[Expression of xenogentic epidermal growth factor receptor ectodomain and its antitumor effect].

AIM: To construct the EGFR protein vaccine and evaluate its antitumor effect. METHODS: The gene of chicken EGFR ectodomain was amplified by PCR, inserted into the pGEX-4T-2 vetor, and then exporessed in E.coli BL21 with glutathione S-transferase in a fusion protein form. The fusion protein was purified by metal affinity chromatography, and refolded by dialysis.Then the mice were immunized with the fusion protein three times. After that, these mice were vaccinated with Lewis cells. At last the growth of tumors was measured and the surm antibody response was measured by ELISA. RESULTS: The ectodomain gene of EGFR was ligated into prokaryotic expression vetor. The expression of the fusion protein was analyzed by SDS-PAGE. The relative moleclar mass of the protein is about M(r); 50,000. After the third immunization, all the mice immunized with the fusion protein showed an antibody response towards the EGFR protein. Compared with the control group, the fusion protein group showed good anti-tumor effects. CONCLUSION: The xenogentic EGFR protein vaccine can overcome the host's immune tolerance problem and induce the production of specific antibodies against.

Co-application of ricin A chain and a recombinant adenovirus expressing ricin B chain as a novel approach for cancer therapy.

AIM: To develop a novel ricin-based approach for the safe and effective therapy of cancer. METHODS: The ricin A chain (RTA) was expressed in Escherichia coli in the form of a 6XHis-tagged fusion protein and purified with Ni(2+)-NTA affinity resin. A replication-deficient ricin B chain (RTB)-expression adenovirus green fluorescence protein (AdGFP-RTB) was constructed. RTA and AdGFP-RTB were tested for cytotoxicity either individually or in combination in human cell lines HEK293, HeLa, SMMC7721, and HL7702. Cell viability was determined with trypan blue staining or MTT assay. RESULTS: The expression and release of RTB, as well as the entry of RTA into AdGFP-RTB-infected cells were confirmed. When RTA and AdGFP-RTB was used individually, neither was toxic to the cells. When they were applied together, significant cell death was observed in all of the cell lines tested. The cell-killing effect correlated with the amount of RTA protein used, with cell mortality at about 60% at 4.8 mu g RTA in combination with AdGFP-RTB at 100 pfu/cell. No major cell killing was seen when RTA was used in combination with a control adenovirus AdGFP. The treatment of healthy HeLa cells with the virusfree supernatant from AdGFP-RTB/RTA-treated HeLa cells resulted in cell death, suggesting the formation of RTA/RTB complex, and a potential by-stander effect. CONCLUSION: The new approach was successful in vitro. Further modifications of the adenovirus vector, as well as an in vivo study are needed to confirm its potential in cancer therapy.

[Antitumor effect of recombinant T7 phage vaccine expressing xenogenic vascular endothelial growth factor on Lewis lung cancer in mice].

BACKGROUND & OBJECTIVE: Angiogenesis plays an important role in growth and metastasis of tumors. Vascular endothelial growth factor (VEGF) is considered as a fundamental regulator for angiogenesis. This study was to construct a recombinant T7 phage vaccine expressing xenogenic VEGF on the capsid, and test its inhibitory effect on Lewis lung cancer cells in mice. METHODS: VEGF gene was cloned by reverse transcription-polymerase chain reaction (RT-PCR) from human lung cancer tissues, and inserted into phage using T7 Select10-3b kit to construct T7 Select10-3b_VEGF vaccine. The titer of prepared phage reached 1x10(13) pfu/ml. C57BL/6J mice were randomly divided into 3 groups: T7 Select10-3b_VEGF vaccine group (T7-VEGF), T7 phage (T7) group, normal saline (NS) group (10 mice/group). Each mouse was injected with Freundos adjuvant mixed with 1x10(12) pfu/200 microl T7 Select10-3b_VEGF, or T7, or normal saline once a week for 4 weeks. Lewis lung carcinoma model (LL/2) was established in C57BL/6J mice after 4-week immunization. Tumor growth and mouse's physical status were observed during immunization. Tumor weight and serum level of specific anti-VEGF antibody were measured by enzyme-linked immunosorbent assay (ELISA). Microvessel density (MVD) of tumors was detected by immunohistochemistry 14 days after the inoculation of tumor cells. RESULTS: Tumor weight of T7-VEGF vaccine group,T7 group, and NS group were (0.543+/-0.259)g, (0.982+/-0.359)g, (1.169+/-0.460)g, respectively. Tumor weight of T7-VEGF vaccine group was significantly lower than that of NS group (P<0.01). Serum anti-VEGF antibody level in T7-VEGF vaccine group was 1:1,000. MVD was significantly lower in T7-VEGF vaccine group than in NS group (8.5+/-0.8 vs 18.5+/-1.6, P<0.05). MVD in T7 group was 16.4+/-1.3. CONCLUSION: Recombinant T7 phage vaccine expressing xenogenic VEGF can break immunologic tolerance against self-VEGF and inhibit the growth of Lewis lung cancer cells.

[Immunotherapeutic effect of recombinant EGFR phage vaccine on tumors].

OBJECTIVE: To construct a recombined phage vaccine and to evaluate the efficiency of this phage vaccine against EGFR-positive tumors. METHODS: T7 phage display system was used to display five fragments of the extracellular domain of chicken EGFR. The EGFR was expressed as a fused protein on the surface of the T7 phage 10B capsid protein. The EGFR expression of the phage vaccine was verified by Western-blot analysis. Anti-EGFR antibody was detected by ELISA. Splenic lymphocytes of the immunized mice were separated and used to determine the immunotoxic effect against A431 cells. The phage vaccines were injected into C57 mice 4 times before Lewis lung cancer cells inoculation. Tumor volume was recorded to evaluate the anti-tumor effect of each vaccine. RESULTS: Five phage vaccines inserted with the chicken EGFR gene were successfully constructed. Western blot assay showed that the extracellular domain of chicken EGFR proteins were displayed on the surface of the phage. Specific antibody was induced in the immunized mice, compared with the control group. Splenic lymphocytes of the immunized mice were shown to be immunotoxic against A431 cells. The killing rates of the experimental groups were higher than that of control group (P < 0.001, t-Student test). The highest killing rate was (45.74 +/- 7.21)%. The tumor growth was inhibited in the experimental groups compared with those of control groups (P < 0.05 in C1, C2, C3, C4 groups, P > 0.05 in C5 group). CONCLUSION: Our results demonstrated that recombined EGFR phage vaccines may be used to induce therapeutic anti-tumor immunity against EGFR-positive tumors.

[An anti-tumor research of recombinant phage vaccine expressed xenogenic EGFR].

A recombinant phage vaccine expressing EGFR on it's capsid was constructed and used to study the anti-tumor effect. The T7 phage display system was applied to display seven xenogenic (human, chicken) epidermal growth factor receptor extracellular domain fragments. The EGFR fragment was expressed as fused protein with 10B capsid on the surface of T7 phage. The T7-EGFR phage vaccines were injected into C57BL/6J mice, and then Lewis lung cancer cells were inoculated after 4 weeks immunization. The tumor tissue was excised and weighed after 10 days to evaluate the anti-tumor effect of each experimental group. The EGFR expression of the phage vaccine was verified by western-blot analysis. The A431 cells with high expressed EGFR was used to detect the anti-EGFR antibody by flow cytometry analysis. The results showed that the A431 cell can react with the serum obtained from the mice after three-week immunization. The experimental results confirmed that special EGFR antibody could be induced by the T7-EGFR phage vaccine. The T7-EGFR phage vaccine can elicit endogenous special EGFR antibody in mice and is capable of suppressing the tumor proliferation and retarding the growth of Lewis lung cancer. This research can be used to develop an anti-tumor vaccine for the target-therapy of EGFR(+) tumor.