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Video 1. Time-lapse DIC Imaging. Time-lapse sequential DIC images (video) showed swelling and then shrinkage of the cell after NIR light irradiation in cells treated with tra-IR700 (50 min observation). Flashing light is NIR light irradiation (2 J/cm2).(10sec interval, total 50min)

Supplementary Figures 1-5. Video Captions (Video 1 and 2) Supplementary Figure 1. Targeted necrotic cell death observed after NIR-PIT in vitro. Supplementary Figure 2. Necrotic cell death evaluated on serial bioluminescence imaging after NIR-PIT Supplementary Figure 3.In vivo tumor inhibition by NIR-PIT in flank model Supplementary Figure 4. In vivo fluorescence imaging of tumor bearing mice before and after NIRPIT Supplementary Figure 5. Mesothelin targeted necrotic cell death observed after NIR-PIT in vitro

Video 2. Time-lapse PI Imaging. Time-lapse sequential PI images (video) showed rapid membrane damage detected by PI staining after NIR light irradiation in cells treated with tra-IR700 (50 min observation). Flashing light is NIR light irradiation (2 J/cm2).(10sec interval, total 50min)

Table S1. Biodistribution of radioactivity in mice after injection of 67Ga-NOTA-Fab, 67Ga-NOTA-MI-Fab and 67Ga-NOTA-MVK-Fab. Table S2. Biodistribution of radioactivity in nude mice bearing SY cells after 3 h injection of 67Ga-NOTA-Fab, 67Ga-NOTA-MI-Fab and 67Ga-NOTA-MVK-Fab. Table S3. Stability of 67Ga-labeled Fab fragments in murine serum. Scheme S1. Synthetic procedure for NOTA-MVK-Mal. Scheme S2. Synthetic procedure for NOTA-MVK-Bzo.

Purpose: This study was undertaken to evaluate the renal radioactivity levels of a newly designed 67Ga-labeled antibody fragment with a linkage cleaved by enzymes present on the brush border membrane (BBM) lining the lumen of the renal tubule.Experimental Design: 67Ga-labeled S-2-(4-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (SCN-Bn-NOTA) was conjugated with an antibody Fab fragment through a Met-Val-Lys linkage (67Ga-NOTA-MVK-Fab) considering that a Met-Val sequence is a substrate of enzymes on the renal BBM and 67Ga-NOTA-Met is excreted from the kidney into the urine. The enzymatic recognition of the linkage was evaluated with a low-molecular-weight 67Ga-NOTA-Met-Val-Lys derivative. Biodistribution of radioactivity after injection of 67Ga-NOTA-MVK-Fab into mice was compared with 67Ga-NOTA-conjugated Fab fragments through a Met-Ile linkage that liberates 67Ga-NOTA-Met (67Ga-NOTA-MI-Fab) or a conventional thiourea linkage (67Ga-NOTA-Fab).Results: The MVK linkage remained stable in plasma and was recognized by enzymes on renal BBM to liberate 67Ga-NOTA-Met. When injected into mice, all three 67Ga-labeled Fab exhibited similar blood clearance rates and tumor accumulation. Significant differences were observed in the kidney where 67Ga-NOTA-MVK-Fab registered the lowest renal radioactivity levels from early postinjection time (P < 0.05), followed by 67Ga-NOTA-MI-Fab, which was well reflected in the SPECT/CT images.Conclusions: These findings indicated that our proposal of liberating a radiolabeled compound to urinary excretion from antibody fragments at the renal BBM to reduce the renal radioactivity levels was applicable to 67/68Ga-labeled antibody fragments. Because antibody fragments and constructs share similar metabolic fates in the kidney, the present labeling procedure would also apply to a variety of antibody fragments and constructs of interest. Clin Cancer Res; 24(14); 3309–16. ©2018 AACR.

Introduction: 3-[18F]fluoro-α-methyl-L-tyrosine ([18F]FAMT) is a promising amino acid tracer targeting L-type amino acid transporter 1 (LAT1). One concern regarding the diagnosis using [18F]FAMT is the possibility of false-negative findings because of its relatively low accumulation level even in malignant tumors. Moreover, preloading probenecid, an organic anion transporter inhibitor, markedly increased the tumor accumulation level of radioiodine-labeled α-methyltyrosine. In this study, we evaluated the usefulness of preloading probenecid in improving the tumor-imaging capability of [18F]FAMT. Methods: Three biodistribution studies of [18F]FAMT were conducted in normal mice to elucidate the usefulness of probenecid preloading. Then, a biodistribution study and positron emission tomography (PET) imaging of [18F]FAMT were conducted with or without probenecid injection in tumor-bearing mice. Results: Probenecid preloading significantly delayed blood clearance and consequently enhanced the accumulation of [18F]FAMT in the pancreas, a LAT1-positive organ. The effects of probenecid preloading were independent of the administration route. Tumor accumulation level in the biodistribution study and the maximum standardized uptake value in tumors on PET imaging of the probenecid preloading group were significantly higher than those of the control (without probenecid injection) group in tumor-bearing mice. Conclusions: Preloading probenecid significantly delayed blood clearance and consequently enhanced the accumulation of [18F]FAMT in tumors. These results indicate that preloading probenecid could improve the diagnostic accuracy of [18F]FAMT.

Urinary fatty acid binding protein 1 (FABP1, also known as liver-type FABP) has been implicated as a biomarker of acute kidney injury (AKI) in humans. However, the precise biological mechanisms underlying its elevation remain elusive. Here, we show that urinary FABP1 primarily reflects impaired protein reabsorption in proximal tubule epithelial cells (PTECs). Bilateral nephrectomy resulted in a marked increase in serum FABP1 levels, suggesting that the kidney is an essential organ for removing serum FABP1. Injected recombinant FABP1 was filtered through the glomeruli and robustly reabsorbed via the apical membrane of PTECs. Urinary FABP1 was significantly elevated in mice devoid of megalin, a giant endocytic receptor for protein reabsorption. Elevation of urinary FABP1 was also observed in patients with Dent disease, a rare genetic disease characterized by defective megalin function in PTECs. Urinary FABP1 levels were exponentially increased following acetaminophen overdose, with both nephrotoxicity and hepatotoxicity observed. FABP1-deficient mice with liver-specific overexpression of FABP1 showed a massive increase in urinary FABP1 levels upon acetaminophen injection, indicating that urinary FABP1 is liver-derived. Lastly, we employed transgenic mice expressing diphtheria toxin receptor (DT-R) either in a hepatocyte- or in a PTEC-specific manner, or both. Upon administration of diphtheria toxin (DT), massive excretion of urinary FABP1 was induced in mice with both kidney and liver injury, while mice with either injury type showed marginal excretion. Collectively, our data demonstrated that intact PTECs have a considerable capacity to reabsorb liver-derived FABP1 through a megalin-mediated mechanism. Thus, urinary FABP1, which is synergistically enhanced by concurrent liver injury, is a biomarker for impaired protein reabsorption in AKI. These findings address the use of urinary FABP1 as a biomarker of histologically injured PTECs that secrete FABP1 into primary urine, and suggest the use of this biomarker to simultaneously monitor impaired tubular reabsorption and liver function. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Excess lipid accumulation is associated with obesity-related chronic kidney disease, but the mechanisms of fatty acid (FA) uptake have been poorly understood. To this end, we investigated how FAs are taken up by tubular epithelial cells (TECs) in mice by using in vivo FA tracing and histological methods. Immunohistochemistry showed that CD36, which is a well-known FA transporter, was abundantly expressed on the basolateral side of proximal TECs (PTECs). The uptake of 125I-BMIPP (a radiolabeled FA tracer) was significantly reduced in CD36-knockout kidneys at 1 min after injection. In vivo imaging with multiphoton microscopy revealed that BODIPY-C12 (a fluorescence-labeled FA tracer) accumulated on both the basolateral and apical sides of PTECs. Numerous lipid droplets accumulated in PTECs after accelerated lipolysis. Furthermore, PTEC-specific injury via diphtheria toxin (DT) injection in transgenic mice expressing the DT receptor resulted in a compensatory increase in lipid accumulation in downstream TECs. Importantly, urinary FAs were undetectable, even in mice and humans with remarkable albuminuria. Our data demonstrate that renal TECs take up FAs from blood (CD36-dependent) and primary urine (CD36-independent) and can store excess FAs as neutral lipids. The results further show that renal tubules have hitherto largely unappreciated mechanisms by which the excretion of FAs into the urine is avoided.

Pretargeting radioimmunotherapy (PRIT) is a promising approach that can reduce long-time retention of blood radioactivity and consequently reduce hematotoxicity. Among the PRIT strategies, the combination of biotin-conjugated mAb and radiolabeled streptavidin (StAv) is a simple and convenient method because of its ease of preparation. This study performed three-step (3-step) PRIT using the sequential injection of (1) biotinylated bevacizumab (Bt-BV), (2) avidin, and (3) radiolabeled StAv for the treatment of triple-negative breast cancer (TNBC). Four biodistribution studies were performed using 111In in tumor-bearing mice to optimize each step of our PRIT methods. Further, a therapeutic study was performed with optimized 3-step PRIT using 90Y-labeled StAv. Based on the biodistribution studies, the protein dose of Bt-BV and avidin was optimized to 100 μg and 10 molar equivalent of BV, respectively. Succinylation of StAv significantly decreased the kidney accumulation level (with succinylation (6.96 ± 0.91) vs without succinylation (20.60 ± 1.47) at 1 h after injection, p

Targeted α-radionuclide therapy has growing attention as a promising therapy for refractory cancers. However, the application is limited to certain types of cancer. Since L-type amino acid transporter 1 (LAT1) is highly expressed in various human cancers, we prepared LAT1-selective α-emitting amino acid analog, 2-[211At]astato-α-methyl-L-phenylalanine (2-[211At]AAMP), and evaluated its potential as a therapeutic agent. Methods: 2-[211At]AAMP was prepared from the stannyl precursor. Stability of 2-[211At]AAMP was evaluated by both in vitro and in vivo. In vitro studies using LAT1 expressing human ovarian cancer cell line, SKOV3, were performed for evaluating cellular uptake and cytotoxicity of 2-[211At]AAMP. Biodistribution and therapeutic studies in SKOV3 bearing mice were performed after intravenous injection of 2-[211At]AAMP. Results: 2-[211At]AAMP was stable in murine plasma in vitro and excreted into urine as intact. Cellular uptake of 2-[211At]AAMP was inhibited by treatment with LAT1-selective inhibitor. After 24 hours of incubation, 2-[211At]AAMP suppressed clonogenic growth at 10 kBq/ml, and induced cell death and DNA double-strand break at 25 kBq/ml. When injected to mice, 2-[211At]AAMP exhibited the peak accumulation in the tumor at 30 min postinjection, and the radioactivity levels in the tumor retained up to 60 min. The majority of the radioactivity was rapidly eliminated from the body into the urine as an intact form immediately after injection. 2-[211At]AAMP significantly improved the survival of mice (P

The high and persistent renal radioactivity levels after injection of radiolabeled low-molecular-weight polypeptides constitute a significant problem for their diagnostic and therapeutic applications, especially when they are labeled with metallic radionuclides. To improve the renal radioactivity levels of technetium-99m (99mTc)-labeled Fab fragments, a mercaptoacetyltriglycine (MAG3)-based new bifunctional chelating agent with a cleavable glycyl-phenylalanyl-lysine (GFK) linkage, MAG3-GFK-suc-TFP, was designed, synthesized, and evaluated. 99mTc-labeled Fab was obtained by reacting MAG3-GFK-Fab conjugate with 99mTc-glucarate. The GFK linkage remained stable in plasma but was cleaved by enzymes on the renal brush border membrane. The comparative biodistribution studies with indium-111 (111In)-labeled Fab using SCN-CHX-A″-DTPA showed that while both radiolabeled Fabs exhibited similar elimination rates from the blood, [99mTc]Tc-MAG3-GFK-Fab registered much lower renal radioactivity levels from 30 min post-injection onward due to the release and subsequent urinary excretion of [99mTc]Tc-MAG3-Gly. However, [99mTc]Tc-MAG3-GFK-Fab showed an increase in the intestinal radioactivity levels with the time that was not observed with 111In-labeled Fab. The analysis of the intestinal contents suggested the redistribution of [99mTc]Tc-MAG3-Gly to the intestine. The retrospective comparison of [99mTc]Tc-MAG3-GFK-Fab with the radiolabeled Fabs so far prepared under the identical concept suggested that some portion of [99mTc]Tc-MAG3-Gly was generated after the coated vesicle formation and they were excreted into the blood, and subsequently redistributed in the intestine via hepatobiliary excretion. In conclusion, MAG3-GFK-suc-TFP provided 99mTc-labeled Fabs that exhibit low renal radioactivity shortly after injection by the post-labeling procedure. The present study indicated that, contrary to our earlier proposal, the generation of the radiometabolites would proceed not only during the internalization process of the parental antibody fragments but also after coated vesicle formation. This study also showed that the intracellular behaviors of radiometabolites played crucial roles in the elimination rates and the routes of the radioactivity from the kidney.

L-2-[18 F]fluoro-alpha-methylphenylalanine (2-[18 F]FAMP) is a promising amino acid tracer for positron emission tomography (PET) imaging, yet the low production yield of direct electrophilic radiofluorination with [18 F]F2 necessitates further optimization of the radiolabeling process. This paper describes a two-step preparation method for L-2-[18 F]fluoro-alpha-methylphenylalanine (2-[18 F]FAMP) starting from [18 F]fluoride. The (Mesityl)(L-alpha-methylphenylalanine)-2-iodonium tetrafluoroborate precursors with various protecting groups were prepared. The copper-mediated 18 F-fluorination of the iodonium salt precursors successfully produced 2-[18 F]FAMP. The highest radio chemical conversion of 57.6% was noted with N-Piv-protected (mesityl)(aryl)iodonium salt in the presence of 5 equivalent of Cu (OTf)2 . Subsequent deprotection with 57% hydrogen iodide produced 2-[18 F]FAMP within 120 min in 21.4 ± 11.7% overall radiochemical yield with >95% radiochemical purity and an enantiomeric excess >99%. The obtained 2-[18 F]FAMP showed comparable biodistribution profiles in normal mice with that of the carrier-added 2-[18 F]FAMP. These results indicate that usefulness of copper mediated 18 F-fluorination for the production of 2-[18 F]FAMP, which would facilitate clinical translation of the promising tumor specific amino acid tracer. Individual facilities could adopt either production method based on radioactivity demand and equipment availability.

Objectives: Molecular imaging constitutes a promising technique for the early detection of rheumatoid arthritis (RA). Macrophages and hypoxia play significant roles in inflamed synovium. In the pre...

Although 2-18F-fluoro-2-deoxy-glucose (18F-FDG) has established roles in the diagnosis of a variety of cancers, it has limited value in the detection of primary/recurrent lesions in the bladder, mainly because of interference by the pooled radioactivity in the urine. Our previous study revealed promising properties of l- and d-2-18F-α-methyl-phenylalanine (2-18F-FAMP) as radiotracers; i.e., their rapid blood clearance and low renal accumulation. In the present study we evaluated the utility of l- and d-2-18F-FAMP for imaging bladder cancer in a mouse model. We used the human bladder cancer cell line HT1376 to prepare a bladder cancer xenograft model in mice bearing both orthotopic and subcutaneous tumors. Biodistribution and PET imaging studies were performed at 1 and 3 h after injection of l-2-18F-FAMP or d-2-18F-FAMP. 18F-FDG was used as a control. At 1 h after injection, greater accumulations of both l-2-18F-FAMP and d-2-18F-FAMP were observed in the orthotopic tumors compared to 18F-FDG. The orthotopic tumor-to-muscle ratio of d-2-18F-FAMP was significantly higher than that of 18F-FDG (p

Introduction: Non-invasive diagnosis of endometriosis remains challenging. A promising approach for diagnosing endometriosis is the molecular imaging of vascular endothelial growth factor because angiogenesis plays a role in the establishment of endometriosis. This study aimed to evaluate the potential of copper-64-labeled bevacizumab, an anti–vascular endothelial growth factor antibody, for endometriosis imaging. Methods: Mouse endometriosis model was prepared by autologous transplantation. The vascular endothelial growth factor expression was evaluated by immunohistochemical staining. Biodistribution study and positron emission tomography imaging were performed at 1, 24, and 48 h after the injection of radiolabeled bevacizumab. Results: The immunohistochemical staining revealed that vascular endothelial growth factor is expressed around the stroma and glandular epithelial cells in the endometriosis lesion. The biodistribution study showed a high uptake of indium-111 bevacizumab in the endometriosis lesion. Positron emission tomography imaging with copper-64-labeled bevacizumab clearly visualized the endometriosis lesions at 24 and 48 h after injection. Conclusion: These results indicate the potential usefulness of copper-64-labeled bevacizumab for endometriosis imaging.

Background We recently reported a new absorbed dose conversion method, RAP (RAtio of Pharmacokinetics), for 211At-meta-astatobenzylguanidine (211At-MABG) using a single biodistribution measurement, the percent injected dose/g. However, there were some mathematical ambiguities in determining the optimal timing of a single measurement of the percent injected dose/g. Thus, we aimed to mathematically reconstruct the RAP method and to examine the optimal timing of a single measurement. Methods We derived a new formalism of the RAP dose conversion method at time t. In addition, we acquired a formula to determine the optimal timing of a single measurement of the percent injected dose/g, assuming the one-compartment model for biological clearance. Results We investigated the new formalism’s performance using a representative RAP coefficient with radioactive decay weighting. Dose conversions by representative RAP coefficients predicted the true [211At]MABG absorbed doses with an error of 10% or less. The inverses of the representative RAP coefficients plotted at 4 h post-injection, which was the optimal timing reported in the previous work, were very close to the new inverses of the RAP coefficients 4 h post-injection. Next, the behavior of the optimal timing was analyzed by radiolabeled compounds with physical half-lives of 7.2 h and 10 d on various biological clearance half-lives. Behavior maps of optimal timing showed a tendency to converge to a constant value as the biological clearance half-life of a target increased. The areas of optimal timing for both compounds within a 5% or 10% prediction error were distributed around the optimal timing when the biological clearance half-life of a target was equal to that of the reference. Finally, an example of RAP dose conversion was demonstrated for [211At]MABG. Conclusions The RAP dose conversion method renovated by the new formalism was able to estimate the [211At]MABG absorbed dose using a similar pharmacokinetics, such as [131I]MIBG. The present formalism revealed optimizing imaging time points on absorbed dose conversion between two radiopharmaceuticals. Further analysis and clinical data will be needed to elucidate the validity of a behavior map of the optimal timing of a single measurement for targeted alpha-nuclide therapy.

Introduction: Urinary fatty acid binding protein 1 (FABP1, also known as liver-type FABP) has been implicated as a biomarker of acute kidney injury (AKI) in humans. However, the precise biological mechanisms underlying its elevation remain elusive. Here, we show that urinary FABP1 primarily reflects impaired protein reabsorption in proximal tubule epithelial cells (PTECs). Methods and Results: Bilateral nephrectomy resulted in a marked increase in serum FABP1 levels, suggesting that the kidney is an essential organ for removing serum FABP1. Injected recombinant FABP1 was filtered through the glomeruli and robustly reabsorbed via the apical membrane of PTECs. Urinary FABP1 was significantly elevated in mice devoid of megalin, a giant endocytic receptor for protein reabsorption. Elevation of urinary FABP1 was also observed in patients with Dent disease, a rare genetic disease characterized by defective megalin function in PTECs. Urinary FABP1 levels were exponentially increased following acetaminophen overdose, with both nephrotoxicity and hepatotoxicity observed. FABP1-deficient mice with liver-specific overexpression of FABP1 showed a massive increase in urinary FABP1 levels upon acetaminophen injection, indicating that urinary FABP1 is liver-derived. Lastly, we employed transgenic mice expressing diphtheria toxin receptor (DT-R) either in a hepatocyte- or PTEC-specific manner, or both. Upon diphtheria toxin (DT) administration, massive excretion of urinary FABP1 was induced in mice with both kidney and liver injury, while mice with either injury type showed marginal excretion. Conclusions: Collectively, our data demonstrated that intact PTECs have a considerable capacity to reabsorb liver-derived FABP1 through a megalin-mediated mechanism. Thus, urinary FABP1, which is synergistically enhanced by concurrent liver injury, is a biomarker for impaired protein reabsorption in AKI. These findings address the use of urinary FABP1 as a biomarker of histologically injured PTECs that secrete FABP1 into primary urine, and suggest the use of this biomarker to simultaneously monitor impaired tubular reabsorption and liver function.

Introduction: The kidney combusts a large amount of fatty acid (FA) for body fluid homeostasis. Despite the high demand for FA, however, little is known about the mechanisms of FA uptake. We aimed to determine how FAs are taken up by tubular epithelial cells. Methods and Results: Immunohistochemistry showed that CD36, known as an important FA transporter in the heart, was also expressed in the basolateral side of proximal tubule epithelial cells (PTECs). The uptake of 125 I-BMIPP, radio-labeled FA tracer, was significantly reduced in the kidney in CD36 knockout mice 1 min after its injection compared with wild-type mice, while the significant difference disappeared 30 min after the injection. In vivo imaging with two-photon microscopy revealed that BODIPY-C 12 , fluorescence-labeled FA tracer, was accumulated in the basolateral side (blood side) of PTECs shortly after its injection, which was followed by accumulation in the apical side (primary urine side), suggesting bidirectional FA uptake by PTECs. A large amount of neutral lipid was accumulated in the kidney when serum FA concentration was increased by accelerated lipolysis by administration of a β3 adrenergic receptor agonist. Immunofluorescence with cell-specific antibodies revealed that the cells with the most abundant lipid accumulation were PTECs, followed by tubular epithelial cells of the distal nephron. In addition, neutral lipid accumulation was enhanced even in the distal nephron when PTECs were injured with administrations of diphtheria toxin (DT) in mice overexpressing DT-receptor in a PTEC-specific manner. Importantly, the PTEC-injured mice exhibited marked albuminuria, suggesting disturbance of protein reabsorption. Despite marked albuminuria, however, urinary FA was not detected at all, suggesting complete FA reabsorption independently of albumin reabsorption in the kidney. Conclusions: Our results revealed the unique and prominent capability of proximal and distal tubular epithelial cells to take up FA from both blood (CD36-dependent) and primary urine (CD36-independent) and to store them as neutral lipids. We further suggest that the kidney acts not only as FA consuming tissue but also as FA keeping tissue to completely reabsorb FA from primary urine for unwasted energy use.

Simple Summary To enhance the therapeutic effect of 2-211At-astato-α-methyl-L-phenylalanine (2-211At-AAMP), a radiopharmaceutical for targeted alpha therapy, we evaluated the effect of probenecid loading on its biodistribution and therapeutic effect in mice. Probenecid preloading significantly delayed the clearance of 2-211At-AAMP from the blood, increasing its accumulation in tumors. Consequently, the therapeutic effect of 2-211At-AAMP markedly improved. These results indicate that 2-211At-AAMP with probenecid loading is useful for the treatment of various types of cancers. Abstract L-type amino acid transporter 1 (LAT1) might be a useful target for tumor therapy since it is highly expressed in various types of cancers. We previously developed an astatine-211 (211At)-labeled amino acid derivative, 2-211At-astato-α-methyl-L-phenylalanine (2-211At-AAMP), and demonstrated its therapeutic potential for LAT1-positive cancers. However, the therapeutic effect of 2-211At-AAMP was insufficient, probably due to its low tumor retention. The preloading of probenecid, an organic anion transporter inhibitor, can delay the clearance of some amino acid tracers from the blood and consequently increase their accumulation in tumors. In this study, we evaluated the effect of probenecid preloading on the biodistribution and therapeutic effect of 2-211At-AAMP in mice. In biodistribution studies, the blood radioactivity of 2-211At-AAMP significantly increased with probenecid preloading. Consequently, the accumulation of 2-211At-AAMP in tumors was significantly higher with probenecid than without probenecid loading. In a therapeutic study, tumor growth was suppressed by 2-211At-AAMP with probenecid, and the tumor volume was significantly lower in the treatment group than in the untreated control group from day 2 to day 30 (end of the follow-up period) after treatment. These results indicate that probenecid loading could improve the therapeutic effect of 2-211At-AAMP by increasing its accumulation in tumors.

3-[Three biodistribution studies of [Probenecid preloading significantly delayed blood clearance and consequently enhanced the accumulation of [Preloading probenecid significantly delayed blood clearance and consequently enhanced the accumulation of [

Backgrounds Overexpression of epidermal growth factor receptor (EGFR) has been established as a valid therapeutic target of non-small cell lung cancer (NSCLC). However, the clinical benefit of cetuximab as an EGFR-targeting drug is still controversial, partially due to the lack of effective means to identify suitable patients. This study aimed to investigate the potential of radiolabeled cetuximab as a non-invasive tool to predict cetuximab accumulation in NSCLC tumor xenografts with varying EGFR expression levels. Methods The NSCLC tumors in model mice were subjected to in vivo biodistribution study and positron emission tomography (PET) imaging 48 h after injection of either 111In- or 64Cu-labeled cetuximab. The EGFR expression levels of NSCLC tumors were determined by ex vivo immunoblotting. Results We found that tumors with high EGFR expression had significantly higher [111In]In-DOTA-cetuximab accumulation than tumors with moderate to low EGFR expression (P 111In]In-DOTA-cetuximab tumor uptake and EGFR expression level (r = 0.893), and between [64Cu]Cu-DOTA-cetuximab tumor uptake with EGFR expression level (r = 0.915). PET imaging with [64Cu]Cu-DOTA-cetuximab allowed clear visualization of tumors. Conclusion Our findings suggest that this immuno-PET imaging can be clinically translated as a tool to predict cetuximab accumulation in NSCLC cancer patients prior to cetuximab therapy.

Early detection plays a role in the prognosis of melanoma, the most aggressive skin cancer. 64Cu- and 68Ga-labeled alpha-melanocyte-stimulating hormone (α-MSH) analogs targeting the melanocortin-1 receptor are promising positron emission tomography (PET) tracers for detecting melanoma, and the use of 18F-labeling will further contribute to the detectability and availability. However, the high radiochemistry demand related to the conventional 18F-labeling methods has restricted the development of 18F-labeled α-MSH analogs. A recently developed radiofluorination method using aluminum-fluoride (Al18F) offers a simple, efficient, and time-saving labeling procedure compared to the conventional 18F-labeling methods. Herein, we sought to establish a simple preparation method for an 18F-labeled α-MSH analog using Al18F, and we examined its potential for the early detection of melanoma. A 1,4,7-triazacyclononane-N,N′,N″-triacetic acid (NOTA)-conjugated α-MSH analog (NOTA-GGNle-CycMSHhex) was prepared by the Fmoc solid-phase strategy. NOTA-GGNle-CycMSHhex was labeled with Al18F by heating at 105 °C using a microwave synthesizer for 15 min. Biodistribution study was conducted on B16/F10-luc melanoma-bearing mice at 30 min, 1 h and 3 h after injection of Al18F-NOTA-GGNle-CycMSHhex. PET imaging was conducted on melanoma-bearing mice at 1 h post-injection. One day prior to the PET imaging, bioluminescence imaging was also performed. Al18F-NOTA-GGNle-CycMSHhex was readily prepared with a high radiochemical yield (94.0 ± 2.8%). The biodistribution study showed a high accumulation of Al18F-NOTA-GGNle-CycMSHhex in the tumor at 30 min and 1 h post-injection (6.69 ± 1.49 and 7.70 ± 1.71%ID/g, respectively). The tumor-to-blood ratio increased with time: 3.46 ± 0.89, 12.67 ± 1.29, and 35.27 ± 9.12 at 30 min, 1 h, and 3 h post-injection, respectively. In the PET imaging, Al18F-NOTA-GGNle-CycMSHhex clearly visualized the tumors and depicted very small tumors (

Positron emission tomography (PET) imaging with 18F-labeled α-methyl-substituted amino acids exerts significant influence on differential diagnosis of malignant tumors and tumor-like lesions. Exclusive uptake via L-type amino acid transporter 1 (LAT1), a tumor-specific transporter, accounts for their excellent tumor specificity and low background accumulation. However, further refinement and optimization in their tumor accumulation and pharmacokinetics are sorely needed. To address these issues, we newly designed 18F-labeled α-methyl-phenylalanine (18F-FAMP) regioisomers (2-, 3-, or 4-18F-FAMP) and stereoisomers (L- or D-form), and we comprehensively evaluated their potential as tumor-imaging agents. 18F-FAMPs were prepared from α-methyl phenylalanine by electrophilic radiofluorination and purified by reversed-phase HPLC. In biodistribution studies on normal mice, L-2-18F-FAMP and the three D-18F-FAMPs showed faster blood clearance and lower renal accumulation than L-3-18F-FAMP or L-4-18F-FAMP. In LS180 human colorectal cancer cell line xenograft mice, L-2-18F-FAMP exhibited significantly higher tumor accumulation than the D-18F-FAMPs or a clinically relevant tracer, L-3-18F-α-methyl-tyrosine (18F-FAMT) (p < 0.05). The renal accumulation levels of L-2-18F-FAMP were significantly lower than that of 18F-FAMT (p < 0.01). LAT-1 specificity of L-2-18F-FAMP was validated in the cellular uptake studies. The PET imaging with L-2-18F-FAMP clearly visualized the tumor as early as 1 h after injection, and the high tumor accumulation level was retained for 3 h. These findings suggest that L-2-18F-FAMP constitutes a potential PET tracer for tumor-specific imaging.

Macrophage mannose receptor (MMR/CD206) is a promising target for the detection and identification of sentinel lymph node (SLN). MMR-targeting probes have been developed using mannosylated dextran, however, impairment of efficient targeting of SLN was often caused because of retention of injection site in which macrophages and dendritic cells exist. In this study, we prepared new MMR-targeting probes from yeast mannan (85 kDa), and its bioditribution was investigated. In-vivo evaluation showed that 11.9% of injected dose of 99mTc-labeled mannan-S-cysteines (99mTc-MSCs) was accumulated in popliteal lymph node (the SLN in this model), however, significant level of radioactivity (approximately 80%) was remained in injection site. Interestingly, 99mTc-labeled low molecular weight mannan-S-cysteine mannan (99mTc-LSC) prepared from 50 and 25 kDa mannan showed a decreased specific accumulation of 99mTc-LSC in the popliteal lymph node, while the radioactivity at the injection site remained unchanged. These results suggest that the molecular size, or nature/shape of the sugar chain is important for the specific accumulation of 99mTc-MSC in popliteal lymph node.

“Radiotheranostics” is a term used in nuclear medicine to refer to the use of radioisotope (RI)-labeled agents to perform simultaneous imaging and therapy of a target lesion. A radiotheranostics system uses radiolanthanides as diagnostic and therapeutic RIs. In this review, we discuss radiotheranostics with radiolanthanides, focusing on the design, development strategies, and medical applications of radiolanthanide-labeled probes. We also discuss the potential and future uses of radiolanthanides in radiotheranostics.

Circulating fatty acid binding protein 4 (FABP4), secreted from adipocytes, is a potential biomarker for metabolic and cardiovascular diseases. Circulating FABP4 levels are positively associated with adiposity and adrenergic stimulation, but negatively with renal function. In this study, we addressed the issue of how the kidney regulates clearance of circulating FABP4. Tracing study revealed remarkable accumulation of 125I-labeled FABP4 in the kidney. Exogenous FABP4 was exclusively detected in the apical membrane of proximal tubule epithelial cells (PTECs). Bilateral nephrectomy resulted in marked elevation of circulating FABP4 levels. Accelerated lipolysis by β-3 adrenergic stimulation led to a marked elevation in circulating FABP4 in mice with severe renal dysfunction. Megalin, an endocytic receptor expressed in PTECs, plays a major role in reabsorption of proteins filtered through glomeruli. Quartz-crystal microbalance study revealed that FABP4 binds to megalin. In kidney-specific megalin knockout mice, a large amount of FABP4 was excreted in urine while circulating FABP4 levels were significantly reduced. Our data suggest that circulating FABP4 is processed by the kidney via the glomerular filtration followed by megalin-mediated reabsorption. Thus, it is likely that circulating FABP4 levels are determined mainly by balance between secretion rate of FABP4 from adipocytes and clearance rate of the kidney.

Photochemical reactions can dramatically alter physical characteristics of reacted molecules. In this study, we demonstrate that near-infrared (NIR) light induces an axial ligand-releasing reaction, which dramatically alters hydrophilicity of a silicon phthalocyanine derivative (IR700) dye leading to a change in the shape of the conjugate and its propensity to aggregate in aqueous solution. This photochemical reaction is proposed as a major mechanism of cell death induced by NIR photoimmunotherapy (NIR-PIT), which was recently developed as a molecularly targeted cancer therapy. Once the antibody-IR700 conjugate is bound to its target, activation by NIR light causes physical changes in the shape of antibody antigen complexes that are thought to induce physical stress within the cellular membrane leading to increases in transmembrane water flow that eventually lead to cell bursting and necrotic cell death., Photoinduced ligand-release reaction of silicon phthalocyanine works as a highly selective “death switch” on targeted cells which antibody-IR700 conjugates bind by inducing damage on cell membrane.

The high and persistent renal radioactivity levels after injection of radiolabeled low-molecular-weight polypeptides constitute a significant problem for their diagnostic and therapeutic applications, especially when they are labeled with metallic radionuclides. To improve the renal radioactivity levels of technetium-99m (

Background Pretargeting radioimmunotherapy (PRIT) is a promising approach that can reduce long-time retention of blood radioactivity and consequently reduce hematotoxicity. Among the PRIT strategies, the combination of biotin-conjugated mAb and radiolabeled streptavidin (StAv) is a simple and convenient method because of ease of preparation. This study performed three-step (3-step) PRIT using the sequential injection of (1) biotinylated bevacizumab (Bt-BV), (2) avidin, and (3) radiolabeled StAv for the treatment of triple-negative breast cancer (TNBC). Methods Four biodistribution studies were performed using 111In in tumor-bearing mice to optimize each step of our PRIT methods. Further, a therapeutic study was performed with optimized 3-step PRIT using 90Y-labeled StAv. Results Based on the biodistribution studies, the protein dose of Bt-BV and avidin was optimized to 100 μg and 10 molar equivalent of BV, respectively. Succinylation of StAv significantly decreased the kidney accumulation level (with succinylation (6.96 ± 0.91) vs without succinylation (20.60 ± 1.47) at 1 h after injection, p < 0.0001) with little effect on tumor accumulation level. In the therapeutic study, tumor growth was significantly suppressed in treatment groups with optimized 3-step PRIT using 90Y-labeled succinylated StAv compared to that of the no-treatment group (p < 0.05). Conclusion The 3-step PRIT strategy of this study achieved fast blood clearance and low kidney uptake with little effect on tumor accumulation level, and a certain level of therapeutic effect was consequently observed. These results indicated that the pretargeting treatment of the current study may be effective for human TNBC treatment.

Diabetes is an independent risk factor for the development of heart failure. Increased fatty acid (FA) uptake and deranged utilization leads to reduced cardiac efficiency and accumulation of cardiotoxic lipids, which is suggested to facilitate diabetic cardiomyopathy. We studied whether reduced FA uptake in the heart is protective against streptozotocin (STZ)-induced diabetic cardiomyopathy by using mice doubly deficient in fatty acid binding protein 4 (FABP4) and FABP5 (DKO mice). Cardiac contractile dysfunction was aggravated 8 weeks after STZ treatment in DKO mice. Although compensatory glucose uptake was not reduced in DKO-STZ hearts, total energy supply, estimated by the pool size in the TCA cycle, was significantly reduced. Tracer analysis with 13C6-glucose revealed that accelerated glycolysis in DKO hearts was strongly suppressed by STZ treatment. Levels of ceramides, cardiotoxic lipids, were similarly elevated by STZ treatment. These findings suggest that a reduction in total energy supply by reduced FA uptake and suppressed glycolysis could account for exacerbated contractile dysfunction in DKO-STZ hearts. Thus, enhanced FA uptake in diabetic hearts seems to be a compensatory response to reduced energy supply from glucose, and therefore, limited FA use could be detrimental to cardiac contractile dysfunction due to energy insufficiency.

Dipeptidyl peptidase-4 (DPP-4) inhibitors are widely used incretin-based therapy for the treatment of type 2 diabetes. We investigated the cardioprotective effect of a DPP-4 inhibitor, vildagliptin (vilda), on myocardial metabolism and cardiac performance under pressure overload. Mice were treated with either vehicle orvilda, followed by transverse aortic constriction (TAC). After 3 weeks of TAC, cardiac hypertrophy and impairment of systolic function were attenuated invilda-treated mice. Pressure–volume analysis showed thatvildatreatment significantly improved left-ventricular contractile efficiency in TAC heart. Myocardial energy substrate analysis showed thatvildatreatment significantly increased glucose uptake as well as fatty acid uptake. Fibroblast growth factor 21 (FGF21), a peptide involved in the regulation of energy metabolism, increased in TAC heart and was further increased byvildatreatment. FGF21 was strongly expressed in cardiac fibroblasts than in cardiomyocytes in mouse heart after TAC withvildatreatment.Vildatreatment markedly induced FGF21 expression in human cardiac fibroblasts through a sirtuin (Sirt) 1-mediated pathway, suggesting that fibroblast-mediated FGF21 expression may regulate energy metabolism and exertvilda-mediated beneficial effects in stressed heart.Vildainduced a metabolic regulator, FGF21 expression in cardiac fibroblasts via Sirt1, and increased contractile efficiency in murine pressure-overloaded heart.

Introduction Targeted α-radionuclide therapy has attracted attention as a promising therapy for refractory cancers. However, the application is limited to certain types of cancer. Since L-type amino acid transporter 1 (LAT1) is highly expressed in various human cancers, we prepared an LAT1-selective α-radionuclide-labeled amino acid analog, 2-[211At]astato-α-methyl-L-phenylalanine (2-[211At]AAMP), and evaluated its potential as a therapeutic agent. Methods 2-[211At]AAMP was prepared from the stannyl precursor. Stability of 2-[211At]AAMP was evaluated both in vitro and in vivo. In vitro studies using an LAT1-expressing human ovarian cancer cell line, SKOV3, were performed to evaluate cellular uptake and cytotoxicity of 2-[211At]AAMP. Biodistribution and therapeutic studies in SKOV3-bearing mice were performed after intravenous injection of 2-[211At]AAMP. Results 2-[211At]AAMP was stable in murine plasma in vitro and excreted intact into urine. Cellular uptake of 2-[211At]AAMP was inhibited by treatment with an LAT1-selective inhibitor. After 24 h incubation, 2-[211At]AAMP suppressed clonogenic growth at 10 kBq/ml, and induced cell death and DNA double-strand breaks at 25 kBq/ml. When injected into mice, 2-[211At]AAMP exhibited peak accumulation in the tumor at 30 min postinjection, and radioactivity levels in the tumor were retained up to 60 min. The majority of the radioactivity was rapidly eliminated from the body into urine in an intact form immediately after injection. 2-[211At]AAMP significantly improved the survival of mice (P Conclusion 2-[211At]AAMP showed α-radiation-dependent cellular growth inhibition after it was taken up via LAT1. In addition, 2-[211At]AAMP had a beneficial effect on survival in vivo. These findings suggest that 2-[211At]AAMP would be useful for the treatment of LAT1-positive cancer. Advances in knowledge and implications for patient care This is the first report of an LAT1-targeting radiopharmaceutical for α-radionuclide therapy; this agent would be applicable for the treatment of various types of cancer.

We aimed to estimate in vivoWe used the framework of the Monte Carlo method to create 3200 virtual experimental data sets of activity concentrations (kBq/g) to get the statistical information. Time activity concentration curves were produced using the fitting method of a genetic algorithm. The basic method was that absorbed doses ofVirtual experiments showed thatThe present RAP dose conversion method could estimate

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Although 2-We used the human bladder cancer cell line HT1376 to prepare a bladder cancer xenograft model in mice bearing both orthotopic and subcutaneous tumors. Biodistribution and PET imaging studies were performed at 1 and 3 h after injection of L-2-At 1 h after injection, greater accumulations of both L-2-Our study showed that L-2

Purpose: This study was undertaken to evaluate the renal radioactivity levels of a newly designed 67Ga-labeled antibody fragment with a linkage cleaved by enzymes present on the brush border membrane (BBM) lining the lumen of the renal tubule. Experimental Design: 67Ga-labeled S-2-(4-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (SCN-Bn-NOTA) was conjugated with an antibody Fab fragment through a Met-Val-Lys linkage (67Ga-NOTA-MVK-Fab) considering that a Met-Val sequence is a substrate of enzymes on the renal BBM and 67Ga-NOTA-Met is excreted from the kidney into the urine. The enzymatic recognition of the linkage was evaluated with a low-molecular-weight 67Ga-NOTA-Met-Val-Lys derivative. Biodistribution of radioactivity after injection of 67Ga-NOTA-MVK-Fab into mice was compared with 67Ga-NOTA-conjugated Fab fragments through a Met-Ile linkage that liberates 67Ga-NOTA-Met (67Ga-NOTA-MI-Fab) or a conventional thiourea linkage (67Ga-NOTA-Fab). Results: The MVK linkage remained stable in plasma and was recognized by enzymes on renal BBM to liberate 67Ga-NOTA-Met. When injected into mice, all three 67Ga-labeled Fab exhibited similar blood clearance rates and tumor accumulation. Significant differences were observed in the kidney where 67Ga-NOTA-MVK-Fab registered the lowest renal radioactivity levels from early postinjection time (P < 0.05), followed by 67Ga-NOTA-MI-Fab, which was well reflected in the SPECT/CT images. Conclusions: These findings indicated that our proposal of liberating a radiolabeled compound to urinary excretion from antibody fragments at the renal BBM to reduce the renal radioactivity levels was applicable to 67/68Ga-labeled antibody fragments. Because antibody fragments and constructs share similar metabolic fates in the kidney, the present labeling procedure would also apply to a variety of antibody fragments and constructs of interest. Clin Cancer Res; 24(14); 3309–16. ©2018 AACR.

In the synthesis of technetium-99m (99mTc) labeled target-specific ligands, the presence of a large excess of unlabeled ligands over 99mTc in the injectate hinders target accumulation of 99mTc-labeled ligands by competing for target molecules. To circumvent the problem, we recently developed a concept of the metal coordination-mediated multivalency, and proved the concept with a 99mTc-labeled trivalent compound [99mTc(CO)3(CN-RGD)3]+ In this study, D-penicillamine (Pen) was selected as a chelating molecule and a cyclic RGDfK peptide was conjugated to Pen via a hexanoic linkage (Pen-Ahx-c(RGDfK)). 99mTc complexation reaction, and the stability, integrin αvβ3 binding affinity and biodistribution of the 99mTc-labeled probe was investigated to evaluate the applicability of the concept to bivalent probes. 99mTc-[Pen-Ahx-c(RGDfK)2] was obtained over 95% radiochemical yields under low Pen-Ahx-c(RGDfK) concentration (50 µM). 99mTc-[Pen-Ahx-c(RGDfK)2] showed approximately 10-times higher integrin αvβ3 binding affi...