| objective: our purpose was to explore the synergistic anti-tumor effect and mechanism of paclitaxel nanoparticles(PTX-NPs)combined with radiotherapy(RT)on human cervical carcinoma(HeLa).Methods : PTX-NPs were prepared by a solid dispersion method using methoxy poly(ethylene glycol)-poly(ε-caprolactone)(MPEG-PCL),which combined with RT exerted a potent and high efficient effect against cervical cancer.In vitro,The drug loading(DL)、 encapsulation efficiency(EE)and drug release profiles of PTXNPs were determined by a high performance liquid chromatography instrument(HPLC,Agilent 1260,Agilent technologies,USA),and PTX-NPs was characterized in physicochemical properties by dynamic light scattering(DLS,NanoBrook 90 Plus Zeta,Brookhaven,USA),including the morphology,the particle size distribution and the formulation stability.The cytotoxicity of PTX-NPs was comparable with the Taxol? by using methyl thiazolyltetrazolium(MTT).In vivo,72 tumor-bearing mice(200mm2)were randomly divided into 6 groups(each group was 12): Normal saline(NS)representing the control group,PTX(Taxol?),PTX-NPs,RT,PTX+RT and PTX-NPs+RT group(n=12).NS infusion 0.9%,PTX injection or PTX-NPs solution(0.5 mg/ml PTX2.5 mg/kg)were intravenously injected and subsequently tumor irradiation(15Gy/5F)was performed 6 hours post injection.The early tumor response to PTX-NPs in combination with RT were evaluated using micro fluorine-18-deoxyglucose PET/computed tomography(18F-FDG PET/CT).Fifty% of the animals of each group were randomly euthanized 24 h after treatment and the remaining mice in each group were used to investigate the tumor growth delay(TGD)and median survival time.the immunohistochemistry of cell proliferation associated antigen(Ki-67)、micro-vessel density(MVD)associated with CD31 and vascular endothelial growth factor(VEGF)were performed with the euthanized mice.Results: In the experiments,the PTX-NPs of theoretical DL rate of 8% had a higher actual DL(7.96±0.06%)andf free PTX is more than 4μg/mL,the cytotoxicity of PTX-NPs is small than Taxol?(p < 0.05),while when the free PTX concentrations less than 4μg/mL,toxicity between the groups was no significant difference(p >0.05)。In vivo experiment,after 22 days,the tumor volume of PTX-NPs+RT group(623.5mm3)was significantly smaller than PTX+RT group(1121.4 mm3,p < 0.01),RT group(1176.9 mm3,p < 0.01),PTX-NPs group(2074.1 mm3,p < 0.01),PTX group(2197.2 mm3,p < 0.01),and NS group(2347.2 mm3,p < 0.01),and the median survival time of mice in the PTX-NPs+RT group was significantly longer(87 days)compared to the PTX+RT group(61 days,p < 0.01),RT group(64 days,p < 0.01),PTX-NPs group(31 days,p < 0.01),PTX group(34 days,p< 0.01),and NS group(25 days,p < 0.01).PET/CT imaging observed PTX NPs+ RT group(1.182-0.043)and PTX + RT group(2.032 + 0.214),compared with NS group(2.635 + 0.074),lower metabolism of tumor tissue(p < 0.05).In the immunohistochemical trials of related mechanism,a small number of Ki-67 positive cells was observed in the PTX-NPs+RT group(21.7 ± 7.5%)compared to PTX+RT group(40.6 ± 4.4%,p < 0.05),RT group(57.2 ± 5.0%,p < 0.05),NPs group(73.2 ± 5.8%,p < 0.05),PTX group(79.6 ± 6.2%,p < 0.05),or NSgroup(87.2 ± 4.0%,p < 0.05);Fewer immunoreactive microvessels were observed in the tumor tissue sections of PTX-NPs+RT treated mice(2.1 ±0.3%)compared to the PTX+RT group(3.8 ± 0.4%,p < 0.05),RT group(4.2 ± 0.8%,p < 0.05),NPs group(8.7 ± 0.7%,p < 0.05),PTX group(9.0 ± 0.4%,p < 0.05),or NS group(9.8 ± 0.7%,p < 0.05);The expression of VEGF protein in the PTX-NPs+RT group was 30.7±4.0 %,that was actually significantly lower than that of the PTX+RT group(85.6 ± 3.5%,p < 0.01),RT group(89.7±3.5%,p <0.01),NPs group(75.7 ±3.2%,p < 0.01),PTX group(77.4 ± 5.1%,p < 0.01),or NS group(80.0 ± 5.0%,p < 0.01).Conclusion:1、The PTX-NPs prepared in the experiment had a high drug loading、high encapsulation efficiency,good stability,spherical shape,and a single dispersion.in vitro,it exhibited a slow release model and had a lower cytotoxicity against Hela cell.2、The low doses of PTX-NPs combined RT can effectively inhibit the growth of cervical cancer and prolong the median survival period,the results of PET/CT imaging show that the PTX-NPs combined RT can effectively reduce the metabolism of tumor tissues.3 、 The mechanism of PTX-NPs combined RT inhibiting tumor of cervical cancer might PTX-NPs in combination with RT inhibit cell proliferation through its action on Ki-67,and decreased micro-vessel density(MVD)associated with CD31 and vascular endothelial growth factor(VEGF). |
