Anti-angiogenic therapies in cancer clinical trials

The Characteristics of Vascular Growth in VX2 Tumor Measured by MRI and Micro-CT

Blood supply is crucial for rapid growth of a malignant tumor; medical imaging can play an important role in evaluating the vascular characterstics of tumors. Magnetic resonance imaging (MRI) and micro-computed tomography (CT) are able to detect tumors and measure blood volumes of microcirculation in tissue. In this study, we used MR imaging and micro-CT to assess the microcirculation in a VX2 tumor model in rabbits. MRI characterization was performed using the intravascular contrast agent Clariscan (NC100150-Injection); micro-CT with Microfil was used to directly depict blood vessels with diameters as low as 17 um in tissue. Relative blood volume fraction (rBVF) in the tumor rim and blood vessel density (rBVD) over the whole tumor was calculated using the two imaging methods. Our study indicates that rBVF is negatively related to the volume of the tumor measured by ultrasound (R = 0.90). rBVF in the tissue of a VX2 tumor measured by MRI in vivo was qualitatively consistent with the rBVD demonstrated by micro-CT in vitro (R = 0.97). The good correlation between the two methods indicates that MRI studies are potentially valuable for assessing characteristics or tumor vascularity and for assessing response to therapy noninvasively.

In vivo inhibition of angiogenesis by sulphamoylated derivatives of 2-methoxyoestradiol

Drugs that inhibit growth of tumours and their blood supply could have considerable therapeutic potential. 2-Methoxyoestradiol-3,17-O,O-bis-sulphamate (2-MeOE2bisMATE) has been shown to inhibit the proliferation of MCF-7 (ER+) breast cancer cells and angiogenesis in vitro. 2-MeOE2bisMATE and its analogue, 17-Cym-2-MeOE2MATE, were investigated for their ability to inhibit in vivo angiogenesis and tumour growth. The mouse Matrigel plug assay for angiogenesis was used to investigate the effect of compounds on neovascularisation and was quantified using a FITC-dextran injection technique. Nude mice bearing tumours derived from MCF-7 cells were used to assess efficacy on tumour growth. Tumour sections were stained for VEGFR-2 and Ki67 to assess tumour angiogenesis and cell proliferation respectively. Matrigel plugs supplemented with basic fibroblast growth factor resulted in increased neovascularisation over 7 days. Oral administration of 2-MeOE2bisMATE for 7 days at 10 or 50 mg kg(-1) significantly reduced neovascularisation to or below control levels respectively. 17-Cym-2-MeOE2MATE at 20 mg kg(-1) was equally effective. 2-MeOE2bisMATE, dosed daily for 21 days, caused a 52% reduction in tumour growth at 5 mg kg(-1) and 38% regression at 20 mg kg(-1). 17-Cym-2-MeOE2MATE (20 mg kg(-1)) reduced tumour growth by 92%. Immunohistochemistry revealed a reduction in angiogenesis and proliferation. Matrigel plug and tumour imaging after FITC-dextran injection indicated that 2-MeOE2bisMATE caused a marked disruption of vasculature. These sulphamoylated oestrogen derivatives have been shown to be potent inhibitors of angiogenesis in vivo. This, together with their ability to inhibit tumour growth, indicates the potential of this new class of drugs for further development for cancer therapy.

Design, Synthesis, and Antiangiogenic Effects of a Series of Potent Novel Fumagillin Analogues

A series of fumagillin analogues containing the C6-substituted cinnamoyl moiety were designed, synthesized, and evaluated for antiangiogenic activity. Among them, 4-hydroxyethoxy-cinnamoyl fumagillol (4a) and 4-hydroxyethoxy-3,5-dimethoxycinnamoyl fumagillol (4d) exhibited more potent anti-proliferation activity in CPAE and HUVEC cells with low cytotoxicity in vitro. These compounds are presently under further pharmacological evaluation studies.

Angiogenic and antiangiogenic gene therapy

Gene therapy is thought to be a promising method for the treatment of various diseases. One gene therapy strategy involves the manipulations on a process of formation of new vessels, commonly defined as angiogenesis. Angiogenic and antiangiogenic gene therapy is a new therapeutic approach to the treatment of cardiovascular and cancer patients, respectively. So far, preclinical and clinical studies are successfully focused mainly on the treatment of coronary artery and peripheral artery diseases. Plasmid vectors are often used in preparations in angiogenic gene therapy trials. The naked plasmid DNA effectively transfects the skeletal muscles or heart and successfully expresses angiogenic genes that are the result of new vessel formation and the improvement of the clinical state of patients. The clinical preliminary data, although very encouraging, need to be well discussed and further study surely continued. It is really possible that further development of molecular biology methods and advances in gene delivery systems will cause therapeutic angiogenesis as well as antiangiogenic methods to become a supplemental or alternative option to the conventional methods of treatment of angiogenic diseases.

Investigation of novel fumagillin analogues as angiogenesis inhibitors

Modification of fumagillin was conducted to develop MetAP-2 inhibitors with desirable pharmacological properties. Replacement of the C4 side chain by benzyloxime preserves the inhibitory activity against MetAP-2 enzyme. Fumagillin analogues containing the C4 benzyloxime moiety were found to be very sensitive to the nature of the C6 substituent on the inhibition activity of HUVEC proliferation. This lack of correlation between MetAP-2 and HUVEC activities might be due to the cellular metabolism of the compounds by epoxide hydrolase, which is present in the cell. Compound (E)-3d, containing ethylpiperazinyl carbamate at C6 position, exhibited antiangiogenic effects similar to TNP-470 on matrigel plug assay and rat corneal micropocket assay.

Concise stereocontrolled routes to fumagillol, fumagillin, and TNP-470

A concise, diastereoselective synthesis of (+/-)-fumagillol (3) and formal, enantioselective syntheses of the potent angiogenesis inhibitors fumagillin (1) and TNP-470 (2) are reported. The origin of asymmetry is a highly diastereoselective Diels-Alder reaction using a diene with a chiral oxazolidinone auxiliary. The stereochemical course of a key conjugate addition reaction is controlled by the cup-shaped architecture of a cis-fused bicyclic enal. Other key steps include a facile hetero-Claisen rearrangement and a site-selective Sharpless epoxidation.

Angiogenic growth factors: autocrine and paracrine regulation of survival in hematologic malignancies

Recent research has focused on the role of angiogenic growth factors and their ability to mediate tumor growth and metastases, both in solid tumors and in hematologic malignancies. The bone marrow microenvironment is the setting for a wealth of complex interactions that include cell-to-cell contacts as well as secretion of and response to soluble factors. Abundant evidence supports the role of basic fibroblast growth factor (bFGF) in contributing to the dysregulation of apoptosis that is the hallmark of chronic lymphocytic leukemia (CLL). In fact, CLL cells themselves express bFGF; intracellular levels of this cytokine correlate with clinical CLL stage. Other stromal factors mediate the inhibition of apoptosis in CLL as well, suggesting that strategies to block the responses of CLL cells to these factors may represent effective therapies. More broadly, the class of agents known as angiogenesis inhibitors may offer important advantages with respect to the treatment of numerous types of malignancies. Currently, a number of clinical trials are under way to evaluate the clinical potential of several different angiogenesis inhibitors in several hematologic neoplasms.

Tumor angiogenesis as a therapeutic target

Angiogenesis - the formation of new blood vessels within a tumor (or many other tissue types) - has become a hotbed of pharmacological research as well as industrial drug discovery. This is the result of the efforts of a generation of scientists elucidating the complex (patho)physiological, biochemical and molecular events accompanying angiogenesis. It is estimated that >300 drug candidates are currently in various stages of testing, and it is, therefore, impossible to capture all of this in a brief review. Therefore, the emphasis here is on relatively advanced projects that are either in preclinical or clinical development, thus neglecting, to a large extent, the many exciting avenues being pursued in both academic and biotechnology laboratories. Although the potential of the approaches described cannot be overestimated, it is also important to note that there is still no drug on the market that achieves clinical benefit based on a selective modulation or inhibition of angiogenesis.

Angiogenesis and lymphangiogenesis in stage 1 germ cell tumours of the testis

OBJECTIVE

To determine whether angiogenesis can be used as an additional prognostic indicator in patients with stage 1 germ cell tumours of the testis.

PATIENTS AND METHODS

Paraffin sections were assessed immunohistochemically from 51 patients with clinical stage 1 germ cell tumours of the testis (28 seminoma, 23 teratoma) treated by orchidectomy and surveillance only. Sections were analysed for microvascular density (MVD), and expression of the angiogenic factors vascular endothelial growth factor (VEGF) and thymidine phosphorylase (TP). In addition, in the seminoma cases the presence of mRNA for the lymphangiogenic factor VEGF-C was examined by in situ hybridization, and its corresponding receptor VEGFR-3 by immunohistochemistry.

RESULTS

Teratoma specimens had a significantly higher mean (range) MVD (85, 26-163; P < 0.01) than both seminoma (37, 16-91) and four normal specimens (26, 18-30). Teratoma specimens also had significantly higher VEGF expression than both seminoma and normal specimens (P < 0.01). Despite these differences between groups, and indeed individual tumours, there was no significant correlation between MVD and VEGF, or between either MVD or VEGF and relapse-free survival. TP expression was significantly greater in tumours than in normal specimens (P < 0.02) but with very little inter-tumour variation. VEGF-C mRNA and VEGFR-3 protein were detected in a third to a half of cases, with expression mostly around endothelial vessels.

CONCLUSIONS

The marked differences between normal testis and tumours implicate angiogenesis in the biology of germ cell tumours of the testis. In addition, the detection of factors involved in lymphangiogenesis in some seminomas, tumours which initially metastasize primarily to lymph nodes, indicate that although not prognostic in this study, further studies are warranted in both these areas in the search for further prognostic indicators and therapeutic targets.

Vascular endothelial growth factor and its correlation with superficial bladder cancer recurrence rates and stage progression

Because of the heterogeneous behavior of superficial bladder cancer, the development of additional simple diagnostic and prognostic tests will be invaluable. The authors have demonstrated significantly elevated levels of urinary VEGF in patients with active bladder cancer. The sensitivity and specificity of urinary VEGF for diagnosing primary or recurrent bladder cancer were superior when compared with the results of cytology, which remains the most widely used noninvasive diagnostic investigation. These results and the authors' previous findings at the mRNA and protein level strongly implicate VEGF in the pathogenesis of bladder cancer recurrence and progression. The potential exists for anti-VEGF strategies in the treatment of, or prophylaxis against, recurrent superficial bladder cancer.