The siRNA treatment for cancer 癌症的siRNA治疗.docx

The siRNA treatment for cancerAbstract: Small interfering RNA(siRNA), also known asshort interfering RNA, plays an important role in theRNA interferencepathway, where it interferes with theexpressionof specific genes with complementary nucleotide sequence. In recent years, siRNA has provided a promising therapeutic modality for the treatment of cancer. Thus, this article will provide an overview of the inhibitory effect exerted by siRNA on various kinds of cancer. It also describes the synergistic effect of siRNA and other therapy. Finally, the delivery system of siRNA will be discussed as well.Key words: siRNA, cancer, treatment, combined therapy, delivery systemIntroduction:Small interfering RNA (siRNA) is a kind of non-coding double-stranded RNAs 2125 nucleotides in length which can effectively inhibit the translation of target mRNAs by binding to their 3-UTR through specific cleavage of perfectly complementary mRNA 1. Thus, siRNA is one kind of theRNA interference(RNAi) pathway. There has recently been an increasing interest in harnessing siRNA to develop novel treatment of various diseases, such as cancer, neurological disorders, age-related macular degeneration and viral infections 2.Among them, siRNAs have displayed considerable promise for the treatment ofcancer because siRNA has distinct advantages over conventional small molecule or protein-based drugs, including high specificity, higher potency and reduced toxicity 2.Therefore, this review will focused primarily on the researches about the siRNA treatment for different kinds of cancer. Secondly, a review of the therapies which combine siRNA and conventional cancer drug will be present in this article. Moreover, the delivery of siRNA will be discussed as well. siRNA can be a novel treatment of cancer:Numberous researches have demonstrated that siRNA could be a potential effective treatment for cancer. Table 1 has summarized the repressive effect of siRNA targeting different genes on various sorts of cancer. From table 1, we can see that siRNA can inhibit tumor cell viability and proliferation. Moreover, siRNA performs the function of inducing apoptosis and reversing multidrug resistance.Table1 Treatment of siRNA for different sorts of cancerCancersiRNA targeted geneFunctionRefprostatecancerIGHG1Zinc finger protein X-linkedHIF-1VEGFJNK-1FASNALKBH3HMGN5HSP27inhibit cell viability promote apoptosisdisturbed angiogenesis3-11gastriccancerPI3KCdx2STAT3inhibit cell growth and proliferationinduce cell apoptosisreduce the motility and invasion12, 13breastcancersCluDNMTsABC transporterOsteopontinPLK1BCL-2HSP27MDM2Nek2A FOXM1P-glycoproteininhibit cell growthand metastasis suppress cell proliferationreverse multidrug resistance14-23esophagealcancerPDK1inhibit cell proliferationinhibitinvasionpromote apoptosis24retinoblastomaHMGP A2reduce cell proliferation25ovariancancerNotch3Bmi-1Gli1Wnt2BKSPincrease response to platinumtherapyinhibit cell growthdecrease telomerase activityinduce anoikis26-31renal carcinomaCXCR4Ki67inhibit cell growth, invasiveness and migrationinduce apoptosis32, 33lung cancerNUPR1EZH2RhoGDICOPS3ZEB-1mTORRRM2SGO-1Plk1inhibit cells proliferation and colony formationinduce apoptosis34-41melanomaBCL-2KSPCOX-2 Integrin 3inhibit migration and metastasisgrowth inhibition31, 42-44colorectalcancerPLSCR1PIK3CA K-RasFOXM1STAT3APRILinhibit proliferation, adhesion, migration and invasionincrease apoptosis13, 45-48hepatic cancerPLSCR1TLR2NET-1STAT3FOXM1HeparanaseIGF-IRinhibit proliferation, adhesion, migration and invasiondecrease the secretion of cytokines46, 47, 49-54pancreaticcancerRibosomal protein L26 Ribosomal protein L29VEGFRAP80FOXM1NestinCOX-2c-SrcTRPM7suppress cell proliferationenhance cell apoptosisimprovechemosensitivity47, 55-60diffuse large B cell lymphomaCDC7increase apoptosis61peripheral nerve sheath tumorSurvivinabrogate cell growthinduce G(2) cell-cycle arrest and marked apoptosis62head and neck carcinoma RRM2SphK1suppress cell proliferation induce apoptosis39, 63cervicalcancerTPX2MDR1induce apoptosis, cell proliferation and invasionreverse multidrug resistance64, 65Abbreviation: Hypoxia-inducible factor-1:HIF-1; c-Jun-N-terminal kinase-1:JNK-1; Fatty acid synthase:FASN; AlkB homolog 3:ALKBH3; heat shock protein:HSP; secreted clusterin:sClu; DNA methyltransferases:DNMTs; ATP-binding cassette transporter:ABC transporter; Polo-like kinase 1:PLK1; NIMA-related kinases 2A:Nek2A; Forkhead box protein M1:FOXM1; Immunoglobulin G heavy chain:IGHG; high mobility group protein A2:HMGP A2; kinesin spindle protein:KSP; ribonucleotide reductase subunit M2:RRM2; nuclear protein 1:NUPR1; shugoshin:SGO-1; Cyclooxygenase-2:COX-2; cell division cycle 7:CDC7; Signal transducer and activator of transcription 3: STAT 3; transient receptor potential melastatin-subfamily member 7 :TRPM7; sphingosine kinase:SphK1; target protein for Xklp2:TPX2; multidrug resistance: MDR; phospholipid scramblase: PLSCR1; neuroepithelial transforming protein 1:NET-1.Whats more, Goldberg MS et al 66 found that Pyruvate kinase M2-specificsiRNAinduced apoptosis and tumor regression. And it is also reported that siRNA targeting programmed death 1 ligands can inhibit a negative regulatory mechanism of tumor-specific T cells resulting in enhanced efficacy of adoptive T-celltherapyofcancerusing genetically modified autologous lymphocytes 67. Taken together, siRNA has potential to be a promising gene therapy against cancer. Combination of siRNA and other therapy enhances therapeutic effect:Currently therapies for cancer include chemotherapy, surgery and radiation. However, the therapeutic effect leaves much to be desired. Thus, there is an increasing need to develop a combinational therapy to enhance the therapeutic effect. Since siRNA alone has shown significant effect on the inhibition of tumor growth, we wonder whether the combination of conventional therapy and siRNA will play synergistic effect as well as attenuating adverse effect of conventional therapy.The epidermal growth factor receptor knockdown bysiRNAfurther decreases the cell growth of lungcancercells that are treated with tyrosine kinase inhibitorsor cetuximab alone, confirming that single agent drug targeting does not achieve a maximal biological effect 68. Xiao Y et al 69 combined chemotherapy and RNA silencing could potentially enhance the therapeutic outcomes in treating neuroendocrine cancers. A research conducted by Koganti S et al 70 has shown that cisplatin at the dose of 1.7mg/kg combined with siRNA was effective in improving the lifespan of tumor bearing mice with significant decrease in nephrotoxicity. The combinedtherapy of siRNA and radiotherapyenhanced the percentage of apoptotic A549 cells and reduced the tumor size, in addition to increasing the survival rate in tumor xenograft experiments 35.The antitumor effect of vitamin K2 (VK2) may be improved by silencing BCL-2 expression in hepatocellular carcinoma cells, which provides support for the combined use of VK2 and siBCL-2 as a promising approach incancergenetherapy 71. Cohen S et al 72 have demonstrated that treatment of cIAP-2 siRNA significantly sensitizes ovarian carcinoma cell to cisplatin. Combined treatments using rituximab and CDC7 siRNA significantly increases apoptosis in large B cell lymphoma subtype cells and plays synergistic effect 61. Whats more, combination of sCD40L with PI3KsiRNAcould significantly decrease tumour size, microvessel density, expression levels of PI3K, survivin and VEGF proteins, and increase apoptosis index 73. And knockdown of RhoGDI strengthened the effect on apoptosis and inhibition of cell viability induced by paclitaxel treatment 36. In addition to decreasing cell proliferation and inducing cell apoptosis, combined treatment stat3-siRNA and endostatin also elicited immune system regulation of various immune cells and cytokines 51.Moreover, combining other genetherapywith siRNA leads to enhancing anti-cancereffects as well. Ahn YH et al 13 administrated adenoviruses harboring the herpes simplex virus thymidine kinase gene into STAT3-silenced CT26 cell tumors and discovered extensive apoptosis and a significant reduction in the tumor size. SiBcl2 and oncolytic adenovirus H101 exhibited synergistic cytotoxic effect in uveal melanoma cell lines and could potentially serve as a novel targeted moleculartherapyfor uveal melanoma 43.Delivery System:Despite all the potential ofsiRNAas a novel class of drugs, the limited cellular uptake, low biological stability, and unfavorable pharmacokinetics of siRNAs have limited their application in the clinic, especially in cancer therapy 74. Consequently, there is a need to develop an effective vector that can lead to high silencing efficiency, low toxicity and immunogenicity of siRNA. Figure 2 has shown the vectors that can be used to deliver siRNA so far. Figure 2NanoparticleNanotechnology has plays an important role in the development of delivery vectors so far, which has been a promising delivery system of siRNA. Researches have found that nanocarriers can efficiently protectsiRNAfrom in vivo degradation and are able to deliver siRNA to tumor cells to perform its inhibitory function 15, 39, 75-82.Chen Z et al 83 has developed a nanoplex platform which was well-tolerated and did not induce liver or kidney toxicity or a significant immune response. Moreover, the nanoplex platform can be easily modified and applied to different cancers, receptors, and pathways to achieve theranostic imaging, as a single agent or in combination with other treatment modalities 83. It has been reported that self-assembled DNA tetrahedral nanoparticles with a well-defined size can deliver siRNAs and silence target genes in tumor cell because the DNA strands are easily programmable, the size of the nanoparticles and the spatial orientation and density ofcancer-targeting ligands on the nanoparticle surface can be controlled precisely 84. Whats more, these nanoparticles showed a longer blood circulation time than the parentsiRNA. Yang X Z et al 85 have combined cationic polymer and lipid-based vehicles as the delivery systems ofsiRNAand demonstrated that this system was stable, nontoxic, highly efficient, and easy to scale up.Guo J et al 86 use a pH-triggered amphiphilic poly-L-lysine nanocarrier to deliver therapeutic siRNA, which shows high silencing efficiency. However, cumulative experience has revealed that upon repeated administration, such delivery system lose their ability to circulate over long periods in the bloodstream. In addition, it impairs the internalization of thesiRNAinto the target cell and its subsequent escape from the endocytic pathway, which reduces biological activity 74.Single walled carbon nanotubes (SWNTs) are of interest as carriers of siRNA because of their ability to cross cell membranes.And relative researches demonstrated that SWNT could be an efficient carrier system of siRNA 20, 87.Hasan W et al 88 developed poly(lactic acid-co-glycolic acid)/siRNAnanoparticles coated with lipids, which were used to deliver therapeuticsiRNAto knockdown genes relevant to prostatecancer and showed high silence efficiency.Masood R et al 63 employed biocompatible gold nanorods as carriers of siRNA, which played a critical role in protecting thesiRNAmolecules against physiological degradation, as well as delivering them inside target cells.Moreover, incorporation ofsiRNAinto stable micelle structures containing the cyclo-Arg-Gly-Asp peptide resulted in increased gene silencing ability, improved cell uptake, and broader subcellular distribution and also improved accumulation in both the tumor mass and tumor-associated blood vessels, indicating that this micellar nanomedicine could potentially expand the utility ofsiRNA-based therapies forcancer treatments that require intravenous injection 89.AntibodyBesides nanoparticles, antibody can also be developed into a vector of siRNA. Yao YD et al 17 complexed PLK1 siRNAs with a Her2-single-chain fragmented antibodies (ScFvs)-protamine peptide fusion protein (F5-P), which suppressed Her2 (+) breastcancercell lines and primary human cancers in orthotopic breastcancermodels.The study conducted by Chen Y et al 90 also showed that scFv(CD44v6)-PEG-g-PEI-SPION is a promising nonviral vector for gastriccancergenetherapyand diagnosis. Furthermore, the delivery of siDNMTs by F5-P, an anti-Her2 single-chain antibody fragment with a positively charged protamine, could also be used to treat Her2-expressing breastcancer 91.Virus and Bacteria:Adenovirus and lentivirus can be used as vector of siRNA as well. Liu J et al 33 have demonstrated that the G250-specific oncolytic adenovirus expressing Ki67-siRNAwas applicable for human renal clear cellcancer therapy. And Shao W et al 92 used polyethyleneimine-coated virus-like particles derived from adeno-associated virus type 2, which were able to condensesiRNAand to protect it from degradation by nucleases and resulted in a high transfection rate in MCF-7 breastcancercells with no significant cytotoxicity. It has been reported that lentivirus-mediatedsiRNAinterference targeting SGO-1 inhibits human nonsmall cell lung cancer cell growth 40. Knockdown of ZEB-1 expression by lentivirus-deliveredsiRNAcould decrease lung adenocarcinoma cell proliferation by delaying S-phase entry and induce cell apoptosis, which led to the inhibition of the tumorigenicity of A549 and H1299 cell lines 93. In addition, Jia H et al 51 successfully delivered Stat3-siRNAand endostatin combined therapies by attenuated Salmonella on orthotopically implanted hepatocarcinoma, which decreased cell proliferation, induced cell apoptosis and inhibited angiogenesis.AptamersAptamers have the properties to bind to a wide range of molecules with high specificity and affinity for their target. These properties together with theirsmallsize and their ease of synthesis make them very attractive and promising for delivering siRNA to cancer tissues 94. Thiel KW et al 18 have demonstrated that the HER2 aptamer-Bcl-2siRNAconjugates selectively internalized into HER2 (+)-cells and silence Bcl-2 gene expression.Asymmetric liposome particlesMokhtarieh AA et al 95 have developed a novel method of producing asymmetric liposome particles (ALPs) with highly efficient siRNA encapsulation. Two kinds of lipid inverted micelles were prepared for the purpose of obtaining ALPs. The inner one is composed of ionizable cationic 1,2-dioleoyl-3-dimethylammonium-propane (DODAP) and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), which entrapsiRNA, and the outer one is composed of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), DOPE, polyethylene glycol-1,2-distearoyl-sn-glycero-3-phosphatidylethanolamine (PEG-PE), and cholesterol. After mixing the inverted micelles, ALPs encapsulatingsiRNAwere obtained by solvent evaporation and dialysis. And the ALPs protectedsiRNAfrom ribonuclease A degradation.Gastrin-releasing peptides Sioud M et al 96 have covalently conjugated asiRNAagainst survivin to Gastrin-releasing peptides (GRPs) to direct siRNAmolecules tocancercells that express the GRP receptor. GRP-siRNAconjugates were taken up bycancercells but not normal mammary epithelial cells or human blood monocytes and inhibited the expression of survivin 96.Nuclear localization signalBy pre-conjugation of nuclear localization signal (NLS) tosiRNA-expressing dsDNA, the anti-cancerefficacy was enhanced due to elevated nuclear delivery. Lo WL et al 97 have found that the NLS-preconjugated siEZH2/siOct4 constructs remarkably repressed epithelial-mesenchymal transdifferentiation and radioresistance in ALDH1+/CD44+ CSC-like cells.Multifunctional quantum dotsLi J M et al 98-100 have developed a series of quantum dots (QDs) functionalized by -cyclodextrin (-CD) coupled to amino acids, some of which can be used to facilitate the delivery of siRNA. In their recent study, two CdSe/ZnSe QDs modified with -CD coupled to L-Arg or L-His were used to simultaneously deliver doxorubicin and siRNAtargeting the MDR1 gene to reverse the multidrug resistance of HeLa cells, which significantly downregulated mdr1 mRNA levels 65.Triethanolamine-core PAMAM dendrimer of generation 5 A triethanolamine-core PAMAM dendrimer of generation 5 (G(5) is able to deliver sticky siRNAs bearing complementary A(n)/T(n) 3-overhangs effectively to a prostatecancermodel and produce potent gene silencing of the HSP 27, leading to a notable anticancer effect. The complementary A(n)/T(n) (n = 5 or 7) overhangs characteristic of these stickysiRNAmolecules help the siRNAmolecules self-assemble into gene-like longer double-stranded RNAs thus endowing a low generation dendrimer with greater delivery capacity 11.PlasmidArtificial plasmids are widely used asvectorsinmolecular cloning, serving to drive the replication ofrecombinant DNAsequences within host organisms. Recently it has been reported that SrcsiRNAplasmid could specifically suppress c-Src expression, inhibit VEGF expression, dampen cell proliferation and enhance gemcitabine chemosensitivity 59.Plasma exosomesIt has been reported that human exosomes effectively delivered the administeredsiRNAinto monocytes and lymphocytes, causing selective gene silencing of mitogen-activated protein kinase 1, suggesting that exosomes coul