Potential Application of the Myocardial Scintigraphy Agent [123I]BMIPP in Colon Cancer Cell Imaging.

[123I]ß-methyl-p-iodophenyl-pentadecanoic acid ([123I]BMIPP), which is used for nuclear medicine imaging of myocardial fatty acid metabolism, accumulates in cancer cells. However, the mechanism of accumulation remains unknown. Therefore, this study aimed to elucidate the accumulation and accumulation mechanism of [123I]BMIPP in cancer cells. We compared the accumulation of [123I]BMIPP in cancer cells with that of [18F]FDG and found that [123I]BMIPP was a much higher accumulation than [18F]FDG. The accumulation of [123I]BMIPP was evaluated in the presence of sulfosuccinimidyl oleate (SSO), a CD36 inhibitor, and lipofermata, a fatty acid transport protein (FATP) inhibitor, under low-temperature conditions and in the presence of etomoxir, a carnitine palmitoyl transferase I (CPT1) inhibitor. The results showed that [123I]BMIPP accumulation was decreased in the presence of SSO and lipofermata in H441, LS180, and DLD-1 cells, suggesting that FATPs and CD36 are involved in [123I]BMIPP uptake in cancer cells. [123I]BMIPP accumulation in all cancer cell lines was significantly decreased at 4 °C compared to that at 37 °C and increased in the presence of etomoxir in all cancer cell lines, suggesting that the accumulation of [123I]BMIPP in cancer cells is metabolically dependent. In a biological distribution study conducted using tumor-bearing mice transplanted with LS180 cells, [123I]BMIPP highly accumulated in not only LS180 cells but also normal tissues and organs (including blood and muscle). The tumor-to-intestine or large intestine ratios of [123I]BMIPP were similar to those of [18F]FDG, and the tumor-to-large-intestine ratios exceeded 1.0 during 30 min after [123I]BMIPP administration in the in vivo study. [123I]BMIPP is taken up by cancer cells via CD36 and FATP and incorporated into mitochondria via CPT1. Therefore, [123I]BMIPP may be useful for imaging cancers with activated fatty acid metabolism, such as colon cancer. However, the development of novel imaging radiotracers based on the chemical structure analog of [123I]BMIPP is needed.

Estimation of post-therapeutic liver reserve capacity using 99mTc-GSA scintigraphy prior to carbon-ion radiotherapy for liver tumors.

BACKGROUND: There is currently no established imaging method for assessing liver reserve capacity prior to carbon-ion radiotherapy (CIRT) for liver tumors. In order to perform safe CIRT, it is essential to estimate the post-therapeutic residual reserve capacity of the liver. PURPOSE: To evaluate the ability of pre-treatment 99mTc-galactosyl human serum albumin (99mTc-GSA) scintigraphy to accurately estimate the residual liver reserve capacity in patients treated with CIRT for liver tumors. MATERIALS AND METHODS: This retrospective study evaluated patients who were performed CIRT for liver tumors between December 2018 and September 2020 and underwent 99mTc-GSA scintigraphy before and 3 months after CIRT, and gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced MRI within 1 month before CIRT were evaluated. The maximal removal rate of 99mTc-GSA (GSA-Rmax) was analyzed for the evaluation of pre-treatment liver reserve capacity. Then, the GSA-Rmax of the estimated residual liver (GSA-RL) was calculated using liver SPECT images fused with the Gd-EOB-DTPA-enhanced MRI. GSA-RL before CIRT and GSA-Rmax at 3 months after CIRT were compared using non-parametric Wilcoxon signed-rank test and linear regression analysis. RESULTS: Overall, 50 patients were included (mean age ± standard deviation, 73 years ± 11; range, 29-89 years, 35 men). The median GSA-RL was 0.393 [range, 0.057-0.729] mg/min, and the median GSA-Rmax after CIRT was 0.369 [range, 0.037-0.780] mg/min (P = .40). The linear regression equation representing the relationship between the GSA-RL and GSA-Rmax after CIRT was y = 0.05 + 0.84x (R2 = 0.67, P < .0001). There was a linear relationship between the estimated and actual post-treatment values for all patients, as well as in the group with impaired liver reserve capacity (y = - 0.02 + 1.09x (R2 = 0.62, P = .0005)). CONCLUSIONS: 99mTc-GSA scintigraphy has potential clinical utility for estimating the residual liver reserve capacity in patients undergoing carbon-ion radiotherapy for liver tumors. TRIAL REGISTRATION: UMIN000038328, https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000043545 .

Evaluation of L-Alanine Metabolism in Bacteria and Whole-Body Distribution with Bacterial Infection Model Mice.

The World Health Organization has cautioned that antimicrobial resistance (AMR) will be responsible for an estimated 10 million deaths annually by 2050. To facilitate prompt and accurate diagnosis and treatment of infectious disease, we investigated the potential of amino acids for use as indicators of bacterial growth activity by clarifying which amino acids are taken up by bacteria during the various growth phases. In addition, we examined the amino acid transport mechanisms that are employed by bacteria based on the accumulation of labeled amino acids, Na+ dependence, and inhibitory effects using a specific inhibitor of system A. We found that 3H-L-Ala accurately reflects the proliferative activity of Escherichia coli K-12 and pathogenic EC-14 in vitro. This accumulation in E. coli could be attributed to the amino acid transport systems being different from those found in human tumor cells. Moreover, biological distribution assessed in infection model mice with EC-14 using 3H-L-Ala showed that the ratio of 3H-L-Ala accumulated in infected muscle to that in control muscle was 1.20. By detecting the growth activity of bacteria in the body that occurs during the early stages of infection by nuclear imaging, such detection methods may result in expeditious diagnostic treatments for infectious diseases.

Comparison of L- and D-Amino Acids for Bacterial Imaging in Lung Infection Mouse Model.

The effectiveness of L- and D-amino acids for detecting the early stage of infection in bacterial imaging was compared. We evaluated the accumulation of 3H-L-methionine (Met), 3H-D-Met, 3H-L-alanine (Ala), and 3H-D-Ala in E. coli EC-14 and HaCaT cells. Biological distribution was assessed in control and lung-infection-model mice with EC-14 using 3H-L- and D-Met, and 18F-FDG. A maximum accumulation of 3H-L- and D-Met, and 3H-L- and D-Ala occurred in the growth phase of EC-14 in vitro. The accumulation of 3H-L-Met and L-Ala was greater than that of 3H-D-Met and D-Ala in both EC-14 and HaCaT cells. For all radiotracers, the accumulation was greater in EC-14 than in HaCaT cells at early time points. The accumulation was identified at 5 min after injection in EC-14, whereas the accumulation gradually increased in HaCaT cells over time. There was little difference in biodistribution between 3H-L-and D-Met except in the brain. 3H-L- and D-Met were sensitive for detecting areas of infection after the spread of bacteria throughout the body, whereas 18F-FDG mainly detected primary infection areas. Therefore, 11C-L- and D-Met, radioisotopes that differ only in terms of 3H labeling, could be superior to 18F-FDG for detecting bacterial infection in lung-infection-model mice.

Unique advantages of dynamic l-[11C]methionine PET/CT for assessing the rate of skeletal muscle protein synthesis: A pilot trial in young men.

Although the standard method to evaluate skeletal muscle protein synthesis (MPS) is muscle biopsy, the method is invasive and problematic for multisite use. We conducted a small pilot study in volunteers to investigate changes in MPS according to skeletal muscle site using a noninvasive method in which 6 healthy young men were given yogurt (containing 20 g milk protein) or water, and 1 h later, l-[11C]methionine ([11C]Met) was administered intravenously. Dynamic PET/CT imaging of their thighs was performed for 60 min. The influx constant Ki of [11C]Met in skeletal muscle protein was calculated as an index of MPS using a Patlak plot, and found to be 0.6%-28% higher after ingesting yogurt than after water in 5 of the 6 volunteer participants, but it was 34% lower in the remaining participant. Overall, this indicated no significant increase in Ki after ingesting milk protein. However, when the quadriceps and hamstring muscles were analyzed separately, we found a significant difference in Ki. This demonstrates the potential of visualizing MPS by calculating the Ki for each voxel and reconstructing it as an image, which presents unique advantages of [11C]Met PET/CT for evaluating MPS, such as site-specificity and visualization.

A first-in-man study of [18F] FEDAC: a novel PET tracer for the 18-kDa translocator protein.

PURPOSE: N-benzyl-N-methyl-2-[7, 8-dihydro-7-(2-[18F] fluoroethyl) -8-oxo-2-phenyl-9H-purin-9-yl] acetamide ([18F] FEDAC) is a novel positron emission tomography (PET) tracer that targets the translocator protein (TSPO; 18 kDa) in the mitochondrial outer membrane, which is known to be upregulated in various diseases such as malignant tumors, neurodegenerative diseases, and neuroinflammation. This study presents the first attempt to use [18F]FEDAC PET/CT and evaluate its biodistribution as well as the systemic radiation exposure to the radiotracer in humans. MATERIALS AND METHODS: Seventeen whole-body [18F]FEDAC PET/CT (injected dose, 209.1 ± 6.2 MBq) scans with a dynamic scan of the upper abdomen were performed in seven participants. Volumes of interest were assigned to each organ, and a time-activity curve was created to evaluate the biodistribution of the radiotracer. The effective dose was calculated using IDAC-Dose 2.1. RESULTS: Immediately after the intravenous injection, the radiotracer accumulated significantly in the liver and was subsequently excreted into the gastrointestinal tract through the biliary tract. It also showed high levels of accumulation in the kidneys, but showed minimal migration to the urinary bladder. Thus, the liver was the principal organ that eliminated [18F] FEDAC. Accumulation in the normal brain tissue was minimal. The effective dose estimated from biodistribution in humans was 19.47 ± 1.08 µSv/MBq, and was 3.60 mSV for 185 MBq dose. CONCLUSION: [18F]FEDAC PET/CT provided adequate image quality at an acceptable effective dose with no adverse effects. Therefore, [18F]FEDAC may be useful in human TSPO-PET imaging.

Biological Distribution after Oral Administration of Radioiodine-Labeled Acetaminophen to Estimate Gastrointestinal Absorption Function via OATPs, OATs, and/or MRPs.

We evaluated the whole-body distribution of orally-administered radioiodine-125 labeled acetaminophen (125I-AP) to estimate gastrointestinal absorption of anionic drugs. 125I-AP was added to human embryonic kidney (HEK)293 and Flp293 cells expressing human organic anion transporting polypeptide (OATP)1B1/3, OATP2B1, organic anion transporter (OAT)1/2/3, or carnitine/organic cation transporter (OCTN)2, with and without bromosulfalein (OATP and multidrug resistance-associated protein (MRP) inhibitor) and probenecid (OAT and MRP inhibitor). The biological distribution in mice was determined by oral administration of 125I-AP with and without bromosulfalein and by intravenous administration of 125I-AP. The uptake of 125I-AP was significantly higher in HEK293/OATP1B1, OATP1B3, OATP2B1, OAT1, and OAT2 cells than that in mock cells. Bromosulfalein and probenecid inhibited OATP- and OAT-mediated uptake, respectively. Moreover, 125I-AP was easily excreted in the urine when administered intravenously. The accumulation of 125I-AP was significantly lower in the blood and urinary bladder of mice receiving oral administration of both 125I-AP and bromosulfalein than those receiving only 125I-AP, but significantly higher in the small intestine due to inhibition of OATPs and/or MRPs. This study indicates that whole-body distribution after oral 125I-AP administration can be used to estimate gastrointestinal absorption in the small intestine via OATPs, OATs, and/or MRPs by measuring radioactivity in the urinary bladder.

123I-BMIPP, a Radiopharmaceutical for Myocardial Fatty Acid Metabolism Scintigraphy, Could Be Utilized in Bacterial Infection Imaging.

In this study, we evaluated the use of 15-(4-123I-iodophenyl)-3(R,S)-methylpentadecanoic acid (123I-BMIPP) to visualize fatty acid metabolism in bacteria for bacterial infection imaging. We found that 123I-BMIPP, which is used for fatty acid metabolism scintigraphy in Japan, accumulated markedly in Escherichia coli EC-14 similar to 18F-FDG, which has previously been studied for bacterial imaging. To elucidate the underlying mechanism, we evaluated changes in 123I-BMIPP accumulation under low-temperature conditions and in the presence of a CD36 inhibitor. The uptake of 123I-BMIPP by EC-14 was mediated via the CD36-like fatty-acid-transporting membrane protein and accumulated by fatty acid metabolism. In model mice infected with EC-14, the biological distribution and whole-body imaging were assessed using 123I-BMIPP and 18F-FDG. The 123I-BMIPP biodistribution study showed that, 8 h after infection, the ratio of 123I-BMIPP accumulated in infected muscle to that in control muscle was 1.31 at 60 min after 123I-BMIPP injection. In whole-body imaging 1.5 h after 123I-BMIPP administration and 9.5 h after infection, infected muscle exhibited a 1.33-times higher contrast than non-infected muscle. Thus, 123I-BMIPP shows potential for visualizing fatty acid metabolism of bacteria for imaging bacterial infections.

A single high-dose irradiation changes accumulation of methotrexate and gene expression levels of SLC and ABC transporters in cancer cells.

Chemoradiotherapy is frequently used to treat cancer. Stereotactic body radiotherapy (SBRT) is a single high-dose radiotherapy used to treat a variety of cancers. The anticancer drug methotrexate (MTX) shows affinity for solute carrier (SLC) and ATP-binding cassette (ABC) transporters. This study investigated relationships between accumulation of methotrexate and gene expression levels of solute carrier and ATP-binding cassette transporters in cancer cells after a single and high-dose X-ray irradiation. Cancer cell lines were selected from lung and cervical cancer cell line that are commonly used for stereotactic body radiotherapy and effective with methotrexate. We examined expression levels of organic anion-transporting polypeptide (OATP)1B1, OATP1B3, OATP1B7, and organic anion transporter (OAT)1 as solute carrier transporters and multidrug resistance-associated protein (MRP)1 and MRP2 as ATP-binding cassette transporters, using real-time polymerase chain reaction and accumulation of 3H-MTX in cancer cells after 10-Gy irradiation, assuming stereotactic body radiotherapy. Cells were divided into three groups: Control without irradiation; 4 h after irradiation; and 24 h after irradiation. In control, gene expression levels of OAT1 in all cells was below the limit of measurement. After irradiation, gene expression levels of OATP1B1/1B3/1B7 showed changes in each cell line. Gene expression levels of MRP1/2 tended to increase after irradiation. Gene expression levels of OATP1B1/1B3/1B7 were much lower than those of MRP1/2. Accumulation of 3H-MTX tended to decrease over time after irradiation. Irradiation of cancer cells thus alters gene expression levels of both solute carrier transporters (OATP1B1/1B3/1B7) and ABC transporters (MRP1/2) and decreases accumulation of 3H-MTX in cancer cells over time due to elevated expression of MRP1/2.

[S-methyl-11C]-L-methionine positron emission tomography/computed tomography imaging parameters to evaluate early response for esophageal cancer with neoadjuvant carbon ion radiotherapy.

This study aimed to evaluate the uptake of the clinical effectiveness of [S-methyl-11C]-L-methionine positron emission tomography/computed tomography (MET PET/CT) in patients with esophageal cancer and to investigate MET PET/CT imaging parameters to assess early response for esophageal cancer with neoadjuvant carbon ion radiotherapy (CIRT). MET PET/CT scans were performed in nineteen patients before and 3 weeks after completion of CIRT. After Surgery, the effect of neoadjuvant CIRT was investigated by examining the relationship between each parameter of MET uptake and the histological assessment (grade and tumor residual ratio). Four parameters of MET uptake were the maximum and minimum standardized uptake values of pre and post CIRT (pre-SUVmax, pre-SUVmean, post-SUVmax, and post-SUVmean). MET PET/CT imaging of esophageal cancer was clearly demonstrated. The post-SUVmax was the most suitable parameter. When the cutoff value was set as post-SUVmax = 6.21, the sensitivity, the specificity, and the accuracy of Grades 3 were 100.0%, 63.6%, and 78.9%, respectively. And there was a positive relationship between the tumor residual ratio and post-SUVmax (R2 = 0.38, p < 0.005). MET PET/CT is clinically useful for the assessment of early response to neoadjuvant CIRT in esophageal cancer. Particularly, post-SUVmax is considered a promising PET imaging parameter.