Gi Jeong Cheon

Preparation of a Promising Angiogenesis PET Imaging Agent: 68Ga-Labeled c(RGDyK)–Isothiocyanatobenzyl-1,4,7-Triazacyclononane-1,4,7-Triacetic Acid and Feasibility Studies in Mice

Arg-Gly-Asp (RGD) derivatives have been labeled with various radioisotopes for the imaging of angiogenesis in ischemic tissue, in which αvβ3 integrin plays an important role. In this study, cyclic Arg-Gly-Asp-d-Tyr-Lys [c(RGDyK)] was conjugated with 2-(p-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (SCN-Bz-NOTA) and then labeled with 68Ga. The labeled RGD so produced was subjected to an in vitro binding assay and in vivo biodistribution and PET studies. Methods: A mixture of SCN-Bz-NOTA (660 nmol) and c(RGDyK) (600 nmol) in 0.1 M sodium carbonate buffer (pH 9.5) was allowed to react for 20 h at room temperature in the dark for thiourea bond formation. The conjugate obtained was purified by semipreparative high-performance liquid chromatography (HPLC). The purified c(RGDyK)–SCN-Bz-NOTA (NOTA-RGD) was then labeled with 68Ga from a 68Ge/68Ga generator and purified by semipreparative HPLC. A competitive binding assay for c(RGDyK) and NOTA-RGD was performed with 125I-c(RGDyK) as a radioligand and αvβ3 integrin–coated plates as a solid phase. 68Ga-NOTA-RGD (0.222 MBq/100 μL) was injected, through a tail vein, into mice with hind limb ischemia and into mice bearing human colon cancer SNU-C4 xenografts. Biodistribution and imaging studies were performed at 1 and 2 h after injection. Results: The labeling of NOTA-RGD with 68Ga was straightforward. The Ki values of c(RGDyK) and NOTA-RGD were 1.3 and 1.9 nM, respectively. In the biodistribution study, the mean ± SD uptake of 68Ga-NOTA-RGD by ischemic muscles was 1.6 ± 0.2 percentage injected dose per gram (%ID/g); this uptake was significantly blocked by cold c(RGDyK) to 0.6 ± 0.3 %ID/g (P < 0.01). Tumor uptake was 5.1 ± 1.0 %ID/g, and the tumor-to-blood ratio was 10.3 ± 4.8. Small-animal PET revealed rapid excretion through the urine and high levels of tumor and kidney uptake. Conclusion: Stable 68Ga-NOTA-RGD was obtained in a straightforward manner at a high yield and showed a high affinity for αvβ3 integrin, specific uptake by angiogenic muscles, a high level of uptake by tumors, and rapid renal excretion. 68Ga-NOTA-RGD was found to be a promising radioligand for the imaging of angiogenesis.

Intracranial Ganglioglioma: Preoperative Characteristics and Oncologic Outcome after Surgery

In order to investigate the clinical characteristics, neuroimaging findings, pathological features, treatment, and outcomes, and to provide valuable guidance for the diagnosis and management of intracranial gangliogliomas, 34 cases of intracranial gangliogliomas were retrospectively analyzed.This study included 23 males and 11 females. Age at operation ranged from 17 days to 50 years. All patients had preoperative magnetic resonance imaging (MRI). Computed tomography (CT), magnetic resonance spectroscopy (MRS), 18F-FDG–PET (positron emission tomography), and 99Tc-HMPAO-SPECT (single photon emission computed tomography) were also performed in some cases. All pathological specimens and all available neuroimages were re-evaluated. The follow-up period varied from 12 to 89 months (mean 36 months). Seizure was the most common presenting symptom (85%). Tumor calcification was detected by CT scan in six of 11 cases. Seventeen gangliogliomas (50%) showed cystic components and 18 tumors (53%) were enhanced on MRI. All temporal lobe gangliogliomas were located intracortically and most of them had poor demarcation on MRI. In comparison with the contralateral normal area, the gangliogliomas showed a reduced Cho/Cr and NAA/Cr ratio, and an increased Cho/NAA ratio. On 18F-FDG-PET, gangliogliomas were usually hypometabolic. HMPAO-SPECT indicated tumor hypoperfusion or isoperfusion. A gross total resection was achieved in 25 patients. Tumor progression was observed in three patients who underwent an incomplete tumor resection. Two of them underwent a malignant transformation to a glioblastoma. Twenty-seven patients could carry on their normal life activity with the Karnofsky Performance Scale (KPS) of more than 80.Even though ganglioglioma is a slowly growing benign tumor, which could be demonstrated by magnetic resonance spectroscopy (MRS), PET, and SPECT, there is a chance of malignant transformation, especially in cases of incomplete tumor resection. Gangliogliomas should be resected gross totally, if feasible, to achieve the best long-term outcomes.

Prediction Model of Chemotherapy Response in Osteosarcoma by 18F-FDG PET and MRI

Response to neoadjuvant chemotherapy is a significant prognostic factor for osteosarcoma; however, this information can be determined only after surgical resection. If we could predict histologic response before surgery, it might be helpful for the planning of surgeries and tailoring of treatment. We evaluated the usefulness of 18F-FDG PET for this purpose. Methods: A total of 70 consecutive patients with a high-grade osteosarcoma treated at our institute were prospectively enrolled. All patients underwent 18F-FDG PET and MRI before and after neoadjuvant chemotherapy. We analyzed the predictive values of 5 parameters, namely, maximum standardized uptake values (SUVs), before and after (SUV2) chemotherapy, SUV change ratio, tumor volume change ratio, and metabolic volume change ratio (MVCR) in terms of their abilities to discriminate responders from nonresponders. Results: Patients with an SUV2 of less than or equal to 2 showed a good histologic response, and patients with an SUV2 of greater than 5 showed a poor histologic response. The histologic response of a patient with an intermediate SUV2 (2 < SUV2 ≤ 5) was found to be predictable using MVCR. A patient with an MVCR of less than 0.65 is likely to be a good responder, whereas a patient with an MVCR of greater than or equal to 0.65 is likely to be a poor responder. According to our model, the predictive values for good responders and poor responders were 97% (31/32) and 95% (36/38), respectively. Conclusion: We found that combined information on 18F-FDG PET and MRI scans, acquired before and after chemotherapy, could be used to predict histologic response to neoadjuvant chemotherapy in osteosarcoma.

Apoptosis-inducing antitumor efficacy of hexokinase II inhibitor in hepatocellular carcinoma

Hypoxia stimulates hepatocellular carcinoma (HCC) cell growth via hexokinase (HK) II induction, and alternatively, HK II inhibition induces apoptosis by activating mitochondrial signaling. This study was to investigate whether the induction of HK II by hypoxia is associated with enhanced mitochondrial stability and to confirm the apoptosis-inducing efficacy of HK II inhibitor in an in vivo model of HCC. Mitochondrial stability was examined by treating isolated mitochondria with deoxycholate, a permeability-enhancing agent. Alteration of permeability transition pore complex composition was analyzed by immunoprecipitation and immunoblotting. An in vivo model of HCC was established in C3H mice i.d. implanted with MH134 cells. The antitumor efficacy of i.p. given 3-bromopyruvate (3-BrPA), a HK II inhibitor, was evaluated by measuring tumor volumes and quantifying apoptosis using terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling staining and 99mTc-hydrazinonicotinamide-Annexin V scans. Hypoxia enhanced mitochondrial stability, and this was inhibited by 3-BrPA treatment. In particular, HK II levels in permeability transition pore complex immunoprecipitates were reduced after 3-BrPA treatment. In mice treated with 3-BrPA, mean tumor volumes and tumor volume growth were found to be significantly reduced. Moreover, percentages of terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling–positive cells were significantly increased in 3-BrPA–treated mice, and this apoptosis-inducing efficacy was reflected in vivo by 99mTc-hydrazinonicotinamide-Annexin V imaging. Our results show that hypoxia enhances mitochondrial stability via HK II induction and that HK II inhibitor treatment exhibits an in vivo antitumor effect by inducing apoptosis. Therefore, HK II inhibitors may be therapeutically useful for the treatment of advanced infiltrative hypovascular HCCs, which are growing in a hypoxic environment. [Mol Cancer Ther 2007;6(9):2554–62]

Characterization and Cancer Cell Specific Binding Properties of Anti-EGFR Antibody Conjugated Quantum Dots

Synthesis of biologically active antibody conjugated quantum dots (QDs) has been of great importance in cellular imaging and diagnostics. Cetuximab (or Erbitux) is the first monoclonal antibody drug which targets the epidermal growth factor receptor (EGFR) overexpressed in most cancer cells. In the present work, we investigated three different conjugation strategies to obtain the biologically functional QD-cetuximab conjugates for the tumor-specific imaging. Successful conjugation of cetuximab to QDs was achieved using PEG conjugated polymer-coated QDs and two long-chain heterobifunctional linkers, sulfo-LC-SPDP and sulfo-SMCC. The dissociation constant of the QD-cetuximab conjugates to EGFR was determined to be 0.61 +/- 0.28 nM. The cancer cell-specific binding ability of the QD-cetuximab conjugates was evaluated in vitro, and the cellular internalization of the QD-cetuximab conjugates was clearly demonstrated in live cells by confocal microscopy. The cellular imaging experiments using the QD-cetuximab conjugates showed a clear endocytosis pathway, which was evidenced by the colocalization of the QD-cetuximab conjugates with dye-labeled transferrin. These results suggest that the QD-cetuximab conjugates as an imaging modality for tumor EGFR overexpression can be expected to provide important information on the expression levels of EGFR on the cancer cells.

In Vivo Differentiation of Human Amniotic Epithelial Cells Into Cardiomyocyte-Like Cells and Cell Transplantation Effect on Myocardial Infarction in Rats: Comparison With Cord Blood and Adipose Tissue-Derived Mesenchymal Stem Cells

Human amniotic epithelial cells (h-AECs), which have various merits as a cell source for cell therapy, are known to differentiate into cardiomyocytes in vitro. However, the ability of h-AECs to differentiate into cardiomyocytes in vivo and their cell transplantation effects on myocardial infarction are still unknown. In this study, we assessed whether h-AECs could differentiate into cardiomyocytes in vivo and whether h-AECs transplantation can decrease infarct size and improve cardiac function, in comparison to transplantation of cord blood-derived mesenchymal stem cells (MSCs) or adipose tissue-derived MSCs. For our study, we injected h-AECs, cord blood-derived MSCs, adipose tissue-derived MSCs, and saline into areas of myocardial infarction in athymic nude rats. After 4 weeks, 3% of the surviving h-AECs expressed myosin heavy chain, a marker specific to the myocardium. Compared with the saline group, all cell-implanted groups showed a higher ejection fraction, lower infarct area by positron emission tomography and histology, and more abundant myocardial gene and protein expression in the infarct area. We showed that h-AECs can differentiate into cardiomyocyte-like cells, decrease infarct size, and improve cardiac function in vivo. The beneficial effects of h-AECs were comparable to those of cord blood and adipose tissue-derived MSCs. These results support the need for further studies of h-AECs as a cell source for myocardial regeneration due to their plentiful availability, low immunity, and lack of ethical issues related to their use.

18F-FDG uptake and EGFR mutations in patients with non-small cell lung cancer: A single-institution retrospective analysis

This retrospective study was performed to evaluate a possible association between the presence of epidermal growth factor receptor (EGFR) mutations and the standardized uptake value (SUV) of (18)F-fluoro-2-deoxy-glucose ((18)F-FDG) uptake in patients with non-small cell lung cancer (NSCLC). We included 100 patients who were tested for EGFR mutations by direct sequencing of resected tissues and who underwent preoperative positron emission tomography/computed tomography at the time of diagnosis. The maximum SUV by the primary tumor was chosen for further analysis. EGFR mutations in exons 19 and 21 were detected in 21 NSCLC patients (21%). EGFR mutations were more frequent in never-smokers than ever-smokers (35% versus 11%; P=0.003), in adenocarcinomas than non-adenocarcinomas (34% versus 6%; P=0.001), and in females than males (41% versus 12%; P=0.001). The SUV ranged from 1.3 to 33.0 (median 10.6). Area under receiver operating characteristic curve for SUVs in respect to the presence of EGFR mutations was 0.74 (95% CI: 0.62-0.85). When a cut off value was used, patients with low SUVs were more likely to have EGFR mutations than those with high SUVs (40% versus 11%; P=0.001). On multivariate analysis, a low SUV remained a significant predictors for EGFR mutations (P=0.025). (18)F-FDG uptake was associated with the presence of EGFR mutation. These results extrapolate that (18)F-FDG uptake might be helpful to discriminate patients who harbor EGFR mutations, especially when a genetic test is not feasible.

Revival of TE2A; a better chelate for Cu(II) ions than TETA?

A highly effective synthetic route for TE2A was developed and the (64)Cu-labeled TE2A complexes showed higher kinetic inertness and faster clearance than most commonly used TETA analogs.

Radiation sensitivity depends on OGG1 activity status in human leukemia cell lines

To assess the role of 8-oxoguanine glycosylase (OGG1) in the cell defense against radiation injury, the radiation-induced cytotoxicities were compared between the mutant type KG-1 featuring a loss of OGG1 activity due to a homozygous mutation of Arg 229 Gln, and the wild type U937. While the following three obvious toxicities were displayed in KG-1, they were observed only minimally in U937. These were: a dramatic arrest at the G2/M phase indicated by a marked increase in both the number of G2/M cells and the expression of cyclin B1, cdc2, and mitotic phosphoprotein monoclonal-2 (MPM-2)-reactive proteins; a severe apoptosis shown by a marked increase in the number of cells with hypo-diploid DNA and DNA fragmentation; and as a result, a severe inhibition of cell growth and proliferation measured by the MTT test and [(3)H]-thymidine uptake assay. As expected, KG-1 exhibited a significant increase in the 8-hydroxyguanine level in DNA whereas U937 did not. However, the level of irradiation-induced lipid peroxidation was almost the same in both cell lines. All of these symptoms shown by KG-1 were observed in Molt-4 and CEM-CM3, which were also found to feature low OGG1 activity. These findings suggest that OGG1 plays an important role in cell survival from radiation-induced damage and are also indicative of the capability of 8-hydroxyguanine in DNA to induce cellular toxicities.

18F-Fluoro-2-Deoxy-Glucose Uptake Predicts Clinical Outcome in Patients with Gefitinib-Treated Non–Small Cell Lung Cancer

Purpose: To evaluate response and survival according to 18F-fluoro-2-deoxy-glucose uptake at presentation in patients with gefitinib-treated non–small cell lung cancer. Experimental Design: We retrospectively analyzed 84 positron emission tomography/computed tomography findings. Patient characteristics, response rates, and survivals were evaluated according to the maximum standardized uptake value (SUV) of primary tumor. The cutoff value of SUVs was obtained from receiver operating characteristic analysis. Results: The response rate (RR) was higher for never-smokers (41%) than ever-smokers (9%; P = 0.001). Patients with adenocarcinoma showed higher RR than those with other tumor histopathology (35% versus 9%; P = 0.009). The SUV was significantly lower in patients who were never-smokers (P = 0.005), patients with adenocarcinoma (P < 0.001), and female patients (P = 0.017). Patients with a low SUV showed higher RR compared with those with a high SUV (53% versus 18%; P = 0.003). Prolonged progression-free survival was observed in patients with low SUVs compared with those with high SUVs (median, 33.1 weeks versus 8.6 weeks; P = 0.003). While controlling for performance status, smoking history, and pathology, the high SUV conferred unfavorable outcome (hazard ratio, 2.3; P = 0.012). In terms of overall survival, a low SUV was associated with favorable outcome in univariate analysis (P = 0.011). Patients with a low SUV showed prolonged survival in multivariate analysis (P = 0.043). Conclusions: These results suggest that low SUVs at presentation can predict favorable response and survival in gefitinib-treated non–small cell lung cancer patients.