Metabolic Tumor Volume Measured by 18F-FDG PET/CT is Associated with the Survival of Unresectable Hepatocellular Carcinoma Treated with PD-1/PD-L1 Inhibitors Plus Molecular Targeted Agents.

Purpose: The combination of PD-1/PD-L1 inhibitors and molecular targeted agents showed promising efficacy for unresectable hepatocellular carcinoma (uHCC). This study aimed to investigate the prognostic value of metabolic parameters from 18F-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET/CT) in patients with uHCC underwent the combined therapies. Patients and Methods: Patients with uHCC treated with a combination of immunotherapy and targeted therapy who underwent baseline 18F-FDG PET/CT between July 2018 and December 2021 were recruited retrospectively. The metabolic tumor volume (MTV), total lesion glycolysis (TLG), maximum standardized uptake values (SUVmax), and clinical and biological parameters were recorded. A multivariate prediction model was developed for overall survival (OS) using these parameters together with clinical prognostic factors. Results: Seventy-seven patients were finally included. The median OS was 16.8 months. We found that a high MTV (≥39.65 cm3 as the median value) was significantly associated with OS (P<0.05). In multivariate analyses for OS, a high MTV, high Eastern Cooperative Oncology Group performance status (ECOG-PS, ≥1), Child-Pugh (B-C) grade, and the presence of bone metastasis were significantly associated with poor OS (HR 1.371, HR 3.73, HR 15.384, and HR 2.994, all P<0.05, respectively). A multivariate prognostic model including MTV and prognostic factors, such as ECOG-PS, Child-Pugh grade, and bone metastasis, further improved the identification of different OS subgroups. Conclusion: High MTV is an adverse prognostic factor in patients with uHCC treated with a combination of immunotherapy and molecular targeted agents. Integrating PET/CT parameters with clinical prognostic factors could help to personalize immunotherapy.

Dynamic PET/CT scan of 68Ga-FAPI-04 for the optimal acquisition time in suspected malignant hepatic cancer patients.

PURPOSE: Dynamic PET/CT scan of 68Ga-FAPI-04 in patients with suspected malignant hepatic lesions were retrospectively analyzed to find the optimal acquisition time with better lesion detection rate. METHODS: Twenty-two patients with lesions confirmed by CT or MRI were performed with dynamic 68Ga-FAPI-04 PET/CT scan. Tracer uptake of lesions and normal organs at different time points were analyzed. Standardized uptake value (SUV) and tumor-to-background (TBR) were calculated based on the quantification of images. RESULTS: SUV of normal organs decreased rapidly from 10 to 30 min and decreased gradually from 30 to 60 min. Besides, the uterus showed a particularly high uptake in all patients (12.62 ± 4.58 at 10 min p.i., 12.04 ± 3.99 at 30 min p.i., 10.92 ± 2.38 at 60 min p.i.). SUV of lesions decreased gradually, while TBR increased from 10- to 60-min post-injection. Visual analysis verified a comparable lesion detectability of 30 min and 60 min with images of 10 min showing a decreased lesion detection number. CONCLUSION: This study revealed that similar detection rates were achieved at both 30 and 60 min, suggesting a static scan at 30 min to be appropriate in the clinic. Besides, although with high lesion uptake, early 68Ga-FAPI-04 PET imaging at 10 min after tracer injection could cause missed lesion detection.

Characterization of myocardial oxidative metabolism and myocardial external efficiency in high-risk alcohol cardiotoxicity and alcoholic cardiomyopathy via dynamic 11C-Acetate positron emission tomography.

INTRODUCTION: The purpose of this study was to evaluate subjects with high-risk alcohol cardiotoxicity and patients with alcoholic cardiomyopathy (ACM) via dynamic 11C-Acetate positron emission tomography (PET) imaging as a myocardial oxidative metabolic probe. METHODS AND RESULTS: We recruited 37 subjects with chronic alcohol consumption [18 with moderate consumption (MC), 19 with heavy consumption (HC)], 5 ACM patients, and 12 healthy controls to receive dynamic 11C-Acetate PET scans. PET imaging data were analyzed to calculate kinetic parameters (e.g., Kmono, K1 and k2) based on the mono-exponential and one-tissue compartmental models. Myocardial oxygen consumption (MVO2) and myocardial external efficiency (MEE) were then derived from these kinetic parameters. MVO2 was significantly lowered in the HC group and in ACM patients (0.121± 0.018 and 0.111 ± 0.017 mL·g-1·min-1, respectively) compared with those in healthy controls and MC subjects (0.144 ± 0.023 and 0.146 ± 0.027 mL·g-1·min-1, respectively; P < .01). MEE was significantly reduced in ACM patients (13.0% ± 4.3%) compared with those of healthy controls (22.4% ± 4.6%, P < .01), MC subjects (20.1% ± 4.5%, P < .05), and HC subjects (22.3% ± 4.5%, P < .001). CONCLUSION: Functional assessment via dynamic 11C-Acetate PET imaging may represent a clinically feasible probe for identifying cohorts with high-risk cardiotoxicity due to addictive alcohol consumption and ACM.

Integrin αvß6-targeted MR molecular imaging of breast cancer in a xenograft mouse model.

BACKGROUND: The motif RXDLXXL-based nanoprobes allow specific imaging of integrin αvß6, a protein overexpressed during tumorigenesis and tumor progression of various tumors. We applied a novel RXDLXXL-coupled cyclic arginine-glycine-aspartate (RGD) nonapeptide conjugated with ultrasmall superparamagnetic iron oxide nanoparticles (referred to as cFK-9-USPIO) for the application of integrin αvß6-targeted magnetic resonance (MR) molecular imaging for breast cancer. METHODS: A novel MR-targeted nanoprobe, cFK-9-USPIO, was synthesized by conjugating integrin αvß6-targeted peptide cFK-9 to N-amino (-NH2)-modified USPIO nanoparticles via a dehydration esterification reaction. Integrin αvß6-positive mouse breast cancer (4 T1) and integrin αvß6 negative human embryonic kidney 293 (HEK293) cell lines were incubated with cFK-9-AbFlour 647 (blocking group) or cFK-9-USPIO (experimental group), and subsequently imaged using laser scanning confocal microscopy (LSCM) and 3.0 Tesla magnetic resonance imaging (MRI) system. The affinity of cFK-9 targeting αvß6 was analyzed by calculating the mean fluorescent intensity in cells, and the nanoparticle targeting effect was measured by the reduction of T2 values in an in vitro MRI. The in vivo MRI capability of cFK-9-USPIO was investigated in 4 T1 xenograft mouse models. Binding of the targeted nanoparticles to αvß6-positive 4 T1 tumors was determined by ex vivo histopathology. RESULTS: In vitro laser scanning confocal microscopy (LSCM) imaging showed that the difference in fluorescence intensity between the targeting and blocking groups of 4 T1 cells was significantly greater than that in HEK293 cells (P < 0.05). The in vitro MRI demonstrated a more remarkable T2 reduction in 4 T1 cells than in HEK293 cells (P < 0.001). The in vivo MRI of 4 T1 xenograft tumor-bearing nude mice showed significant T2 reduction in tumors compared to controls. Prussian blue staining further confirmed that αvß6 integrin-targeted nanoparticles were specifically accumulated in 4 T1 tumors and notably fewer nanoparticles were detected in 4 T1 tumors of mice injected with control USPIO and HEK293 tumors of mice administered cFK-9-USPIO. CONCLUSIONS: Integrin αvß6-targeted nanoparticles have great potential for use in the detection of αvß6-overexpressed breast cancer with MR molecular imaging.

The Relationship Among Glucose Metabolism, Cerebral Blood Flow, and Functional Activity: a Hybrid PET/fMRI Study.

18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) estimate brain activities from different aspects, including regional glucose uptake (rGU) by 18FDG-PET, regional cerebral blood flow (rCBF) by arterial spin labeling, and dynamic changes of deoxyhemoglobin by blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI). However, the relationships between them remain incompletely understood. In the current study, twenty-four subjects (14 males, 10 females) were recruited and investigated the correlation among rGU, rCBF, and BOLD fMRI-derived metrics reflecting the neural activity, including amplitude of low-frequency fluctuation (ALFF), regional homogeneity (ReHo), and degree centrality (DC) by hybrid PET/fMRI. Correlation analyses were performed across subject and across space at both voxel level and region level, considering partial volume effects by adjusting for gray matter volume. Each pair of metrics showed significant across-space correlations. rGU against ReHo showed the highest mean correlation coefficients. rGU had higher correlations with three resting-state (RS) fMRI metrics than did ASL-rCBF. However, the across-subject correlations were not significant among functional modalities (rGU, rCBF, and RS-fMRI BOLD data) at either voxel level or region level even with a liberal threshold, except for significant across-subject correlation between RS-fMRI metrics (ALFF, ReHo, and DC). These comprehensive findings from hybrid PET/MR might provide complementary information to reveal the underlying mechanisms of the brain activity and open new perspective to interpret pathologic conditions.

Scintigraphic Imaging of Neovascularization With 99mTc-3PRGD2 for Evaluating Early Response to Endostar Involved Therapies on Pancreatic Cancer Xenografts In Vivo.

Background: Molecular imaging targeting angiogenesis can specifically monitor the early therapeutic effect of antiangiogenesis therapy. We explore the predictive values of an integrin αvß3-targeted tracer, 99mTc-PEG4-E[PEG4-c(RGDfK)]2 (99mTc-3PRGD2), for monitoring the efficacy of Endostar antiangiogenic therapy and chemotherapy in animal models. Methods: The pancreatic cancer xenograft mice were randomly divided into four groups, with seven animals in each group and treated in different groups with 10 mg/kg/day of Endostar, 10 mg/kg/day of gemcitabine, 10 mg/kg/day of Endostar +10 mg/kg/day of gemcitabine at the same time, and the control group with 0.9% saline (0.1 ml/day). 99mTc-3PRGD2 scintigraphic imaging was carried out to monitor therapeutic effects. Microvessel density (MVD) was measured using immunohistochemical staining of the tumor tissues. The region of interest (ROI) of tumor (T) and contralateral corresponding site (NT) was delineated, and the ratio of radioactivity (T/NT) was calculated. Two-way repeated-measure analysis of variance (ANOVA) was used to assess differences between treatment groups. Results: Tumor growth was significantly lower in treatment groups than that in the control group (p < 0.05), and the differences were noted on day 28 posttreatment. The differences of 99mTc-3PRGD2 uptakes were observed between the control group and Endostar group (p = 0.033) and the combined treatment group (p < 0.01) on day 7 posttreatment and on day 14 posttreatment between the control group and gemcitabine group (p < 0.01). The accumulation of 99mTc-3PRGD2 was significantly correlated with MVD (r = 0.998, p = 0.002). Conclusion: With 99mTc-3PRGD2 scintigraphic imaging, the tumor response to antiangiogenic therapy, chemotherapy, and the combined treatment can be observed at an early stage of the treatments, much earlier than the tumor volume change. It provides new opportunities for developing individualized therapies and dose optimization.

Static 18F-FET PET and DSC-PWI based on hybrid PET/MR for the prediction of gliomas defined by IDH and 1p/19q status.

OBJECTIVES: To investigate the predictive value of static O-(2-18F-fluoroethyl)-L-tyrosine positron emission tomography (18F-FET PET) and cerebral blood volume (CBV) for glioma grading and determining isocitrate dehydrogenase (IDH) mutation and 1p/19q codeletion status. METHODS: Fifty-two patients with newly diagnosed gliomas who underwent simultaneous 18F-FET PET and dynamic susceptibility contrast perfusion-weighted imaging (DSC-PWI) examinations on hybrid PET/MR were retrospectively enrolled. The mean and max tumor-to-brain ratio (TBR) and normalized CBV (nCBV) were calculated based on whole tumor volume segmentations with reference to PET/MR images. The predictive efficacy of FET PET and CBV in glioma according to the 2016 World Health Organization (WHO) classification was evaluated by receiver operating characteristic curve analyses with the area under the curve (AUC). RESULTS: TBRmean, TBRmax, nCBVmean, and nCBVmax differed between low- and high-grade gliomas, with the highest AUC of nCBVmean (0.920). TBRmax and nCBVmean showed significant differences between gliomas with and without IDH mutation (p = 0.032 and 0.010, respectively). Furthermore, TBRmean, TBRmax, and nCBVmean discriminated between IDH-wildtype glioblastomas and IDH-mutated astrocytomas (p = 0.049, 0.034 and 0.029, respectively). The combination of TBRmax and nCBVmean showed the best predictive performance (AUC, 0.903). Only nCBVmean differentiated IDH-mutated with 1p/19q codeletion oligodendrogliomas from IDH-wildtype glioblastomas (p < 0.001) (AUC, 0.829), but none of the parameters discriminated between oligodendrogliomas and astrocytomas. CONCLUSIONS: Both FET PET and DSC-PWI might be non-invasive predictors for glioma grades and IDH mutation status. FET PET combined with CBV could improve the differentiation of IDH-mutated astrocytomas and IDH-wildtype glioblastomas. However, FET PET and CBV might be limited for identifying oligodendrogliomas. KEY POINTS: • Static 18F-FET PET and DSC-PWI parameters differed between low- and high-grade gliomas, with the highest AUC of the mean value of normalized CBV. • Static 18F-FET PET and DSC-PWI parameters based on hybrid PET/MR showed predictive value in identifying glioma IDH mutation subtypes, which have gained importance for both determining the diagnosis and prognosis of gliomas according to the 2016 WHO classification. • Static 18F-FET PET and DSC-PWI parameters have limited potential in differentiating IDH-mutated with 1p/19q codeletion oligodendrogliomas from IDH-wildtype glioblastomas or IDH-mutated astrocytomas.

Imaging and monitoring HER2 expression in breast cancer during trastuzumab therapy with a peptide probe 99mTc-HYNIC-H10F.

PURPOSE: The novel molecular imaging probe 99mTc-HYNIC-H10F was developed for patient screening and efficacy monitoring of trastuzumab therapy by SPECT imaging of HER2 expression in breast cancer. METHODS: 99mTc-HYNIC-H10F was developed by labeling H10F peptide with 99mTc following an optimized protocol. Biodistribution and SPECT/CT were performed in mouse models bearing HER2-positive SK-BR3 and HER2-negative MDA-MB-231 human breast cancer xenografts, respectively. The treatment response to trastuzumab was monitored and quantified by SPECT/CT in two HER2-positive breast cancer models (SK-BR3 and MDA-MB-361). The preliminary clinical study was performed in two patients with breast cancer. RESULTS: SPECT/CT with 99mTc-HYNIC-H10F showed that the SK-BR3 tumors were clearly visualized, while the signals from MDA-MB-231 tumors were much lower. The tumor uptake of 99mTc-HYNIC-H10F could be blocked by excess unlabeled H10F peptide but not by excess trastuzumab. The growth of two HER2-positive tumors was prominently suppressed at day 11 post-treatment. However, SPECT/CT reflected much earlier therapy response at day 4 post-treatment. The HER2 expression in tumors of breast cancer patients could be detected by 99mTc-HYNIC-H10F SPECT/CT imaging. CONCLUSIONS: 99mTc-HYNIC-H10F specifically accumulates in HER2-positive tumors. Compared with trastuzumab, 99mTc-HYNIC-H10F binds to a different domain of HER2 antigen, providing new opportunities to monitor HER2 expression levels before/during/after trastuzumab treatment for more effective personalized treatment.

Value of integrated PET-IVIM MR in assessing metastases in hypermetabolic pelvic lymph nodes in cervical cancer: a multi-parameter study.

PURPOSE: To evaluate the value of integrated multi-parameter positron emission tomography-intravoxel incoherent motion magnetic resonance (PET-IVIM MR) imaging for pelvic lymph nodes with high FDG uptake in cervical cancer, and to determine the best combination of parameters. METHODS: A total of 38 patients with 59 lymph nodes with high FDG uptake were included. The imaging parameters of the lymph nodes were calculated by PET-IVIM MR, and the differences between lymph nodes diagnosed by postoperative pathology as metastasis versus non-metastasis were compared. We used the receiver operating characteristic (ROC) curve and logistic regression to construct a combination prediction model to filter low value and similar parameters, in order to search the optimal combination of PET/MR parameters for predicting pathologically confirmed metastatic lymph nodes. The correlation between diffusion parameters and metabolic parameters was analyzed by Spearman's rank correlation. RESULTS: The maximum standardized uptake value (SUVmax), mean standardized uptake value (SUVmean), total metabolic tumor volume (MTV), total lesion glycolysis (TLG), apparent diffusion coefficient (ADC), diffusion-related coefficient (D), and perfusion-related parameter (F) showed significant differences between the metastatic and non-metastatic groups (p < 0.05). The combination of MTV, SUVmax, and D had the strongest predictive value (area under the ROC 0.983, p < 0.05). SUVmax, SUVmean, and TLG weakly correlated with F (R = - 0.306, - 0.290, and - 0.310; p < 0.05). CONCLUSIONS: The combination of MTV, SUVmax, and D may have a better diagnostic performance than PET- or IVIM-derived parameters either in combination or individually. No strong correlation exists between diffusion parameters and metabolic parameters. KEY POINTS: • Integrated PET-IVIM MR may assist to characterize lymph node status. • The combination of MTV, SUVmax, and D may have a better diagnostic performance than PET- or IVIM-derived parameters either in combination or individually for the assessment of pelvic lymph nodes with high FDG uptake. • No strong correlation exists between diffusion parameters and metabolic parameters in pelvic lymph nodes with high FDG uptake.

Simultaneous FET-PET and contrast-enhanced MRI based on hybrid PET/MR improves delineation of tumor spatial biodistribution in gliomas: a biopsy validation study.

PURPOSE: Glioma treatment planning requires precise tumor delineation, which is typically performed with contrast-enhanced (CE) MRI. However, CE MRI fails to reflect the entire extent of glioma. O-(2-18F-fluoroethyl)-L-tyrosine (18F-FET) PET may detect tumor volumes missed by CE MRI. We investigated the clinical value of simultaneous FET-PET and CE MRI in delineating tumor extent before treatment planning. Guided stereotactic biopsy was used to validate the findings. METHODS: Conventional MRI and 18F-FET PET were performed simultaneously on a hybrid PET/MR in 33 patients with histopathologically confirmed glioma. Tumor volumes were quantified using a tumor-to-brain ratio ≥ 1.6 (VPET) and a visual threshold (VCE). We visually assessed abnormal areas on FLAIR images and calculated Dice's coefficient (DSC), overlap volume (OV), discrepancy-PET, and discrepancy-CE. Additionally, several stereotactic biopsy samples were taken from "matched" or "mismatched" FET-PET and CE MRI regions. RESULTS: Among 31 patients (93.94%), FET-PET delineated significantly larger tumor volumes than CE MRI (77.84 ± 51.74 cm3 vs. 34.59 ± 27.07 cm3, P < 0.05). Of the 21 biopsy samples obtained from regions with increased FET uptake, all were histopathologically confirmed as glioma tissue or tumor infiltration, whereas only 13 showed enhancement on CE MRI. Among all patients, the spatial similarity between VPET and VCE was low (average DSC 0.56 ± 0.22), while the overlap was high (average OV 0.95 ± 0.08). The discrepancy-CE and discrepancy-PET were lower than 10% in 28 and 0 patients, respectively. Eleven patients showed VPET partially beyond abnormal signal areas on FLAIR images. CONCLUSION: The metabolically active biodistribution of gliomas delineated with FET-PET significantly exceeds tumor volume on CE MRI, and histopathology confirms these findings. Our preliminary results indicate that combining the anatomic and molecular information obtained from conventional MRI and FET-PET would reveal a more accurate glioma extent, which is critical for individualized treatment planning.

In vivo preclinical PET/CT imaging of carbon-11-labeled aminoglycerol probe for the diagnosis of liver fibrosis.

OBJECTIVE: As an important membrane protein, aquaglyceroporin involves liver glycerol metabolism, which can be used to stage liver fibrosis. In this study, we synthesized a novel molecular probe carbon-11-labeled AR ([11C]AR) with aminoglycerol (AR), and evaluated its preclinical performance for liver fibrosis diagnosis by positron emission tomography/computed tomography (PET/CT) imaging in vivo. METHODS: We developed a fully automatic synthesis procedure for the preparation of [11C]AR by radiolabeling glycerol analogue precursor AR with carbon-11. The liver uptake kinetics of [11C]AR was investigated using a rat model by the PET/CT scanner. The dynamic PET/CT scans were performed between the control group (n = 5) and experimental group (n = 25), which was divided into three subgroups (S1, S2 + S3, S4) based on the stages of liver fibrosis. The regions of interest (ROIs) of 20 pixels were drawn in the liver area on the reconstructed images. One-way analysis of variance and independent sample t test were used to analyze the statistical difference of the maximum standardized uptake value (SUVmax) among the groups at series of scanning time points (20 s, 60 s, 90 s, 150 s, 5 min, 10 min, 20 min and 25 min). RESULTS: The fully automatic synthesis of [11C]AR was successfully achieved with high synthesis efficiency (above 50%). The uptake of [11C]AR in progressive liver fibrosis tissues was significantly lower than that in healthy livers at all the imaging time points (P < 0.05), especially at early time points (before 10 min p.i.). A cut-off SUVmax value (1.1) at 150 s p.i. was set for discrimination progressive fibrosis from healthy liver. More experimental and healthy rats were tested with this new threshold to evaluate fibrosis situation. The sensitivity of detecting progressive fibrosis with [11C]AR was 100% in the second cohort. CONCLUSION: We demonstrated a new carbon-11-radiolabeled aminoglycerol PET/CT imaging probe [11C]AR for liver fibrosis diagnosis and staging, which may allow potential assessment of liver fibrosis stages in a rapid and noninvasive method.

SPECT/CT Imaging of the Novel HER2-Targeted Peptide Probe 99mTc-HYNIC-H6F in Breast Cancer Mouse Models.

Overexpression of human epidermal growth factor receptor 2 (HER2) plays important roles in tumorigenesis and tumor progression in breast cancer. Nuclear imaging of HER2 expression in tumors might detect all HER2-positive tumors throughout the body and guide HER2-targeted therapies for patients. We therefore aimed to develop a HER2-targeted peptide probe for breast cancer imaging. A novel SPECT imaging probe, 99mTc-HYNIC-H6F, was prepared and then evaluated in breast cancer animal models. Methods: The HER2-targeted peptide H6F (YLFFVFER) was conjugated with the bifunctional chelator hydrazinonicotinamide (HYNIC). 99mTc-HYNIC-H6F was prepared, and the in vivo characteristics of 99mTc-HYNIC-H6F were investigated in MDA-MB-453 (HER2-positive) and MDA-MB-231 (HER2-negative) models using small-animal SPECT/CT. Moreover, to investigate the specificity of the H6F peptide toward HER2 and the potential applications in monitoring therapies involving trastuzumab, unlabeled H6F and trastuzumab were used as blocking agents in cell competition studies and SPECT imaging. Results: A standard tricine/trisodium triphenylphosphine-3,3',3″-trisulfonate labeling procedure demonstrated that the radiochemical purity was greater than 95%. 99mTc-HYNIC-H6F displayed excellent HER2-binding specificity both in vitro and in vivo. SPECT/CT imaging revealed that the MDA-MB-453 tumors were clearly visualized (percentage injected dose per gram, 3.58 ± 0.01 at 30 min after injection), whereas the signals in HER2-negative MDA-MB-231 tumors were much lower (0.73 ± 0.22 at 30 min after injection). Tumor uptake of MDA-MB-453 was blocked by the coinjection of excess H6F but not by excess trastuzumab. Conclusion: The 99mTc-HYNIC-H6F peptide probe specifically accumulates in HER2-positive tumors and is therefore promising for the diagnosis of HER2-positive cancers. Because 99mTc-HYNIC-H6F and trastuzumab target different regions of the HER2 receptor, this radiotracer also has great potential for monitoring the therapeutic efficacy of trastuzumab by rechecking the expression level of HER2 without blocking effect during therapy.

Scavenger Receptor Class B Type 1 Deletion Led to Coronary Atherosclerosis and Ischemic Heart Disease in Low-density Lipoprotein Receptor Knockout Mice on Modified Western-type Diet.

AIM: Atherosclerosis-prone apolipoprotein E (apoE) or low-density lipoprotein receptor (LDL-R) knockout (KO) mice are generally resistant to developing coronary atherosclerosis (CA) and ischemic heart disease (IHD). However, studies have demonstrated the occurrence of spontaneous CA and IHD in scavenger receptor class B type 1 (SR-BI)/apoE double KO (dKO) mice, which suggests that SR-BI could be a potential target for the prevention and therapy of CA and IHD. This possibility was later investigated in SR-BI/LDL-R dKO mice, but no signs of CA or IHD was identified when mice were fed a normal western-type diet. Here we explored whether SR-BI deletion could result in CA and IHD in LDL-R KO mice when fed a modified western-type diet containing higher (0.5%) cholesterol. METHODS: Cardiac functions were detected by electrocardiography, single photon emission computed tomography (SPECT), echocardiography (Echo) and 2,3,5-triphenyltetrazolium chloride staining. CA was visualized by hematoxylin-eosin staining. RESULTS: After 12 weeks on the modified diet, SR-BI/LDL-R dKO mice developed cardiac ischemia/infarction, together with systolic dysfunction and left ventricular dilatation. CA was most severe at the aortic sinus level to an extent that no dKO mice survived to 20 weeks on the modified diet. None of control mice, however, developed CA or IHD. CONCLUSIONS: SR-BI deletion led to CA and IHD in LDL-R KO mice when fed the modified western-type diet. We established SR-BI/LDL-R dKO mice as a diet-induced murine model of human IHD and developed detection methods, using a combination of SPECT and Echo, for effective in vivo evaluation of cardiac functions.

Radiolabeled novel mAb 4G1 for immunoSPECT imaging of EGFRvIII expression in preclinical glioblastoma xenografts.

Epidermal growth factor receptor mutant III (EGFRvIII) is exclusively expressed in tumors, such as glioblastoma, breast cancer and hepatocellular carcinoma, but never in normal organs. Increasing evidence suggests that EGFRvIII has clinical significance in glioblastoma prognosis due to its enhanced tumorigenicity and chemo/radio resistance, thus the development of an imaging approach to early detect EGFRvIII expression with high specificity is urgently needed. To illustrate this point, we developed a novel anti-EGFRvIII monoclonal antibody 4G1 through mouse immunization, cell fusion and hybridoma screening and then confirmed its specificity and affinity by a serial of assays. Following biodistribution and small animal single-photon emission computed tomography (SPECT/CT) imaging of 125I-4G1 in EGFRvIII positive/negative tumor-bearing mice were performed and evaluated to verify the tumor accumulation of this radiotracer. The biodistribution indicated that 125I-4G1 showed prominent tumor accumulation at 24 h post-injection, which reached maximums of 11.20 ± 0.75% ID/g and 13.98 ± 0.57% ID/g in F98npEGFRvIII and U87vIII xenografts, respectively. In contrast, 125I-4G1 had lower tumor accumulation in F98npEGFR and U87MG xenografts. Small animal SPECT/CT imaging revealed that 125I-4G1 had a higher tumor uptake in EGFRvIII-positive tumors than that in EGFRvIII-negative tumors. This study demonstrates that radiolabeled 4G1 can serve as a valid probe for the imaging of EGFRvIII expression, and would be valuable into the clinical translation for the diagnosis, prognosis, guiding therapy, and therapeutic efficacy evaluation of tumors.

Hyaluronic Acid-Coated Silver Nanoparticles As a Nanoplatform for in Vivo Imaging Applications.

An efficient chemical reduction protocol has been developed for the synthesis of hyaluronic acid-coated silver nanoparticles (HA-Ag NPs) that are spherical, ultrasmall and monodisperse. The as-synthesized HA-Ag NPs not only exhibited excellent long-term stability and low cytotoxicity but also could be used as a nanoplatform for X-ray computed tomography (CT) and single-photon emission computed tomography (SPECT) imaging after being radiolabeled with 99mTc.

(99m)Tc-Cyclopentadienyl Tricarbonyl Chelate-Labeled Compounds as Selective Sigma-2 Receptor Ligands for Tumor Imaging.

We have designed and synthesized a series of cyclopentadienyl tricarbonyl rhenium complexes containing a 5,6-dimethoxyisoindoline or a 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline pharmacophore as σ2 receptor ligands. Rhenium compound 20a possessed low nanomolar σ2 receptor affinity (K(i) = 2.97 nM) and moderate subtype selectivity (10-fold). Moreover, it showed high selectivity toward vesicular acetylcholine transporter (2374-fold), dopamine D2L receptor, NMDA receptor, opiate receptor, dopamine transporter, norepinephrine transporter, and serotonin transporter. Its corresponding radiotracer [(99m)Tc]20b showed high uptake in a time- and dose-dependent manner in DU145 prostate cells and C6 glioma cells. In addition, this tracer exhibited high tumor uptake (5.92% ID/g at 240 min) and high tumor/blood and tumor/muscle ratios (21 and 16 at 240 min, respectively) as well as specific binding to σ receptors in nude mice bearing C6 glioma xenografts. Small animal SPECT/CT imaging of [(99m)Tc]20b in the C6 glioma xenograft model demonstrated a clear visualization of the tumor at 180 min after injection.

SPECT/NIRF Dual Modality Imaging for Detection of Intraperitoneal Colon Tumor with an Avidin/Biotin Pretargeting System.

We describe herein dual-modality imaging of intraperitoneal colon tumor using an avidin/biotin pretargeting system. A novel dual-modality probe, (99m)Tc-HYNIC-lys(Cy5.5)-PEG4-biotin, was designed, synthesized and characterized. Single-photon emission computed tomography/ computed tomography (SPECT/CT) imaging and near infrared fluorescence (NIRF) imaging were developed using intraperitoneal LS180 human colon adenocarcinoma xenografts. Following avidin preinjection for 4 hours, (99m)Tc-HYNIC-lys(Cy5.5)-PEG4-biotin could successfully detect colon tumors of different sizes inside the abdominal region using both modalities, and the imaging results showed no differences. Biodistribution studies demonstrated that the tumors had a very high uptake of the probe (99m)Tc-HYNIC-lys(Cy5.5)-PEG4-biotin (12.74 ± 1.89% ID/g at 2 h p.i.), and the clearance from blood and other normal tissues occured very fast. The low tumor uptake in the non-pretargeted mice (1.63 ± 0.50% ID/g at 2 h p.i.) and tumor cell staining results showed excellent tumor binding specificity of the pretargeting system. The ability of the novel probe to show excellent imaging quality with high tumor-to-background contrast, a high degree of binding specificity with tumors and excellent in vivo biodistribution pharmacokinetics should prove that the avidin/biotin based dual-modality pretargeting probe is a promising imaging tool during the entire period of tumor diagnosis and treatment.

Microarray based screening of peptide nano probes for HER2 positive tumor.

Peptides are excellent biointerface molecules and diagnostic probes with many advantages such as good penetration, short turnover time, and low cost. We report here an efficient peptide screening strategy based on in situ single bead sequencing on a microarray. Two novel peptides YLFFVFER (H6) and KLRLEWNR (H10) specifically binding to the tumor biomarker human epidermal growth factor receptor 2 (HER2) with aKD of 10(-8) M were obtained from a 10(5) library. Conjugated to nanoparticles, both the H6 and H10 probes showed specific accumulation in HER2-positive tumor tissues in xenografted mice by in vivo imaging.

Radioligand saturation binding for quantitative analysis of ligand-receptor interactions.

The reversible combination of a ligand with specific sites on the surface of a receptor is one of the most important processes in biochemistry. A classic equation with a useful simple graphical method was introduced to obtain the equilibrium constant, Kd, and the maximum density of receptors, Bmax. The entire 125I-labeled ligand binding experiment includes three parts: the radiolabeling, cell saturation binding assays and the data analysis. The assay format described here is quick, simple, inexpensive, and effective, and provides a gold standard for the quantification of ligand-receptor interactions. Although the binding assays and quantitative analysis have not changed dramatically compared to the original methods, we integrate all the parts to calculate the parameters in one concise protocol and adjust many details according to our experience. In every step, several optional methods are provided to accommodate different experimental conditions. All these refinements make the whole protocol more understandable and user-friendly. In general, the experiment takes one person less than 8 h to complete, and the data analysis could be accomplished within 2 h.