Abstract
1020
Objectives: To improve the therapeutic efficiency of radioactive 131I in HCT116 colon cancer by utilizing the nanocomposite of 131I, Au nanoparticles (AuNPs) and cell penetrating peptide (TAT).
Methods: AuNPs (averaged 9.12 ± 1.19 nm) modified with PEG was conjuncted with TAT (Au@PEG-TAT) for cell-nucleus targeting, and 131I was labeled to AuNPs (131I-AuNPs), TAT (131I-TAT) and AuNPs@PEG-TAT (131I-AuNPs-TAT), respectively. In cellular level, clone formation assay was conducted for evaluating cell proliferation, and flow cytometry for cell apoptosis, ROS level and cell cycle distribution. DNA doublestrand breaks (DSBs) was detected by γ-H2AX staining. In vivo, tumor-bearing BALB/c mice were treated with different drugs and monitored by SPECT/CT for drug metabolism. Tumors were measured for volume every two days, and tested for the expression level of CD19 and CD56 antibodies by immunohistochemical analysis, Western Blotting, and flow cytometry.
Results: Improved cell nucleus uptake of AuNPs@PEG-TAT than AuNPs was confirmed by confocal microscopy and Bio-TEM. CCK-8 assay indicated the optimal usage of 500 μCi 131I consponding to 100ug AuNPs and 10ug TAT. Cells treated with 131I-AuNPs-TAT showed dose-dependently supressed proliferation with the lowest colony efficiency (1.04%) and surviving fraction (0.01%) at 40μCi 131I, and exhibited the highest apoptosis rate (73.12%) compared to 131I-AuNPs (61.82%), 131I-TAT (46.96%) and 131I (31.44%). Further, 131I-AuNPs-TAT generated most ROS (56.55% VS 29.21% VS 42.69% VS 46.22%), caused 18.67±19.33,9.17±13.41,1.31±0.41 times of DSBs than others, and showed largest G2/M proportion (45.12%) with 1.12-, 1.87- and 2.37- folds increased than others. SPECT/CT imaging showed prolonged intratumor retention of 131I-AuNPs for 12 hours and 131I-AuNPs-TAT for 36 hours. Tumor growth treated with 131I-AuNPs-TAT was inhibited by 44.74% ± 3.61%, 68.98% ± 4.55%, and 79.95% ± 2.21% relative to 131I-AuNPs, 131I-TAT and 131I. Elevated anti-cancer CD19+ and CD56+ effector in tumor irradiated by 131I-AuNPs-TAT was found in immunohistochemical staining and Western Blotting, and flow cytometry showed the highest proportion of B and NK cells (12.47%±1.15%) than other therapeutic controls (4.75%±2.87%, 6.57%±3.48%, 4.22%±2.51%).
Conclusions: The as-synthesized 131I-AuNPs-TAT, based on bremsstrahlung reaction between high-Z AuNPs and β-ray from 131I, provided enhanced therapeutic efficiency under TAT mediated intra-nucleus radiotherapy, and the additional immune enhancement effect induced by low-dose X-ray can also work as a complementary mechanism for the ideal treatment outcome. $$graphic_7266E0F9-C662-4286-B848-72B277EE721E$$
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