Feasibility Study of Single-Photon Emission Computed Tomography with Iodine-123 Labeled Metaiodobenzylguanidine for Preclinical Evaluation of Labetalol as a ß-Adrenergic Receptor Blocker.

Among clinically used radiopharmaceuticals, iodine-123 labeled metaiodobenzylguanidine ([123I]mIBG) serves for diagnosing neuroendocrine tumors and obtaining images of myocardial sympathetic innervation. mIBG, a structural analogue of norepinephrine (NE), a neurotransmitter acting in peripheral and central nerves, follows a pathway similar to NE, transmitting signals through the NE transporter (NET) located at synaptic terminals. It moves through the body without decomposing, enabling noninvasive image evaluation. In this study, we aimed to quantify [123I]mIBG uptake in the adrenal glands using small animal single-photon emission computed tomography/computed tomography (SPECT/CT) images post [123I]mIBG administration. We investigated the possibility of assessing the effectiveness of ß-adrenergic receptor blockers by quantifying SPECT/CT images and biodistribution results to determine the degree of [123I]mIBG uptake in the adrenal glands treated with labetalol, a known ß-adrenergic receptor blocker. Upon intravenous administration of [123I]mIBG to mice, SPECT/CT images were acquired over time to confirm the in vivo distribution pattern, revealing a clear uptake in the adrenal glands. Labetalol inhibited the uptake of [123I]mIBG in cell lines expressing NET. A decrease in [123I]mIBG uptake in the adrenal glands was observed in the labetalol-treated group compared with the normal group through SPECT/CT imaging and biodistribution studies. These results demonstrate that SPECT/CT imaging with [123I]mIBG could be applicable for evaluating the preclinical efficacy of new antihypertensive drug candidates such as labetalol, a ß-adrenergic receptor blocker.

Dilute lattice doping of 64Cu into 2D-nanoplates: its impact on radio-labeling efficiency and stability for target selective PET imaging.

A quintinite nanoplate (64Cu-QT-NP) isomorphically substituted with 64Cu, as the positron emission tomography (PET) imaging material, was prepared via two-step processes. A 64Cu labeling efficiency of 99% was realized, for the first time, by immobilizing the 64Cu radioisotope directly in the octahedral site of the 2-dimensional (2D) quintinite lattice. Furthermore, the 64Cu labeling stability of 64Cu-QT-NPs was also achieved to be more than ∼99% in various solutions such as saline, phosphate-buffered saline (PBS), and other biological media (mouse and human serums). In an in vivo xenograft mouse model, the passive targeting behavior of 64Cu-QT-NPs into tumor tissue based on the enhanced permeability and retention (EPR) effect was also demonstrated by parenteral administration, and successfully visualized using a PET scanner. For enhancing the tumor tissue selectivity, bovine serum albumin (BSA) was coated on 64Cu-QT-NPs to form 64Cu-QT-NPs/BSA, resulting in better colloidal stability and longer blood circulation time, which was eventually evidenced by the 2-fold higher tumor uptake rate when intravenousely injected in an animal model. It is, therefore, concluded that the present 64Cu-QT-NPs/BSA with tumor tissue selectivity could be an advanced nano-device for radio-imaging and diagnosis as well.

Therapeutic Response Monitoring with 89Zr-DFO-Pertuzumab in HER2-Positive and Trastuzumab-Resistant Breast Cancer Models.

Immuno-positron emission tomography (PET) has great potential to evaluate the target expression level and therapeutic response for targeted cancer therapy. Immuno-PET imaging with pertuzumab, due to specific recognition in different binding sites of HER2, could be useful for the determination of the therapeutic efficacy of HER2-targeted therapy, trastuzumab, and heat shock protein 90 (HSP90) inhibitor, in HER2-expressing breast cancer. The aim of this study is to evaluate the feasibility of monitoring therapeutic response with 89Zr-DFO-pertuzumab for the treatment of HER2-targeted therapeutics, trastuzumab, or the HSP90 inhibitor 17-DMAG, in trastuzumab-resistant JIMT-1 breast cancer models. We prepared an immuno-PET imaging agent using desferoxamine (DFO)-pertuzumab labeled with 89Zr and performed the biodistribution and PET imaging in breast cancer xenograft models for monitoring therapeutic response to HER2-targeted therapy. 89Zr-DFO-pertuzumab was successfully prepared and showed specific binding to HER2 in vitro and clearly visualized HER2 expressing JIMT-1 tumors. 89Zr-DFO-pertuzumab had prominent tumor uptake in HER2 expressing JIMT-1 tumors. JIMT-1 tumors showed trastuzumab-resistant and HSP90 inhibitor sensitive characterization. In immuno-PET imaging, isotype antibody-treated JIMT-1 tumors had similar uptake in trastuzumab-treated JIMT-1 tumors, but 17-DMAG-treated JIMT-1 tumors showed greatly reduced uptake compared to vehicle-treated tumors. Additionally, HER2 downregulation evaluated by immuno-PET imaging was verified by western blot analysis and immunofluorescence staining which resulted in a significant reduction in the tumor's HER2 level in 17-DMAG-treated JIMT-1 tumors. 89Zr-DFO-pertuzumab immuno-PET may be clinically translated to select pertinent patients for HER2-targeted therapy and to monitor the therapeutic response in HER2-positive cancer patients under various HER2-targeted therapeutics treatments.

Effects of packaging parameters on the microbial decontamination of Korean steamed rice cakes using in-package atmospheric cold plasma treatment.

The effects of packaging materials, package shape, and secondary packaging on the inactivation of indigenous mesophilic aerobic bacteria in Korean steamed rice cakes using in-package atmospheric dielectric barrier discharge cold plasma (ADCP) treatment were investigated. Inactivation of indigenous mesophilic aerobic bacteria by ADCP treatment (21 kV, 3 min) was significantly increased by 0.6 and 0.8 log CFU/g (p < 0.05) from 0.7 ± 0.1 and 0.5 ± 0.1 CFU/g, respectively, when polypropylene (PP) and low-density polyethylene (LDPE) were laminated with nylon, respectively. Secondary packaging lowered the inactivation level by 0.7-0.8 log CFU/g from 1.1 to 1.3 log CFU/g. In-package ADCP treatment did not alter the water vapor permeability, oxygen transmission rate, and tensile properties of PP, LDPE, nylon/PP, and nylon/LDPE. Thus, the results demonstrated that lamination of PP or LDPE with nylon and treatment before secondary packaging may be effective strategies for microbial inactivation by in-package ADCP treatment.

A preliminary clinical trial to evaluate 64Cu-NOTA-Trastuzumab as a positron emission tomography imaging agent in patients with breast cancer.

BACKGROUND: The purpose of this study was to evaluate both the biodistribution and safety of 64Cu-1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA)-Trastuzumab, a novel 64Cu-labeled positron emission tomography (PET) tracer for human epidermal growth factor receptor 2 (HER2) in patients with breast cancer. METHODS: PET images at 1, 24, and 48 h after 296 MBq of 64Cu-NOTA-Trastuzumab injection were obtained from seven patients with breast cancer. Both the primary tumors' and metastatic lesions' maximum standardized uptake value (SUVmax) was evaluated. The mean SUVmax (SUVmean) was evaluated in the other organs, including the blood pool, liver, kidney, muscle, spleen, bladder, and the lungs, as well as the bones. Moreover, the internal radiation dosimetry was calculated using the OLINDA/EXM software. Safety was assessed based on feedback regarding adverse reactions and safety-related issues within 1 month after 64Cu-NOTA-Trastuzumab administration. RESULTS: 64Cu-NOTA-Trastuzumab PET images showed that the overall SUVmean values in each organ negatively correlated with time. The liver's average SUVmean values were measured at 5.3 ± 0.7, 4.8 ± 0.6, and 4.4 ± 0.5 on 1 h, 24 h, and 48 h after injection, respectively. The average SUVmean blood values were measured at 13.1 ± 0.9, 9.1 ± 1.2, and 7.1 ± 1.9 on 1 h, 24 h, and 48 h after injection, respectively. The SUVmax of HER2-positive tumors was relatively higher than HER2-negative tumors (8.6 ± 5.1 and 5.2 ± 2.8 on 48 h after injection, respectively). Tumor-to-background ratios were higher in the HER2-positive tumors than in the HER2-negative tumors. No adverse events related to 64Cu-NOTA-Trastuzumab were reported. The calculated effective dose with a 296 MBq injection of 64Cu-NOTA-Trastuzumab was 2.96 mSv. The highest absorbed dose was observed in the liver (0.076 mGy/MBq), followed by the spleen (0.063 mGy/MBq), kidney (0.044 mGy/MBq), and heart wall (0.044 mGy/MBq). CONCLUSIONS: 64Cu-NOTA-Trastuzumab showed a specific uptake at the HER2-expressing tumors, thus making it a feasible and safe monitoring tool of HER2 tumor status in patients with breast cancer. TRIAL REGISTRATION: CRIS, KCT0002790. Registered 02 February 2018, https://cris.nih.go.kr.

A microdose clinical trial to evaluate [18F]Florastamin as a positron emission tomography imaging agent in patients with prostate cancer.

PURPOSE: To evaluate the biodistribution of [18F]Florastamin, a novel 18F-labelled positron emission tomography (PET) tracer for prostate-specific membrane antigen (PSMA) for the diagnosis of prostate cancer. METHODS: PET was performed for five healthy controls and 10 patients with prostate cancer at 0, 10, 30, 70, and 120 mins after injecting 370 MBq of [18F]Florastamin. The maximum standardised uptake value (SUVmax) was evaluated in the primary tumour. The mean SUVmax (SUVmean) was evaluated in normal organs. Furthermore, the residence time was evaluated by assessing radioactivity in each organ. The internal radiation dosimetry was calculated using the OLINDA/EXM software. RESULTS: The SUVmax in primary tumours increased with time. A favourable tumour to background ratio was also observed over time. Multiple lymph nodes and bone metastases were also evaluated and showed a similar pattern to SUVmax in the primary tumour. In one patient, a tiny lymph node metastasis was identified using [18F]Florastamin PET, which was not observed using other modalities, and was histologically confirmed. The highest absorbed dose was observed in the kidney (0.062 ± 0.015 mGy/MBq), followed by the bladder (0.032 ± 0.013 mGy/MBq), liver (0.022 ± 0.006 mGy/MBq), and salivary gland (0.018 ± 0.006 mGy/MBq). The effective dose with a 370 MBq injection of [18F]Florastamin was 1.81 mSv. No adverse events related to [18F]Florastamin were reported. CONCLUSION: We identified a novel PSMA-targeted PET ligand, [18F]Florastamin, for imaging prostate cancer. [18F]Florastamin showed a high SUVmax and relatively high tumour to background ratio in both primary tumour and metastatic lesions, which suggests its high sensitivity to detect tumours without any adverse events. TRIAL REGISTRATION: KCT0003924 registered at https://cris.nih.go.kr/ .

Small Animal PET Imaging of hTERT RNA-Targeted HSV1-tk Gene Expression with Trans-Splicing Ribozyme.

Background: Trans-splicing ribozymes (TSR) are useful anticancer agents targeting cancer-specific transcripts and replacing the RNA to induce anticancer gene expression specifically and selectively in cancer cells. Similar to other gene therapy methods, it is also important to evaluate the transgene expression for target specificity and ribozyme activity. Materials and Methods: In this study, the authors performed in vivo small animal positron emission tomography (PET) imaging and biodistribution assay to evaluate human telomerase reverse transcriptase (hTERT) RNA-targeting-specific TSR, which directs the expression of herpes simplex virus type 1 thymidine kinase (HSV1-tk) gene selectively in hTERT-positive tumors through targeted RNA replacement of the hTERT transcript. Results: The hTERT RNA-targeted HSV1-tk expression with TSR was monitored by PET imaging with 124I labeled 2'-fluoro-2'-deoxy-1-ß-D-arabinofuranosyl-5-iodouracil, which is one of the thymidine derivatives acting as substrates for HSV1-tk, in hTERT-positive tumor-bearing mice. Conclusions: Imaging of hTERT RNA-targeted HSV1-tk expression by TSR could be used in the development of advanced gene therapy using tumor-specific TSR.

Development of a Microbial Decontamination System Combining Washing with Highly Activated Calcium Oxide Solution and Antimicrobial Coating for Improvement of Mandarin Storability.

A new microbial decontamination system combining washing with a natural antimicrobial solution and coating with a carnauba wax (CW)-based antimicrobial coating was developed and its effects on mandarin storability were investigated. Mandarins were washed with an antimicrobial solution and/or coated with grapefruit seed extract-CW (GSE/CW). Values for the disease incidence of Penicillium digitatum in untreated mandarins; mandarins coated with GSE/CW without washing; and mandarins coated with GSE/CW after washing with a fumaric acid (FA) solution of slightly acidic electrolyzed water, a highly activated calcium oxide (CaO) aqueous solution, or CaO solution followed by FA solution were 96.0, 70.0, 78.8, 50.0, and 72.2%, respectively. GSE/CW coating after CaO washing was most effective in inhibiting P. digitatum growth during storage at 25 °C. Compared to untreated samples, GSE/CW coating alone or after CaO washing retained CO2 generation, firmness, and total polyphenol content of mandarins at 25 °C. Such treatments also effectively maintained mandarin pH, ascorbic acid concentration, and antioxidant capacity at both 4 and 25 °C. Moreover, GSE/CW coating after CaO washing more effectively inhibited P. digitatum growth at 25 °C and maintained ascorbic acid concentration and antioxidant capacity at 4 and 25 °C than GSE/CW coating alone. The microbial decontamination system integrating CaO washing and GSE/CW coating demonstrates potential for improving mandarin storability by inhibiting P. digitatum growth and improving the preservation of quality properties and sensory characteristics. PRACTICAL APPLICATION: This is the first study to develop a microbial decontamination system involving both washing with a natural antimicrobial solution and carnauba wax coating containing grapefruit seed extract to improve the storability of fruits. This system demonstrated a primary effect of inhibiting fungi that cause mandarin surface decay at 25 °C via the highly activated calcium oxide wash and secondary effects of delaying quality degradation and inhibiting fungal growth by the action of the antimicrobial coating. These effects led to improvements in mandarin storability, along with enhanced visual appeal while not affecting taste, flavor, or texture.

Development of a Theranostic Convergence Bioradiopharmaceutical for Immuno-PET Based Radioimmunotherapy of L1CAM in Cholangiocarcinoma Model.

PURPOSE: Cholangiocarcinoma is a malignancy of bile duct with a poor prognosis. Conventional chemotherapy and radiotherapy are generally ineffective, and surgical resection is the only curative treatment for cholangiocarcinoma. L1-cell adhesion molecule (L1CAM) has been known as a novel prognostic marker and therapeutic target for cholangiocarcinoma. This study aimed to evaluate the feasibility of immuno-PET imaging-based radioimmunotherapy using radiolabeled anti-L1CAM antibody in cholangiocarcinoma xenograft model. EXPERIMENTAL DESIGN: We prepared a theranostic convergence bioradiopharmaceutical using chimeric anti-L1CAM antibody (cA10-A3) conjugated with 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) chelator and labeled with 64Cu or 177Lu and evaluated the immuno-PET or SPECT/CT imaging and biodistribution with 64Cu-/177Lu-cA10-A3 in various cholangiocarcinoma xenograft models. Therapeutic efficacy and response monitoring were performed by 177Lu-cA10-A3 and 18F-FDG-PET, respectively, and immunohistochemistry was done by TUNEL and Ki-67. RESULTS: Radiolabeled cA10-A3 antibodies specifically recognized L1CAM in vitro, clearly visualized cholangiocarcinoma tumors in immuno-PET and SPECT/CT imaging, and differentiated the L1CAM expression level in cholangiocarcinoma xenograft models. 177Lu-cA10-A3 (12.95 MBq/100 µg) showed statistically significant reduction in tumor volumes (P < 0.05) and decreased glucose metabolism (P < 0.01). IHC analysis revealed 177Lu-cA10-A3 treatment increased TUNEL-positive and decreased Ki-67-positive cells, compared with saline, cA10-A3, or 177Lu-isotype. CONCLUSIONS: Anti-L1CAM immuno-PET imaging using 64Cu-cA10-A3 could be translated into the clinic for characterizing the pharmacokinetics and selecting appropriate patients for radioimmunotherapy. Radioimmunotherapy using 177Lu-cA10-A3 may provide survival benefit in L1CAM-expressing cholangiocarcinoma tumor. Theranostic convergence bioradiopharmaceutical strategy would be applied as imaging biomarker-based personalized medicine in L1CAM-expressing patients with cholangiocarcinoma.

Inactivation of Potato Polyphenol Oxidase Using Microwave Cold Plasma Treatment.

This study was conducted to examine the effects of microwave cold plasma (CP) treatment on inactivation of polyphenol oxidase (PPO) of potato. The PPO activity and treatment variables were fit to first-order kinetics, the Weibull model, and the second-order model. The optimum CP-generation power and treatment time for inactivating PPO in the PPO extract were found to be 900 W and 40 min, respectively, which resulted in the highest inactivation of PPO (49.5%). PPO activity after CP treatment of potato slices decreased from 72.4% to 59.0% as the sample surface-to-volume ratio increased from 7.1 to 9.0. CP treatment delayed the browning of potato slices. Microwave CP treatment effectively inactivated PPO in potatoes, demonstrating the potential of CP treatment for controlling PPO activity in foods. PRACTICAL APPLICATION: This study demonstrated that microwave CP treatment, a nonthermal food processing technology, inactivates PPO activity in potatoes. The results showed that the inactivation effect of CP treatment on PPO corresponded to the surface-to-volume ratio of potato slices. Furthermore, this study proposed an enzyme inactivation model that is suitable for predicting the inactivation of PPO activity and confirmed that CP treatment delayed browning in potatoes.

Development of 64Cu-NOTA-Trastuzumab for HER2 Targeting: A Radiopharmaceutical with Improved Pharmacokinetics for Human Studies.

The purpose of this study was to develop 64Cu-labeled trastuzumab with improved pharmacokinetics for human epidermal growth factor receptor 2 (HER2). Methods: Trastuzumab was conjugated with SCN-Bn-NOTA and radiolabeled with 64Cu. Serum stability and immunoreactivity of 64Cu-NOTA-trastuzumab were tested. Small-animal PET imaging and biodistribution studies were performed in a HER2-positive breast cancer xenograft model (BT-474). The internal dosimetry for experimental animals was determined using the image-based approach with the Monte Carlo N-particle code. Results:64Cu-NOTA-trastuzumab was prepared with high radiolabeling yield and radiochemical purity (>98%) and showed high stability in serum and good immunoreactivity. Uptake of 64Cu-NOTA-trastuzumab was highest at 48 h after injection as determined by PET imaging and biodistribution results in BT-474 tumors. The blood radioactivity concentrations of 64Cu-NOTA-trastuzumab decreased biexponentially with time in both mice with and mice without BT-474 tumor xenografts. The calculated absorbed dose of 64Cu-NOTA-trastuzumab was 0.048 mGy/MBq for the heart, 0.079 mGy/MBq for the liver, and 0.047 mGy/MBq for the spleen. Conclusion:64Cu-NOTA-trastuzumab was effectively targeted to the HER2-expressing tumor in vitro and in vivo, and it exhibited a relatively low absorbed dose due to a short residence time. Therefore, 64Cu-NOTA-trastuzumab could be applied to select the right patients and right timing for HER2 therapy, to monitor the treatment response after HER2-targeted therapy, and to detect distal or metastatic spread.

PET Imaging Biomarkers of Anti-EGFR Immunotherapy in Esophageal Squamous Cell Carcinoma Models.

Epidermal growth factor receptor (EGFR) is overexpressed and considered as a proper molecular target for diagnosis and targeted therapy of esophageal squamous cell carcinoma (ESCC). This study evaluated the usefulness of PET imaging biomarkers with 64Cu-PCTA-cetuximab and 18F-FDG-PET for anti-EGFR immunotherapy in ESCC models. In vivo EGFR status and glucose metabolism by cetuximab treatment were evaluated using 64Cu-PCTA-cetuximab and 18F-FDG-PET, respectively. Therapeutic responses with imaging biomarkers were confirmed by western blot and immunohistochemistry. TE-4 and TE-8 tumors were clearly visualized by 64Cu-PCTA-cetuximab, and EGFR expression on TE-8 tumors showed 2.6-fold higher uptake than TE-4. Tumor volumes were markedly reduced by cetuximab in TE-8 tumor (92.5 ± 5.9%), but TE-4 tumors were refractory to cetuximab treatment. The SUVs in 64Cu-PCTA-cetuximab and 18F-FDG-PET images were statistically significantly reduced by cetuximab treatment in TE-8 but not in TE-4. 64Cu-PCTA-cetuximab and 18F-FDG-PET images were well correlated with EGFR and pAkt levels. 64Cu-PCTA-cetuximab immuno-PET had a potential for determining EGFR level and monitoring therapeutic response by anti-EGFR therapy. 18F-FDG-PET was also attractive for monitoring efficacy of anti-EGFR therapy. In conclusion, PET imaging biomarkers may be useful for selecting patients that express target molecules and for monitoring therapeutic efficacy of EGFR-targeted therapy in ESCC patients.

Correction: Hypoxia/reoxygenation-experienced cancer cell migration and metastasis are regulated by Rap1- and Rac1-GTPase activation via the expression of thymosin beta-4.

[This corrects the article DOI: 10.18632/oncotarget.3218.].

Immuno-PET imaging based radioimmunotherapy in head and neck squamous cell carcinoma model.

The epidermal growth factor receptor (EGFR) is one of the most comprehensively studied molecular targets in head and neck squamous cell carcinoma (HNSCC). However, inherent and acquired resistance are serious problems and are responsible for limited clinical efficacy and tumor recurrence. In this study, we evaluated the feasibility of immuno-positron emission tomography (PET) imaging and radioimmunotherapy (RIT) with 64Cu-/177Lu-PCTA-cetuximab in cetuximab-resistant SNU-1066 HNSCC xenografted model. The cellular uptake of 64Cu/177Lu-3,6,9,15-tetraazabicyclo[9.3.1]-pentadeca-1(15),11,13-triene-3,6,9,-triacetic acid (PCTA)-cetuximab showed good correlation with western blot and flow cytometry analysis in EGFR expression level of various HNSCC cells. 177Lu-PCTA-cetuximab selectively killed cetuximab-resistant SNU-1066 cells in vitro. 64Cu-/177Lu-PCTA-cetuximab specifically accumulated in SNU-1066 tumor and those uptakes were peaked at 48 h and 7 day, respectively in biodistribution, PET and single-photon emission computed tomography/computed tomography (SPECT/CT) imaging. RIT with single dose of 177Lu-PCTA-cetuximab exhibited significant tumor regression and markedly reduced 2-[18F]fluoro-2-deoxy-D-glucose (18F-FDG) uptake, compared to other groups. Proliferation index were dramatically decreased and apoptotic index increased in RIT group. These results suggest that a diagnostic and therapeutic convergence radiopharmaceutical, 64Cu-/177Lu-PCTA-cetuximab has the potential of target selection using immuno-PET imaging and targeted therapy by RIT in EGFR expressing cetuximab-resistant HNSCC tumors.

Monitoring of macrophage accumulation in statin-treated atherosclerotic mouse model using sodium iodide symporter imaging system.

INTRODUCTION: Macrophages play a key role in atherosclerotic plaque formation in atherosclerosis, but its detailed understanding has poorly investigated until now. Thus, we sought to demonstrate a noninvasive technique for macrophage tracking to atherosclerotic lesions in apolipoprotein E-/-(ApoE-/-) mice with an imaging system based on sodium iodide symporter (NIS) gene coupled with 99mTc-single-photon emission computed tomography (SPECT). METHODS AND RESULTS: Macrophage cells (RAW264.7) were stably transduced with retrovirus expressing NIS gene (RAW-NIS). In RAW-NIS cells, uptake of 125I was higher than the parental cells. [18F]FDG signals in the aorta at 30weeks on an ApoE-/- mice with high cholesterol diet were higher (1.7±0.12% injected dose (ID)) than those in control group (0.84±0.06% ID). Through 99mTc-SPECT/computed tomography (CT), in the RAW-NIS cell injected group, the 99mTc-pertechnetate uptake in aorta was higher than control groups. However, according to atorvastatin treatment, RAW-NIS cell recruitment reduced to the aorta. Area of 99mTc-pertechnetate uptake was positively correlated with immunostaining results against macrophage antigen (CD68). Cholesterol and low-density lipoprotein levels of atorvastatin-treated group showed lower than those of atorvastatin-untreated group, but did not reach statistical difference. CONCLUSIONS: This novel approach to tracking macrophages to atherosclerotic plaques in vivo can be applied for studies of arterosclerotic vascular disease.

Stem Cell Monitoring with a Direct or Indirect Labeling Method.

The molecular imaging techniques allow monitoring of the transplanted cells in the same individuals over time, from early localization to the survival, migration, and differentiation. Generally, there are two methods of stem cell labeling: direct and indirect labeling methods. The direct labeling method introduces a labeling agent into the cell, which is stably incorporated or attached to the cells prior to transplantation. Direct labeling of cells with radionuclides is a simple method with relatively fewer adverse events related to genetic responses. However, it can only allow short-term distribution of transplanted cells because of the decreasing imaging signal with radiodecay, according to the physical half-lives, or the signal becomes more diffuse with cell division and dispersion. The indirect labeling method is based on the expression of a reporter gene transduced into the cell before transplantation, which is then visualized upon the injection of an appropriate probe or substrate. In this review, various imaging strategies to monitor the survival and behavior change of transplanted stem cells are covered. Taking these new approaches together, the direct and indirect labeling methods may provide new insights on the roles of in vivo stem cell monitoring, from bench to bedside.

Radioimmunotherapy with (131)I-rituximab as consolidation therapy for patients with diffuse large B-cell lymphoma.

PURPOSE: The aim of this study was to assess the clinical activity and toxicity of (131)I-rituximab as consolidation therapy for patients with diffuse large B-cell lymphoma (DLBCL) who were treated with R-CHOP (rituximab, cyclophosphamide, vincristine, doxorubicin, and prednisolone). METHODS: Patients who had been diagnosed with advanced stage (Ann Arbor III or IV) or bulky stage II DLBCL and achieved complete or partial response after six to eight cycles of R-CHOP were enrolled. RESULTS: A total of 16 patients were enrolled and treated with a single dose of (131)I-rituximab as consolidation therapy after the completion of six or eight cycles of R-CHOP between December 2005 and June 2011. This trial was terminated before the scheduled enrollment owing to low recruitment. Among the 16 patients who were treated with consolidative (131)I-rituximab, 6 achieved complete response (CR) after three cycles of R-CHOP, and another 9 patients further achieved CR after the completion of six or eight cycles of R-CHOP. During the median follow-up period of 73 months, only four patients (25 %) experienced relapse. Two-year relapse-free survival was 88 %, and 5-year relapse-free survival was 81 %. Grade 3 or 4 treatment-related toxicity occurred in four patients and included neutropenia and thrombocytopenia. CONCLUSIONS: (131)I-rituximab showed promising efficacy as consolidation treatment for patients with DLBCL. A future randomized phase III study to confirm our results is warranted.

Alpha-fetoprotein-targeted reporter gene expression imaging in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is one of the most common cancers in Eastern Asia, and its incidence is increasing globally. Numerous experimental models have been developed to better our understanding of the pathogenic mechanism of HCC and to evaluate novel therapeutic approaches. Molecular imaging is a convenient and up-to-date biomedical tool that enables the visualization, characterization and quantification of biologic processes in a living subject. Molecular imaging based on reporter gene expression, in particular, can elucidate tumor-specific events or processes by acquiring images of a reporter gene's expression driven by tumor-specific enhancers/promoters. In this review, we discuss the advantages and disadvantages of various experimental HCC mouse models and we present in vivo images of tumor-specific reporter gene expression driven by an alpha-fetoprotein (AFP) enhancer/promoter system in a mouse model of HCC. The current mouse models of HCC development are established by xenograft, carcinogen induction and genetic engineering, representing the spectrum of tumor-inducing factors and tumor locations. The imaging analysis approach of reporter genes driven by AFP enhancer/promoter is presented for these different HCC mouse models. Such molecular imaging can provide longitudinal information about carcinogenesis and tumor progression. We expect that clinical application of AFP-targeted reporter gene expression imaging systems will be useful for the detection of AFP-expressing HCC tumors and screening of increased/decreased AFP levels due to disease or drug treatment.

In vivo monitoring of CD44+ cancer stem-like cells by γ-irradiation in breast cancer.

There is increasing evidence that cancer contains cancer stem cells (CSCs) that are capable of regenerating a tumor following chemotherapy or radiotherapy. CD44 and CD133 are used to identify CSCs. This study investigated non-invasive in vivo monitoring of CD44-positive cancer stem-like cells in breast cancer by γ-irradiation using molecular image by fusing the firefly luciferase (fLuc) gene with the CD44 promoter. We generated a breast cancer cell line stably expressing fLuc gene by use of recombinant lentiviral vector controlled by CD44 promoter (MCF7-CL). Irradiated MCF7-CL spheres showed upregulated expression of CD44 and CD133, by immunofluorescence and flow cytometry. Also, gene expression levels of CSCs markers in irradiated spheres were clearly increased. CD44+ CSCs increased fLuc expression and tumor growth in vivo and in vitro. When MCF7-CL was treated with siCD44 and irradiated, CD44 expression was inhibited and cell survival ratio was decreased. MCF7-CL subsets were injected into the mice and irradiated by using a cobalt-60 source. Then, in vivo monitoring was performed to observe the bioluminescence imaging (BLI). When breast cancer was irradiated, relative BLI signal was increased, but tumor volume was decreased compared to non-irradiated tumor. These results indicate that increased CD44 expression, caused by general feature of CSCs by irradiation and sphere formation, can be monitored by using bioluminescence imaging. This system could be useful to evaluate CD44- expressed CSCs in breast cancer by BLI in vivo as well as in vitro for radiotherapy.

Immuno-PET Imaging and Radioimmunotherapy of 64Cu-/177Lu-Labeled Anti-EGFR Antibody in Esophageal Squamous Cell Carcinoma Model.

UNLABELLED: Immuno-PET provides valuable information about tumor location, phenotype, susceptibility to therapy, and treatment response, especially to targeted radioimmunotherapy. In this study, we prepared antiepidermal growth factor receptor (EGFR) antibody via identical chelator, 3,6,9,15-tetraazabicyclo[9.3.1]-pentadeca-1(15),11,13-trience-3,6,9,-triacetic acid (PCTA), labeled with (64)Cu or (177)Lu to evaluate the EGFR expression levels using immuno-PET and the feasibility of radioimmunotherapy in an esophageal squamous cell carcinoma (ESCC) model. METHODS: Cetuximab was conjugated with p-SCN-Bn-PCTA and radiolabeled with (64)Cu or (177)Lu. In vitro EGFR expression levels were determined and compared using flow cytometry and cell binding assay. In vivo EGFR expression levels were evaluated via immuno-PET imaging of (64)Cu-cetuximab and biodistribution analysis. Micro-SPECT/CT imaging, biodistribution, and radioimmunotherapy studies of (177)Lu-cetuximab were performed in the ESCC model. Therapeutic responses were monitored using (18)F-FDG PET and immunohistochemical staining. RESULTS: (64)Cu- or (177)Lu-labeled antibodies showed high radiolabeling yield (>98%), stability (>90%), and favorable immunoreactivity. In vitro EGFR status measured by cell binding assay was correlated with the flow cytometry data. Immuno-PET, micro-SPECT/CT, and biodistribution demonstrated specific uptake in ESCC tumors depending on the EGFR expression levels. Tumor accumulation of (64)Cu- and (177)Lu-cetuximab was peaked at 48 and 120 h, respectively. Radioimmunotherapy with (177)Lu-cetuximab showed significant inhibition of tumor growth (P < 0.01) and marked reduction of (18)F-FDG SUV compared with that of control (P < 0.05). Terminal deoxynucleotidyl transferase dUTP nick-end labeling positivity and Ki-67 staining indices increased and decreased, respectively, in the radioimmunotherapy group compared with other groups (P < 0.01). CONCLUSION: (64)Cu-cetuximab immuno-PET represented EGFR expression levels in ESCC tumors, and (177)Lu-cetuximab radioimmunotherapy effectively inhibited the tumor growth. The diagnostic and therapeutic convergence radiopharmaceutical (64)Cu-/(177)Lu-PCTA-cetuximab may be useful as a diagnostic tool in patient selection and a potent radioimmunotherapy agent in EGFR-positive ESCC tumors.