Platinum-Prodrug-Based Multifunctional Gene Vector For Synergistic Treatment Of Cancers

As one of the three traditional treatment methods,chemotherapy is an effective means of cancer therapy.Among the many chemotherapeutic drugs,platinum-based drugs have been involved in treating more than half of cancers in clinics.However,the lack of selectivity,low solubility,short blood circulation time and vulnerability of being metabolized has largely restricted their further clinical application.More seriously,innate or acquired drug resistance has attenuated their effectiveness for certain patients.Recently,gene therapy that can cure diseases at the genetic level,has showed great potential in cancer treatment.Compared with anticarcinogens,gene drugs have the advantages of specific targets,high selectivity,accurate regulation of the pathogenic gene expression,and no drug resistance.Therefore,to tackle the drug resistance and heterogeneity of tumor,the combination of gene therapy and platinum-based chemotherapy could be a promising strategy,which can suppress the proliferation of cancer cells at the genetic level and enhance the efficacy of chemotherapy drugs at the same time.Meanwhile,considering the problems in the process of in vivo application of platinum drugs and genes,it is of great significance to design the platinum-based drug and gene drug co-delivery systems for the combination of chemotherapy and gene therapy.In recent years,nanosystems have shown great superiority in the fundamental researches and clinical applications,such as improving drug solubility,prolonging drug blood circulation time and increasing drug concentration at target sites.Up to now,there have been some nanocarriers developed to co-load the platinum drugs and gene drugs.However,the low loading content of drugs and genes,absence of efficient endo/lysosomal escape ability and uncontrollability of drug release and gene unpacking limits the maximization of the combinational therapeutic efficacy.Therefore,the novel co-delivery systems which can solve the above problems are of importance for the development of combined therapy.Platinum(?)prodrugs have been brought into researchers' focus as they have lower toxicity compared with platinum(?)drugs and can be activated by mild light irradiation or reductants to release cytotoxic Pt(?)drugs.By introducing the Pt(?)prodrugs into side chain or main chain of polymers,stimulation-responsive nanodrugs would be obtained owning to the light or reductive responsiveness of Pt(?)prodrugs.They will improve the bioavailability and reduce the toxicity of platinum drugs.Based on these advantages,this paper will focus on the design of Pt(?)prodrugs-based multifunctional gene vectors to realize controllable co-delivery of platinum drugs and genes,so as to maximize the combined therapeutic effect.Firstly,we developed a photoactivatable Pt(?)prodrug-backboned polymeric nanoparticle system(CNPPtCP/si(c-fos))for light-controlled co-delivery of the Pt(?)prodrug and siRNA.Compared to previous platinum drugs and gene co-delivery systems,this nanosystem:1)The Pt(?)prodrug-backboned polymer with an extraordinarily high drug loading content was used as carrier that can avoid the complicated drug loading process;2)Under mild light irradiation,CNPPtCP/si(c-fos)can effectively produce azidyl radicals(N3·),for the first time,to promote endo/lysosome escape;3)Pt(?)releasing and si(c-fos)unpacking could occur simultaneously in a controlled manner as desired;4)CNPPtCP/si(c-fos)has good stability and tumor targeting ability,which improves the drug accumulation in tumor sites.Under light conditions,CNPPtCP/si(c-fos)can efficiently silence the expression of c-fos in vitro and in vivo,thus reversing the Pt-based drug resistance and enhancing the antitumor efficacy on platinus-resistant ovarian cancer,achieving synergistic photoactivated chemotherapy(PACT)and RNAi.For better tissue penetration and theranostics,a near-infrared(NIR)photoactivable Pt(?)/siRNA co-delivery upconverison nanoparticles(UCNP@Pt@siRNA)was developed for in vivo multimodality imaging and synergistic cancer therapy.The experimental results displayed that the UCNP@Pt@siRNA has good capability of up-conversion fluorescence imaging(UCL),magnetic resonance imaging(MRI)and CT imaging.Under the excitation of 980nm NIR,UCNP could emit from ultraviolet to visible light to activate the Pt(?)prodrug-backboned polymer on the surface of UCNP@Pt@siRNA,resulting in the release of Pt(?)and the unpacking of siRNA.The nanosystem can achieve effective gene silencing and enhance the effect of combination therapy under NIR irradiation in vitro and in vivo,which provides a more convenient and feasible path for combination of chemotherapy and gene therapy.To date,there have been no studies using single nanocarrier to combine platinum-based chemotherapy and CRISPR/Cas9 gene editing for cancer therapy.Herein,we designed a simple chain-shattering Pt(?)prodrug-backboned polymeric nanoplatform(NPcspt)for the delivery of the CRISPR/Cas9 system(NPCSPt/pEZH2).The NPCSPt/pEZH2 can effectively deliver the CRISPR/Cas9 system into cells and escape from endo/lysosomes.Thereafter,The polymer(CSPt)in NPCSPt/pEZH2 can be degraded by the reductive agent in the cancer cells in a chain-sharttering manner,and then the CRISPR/Cas9 system and Pt(?)could be released simultaneously for effective gene editing of the EZH2.After silencing the EZH2,H3K27me3 protein will also be downregulated,resulting in a looser chromosome structure in the nucleus,which would increase the binding of Pt(?)to nuclear DNA and finally lead to more DNA damage and cancer celldeath.Finally,NPCSPt/pEZH2 can significantly inhibit the proliferation of prostate cancer cells and the growth of subcutaneous xenograft tumor.