Biodistribution of ⁶⁴Cu-ATSM in BALB/c nude mice.

<p>Data were obtained at 5⁶⁴Cu-ATSM injection. Values are expressed as the %ID/g for the organs (liver, kidney, small intestine, large intestine, muscle, and remainder of the body) and blood and as the %ID for the urine and feces. Values are shown as means ± SD; <i>n</i> = 4 for 5 min, 15 min, 30 min, 1 h, 2 h, 4 h, and 6 h and <i>n</i> = 3 for 16 h and 24 h.</p

Mean estimated human absorbed doses for ⁶⁴Cu-ATSM, extrapolated from mouse biodistribution data.

<p>Mean estimated human absorbed doses for ⁶⁴Cu-ATSM, extrapolated from mouse biodistribution data.</p

Chronological changes in biodistribution and excretion after ⁶⁴Cu-ATSM injection with fractionated penicillamine injections.

<p>Biodistribution in organs and urinary and fecal excretions at 2, 4, 6, 16, and 24⁶⁴Cu-ATSM injection in HT-29 tumor-bearing mice that were treated p.o. with fractionated doses of penicillamine (100 mg/kg×3) at 1, 2, and 3 h or 1, 3, and 5 h after ⁶⁴Cu-ATSM injection, compared with those in animals treated with saline (control). Additional laxative treatments at 5.5 h after ⁶⁴Cu-ATSM injection along with penicillamine administration (100 mg/kg×3; 1, 3, and 5 h after ⁶⁴Cu-ATSM injection) are also shown. Data are shown as the %ID/g for the organs (liver, kidney, small intestine, large intestine, muscle, remainder of the body, and tumor) and blood and the %ID for the urine and feces at 2, 4, 6, 16, and 24 h after ⁶⁴Cu-ATSM injection. Asterisks indicate statistical significance (*<i>P</i><0.05) in comparison to the control at each time point. There were no significant differences in the %ID/g of the tumors between any of the treatment groups and the control. Values are shown as means ± SD; <i>n</i> = 4 for 2, 4, and 6 h and <i>n</i> = 3 for 16 and 24 h.</p

Controlled Administration of Penicillamine Reduces Radiation Exposure in Critical Organs during ⁶⁴Cu-ATSM Internal Radiotherapy: A Novel Strategy for Liver Protection

<div><p>Purpose</p><p>⁶⁴Cu-diacetyl-bis (<i>N</i>⁴-methylthiosemicarbazone) (⁶⁴Cu-ATSM) is a promising theranostic agent that targets hypoxic regions in tumors related to malignant characteristics. Its diagnostic usefulness has been recognized in clinical studies. Internal radiotherapy (IRT) with ⁶⁴Cu-ATSM is reportedly effective in preclinical studies; however, for clinical applications, improvements to reduce radiation exposure in non-target organs, particularly the liver, are required. We developed a strategy to reduce radiation doses to critical organs while preserving tumor radiation doses by controlled administration of copper chelator penicillamine during ⁶⁴Cu-ATSM IRT.</p><p>Methods</p><p>Biodistribution was evaluated in HT-29 tumor-bearing mice injected with ⁶⁴Cu-ATSM (185 kBq) with or without oral penicillamine administration. The appropriate injection interval between ⁶⁴Cu-ATSM and penicillamine was determined. Then, the optimal penicillamine administration schedule was selected from single (100, 300, and 500 mg/kg) and fractionated doses (100 mg/kg×3 at 1- or 2-h intervals from 1 h after ⁶⁴Cu-ATSM injection). PET imaging was performed to confirm the effect of penicillamine with a therapeutic ⁶⁴Cu-ATSM dose (37 MBq). Dosimetry analysis was performed to estimate human absorbed doses.</p><p>Results</p><p>Penicillamine reduced ⁶⁴Cu accumulation in the liver and small intestine. Tumor uptake was not affected by penicillamine administration at 1 h after ⁶⁴Cu-ATSM injection, when radioactivity was almost cleared from the blood and tumor uptake had plateaued. Of the single doses, 300 mg/kg was most effective. Fractionated administration at 2-h intervals further decreased liver accumulation at later time points. PET indicated that penicillamine acts similarly with the therapeutic ⁶⁴Cu-ATSM dose. Dosimetry demonstrated that appropriately scheduled penicillamine administration reduced radiation doses to critical organs (liver, ovaries, and red marrow) below tolerance levels. Laxatives reduced radiation doses to the large intestine.</p><p>Conclusions</p><p>We developed a novel strategy to reduce radiation exposure in critical organs during ⁶⁴Cu-ATSM IRT, thus promoting its clinical applications. This method could be beneficial for other ⁶⁴Cu-labeled compounds.</p></div

Representative PET images.

<p>PET images of HT-29 tumor-bearing mice that were administered ⁶⁴Cu-ATSM and a single dose of penicillamine (300 mg/kg p.o.) or saline (control) at 1 h after the ⁶⁴Cu-ATSM injection are shown. (A) Coronal PET images show the liver (white arrows). (B) Transverse PET images show the tumor. HT29 tumors are indicated by yellow arrows and circles. Images were obtained at 0.5, 2, and 3 h after the ⁶⁴Cu-ATSM injection. (C) Time activity curves from the PET analysis. Time activity curves for the liver (upper) and tumor (lower) are shown for animals treated with penicillamine or saline (control; <i>n = </i>3/group). Values are shown as means ± SD.</p

Chronological changes in biodistribution and excretion after ⁶⁴Cu-ATSM injection with single-dose penicillamine injections.

<p>Biodistribution in the organs and urinary and fecal excretions at 2, 4, 6, 16, and 24⁶⁴Cu-ATSM injection in HT-29 tumor-bearing mice that were treated p.o. with a single-dose of 100, 300, or 500 mg/kg penicillamine at 1 h after ⁶⁴Cu-ATSM injection, compared with those in animals treated with saline (control). Data are shown as the %ID/g for the organs (liver, kidney, small intestine, large intestine, muscle, remainder of the body, and tumor) and blood and the %ID for the urine and feces. Asterisks indicate statistical significance (*<i>P</i><0.05) in comparison to the control at each time point. There were no significant differences in the %ID/g of the tumors between any of the treatment groups and the control. Values are shown as means ± SD; <i>n</i> = 4 for 2, 4, and 6 h and <i>n</i> = 3 for 16 and 24 h.</p

The effect of penicillamine administration timing on the biodistribution of ⁶⁴Cu-ATSM.

<p>(A) Biodistribution in the liver (upper) and tumor (lower) in HT-29 tumor-bearing mice that were treated p.o. with a single-dose of 500 mg/kg penicillamine at 10 min before or after ⁶⁴Cu-ATSM injection or at 1 h after ⁶⁴Cu-ATSM injection. Data were obtained at 1, 2, and 4 h after ⁶⁴Cu-ATSM injection. (B) Time activity curves for the tumors and blood, based on the biodistribution data from HT-29 tumor-bearing mice (control animal). Values are shown as means ± SD; <i>n</i> = 4 for each time point.</p

Biodistribution of [1-¹⁴C]acetate and <i>in vivo</i> PET imaging with [1-¹¹C]acetate in tumor xenograft-bearing mice.

<p>(A) Biodistribution at 10 min and 30 min in organs (left) and each tumor (right). Data represents %ID/g, expressed as means ± SD. The groups with different alphabets are significantly different (<i>P</i><0.05). (B) Small-animal PET images of [1-¹¹C]acetate at 30 min after injection. Yellow arrows indicate tumors. S = stomach; L = liver.</p

Effects of FASN inhibition by RNAi in FASN-expressing LNCaP cells.

<p>FASN-RNAi 3128 and 3129 cells and control-RNAi cells were used. (A) Relative expression of FASN, analyzed by Western blotting analysis (left) and uptake of [1-¹⁴C]acetate (right). (B) Cell proliferation over 7 days (upper, left). Light microscopy images (upper, right). Relative migration and invasion potential in FASN-RNAi cells, as compared with control-RNAi cells (lower, left and right, respectively). Values from six independent experiments are shown. Data are expressed as means ± SD. The groups with different alphabets are significantly different (<i>P</i><0.05).</p

Schematic view of this study.

<p>The functions of FASN in tumors, mechanism of FASN inhibition, and method for applying [1-¹¹C]acetate PET as a predictor of outcome of FASN-targeted therapies are shown.</p