| Because of the increasment of incidence and mortality year by year, cancer hasbecome one of the most serious diseases to human health. Due to less side-effect andwider range of treatment, biological therapy has now become the fourth mostfrequently used therapy for tumor treatment, except for surgery, chemotherapy andradiation. Many tumor vaccines have been under the clinical trials or permitted to beused for the clinical treatment so far.The ideal vaccine targets should have the following characteristics:①strongspecificity. The targets are only expressed in tumor cells, but they are not or lowexpressed in normal cells. If they are expressed in normal tissues, the expressionlevels must have a significant change in quality and quantity in tumor tissue.②Thetumor targets must have a certain broad spectrum, which means that they areexpressed in the majority of tumors.③Antigen-specific antibody and CTL can bedetected in cancer patients. It is suggested that cancer patients has been regarded it asa foreign body and produced immune response against it. Such tumor antigens used asvaccine targets will be easier to break immune tolerance. Survivin and MUC1whichare broadly used have all the three conditions above. Therefore, this thesis intends toapply MUC1and Survivin as the targets of cancer vaccine.Survivin, as a member of IAP families, could both inhibit cell apoptosis andcontrol cell division. Survivin is widely expressed in tumor tissues, but not expressedin terminal devision of normal tissues. It is reported that the expression levels ofsurvivin are associated with drug resistance, poor prognosis and shortened survival,and which make survivin an ideal target antigen of tumor vaccine. The current reportshave revealed that survivin-targeted vaccine has various forms, whereas no report on survivin protein vaccine can be found. This may be due to its poor ability to inducecellular immunity. A suitable immunoadjuvant and optimized immunization strategycan greatly enhance the cellular immune response to this protein vaccine.In order to get a vaccine of higher immunogenicity and better antitumor effection,our research makes survivin as the target of tumor vaccine, uses the protein form ofS8which has lost the function of anti-apoptosis and optimizes the choice of adjuvantof S8proten and the vaccine immunization strategies.Immunoadjuvants such as CpG ODN, incomplete Freund’s adjuvant, aluminiumhydroxide [Al(OH)3] and monophosphoryl lipid A (MPL) have been used to enhanceresponses to a variety of vaccines. DDA/MPL has been shown to enhance antigenuptake and presentation and induce a significant level of protective immunity inChlamydia and tuberculosis vaccine research. However, whether DDA/MPL canenhance efficacy of tumor vaccines has not been reported. A heterologousprime-boost strategy can enhance the cellular immunity of a protein vaccine byapplying different antigen-presenting systems. DDA/MPL, Al(OH)3and anadenovirus prime-protein boost strategy were applied to enhance the survivin-specificimmunity and anti-tumor immunity of a truncated survivin protein vaccine.(Due tosafety concerns of full-length survivin, an anti-apoptosis protein, this vaccine wasbased on a truncated form of survivin (S8) with a deletion of seven amino acids at itsN-terminus, which was shown to be non-functional in our previous study.)It was showed that survivin protein used alone couldn’t induce effective cellularimmunity, and DDA/MPL adjuvant induced stronger antigen-specific cellularresponses than Al(OH)3. Furthermore, comparing to other immunization regimens,recombinant adenovirus prime adjuvanted protein boosted immunization showed thestrongest anti-tumor effect in the murine melanoma model. The anti-tumor effect wasmediated by Th1-typed immune response.MUC1is a transmembrane glycoprotein normally expressed on the apical surfaceof ductal epithelia. A variable number (20–125) of tandem repeats (VNTR) of a20 amino acid sequence which was contained in its extracellular domain is the dominantimmunogenic domain. MUC1(mucin1) is a classic target for cancer immunotherapythat is overexpressed in many adenocarcinomas. Many active immunotherapiestargeting MUC1are in clinical trials. We investigated the immunity response andanti-tumor effect in a murine melanoma model after administration of an AD-9Madenoviral vector prime-recombinant9M protein and DDA/MPL boost. Our resultsdemonstrated that the vaccination induced a significant inhibition of the growth ofB16melanoma in mice and prolonged the survival of B16melanoma–bearing mice.The survival rate was about33%. Due to the heterogeneity of tumor cells, theapplication of a single antigen site vaccine may not be able to induce enough tumorsuppressive effect. Our work evaluated the anti-tumor effect and survival extendanceof the survivin and MUC1combination vaccine in a murine melanoma-bearingmodel. The results showed that the combination could not inhibit the tumor growth,however, it could extend the survival time of tumor-bearing mice. The survival ratewas8.82%compared with AD-S8/S8pro group, and2.78%compared withAD-9M/9M pro group.Due to the heterogeneity of tumor cells and complexity of tumormicroenvironments, many clinical trials of tumor vaccines alone have failed. It isreported that the administration of other therapies such as chemotherapy along with avaccine may enhance its efficacy. The tumor inhibitory effect of our cancer vaccinewas also tested in combination with a widely used anti-tumor chemotherapy drugoxaliplatin. Compared to PBS group, the tumor inhibition rate of oxaliplatin, vaccine,combination of oxaliplatin and vaccine are29.64%，42.59%and54.68%respectively;the survival rate of tumor-bearing mice are22.22%，33.33%and48.15%respectively.It is suggested that oxaliplatin may help to improve the outcome of survivin-basedimmunotherapy. Moreover, the vaccine also alleviated side effects of thechemotherapy drug oxaliplatin, such as emaciation and poor activity.To investigate the most suitable cancer types of vaccine targeting survivin andMUC1, antibody levels of serum from breast cancer, colorectal cancer, overian cancer, esophageal cancer, lung cancer and gastric cancer are evaluated. Our results showedthat the antibody levels are different from cancer types. The sero-positive rate ofMUC1of colorectal cancer, gastric cancer, lung cancer overian cancer, esophagealcancer and breast cancer was18.5%,12%，2%,0,0,10.1%respectively; thesero-positive rate of surviving was31.1%,3%,0,0,2.9%,15.15%respectively. Theinduced anti-tumor effect of vaccine targeting survivin and MUC1was evaluated inmurine colorectal cancer and breast cancer models whose sero-positive rate wererelatively high.The results showed that the AD-MS/S8+9M Pro could significantly inhibittumor growth in murine colon cancer model (P<0.05) and can significantly prolongthe survival time of colon carcinoma-bearing mice (P<0.01). However, AD-MS/S8+9M Pro could significantly inhibit tumor growth in murine breast cancer model(P<0.05) but can’t significantly prolong the survival time of colon carcinoma-bearingmice (P>0.05). The data was in correspondence with the serological test results. Thecombination of vaccine and oxaliplatin had synergistic effects in inhibition andsurvival time prolonging in murine colon cancer model. However, it didn’t havesynergistic effects in murine breast cancer model.Overall, DDA/MPL possibly increased the protein vaccine induced antigen-specific cellular immuneresponse,the strategy adenovirus early immuned withprotein combined with adjuvant to enhance immunization has the strongest tumorinhibition efficiency, this tumor inhibitory effect is mediatedby Th1type immuneresponses.Survivin and MUC1combined immunization is better than the aloneimmune effects. Combined immunity inhibits tumor growth in the model ofmelanoma, mammary gland carcinoma and colon carcinoma. However, it cansignificantly extend the life of the tumor-bearing mice in nurine melanoma and coloncancer model. |
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