Imaging and biodistribution of lipofectamine-mediated 99Tcm labeled EGFR mRNA antisense peptide nucleic acid in SKOV3 tumor-bearing nude mice / 中华核医学与分子影像杂志

ABSTRACT

Objective To evaluate the in vitro effect on tumor cell uptake,tumor imaging and in vivo biodistribution of 99Tcm-epidermal growth factor receptor (EGFR) mRNA antisense PNA probe mediated by cationic liposome.Methods The oligonucleotide with sequence complementary to part of the EGFR mRNA antisense PNA was hybridized in an anti-parallel orientation targeted PNA.PNA hybridization complexes were labeled with 99Tcm by ligand exchange.The assembly of lipofectamine and 99Tcm-labeled heteroduplex was achieved by electrostatic interactions,and the radiolabeled purity was determined by reversedphase HPLC (RP-HPLC).The disparities of cell uptake in SKOV3 cells and the differences of biodistribution and molecular imaging in BALB/c nude mice bearing SKOV3 xenografts between lipofectanine-mediated 99Tcm-EGFR mRNA antisense PNA (group 1) and 99Tcm-EGFR mRNA antisense PNA (group 2) were analyzed.Two-sample t (or t') test and Wilcoxon rank sum test were used for statistical analysis.Results The labeling rates of both group 1 and group 2 were more than 95％ within 6 h.The cell uptake at 1,2,4,6,12,24 h after injection was (28.90±1.12)％,(32.76±1.20)％,(38.20±3.11)％,(41.23±1.60)％,(46.63±1.55)％ and (46.78±2.14)％ in group 1,and was (3.51±0.39)％,(3.90±0.40)％,(4.69±0.18)％,(5.91±0.26)％,(5.30±0.22)％ and (5.39±0.17)％ in group 2 respectively (t'=47.11-58.67,Z=2.80,all P＜0.05).The retention ratios showed significant difference between the two groups (t'=7.25-11.55,Z=2.80,all P＜0.05).The SKOV3 tumor could be visualized in both groups at 1 h post injection but much better visualized in group 1.The T/NT ratios were higher in group 1 at all time points (t =3.96,t'=12.65-14.69,Z=2.83-5.29,all P＜0.05).The T/NT ratios at uptake peak were 5.02 and 3.95,respectively.The probe accumulated mainly in tumor,kidneys and liver.Tumor uptake increased with time ((1.49±0.09) ％ID/g and (2.15±0.21) ％ID/g at 1 h,(3.90±0.65) ％ID/g and (5.00±0.10) ％ID/g at 6 h) after lipofectamine treatment.The ratios of tumor to contralateral muscle were also higher in group 1 (t =11.24,t' =3.96-11.94,all P＜0.05).Conclusions Lipofectamine-mediation can significantly improve the intracellular delivery of radionuclide molecular probe.Lipofectamine-mediated 99Tcm-EGFR mRNA antisense PNA can greatly improve imaging contrast and visualization of EGFR-over-expressing tumors.