Local Injectable Endostatin Hydrogel Reduced Toxicity And Synergistic Effect Of Combined With Radiotherapy In Lung Cancer

Introduction: Antiangiogenic drugs have the potential to make oxygen delivery more efficient and increase the efficacy of radiotherapy.They can effectively inhibit neovascularization in most solid tumors.In this study,our objective is to use endostatin(ES)as an example to synthesize an anti-angiogenic hydrogel drug and change the route of delivery,then explore the efficacy of the drug and its therapeutic effect in combination with radiotherapy(RT).Methods: The study included 72 female C57 mice,Lewis lung cancer(LLC)cells,and human umbilical vascular endothelial cells(HUVEC).First,endostatin hydrogel(ES-HA-Tyr)was synthesized by physical fusion and chemical crosslinking.An in vitro release test was used to determine the release behavior of ES-HA-Tyr.In vitro,we adopted MTT,Transwell and tube-forming experiments to observe the ability of PBS,hyaluronic acid-tyramine polymer(HA-Tyr),ES,ES-HA-Tyr on proliferation,invasion and tube-forming on HUVEC.In vivo,we established subcutaneous heterograft tumor model of Lewis lung cancer,then randomly divided into 6 groups including PBS,ES,HA-Tyr,ES-HA-Tyr,RT and ES-HA-Tyr+RT for treatment.The tumor volume of each mouse was measured every 2 days and the tumor growth curve was plotted.After 17 days of observation,tumor mass was calculated and tumor tissue and serum were collected.Histopathology was performed with the heart,liver,lung,and kidney tissues in ES,ES-HA-Tyr groups;ELISA used to detect the ES levels in the serum and tumor.We used immunofluorescence investigate mice tumor micro-vessel density(MVD)and pericyte coverage in each group;18FMISO PET/CT imaging to detect tumor hypoxia in each group.Immunohistochemistry was performed to detect the expression of VEGF-A,and HIF-?.Results: We synthesized a sustained-release,injectable endostatin-loaded hydrogel.Before forming,the ES-HA-Tyr was colorless liquid with fluidity;after forming,it was light yellow transparent hydrogel with no fluidity.ES-HA-Tyr showed significant sustained release in vitro,and the cumulative release of endostatin reached 52.66±3.93% on day 14.The decomposition of endostatin hydrogel and its release of endostatin were enzyme-dependent.In vitro,compared with PBS,HA-Tyr and ES,ES-HA-Tyr significantly inhibited the proliferation ability(P<0.05),invasion ability(P<0.01)and tube-forming ability(P<0.01)of HUVEC.In vivo,we observed that compared with the ES group,ES-HA-Tyr decreased the blood drug concentration of endostatin(P<0.01),and significantly reduced the tissue damage of heart,liver,lung and kidney,increased the local drug concentration of endostatin in tumor(P<0.01).In vivo ES-HA-Tyr combined with Radiotherapy,compared with PBS,ES,HA-Tyr,ES-HA-Tyr and RT alone,ES-HA-Tyr +RT effectively reduced tumor micro-vessel density(MVD),increased tumor vascular normalization(P<0.05),and improved tumor hypoxia(P<0.05),and increased radiotherapy response(P<0.05).Conclusions: 1.We successfully established the hydrogel loading system,synthesized endostatin hydrogel,and verified its sustained release effect in vitro.The decomposition of endostatin hydrogel and its release of endostatin were enzyme-dependent.2.The inhibition of endostatin hydrogel on endothelial cell proliferation,invasion and tube formation in vitro was proved to be superior to that of endostatin.3.This experiment also confirmed that endostatin hydrogel increased local drug concentration and decreased blood drug concentration and reduced liver,kidney,and heart tissue toxicity.4.It was confirmed that endostatin hydrogel combined with radiotherapy had a synergistic inhibitory effect on lung cancer,which was manifested in reducing the excessive growth of tumor blood vessels,increasing the coverage of tumor perivascular cells,and reducing hypoxia of tumor tissues,increased radiotherapy response.