Proteomic screening of anaerobically regulated promoters from Salmonella and its antitumor applications

Solid tumors often contain hypoxic and necrotic areas that can be targeted by attenuated Salmonella typhimurium VNP20009 (VNP). We sought to develop a hypoxia- inducible promoter system based on the tumor-specific delivered strain VNP to confine expression of therapeutic gene specifically or selectively within the tumor microenvironment. A hypoxia-inducible promoter - adhE promoter was screened from the hypoxia-regulated endogenous proteins of Salmonella through two-dimensional gel electrophoresis and matrix-assisted laser desorption ionization-time-of-flight/time-of-flight MS-based proteomics approaches. The efficiency and specificity of the selected adhE promoter were validated first in both bacteria and animal tumor models. The adhE promoter could specifically drive GFP gene expression under hypoxia, but not under normoxia. Furthermore, luciferase reporter expression controlled by the system was also confined to the tumors. Finally, we investigated the anticancer efficacy of VNP delivering human endostatin controlled by our adhE promoter system in both murine melanoma and Lewis lung carcinoma models. Our results demonstrated that by the dual effects of tumoricidal and anti-angiogenic activities, the recombinant Salmonella strain could generate enhanced antitumor effects compared with those of unarmed VNP treatment or untreated control. The recombinant VNP could retard tumor growth significantly and extend survival of tumor-bearing mice by inducing more apoptosis and more severe necrosis as well as inhibiting blood vessel density within tumors. Therefore, VNP carrying the endostatin gene under our tumor-targeted expression system holds promise for the treatment of solid tumors.     

肌肉内转内抑素基因对肿瘤生长的抑制作用

 为研究骨骼肌及肿瘤内介导的内抑素基因转移对肿瘤生长的作用 ,利用基因克隆技术构建了内抑素基因真核表达质粒 ,应用电脉冲转移法将质粒转入转肿瘤小鼠骨骼肌或肿瘤中 .结果表明 ,内抑素基因可在骨骼肌或肿瘤内表达 ,并显著抑制肿瘤生长 .这为内抑素基因在肿瘤治疗中的应用进行了探索     

Endostatin gene therapy enhances the efficacy of paclitaxel to suppress breast cancers and metastases in mice

Chemotherapy combined with antiangiogenic therapy is more effective than chemotherapy alone. The aim of this study was to investigate whether endostatin, a potent anti-angiogenic agent, could enhance the efficacy of paclitaxel to combat breast cancer. An expression plasmid encoding mouse endostatin (End-pcDNA3.1) was constructed, which produced intense expression of endostatin and inhibited angiogenesis in the chorioallantoic membrane assay. 4T1 breast tumors were established in BALB/c mice by subcutaneous injection of 1 × 10⁵ 4T1 cells. The End-pcDNA3.1 plasmid diluted in the transfection reagent FuGENE^TM was injected into the tumors (around 100 mm²), and paclitaxel was injected i.p. into the mice. Endostatin gene therapy synergized with paclitaxel in suppressing the growth of 4T1 tumors and their metastasis to the lung and liver. Both endostatin and paclitaxel inhibited tumor angiogenesis and induced cell apoptosis. Despite the finding that endostatin was superior to paclitaxel at inhibiting tumor angiogenesis, paclitaxel was nevertheless more effective at inducing tumor apoptosis. The combination of paclitaxel and endostatin was more effective in suppressing tumor growth, metastases, angiogenesis, and inducing apoptosis than the respective monotherapies. The combinational therapy with endostatin and paclitaxel warrants future investigation as a therapeutic strategy to combat breast cancer.     

T cell augments the antitumor activity of tumor-targeting <Emphasis Type="Italic">Salmonella</Emphasis>

Systemic administration of Salmonella to tumor-bearing mice leads to preferential accumulation within tumor sites and retardation of tumor growth. However, the detailed mechanism of Salmonella-induced antitumor immune response via host T cell remains uncertain. Herein, we used wild-type, CD4⁺ T-cell-deficient, and CD8⁺ T-cell-deficient mice to study the role of T cell in the antitumor immune responses induced by Salmonella enterica serovar Choleraesuis (Salmonella Choleraesuis). When systemically administered into mice bearing tumors, Salmonella Choleraesuis significantly inhibited tumor growth by 50%. In contrast, in T-cell-deficient mice, there was only 34–42% inhibition of tumor growth. We found that treatment with Salmonella Choleraesuis significantly upregulates interferon-γ in wild-type and CD8⁺ T-cell-deficient mice, but not in CD4⁺ T-cell-deficient mice. Furthermore, immunohistochemical staining of the tumors revealed more infiltration of macrophages and neutrophils in wild-type mice after Salmonella Choleraesuis treatment compared with those in T-cell-deficient mice. The antitumor therapeutic effect mediated by Salmonella Choleraesuis is associated with an inflammatory immune response at the tumor site and a tumor T helper 1-type immune response. In conclusion, these results suggest that tumor-targeted therapy using Salmonella Choleraesuis, which exerts tumoricidal effects and stimulates T cell activities, represents a potential strategy for the treatment of tumor.     

内皮抑素与肿瘤治疗

内皮抑素(endostatin)是近年来发现的,天然产生的新血管生成抑制因子。它在体内由胶原ⅩⅧ经酶解产生,可以抑制新血管生成,在肿瘤动物模型中显示出显著的抑瘤活动。通过抑制肿瘤相关的新血管的形成来治疗肿瘤,是目前出现的新疗法,内皮抑素是这种疗法中很有前景的侯选药物之一。在美国已经开始了用内皮抑素治疗肿瘤的Ⅰ期临床试验,关于它的临床前基础实验也在广泛开展。本文综述了内皮抑素在肿瘤治疗中的应用基础研究 。     

Anti-Tumor Effect of a Novel Soluble Recombinant Human Endostatin: Administered as a Single Agent or in Combination with Chemotherapy Agents in Mouse Tumor Models

Background

Angiogenesis has become an attractive target in cancer treatment. Endostatin is one of the potent anti-angiogenesis agents. Its recombinant form expressed in the yeast system is currently under clinical trials. Endostatin suppresses tumor formation through the inhibition of blood vessel growth. It is anticipated that combined therapy using endostatin and cytotoxic compounds may exert an additive effect. In the present study, we expressed and purified recombinant human endostatin (rhEndostatin) that contained 3 additional amino acid residues (arginine, glycine, and serine) at the amino-terminus and 6 histidine residues in its carboxyl terminus. The recombinant protein was expressed in E. Coli and refolded into a soluble form in a large scale purification process. The protein exhibited a potent anti-tumor activity in bioassays. Furthermore, rhEndostatin showed an additive effect with chemotherapy agents including cyclophosphamide (CTX) and cisplatin (DDP).

Methods

rhEndostatin cDNA was cloned into PQE vector and expressed in E. Coli. The protein was refolded through dialysis with an optimized protocol. To establish tumor models, nude mice were subcutaneously injected with human cancer cells (lung carcinoma A549, hepatocellular carcinoma QGY-7703, or breast cancer Bcap37). rhEndostatin and/or DDP was administered peritumorally to evaluate the rate of growth inhibition of A549 tumors. For the tumor metastasis model, mice were injected intravenously with mouse melanoma B16 cells. One day after tumor cell injection, a single dose of rhEndostatin, or in combination with CTX, was administered intravenously or at a site close to the tumor.

Results

rhEndostatin reduced the growth of A549, QGY-7703, and Bcap37 xenograft tumors in a dose dependent manner. When it was administered peritumorally, rhEndostatin exhibited a more potent inhibitory activity. Furthermore, rhEndostatin displayed an additive effect with CTX or DDP on the inhibition of metastasis of B16 tumors or growth of A549 tumors.

Conclusion

Soluble rhEndostatin exhibits a potent anti-tumor activity in mouse xenograft models and it also has an additive effect with CTX and DDP, implying possible applications in clinical settings.     

Dynamic distribution and expression in vivo of human endostatin gene delivered by adenoviral vector

Endostatin, a 20-kDa carboxyl-terminal fragment of collagen XVIII, is a potent inhibitor of endothelial cell proliferation and tumor angiogenesis. We have constructed replication-deficient recombinant adenovirus (Ad-rhE), which encoded secreted human endostatin, and our previous studies showed that Ad-rhE had a potent suppression of tumor growth in vivo. In the present study, we investigated the dynamic distribution and expression of human endostatin gene in vivo using fluorogenic real-time quantitative PCR and enzyme-linked immunosorbent assay(ELISA), respectively, with an injection of 2.0 x10(9)pfu of Ad-rhE. After injection, the Ad-rhE DNAs decreased sharply, but lasted a relative long-term at low concentration (10,000--20,000 copies/mg tissues). Whereas the expressed endostatin rose up rapidly, and reached to the top on day 5 after injection of Ad-rhE, and then decreased sharply, but endostatin in tumors sustained to over 9 days at a certain level. Both Ad-rhE DNAs and endostatin mainly enriched in tumors in vivo, and then in livers. These results suggest that endostatin gene delivered by adenoviral vector can generate a high expression in vivo, and both the metabolism pathways of Ad-rhE DNAs and endostatin in vivo are through the systems of livers.     

Adeno-associated virus-mediated gene transfer of a secreted form of TRAIL inhibits tumor growth and occurrence in an experimental tumor model

BACKGROUND: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces cell death in various tumor cells, but relatively spares normal cells. Recombinant adeno-associated virus (rAAV) vectors have a number of advantages including in vivo long-term gene expression. Here, we assessed the biological activity of a novel, secreted form of TRAIL (sTRAIL) for cancer gene therapy using a rAAV2 vector. METHODS: A plasmid and rAAV2 vectors were constructed encoding sTRAIL composed of a leader sequence, the isoleucine zipper, and the active domain of TRAIL (aa 95-281). The functionality of sTRAIL was validated by cell viability, FACS analysis, caspase-3 activity, and TUNEL staining. rAAV-sTRAIL was injected intratumorally to nude mice bearing human A549 lung tumor cells. Nude mice received A549 tumor cells after intravenous delivery of rAAV-sTRAIL. The antitumor effect was then evaluated by measuring tumor regression and occurrence in the experimental animal. RESULTS: sTRAIL was released from cells transfected with the sTRAIL expression construct or transduced with rAAV-sTRAIL, and induced apoptosis in cancer cells, but spared normal fibroblast cells. Secreted sTRAIL formed oligomers including trimers with intersubunit disulfide. Purified sTRAIL exerted much lower cytotoxicity on primary human hepatocytes compared to recombinant TRAIL. Intratumoral delivery of rAAV-sTRAIL significantly inhibited growth of A549 tumors established in nude mice. A number of apoptotic tumor cells were detected by TUNEL staining in mice treated with rAAV-sTRAIL. Systemic pretreatment with rAAV-sTRAIL significantly inhibited tumor formation in nude mice. CONCLUSION: The results suggest that rAAV-sTRAIL may be useful for local or systemic cancer gene therapy for treating TRAIL-sensitive tumors.     

Inhibition of tumor growth in mice by endostatin derived from abdominal transplanted encapsulated cells

Endostatin,a C-terminal fragment of collagen 18a,inhibits the growth of established tumorsand metastases in vivo by inhibiting angiogenesis.However,the purification procedures required for large-scale production and the attendant cost of these processes,together with the low effectiveness in clinicaltests,suggest that alternative delivery methods might be required for efficient therapeutic use of endostatin.In the present study,we transfected Chinese hamster ovary(CHO)cells with a human endostatin geneexpression vector and encapsulated the CHO cells in alginate-poly-L-lysine microcapsules.The release ofbiologically active endostatin was confirmed using the chicken chorioallantoic membrane assay.The encap-sulated endostatin-expressing CHO cells can inhibit the growth of primary tumors in a subcutaneous B 16tumor model when injected into the abdominal cavity of mouse.These results widen the clinical applicationof the microencapsulated cell endostatin delivery system in cancer treatment.     

大肠杆菌-长双歧杆菌穿梭载体的构建及PTEN在长双歧杆菌中的表达

长双歧杆菌可特异地定植于实体瘤低氧区,可用做肿瘤靶向性基因治疗的载体,而构建大肠杆菌-长双歧杆菌穿梭质粒则被证明是外源基因在长双歧杆菌中稳定表达的有效途径。为了构建能在长双歧杆菌中稳定表达外源基因的穿梭质粒并检测携带抑癌基因的工程菌对小鼠实体瘤的抑制效果,利用软件设计并合成了48条部分序列相互重叠的引物,通过PCR合成了长双歧杆菌质粒pMB1序列及长双歧杆菌HU启动子区序列,插入克隆载体pMD18-T,构建穿梭载体pMB-HU,该载体可在大肠杆菌DH5α及长双歧杆菌L17中稳定复制。PTEN基因编码具有蛋白质和酯类双重特异性磷酸酶活性的抑癌因子。将PTEN基因cDNA序列插入载体pMB-HU中HU启动子下游,构建重组质粒pMB-HU-PTEN,电击转化长双歧杆菌后,Western blot检测表明,表达产物中存在55kDa的PTEN蛋白特异条带。抑癌试验表明:与对照组相比,携带PTEN基因的长双歧杆菌可显著抑制小鼠实体瘤的生长。上述结果为以长双歧杆菌为载体的实体瘤靶向性基因治疗研究奠定了基础。     

Characterization of a Salmonella choleraesuis mutant that cannot multiply within epithelial cells

A mutant of Salmonella choleraesuis was identified that could invade (enter) and penetrate through polarized monolayers of Caco-2 and MDCK epithelial cells at normal levels but was defective for intracellular multiplication within these cells. It was also able to survive inside cultured J774 macrophage cells. These bacteria remained inside membrane-bound vacuoles, which coalesced at later times in the perinuclear region of the epithelial cell. This mutant exhibited slightly slower growth rates in rich or minimal media than the parental strain but was normal for iron usage, phosphate usage, and anaerobic growth and was a prototroph. The mutant was completely avirulent when administered orally or intravenously to susceptible mice. These results suggest that the ability to multiply within eukaryotic cells may contribute to S. choleraesuis virulence.     

体内表达的休眠蛋白抑制裸鼠肿瘤的生长

休眠蛋白 (restin)是内皮抑素 (endostatin)的同源蛋白 ,它们之间相同的氨基酸占整个蛋白质的 6 2 %。休眠蛋白位于胶原XV羧端的非胶原结构域。在大肠杆菌中重组表达的休眠蛋白经复性后可以专一地抑制牛主动脉内皮细胞的生长 ,并引起凋亡。将鼠源的休眠蛋白基因与信号肽连接后克隆入真核表达载体 pCDNA3,取名为pCDNAXV并转染Bel74 0 4细胞。利用RT PCR和Western印迹证实休眠蛋白在稳定转染株中表达。将这一稳定转染株细胞接入裸鼠皮下观察肿瘤生长 ,发现转染有休眠蛋白基因的肿瘤生长显著慢于对照组 ;由于休眠蛋白基因对肿瘤细胞的增殖没有影响 ,这种抑制作用很可能是通过抑制血管生长来实现的。同时 ,这种方法为研究抑制血管生长蛋白提供了新的手段     

可诱导肿瘤靶向性IFN-α2a重组腺病毒的构建及其表达

腺病毒载体广泛应用于恶性肿瘤的靶向性基因治疗的研究,但这些肿瘤靶向载体缺乏可控性,其疗效和安全性受到很大的影响,因此开发新型可诱导的生物肿瘤靶向载体是当今抗肿瘤靶向药物研究的当务之急。该研究构建了可诱导肿瘤靶向性IFN-α2a重组腺病毒。重组腺病毒能够有效感染人肝癌细胞株HepG2等多种肿瘤细胞株,RT-PCR和Western blot结果表明肿瘤细胞能高效表达IFN-α2a,而其非肿瘤细胞株L02几乎没有表达。诱导试验表明重组腺病毒Ad MT-Ⅱ-hTERT/IFN-α2a能被ZnSO4诱导表达。可诱导肿瘤靶向性重组腺病毒Ad MT-Ⅱ-hTERT/IFN-α2a成功构建为下一步体内外抑癌实验研究打下了基础。     

125I-UdR提高内皮抑素基因的抑瘤作用

目的:探讨125I-UdR提高内皮抑素基因对大鼠种植癌模型的抑制效应。方法:制作肿瘤株Walker-256细胞大鼠皮下种植癌的动物模型并分为1-4组(对照组、125I-UdR组、Endostatin组和Endostatin+125I-UdR组),每组20只,通过实体瘤内注射,分别给与相同体积生理盐水125I-UdR、内皮抑素基因及125I-UdR和内皮抑素基因混合物,测量肿瘤治疗前体积(V0)和治疗后不同时间体积(Vt),计算10d、20d的肿瘤生长率(f=Vt/V0),观察各组肿瘤在光镜下的变化。结果:各组大鼠10d、20d肿瘤生长率为:(11.03±1.08、27.35±1.08),(4.02±0.79、7.58±2.98),(3.88±0.26、7.02±2.75),(2.72±1.01、2.94±1.26),2、3、4组的肿瘤生长率明显小于1组(P<0.001);2、3组之间肿瘤生长率差别不明显(P>0.05),4组肿瘤生长率小于2、3组(P<0.01)。结论:通过实体瘤内注射的方法给与125I-UdR、内皮抑素基因及两者混合物后,能够明显抑制肿瘤的生长,内皮抑素基因和125I-UdR联合治疗在抑制肿瘤生长方面作用更加显著。     

Live attenuated Salmonella as a vector for oral cytokine gene therapy in melanoma

Systemic administration of cytokines has shown therapeutic benefits in cancer patients; however, serious adverse effects associated with direct protein administration prevent the wide use of this approach. We have assessed the capacity of live attenuated Salmonella to act as a vector for oral cytokine-gene therapy. Salmonella orally administered to melanoma-bearing mice was found to accumulate within the tumor, reaching up to 10(5) bacteria per gram of tumor by day 21 after bacterial inoculation. Numbers of bacteria recovered from tumor did not differ from those recovered from liver or spleen at any time point. Recombinant bacteria carrying eukaryotic expression vectors encoding the murine IL-4 or IL-18 genes were administered to groups of mice with established subcutaneous melanoma tumors. We found that a single oral dose of Salmonella carrying any of the cytokine-encoding plasmids resulted in significantly increased survival time, as compared with mice that received Salmonella carrying the parental plasmid or PBS. Increased levels of IFNgamma were found in sera of animals receiving either of the cytokine-encoding bacteria, but not in mice receiving Salmonella alone or PBS. Co-administration of both recombinant bacteria maximized the production of IFNgamma. Overall these results suggest that cytokine-encoding Salmonella can be an effective and safer alternative to systemic administration of cytokines for immunotherapy of cancer.     

Combined alpha tumor necrosis factor gene therapy and engineered dendritic cell vaccine in combating well-established tumors

BACKGROUND: Although current immunotherapeutic strategies including adenovirus (AdV)-mediated gene therapy and dendritic cell (DC) vaccine can all stimulate antitumor cytotoxic T lymphocyte (CLT) responses, their therapeutic efficiency has still been limited to generation of prophylactic antitumor immunity against re-challenge with the parental tumor cells or growth inhibition of small tumors in vivo. However, it is the well-established tumors in animal models that mimic clinical patients with existing tumor burdens. Alpha tumor necrosis factor (TNF-alpha) is a multifunctional and immunoregulatory cytokine that induces antitumor activity and activates immune cells such as DCs and T cells. We hypothesized that a combined immunotherapy including gene therapy and DC vaccine would have some advantages over each modality administered as a monotherapy. METHODS: We investigated the antitumor immunotherapeutic efficiency of gene therapy by intratumoral injection of AdVTNF-alpha and DC vaccine using subcutaneous injection of TNF-alpha-gene-engineered DC(TNF-alpha) cells, and further developed a combined AdV-mediated TNF-alpha-gene therapy and TNF-alpha-gene-engineered DC(TNF-alpha) vaccine in combating well-established MO4 tumors expressing the ovalbumin (OVA) gene in an animal model. RESULTS: Our data show that vaccination of DC(TNF-alpha) cells pulsed with the OVA I peptide can (i) stimulate type 1 immune response with enhanced antitumor CTL activities, (ii) induce protective immunity against challenge of 5 x 10(5) MO4 tumor cells, and (iii) reduce growth of the small (3-4 mm in diameter), but not large, established MO4 tumors (6-8 mm in diameter). Our data also show that AdVTNF-alpha-mediated gene therapy can completely eradicate small tumors in 6 out of 8 (75%) mice due to the extensive tumor necrosis formation, but not the large tumors (0%). Interestingly, a combined AdVTNF-alpha-mediated gene therapy and TNF-alpha-gene-engineered DC(TNF-alpha) vaccine is able to cure 3 out of 8 (38%) mice bearing large MO4 tumors, indicating that the combined immunotherapy strategy is much more efficient in combating well-established tumors than monotherapy of either gene therapy or DC vaccine alone. CONCLUSIONS: This novel combined immunotherapy may become a tool of considerable conceptual interest in the implementation of future clinical objectives.