Pre-clinical evaluation of a new indirectly labeled ⁹⁹mTc-6-hydrazinopyridine-3-carboxylic acid (HYNIC)-depreotide with HYNIC as bifunctional chelator / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Technetium-99m or (99m)Tc is widely used for labeling peptide in nuclear medicine. Somatostatin and its analog can inhibit tumor cell growth after binding with its receptor. This research was to study the preclinical effect of a new (99m)Tc-6-hydrazinopyridine-3-carboxylic acid (HYNIC)-depreotide, indirect (99m)Tc labeling of depreotide using HYNIC as a bifunctional chelator.</p><p><b>METHODS</b>The cyclopeptide, cyclo-[(N-Me) Phe-Tyr-D-Trp-Lys-Val-Hcy], the linear peptide, and [ClCH(2)-CO×b-Dap-Lys- Cys-Lys×amide] were synthesized by Fmoc solid-phase synthesis. The cyclopeptide and the linear peptide were linked by liquid-phase synthesis. The product depreotide was isolated and purified by high performance liquid chromatography and was confirmed by mass spectrography. Depreotide was labeled with (99m)Tc through a direct labeling method, using HYNIC as a bifunctional chelator. Paper chromatography method was used to calculate the labeling rate, and through the comparative analysis selected the best mark conditions. The new (99m)Tc-HYNIC-depreotide was tested by high-performance liquid chromatography (HPLC). The internalization and externalization rates of the new (99m)Tc-HYNIC-depreotide were studied in A549 cells. Furthermore, biodistribution of the radiopeptide was studied in nude mice, bearing tumors from human lung carcinoma cells SPC-A1.</p><p><b>RESULTS</b>The molecular of synthesize depreotide was 1358, and the purity of it was 95.29%. The labeling efficiency of (99m)Tc-HYNIC-depreotide was highest at pH 6.0 and 15°C, about (70.95 ± 0.84)%. The labeling rate of the new (99m)Tc-HYNIC-depreotide rose to a peak of (20.75 ± 0.48)% at 60 minutes in A549 cells at 37°C and decreased slightly later, while it elevated gradually during the time course at 4°C and 25°C. The internalization rate of the new (99m)Tc-HYNIC-depreotide at 37°C increased gradually and reached the peak of 84.4% in 120 minutes, while the externalization rate of the new (99m)Tc-HYNIC-depreotide was always less than 20%. In mice bearing the experimental SPC-A1 tumor, the new (99m)Tc-HYNIC-depreotide demonstrated a high tumor uptake of (4.05 ± 0.04)% ID/g at 1.5 hpi and remained high ((2.51 ± 0.06)% ID/g) at 4 hpi. The tumor-to-lung activity concentration ratio (T/Lu) was very high for the new (99m)Tc-HYNIC-depreotide at all time points. So did the tumor-to-muscle activity (T/Mu) and tumor-to-blood activity concentration ratios (T/Bl).</p><p><b>CONCLUSION</b>The findings suggested that the new (99m)Tc-HYNIC-depreotide might be a promising candidate radiopharmaceutical for imaging somatostatin receptor positive lung cancer.</p>

Time resolved fluoroimmunoassay for Glypican 3 and its preliminary application / 中华核医学杂志

Objective To establish a time resolved fluoroimmunoassay (TRFIA) method for detecting Glypican 3 (GPC3) and to explore the diagnostic value of serum GPC3 for hepatic carcinoma (HCC). Methods Microplate coated with anti-GPC3 monoclonal antibody 7C8 and GP9 labeled with Eu3+ were used to establish TRFIA kit. The serum concentrations of GPC3 in 41 HCC patients and 44 chronic hepatitis (CH) patients were quantitatively analyzed. AFP was detected by with lowest limit of 2.06 μg/L. The CV of inter and intra assay were 12.25% and 12.91%, respectively. The average serum concentration of GPC3 in HCC patients was (86.68±110.39) μg/L (median: 56.98 μg/L). But in CH patients it was only (14.77±29.48) μg/L, which was significantly lower than that in HCC (Wilcoxon W=1335.00, Z=-4.99, P<0.001). With diagnostic cut-off value set at 42.94 μg/L, the diagnostic sensitivity and specificity of TRFIA GPC3 for HCC were 58.5% (24/41) and 95.5%(42/44) respectively. The diagnostic sensitivity of AFP was 46.3% (19/41) in 41 HCC patients, and was raised to 78.0% (32/41) when combined with GPC3. Conclusions Serum GPC3 assay by TRFIA is established and it could increase the diagnostic sensitivity for HCC when combined with AFP.