Infarction of tumor vessels by NGR-peptide-directed targeting of tissue factor: experimental results and first-in-man experience.

We induced thrombosis of blood vessels in solid tumors in mice by a fusion protein consisting of the extracellular domain of tissue factor (truncated tissue factor, tTF) and the peptide GNGRAHA, targeting aminopeptidase N (CD13) and the integrin alpha(v)beta(3) (CD51/CD61) on tumor vascular endothelium. The designed fusion protein tTF-NGR retained its thrombogenic activity as demonstrated by coagulation assays. In vivo studies in mice bearing established human adenocarcinoma (A549), melanoma (M21), and fibrosarcoma (HT1080) revealed that systemic administration of tTF-NGR induced partial or complete thrombotic occlusion of tumor vessels as shown by histologic analysis. tTF-NGR, but not untargeted tTF, induced significant tumor growth retardation or regression in all 3 types of solid tumors. Thrombosis induction in tumor vessels by tTF-NGR was also shown by contrast enhanced magnetic resonance imaging (MRI). In the human fibrosarcoma xenograft model, MRI revealed a significant reduction of tumor perfusion by administration of tTF-NGR. Clinical first-in-man application of low dosages of this targeted coagulation factor revealed good tolerability and decreased tumor perfusion as measured by MRI. Targeted thrombosis in the tumor vasculature induced by tTF-NGR may be a promising strategy for the treatment of cancer.

Generation of fusion proteins for selective occlusion of tumor vessels.

Selective activation of blood coagulation in tumor vessels with subsequent thrombosis and tumor infarction is a promising strategy in cancer therapy. To this end, different fusion proteins consisting of the extracellular domain of tissue factor (truncated tissue factor, tTF) were fused to the peptides GRGDSP (abbr. RGD), GNGRAHA (abbr. NGR) or cyclic derivates of these peptides, which selectively target alpha(v)-integrins or aminopeptidase N (CD13), respectively. Rationale for this strategy is the fact that these surface receptors are preferentially expressed on tumor endothelial cells. The tTF constructs were expressed in Escherichia coli BL21 (DE3). The integrity of the fusion proteins was evaluated by SDS-PAGE, immunoblotting and mass spectrometry. The screening process for the activity contained coagulation assays as well as purified receptor binding assays. The fusion proteins which retained their thrombogenic and binding activity were evaluated further. In vivo studies in nude mice bearing established different malignant human tumors revealed that i.v. administration of tTF-RGD or tTF-NGR induced partial or complete thrombotic occlusion of tumor vessels, which was demonstrated by histological analysis. Furthermore, treatment studies showed that the targeted tTF fusion proteins but not untargeted tTF proteins induced significant tumor growth retardation in human adenocarcinoma of the breast in a nude mice model without apparent side effects such as thrombosis in liver, kidney, heart or lung at therapeutic dose levels. Finally, we illustrate the upscaling process of fusion protein fabrication in order to produce the amounts needed for clinical studies. Thus, generation and screening of active fusion proteins, which induce selective thrombosis in the tumor vasculature, may be a promising strategy for the development of new drugs as cancer therapeutics.

Expression of VEGF-C and its receptor VEGFR-3 in the bone marrow of patients with acute myeloid leukaemia.

Vascular endothelial growth factor-C (VEGF-C) has been shown to promote survival and resistance to chemotherapy of AML-cells in vitro. We investigated the expression of VEGF-C/VEGFR-3 in the bone marrow and pretherapeutic plasma levels of VEGF-C in patients with newly diagnosed AML. Expression of VEGF-C/VEGFR-3 was significantly higher in AML patients than in controls, while circulating levels did not differ. However, VEGF-C/VEGFR-3 expression was not able to predict clinical outcome. In conclusion, AML is associated with an increased expression of VEGF-C/VEGFR-3. Although expression levels display no prognostic significance in our study, strategies targeting the VEGF-C/VEGFR-3-pathway might be a promising treatment approach.

Antiangiogenic tumor treatment: early noninvasive monitoring with USPIO-enhanced MR imaging in mice.

PURPOSE: To prospectively investigate steady-state blood volume measurements for early quantitative monitoring of antiangiogenic treatment with ultrasmall superparamagnetic iron oxide (USPIO)-enhanced magnetic resonance (MR) imaging. MATERIALS AND METHODS: The institutional animal care committee approved all experiments. HT-1080 fibrosarcoma-bearing nude mice were injected with a thrombogenic vascular targeting agent (VTA) (11 nude mice, 20 tumors) or saline (12 nude mice, 20 tumors). USPIO-enhanced (SH U 555C) MR imaging was performed after the VTA was administered. USPIO-induced changes in tissue R2* (DeltaR2*) were measured with a T2-weighted dual-echo echo-planar imaging sequence, and the vascular volume fraction (VVF) was calculated. Parametric DeltaR2* maps were analyzed with respect to tumor perfusion patterns. Correlative histologic analysis was performed for grading of tissue thrombosis, and tissue perfusion was quantified with fluorescent microbeads. Unpaired Student t test and Spearman nonparametric correlation coefficient were used for statistical analysis. RESULTS: The DeltaR2* values were significantly (P < .001) reduced shortly after treatment initiation (mean DeltaR2*, 0.017 msec(-1) +/- 0.0014 [standard error] in control animals vs 0.005 msec(-1) +/- 0.0007 in animals that received VTA), which was also reflected by a decrease in the VVF (2.47% +/- 0.18 vs 0.41% +/- 0.48, P < .001). Histologic analysis revealed various degrees of tumor thrombosis after VTA treatment that correlated inversely with the DeltaR2* values (r = -0.83). Moreover, tumor perfusion measurements corroborated the MR results, indicating a significant reduction in tissue perfusion after VTA treatment (mean tissue fluorescence, 570.4 arbitrary units [au] per gram +/- 27 vs 161.7 au/g +/- 17; P < .05). CONCLUSION: USPIO-enhanced MR imaging enables early monitoring of antiangiogenic treatment of tumors.

Vascular endothelial growth factor and its receptor as drug targets in hematological malignancies.

Angiogenesis is defined as formation of new blood vessels from the preexisting vasculature, a process which is essential for malignant tumor growth. While this has been accepted for solid forms of cancer there is now emerging evidence that progression of hematological malignancies also requires the induction of new blood vessels. Vascular endothelial growth factor (VEGF) is known to be an essential regulator of physiological and pathological angiogenesis. Numerous preclinical and clinical studies have validated VEGF as target for antiangiogenesis and anticancer therapy. With regard to hematological malignancies a stimulating effect of VEGF for proliferation, survival and migration of leukemia cells could be demonstrated. Bone marrow of leukemia patients shows an increased microvessel density as well as VEGF expression. Complete remissions in acute myeloid leukemia (AML) have been reported by targeting the receptor tyrosine kinase system of VEGF. While the pathophysiology behind the contribution of VEGF to leukemia progression is not yet completely understood, VEGF and its receptors may provide promising targets not only in solid tumors but also hematological malignancies such as AML.

Assessment of bone marrow angiogenesis in patients with acute myeloid leukemia by using contrast-enhanced MR imaging with clinically approved iron oxides: initial experience.

PURPOSE: To prospectively assess bone marrow (BM) angiogenesis in patients with acute myeloid leukemia (AML) by using iron oxide-enhanced magnetic resonance (MR) imaging. MATERIALS AND METHODS: The study was institutional ethics committee approved. Informed signed consent was obtained from each study participant. The requirement for informed consent for use of data from a reference database was waived. Eleven patients (seven women, four men; mean age, 53 years+/-4.40 [standard deviation]) with an initial diagnosis of AML were enrolled in the study and underwent T2*-weighted two-echo echo-planar MR imaging of the pelvis before and after intravenous injection of a clinically approved iron oxide blood-pool contrast agent. Six healthy control subjects (one woman, five men; mean age, 35 years+/-2.31) were examined with the same MR protocol. The iron oxide-induced change in R2* relaxation rate (DeltaR2*) was calculated, and the vascular volume fraction (VVF) of the BM was derived by dividing the DeltaR2* of the BM by the DeltaR2* of the muscle. Parametric DeltaR2* maps were calculated to visualize vessel distribution. Patients underwent BM biopsy for correlative determination of microvessel density (MVD) and vascular endothelial growth factor (VEGF). Differences in DeltaR2*, VVF, VEGF, and MVD were compared by using the Wilcoxon rank sum test. RESULTS: DeltaR2* maps showed prominent areas of highly vascularized BM in the patients with AML, whereas the control subjects had moderately vascularized BM with homogeneous vessel distribution. Quantitative analysis revealed VVF values to be significantly higher in patients with AML than in control subjects: The mean VVF in the pelvis was 9.18%+/-1.54 for patients versus 3.91%+/-0.61 for control subjects (P=.010). In accordance with MR results, MVD (P=.009) and VEGF expression (P=.017) were significantly elevated in the AML group compared with values in the control group. CONCLUSION: Iron oxide-enhanced MR imaging enables assessment of BM angiogenesis in patients with AML.

Expression of angiopoietins and their receptor Tie2 in the bone marrow of patients with acute myeloid leukemia.

BACKGROUND AND OBJECTIVES: Angiopoietin-1 (Ang-1) and its natural antagonist angiopoietin-2 (Ang-2), both ligands for the receptor tyrosine kinase Tie2, are known to play an essential role in normal and pathological angiogenesis. DESIGN AND METHODS: We investigated the expression of Ang-1, Ang-2 and Tie2 by immunohistochemical analyses in bone marrow biopsies of 64 adult patients with newly diagnosed acute myeloid leukemia (AML) and correlated angiogenic factor expression with clinicopathological variables and long-term survival. RESULTS: Expression of Ang-2 was significantly higher in the bone marrow of AML patients than in 16 control patients. In contrast, the levels of Ang-1 expression in AML patients did not differ from those found in controls. Thus, we observed a reversal of the Ang-1 and Ang-2 expression balance in the neoplastic bone marrow. Furthermore, Tie2 was significantly overexpressed in leukemic blasts. Patients expressing high levels of Ang-2 had significantly longer overall survival than those with low Ang-2 levels (52.7 vs. 14.7 months). Multivariate analysis revealed that karyotype and Ang-2 expression were independent prognostic factors for overall survival (hazard ratio [CI]: 3.06 [1.39-6.70] and 0.31 [0.14-0.69], respectively). INTERPRETATION AND CONCLUSIONS: These data provide evidence that the alteration of angiopoietin balance in favor of Ang-2 may play a critical role in the pathophysiology of AML. Furthermore, high pre-therapeutic levels of Ang-2 in the bone marrow indicate a favorable prognosis in AML patients treated with polychemotherapy, although the mechanism is not yet known.

Inhibition of tumor growth by RGD peptide-directed delivery of truncated tissue factor to the tumor vasculature.

Selective activation of blood coagulation in tumor vessels with subsequent tumor infarction is a promising anticancer strategy. To this end, a fusion protein consisting of the extracellular domain of tissue factor [truncated tissue factor (tTF)] was fused to the peptide GRGDSP selectively targeting alpha(v)-integrins on tumor endothelial cells. tTF-RGD retained its thrombogenic and integrin-binding activity in vitro. In vivo studies in mice bearing human adenocarcinomas (CCL185), melanoma (M21), and fibrosarcoma (HT1080) revealed that i.v. administration of tTF-RGD induced thrombotic occlusion of tumor vessels resulting in tumor growth retardation or regression in all three types of solid tumors. No apparent side effects, such as thrombosis, in other organs or other treatment-related toxicities were observed. Reduced tumor blood flow in tTF-RGD-treated animals as determined by contrast-enhanced magnetic resonance imaging underlines the proposed mechanism. In conclusion, we consider RGD peptide-directed delivery of tTF as alternative to previously used antibody fusion proteins. Small peptide-directed delivery of coaguligands does not cause immunologic side effects and those caused by accumulation in the reticuloendothelial system. This is the first report to describe the induction of selective thrombosis in tumor vessels by RGD peptide-directed delivery of tTF, which may be a promising strategy for the treatment of cancer.

Prognostic relevance of increased angiogenesis in osteosarcoma.

PURPOSE: The purpose of this work was to evaluate the prognostic relevance of microvessel density (MVD) for response to chemotherapy and long-term outcome in osteosarcoma. EXPERIMENTAL DESIGN: Pretherapeutic tumor biopsies of 60 patients with high-grade central osteosarcoma, who were treated according to multimodal neoadjuvant protocols of the German-Austrian-Swiss Cooperative Osteosarcoma Study Group, were evaluated for intratumoral MVD. MVD was correlated with demographic and tumor-related variables, response, and survival. RESULTS: The median intratumoral MVD was 52 microvessels per 0.26-mm2 field area (interquartile range, 31-77 microvessels per 0.26-mm2 field area). At a median follow-up period of 3.5 years, patients with a high (>median) MVD had significantly higher 5- and 10-year overall survival rates (84%) than patients with low (< or =median) MVD (49%; P = 0.0029). Furthermore, increased relapse-free survival for patients with high MVD (P = 0.0064) was observed. In a subgroup analysis of 44 patients with primary high-grade central osteosarcoma of the extremities without primary metastases and good surgical remission, high MVD was associated with 5- and 10-year overall survival rates of 91% compared with 58% for low MVD (P = 0.034). Cox regression analysis revealed that MVD was an independent prognostic factor for survival. A good response to chemotherapy (histologic grading scale of Salzer-Kuntschik) correlated significantly with a high MVD (P = 0.006). CONCLUSIONS: Increased angiogenesis is a prognostic indicator for higher survival and response rates to chemotherapy in patients with osteosarcoma. Thus, measurement of MVD might be useful in decisions selecting patients for future neoadjuvant treatment.

Signal transduction pathways as novel therapy targets in lung cancer.

Cytotoxic therapy for lung-cancer patients has only moderately improved during the last decades. Simultaneously, efforts of intensive research to increase our understanding of the molecular basis of lung cancer have been undertaken. The cancer cell has been characterised by several genetic changes that lead to altered cellular functions. In addition, multiple factors of the cancer-cell environment further affect the tumour cell via various receptors and subsequent signaling pathways. The increased knowledge of cellular signaling offers the opportunity to develop novel substances that target specific pathway molecules. In the current review, some of the most essential receptors and signaling pathways involved in lung cancer will be described. In conjunction, examples of novel target-specific agents that have already found their way into clinical trials will be discussed.

Overexpression of basic fibroblast growth factor and autocrine stimulation in acute myeloid leukemia.

Basic fibroblast growth factor (bFGF) is known to play a critical role in tumorigenesis of solid tumors. The importance of bFGF in hematological malignancies such as acute myeloid leukemia (AML) remains to be elucidated. Therefore, we determined bFGF protein expression by immunohistochemical analyses in bone marrow biopsies of patients with newly diagnosed, untreated AML. The expression of bFGF was significantly increased in AML patients [n = 81; median, 3.0 (interquartile range, 1.8-3.9) arbitrary units (AU)] as compared with controls [n = 18; 1.9 (1.5-2.3) AU]. The degree of bFGF expression did not correlate with microvessel density. bFGF/FGF receptor mRNA and bFGF protein were detected in different AML cell lines. To study autocrine growth stimulation of AML blasts, the AML cell lines HL-60, M-07e, and KG-1 were incubated with bFGF. A significant dose-dependent increase in proliferation and colony formation was observed. These effects were abrogated by the addition of a polyclonal anti-bFGF antibody. In conclusion, increased expression of bFGF in the bone marrow of AML patients seems to play an important role in the pathophysiology of AML by promoting autocrine growth stimulation of leukemic blasts.

Rituximab in combination with platinum-containing chemotherapy in patients with relapsed or primary refractory diffuse large B-cell lymphoma.

The aim of the study was to evaluate the efficacy of a regimen consisting of rituximab and a platinum-containing chemotherapy with either Ifosfamide, Carboplatin and Etoposide (ICE) or Cisplatin, high-dose Ara-C and Dexamethasone (DHAP) in patients with relapsed or primary refractory diffuse large B-cell lymphoma. Ten patients with relapsed or primary refractory diffuse large B-cell lymphoma were treated from June 2000 until May 2001 with a platinum-containing chemotherapy regimen according to the ICE- or DHAP-protocol in combination with rituximab at the University of Muenster. Two cycles of ICE or DHAP and rituximab were given. In case of at least a minor response after 2 cycles, 2 additional cycles of the same combination were applied. Response rate, remission duration and duration of survival were evaluated. All 10 patients could be analysed with respect to these endpoints. No treatment related mortality was observed. The response rate (CR/PR) was 60% (10/50%). Twenty percent of the patients had progressive disease. The median duration of remission and survival was 3 and 3.5 months, respectively (range: 1-6 and 1-7 months, respectively), the survival rate was 10%. Eight of 10 patients died because of their underlying disease with short remission duration, 1 patient died of complications of allogeneic transplantation in CR. In conclusion, the combination of platinum-containing chemotherapy (ICE or DHAP) with rituximab demonstrates significant activity in intensively pretreated patients with relapsed or primary refractory diffuse large B-cell lymphoma. Considering the short duration of remission and survival, respectively, other experimental therapeutic approaches (e.g. allogeneic stem cell transplantation, radioimmunotherapy) should be pursued following this treatment in order to induce long-term remission.

Phase I study of liposomal daunorubicin in relapsed and refractory acute myeloid leukemia.

Daunorubicin (DNR) is one of the most important cytotoxic agents in the treatment of acute myeloid leukemia (AML). Its use is usually limited by drug-induced cardiotoxicity depending on the cumulative dose administered. Liposomal encapsulation of DNR (DaunoXome, DNX) seems to reduce the risk of this severe side effect. To investigate the toxicity of DNX in heavily pretreated patients, we conducted a phase I trial, including patients (pts) older than 60 years with relapsed or refractory AML. DNX was used at doses of 40, 60, 75 and 90 mg/m(2), biweekly. Fourteen patients with a median age of 69 years (range, 63-77) were enrolled. A total of 49 courses of DNX were administered [3 pts at 40 mg/m(2) (for a total of 13 courses), 5 at 60 mg/m(2) (20 courses), 4 at 75 mg/m(2) (12 courses), and 2 at 90 mg/m(2) (4 courses)]. The mean cumulative dose of DNX administered was 340 mg (range, 120-1200). A 20% decline in the left ventricular ejection fraction (LVEF) without clinical signs and symptoms of heart failure was noted in 2 patients after a cumulative DNX dose of 480 mg, both with pre-existing heart disease. Even at the highest cumulative doses of DNX, no further decline in LVEF was noted. Nausea, vomiting, alopecia and mucositis were absent. All patients had significant myelosuppression requiring transfusion support. During treatment, 3 patients showed a 25% reduction of leukemic blasts in the bone marrow, 3 patients had to be excluded due to AML progression after the 2nd DNX course, and 7 patients died during the first 6 weeks of treatment. We conclude from these data that DNX offers a less toxic alternative to DNR and other anthracyclines. Using DNX dosages of 40 to 90 mg/m(2) biweekly seems to have little anti-leukemic activity in a patient population heavily pretreated with anthracyclines.

The catalytic domain of endogenous urokinase-type plasminogen activator is required for the mitogenic activity of platelet-derived and basic fibroblast growth factors in human vascular smooth muscle cells.

Emerging data suggest that urokinase-type plasminogen activator (UPA), beyond its role in pericellular proteolysis, may also act as a mitogen. We investigated the function of endogenous UPA in mediating the mitogenic effects of platelet-derived growth factor (PDGF) and basic fibroblast growth factor (bFGF) on human vascular smooth muscle cells (SMC). Growth-arrested SMC constitutively expressed UPA, but UPA expression and secretion increased several times upon stimulation with either PDGF or bFGF. Inhibition of endogenous UPA with a polyclonal antibody significantly reduced DNA synthesis and proliferation of PDGF or bFGF stimulated SMC, this effect already being evident when the cells entered S-phase. The proliferative activity of endogenous UPA was dependent on a functional catalytic domain as demonstrated by inhibition experiments with a specific monoclonal antibody (394OA) and p-aminobenzamidine, respectively. In contrast, neither plasmin generation nor binding of UPA to its receptor (CD87) were required for UPA-mediated mitogenic effects. The results demonstrate that endogenous UPA is not only overexpressed in SMC upon stimulation with PDGF/bFGF, but also mediates the mitogenic activity of the growth factors in a catalytic-domain-dependent manner. Specific inhibition of this UPA domain may represent an attractive target for pharmacological interventions in atherogenesis and restenosis after angioplasty.

Efficacy and safety of thalidomide in patients with acute myeloid leukemia.

Emerging data suggest an involvement of angiogenesis in the pathophysiology of acute myeloid leukemia (AML). Thus, antiangiogenic therapy could constitute a novel strategy for the treatment of AML. To test this hypothesis, a phase I/II dose-escalating trial was performed to study the safety and efficacy of thalidomide, a putative inhibitor of angiogenesis, in 20 patients with AML. Thirteen patients were assessable for both toxicity and response, tolerating a maximum dose of 200 to 400 mg daily for at least 1 month. Seven patients had to be prematurely withdrawn from drug administration owing to progressive disease and death (3 patients), personal decision (2 patients), or inability to tolerate thalidomide (2 patients). Overall, adverse events were fatigue, constipation, rash, and neuropathy (grade 1 to 2 in most patients). In 4 patients, a partial response, defined as reduction of at least 50% in the blast cell infiltration of the bone marrow accompanied by increases in platelet counts and hemoglobin values, was observed. One additional patient showed a hematologic improvement without fulfilling the criteria of a partial response. The responses lasted a median of 3 months (range, 1-8 months). In parallel, microvessel densities significantly decreased in these 5 patients during treatment with thalidomide (P <.05). This decrease was accompanied by declining plasma levels of basic fibroblast growth factor, one of the most potent angiogenic growth factors. In conclusion, single-agent thalidomide has antiangiogenic and antileukemic activity in AML, although a causal relationship between both effects has still to be proven.