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     

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 。     

The inhibitory effects of endostatin on endothelial cells are modulated by extracellular matrix

We investigated the ability of extracellular matrix (ECM) proteins to modulate the response of endothelial cells to both promoters and inhibitors of angiogenesis. Using human dermal microvascular endothelial cells (HDMEC), we found that cells demonstrated different adhesive properties and proliferative responses to the growth factor VEGF depending upon which ECM protein with which they were in contact, with fibronectin having the most impact on VEGF-induced HDMEC proliferation and survival. More importantly, we observed that ECM could modulate the ability of the angiogenic inhibitor endostatin to prevent endothelial cell proliferation, survival and migration. We observed that growth on vitronectin or fibronectin impaired the ability of endostatin to inhibit VEGF-induced HDMEC proliferation to the greatest extent as determined by BrdU incorporation. We found that, following growth on collagen I or collagen IV, endostatin only inhibited VEGF-induced HDMEC proliferation at the highest dose tested (2500 ng/ml). In a similar manner, we observed that growth on ECM proteins modulated the ability of endostatin to induce endothelial cell apoptosis, with growth on collagen I, fibronectin and collagen IV impairing endostatin-induced apoptosis. Interestingly, endostatin inhibited VEGF-induced HDMEC migration following culture on collagen I, collagen IV and laminin, while migration was not inhibited by endostatin following HDMEC culture on other matrices including vitronectin, fibronectin and tenascin-C. These results suggest that different matrix proteins may affect different mechanisms of endostatin inhibition of angiogenesis. Taken together, our results suggest that the ECM may have a profound impact on the ability of angiostatic molecules such as endostatin to inhibit angiogenesis and thus may have impact on the clinical efficacy of such inhibitors.     

Endostatin''s heparan sulfate-binding site is essential for inhibition of angiogenesis and enhances in situ binding to capillary-like structures in bone explants

The functional role of endostatin's affinity for heparan sulfates was addressed using an ex vivo bone angiogenesis model. Capillary-like sprouts showed prominent expression of collagen XVIII/endostatin. Outgrowth of endothelial cells was not altered in the absence of collagen XVIII but inhibited by the addition of recombinant endostatin. Mutant non-heparan sulfate binding endostatin and the collagen XV endostatin homologue were ineffective. The ability of mutant endostatin to bind to capillary structures was reduced when compared to endostatin. Endostatin-XV completely failed to bind to endothelial cells. Our data indicate that endostatin's angiostatic function is heparan sulfate-dependent, and that in situ-binding of endostatin to endothelial cells is increased by heparan sulfates.     

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.     

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.     

腺相关病毒载体介导的Endostatin及K1-5蛋白抗肿瘤血管生成协同作用

为研究腺相关病毒载体介导的内皮抑素(Endostatin)及K1-5蛋白抗肿瘤血管生成协同作用,实验中用含有Endostatin及K1-5基因的重组病毒rAAV-hE和rAAV-K5分别感染BHK-21细胞,并表达分泌出内皮抑素和K1-5蛋白,EIA法测定培养液上清中内皮抑素浓度达36.42ng/m l,免疫斑点印迹实验表明rAAV-K5可介导K1-5的体外表达。重组腺相关病毒(rAAV)介导所表达的内皮抑素和K1-5蛋白对血管内皮细胞增殖具有抑制作用。二者对人脐静脉内皮细胞(ECV-304)的抑制率分别为68.1%和63.1%,对牛毛细血管内皮细胞(BCE)的抑制率分别为41.6%和34.0%。同时二者还有协同效应,用rAAV-hE和rAAV-K5同时感染BHK-21细胞,表达产物对人脐静脉内皮细胞和牛毛细血管内皮细胞的抑制率分别为70.8%和43.8%。动物实验表明,重组病毒rAAV-hE和rAAV-K5转入荷有人肺肿瘤细胞的裸鼠,对肿瘤细胞生长具有抑制作用,同时二者具有协同抗肿瘤作用。     

Endostatin gene therapy delivered by Salmonella choleraesuis in murine tumor models

BACKGROUND: Some anaerobic and facultatively anaerobic bacteria have been used experimentally as anticancer agents because of their selective growth in tumors. In this study, we exploited attenuated Salmonella choleraesuis as a tumoricidal agent and a vector to deliver the endostatin gene for tumor-targeted gene therapy. METHODS: Attenuated S. choleraesuis carrying a eukaryotic expression plasmid encoding reporter gene was used to evaluate its abilities of tumor targeting and gene delivery in three syngeneic murine tumor models. Furthermore, S. choleraesuis carrying the endostatin expression vector was administered intraperitoneally into tumor-bearing mice, and its antitumor effect was evaluated. RESULTS: Systemically administered S. choleraesuis preferentially accumulated within tumors for at least 10 days, forming tumor-to-normal tissue ratios exceeding 1000-10,000 : 1. Transgene expression via S. choleraesuis-mediated gene transfer also persisted for at least 10 days. Host immune responses and tumor hypoxia may influence tumor-targeting potential of S. choleraesuis. When systemically administered into mice bearing melanomas or bladder tumors, S. choleraesuis carrying the endostatin expression vector significantly inhibited tumor growth by 40-70% and prolonged survival of the mice. Furthermore, immunohistochemical studies in the tumors revealed decreased intratumoral microvessel density, reduced expression of vascular endothelial growth factor (VEGF), and increased infiltration of CD8(+) T cells. CONCLUSIONS: These results suggest that tumor-targeted gene therapy using S. choleraesuis carrying the endostatin expression vector, which exerts tumoricidal and antiangiogenic activities, represents a promising strategy for the treatment of solid tumors.