Serum Endostatin Concentrations Research Articles

Evaluating the relationship between endostatin and cognition in mild cognitive impairment (MCI), coronary artery disease (CAD), and Alzheimer’s disease (AD)

AbstractBackgroundEndostatin is an endogenous angiogenesis inhibitor that can regulate pro‐and anti‐angiogenic factors, notably vascular endothelial growth factor. Research shows that endostatin levels in the brain are associated with amyloid plaque formation in Alzheimer’s disease (AD), and may contribute to AD pathogenesis. Hence, endostatin may be relevant to the broad range of cognitive impairments, namely people with mild cognitive impairment (MCI), AD, and/or coronary artery disease (CAD) who are at risk for cognitive impairment. We examine associations between serum endostatin and global cognition.MethodsParticipants with MCI, AD, or CAD (with or without MCI) were recruited. Serum endostatin concentrations were measured and analyzed using enzyme‐linked immunosorbent assays. MCI was diagnosed using either the Petersen criteria or the Diagnostic and Statistical Manual of Mental Disorders (DSM‐5) criteria. AD was diagnosed using DSM‐5 criteria. CAD was defined as at least 1 of previous hospitalization for acute myocardial infarction, coronary angiographic evidence of ≥ 50% blockage in ≥ 1 major coronary artery or a prior revascularization procedure. Global cognition was assessed by the Montreal Cognitive Assessment (MoCA). Linear regression analyses were used to assess the association between endostatin levels and global cognition with and without covariates. Endostatin levels were log‐transformed prior to analyses due to significant departure from normality in Shapiro‐Wilk tests.ResultsIn 119 participants, 94 (79.0%) were male, 102 (85.7%) had CAD, and 23 (19.3%) had MCI or AD; the mean(SD) age was 65.6(7.5), years of education were 16.4(3.3), and endostatin levels were 156.3(38.6) ng/mL. Endostatin was associated with global cognition alone [F(1,117) = 11.39, p <.001, R2 = .089] and also when considering covariates: age, sex, body mass index (BMI), education, MCI/AD diagnosis, and CAD diagnosis [F(7,111) = 11.27, p< .001, R2 = .415]. All variables except age, sex, BMI, and CAD diagnosis added significantly to the association (p< .05). Controlling for other variables, one log endostatin unit was associated with a total MoCA score 5.08 (SE= 2.52) points lower.ConclusionIn this sample, lower serum endostatin concentrations were associated with higher cognitive performance. This relationship may support the involvement of endostatin in cognitive functions and neurodegenerative diseases.

Endostatin Is an Independent Risk Factor of Graft Loss after Kidney Transplant

Background: Endostatin is a 20-kDa C-terminal fragment of collagen XVIII, known for its ability to inhibit the proliferation of capillary endothelial cells. Previous studies suggested that circulating endostatin independently predicts incident chronic kidney disease. However, the impact of endostatin on graft loss level in kidney transplant recipients (KTRs) remains unknown. Methods: We conducted a prospective observational cohort study in 574 maintenance KTRs. Patients were followed for kidney graft loss and all-cause mortality during a median follow-up of 48 months. Serum-, and urine-samples and clinical data were collected at baseline. Serum Endostatin concentration was analyzed by an ELISA. Results: Among 574 patients, 37 patients had graft loss and 62 patients died. For graft loss, the optimal cut-off value based on receiver operating characteristics analysis (area under the curve 0.79, 95% CI 0.71–0.86, p < 0.001) of endostatin was 147.3 pmol/L. Kaplan-Meier curves revealed that higher serum endostatin concentrations positively correlated with graft loss (p < 0.001). Multivariable Cox regression analyses showed that baseline endostatin concentrations were significantly associated with graft loss after adjusting for graft loss risk factors (adjusted hazard ratio [HR] 8.34; 95% CI 2.19–31.72; p = 0.002). The adjusted HRs for classical graft loss risk factors such as baseline estimated glomerular filtration rate and urinary protein excretion were lower (1.91 and 5.44, respectively). In contrast to graft loss, baseline endostatin concentrations were not associated with all-cause mortality. Conclusion: Increased serum endostatin at baseline is independently associated with the risk of graft loss in KTRs.

Validation of an enzyme-linked immunosorbent assay (ELISA) for quantification of endostatin levels in mice as a biomarker of developing glomerulonephritis.

Endostatin, the C-terminal fragment of type XVIII collagen, was shown to be one of the most potent endothelial cell-specific inhibitors of angiogenesis. As altered circulating endostatin concentration is associated with impaired kidney function, new tools for measuring endostatin in rodents may be helpful to further investigate and understand its role within kidney disease progression. A novel and commercially available ELISA for the quantification of mouse and rat endostatin was developed and validated according to international quality guidelines including the parameters specificity, robustness, accuracy, dilution linearity, precision, limit of detection (LOD) and lower limit of quantification (LLOQ). Endostatin and blood urea nitrogen (BUN) concentration were measured in mice with a glomerulonephritis phenotype. The validation revealed that within the range of 0.5–32 nmol/L the immunoassay is robust and highly specific for the measurement of rodent endostatin with high sensitivity (LOD 0.24 nmol/L, LLOQ 0.5 nmol/L) and good reproducibility (intra- and inter-assay CV <10%). Also accuracy and dilution linearity were within the range of acceptance. BCL2 transgenic and ETV6/RUNX1;BCL2 double transgenic mice develop a glomerulonephritis phenotype over time, which was displayed by staining of kidney sections. Even before full manifestation of disease serum endostatin concentration rises significantly, whereas BUN levels just slightly increase. This newly developed and commercially available ELISA provides a reliable and accurate tool for the quantification of mouse and rat endostatin and may give new perspectives in the investigation of the role of endostatin as an important and early biomarker for reduced kidney function. Measurement of endostatin concentration is recommended to be used as a superior biomarker for chronic kidney disease compared to BUN.

Serum Endostatin Levels in Oral Squamous Cell Carcinoma.

Endostatin is a C-terminal proteolytic fragment of collagen XVIII and, as with angiostatin and thrombospondin, is known as an antiangiogenic agent. The aim of this study was to assess the level of serum endostatin in patients with oral squamous cell carcinoma (SCC), and its association with the clinicopathological characteristics of the tumor. Using an enzyme-linked immunosorbent assay (ELISA) kit, we investigated the circulating levels of endostatin in the blood serum of 45 patients with oral SCC and 45 healthy controls. The mean level of serum endostatin in patients was significantly lower (68.8±85 ng/ml) than in healthy controls (175.6±73 ng/ml) (P<0.001). Serum endostatin levels were significantly lower in patients with lymph node metastasis compared with patients without lymph node metastasis (P<0.001). In addition, serum endostatin level was associated with higher histological grade (P<0.001). There were no apparent correlations between serum endostatin concentration and clinicopathological features such as age, gender, and tumor stage (P>0.05). Findings of the present study suggest the prognostic and anti-metastatic role of endostatin, and this may be used as a tool for monitoring tumor progression.

Serum Endostatin Concentrations Are Higher in Men with Symptoms of Intermittent Claudication

Objectives. A cleavage fragment of collagen XVIII, endostatin, is released into the circulation and has been demonstrated to have antiangiogenic effects in animal models. We hypothesized that circulating endostatin would be increased in patients with symptoms of lower limb peripheral artery disease. Design. Cross-sectional study. Participants. Community dwelling older men. Measurements. Intermittent claudication was defined using the Edinburgh Claudication Questionnaire (ECQ). Serum endostatin was measured by a commercial ELISA. The association of serum endostatin with intermittent claudication was examined using logistic regression adjusting for age, diabetes, hypertension, dyslipidemia, coronary heart disease, and stroke. Results. Serum endostatin was measured in 1114 men who completed the ECQ. 106 men had intermittent claudication, 291 had atypical pain, and 717 had no lower limb pain. Mean (±standard deviation) serum endostatin concentrations (ng/mL) were 145.22 ± 106.93 for men with intermittent claudication, 129.11 ± 79.80 for men with atypical pain, and 116.34 ± 66.57 for men with no lower limb pain; P < 0.001. A 70 ng/mL increase in endostatin was associated with a 1.17-fold rise in the adjusted odds of having intermittent claudication (OR 1.17, 95% confidence interval 1.00–1.37, and P = 0.050). Conclusions. Serum endostatin is raised in older men who have symptoms of intermittent claudication. The role of endostatin in the genesis and outcome of peripheral artery disease requires further investigation.

Association of endostatin with mortality in patients with chronic heart failure

Experimental data imply that in decompensated heart failure (HF), the anti-angiogenic factor endostatin is increased. This study aimed to investigate whether the angiogenesis inhibitor endostatin is related to the risk of all-cause mortality in a prospective cohort study of chronic HF patients. In this prospective observational cohort study, endostatin serum concentrations were determined in patients with chronic HF. Mortality data were recorded during a median follow-up of 31months. One fifty one patients were included. The overall mortality rate was 20%. Baseline endostatin concentrations >245ng/mL were associated with higher risk of all-cause mortality [HR 8·7 (95% CI 2·5-30·0); P=0·001] in the multivariate analysis as compared to endostatin concentrations ≤245ng/mL. When both endostatin and NT-proBNP were above the calculated cut-off of 245ng/mL and 2386pg/mL, respectively, the prognostic utility of both biomarkers increased [HR 40·8 (95% CI 4·7-354·6); P=0·001] compared with values lower than the cut-offs. Serum endostatin concentrations are independently associated with all-cause mortality. Furthermore, combination of endostatin and NT-proBNP discriminates patients at high risk.

Endostatina sérica en preeclampsia y eclampsia

ObjectiveTo compare serum endostatin concentrations in eclamptic, pre-eclamptic and normotensive pregnant women. Materials and methodThe study included 30 patients with mild preeclampsia (group A), 30 patients with severe pre-eclampsia (group B), and 30 patients with eclampsia (group C). A control group, consisting of 30 healthy pregnant women of similar age and body mass index to the studiy groups, was selected (group D). Only nuliparous patients were included. Blood samples were collected for serum endostatin determination from all patients before delivery, and from the study groups immediately after diagnosis. ResultsHigher values of endostatin were observed in eclamptic patients together with severe pre-eclamptic patients. Lower values were found in mild pre-eclamptic patients. The study groups had significantly higher values of endostatin compared with the control group (P<.05). Linear regression analysis, found that factors that significantly affected plasma endostatin concentrations were uric acid and 24-hour proteinuria. ConclusionThe findings of this study showed that eclamptic and pre-eclamptic patients had higher serum endostatin concentrations than normotensive pregnant women.

Serum Angiogenic Factors in Patients with Neuroendocrine Tumors of Abdominal Organs

The initial (before treatment) levels of VEGF, endostatin, and tumor necrosis factor-beta (TNF-beta) were measured in the sera of 20 patients with malignant and benign neuroendocrine tumors of the abdominal organs and 25 healthy controls. The initial levels of VEGF, endostatin, and TNF-beta in the total group of patients with neuroendocrine tumors of abdominal organs did not differ from the control. A significant difference was detected between the mean serum concentrations of endostatin in patients with benign and malignant neuroendocrine tumors: 64.1+/-14.7 and 107.8+/-14.1 ng/ml, respectively (p=0.043). The content of VEGF, endostatin, and TNF-beta did not correlate with patients' gender and age. A direct correlation between endostatin, TNF-beta concentrations and maximum size of the primary tumor was detected in patients with malignant neuroendocrine tumors. Direct correlations between the initial levels of VEGF and endostatin and an inverse correlation between VEGF and TNF-beta concentrations were detected in patients with benign neuroendocrine tumors. Relapse-free survival was significantly lower in patients with serum endostatin concentration >100 ng/ml and TNF-beta<30 pg/ml.

Short-term induction of thrombocytopenia delays periodontal healing in rats with periodontal disease: participation of endostatin and vascular endothelial growth factor

Platelets contain factors, including VEGF and endostatin, that can modulate the healing process. We evaluated the effects of severe thrombocytopenia on periodontal healing in rats and determined the contribution of VEGF and endostatin to the healing process. Rats were distributed into three test groups and two control groups. Cotton ligatures were placed at the gingival margin level of the lower first molar in the test groups. Sham-operated rats and rats in one of the periodontitis groups were killed 15 days later. Rats in the remaining two periodontitis groups had the ligatures removed in order to study the spontaneous recovery from the periodontal disease 15 days later, and these rats were treated with rabbit antiplatelet serum, in order to induce thrombocytopenia, or normal rabbit serum. An additional group without ligatures received antiplatet serum in the same period. After ligature removal, rats treated with normal rabbit serum showed reduced myeloperoxidase activity, decreased alveolar bone loss and increased numbers of blood vessels. Thrombocytopenia caused a delay in alveolar bone regeneration, a decrease in the number of vessels and a modest decrease in myeloperoxidase activity. In the rats with periodontitis, serum endostatin concentrations were slightly decreased and serum VEGF remained unchanged compared with sham-operated animals. After ligature removal, a significant VEGF increase and endostatin decrease were observed in the rats treated with normal rabbit serum. Thrombocytopenia led to a dramatic fall in both VEGF and endostatin concentrations. Thrombocytopenia leads to a delay of periodontal healing in the situation of experimental periodontitis, which might be mediated in part by a decrease in the serum concentration of VEGF and endostatin derived from the platelets. However, other factors derived from the platelets may also have contributed to a delay of periodontal healing in the rats with thrombocytopenia.

Maternal serum endostatin at gestational weeks 16–20 is elevated in subsequent pre‐eclampsia but not in intrauterine growth retardation

Endostatin, an important anti-angiogenic factor produced by endothelial cells, is elevated in established pre-eclampsia. We measured maternal serum endostatin concentrations in early pregnancy associated with later pre-eclampsia and intrauterine growth retardation (IUGR). Retrospective case-control study. University Central Hospital. Serum samples were collected at 12-15 and 16-20 gestational weeks from a total of 124 pregnant women of whom 49 developed pre-eclampsia, 16 gave birth to infants with IUGR without pre-eclampsia, and 59 remained normotensive giving birth to healthy, normal-weight infants. Enzyme-linked immunosorbent assay. Endostatin concentrations in serum. At 12-15 gestational weeks, there was no difference in median endostatin concentrations between the groups. At 16-20 gestational weeks, the median endostatin concentration was higher in the women with subsequent pre-eclampsia (p=0.026), especially preceding a later severe form of the disease (p=0.041), than in the controls. The results were further confirmed by receiver operating characteristic (ROC) analysis showing an area under the curve (AUC) of 0.64 (95% confidence interval: 0.50-0.81) for endostatin to identify subsequent pre-eclampsia, and 0.71 (0.53-0.89) in cases of severe pre-eclampsia. Optimal cut-off values were determined and used for calculations of sensitivity and specificity, which were 80 and 52% (cut-off value = 58.0 microg/L) in pre-eclampsia, and 80 and 65% (cut-off value = 65.5 microg/L) in the severe form of the disease. The concentrations of endostatin in maternal serum at 16-20 weeks' of gestation are associated with an increased risk of pre-eclampsia but not IUGR.

Tamoxifen and Aromatase Inhibitors Differentially Affect Vascular Endothelial Growth Factor and Endostatin Levels in Women with Breast Cancer

Circulating and cellular proangiogenic and antiangiogenic proteins such as vascular endothelial growth factor (VEGF) and endostatin contribute to the local angiogenic balance. We explored the effects of tamoxifen and aromatase inhibitors on concentrations of VEGF and endostatin in plasma, serum, and platelet releasate (induced by platelet activation). VEGF and endostatin concentrations were measured with a quantitative immunoassay before and after 1 to 5 weeks of treatment in 30 women with breast cancer treated with either tamoxifen (n = 14) or aromatase inhibitors (n = 16). Platelet activation was induced by a thrombin receptor agonist. Tamoxifen therapy resulted in an increase in platelet releasate concentrations of VEGF (P = 0.01) but no change in plasma VEGF. In contrast, aromatase inhibitor therapy did not affect serum, plasma, or platelet releasate VEGF. In univariate analysis, aspirin use attenuated the tamoxifen-associated increase in VEGF in the platelet releasate and decreased serum levels of VEGF (P = 0.03). Aromatase inhibitor therapy resulted in a decrease in serum endostatin concentrations (P = 0.04), whereas plasma concentrations of endostatin tended to be higher during treatment with aromatase inhibitors (P = 0.06). Tamoxifen therapy resulted in no change in serum or plasma endostatin concentrations. Platelet releasate concentrations of endostatin did not change with either treatment. Interindividual variability was noted among both aromatase inhibitor--and tamoxifen-treated patients. Tamoxifen and aromatase inhibitor therapy affect VEGF and endostatin levels and likely contribute to the angiogenic balance in breast cancer patients. Aspirin decreased the proangiogenic effects of tamoxifen, suggesting that antiplatelet and/or antiangiogenic therapy might improve the effectiveness of tamoxifen in women with breast cancer.

Endostatin and Vascular Endothelial Growth Factor Concentrations in Healthy Dogs, Dogs with Selected Neoplasia, and Dogs with Nonneoplastic Diseases

To evaluate the relationship between endostatin and vascular endothelial growth factor (VEGF) in cancers of dogs, circulating concentrations of these 2 tumor‐associated markers were measured prospectively in healthy dogs (n = 44), dogs with tumors (n = 54), and dogs with nonneoplastic diseases (n = 42 for endostatin; n = 16 for VEGF). A canine‐directed enzyme‐linked immunosorbent assay kit was used for determination of endostatin, and a human‐directed kit was validated for detection of canine VEGF. Concentrations of endostatin for all dogs were 28–408 ng/mL. Increasing serum endostatin concentration was associated with increasing age (P= .0396). Concentrations of endostatin were not different among groups of dogs (P= .1989) when adjusted for age. Mean endostatin concentrations for all dogs were higher in dogs (P= .0124) with detectable VEGF concentrations. Endostatin concentrations, when corrected for age, were related to decreasing PCV (P= .032) but not white blood cell count (P= .225) or platelet count (P= .1990). Measurable VEGF (≥2.5 pg/mL) was detected in 3 (7.0%) of 43 healthy dogs. Dogs with tumors had detectable VEGF in 24 (44%) of 54 dogs, with concentrations ranging from 2.5–274 pg/mL; only 1 dog with a nonneoplastic disease process had detectable VEGF. VEGF concentrations for all dogs after correcting for age, endostatin, and disease categories were associated with increased white blood cell count (P= .0032) and platelet counts (P= .0064) and decreased PCV (P= .0017). Linkage between increased endostatin and VEGF concentrations suggests that similar factors may influence concentrations of these markers. Further evaluation of endostatin and VEGF associations in dogs with tumors may provide information on the extent and progression of the disease.

Endostatin and Vascular Endothelial Growth Factor Concentrations in Healthy Dogs, Dogs with Selected Neoplasia, and Dogs with Nonneoplastic Diseases

To evaluate the relationship between endostatin and vascular endothelial growth factor (VEGF) in cancers of dogs, circulating concentrations of these 2 tumor-associated markers were measured prospectively in healthy dogs (n = 44), dogs with tumors (n = 54), and dogs with nonneoplastic diseases (n = 42 for endostatin; n = 16 for VEGF). A canine-directed enzyme-linked immunosorbent assay kit was used for determination of endostatin, and a human-directed kit was validated for detection of canine VEGF. Concentrations of endostatin for all dogs were 28-408 ng/mL. Increasing serum endostatin concentration was associated with increasing age (P = .0396). Concentrations of endostatin were not different among groups of dogs (P = .1989) when adjusted for age. Mean endostatin concentrations for all dogs were higher in dogs (P = .0124) with detectable VEGF concentrations. Endostatin concentrations, when corrected for age, were related to decreasing PCV (P = .032) but not white blood cell count (P = .225) or platelet count (P = .1990). Measurable VEGF (> or = 2.5 pg/mL) was detected in 3 (7.0%) of 43 healthy dogs. Dogs with tumors had detectable VEGF in 24 (44%) of 54 dogs, with concentrations ranging from 2.5-274 pg/mL; only 1 dog with a nonneoplastic disease process had detectable VEGF. VEGF concentrations for all dogs after correcting for age, endostatin, and disease categories were associated with increased white blood cell count (P = .0032) and platelet counts (P = .0064) and decreased PCV (P = .0017). Linkage between increased endostatin and VEGF concentrations suggests that similar factors may influence concentrations of these markers. Further evaluation of endostatin and VEGF associations in dogs with tumors may provide information on the extent and progression of the disease.

Recombinant human endostatin administered as a 28-day continuous intravenous infusion, followed by daily subcutaneous injections: a phase I and pharmacokinetic study in patients with advanced cancer

Endostatin is an endogenous collagen XVIII-fragment with anti-angiogenic properties and remarkable antitumor activity in mice. Preclinical data suggest that continuous low dose administration of endostatin is much more potent than intermittent dosing. The feasibility of this approach is tested in a phase I study. We determined the safety and pharmacokinetic profile of 4-week continuous intravenous infusion of recombinant human (rh)-endostatin, followed after an interval of 1 week by twice daily subcutaneous injections in patients with advanced cancer. Thirty-two patients received rh-endostatin in six dosing cohorts, ranging from 3.75 mg/m(2)/day to 120 mg/m(2)/day. Serum endostatin pharmacokinetics, toxicity and antitumor response were determined. A total of 160 cycles were delivered without significant toxicities. Pharmacokinetic analysis showed a linear increase of steady-state serum endostatin concentrations with dose (i.v. r(2)=0.96; s.c. r(2)=0.99) reaching 300--1,000 ng/ml for the two highest doses, with considerable interpatient variation. The main pharmacokinetic values for both routes of administration were similar. The apparent steady-state concentration and AUC reached at 60--120 mg/m(2)/day were within the range expected to induce anti-angiogenic and antitumor effects based on preclinical tumor models. Although no objective responses were observed, two patients had long-lasting stable disease (defined as a tumor increase<100%). rh-endostatin was safely administered both by continuous infusion and by twice daily subcutaneous injections up to 120 mg/m(2)/day. Predictable pK was seen in this dose range and the target endostatin levels were reached from 60 mg/m(2)/day and above.

Serum endostatin levels are elevated and correlate with serum vascular endothelial growth factor levels in patients with pituitary adenomas

Endostatin, a cleaved fragment of collagen XVIII, is a potent endogenous angiogenesis inhibitor. Elevated serum endostatin levels have been recently reported in patients with various types of neoplasms. The purpose of our study was to evaluate serum concentrations of endostatin in patients harbouring various pituitary adenoma types and to examine the relationship of serum endostatin levels to circulating vascular endothelial growth factor (VEGF) levels. Preoperative serum endostatin and VEGF concentrations were measured using competitive enzyme immunoassays in 71 patients with pituitary adenomas (20 somatotropinomas, 3 corticotropinomas, 6 prolactinomas and 42 clinically nonfunctioning pituitary adenomas - CNFPAs) and compared with levels from age-matched controls. In 35 patients postoperative immunohistochemical investigations were performed. Serum endostatin concentrations were significantly higher in all pituitary adenoma types, except for prolactinomas (somatotropinomas: 124 +/- 16; p < 0.02, corticotropinomas: 157 +/- 42; p < 0.02, prolactinomas: 141 +/- 37; p > 0.05, CNFPAs: 169 +/- 11 ng/ml; p < 0.000005 vs 73 +/- 10 ng/ml in controls). There was a significant positive correlation between endostatin and VEGF serum levels in patients with pituitary adenomas (r = +0.322; p = 0.006). In the control group a significant negative correlation xbetween circulating endostatin and VEGF was found (r = -0.653; p = 0.00975). The simultaneous elevation of endostatin and VEGF may attenuate the pro-angiogenic action of VEGF and be responsible for rather weak neovascularization of pituitary adenomas. Prospective studies are required to assess the usefulness of circulating endostatin and VEGF as markers of progression or recurrence of pituitary tumors.

Endostatin Concentrations in Healthy Dogs and Dogs with Selected Neoplasms

Endostatin prevents angiogenesis and tumor growth by inhibiting endothelial cell proliferation and migration. The purpose of this study was to determine serum endostatin concentrations in 53 healthy dogs and in 38 dogs with confirmed malignant neoplasms. Endostatin concentration was determined with a competitive enzymatic immunoassay (EIA) with rabbit polyclonal antibody generated against a recombinant canine endostatin protein. Both the presence of cancer and increasing age were associated with increased serum concentration of endostatin. Endostatin concentration in healthy dogs was 87.7 ± 3.5 ng/mL. Upper and lower limits of the reference range for serum endostatin concentration in healthy dogs were 60 and 113 ng/mL. Dogs with lymphoma (LSA) and hemangiosarcoma (HSA) had endostatin concentrations of 107 ± 9.3 ng/mL. In conclusion, this study demonstrates that endostatin can be quantified in dogs and that endostatin concentrations are high in dogs with HSA and LSA.

Endostatin concentrations in healthy dogs and dogs with selected neoplasms.

Endostatin prevents angiogenesis and tumor growth by inhibiting endothelial cell proliferation and migration. The purpose of this study was to determine serum endostatin concentrations in 53 healthy dogs and in 38 dogs with confirmed malignant neoplasms. Endostatin concentration was determined with a competitive enzymatic immunoassay (EIA) with rabbit polyclonal antibody generated against a recombinant canine endostatin protein. Both the presence of cancer and increasing age were associated with increased serum concentration of endostatin. Endostatin concentration in healthy dogs was 87.7 +/- 3.5 ng/mL. Upper and lower limits of the reference range for serum endostatin concentration in healthy dogs were 60 and 113 ng/mL. Dogs with lymphoma (LSA) and hemangiosarcoma (HSA) had endostatin concentrations of 107 +/- 9.3 ng/mL. In conclusion, this study demonstrates that endostatin can be quantified in dogs and that endostatin concentrations are high in dogs with HSA and LSA.

Evaluation of endostatin antiangiogenesis gene therapy in vitro and in vivo.

Progressive growth and metastasis of solid tumors require angiogenesis, or the formation of new blood vessels. Endostatin is a 20-kDa carboxy-terminal fragment of collagen XVIII that has been shown to inhibit endothelial cell proliferation and tumor angiogenesis. Replication-deficient recombinant adenovirus (rAd) vectors were constructed, which encoded secreted forms of human and mouse endostatin (HECB and MECB, respectively), and, as a control, human alkaline phosphatase (APCB). Accumulation of endostatin was demonstrated in supernatants of cultured cells infected with the endostatin rAds. These supernatants disrupted tubule formation, inhibited migration and proliferation, and induced apoptosis in human dermal vascular endothelial cells or human vascular endothelial cells. Endostatin-containing supernatants had no effect on the proliferation of MidT2-1 mouse mammary tumor cells in vitro. A pharmacokinetic study of MECB in immunocompetent FVB mice demonstrated a 10-fold increase of serum endostatin concentrations 3 days after intravenous administration of 1x10(10) particles of this rAd (215-257 ng/mL compared to 12-38 ng/mL in control rAd-treated mice). Intravenous administration of MECB reduced b-FGF stimulated angiogenesis into Matrigel plugs by 38%. Intratumoral MECB inhibited growth of MidT2-1 syngeneic mammary tumors in FVB mice, but had minimal impact on the growth of MDA-MB-231 human breast tumors in SCID mice. Intravenous therapy with MECB also initially inhibited growth of MidT2-1 tumors, but this activity was subsequently blocked by induced anti-rAd antibodies. In summary, endostatin gene therapy effectively suppressed angiogenic processes in vitro and in vivo in several model systems.

The angiogenesis inhibitor, endostatin, does not affect murine cutaneous wound healing.

Endostatin is a potent angiogenesis inhibitor, which is currently being used in Phase I trials as an antitumor agent. The purpose of this study was to determine whether endostatin has an effect on wound healing in a murine model. The function of endostatin was confirmed using a human microvascular endothelial cell (HMVEC) proliferation assay in which cells are treated for 4 days with growth media plus or minus endostatin. Full-thickness incisions were made on the dorsum of athymic nude mice and closed primarily with skin staples. PVA sponges were implanted in some wounds to determine vascular ingrowth. Subsequently, mice were treated with recombinant human endostatin at 20 mg/kg/day or 50 mg/kg/dose BID versus control for a total of 14 days. On Days 2, 4, 8, 12, and 16, three mice per group had serum samples drawn and were sacrificed. Perpendicular breaking strength (N) was determined using an Instron 5540 tensometer. Wound strength was determined by dividing breaking strength by wound area (N/cm(2)). Vascular density in sponges was determined using CD31 immunohistochemistry. Serum endostatin concentrations were determined using a commercially available ELISA kit. Endostatin caused a significant reduction of endothelial cell proliferation after 4 days compared to media alone (72%, P = 0.031). At all time points tested, there was no statistical difference in the wound-breaking strength between endostatin and control-treated mice at either the low or high dose. Serum endostatin levels were consistently 10-fold higher in endostatin-treated mice than in controls. No differences in vascular density were seen in endostatin versus control-treated mice as determined by CD31 immunohistochemistry of PVA sponges. Therapy with human endostatin does not induce a significant decrease in breaking strength of cutaneous wounds in mice.