Tumor Gene Vaccine Optimization And Its Synergistic Anti-tumor Effect With Chemotherapy Drugs

Cancer is harmful to human health. The number of cancer deaths increases yearby year in the world. Tumor prevention and treatment is an important issue all overthe world. As a new biological treatment, tumor gene vaccine gains more and moreattentions nowadays. Tumor gene vaccine is cloning a tumor antigen gene into aneukaryotic expression vector. When immunizing animals with the recombinant vector,the antigen gene will get expressed in the host body and stimulate the body’s specificimmune response which may activate the body’s immune response to eliminate thetumor cells. There are a variety of factors affecting the immune effects of tumor genevaccine, such as antigen of the gene vaccine, vaccine vector, vaccine adjuvants andimmunization strategy.In our preliminary work, we have constructed tumor DNA vaccine CpVR-MSexpressing the tumor antigen MUC1and Survivin fusion protein (using VR1012asthe vector, and CpG motif as an adjuvant) and the recombinant adenovirus vaccineAd-MS was also constructed; we used VR-IL2as vaccine adjuvant and DNA PrimeAd-MS boost immunization strategy to induce specific immune response in mice.This strategy had a better anti-tumor efficient, which could inhibit the tumor growthof tumor-bearing mice and prolong survival of them. In order to further enhance theanti-tumor effect of the tumor vaccine, we optimized the vaccine by studing vaccinedose, vector, conjunction of vaccine and chemotherapy drugs.Firstly, we used CpG motif as a vaccine adjuvant to optimize the dose of thevaccine. In the presence of CpG motif, only a small dose of vaccine can induceimmune response. In order to explore whether the existence of CpG motif could maketumor gene vaccine have good immune effect at lower doses, which could provide atheoretical basis for further optimization of the dose of tumor gene vaccine, this thesisfirst reduce the dose of CpVR-MS vaccine and detect the changes of humoral andcellular immune. The results showed that the existence of CpG motif could enhancethe immunogenicity of the vaccine. The vaccine immunogenicity was the same as thatof the vaccine without CpG motif when vaccine dose reduced100times and vaccine immunogenicity and vaccine dose was positively correlated; tumor treatment testsshowed it still had anti-tumor effect when reduced the dose of the vaccine by10times.Secondly, we optimized the vaccine vector. We cloned CpG motif intobicistronic expression vector DV constructed by other people of our group and furtheroptimized the form of our vaccine. Bicistronic vector containing two expressionframeworks could connect tumor antigen genes and adjuvant gene into the samecarrier. By this means we can avoid impacting structure of the genes when fusionexpressed and different genes will have the same expression environment. At thesame time, using bicistronic vector can simplify the preparation process of vaccinesand reduce the pain of patients caused by multiple injections of vaccines. All thereasons make it a good gene vaccine vector. In this research we inserted16repeat C-type CpG motif into the bicistronic expression vector DV to get the carrier CpDV.Then the IL-2and MS genes were connected into the two CMV promoters to get thevaccine CpDV-IL2-MS. The results of comparing the vaccine effect of CpDV-IL2-MS with CpVR-MS showed that they could induce immune response in the samelevel and have similar ability to inhibit tumor growth; however, vaccine CpVR-MShad better ability to prolong the life of tumor-bearing mice.Thirdly, we combined tumor vaccine and chemotherapy drugs to enhance theanti-tumor effect. This strategy can make tumor cells more sensitive to the cytotoxicresponse induced by immunotherapy, increase the anti-tumor effect, inhibit tumormetastases and avoid the generation of tumor immune tolerance. It is an effective newprogram for tumor treatment. Platinum is a cytotoxic anti-cancer drugs, which is usedfor the treatment of a variety of tumors. At present, there are three generations ofplatinum drugs, such as cisplatin, carboplatin and Oxaliplatin. Oxaliplatin which is thethird generation of platinum drugs is used for kinds of tumor treatments. In this study,we joint vaccine CpDV-IL2-MS and CpVR-MS with Oxaliplatin and studied theiranti-tumor effects on tumor-bearing mice. The results showed that, when combinedCpDV-IL2-MS with Oxaliplatin, the rate of tumor inhibition increased by8.33%, andthe life extension rate increased by37.77%; when combined CpVR-MS withOxaliplatin, the rate of tumor inhibition increased by11.66%; so vaccines andchemotherapy drugs have synergistic anti-tumor effect. This thesis also compared theantitumor effect of CpDV-IL2-MS/Oxaliplatin with CpVR-MS/Oxaliplatin, resultsshowed that they could inhibit tumor growth at the same level. However, whencompared with CpVR-MS/Oxaliplatin, the life prolongation rate of CpDV-IL2- MS/Oxaliplatin increased by18.74%. Therefore, CpDV-IL2-MS and Oxaliplatinshowed a significant advantage in tumor treatment.In summary, CpG motif could enhance the immune effect of our tumor genevaccine and the vaccine immunogenicity was positively correlated with vaccine dose;bicistronic vector vaccine CpDV-IL2-MS and CpVR-MS had similar immuneinducing effects as well as tumor inhibition effects, but the life extension ability ofCpDV-IL2-MS was lower than CpVR-MS. However, when combined withchemotherapy drugs, CpDV-IL2-MS showed a significant advantage. Thus our thesisconcluded that, CpDV-IL2-MS joint with Oxaliplatin could be used as a new stratagefor tumor treatment.