Vascular endothelial growth factor D expression is a potential biomarker of bevacizumab benefit in colorectal cancer.

BACKGROUND: Bevacizumab prolongs progression-free survival (PFS) in patients with metastatic colorectal cancer. We analysed the protein expression levels of vascular endothelial growth factor (VEGF) ligands and receptors to determine their prognostic and predictive effects. METHODS: We graded expression of VEGF-A, VEGF-B, VEGF-C, VEGF-D, VEGF-R1, and VEGF-R2 to assess whether overexpression predicted bevacizumab resistance in samples from 268 of 471 patients randomised to capecitabine (C), capecitabine and bevacizumab (CB), or CB and mitomycin (CBM) in the MAX trial and extended the analysis to the CAIRO-2 population. RESULTS: Patients with low expression of VEGF-D (0, 1þ) benefited from bevacizumab treatment (PFS hazard ratio (HR) (C vs CBþCBM), 0.21; 95% CI, 0.08­0.55; overall survival (OS) HR, 0.35; 95% CI, 0.13­0.90). Patients with higher VEGF-D expression received less benefit (VEGF-D 2þ PFS HR, 0.67; 95% CI, 0.45­1.00; OS HR, 0.82; 95% CI, 0.52­1.30; VEGF-D 3þ PFS HR, 0.77; 95% CI, 0.50­1.17; OS HR, 1.28; 95% CI, 0.79­2.09) (P interaction o0.05). In CAIRO-2, there was no difference in PFS or OS according to VEGF-D expression. CONCLUSIONS: The predictive value of VEGF-D expression for bevacizumab may depend on the chemotherapy backbone used. Further evaluation is required before clinical utilisation.

Specific targeting, biodistribution, and lack of immunogenicity of chimeric anti-GD3 monoclonal antibody KM871 in patients with metastatic melanoma: results of a phase I trial.

PURPOSE: KM871 is a chimeric monoclonal antibody against the ganglioside antigen GD3, which is highly expressed on melanoma cells. We conducted an open-label, dose escalation phase I trial of KM871 in patients with metastatic melanoma. PATIENTS AND METHODS: Seventeen patients were entered onto one of five dose levels (1, 5, 10, 20, and 40 mg/m2). Patients received three infusions of KM871 at 2-week intervals, with the first infusion of KM871 trace-labeled with indium-111 (111In) to enable assessment of biodistribution in vivo. Biopsies of metastatic melanoma sites were performed on days 7 to 10. RESULTS: Fifteen of 17 patients completed a cycle of three infusions of KM871. No dose-limiting toxicity was observed during the trial; the maximum-tolerated dose was therefore not reached. Three patients (at the 1-, 5-, and 40-mg/m2 dose levels) developed pain and/or erythema at tumor sites consistent with an inflammatory response. No normal tissue uptake of 111In-KM871 was observed, and tumor uptake of 111In-KM871 was observed in all lesions greater than 1.5 cm (tumor biopsy 111KM871 uptake results: range, 0.001% to 0.026% injected dose/g). The ratio of maximum tumor to normal tissue was 15:1. Pharmacokinetic analysis revealed a 111In-KM871 terminal half-life of 7.68 +/- 2.94 days. One patient had a clinical partial response that lasted 11 months. There was no serologic evidence of human antichimeric antibody in any patient, including one patient who received 16 infusions over a 12-month period. CONCLUSION: This study is the first to demonstrate the biodistribution and specific targeting of an anti-GD3 antibody to metastatic melanoma in patients. The long half-life and lack of immunogenicity of KM871 makes this antibody an attractive potential therapy for patients with metastatic melanoma.

Monoclonal antibody 806 inhibits the growth of tumor xenografts expressing either the de2-7 or amplified epidermal growth factor receptor (EGFR) but not wild-type EGFR.

The monoclonal antibody (mAb) 806 was raised against the delta2-7 epidermal growth factor receptor (de2-7 EGFR or EGFRvIII), a truncated version of the EGFR commonly expressed in glioma. Unexpectedly, mAb 806 also bound the EGFR expressed by cells exhibiting amplification of the EGFR gene but not to cells or normal tissue expressing the wild-type receptor in the absence of gene amplification. The unique specificity of mAb 806 offers an advantage over current EGFR antibodies, which all display significant binding to the liver and skin in humans. Therefore, we examined the antitumor activity of mAb 806 against human tumor xenografts grown in nude mice. The growth of U87 MG xenografts, a glioma cell line that endogenously expresses approximately 10(5) EGFRs in the absence of gene amplification, was not inhibited by mAb 806. In contrast, mAb 806 significantly inhibited the growth of U87 MG xenografts transfected with the de2-7 EGFR in a dose-dependent manner using both preventative and established tumor models. Significantly, U87 MG cells transfected with the wild-type EGFR, which increased expression to approximately 10(6) EGFRs/cell and mimics the situation of gene amplification, were also inhibited by mAb 806 when grown as xenografts in nude mice. Xenografts treated with mAb 806 all displayed large areas of necrosis that were absent in control tumors. This reduced xenograft viability was not mediated by receptor down-regulation or clonal selection because levels of antigen expression were similar in control and treated groups. The antitumor effect of mAb 806 was not restricted to U87 MG cells because the antibody inhibited the growth of new and established A431 xenografts, a cell line expressing >10(6) EGFRs/cell. This study demonstrates that mAb 806 possesses significant antitumor activity.

Localization of bradykinin B2 receptors in the endometrium and myometrium of rat uterus and the effects of estrogen and progesterone.

In the uterus, bradykinin is a potent inducer of smooth muscle contraction, which is mediated by the bradykinin B2 receptor subtype. However, little is known about the distribution or regulation of this receptor in this tissue. The aim of this study was to localize the B2 receptor in the uterus and determine whether the levels of this receptor were altered during the estrous cycle and modulated by estrogen and/or progesterone in ovariectomized rats. At diestrus, uterine B2 receptors were localized to both the circular and longitudinal smooth muscle layers of the myometrium, the endometrial stroma, the glandular epithelium, and the layer subjacent to the luminal epithelium. B2 receptor levels in both myometrium and endometrium were lowest during early proestrus, when estrogen levels are low, whereas myometrial B2 receptor protein and messenger RNA levels were highest during late proestrous, when estrogen levels peak. Similar findings were observed for the estrogen-supplemented group after ovariectomy, with progesterone appearing to inhibit the estrogen-induced rise in bradykinin B2 receptor density in estrogen/progesterone-treated animals. Using in vitro receptor autoradiography employing the specific B2 receptor antagonist analog, HPP-HOE140, immunostaining with specific antipeptide antibodies generated against the B2 receptor, and in situ hybridization using a specific bradykinin B2 receptor riboprobe, our findings show a discrete distribution of the bradykinin B2 receptor throughout the different layers of the uterus and suggest that bradykinin B2 receptor levels in the rat uterus are regulated by estrogen, and possibly progesterone, in both myometrium and endometrium.

Localization of bradykinin B2 binding sites in rat kidney following chronic ACE inhibitor treatment.

Bradykinin exerts important influences on renal hemodynamics and tubular function by acting on renal bradykinin B2 receptors. However, the precise sites and mechanisms of its actions on the kidney are not known. To help elucidate the mechanisms of renal actions of bradykinin in vivo, we have employed high resolution electron microscopic autoradiography to localize bradykinin B2 binding sites in the rat kidney following intravenous administration of a radiolabeled ligand, 125I-HPP-Hoe140 (3-4-Hydroxyphenyl-propionyl-DArg0-[Hyp3-Thi5-D-Tic 7-Oic8]-bradykinin), a derivative of the highly selective bradykinin B2 receptor antagonist, Hoe140. In non-treated rats, bradykinin B2 binding sites were localized to the cell bodies and the luminal brush border of the proximal convoluted tubules in the cortex. In the medulla (except for the outer stripe of the outer medulla), binding occurred in the distal tubules, thin limbs of the loop of Henle, collecting ducts, peritubular capillary endothelium and renomedullary interstitial cells. To exclude the possibility that the radioligand may bind to angiotensin converting enzyme, rats were pretreated with the angiotensin converting enzyme inhibitor, perindopril. In these rats, binding to the cell bodies and the luminal brush border of the proximal convoluted tubules in the cortex was completely abolished, while binding remained unaltered in the medulla. Further studies using high performance liquid chromatography revealed that while the radioligand was degraded following systemic administration in nontreated rats, the degradation was significantly reduced in the rats pretreated chronically with perindopril. These results indicate that binding detected in the proximal tubules in the normal rats is due primarily to the tubular uptake of the degraded radioligand, and that bradykinin B2 binding sites occur predominantly in the renal tubules, vascular endothelium, and renomedullary interstitial cells of the renal medulla.

Perindopril chronically inhibits angiotensin-converting enzyme in both the endothelium and adventitia of the internal mammary artery in patients with ischemic heart disease.

BACKGROUND: ACE inhibitors are widely used in treating hypertension and heart failure, but the sites and mechanisms of ACE inhibition in human blood vessels are not understood. The present study was undertaken to assess the sites and extent of in vivo inhibition of ACE by long-term perindopril treatment in different layers of the internal mammary artery in patients with ischemic heart disease. METHODS AND RESULTS: Sixteen patients with ischemic heart disease were treated either with perindopril (4 mg/d PO) for up to 36 days before surgery (n = 9) or without the inhibitor as control subjects (n = 7). The segments of the internal mammary artery were collected for measurement of vascular free and total ACE by quantitative in vitro autoradiography with 125I-351A binding. The patients treated with perindopril had lower plasma ACE (P < .001) and plasma angiotensin (Ang) II-to-Ang I ratio (P < .05). In the internal mammary artery, free ACE was similarly inhibited by perindopril in the endothelium (P < .05) and adventitia (P < .05), and the free ACE-to-total ACE ratio, an index of ACE inhibition, was markedly decreased by perindopril in parallel in the endothelium (P < .001) and adventitia (P < .001). Moreover, plasma ACE correlated highly with vascular ACE in the endothelium (r = .85, P < .001) or adventitia (r = .78, P < .001), and mean arterial pressure correlated significantly with free ACE in the endothelium (r = .52, P < .05) or adventitia (r = .53, P < .05) and with the plasma Ang II-to-Ang I ratio (r = .53, P < .05). Light microscopic autoradiographs of 125I-351A binding revealed a marked inhibition of ACE by perindopril in both layers of the vascular wall. CONCLUSIONS: The present demonstrates that long-term administration of perindopril potently inhibits both endothelial and adventitial ACE to a comparable degree in the human internal mammary artery. These results indicate that perindopril effectively penetrates the vascular wall to inhibit ACE in the adventitia, thus providing evidence that perindopril may be beneficial in inhibiting both circulating Ang II and its local formation in the vascular wall.

Distribution of bradykinin B2 receptors in sheep brain and spinal cord visualized by in vitro autoradiography.

Bradykinin B2 receptors were localized in the sheep brain and spinal cord by quantitative in vitro autoradiography using a radiolabelled and specific bradykinin B2 receptor antagonist analogue, 3-4-hydroxyphenyl-propionyl-D-Arg0-[Hyp3,Thi5,D-Tic 7,Oic8]bradykinin, (HPP-HOE 140). This radioligand displays high affinity and specificity for bradykinin B2 receptors. The respective K(i) values of 0.32, 1.37 and 156 nM were obtained for bradykinin, HOE140 and D-Arg[Hyp3,D-Phe7,Leu8]bradykinin competing for radioligand binding to lamina II of sheep spinal cord sections. Using this radioligand, we have demonstrated the distribution of bradykinin B2 receptors in many brain regions which have not been previously reported. The highest density of bradykinin B2 receptors occur in the pleoglial periaqueductal gray, oculomotor and trochlear nuclei and the circumventricular organs. Moderate densities of receptors occur in the substantia nigra, particularly the reticular part, the posterior thalamic and subthalamic nuclei, zona incerta, the red and pontine nuclei, some of the pretectal nuclei and in discrete layers of the superior colliculus. In the hindbrain, moderate levels of bradykinin B2 receptor binding occur in the nucleus of the solitary tract, and in spinal trigeminal, inferior olivary, cuneate and vestibular nuclei. Laminae II, X and dorsal root ganglia display the most striking binding densities in the spinal cord, while the remainder of the dorsal and ventral horn display a low and diffuse density of binding. Bradykinin B2 receptors are extensively distributed throughout the sheep brain and spinal cord, not only to sensory areas but also to areas involved in motor activity.

Acute and chronic in vivo inhibition of angiotensin-converting enzyme by perindopril in the endothelium and adventitia of large arteries and organs of the rabbit.

Angiotensin-converting enzyme (ACE) inhibitors are widely used in treating hypertension and chronic heart failure, but their precise sites and mechanisms of the actions are not completely understood. In this study, we evaluated the acute and chronic in vivo inhibition of ACE by perindopril in both the endothelium and adventitia of large blood vessels including the aorta, carotid, and femoral arteries, heart, lung, and kidney by using in vitro autoradiography with [(125)I]351A as a ligand. After short-term (0.1, 0.3, and 1 mg/kg) or long-term oral administration (0.3 mg/kg), perindopril significantly inhibited plasma ACE (p < 0.001), the plasma angiotensin II (Ang II)/Ang I ratio (p < 0.01), and decreased mean arterial pressure (p < 0.001) in a dose-related manner. In the aorta, carotid, and femoral arteries, free ACE was inhibited to a similar extent in both the endothelium and adventitia by perindopril, in a dose-dependent manner, whereas total ACE in both layers of these vessels was unaltered. Similar short- and long-term ACE inhibition by perindopril was observed in the lung and heart, with somewhat greater inhibition of kidney and plasma ACE. Vascular and tissue ACE inhibition correlated highly with both plasma ACE and the plasma Ang II/Ang I ratio (r = 0.63-0.89; p < 0.001). Whereas the effects of perindopril on blood pressure, plasma Ang II/Ang I ratio, plasma and vascular ACE were all highly dose dependent, there were no significant differences on the degree of ACE inhibition observed between the three large blood vessels or between their adventitial and endothelial layers. These results demonstrate that perindopril readily penetrates the vascular wall after short- or long-term oral administration, and in a dose-dependent manner, potently inhibits both endothelial and advential vascular ACE to a comparable degree. Therefore ACE inhibitors may be beneficial in inhibiting both circulating Ang II and its local formation in the vascular wall.

Localization of bradykinin B2 receptors in sheep uterus.

The localization and characterization of bradykinin B2 receptors in sheep uterus was carried out using a radiolabelled B2 receptor ligand, 3,4-hydroxyphenypropionyl-D-Arg0-[Hyp3,Thi5,D-++ +Tic7,D-Oic8] bradykinin (HPP-HOE140). Competition of the radioligand, [125I]HPP-HOE140, from membrane preparations of anoestrus sheep uterus by bradykinin agonists and antagonists revealed the presence of high- and low-affinity binding sites with ligand specificity typical of the bradykinin B2 receptor. Using in vitro autoradiography on tissue sections, intense binding was visible over the superficial epithelial layer of the endometrium and inner third of the myometrium of anoestrus sheep uterus. Bradykinin B2 receptors in the myometrium were down regulated in pregnant sheep uterus. We demonstrate that binding studies using [125I]HPP-HOE140 offer high sensitivity and specificity for characterization, quantitation and localization of the bradykinin B2 receptors in tissues and offers new information on uterine bradykinin B2 receptors.

Characterization and localization of bradykinin B2 receptors in the guinea-pig using a radioiodinated HOE140 analogue.

The potent bradykinin B2 receptor antagonist analogue, [125I]HPP-HOE140, ([125I]-3-4-hydroxyphenyl-propionyl-D-Arg0-[Hyp3, Thi5,D-Tic7, Oic8]bradykinin), was used to localize and characterize guinea-pig tissue bradykinin B2 receptors. Analysis of competition for the radioligand binding, using membrane preparations of lung, ileum and uterus, revealed the presence of a high- and low-affinity binding site: at the high-affinity site, the apparent Ki for the various bradykinin B2 receptor ligands ranged from 0.26 to 2.13 nM for HPP-HOE140, from 0.25 to 1.45 nM for HOE140, from 129 to 625 nM for D-Arg0[pHyp3,Phe7]bradykinin and from 0.05 to 1.11 nM for bradykinin. At the low-affinity site, the apparent Ki values ranged from 4.90 to 10.5 nM, from 1.23 to 1.90 nM, 4760 nM and from 2.01 to 62.1 nM, respectively. By contrast, the bradykinin Bi receptor antagonist, des-Arg9[Leu8]bradykinin did not compete for [125I]HPP-HOE140 binding from membrane preparations at concentrations up to 1 microM. Using in vitro autoradiography on tissue sections, intense binding was observed in the lamina propria of the villi of ileum and the arteriolar smooth muscle cells in lung. In the uterus, dense binding was found in the inner third of the myometrium and over epithelial cells of the glandular endometrium, while diffuse binding was observed throughout the endometrial stroma. In the brain, intense binding was observed in the nucleus of the solitary tract, spinal trigeminal tract and area postrema of the hindbrain, the middle cerebral arteries, and the choroid plexus of the third and lateral ventricles. Moderate binding was observed in the CA3 region of the hippocampus and posterior and ventroposterior thalamic nuclei. In the spinal cord, high-density binding occurred in the laminae I and II of the dorsal horn. Unlike previous autoradiographic localization studies of the bradykinin B2 receptor using radiolabeled bradykinin, the radiolabeled antagonist HPP-HOE140 did not bind to bradykinin-degrading peptidases, such as angiotensin-converting enzyme, and displayed subtype specificity. Therefore, binding studies with [125I]HPP-HOE140 offers high sensitivity and specificity for characterization, quantitation and localization of subtypes of bradykinin B2 receptors in tissues, and offers new information on uterine and brain bradykinin B2 receptors.

Angiotensin II receptor subtypes in the human central nervous system.

The distribution of the AT1 and AT2 subtypes of angiotensin II receptor was mapped in the adult human central nervous system using quantitative in vitro autoradiography. Binding in all forebrain, midbrain, pontine, medullary and spinal cord sites where angiotensin II receptors have previously been described is of the AT1 subtype, as is binding in the small and large arteries in the adjacent meninges and in choroid plexus. By contrast, both AT1 and AT2 receptors occur in the molecular layer of the cerebellum. Angiotensin II AT1 receptors in the brain show a moderate degree of conservation across mammalian species studied so far, whereas expression of AT2 receptors is more variable, and is more restricted in the human CNS than in many other mammals. These differences between the subtype distributions in humans and other animals indicate the need for care when extrapolating the results of animal studies involving the brain angiotensin system.

The stability of angiotensin receptors and angiotensin converting enzyme in post mortem brain.

Quantitative in vitro autoradiography was used to assess the post mortem stability of angiotensin II receptors and angiotensin converting enzyme in adult sheep brainstems. There was no significant loss of angiotensin II receptor binding in brainstems stored for up to 24 h at 23 degrees C or for 8 h at 23 degrees C followed by 64 h at 4 degrees C. There was no significant decrease in angiotensin converting enzyme binding in the same nuclei after up to 48 h at 23 degrees C or after 8 h at 23 degrees C followed by up to 64 h at 4 degrees C. Interpretation of neurochemical studies of human brain tissue obtained at autopsy requires assessment of the post mortem stability of the molecules being studied. Our results indicate that angiotensin II receptors and angiotensin converting enzyme are remarkably stable in sheep brainstems after post mortem delays in excess of those usually encountered in hospital autopsies.