Preclinical Study Of Rare Earth Arsenite-mediated Chemoembolization

Purpose:Since arsenic trioxide（As₂O₃,ATO）was approved by the Food and Drug Administration（FDA）for clinical treatment of acute promyelocytic leukemia（APL）in 2000,ATO has been used to treat other hematological cancers and solid tumors.ATO has strong toxicity,which is partly due to its lack of targeting to tumor cells and its limited bioavailability.In addition,overuse will lead to systemic toxicity.Different from traditional arterial chemoembolization（C-TACE）,drug eluting beads（DEB）have the function of simultaneous embolization and continuous release of anticancer drugs in a controllable manner,resulting in local release of drugs in the target tumor.Considering that ATO has high anticancer activity at high concentrations,we believe that the model of DEB-TACE can maximize the efficacy of ATO and reduce the occurrence of adverse reactions.Method:Therefore,a kind of nano-drug eluted beads（NDEB）was designed for chemoembolization of rabbit VX2 liver cancer model.Gadolinium arsenite coated with dextran was synthesized by hydrothermal method as nano-drug elution beads（NDEB）.Its physical and chemical properties were investigated by transmission electron microscopy,Malvern particle size analysis and inductively coupled plasma atomic emission spectrometry（ICP-OES）.Hemolysis test and in vitro phosphate trigger release test were carried out.MTT assay was used to evaluate the toxicity of nano-drug eluted beads（NDEB）on hepatocellular carcinoma cells in vitro.Flow cytometry and Western blotting（WB）were used to study the effect and mechanism of drug on apoptosis of hepatocellular carcinoma cells.The model of VX2 hepatoma was established.After NDEB was administered by TACE,the release process of drugs in animals was explored.The vascular distribution and viability of tumors were evaluated by CT,DSA,color Doppler flow imaging（CDFI）and dynamic contrast enhanced ultrasound（CEUS）.The efficacy and pharmacological mechanism of arsenic nanoparticles were summarized by pathological analysis,immunohistochemistry and biochemical detection.Results:Nano-drug eluting microspheres（NDEB）are composed of core-shell structure of dextran-coated gadolinium arsenite.It is 400-600nm in diameter and has positive charge.In vitro experiments have proved that NDEB has good blood compatibility.The whole drug release process takes about 48 hours.The cytotoxic results further confirmed the delayed and sustainable release of NDEB.At the same time,in the pre-clinical study of nano-drug eluted beads（NDEB）,the sustained release of eluted beads reduced the systemic exposure of arsenic and increased the accumulation of arsenic in the tumor.One week after transarterial chemoembolization,CT and ultrasound showed that the tumor donor vessels were completely occluded.With the continuous embolization of tumor donor vessels,the accumulation of arsenic in the tumor and the continuous consumption of inorganic phosphorus,we found that the tumor necrosis rate of the NDEB group injected by TACE（96.8±3.1%）was much higher than that of the ATO group（64.2±3.9%）.And there was no obvious hepatotoxicity at the treatment dose（arsenic dose 0.4mg～0.8mg）.Preliminary mechanism studies have shown that phosphorus deficiency can not only promote the inhibitory effect of ATO on the proliferation of VX2 cells,but also promote ATO to down-regulate the mitochondrial transmembrane potential of VX2 cells,thus promote the release of pro-apoptotic protein cytochrome C（cytochrome C）,down-regulate the expression of anti-apoptotic protein Bcl-2,reduce the ratio of Bcl-2/bax（pro-apoptotic protein）,and activate cysteine protease 3（Caspase）.Promote ATO to induce apoptosis mediated by mitochondrial pathway.At the same time,it was found that phosphorus deficiency could promote the increase of reactive oxygen species（ROS）in VX2 cells induced by ATO,and induce apoptosis and necrosis of tumor cells by mediating ROS.Conclusion:Nano-drug eluted beads（NDEB）as embolic agent can embolize the blood supply artery of VX2 liver cancer,and as an intraoperative drug,inorganic phosphorus triggers the sustained and slow release of ATO,prolongs the contact time between the drug and tumor tissue and reduces systemic exposure,so as to improve the efficacy and reduce toxicity.Phosphorus deficiency can promote the anti-tumor effect of ATO.NDEB-TACE may be an effective interventional therapy strategy.