 2-[18F]-fluoro-2-deoxy-d-glucose (FDG) positron-emission tomography/computed tomography (PET/CT) at baseline and interim after 2-4 cycles. Predictors of progression-free survival (PFS) and overall survival (OS) were assessed. Positive interim PET/CT (Deauville score ≥3) was a significant independent predictor of poor PFS (Hazard ratio, 4.42; p=.028), and showed marginal significance to predict OS (p=.065). Less than 60% decrease in the average change of maximum standardized uptake value normalized by lean body mass (SULmax) also was a significant independent predictor of poor PFS (Hazard ratio, 12.96; p=.001) and poor OS (Hazard ratio, 24.11; p=.006). Interim PET/CT has a significant prognostic value for predicting PFS and OS in patients with AITL. Deauville score and percent decrease of SULmax have the potential to be useful parameter in classifying patients into good and poor responders.

Intra-patient Variability of FDG Standardized Uptake Values in Mediastinal Blood Pool, Liver, and Myocardium during R-CHOP Chemotherapy in Patients with Diffuse Large B-cell Lymphoma.

PURPOSE: 18F-fluorodeoxyglucose (FDG) PET/CT is useful for staging and evaluating treatment response in patients with diffuse large B-cell lymphoma (DLBCL). A five-point scale model using the mediastinal blood pool (MBP) and liver as references is a recommended method for interpreting treatment response. We evaluated the variability in standardized uptake values (SUVs) of the MBP, liver, and myocardium during chemotherapy in patients with DLBCL. METHODS: We analyzed 60 patients with DLBCL who received rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone (R-CHOP) treatment and underwent baseline, interim, and final FDG PET/CT scans. The FDG uptakes of lymphoma lesions, MBP, liver, and myocardium were assessed, and changes in the MBP and liver SUV and possible associated factors were evaluated. RESULTS: The SUV of the liver did not change significantly during the chemotherapy. However, the SUVmean of MBP showed a significant change though the difference was small (p = 0.019). SUVmean of MBP and liver at baseline and interim scans was significantly lower in patients with advanced Ann Arbor stage on diagnosis. The SUVmean of the MBP and liver was negatively correlated with the volumetric index of lymphoma lesions in baseline scans (r = -0.547, p < 0.001; r = -0.502, p < 0.001). Positive myocardial FDG uptake was more frequently observed in interim and final scans than in the baseline scan, but there was no significant association between the MBP and liver uptake and myocardial uptake. CONCLUSIONS: The SUV of the liver was not significantly changed during R-CHOP chemotherapy in patients with DLBCL, whereas the MBP SUV of the interim scan decreased slightly. However, the SUV of the reference organs may be affected by tumor burden, and this should be considered when assessing follow-up scans. Although myocardial FDG uptake was more frequently observed after R-CHOP chemotherapy, it did not affect the SUV of the MBP and liver.

Synergistic effects of longitudinal amyloid and vascular changes on lobar microbleeds.

OBJECTIVE: To determine whether amyloid and hypertensive cerebral small vessel disease (hCSVD) changes synergistically affect the progression of lobar microbleeds in patients with subcortical vascular mild cognitive impairment (svMCI). METHODS: Among 72 patients with svMCI who underwent brain MRI and [11C] Pittsburgh compound B (PiB)-PET, 52 (72.2%) completed the third year of follow-up. These patients were evaluated by annual neuropsychological testing, brain MRI, and follow-up PiB-PET. RESULTS: Over 3 years, 31 of 52 patients (59.6%) had incident cerebral microbleeds (CMBs) in the lobar and deep regions. Both baseline and longitudinal changes in lacune numbers were associated with increased numbers of lobar and deep microbleeds, while baseline and longitudinal changes in PiB uptake ratio were associated only with the progression of lobar microbleeds, especially in the temporal, parietal, and occipital areas. Regional white matter hyperintensity severity was also associated with regional lobar CMBs in the parietal and occipital regions. There were interactive effects between baseline and longitudinal lacune number and PiB retention on lobar microbleed progression. Increased lobar, but not deep, CMBs were associated with decreased scores in the digit span backward task and Rey-Osterrieth Complex Figure Test. CONCLUSIONS: Our findings suggest that amyloid-related pathology and hCSVD have synergistic effects on the progression of lobar microbleeds, providing new clinical insight into the interaction between amyloid burden and hCSVD on CMB progression and cognitive decline with implications for developing effective prevention strategies.

Mild Alkalization Acutely Triggers the Warburg Effect by Enhancing Hexokinase Activity via Voltage-Dependent Anion Channel Binding.

To fully understand the glycolytic behavior of cancer cells, it is important to recognize how it is linked to pH dynamics. Here, we evaluated the acute effects of mild acidification and alkalization on cancer cell glucose uptake and glycolytic flux and investigated the role of hexokinase (HK). Cancer cells exposed to buffers with graded pH were measured for 18F-fluorodeoxyglucose (FDG) uptake, lactate production and HK activity. Subcellular localization of HK protein was assessed by western blots and confocal microscopy. The interior of T47D breast cancer cells was mildly alkalized to pH 7.5 by a buffer pH of 7.8, and this was accompanied by rapid increases of FDG uptake and lactate extrusion. This shift toward glycolytic flux led to the prompt recovery of a reversed pH gradient. In contrast, mild acidification rapidly reduced cellular FDG uptake and lactate production. Mild acidification decreased and mild alkalization increased mitochondrial HK translocation and enzyme activity. Cells transfected with specific siRNA against HK-1, HK-2 and voltage-dependent anion channel (VDAC)1 displayed significant attenuation of pH-induced changes in FDG uptake. Confocal microscopy showed increased co-localization of HK-1 and HK-2 with VDAC1 by alkaline treatment. In isolated mitochondria, acidic pH increased and alkaline pH decreased release of free HK-1 and HK-2 from the mitochondrial pellet into the supernatant. Furthermore, experiments using purified proteins showed that alkaline pH promoted co-immunoprecipitation of HK with VDAC protein. These findings demonstrate that mild alkalization is sufficient to acutely trigger cancer cell glycolytic flux through enhanced activity of HK by promoting its mitochondrial translocation and VDAC binding. This process might serve as a mechanism through which cancer cells trigger the Warburg effect to maintain a dysregulated pH.

Relation between primary tumor FDG avidity and site of first distant metastasis in patients with breast cancer.

Identification of tumor imaging features associated with metastatic pattern may allow better understanding of cancer dissemination. Here, we investigated how primary tumor F-fluorodeoxyglucose (FDG) avidity influences the first site of breast cancer metastasis.Subjects were 264 patients with advanced breast cancer who underwent positron emission tomography/computed tomography at diagnosis and had metastasis at presentation (n = 193) or metastatic relapse after surgery (n = 71). Primary tumor FDG avidity (maximum SUV [SUVmax] ≥10.1) was compared with histology and first metastatic sites.The most common site of first metastasis was the bone, occurring in 62.7% of patients with metastasis at presentation and 38.0% of those with metastatic relapse. First metastasis to lung occurred in 30.1% and 35.2%, and to liver in 25.4% and 15.2% of respective groups. In patients with metastasis at presentation, primary tumors were FDG avid in 98/193 cases, and this was associated with more frequent first metastasis to lung (37.8% vs 22.1%; P = 0.018). In patients with metastasis relapse, primary tumors were FDG avid in 31/71 cases, and this was associated with more frequent first metastasis to lung (48.4% vs 25.0%; P = 0.041) and liver (29.0% vs 5.0%; P = 0.008). In patients with metastasis relapse, primary tumors that were FDG avid but hormone receptor negative had more first metastasis to lung (57.9% vs 26.9%; P = 0.016).FDG-avid primary breast tumors have favored first spread to the lung and liver, which suggests that tumor cells with heightened glycolytic activity better colonize these organs.

Molecular mechanism of (18)F-FDG uptake reduction induced by genipin in T47D cancer cell and role of uncoupling protein-2 in cancer cell glucose metabolism.

INTRODUCTION: Compounds that modulate cancer cell glucose metabolism could open new opportunities for antitumor therapy and for monitoring response using (18)F-FDG PET. Genipin, a natural dietary compound that blocks uncoupling protein 2 (UCP2)-mediated mitochondrial proton leakage, is a potential anticancer agent. We investigated the effect of genipin on glucose metabolism and the mitochondrial function of cancer cells. METHODS: Breast and colon cancer cells were assessed for effects of genipin on (18)F-FDG uptake. T47D breast cancer cells were further evaluated for time-dependent and dose-dependent effects on (18)F-FDG uptake, lactate release, oxygen consumption rate (OCR), reactive oxygen species (ROS) production, and mitochondrial membrane potential. The effects of UCP2 knockdown were evaluated using specific siRNA. RESULTS: Cancer cells displayed significant reductions in (18)F-FDG uptake by genipin. T47D cells showed the greatest reduction to 32.6±1.0% of controls by 250µM genipin. The effect occurred rapidly, reaching a plateau by 1h that lasted up to 24h. The effect was dose-dependent with a half-inhibitory concentration of 60.8µM. An accompanying decrease in lactate release was consistent with reduced glycolytic flux. OCR was significantly decreased by genipin to 82.2±11.4% of controls, and ROS generation was increased to 156.7±16.0%. These effects were largely reproduced by UCP2 knockdown with specific siRNA. CONCLUSIONS: Genipin decreased cancer cell (18)F-FDG uptake by reducing both glycolytic flux and mitochondrial oxidative respiration. This effect appeared to occur by blocking the ability of UCP2 to dissipate energy and restrict ROS production through proton leakage.

Catabolism of (64)Cu and Cy5.5-labeled human serum albumin in a tumor xenograft model.

Human serum albumin (HSA), the most abundant protein in blood plasma, has been used as a drug carrier for the last few decades. Residualizingly radiolabeled serum albumin has been reported to be avidly taken up by tumors of sarcoma-bearing mice and to most likely undergo lysosomal degradation. In this study, we prepared (64)Cu-1,4,7,10-tetraazacyclododecane-N,N',N″,N'″-tetraacetic acid (DOTA) and Cy5.5-conjugated HSA (dual probe), and evaluated its tumor uptake and catabolism. Two dual probes were prepared using different DOTA conjugation sites of HSA (one via Lys residues and the other via the Cys residue). (64)Cu-DOTA-Lys-HSA-Cy5.5 (dual probe-Lys) exhibited higher uptake by RR1022 sarcoma cells in vitro than (64)Cu-DOTA-Cys-HSA-Cy5.5 (dual probe-Cys). In RR1022 tumor-bearing mice, the two dual probes showed a similar level of tumor uptake, but uptake of dual probe-Lys was reduced in the liver and spleen compared to dual probe-Cys, probably because of the presence of a higher number of DOTA molecules in the former. At 24 and 48 h after injection, dual probe-Lys was intact or partially degraded in blood, liver, kidney, and tumor samples, but (64)Cu-DOTA-Lys was observed in the urine using radioactivity detection. Similarly, Cy5.5-Lys was observed in the urine using fluorescence detection. These results indicate that dual probe-Lys may be useful for predicting the catabolic fate of drug-HSA conjugates.

Utility of FDG PET/CT for Differential Diagnosis of Patients Clinically Suspected of IgG4-Related Disease.

PURPOSE: We investigated the capacity of F-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography/computed tomography (PET/CT) to differentially diagnose immunoglobulin G4-related disease (IgG4-RD) in clinically suspected patients. MATERIALS AND METHODS: Subjects were 94 clinically suspected patients who had tissue IgG4 staining (n = 85) or serum IgG4 greater than 135 mg/dL (n = 9) and underwent FDG PET/CT within 40 days. Clinical, serologic, pathological, and PET/CT findings were analyzed. Binary logistic regression analysis was performed to assess the diagnostic performance of PET/CT. RESULTS: Final diagnosis was IgG4-RD in 28, malignancy in 29, IgG4-unrelated inflammation in 35, and undetermined cause in 2 subjects. Patients with IgG4-RD had lower maximum standardized uptake value (SUVmax) of FDG uptake in lesions (4.6 ± 1.7 vs 7.1 ± 5.0) and higher submandibular gland SUVmax (2.8 ± 1.0 vs 2.3 ± 0.6) and were more likely to have diffuse/heterogeneous uptake pattern (78.6% vs 54.8%). The relation between SUVmax of lesions and histopathological findings was weak. On binary logistic regression analysis, lesion SUVmax, submandibular gland SUVmax, and multiorgan involvement were significant predictors of IgG4-RD and provided an area under the receiver operating characteristics curve of 0.824. With optimum criteria, FDG PET/CT had a sensitivity of 85.7% and specificity of 66.1% for diagnosing IgG4-RD. CONCLUSIONS: FDG PET/CT findings may have the capacity to potentially differentiate IgG4 RD from other diseases in clinically suspected patients.

Effects of curcumin on cancer cell mitochondrial function and potential monitoring with ¹8F-FDG uptake.

A better understanding of how curcumin influences cancer cell biology could help devise new strategies to enhance its antitumor effect. Many curcumin actions are proposed to occur by targeting mitochondrial function, among which glucose metabolism and reactive oxygen species (ROS) production are pivotal. However, little is known of how curcumin influences cancer cell glucose metabolism. We thus evaluated the effect of curcumin on cancer cell glucose metabolism and mitochondrial function, and further investigated whether these responses could be modified to enhance the anticancer potency of the compound. MCF-7 breast cancer cells treated with curcumin were measured for 18F-fluorodeoxyglucose (18F­FDG) uptake, lactate production, hexokinase activity, oxygen consumption rate (OCR), ROS production and mitochondrial membrane potential (MMP). Activation of signaling pathways was evaluated by western blots, and cell survival was assessed with sulforhodamine B assays. Curcumin stimulated a 3.6-fold increase of 18F-FDG uptake in MCF-7 cells, along with augmented hexokinase activity and lactate efflux. This was accompanied by significantly suppressed cellular OCR, consistent with a metabolic shift to glycolytic flux. Inhibiting this metabolic response with 2-deoxyglucose (2-DG) blocked curcumin-induced mTOR activation and resulted in a greater anti-proliferative effect. Curcumin-induced MMP depolarization led to reduced ROS production, which may hinder the anticancer effect of the compound. Intracellular ROS was completely restored by adding Cu2+, which can bind and modify the curcumin's physico-chemical property, and this resulted in a marked potentiation of its anti-proliferative effect. Thus, curcumin suppresses cancer cell MMP and ROS generation, and this response is accompanied by stimulated 18F-FDG uptake via shifting of metabolism from mitochondrial respiration to glycolytic flux. These mitochondrial and metabolic responses may provide potential targets that can help enhance the anticancer action of curcumin.

Clinical Significance of Incidental 18F-FDG Uptake in the Pyriform Sinus Detected by PET/CT.

PURPOSE: We investigated the significance of unexpected focal pyriform sinus FDG uptake and determined the ability of PET/CT parameters to identify malignancy. MATERIALS AND METHODS: FDG PET/CT reports of 56,585 consecutive subjects were retrospectively reviewed, and 281 cases (0.50%) with focal pyriform sinus uptake were included. PET images were assessed for maximum standardized uptake values (SUVmax) and asymmetric indices of FDG activity, and CT images were evaluated for pyriform sinus narrowing. The final diagnosis was determined by tissue biopsy, laryngoscopy, radiological findings, and clinical follow-up. RESULTS: Among the 281 subjects, final diagnosis was pyriform sinus malignancy in 29 (10.3%) and benignity in 215 cases (76.5%). Malignant lesions had significantly higher SUVmax (9.13 ± 3.64 vs. 3.53 ± 1.01) and asymmetric index (4.16 ± 1.81 vs. 1.54 ± 0.39) compared to benign causes. Patients with malignant lesions also had higher cervical lymph node SUVmax (6.66 ± 8.79 vs. 2.76 ± 2.46, all P < 0.001). Lesion SUVmax ≥4.24 identified malignancy with a sensitivity of 93.1% and specificity of 86.5%. Asymmetric index ≥1.81 had a sensitivity of 100% and specificity of 89.7%. CONCLUSION: Incidentally identified focal pyriform sinus uptake on FDG PET/CT should be evaluated for possible malignancy in the presence of high SUVmax or asymmetric index.

Primary Tumor ¹8F-FDG Avidity Affects the Performance of ¹8F-FDG PET/CT for Detecting Gastric Cancer Recurrence.

UNLABELLED: The usefulness of (18)F-FDG PET in gastric cancer recurrence is limited by low sensitivity. Given that detectability by PET is dependent on the tumor's metabolic characteristics, we tested whether the performance of PET for gastric cancer recurrence is enhanced in patients with (18)F-FDG-avid primary tumors. METHODS: Three hundred sixty-eight patients with advanced gastric cancer underwent (18)F-FDG PET/CT for initial staging and for recurrence surveillance after curative surgery. On initial PET/CT, primary tumors were (18)F-FDG-avid if they displayed focal uptake with an SUVmax 4 or more. Follow-up (18)F-FDG PET/CT was evaluated for recurrent disease. RESULTS: On initial PET/CT, the primary tumor was (18)F-FDG-avid in 236 of 368 (64.1%) and nonavid in 132 patients (35.9%). During follow-up for 18.9 ± 13.3 mo, 72 patients (19.6%) had recurrence. Of the 63 PET scans with recurrence, 42 (66.7%) and 21 (33.3%) were scans of patients with (18)F-FDG-avid and nonavid primary tumors, respectively. PET sensitivity was higher in scans of patients with (18)F-FDG-avid than nonavid tumors for all recurrences (81.0% vs. 52.4%;P= 0.018) and nonanastomosis site recurrences (82.1% vs. 47.4%; P= 0.006). The sensitivity for detecting peritoneal recurrence was also higher for the avid tumor group. PET specificity was similarly high (97.1% and 97.5%) for both groups. Adding cell type and Lauren classification to tumor(18)F-FDG avidity further enhanced PET sensitivity. CONCLUSION: Surveillance (18)F-FDG PET/CT after resection of gastric cancer has significantly higher sensitivity in patients with (18)F-FDG-avid primary tumors and may have greater value in this group.

Hybrid PET/optical imaging of integrin αVß3 receptor expression using a (64)Cu-labeled streptavidin/biotin-based dimeric RGD peptide.

BACKGROUND: Hybrid PET/optical imaging provides quantitative and complementary information for diagnosis of tumors. Herein, we developed a (64)Cu-labeled AlexaFluor 680-streptavidin ((AF)SAv)/biotin-based dimeric cyclic RGD peptide (RGD2) for hybrid PET/optical imaging of integrin αVß3 expression. METHODS: (64)Cu-1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA)-(AF)SAv/biotin-PEG-RGD2 was prepared by formation of a complex comprising DOTA-(AF)SAv and biotin-PEG-RGD2, followed by radiolabeling with (64)Cu. Receptor binding studies of DOTA-(AF)SAv/biotin-PEG-RGD2 were performed using U87MG cells and (125)I-RGDyK as the radioligand, and cellular uptake studies of (64)Cu-DOTA-(AF)SAv/biotin-PEG-RGD2 were also performed. MicroPET imaging followed by optical imaging of U87MG tumor-bearing mice was acquired after injection of the hybrid probe, and region of interest (ROI) analysis of tumors was performed. Ex vivo PET/optical imaging and biodistribution studies of the major tissues were performed after the in vivo imaging, and immunofluorescence staining of the tumor tissue sections was carried out. RESULTS: (64)Cu-DOTA-(AF)SAv/biotin-PEG-RGD2 was prepared in 52.1 ± 5.4 % radiochemical yield and with specific activity of 1.0 ± 0.1 GBq/mg. Receptor binding studies showed that DOTA-(AF)SAv/biotin-PEG-RGD2 had higher binding affinity for integrin αVß3 than RGD2, reflecting a possible polyvalency effect. Moreover, the hybrid probe revealed time-dependent uptake by U87MG cells. In a microPET/optical imaging study, the hybrid probe demonstrated high accumulation in tumors; ROI analysis revealed 2.7 ± 0.2 % ID/g at 1 h and 4.7 ± 0.2 % ID/g at 21 h after injection, and subsequently acquired optical images showed tumors with strong fluorescence intensity. Ex vivo PET/optical images of the major tissues confirmed the in vivo imaging data, and biodistribution studies demonstrated high and specific uptake in tumors (4.8 ± 0.1 % ID/g). Immunofluorescence staining showed the formation of new blood vessels in tumor tissues, suggesting that the tumor uptake was due to specific binding of the hybrid probe to integrin αVß3 expressed on tumor cells. CONCLUSIONS: These results indicate that a (64)Cu-DOTA-(AF)SAv/biotin-PEG-RGD2 is able to provide quantitative information on hybrid PET/optical imaging of integrin αVß3 expression.