A Study Of The Synergistic Effect Of Folate-decorated Polymeric Micelle Incorporating Hydroxycamptothecin With Radiotherapy On Xenografted Human Cervical Carcinoma

Objective: Our objective in this study was to explore the synergistic effect of combination folate-decorated polymeric micelle incorporating Hydroxycamptothecin with radiotherapy on xenografted human cervical carcinoma and the related mechanism of action.Methods: In the present work,to prepare the folate(FA)-decorated amphiphilic block copolymer methoxy polyethylene glycol-polycaprolactone(MPEGPCL-FA),MPEG-PCL was used as raw material to covalently bind with FA by the introduction of –C=C–.Hydroxycamptothecin(HCPT)-loaded MPEG-PCL-FA micelle(HFOL)was formed in water by the selfassembly of MPEG-PCL-FA copolymer and then was characterized in physicochemical properties,including the morphology,the particle size distribution and drug release profiles.The cytotoxicity and targeting ability of the HFOL micelle were investigated by using methylthiazoletetrazolium(MTT)and fluorescence microscopy.The in vivo synergistic effect of the micelle and radiotherapy(RT)was observed in a HeLa xenografted model.The antitumor efficacy was detected by analysis of tumor growth delay(TGD)and median survival time.Micro fluorine-18-deoxyglucose PET/computed tomography(18F-FDG PET/CT)was performed to assess early tumor response to HCPT-loaded micelle in combination with RT.Analysis of cell cycle redistribution by flow cytometry,apoptosis and expression of histone H2 AX phosphorylation(?-H2AX)by immunology analysis was used to evaluate the mechanisms by which HCPT-loaded micelle led to radiosensitization.Results: The HFOL micelle was obtained by self-assembly in water,and achieved a hydrodynamic diameter about of 132 nm.HCPT release from the micelle exhibited no initial burst but showed a sustained release profile.The results of MTT and fluorescence microscopy demonstrated that the HFOL micelle had superior cytotoxicity against HeLa cells compared to non-conjugated micelles,and that they exerted this effect by folate receptor(FR)-mediated endocytosis.The in vivo studies demonstrated that compared with the control group and other treatment groups,the HFOL+RT group has a better treatment efficacy with a TGD of 45 days and median survival time of 83.5 days.In the 18F-FDG PET/CT imaging,there were significant differences in T/M values between the three groups(P < 0.01),which were 2.529 ± 0.157,1.522 ± 0.043 and 1.129 ± 0.389.The measured positive index(PI)value of ?-H2 AX in the different treatment groups was observed in the following decreasing order: HFOL + RT > HMEP + RT > HCPT + RT > RT > HCPT.In addition,in RT + HMEP/HFOL groups,both treatment regimens increased the percentage of cells in G2/M phase and decreased the percentage of cells in S phase compared with the control group.And RT+HMEP/HFOL groups induced more cell apoptosis with the percentage of TUNEL-positive cells of 51.2 ± 4.3% and 65.8 ± 3.1%,respectively.Conclusions: Folate-decorated polymeric micelle incorporating Hydroxycamptothecin(HFOL)is a promising carrier for anticancer drugs,using FR-mediated endocytosis as a means by which to specifically target cervical tumor cells.Moreover,the HFOL micelle is a promising radiosensitization reagent for the treatment of cervical carcinoma and the mechanisms of radiosensitization are possibly as a consequence of cell apoptosis,G2/M phase arrest and DNA damage.Furthermore,this kind of micelle has potential benefit in other malignant tumors,such as ovarian,nasopharyngeal,cervical and chorion carcinomas,which express high levels of FR.