Radiation-enhanced endostatin gene expression and effects of combination treatment

Targeting cells that support tumor growth by administering potent angiogenesis inhibitors is currently an area of intense interest. In the present study, a unique plasmid vector for the mouse endostatin gene, pXLG-mEndo, was constructed and evaluated with and without radiation using the Lewis lung carcinoma (LLC) cell line. The physical properties of the expressed endostatin protein were validated by PCR, gel electrophoresis, and Western blot. Enzyme-linked immunosorbent and immunocytochemical analyses for the therapeutic gene demonstrated that transfected LLC cells secreted the protein into the medium. Exposure of the cells to 2 gray (Gy) gamma-rays reduced the time to reach the maximum expression level of the endostatin gene and also increased the amount of secreted endostatin protein (P<0.001). Biological activity of the endostatin was demonstrated by the inhibition of tube formation by human umbilical vein endothelial cells (HUVEC). Based on (3)H-thymidine incorporation, endostatin expression significantly depressed DNA synthesis in HUVEC and LLC cells compared to controls transfected with parental vector or no vector (P<0.005). In addition, radiation increased the efficiency of endostatin-mediated inhibition of both cell types over a 3-day period post-exposure (P<0.05 or less). Intratumoral injection of 100 small mu g pXLG-mEndo combined with 10 Gy radiation significantly delayed LLC tumor growth, especially when each modality was delivered twice (P<0.05 or less compared to all other groups). No toxicity was observed. These findings are very promising and suggest that endostatin therapy with a plasmid vector, such as pXLG-mEndo, may enhance the efficacy of radiotherapy for lung cancer.     

Radiation and endostatin gene therapy in a lung carcinoma model: pilot data on cells and cytokines that affect angiogenesis and immune status

The dose of radiation that can be safely delivered to cancers residing in sensitive areas such as the lungs is limited by concern for normal tissue damage. Therapies that target tumor vasculature have potential to enhance the efficacy of radiotherapy, with minimal risk for toxicity. We constructed a unique plasmid, pXLG-mEndo, containing the mouse endostatin gene. A significantly greater anti-tumor effect was obtained against Lewis lung carcinoma (LLC) in mice when pXLG-mEndo was combined with radiation compared to radiation alone. Here we report results of cellular and cytokine assessments performed one day after treatment. These analyses were done to obtain baseline data on leukocytes that affect angiogenesis, as well as anti-tumor immunity, and to detect possible treatment-related toxicities. White blood cell counts were dramatically elevated in blood and spleens of untreated tumor-bearing mice, primarily due to granulocytosis. Overall, the effect of radiation was more evident than that of the plasmids (pXLG-mEndo and parental pWS4); radiosensitivity of specific lymphocyte subsets was variable (B > T > NK; CD8+ Tc > CD4+ Th). Tumor presence resulted in dramatically elevated interleukin-2 (IL-2) and decreased tumor necrosis factor-alpha (TNF-alpha) in supernatants of activated splenocytes, but had no significant effect on interferon-gamma (IFN-gamma). Administration of pXLG-mEndo, radiation, or both modified the tumor-induced aberrations in IL-2 and TNF-alpha; IFN-gamma production was decreased by radiation. Red blood cell counts, hemoglobin, and hematocrit were low in tumor-bearing mice, but there were no treatment-related differences among groups. Platelet counts were reduced, whereas their volumes were increased in tumor-bearing mice; both parameters were only slightly affected by either pXLG-mEndo or control plasmid injection, however. The data demonstrate in the Lewis lung carcinoma model that tumor-localized endostatin gene therapy and radiation had significant effects on cells and cytokines that can influence angiogenesis, tumor growth, and immune status.     

Recombinant human endostatin combined with radiotherapy inhibits colorectal cancer growth

Background

To examine the effects of recombinant human endostatin combined with radiotherapy on colorectal cancer HCT-116 cell xenografts in nude mice.

Methods

Forty male BALB/c nude mice were injected with human colorectal cancer HCT-116 cells to form xenografts and then randomized into the following 4 groups (each group comprised ten mice): a control group, an endostatin group (20 mg/kg endostatin once a day for 10 days), a radiotherapy group (a 6-Gy dose was administered via a 6-MV X-ray on day 5 post-inoculation), and a combination therapy group (radiotherapy with endostatin treatment). The tumor growth inhibition rate were detected. CD31, vascular endothelial growth factor (VEGF), and hypoxia inducible factor-1α (HIF-1α) expression and microvascular density (MVD) were evaluated by immunohistochemistry. The expression of VEGF protein was also detected by western blotting.

Results

The tumor growth inhibition rate in the radiotherapy with endostatin treatment group was significantly higher than those in endostatin group or radiotherapy group (77.67% vs 12.31% and 38.59%; n?=?8 per group, P?<?0.05). The results of immunohistochemistry showed that treatment with radiotherapy induced significant increases in CD31, VEGF, and HIF-1α expression and MVD compared with treatment with saline, while treatment with endostatin or radiotherapy with endostatin induced reductions in CD31, VEGF, and HIF-1α expression and MVD compared with treatment with saline (n?=?8 per group, P?<?0.05). The results of western blotting showed that VEGF protein expression in radiotherapy group was significantly increased compared with that in the control group. However, VEGF protein expression in the endostatin or radiotherapy with endostatin groups was significantly decreased compared with that in the control group (n?=?8 per group, P?<?0.05).

Conclusions

Endostatin combined with radiotherapy can significantly inhibit HCT-116 cell xenograft growth, possibly by inhibiting angiogenesis and attenuating tumor cell hypoxia.

     

Combination of human plasminogen kringle 5 with ionizing radiation significantly enhances the efficacy of antitumor effect

Antiangiogenic therapy could destroy tumor vasculature and inhibit tumor growth. It might inhibit tumor growth significantly when used as a single treatment modality and its therapeutic benefit may even be greater when used in combination with established treatment modalities such as radiation therapy (RT). In the present report, we investigated the effect of recombinant human plasminogen kringle 5 domain (rhK5) in combination with ionizing radiation on angiogenesis, tumor growth and survival in a murine Lewis lung carcinoma (LLC) tumor model. Combined treatment using rhK5 and radiotherapy displayed obvious suppressive effect on LLC tumor growth as compared with single treatment with either modality (p < 0.05), and resulted in a more additive effect on tumor growth delay in this model. In addition, combined treatment significantly enhanced the survival of mice and no toxic effect, such as weight loss, was observed. The significant antitumor effect of rhK5 plus radiation was associated with a direct suppression effect on early neoangiogenesis and tumor cell apoptosis. Furthermore, the expression of VEGF and HIF-1alpha in tumor tissue correlated well with decreased vessel density. The results suggest that rhK5 significantly enhances the antitumor activity of RT and could be a potent adjuvant therapeutic approach to improve the efficacy of radiotherapy for lung cancer.     

Gene transfer of endostatin enhances the efficacy of doxorubicin to suppress human hepatocellular carcinomas in mice

Hepatocellular carcinoma (HCC) is one of the most common cancer-related causes of death, and is chemoresistant to anticancer drugs. Anti-angiogenic therapy has been shown to enhance the efficacy of chemotherapy to treat solid tumors. The aim of the present study was to determine whether endostatin, a potent antiangiogenic agent, could enhance the efficacy of doxorubicin to combat HCC. An endostatin expression plasmid was constructed and its expression in vitro and in vivo was detected after gene transfer. Recombinant endostatin inhibited angiogenesis in the chorioallantoic membrane assay, and showed synergistic effects with doxorubicin in inhibiting the in vitro proliferation of endothelial cells, but not that of tumor cells. Both endostatin gene therapy and doxorubicin suppressed the growth of subcutaneous human HepG2 tumors established in BALB/c nude mice, and tumor angiogenesis. Combination therapy with endostatin gene therapy and doxorubicin showed a stronger effect in suppressing tumor growth, and tumor angiogenesis, than the respective monotherapies. Gene transfer of endostatin down-regulated the expression of both hypoxia-inducible factor-1alpha and vascular endothelial growth factor (VEGF), whereas doxorubicin only down-regulated VEGF expression. Endostatin and doxorubicin synergized to down-regulate VEGF expression. Endostatin and doxorubicin combination therapy warrants investigation as a therapeutic strategy to combat HCC.     

Enhanced antiangiogenic therapy of squamous cell carcinoma by combined endostatin and epidermal growth factor receptor-antisense therapy.

PURPOSE: We tested the combined effects of antiangiogenic endostatin and epidermal growth factor receptor (EGFR) antisense gene therapy on squamous cell carcinoma (SCC). EXPERIMENTAL DESIGN and Results: The 1483 cell line of human head and neck SCC (HNSCC) and SCC-VII/SF murine SCC cells was used to establish tumors in nude mice and immunocompetent C3H mice, respectively. Tumor-bearing mice were treated with endostatin (20 mg/kg/day, s.c.), liposomal EGFR-antisense expression plasmid (25 microg/mouse, three times/week, intratumoral), a combination of both agents, or liposomal EGFR-sense plasmid as a control. Endostatin or EGFR-antisense alone significantly, yet partially, inhibited the growth of 1483 and SCC-VII/SF tumors, and a combination of both treatments completely blocked tumor growth. Immunohistochemistry analysis demonstrated that a complete suppression of tumor angiogenesis was achieved by the combination treatment. Down-regulation of vascular endothelial growth factor was shown in EGFR-antisense-treated tumors. These results suggest that the EGFR-antisense treatment, in addition to its inhibitory activity on tumor cell proliferation, might have a synergistic effect with endostatin on SCC-induced angiogenesis. In vitro studies demonstrated that EGFR inhibition by antisense oligonucleotides or EGFR-specific tyrosine kinase inhibitor down-regulated the production of VEGF in HNSCC cells. Additional experiments demonstrated that these EGFR inhibition approaches also directly suppressed the growth of endothelial cells. CONCLUSION: A combination of endostatin and EGFR targeting strategies profoundly inhibited the angiogenesis and growth of SCC in vivo. EGFR-antisense therapy might have multiple inhibitory effects against both tumor cells and endothelial cells, leading to enhanced antitumor efficacy. Such a combination strategy might represent a novel and promising approach for HNSCC therapy.     

Intratumoral administration of endostatin plasmid inhibits vascular growth and perfusion in MCa-4 murine mammary carcinomas

Endostatin, a fragment of the COOH-terminal domain of mouse collagen XVIII is a recently demonstrated endogenous inhibitor of tumor angiogenesis and endothelial cell growth. Antiangiogenic therapy with endostatin in animals requires multiple and prolonged administration of the protein. Gene therapy could provide an alternative approach to continuous local delivery of this antiangiogenic factor in vivo. Established MCa-4 murine mammary carcinomas, grown in immunodeficient mice, were treated with intratumoral injection of endostatin plasmid at 7-day intervals. At the time of sacrifice, 14 days after the first injection, endostatin-treated tumor weights were 51% of controls (P < 0.01). Tumor growth inhibition was accompanied by a marked reduction in total vascular density. Specifically, computerized image analysis showed a 18-21% increase in the median distances between tumor cells and both the nearest anatomical (CD31-stained) vessel [48.1 +/- 3.8 versus 38.3 +/- 1.6 microm (P < 0.05)] and the nearest tumor-specific (CD105-stained) vessel [48.5 +/- 1.5 versus 39.8 +/- 1.5 microm (P < 0.01)]. An increased apoptotic index of tumor cells in endostatin-treated tumors [3.2 +/- 0.5% versus 1.9 +/- 0.3% (P < 0.05)] was observed in conjunction with a significant decrease in tumor perfused vessels (DiOC7 staining), and an increase in tumor cell hypoxia (EF5 staining). Hypoxia resulting from endostatin therapy most likely caused a compensatory increase of in situ vascular endothelial growth factor (VEGF) and VEGF receptor mRNA expression. Increased immunoreactivity of endostatin staining in endostatin-treated tumors was also associated with an increased thrombospondin-1 staining [1.12 +/- 0.16 versus 2.44 +/- 0.35]. Our data suggest that intratumoral delivery of the endostatin gene efficiently suppresses murine mammary carcinoma growth and support the potential utility of the endostatin gene for cancer therapy.     

Prospective analysis of circulating endostatin levels in patients with renal cell carcinoma

BACKGROUND: The aim of the current study was to assess circulating levels of endogenous endostatin in patients with renal carcinoma and to determine the relationship of these levels to circulating levels of vascular endothelial growth factor (VEGF) and prognosis. METHODS: The authors prospectively studied 66 patients (48 male, 18 female; mean age, 50 years) undergoing nephrectomy for renal carcinoma on clinical trials at the National Cancer Institute. Metastases were present in 51 of 66 patients (77%) at the time of nephrectomy. Preoperative and followup serum endostatin and VEGF levels were determined using competitive enzyme immunoassays and compared to a group of 32 age- and gender-matched healthy controls. Associations between circulating endostatin levels and clinicopathologic variables, including survival, were determined. RESULTS: Preoperative endostatin levels were higher in renal carcinoma patients than in healthy controls (P = 0.05). There was a weak to moderate correlation between pretreatment serum endostatin levels and serum VEGF levels (r = 0.47; P = 0.001), and levels of both proteins increased significantly following nephrectomy (P < 0.0001 and P < 0.0001, respectively; n = 41). In addition, patients whose endostatin levels increased more than twofold after nephrectomy had significantly poorer prognoses than patients without such an increase (P = 0.018). This association was more pronounced when patients without metastases were excluded (P = 0.0037). CONCLUSIONS: Circulating endostatin levels are elevated in patients with renal carcinoma and correlate with circulating VEGF levels. Endostatin levels increase after nephrectomy, and patients with the greatest increases experience shortened survival times. These findings suggest an association between tumor aggressiveness and the production of endogenous endostatin in patients with renal carcinoma.     

血管内皮抑制素对Calu-6裸鼠移植瘤的生物学效应

目的 探讨血管内皮抑制素对Calu-6裸鼠移植瘤生长及新生血管形成的影响.方法 在荷瘤裸鼠皮下注射不同剂量的血管内皮抑制素,观察注射后肿瘤体积的变化;应用免疫组化SABC法检测肿瘤组织中血管内皮生长因子(VEGF)、生存素(survivin)和环氧化酶-2(COX-2)蛋白的表达以及微血管密度(MVD)的变化;流式细胞术检测循环血管内皮细胞(CECs)的含量;应用逆转录聚合酶链反应(RT-PCR)和实时定量PCR检测外周血中CD146和CD105 mRNA的表达.结果经血管内皮抑制素治疗后,荷瘤鼠肿瘤体积明显减小;肿瘤组织中VEGF、survivin和COX-2蛋白的表达以及MVD均下降,且各治疗组与阳性对照组间的差异均有统计学意义(均P＜0.05);外周血中CECs、CD146和CD105 mRNA的含量均明显下降;活化CECs的含量与肿瘤组织中survivin和VEGF的表达以及MVD的变化均呈正相关.结论 血管内皮抑制素可通过下调移植瘤中VEGF、survivin和COX.2蛋白的表达以及减少MVD抑制肿瘤生长;活化CECs将可能作为理想的预测抗血管形成治疗预后的标记物应用于临床.     

Endostatin 影响大肠癌裸鼠血管内皮生长因子及其受体机理的实验研究

目的探讨 Endostatin 对裸鼠大肠癌血管内皮生成因子(VEGF)及其受体(Flk-1)的抑制作用的机理.方法建立大肠癌裸鼠模型,将裸鼠分为2组,分别给予 Endostatin 和生理盐水治疗,15 d后处死裸鼠,采集肿瘤标本, 免疫组化法检测瘤株的 VEGF 和 Flk-1 的表达情况.结果Endostatin 对 VEGF 没有抑制作用(P＞0.05),对 Flk-1 有抑制作用(P＜0.05).结论Endostatin 通过竞争性抑制 VEGF 与其 Flk-1 结合实现抑制肿瘤生长的目的.     

Pretreatment serum endostatin as a prognostic indicator in metastatic gastric carcinoma

Endostatin is the C-terminal antiangiogenic fragment of the extracellular matrix protein collagen XVIII, and is generated by tumor-derived proteases. The presence of serum endostatin in patients with gastric cancer has not been reported. The authors assessed the serum levels of endostatin in patients with gastric carcinoma and evaluated their association with the levels of vascular endothelial growth factor (VEGF) and the clinical outcome. A total of 107 patients with gastric cancer were included in the study. Pretherapeutic serum levels of endostatin and VEGF were measured using an ELISA, and compared with those in 23 healthy controls. The serum levels of endostatin and VEGF were higher in gastric cancer patients than in healthy controls (endostatin, 70.1 +/- 16.6 vs. 52.2 +/- 6.2 ng/mL [p < 0.001]; VEGF, 55.1 +/- 7.6 vs. 32.1 +/- 2.4 ng/mL [p < 0.001]; mean +/- SD). Serum endostatin levels were significantly associated with the presence of distant metastases (r = 0.556, p < 0.001) and VEGF levels (r = 0.335, p < 0.001), but not with the depth of tumor invasion, differentiation, or regional lymph node status. A serum endostatin level above the 75th percentile of the distribution for the patients (79.2 ng/mL) was associated with a poor outcome (last follow-up at 42 months; median survival time, 9 vs. 20 months [log-rank, p = 0.017]; median time to progression, 5 vs. 10 months [log-rank, p = 0.022]) in the patients with metastatic gastric cancer. The results suggest for the first time that an elevated serum level of endostatin at the diagnosis of metastatic gastric cancer could be predictive of a poor outcome.     

腺病毒介导的内皮抑素基因治疗小鼠肺癌

目的 探讨内皮抑素对小鼠肺癌生长和转移的抑制作用及其对肿瘤内部新生血管的影响.方法 在C57BL/6小鼠背部皮下注射2×106 lewis肺癌(LLC)细胞,建立小鼠肺癌种植瘤模型,2周后,瘤内注射2×109 pfu内皮抑素腺病毒载体,观察内皮抑素对肿瘤生长、转移及生存率的影响,检测内皮抑素在肿瘤组织的原位表达和血液循环中的表达水平及持续时间.用免疫组化方法,检测肿瘤内部血管密度,观察治疗对肿瘤血管的影响.用透射电镜观察肿瘤细胞的凋亡情况.结果 免疫组化检测结果显示,内皮抑素蛋白在内皮抑素组的肿瘤组织中呈强阳性表达,而在空载体对照组和阴性对照组中呈阴性表达或很少量表达.用酶联免疫吸附实验(ELISA)法检测内皮抑素组血清内皮抑素浓度,第2周可达1540±560 ng/ml;1个月后,血清内皮抑素浓度降至对照水平.内皮抑素组的肿瘤体积和生存率,与空载体对照和阴性对照组比较,差异有统计学意义(P＜0.05).抗CD31抗体标记的肿瘤内血管密度(MVD)在内皮抑素组、空载体对照组和阴性对照组中,分别为37.5±4.6、65.2±5.8和68.5±4.5个/200倍视野,抗CD105抗体标记的肿瘤内MVD分别为10.5±3.2、39.7±5.6和42.4±4.8个/200倍视野,内皮抑素组与空载体对照组和阴性对照组比较,差异有统计学意义(P＜0.05).内皮抑素组的组织在电镜下呈凋亡相的肿瘤细胞多见.结论 腺病毒介导的内皮抑素基因可在体内高效、较长时间表达内皮抑素蛋白,对小鼠皮下种植瘤有一定的治疗作用,其作用的靶点是抑制新生血管的生成.     

Serum endostatin levels are elevated and correlate with serum vascular endothelial growth factor levels in patients with stage IV clear cell renal cancer.

Clear cell renal carcinoma (CCRC) is a highly angiogenic tumor known to secrete vascular endothelial cell growth factor (VEGF). Endostatin is an endogenous antiangiogenic agent with antitumor activity in mice. The purpose of this study was to evaluate serum levels of endostatin in normal subjects and in patients with CCRC and to examine the relationship of these levels to circulating VEGF levels. Fifteen patients (mean age, 48 years) on a clinical protocol for stage IV CCRC at the National Cancer Institute were included in the study. Archived prenephrectomy serum samples were analyzed for endostatin and VEGF concentrations. Endostatin and VEGF levels were compared with those of an age-matched group of volunteer blood donors (n = 18) using a competitive enzyme immunoassay. Data were analyzed using the Mann-Whitney U test and the Spearman rank correlation. Median serum endostatin levels were 24.6 ng/ml (range, 15.1-54.0 ng/ml) in CCRC patients versus 14.1 ng/ml (range, 1.0-19.3 ng/ml) in healthy controls (P < 0.0001). Median VEGF levels were 3.4 ng/ml (range, 0.1-11.2 ng/ml) and 2.5 ng/ml (range, 0.1-4.2 ng/ml), respectively (P = 0.065). A highly significant correlation was observed between endostatin and VEGF levels among the CCRC patients (r = 0.81, P = 0.0003) but not among controls (r = -0.22, P = 0.37). Endostatin levels are detectable in serum from healthy subjects as well as from CCRC patients. Levels are significantly elevated and correlate with VEGF levels in CCRC patients. Elucidating the nature of this correlation may lend insight into the regulation of tumor angiogenesis in patients with renal cancer.     

Serum endostatin levels are elevated in patients with soft tissue sarcoma

BACKGROUND: Solid tumors are angiogenesis dependent, and elevated levels of proangiogenic cytokines have been reported in a variety of histologies. Endostatin is an antiangiogenic fragment of the basement membrane protein, collagen XVIII. Because antiangiogenic protein fragments may be generated by tumor-derived proteases, the authors sought to determine whether circulating levels of endostatin were elevated in patients with localized soft tissue sarcoma. METHODS: The authors analyzed preoperative serum levels of endostatin, vascular endothelial growth factor (VEGF), and basic fibroblast growth factor (bFGF) in 25 patients (14 males and 11 females; mean age, 44 years) with soft tissue sarcoma. For each serum sample, two aliquots were assayed in duplicate using a competitive enzyme immunoassay. Serum levels were compared with levels from 34 age-matched and gender-matched volunteer blood donors. RESULTS: Endostatin levels were significantly higher in sera from sarcoma patients than in sera from healthy controls (43.0 ng/mL vs. 25.8 ng/mL, respectively; P = 0.0002; Mann-Whitney U test). Significant elevations also were noted in VEGF and bFGF levels (P = 0.0002 and P = 0.0001, respectively). Furthermore, endostatin levels > 2 standard deviations above the control mean (55 ng/mL) were associated with an increased risk of tumor recurrence after resection (P = 0.047; log-rank test). CONCLUSIONS: Serum endostatin, VEGF, and bFGF levels are elevated in patients with soft tissue sarcoma. Elevated endostatin levels appear to be associated with tumor aggressiveness. The role of these cytokines in sarcoma angiogenesis and as potential targets for therapy warrants further study.     

Antitumor effects of non-replicative herpes simplex vectors expressing antiangiogenic proteins and thymidine kinase on Lewis lung carcinoma establishment and growth

There is growing evidence that combinations of antiangiogenic proteins with other antineoplastic treatments such as chemo- or radiotherapy and suicide genes-mediated tumor cytotoxicity lead to synergistic effects. In the present work, we tested the activity of two non-replicative herpes simplex virus (HSV)-1-based vectors, encoding human endostatin::angiostatin or endostatin::kringle5 fusion proteins in combination with HSV-1 thymidine kinase (TK) molecule, on endothelial cells (ECs) and Lewis lung carcinoma (LLC) cells. We observed a significant reduction of the in vitro growth, migration and tube formation by primary ECs upon direct infection with the two recombinant vectors or cultivation with conditioned media obtained from the vector-infected LLC cells. Moreover, direct cytotoxic effect of HSV-1 TK on both LLC and ECs was demonstrated. We then tested the vectors in vivo in two experimental settings, that is, LLC tumor growth or establishment, in C57BL/6 mice. The treatment of pre-established subcutaneous tumors with the recombinant vectors with ganciclovir (GCV) induced a significant reduction of tumor growth rate, while the in vitro infection of LLC cells with the antiangiogenic vectors before their implantation in mice flanks, either in presence or absence of GCV, completely abolished the tumor establishment.     

Endostatin improves radioresponse and blocks tumor revascularization after radiation therapy for A431 xenografts in mice

PURPOSE: Clinical trials of antiangiogenic agents used alone for advanced malignancy have been disappointing but preclinical studies suggest that the addition of radiation therapy could improve antitumor efficacy. To test the hypothesis that antiangiogenic therapy combined with radiation therapy can overcome the limitations of antiangiogenic monotherapy, we studied the effects of endostatin combined with radiation on the growth and vascularization of A431 human epidermoid carcinomas growing intramuscularly in the legs of mice. METHODS AND MATERIALS: Mice with established A431 human epidermoid leg tumors were treated with radiation, endostatin, both radiation and endostatin, or vehicle control. The experiment was repeated and mice from each group were killed at 2, 7, and 10 days after irradiation so that tumor tissue could be obtained to further analyze the kinetics of the antitumor, antivascular, and antiangiogenic response to therapy. RESULTS: Endostatin enhanced the antitumor effects of radiation, and prolonged disease-free survival was observed in the combined treatment group. Endothelial cell proliferation was increased in tumors after irradiation but was blocked by the concurrent administration of endostatin, and the combination of endostatin with radiation enhanced endothelial cell apoptosis within 48 h after irradiation. Expression of vascular endothelial growth factor, interleukin-8, and matrix metalloproteinase-2 were increased in tumors after irradiation, and this increase was blocked by concurrent administration of endostatin. CONCLUSION: These data indicate that endostatin can block tumor revascularization after radiation therapy and thereby augment radioresponse.     

Extension of the in vivo half-life of endostatin and its improved anti-tumor activities upon fusion to a humanized antibody against tumor-associated glycoprotein 72 in a mouse model of human colorectal carcinoma

Endostatin is an endogenous angiogenesis inhibitor that exhibits potential anti-tumor efficacy in various preclinical animal models. However, its relatively short in vivo half-life and the long-term, frequent administration of high doses limit its widespread clinical use. In this study, we evaluated whether a fusion protein of murine endostatin (mEndo) to a humanized antibody against tumor-associated glycoprotein 72 (TAG-72), which is highly expressed in several human tumor tissues including colon cancer, can extend the serum half-life and improve the anti-tumor efficacy of endostatin by targeted delivery to the tumor mass. The fusion protein (3E8-mEndo) and mEndo showed improved anti-angiogenic activity in vitro and in vivo, predominantly by interfering with pro-angiogenic signaling triggered by vascular endothelial growth factor (VEGF). Moreover, in mice treated with 3E8-mEndo, we observed a markedly prolonged serum half-life and significantly inhibited tumor growth. The improved anti-tumor activity of 3E8-mEndo can be partially explained by increased local concentration in the tumor mass due to targeted delivery of 3E8-mEndo to implanted colon tumors. Collectively, our data clearly indicate that tumor-targeting antibody fusions to endostatin are a powerful strategy that improves the poor pharmacokinetic profile and anti-tumor efficacy of endostatin.     

反义VEGF基因及内皮抑素基因转染对人巨细胞肺癌生物学行为的影响

目的　探讨反义VEGF基因和内皮抑素基因联合转染在抑制肿瘤血管生成和肿瘤生长转移中的作用。方法　反义VEGF12 1cDNA脂质体法转染人肺巨细胞癌细胞 (PG AS VEGF) ,先行转基因细胞裸鼠异种移植 ,之后电脉冲介导PsectagA 内皮抑素基因转染 ,观察反义VEGF基因和内皮抑素转染对肿瘤血管生成和肿瘤生长转移的调节作用。结果　肿瘤内微血管密度在PG AS VEGF、转染空载体组分别为 40 .6 7± 9.35和5 8.34± 10 .5 2 (P <0 .0 5 ) ;裸鼠体内接种PG AS VEGF细胞后 18天 ,PG AS VEGF、转染空载体组肿瘤体积分别为 (0 .9779± 0 .2 42 1)和 (1.5 2 10± 0 .415 0 )cm3(P <0 .0 5 ) ;PG AS VEGF、转染空载体组淋巴结转移率分别为16 .7% (2 /12 )和 5 0 % (6 /12 ) (P <0 .0 5 )。在肿瘤局部行PsectagA 内皮抑素基因转染的PG AS VEGF瘤 ,当肿瘤生长到 2 1天时 ,肿瘤生长受到明显抑制 ,PsectagA 内皮抑素基因转染组与PsectagA空载体转染组肿瘤体积分别为 (1.5 889± 1.1396 )和 (3 .398± 2 .6 42 )cm3(P <0 .0 5 ) ;两者肿瘤淋巴结转移率分别为 12 .5 % (1/8)和 75 %(6 /8) (P <0 .0 5 )。结论　内皮抑素基因转染对反义VEGF基因转染的PG细胞裸鼠体内生长和淋巴结自发性转移有协同抑制作用。     

Anti-tumor effects of pEgr-1-endostatin-TNF-α recombinant plasmid expression induced by ionizing radiation

Purpose: The aim of the present study was to investigate the anti-tumor effect of a pEgr-1-endostatin-TNF-α recombinant plasmid induced by ionizing radiation. Method: Three hundred and twenty mice bearing Lewis lung carcinomas were divided into four experimental groups: blank control, irradiation treatment, plasmid treatment and plasmid combined irradiation treatment. Twenty-four hours after the recombinant plasmid was injected locally into the tumors of the mice, they were irradiated with 10 Gy γ-rays. The concentration of TNF-α and endostatin in the serum of mice was measured by ELISA and tumor growth in each group was compared. The tumor microvessel density was examined by H&E staining and immunohistochemistry analysis of CD31 positive cells. Results: Radiation could induce the expression of pEgr-1-endostatin-TNFα. The levels of endostatin and TNF-α could express steadily for about 4 weeks, with concentrations of 52.6±4.19 and 12.0±0.87 ng/ml respectively, in the second week in combined therapy group and maintained at relative higher level in the fourth week than other groups (F=29.7, P<0.05). Compared with the control group, the tumor micro vessel density was significantly depressed (P<0.05) and tumor growth was significantly inhibited (5907.2±78.6 mm3 vs. 763.5±12.3 mm3, P <0.05). Conclusions: The expression of pEgr-1-endostatin-TNF-α could be induced in mice in vivo and exhibited more significant anti-tumor and anti-angiogenesis effects than irradiation alone.