Objective:

To prepare

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Tc-labeled hydrazino-nicotinamide (HYNIC) plectin targeted peptide (PTP) and investigate its feasibility as a single photon emission computed tomography (SPECT) imaging agent for pancreatic cancer.

Methods:

The N-terminal of PTP was modified with HYNIC and fluorescein isothiocyanate (FITC) to form HYNIC-PTP and FITC-PTP

which are respectively used for radiolabeling of

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Tc and evaluation of targeting ability by flow cytometry.

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Tc-HYNIC-PTP was prepared in a phosphate-buffered saline (PBS

pH=6.0) with the presence of co-ligands tricine and ethylenediamine diacetate at 100 C for 10 min

SnCl 2 as reducing agent. The radiochemical purities of

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Tc-HYNIC-PTP in PBS (at room temperature) and fetal bovine serum (at 37℃) at different time points was tested using instant thin layer chromatography (ITLC) to evaluate the stability

in vitro

. The potential cytotoxicity of HYNIC-PTP was analyzed using cell counting kit-8 (CCK-8) assays. Western blot was used to analyzethe expression level of plectin protein in both BxPC-3 and PANC-1 pancreatic cancer cells

and -TC-6 cells were set as negative control. The targeting of FITC-PTP to BxPC-3 cells was determined by flow cytometry

and PANC-1 cells were used as a positive control. SPECT images were acquired to observe the tumor uptake at 0.5

1.0

2.0

4.0 and 6.0 h after intravenous injection of

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Tc- HYNIC-PTP into nude mice bearing pancreatic cancer xenografts.

Results:

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Tc-HYNIC-PTP has high radiochemical purity (＞99%) and good stability in vitro. The plectin protein expression in both BxPC-3 and PANC-1 cells were much higher than that of -TC-6 ce

lls. The flow cytometry results showed that the target binding rate of FITC-PTP was also high in BxPC-3 cells when compared to PANC-1 cells. As for tumor accumulation

the SPECT signal intensity in tumor region was observed at 0.5 h post- injection and further enhanced at 1.0 h post-injection. The strongest tumor signal intensities appeared at 2.0 h post-injection

followed by a gradual decrease in tumor accumulation at 4.0 and 6.0 h post-injection.

Conclusion:

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Tc-HYNIC-PTP was successfully obtained using a facile preparation method with high radiochemical purity and stability in vitro. SPECT imaging showed that

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Tc- HYNIC-PTP could obviously accumulate in the tumor region

suggesting great potential to be developed as a molecular imaging probe for pancreatic cancer.