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PET 68Ga-labeled alphamethyl tyrosine for imaging lung and breast tumors in rodents

¹ Exp Diag Imaging, UTMD Anderson Cancer Ctr, Houston, Texas

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Objectives: This study was aimed to synthesize 68Ga-1, 4, 8, 11-tetraazacyclotetradecane--methyl-D, L-tyrosine (68Ga-N4-AMT) as apotential radiotracer for imaging lung and breast tumors.

Methods: The phenolic hydroxy group of N-t-butoxycarbonyl (BOC) AMT ethyl ester was reacted with bromopropanol, followed by tosylation to afford N-BOC-O-3-tosylpropyl-AMT ethyl ester. N4-AMT was synthesized by reacting trifloroacetylated cyclam and N-BOC -O-3-tosylpropyl-AMT, followed by acidic hydrolysis to remove protected N-BOC, trifluoroacetate and ethyl ester. 68GaCL3 was eluted from a 68Ge/68Ga generator (Eckert & Ziegler, Berlin, Germany). N4-AMT (1 mg) was labeled with 68Ga(III) using acetate buffer (pH 5). The lung and breast tumor-bearing models were created by inoculating with NCI-H187 lung tumor cells (106 cells/mouse) and rat 13762 breast tumor cells (105 cells/rat) sc in the right hond limbs of nude mice or F-344 rats, respectively. The rodents were administered with 68Ga-N4, 68Ga-N4-AMT and 18F-FDG (300-500 uCi/rodent, iv). PET imaging was performed on a microPET R4 (Siemens).

Results: N4-AMT was confirmed by NMR and mass spectrometry. Radiochemical purity of 68Ga N4-AMT was > 96 %. The specific activity of 68Ga-N4-AMT was 0.13 Ci/mmol. The lung tumor was clearly visualized by 68Ga N4-AMT but poorly with 18F-FDG or 68Ga-N4 at 45 minutes post-injection. From dynamic scans acquired, tumor-to-muscle uptake ratios were ranged 3 to 8 in a breast tumor-bearing rat from 60 to 90 min.

Conclusions: PET with 68Ga N4-AMT is a promising and sensitive agent for detection of tumors. The cellular kinetic uptake, mechanistic studies and biodistribution of this novel tracer in tumor models are underway.

This Article Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Kong, F. Articles by Yang, D. PubMed Articles by Kong, F. Articles by Yang, D.