Section Review Oncologic, Endocrine & Metabolic: Angiogenesis inhibition as a drug target for disease: an update

Anti-angiogenic therapies in cancer clinical trials

Strategies involving vasculature have widely been acknowledged to have therapeutic potential in the management of cancer and other diseases. Based on a large body of evidence from preclinical studies and early clinical trials there is considerable optimism that anti-angiogenesis and vascular targeting will be a major clinical therapy. This review considers some 30 anti-angiogenic and vascular targeting agents that are currently in cancer clinical trials and highlights specific problems relating to the assessment of the activity of these agents in patients, trial design, potential toxicities and resistance mechanisms.

The role of COX-2 inhibitors in lung cancer

BACKGROUND

Human lung cancer is a major cause of death worldwide with few known effective therapeutic modalities. The isoenzyme cyclooxygenase 2 (COX-2) is an inducible inflammatory enzyme with increased activity evidenced in lung carcinoma. The objective was to determine the effect of a selective COX-2 inhibitor on proliferation and apoptosis rates in the Lewis lung (3LL) tumor cell line in vitro.

METHODS

First, 1 x 10(4) 3LL cells were plated in a 96-well plate. Cells were incubated for 24 hours with either a control or increasing doses of rofecoxib (0.1 mmol/L, 0.25 mmol/L, 0.5 mmol/L, 1.0 mmol/L, and 2.5 mmol/L) in complete Dulbecco's Modified Eagle's Medium culture medium. Cell proliferation was measured using BrdU enzyme-linked immunosorbent assay. Next, 1 x 10(6) 3LL cells were similarly treated. Cells were permeabilized, immunostained with propidium iodide and apoptotic rates were measured using flow cytometry. Then, 5 x 10(4) cells were plated on a 24-well plate. Cells were incubated for 24 hours with either control or increasing doses of rofecoxib (0.1 mmol/L, 0.25 mmol/L, 0.5 mmol/L, 1.0 mmol/L, and 2.5 mmol/L) in complete culture medium. Supernatant was collected and lactate dehydrogenase was measured for cell necrosis using a cytotoxicity detection kit.

RESULTS

The selective COX-2 inhibitor rofecoxib resulted in a dose-dependent increase in apoptosis and dose and time-dependent growth inhibition in cell proliferation. However, rofecoxib did not cause cell necrosis.

CONCLUSIONS

There was a significant decrease in proliferation and increase in apoptosis of 3LL tumor cells when treated with the highly selective COX-2 inhibitor rofecoxib. COX-2 inhibitors may have a potential role to play in the treatment of lung carcinoma.

Downregulation of COX-2 and iNOS by amentoflavone and quercetin in A549 human lung adenocarcinoma cell line

Flavonoids are natural polyphenolic compounds ubiquitously present in the plant kingdom. They are reported to exhibit numerous beneficial health effects. In the present study, we demonstrate the potential effects of different flavonoids on cytokines mediated cyclooxygenase-2 and inducible nitric oxide synthase expression and activities in A549 cell line using quercetin, amentoflavone and flavanone. Our data revealed that quercetin, at 50 micro M concentration inhibited PGE(2) biosynthesis by A549 very strongly with little effect on COX-2 mRNA and protein expression. Unlike quercetin, amentoflavone inhibited both PGE(2) biosynthesis and COX-2 mRNA and protein expression strongly. In another set of experiment, quercetin inhibited iNOS protein expression completely without affecting iNOS mRNA expression. In contrast, amentoflavone although exerted no inhibitory effect on iNOS mRNA expression, did inhibit weakly iNOS protein expression. Flavanone had no inhibitory effect on either enzyme at the same concentration. Taken together, our data indicated that amentoflavone and quercetin differentially exerted supression of PGE(2) biosynthesis via downregulation of COX-2/iNOS expression.

Characterization of cyclooxygenase-2 (COX-2) during tumorigenesis in human epithelial cancers: evidence for potential clinical utility of COX-2 inhibitors in epithelial cancers

Increased prostaglandins (PGs) are associated with many inflammatory pathophysiological conditions; and are synthesized from arachidonic acid by either of 2 enzymes, cyclooxygenase-1 (COX-1) or -2 (COX-2). Recent epidemiologic, expression, and pharmacologic studies suggest COX-2 derived metabolites also play a functional role in the maintenance of tumor viability, growth and metastasis. Archival and/or prospectively collected human tissues were prepared for immunohistochemistry, and representative cases assayed via Western blot, RT-PCR, or TAQman analysis. Consistent overexpression of COX-2 was observed in a broad range of premalignant, malignant, and metastatic human epithelial cancers. COX-2 was detected in ca. 85% of the hyperproliferating, dysplastic, and neoplastic epithelial cells, and in the existing and angiogenic vasculature within and adjacent to hyperplastic/neoplastic lesions. These data collectively imply COX-2 may play an important role during premalignant hyperproliferation, as well as the later stages of invasive carcinoma and metastasis in various human epithelial cancers.

Increased expression of cyclooxygenase-2 protein in 4-nitroquinoline-1-oxide-induced rat tongue carcinomas and chemopreventive efficacy of a specific inhibitor, nimesulide

Expression of cyclooxygenase (COX)-2 protein in 4-nitroquinoline-1-oxide (4-NQO)-induced rat tongue lesions and the postinitiation chemopreventive potential of a selective COX-2 inhibitor, nimesulide (NIM), were examined in Fischer 344 male rats. NIM was administered in the diet at doses of 150, 300, and 600 ppm for 14 weeks after treatment with 25-35 ppm 4-NQO in the drinking water for 12 weeks. Western blot analysis revealed COX-2 protein to be barely expressed in the normal tongue epithelia, whereas it was increased approximately 6-fold in squamous cell carcinomas (SCCs). Immunohistochemically, COX-2 protein was diffusely present in SCCs and dysplasia but expressed only in basal cells in hyperplasia and papillomas. In basal cells of normal epithelia, it was also occasionally weakly stained. NIM dose-dependently decreased at doses of 150 and 300 ppm, the incidences of SCCs to 4 of 12 (33.3%) and 1 of 13 (7.7%) and their multiplicity to 0.33+/-0.49 and 0.08+/-0.28 per rat, respectively, as compared with 4-NQO alone group values of 9 of 11 (81.8%) and 1.00+/-0.77. A lesser decrease was observed with 600 ppm, the values being 5 of 12 (41.7%) and 0.50+/-0.67. NIM did not significantly affect the development of hyperplasias, dysplasias, and papillomas. These results clearly indicate chemopreventive potential of a selective COX-2 inhibitor against the postinitiation development of SCCs in rat tongue carcinogenesis.

COX-2 is expressed in human pulmonary, colonic, and mammary tumors

BACKGROUND

The cyclooxygenase (COX) enzyme catalyzes the formation of prostaglandins, which can affect cell proliferation and alter the response of the immune system to malignant cells. The inducible form of COX, COX-2, has been shown to be important in carcinogenesis.

METHODS

The authors studied COX-1 and -2 expression in 20 tumors of the lung, colon, and breast (60 total) by using commercially available monoclonal and polyclonal antibodies on formalin fixed, paraffin embedded tissue. Our evaluation also included seven carcinoma-associated colonic adenomas and 10 mammary ductal carcinomas in situ (DCIS). Quantitation of immunoreactivity was accomplished using an immunohistochemical scoring system that approximates the use of image analysis-based systems.

RESULTS

Ninety percent of lung tumors (squamous cell carcinomas and adenocarcinomas), 71% of colon adenocarcinomas and 56% of breast tumors (DCIS and infiltrating ductal and lobular carcinomas) expressed COX-2 at a moderate to strong level, which was significantly different from the negligible expression in distant nonneoplastic epithelium (controls; P < 0.0001). Poorly differentiated histologic features were correlated with low COX-2 expression overall, especially in colon carcinomas. Among breast carcinomas, DCIS was more likely to express COX-2 than invasive carcinomas. Adenomatous colonic epithelium showed moderate COX-2 expression, as did adjacent nonneoplastic epithelium. COX-1 immunoreactivity was essentially weak to moderate in all tissues evaluated.

CONCLUSIONS

COX-2 expression is upregulated in well and moderately differentiated carcinomas of the lung, colon, and breast whereas COX-1 appears to be constitutively expressed at low levels. A possible COX-2 paracrine effect is suggested by moderate immunoreactivity in adjacent nonneoplastic epithelium.

Effects of an anti-angiogenic agent, TNP-470, on the growth of oral squamous cell carcinomas

Anti-tumor effects of an anti-angiogenic agent, TNP-470, on the growth of oral squamous cell carcinomas (SCCs) were evaluated in vivo and in vitro. The growth of an oral SCC cell line, HSC-2, inoculated subcutaneously in severe combined immuno-deficiency (SCID) mice was inhibited in a dose-dependent manner by the treatment with this agent. A reduction of microvessels surrounding tumor tissues treated with TNP-470 was observed by immunohistochemistry. Significant side-effects were not observed except for weight loss during the period of treatment with high dose (50 mg/kg) of TNP-470. The direct effects of TNP-470 on oral SCC cell lines were also evaluated in culture. The growth of all eight SCC cell lines tested was inhibited by TNP-470, but the sensitivity of the oral SCC cell lines to TNP-470 was about 1700 times less than that of endothelial cells. These results suggest that TNP-470 inhibits the growth of oral SCC by anti-angiogenic activities and that it may be effective as a new therapy of oral cancer.

Potential utility of COX-2 inhibitors in chemoprevention and chemotherapy

Increased prostaglandin (PG) production is associated with many inflammatory pathophysiological conditions; it is derived from arachidonic acid by either of two enzymes: cyclooxygenase-1 or -2 (COX-1 or COX-2). In addition to its role in inflammation, recent work suggests COX-2 derived prostaglandins may play a pivotal part in the maintenance of tumour viability, growth and metastasis. In this review, we summarise the non-steroidal anti-inflammatory drug (NSAID) epidemiological evidence, studies demonstrating overexpression of COX-2 in multiple human tumours and the pharmacological evidence in animal models which also support this hypothesis. We also discuss the potential functional roles of COX-2 activity during tumourigenesis, and speculate on the mechanism by which COX-2 inhibitors may exert their anticancer effects.

P1, P2'-linked macrocyclic amine derivatives as matrix metalloproteinase inhibitors

A novel series of 13- and 14-membered macrocyclic amines was developed by linking the P1 and P2' groups. The synthesis entails stereoselective Frater alkylation to install the anti-succinate configuration and macrocyclic amination via nucleophilic displacement. This strategy resulted in a new class of conformationally constrained inhibitors that are potent and selective for MMP-8 and 9 over MMP-1 and 3.

Nature of interaction between basic fibroblast growth factor and the antiangiogenic drug 7,7-(Carbonyl-bis[imino-N-methyl-4, 2-pyrrolecarbonylimino[N-methyl-4,2-pyrrole]-carbonylimino] )bis-(1, 3-naphthalene disulfonate)

PNU145156E (7,7-(carbonyl-bis[imino-N-methyl-4, 2-pyrrolecarbonylimino[N-methyl-4,2-pyrrole]-carbonylimino]) -bis-(1, 3-naphthalene disulfonate)) is a naphthalene sulfonic distamycin A derivative that interacts with heparin-binding growth factors. Because PNU145156E inhibits tumor angiogenesis, it was selected for clinical development. Picosecond time-resolved fluorescence emission and anisotropy were used to characterize the binding of PNU145156E to the basic fibroblast growth factor (a protein associated with tumor angiogenesis). A decrease in PNU145156E fluorescence lifetime was observed as a function of human basic fibroblast growth factor (bFGF) concentration. Nonlinear least-squares fitting of the binding isotherm yielded Kd = 145 nM for a single class of binding sites. Time-resolved anisotropy gave Kd = 174 nM. Kd = 150 nM was independently verified by quantitative high-performance affinity chromatography. The displaced volume of the complex, calculated from its rotational correlation time, fitted a sphere of 1:1 stoichiometry. These results account for the formation of a tight yet reversible PNU145156E:bFGF complex. An evaluation of PNU145156E fluorescence lifetimes in various solvents has highlighted the forces involved in stabilizing the complex. These are mostly electrostatic-hydrophobic in nature, with a relatively low contribution from hydrogen bonding. Both polar and nonpolar groups are involved on the protein-binding site within a largely hydrophobic cleft. A potential binding trajectory, based on a combination of these results with site-directed chemical modification and known bFGF x-ray structure, is suggested.

Tranilast inhibits the proliferation, chemotaxis and tube formation of human microvascular endothelial cells in vitro and angiogenesis in vivo

1. First developed as an antiallergic drug, tranilast inhibits chemical mediator release from mast cells. In the present study, we examine the effects of tranilast on angiogenesis in vitro and in vivo and discuss the application of tranilast for angiogenic diseases. 2. Tranilast inhibited significantly the proliferation (IC50: 136 microM, 95% confidence limits: 134-137 microM) and vascular endothelium growth factor (VEGF)-induced chemotaxis (IC50: 135 microM, 95% confidence limits: 124-147 microM) of human dermal microvascular endothelial cells (HDMECs) at concentrations greater than 25 micrograms ml-1. No toxicity to HDMECs measuring by LDH release and no inhibitory effects on metalloproteinase (MMP)-2 and MMP-9 activity were observed even at 100 micrograms ml-1 (306 microM). 3. Tube formation of HDMECs cultured on the matrigel as an in vitro angiogenesis model was inhibited by tranilast in a concentration-dependent manner. The IC50 value and 95% confidence limits were 175 microM and 151-204 microM, respectively. 4. In vivo angiogenesis was induced in mice by the subcutaneous injection of matrigel containing 30 ng ml-1 VEGF and 64 micrograms ml-1 heparin. Tranilast was administered orally twice a day for 3 days. Tranilast dose-dependently suppressed angiogenesis in the matrigel and a significant change was observed at a dose of 300 mg kg-1. 5. These results indicate that tranilast is an angiogenesis inhibitor which may be beneficial for the improvement of angiogenic diseases such as proliferative diabetic retinopathy, age-related macular degeneration, tumour invasion and rheumatoid arthritis.