Positron emission tomography imaging of tumors expressing the human chemokine receptor CXCR4 in mice with the use of 64Cu-AMD3100

PURPOSE

Expression of CXCR4 in cancers has been correlated with poor prognosis and increased metastasis. Quantifying CXCR4 expression non-invasively might aid in prognostication and monitoring therapy. We evaluated a radiolabeled antagonist of CXCR4, ⁶⁴Cu-AMD3100, as a positron-emitting imaging agent.

PROCEDURES

CXCR4-transfected or non-transfected cell lines were injected into mice to form xenografts. Accumulation of ⁶⁴Cu-AMD3100 in tumors was analyzed by small-animal PET and biodistribution assays.

RESULTS

⁶⁴Cu-AMD3100 accumulated in CXCR4-expressing, but not CXCR4-negative, tumors. For CXCR4-expressing tumors, tumor-to-blood and tumor-to-muscle ratios were 23-41 and 50-59, respectively, depending on tumor type. Excess of unlabeled Cu-AMD3100 or AMD3100 significantly reduced ⁶⁴Cu-AMD3100 accumulation in CXCR4-expressing tumors. Human-absorbed dose calculations predicted a dose limit of 444 MBq.

CONCLUSIONS

CXCR4 can be imaged in tumors using ⁶⁴Cu-AMD3100. Dosimetry studies suggest that imaging in humans is feasible. We conclude that ⁶⁴Cu-AMD3100 should be investigated as a potential agent for imaging and quantifying CXCR4 in tumors.

Altered gastric emptying and prevention of radiation-induced vomiting in dogs

The relation between radiation-induced vomiting and gastric emptying is unclear and the treatment of this condition is not established. We explored, therefore, (a) the effect of cobalt 60 irradiation on gastric emptying of solids and liquids and (b) the possibility of preventing radiation-induced vomiting with the dopamine antagonist, domperidone. Twenty dogs were studied on two separate days, blindly and in random order, after i.v. injection of either a placebo or 0.06 mg/kg domperidone. On a third day, they received 8 Gy (800 rads) whole body irradiation with cobalt 60 gamma-rays after either placebo (n = 10) or domperidone (n = 10). Before each study, each dog was fed chicken liver tagged in vivo with 99mTc-sulfur colloid (solid marker), and water containing 111In-diethylenetriamine pentaacetic acid (liquid marker). Dogs were placed in a Pavlov stand for the subsequent 3 h and radionuclide imaging was performed at 10-min intervals. Irradiation produced vomiting in 9 of 10 dogs given placebo but only in 1 of 10 dogs pretreated with domperidone (p less than 0.01). Gastric emptying of liquids and solids was significantly suppressed by irradiation (p less than 0.01) after both placebo and domperidone. These results demonstrate that radiation-induced vomiting is accompanied by suppression of gastric emptying. Furthermore, domperidone prevents vomiting produced by ionizing radiation but does not alter the accompanying delay of gastric emptying.

Regional pulmonary function after irradiation of the canine lung: radionuclide evaluation

The pulmonary effects of neutron and gamma irradiation were compared in a group of beagle dogs that were subjected to hemithorax irradiation with cobalt-60 gamma rays or 15-MeV neutrons. Integral cobalt-60 doses of 3000, 4500, or 6750 rad (30, 45, or 67.5 Gy) and neutron doses of 1000, 1500, or 2250 rad (10, 15, or 22.5 Gy) were given on a therapy-type schedule of four equal fractions per week for 6 weeks. Serial Tc-99m-macroaggregated albumin perfusion, Tc-99m-Sn-phytate aerosol, and xenon-133 ventilation studies were performed before irradiation and at 3, 6, 9, 12, 18, and 24 months postexposure. Pulmonary damage was more severe and persistent with neutron than with gamma radiation, but the changes were dose-dependent for both types of radiation. The perfusion and radioaerosol imaging studies provided the best scintigraphic evidence of lung damage. Abnormalities in the xenon-133 studies were relatively minor and were more apparent on the single-breath than on the equilibrium or clearance studies. The scintigraphic studies provided evidence of radiation-induced ventilation perfusion inequalities with both types of radiation, but required several times less neutron radiation than gamma radiation to produce similar alterations in ventilation-perfusion relationships.