Cellular changes in normal blood capillaries undergoing regression after inhibition of VEGF signaling

Elastomeric microposts integrated into microfluidics for flow-mediated endothelial mechanotransduction analysis

Mechanotransduction is known as the cellular mechanism converting insoluble biophysical signals in the local cellular microenvironment (e.g. matrix rigidity, external mechanical forces, and fluid shear) into intracellular signalling to regulate cellular behaviours. While microfluidic technologies support a precise and independent control of soluble factors in the cellular microenvironment (e.g. growth factors, nutrients, and dissolved gases), the regulation of insoluble biophysical signals in microfluidics, especially matrix rigidity and adhesive pattern, has not yet been achieved. Here we reported an integrated soft lithography-compatible microfluidic methodology that could enable independent controls and modulations of fluid shear, substrate rigidity, and adhesive pattern in a microfluidic environment, by integrating micromolded elastomeric micropost arrays and microcontact printing with microfluidics. The geometry of the elastomeric micropost array could be regulated to mediate substrate rigidity and adhesive pattern, and further the elastomeric microposts could be utilized as force sensors to map live-cell subcellular contractile forces. To illustrate the general application of our methodology, we investigated the flow-mediated endothelial mechanotransduction process and examined specifically the involvement of subcellular contractile forces in the morphological realignment process of endothelial cells under a sustained directional fluid shear. Our results showed that the cytoskeletal contractile forces of endothelial cells were spatiotemporally regulated and coordinated to facilitate their morphology elongation process along the direction of flow. Together, our study provided an integrated microfluidic strategy to modulate the in vitro cellular microenvironment with both defined soluble and insoluble signals, and we demonstrated its application to investigate quantitatively the involvement of cytoskeletal contractile forces in the flow-mediated mechanotransduction process of endothelial cells.

The outcome and predictive factors of sunitinib therapy in advanced gastrointestinal stromal tumors (GIST) after imatinib failure - one institution study

BACKGROUND

Gastrointestinal stromal tumors (GIST) mutational status is recognized factor related to the results of tyrosine kinase inhibitors therapy such as imatinib (IM) or sunitinib (SU). Arterial hypertension (AH) is common adverse event related to SU, reported as predictive factor in renal cell carcinoma. The aim of the study was to analyze the outcomes and factors predicting results of SU therapy in inoperable/metastatic CD117(+) GIST patients after IM failure.

METHODS

We identified 137 consecutive patients with advanced inoperable/metastatic GIST treated in one center with SU (2nd line treatment). Median follow-up time was 23 months. Additionally, in 39 patients there were analyzed selected constitutive single nucleotide polymorphisms (SNPs) of VEGFA and VEGFR2 genes.

RESULTS

One year progression-free survival (PFS; calculated from the start of SU) rate was 42% and median PFS was 43 weeks. The estimated overall survival (OS, calculated both from start of SU or IM) was 74 weeks and 51 months, respectively. One-year PFS was 65% (median 74 weeks) in 55 patients with AH vs. 22% (median 17 weeks) in patients without AH. Patients with primary tumors carrying mutations in KIT exon 9 or wild-type had substantially better 1-year PFS (68% and 57%; median 65.5 and 50.5 weeks, respectively) than patients having tumors with KIT exon 11 or PDGFRA mutations (34% and 15%; median 36.8 and 9 weeks, respectively). We identified two independent factors with significant impact on PFS and OS in univariate and multivariate analysis: primary tumor genotype and presence of AH. The most common adverse events during therapy were: fatigue, AH, hypothyroidism, hand and foot syndrome, mucositis, skin reactions, dyspepsia, and diarrhea. Two deaths were assessed as related to tumor rupture caused by reaction to SU therapy. The presence of C-allele in rs833061 and the T-allele in rs3025039 polymorphism of VEGFA were associated with significantly higher risk of hypothyroidism (OR: 10.0 p = 0.041 and OR: 10.5; p = 0.015, respectively).

CONCLUSIONS

We confirmed that many advanced GIST patients benefit from SU therapy with OS > 1.5 year. Primary tumor KIT/PDGFRA genotype and SU-induced AH, as surrogate of its antiangiogenic activity are two independent factors influencing both PFS and OS.

Role of shear-stress-induced VEGF expression in endothelial cell survival

Vascular endothelial growth factor (VEGF) plays a crucial role in developmental and pathological angiogenesis. Expression of VEGF in quiescent adult tissue suggests a potential role in the maintenance of mature blood vessels. We demonstrate, using a Vegf-lacZ reporter mouse model, that VEGF is expressed by arterial but not by venous or capillary endothelial cells (ECs) in vivo. Using an in vitro model, we show that arterial shear stress of human umbilical vein ECs (HUVECs) decreases apoptosis and increases VEGF expression, which is mediated by the induction of Krüppel-like factor 2 (KLF2). Additionally, shear stress stimulates the expression of VEGF receptor 2 (VEGFR2) and is associated with its activation. Knockdown of VEGF in shear stressed HUVECs blocks the protective effect of shear stress, resulting in EC apoptosis equivalent to that in control ECs cultured under static conditions. Similarly, treatment of ECs subjected to arterial shear stress with the VEGF receptor tyrosine kinase inhibitor SU1498, or VEGFR2 neutralizing antiserum, led to increased apoptosis, demonstrating that the mechanoprotection from increased shear is mediated by VEGFR2. Taken together, these studies suggest that arterial flow induces VEGF-VEGFR2 autocrine-juxtacrine signaling, which is a previously unidentified mechanism for vascular EC survival in adult arterial blood vessels.

Norrin stimulates cell proliferation in the superficial retinal vascular plexus and is pivotal for the recruitment of mural cells

Mutations in Norrin, the ligand of a receptor complex consisting of FZD4, LRP5 and TSPAN12, cause severe developmental blood vessel defects in the retina and progressive loss of the vascular system in the inner ear, which lead to congenital blindness and progressive hearing loss, respectively. We now examined molecular pathways involved in developmental retinal angiogenesis in a mouse model for Norrie disease. Comparison of morphometric parameters of the superficial retinal vascular plexus (SRVP), including the number of filopodia, vascular density and number of branch points together with inhibition of Notch signaling by using DAPT, suggest no direct link between Norrin and Notch signaling during formation of the SRVP. We noticed extensive vessel crossing within the SRVP, which might be a loss of Wnt- and MAP kinase-characteristic feature. In addition, endomucin was identified as a marker for central filopodia, which were aligned in a thorn-like fashion at P9 in Norrin knockout (Ndp(y/-)) mice. We also observed elevated mural cell coverage in the SRVP of Ndp(y/-) mice and explain it by an altered expression of PDGFβ and its receptor (PDGFRβ). In vivo cell proliferation assays revealed a reduced proliferation rate of isolectin B4-positive cells in the SRVP from Ndp(y/-) mice at postnatal day 6 and a decreased mitogenic activity of mutant compared with the wild-type Norrin. Our results suggest that the delayed outgrowth of the SRVP and decreased angiogenic sprouting in Ndp(y/-) mice are direct effects of the reduced proliferation of endothelial cells from the SRVP.

Angiogenic properties of myofibroblasts isolated from normal human skin wounds

During wound healing, angiogenesis plays a crucial role in inducing adequate perfusion of the new tissue, thereby allowing its survival. This angiogenic process contributes to the formation of granulation tissue, alongside myofibroblasts. Myofibroblasts are cells specialized in wound contraction and synthesis of new extracellular matrix. Fibroblasts, considered by some to be at the origin of myofibroblasts, have already been shown to promote neovascularization. Thus, we hypothesized that myofibroblasts play a key role during angiogenic development in wound healing. We isolated myofibroblasts from normal human skin wounds and dermal microvascular endothelial cells (HDMVEC) and fibroblasts from skin. Using an in vitro fibrin-based model, we compared the proangiogenic activity of wound myofibroblasts to that of fibroblasts in the presence of HDMVEC. By immunostaining with collagen IV antibodies, we observed the formation of a capillary network significantly more developed when HDMVEC were cultured with myofibroblasts compared to the network formed in the presence of fibroblasts. The differences between these cell types did not result from a differential secretion of Vascular Endothelial Growth Factor or basic Fibroblast Growth Factor. However, in the presence of myofibroblasts, a significant decrease in matrix metalloproteinase activity was observed. This finding was correlated with a significant increase in Tissue Inhibitor of MetalloProteinase (TIMP)-1 and TIMP-3. Furthermore, inhibition of TIMP-1 secretion using shRNA significantly decreased myofibroblasts induced angiogenesis. These results led to the hypothesis that normal wound myofibroblasts contribute to the vascular network development during wound healing. Our data emphasize the critical role of wound myofibroblasts during healing.

Antitumor effect of FP3 in a patient-derived tumor tissue xenograft model of gastric carcinoma through an antiangiogenic mechanism

FP3 (KH902/KH903) is a novel vascular endothelial growth factor (VEGF) blocker with antiangiogenic properties. Previous studies revealed that FP3, a humanized fusion protein that combines ligand binding elements from the extracellular domains of VEGF receptors 1 and 2 and the Fc portion of IgG1, has an inhibitory effect on the VEGF-mediated proliferation and migration of human umbilical vein endothelial cells, and VEGF-mediated vessel sprouting of rat aortic rings in vitro. Thus, FP3 was considered as a new promising agent in treating human choroidal neovascularization (CNV) caused by age-related macular degeneration (AMD). FP3 also has an antitumor effect in a non-small cell lung cancer cell line (A549) xenograft model in nude mice. However, little is known of the direct effects of FP3 on tumor vessels. In this study, we investigated the effects of FP3 on blood vessels in a patient-derived tumor tissue (PDTT) xenograft model of gastric carcinoma, using large tumors with established vasculature. Treatment with FP3 caused robust and early changes in endothelial cells and pericytes of vessels in the PDTT xenograft model. Vascular density decreased and vascular sprouting was suppressed by treatment with FP3. Pericytes did not degenerate to the same extent as endothelial cells, and those on surviving tumor vessels achieved a more normal phenotype. Our results revealed that FP3 has a direct and rapid antiangiogenic effect on tumor vessels, which was achieved mainly via regression of tumor vasculature, inhibition of new and recurrent vessel growth, and normalization of existing tumor vasculature.

Notch4 normalization reduces blood vessel size in arteriovenous malformations

Abnormally enlarged blood vessels underlie many life-threatening disorders including arteriovenous (AV) malformations (AVMs). The core defect in AVMs is high-flow AV shunts, which connect arteries directly to veins, "stealing" blood from capillaries. Here, we studied mouse brain AV shunts caused by up-regulation of Notch signaling in endothelial cells (ECs) through transgenic expression of constitutively active Notch4 (Notch4*). Using four-dimensional two-photon imaging through a cranial window, we found that normalizing Notch signaling by repressing Notch4* expression converted large-caliber, high-flow AV shunts to capillary-like vessels. The structural regression of the high-flow AV shunts returned blood to capillaries, thus reversing tissue hypoxia. This regression was initiated by vessel narrowing without the loss of ECs and required restoration of EphB4 receptor expression by venous ECs. Normalization of Notch signaling resulting in regression of high-flow AV shunts, and a return to normal blood flow suggests that targeting the Notch pathway may be useful therapeutically for treating diseases such as AVMs.

Vascular fasciatherapy danis bois method: a study on mechanism concerning the supporting point applied on arteries

Background

A first study on vascular fasciatherapy enabled us to observe the turning of a turbulent blood flow into a laminar one, and a questioning on the process involved in this transformation emerged. The first question was: What is the nature of artery from the point of view of fascia? And a second question was: Which is the link permitting the observed process working in our first study? So this time, we are investigating a specific aspect of the big question that polarizes the interest of many researchers: “What is fascia?”

Methods

Following Donald Ingber’s statement, “It is necessary to understand how tissues and organs are structured across multiple size scales”, our research methods have been established in order to collect information on what is artery and what is fascia. Concerning these two organs, we have questioned science across the scales of embryology, anatomy, histology and cytology. Beyond the knowledge on structure, the functional link between artery and fascia is the necessary complement of this study whose starting point is in fact a questioning on process. As an application of this study, vascular fasciatherapy Danis-Bois Method and mechanotransduction have been investigated in theoretical and in research aspects to improve the understanding of how they work.

Results

The embryological approach points out a common origin and a histofunctional community of connective tissue and artery. As organs, arteries are sheathed by the adventia-fascia, and are penetrated by connective tissue extensions in media and intima. Furthermore, the functional point of view of this study reports the knowledge on mechanotransduction involving artery, both from the connective side and from the luminal side. Functional anatomy, surgery, histology, and cytology integrating the theory of the extended cytoskeleton, underline continuity from the static and functional points of view, with tensegrity being the architectural principle linking molecules to the entire body.

Conclusion

By answering these questions, we are attempting a better understanding of the mechanisms occurring in the progress of the arterial supporting point. One could presume that it relaxes adventitia and media, locally and all along the arterial network. Its action could also extend inward to the intima and on blood, as well as outwards to the neighboring connective tissue. By its local and remote action, it may be useful when diseases associate general perturbations and arterial disorders, like in high blood pressure or in aging.

Mechanisms of vessel regression: toward an understanding of the resolution of angiogenesis

Physiological angiogenesis refers to a naturally occurring process of blood vessel growth and regression, and it occurs as an integral component of tissue repair and regeneration. During wound healing, sprouting and branching results in an extensive yet immature and leaky neovascular network that ultimately resolves by systematic pruning of extraneous vessels to yield a stable, well-perfused vascular network ideally suited to maintain tissue homeostasis. While the molecular mechanisms of blood vessel growth have been explored in numerous cell and animal models in remarkable detail, the endogenous factors that prevent further angiogenesis and control vessel regression have not received much attention and are largely unknown. In this review, we introduce the relevant literature from various disciplines to fill the gaps in the current limited understanding of the major molecular and biomechanical inducers of vascular regression. The processes are described in the context of endothelial cell biology during wound healing: hypoxia-driven activation and sprouting followed by apoptosis or maturation of cells comprising the vasculature. We discuss and integrate the likely roles of a variety of endogenous factors, including oxygen availability, vessel perfusion and shear stress, intracellular negative feedback mechanisms (Spry2, vasohibin), soluble cytokines (CXCL10), matrix-binding proteins (TSP, PEDF), protein cleavage products (angiostatin, vasostatin), matrix-derived anti-angiogenic peptides (endostatin, arresten, canstatin, tumstatin), and the biomechanical properties of remodeling the extra-cellular matrix itself. These factors aid in the spatio-temporal control of blood vessel pruning by inducing specific anti-angiogenic signaling pathways in activated endothelial cells, pathways which compete with pro-angiogenic and maturation signals in the resolving wound. Gaining more insight into these mechanisms is bound to shed light on unresolved questions regarding scar formation, tissue regeneration, and increase our understanding of the many diseases with angiogenic phenotypes, especially cancer.

Anaplastic thyroid carcinoma

Thyroid cancers represent about 1% of all human cancers. Differentiate thyroid carcinomas (DTCs), papillary and follicular cancers, are the most frequent forms, instead Anaplastic Thyroid Carcinoma (ATC) is estimated to comprise 1-2% of thyroid malignancies and it accounts for 14-39% of thyroid cancer deaths. The annual incidence of ATC is about one to two cases/million, with the overall incidence being higher in Europe (and area of endemic goiter) than in USA. ATC has a more complex genotype than DTCs, with chromosomal aberrations present in 85-100% of cases. A small number of gene mutations have been identified, and there appears to be a progression in mutations acquired during dedifferentiation. The mean survival time is around 6 months from diagnosis an outcome that is frequently not altered by treatment. ATC presents with a rapidly growing fixed and hard neck mass, often metastatic local lymph nodes appreciable on examination and/or vocal paralysis. Symptoms may reflect rapid growth of tumor with local invasion and/or compression. The majority of patients with ATC die from aggressive local regional disease, primarily from upper airway respiratory failure. For this reason, aggressive local therapy is indicated in all patients who can tolerate it. Although rarely possible, complete surgical resection gives the best chance of long-term control and improved survival. Therapy options include surgery, external beam radiation therapy, tracheostomy, chemotherapy, and investigational clinical trials. Multimodal or combination therapy should be useful. In fact, surgical debulking of local tumor, combined with external beam radiation therapy and chemotherapy as neoadjuvant (before surgery) or adjuvant (after surgery) therapy, may prevent death from local airway obstruction and as best may slight prolong survival. Investigational clinical trials in phase I or in phase II are actually in running and they include anti-angiogenetic drugs, multi-kinase inhibitor drugs.

Signaling required for blood vessel maintenance: molecular basis and pathological manifestations

As our understanding of molecular mechanisms leading to vascular formation increases, vessel maintenance including stabilization of new vessels and prevention of vessel regression began to be considered as an active process that requires specific cellular signaling. While signaling pathways such as VEGF, FGF, and angiopoietin-Tie2 are important for endothelial cell survival and junction stabilization, PDGF and TGF-β signaling modify mural cell (vascular smooth muscle cells and pericytes) functions, thus they fortify vessel integrity. Breakdown of these signaling systems results in pathological hyperpermeability and/or genetic vascular abnormalities such as vascular malformations, ultimately progressing to hemorrhage and edema. Hence, blood vessel maintenance is fundamental to controlling vascular homeostasis and tissue functions. This paper discusses signaling pathways essential for vascular maintenance and clinical conditions caused by deterioration of vessel integrity.

Toward an in vitro vasculature: differentiation of mesenchymal stromal cells within an endothelial cell-seeded modular construct in a microfluidic flow chamber

An in vitro tissue construct amenable to perfusion was formed by randomly packing mesenchymal stromal cell (MSC)-embedded, endothelial cell (EC)-coated collagen cylinders (modules) into a microfluidic chamber. The interstices created by the random packing of the submillimeter-sized modules created EC-lined channels. Flow caused a greater than expected amount of contraction and remodeling in the modular constructs. Flow influenced the MSC to develop smooth muscle cell markers (smooth muscle actin-positive, desmin-positive, and von Willebrand factor-negative) and migrate toward the surface of the modules. When modules were coated with EC, the extent of MSC differentiation and migration increased, suggesting that the MSC were becoming smooth muscle cell- or pericyte-like in their location and phenotype. The MSC also proliferated, resulting in a substantial increase in the number of differentiated MSC. These effects were markedly less for static controls not experiencing flow. As the MSC migrated, they created new matrix that included the deposition of proteoglycans. Collectively, these results suggest that MSC-embedded modules may be useful for the formation of functional vasculature in tissue engineered constructs. Moreover, these flow-conditioned tissue engineered constructs may be of interest as three-dimensional cell-laden platforms for drug testing and biological assays.

Mechanisms of antiangiogenic-induced arterial hypertension

Antiangiogenic therapy has emerged as an important concept in the treatment of solid tumors. Vascular endothelial growth factor (VEGF) represents an important therapeutic target, as it is the primary mediator of angiogenesis and is induced by multiple tumor-relevant stimuli. Arterial hypertension has been commonly reported in all clinical trials testing inhibitors of angiogenesis (especially inhibitors of VEGF/VEGFR-2 signalling), with incidence ranging from 11% to 43% in all studies. The mechanism of elevated blood pressure in patients treated with antiangiogenic agents is not fully understood, but it is probably multifactorial, involving endothelial dysfunction and capillary rarefaction. Recently, several studies have suggested that early blood pressure rise was associated with better antitumoral efficacy and improved prognosis, making this commonly observed effect a promising marker of efficacy.

Subthreshold diode laser micropulse photocoagulation versus intravitreal injections of bevacizumab in the treatment of central serous chorioretinopathy

PURPOSE

To evaluate the treatment of central serous chorioretinopathy (CSC) with either subthreshold diode laser MicroPulse (SDM) or intravitreal bevacizumab (BCZ).

METHODS

This comparative, controlled, prospective study conducted over a period of 10 months examined 52 eyes of 52 patients with (a) treatment with SDM at the active leakage site guided by fluorescein angiography (FA) (n=16 eyes), (b) intravitreal injection of 1.25 mg BCZ (n=10 eyes), or (c) observation (n=26 eyes). Outcome measures included changes in retinal pigment epithelium (RPE) leakage at FA, central macular thickness (CMT), best-corrected visual acuity (BCVA), and 10° macular perimetry.

RESULTS

At the end of the study, there was 12.5% persistent leakage in the SDM, compared with 60% in the BCZ and 92% in the control group. Mean CMT decreased by 94 μm in the SDM, 38 μm in the BCZ, and did not change in the control group. Mean BCVA improved more than 6 early treatment of diabetic retinopathy study letters in the SDM, decreased by one letter in the BCZ, and by two letters in the control group. In the SDM group, mean perimetric deficit improved by 1.5 decibels and corrected lost variance by 2.6. In the BCZ, it improved by 0.6, and in the control group by 0.5. Retreatment was required in 7/16 eyes of the SDM group (43.75%), and in 5/10 eyes of the BCZ group (50%).

CONCLUSION

SDM photocoagulation was superior to intravitreal injections of 1.25 mg BCZ in the treatment of CSC, which resulted in enhanced visual acuity and macular perimetry.

Matrix metalloproteinase activity causes VEGFR-2 cleavage and microvascular rarefaction in rat mesentery

A complication of the spontaneously hypertensive rat (SHR) is microvascular rarefaction, defined by the loss of microvessels. However, the molecular mechanisms involved in this process remain incompletely identified. Recent work in our laboratory suggests that matrix metalloproteinases (MMPs) may play a role by cleavage of the vascular endothelial growth factor receptor 2 (VEGFR-2). In order to further delineate the role for MMPs in microvascular rarefaction, the objective of the current study was to examine the relationship in the same tissue between MMP activity, VEGFR-2 cleavage and rarefaction. Using an in vivo microzymographic technique, we show significantly enhanced levels of MMP-1, -1/-9, -7, and -8 activities, but not MMP-2 and -3 activities, along mesenteric microvessels of the SHR compared to its normotensive control, Wistar Kyoto rat. Based on immunohistochemical methods, the SHR exhibited a decreased labeling of the extracellular, but not the intracellular, domain of VEGFR-2 along mesenteric microvessels. Chronic MMP inhibition served to attenuate VEGFR-2 cleavage and microvascular network rarefaction in the SHR mesentery. These results spatially link MMP-induced VEGFR-2 cleavage and rarefaction in the mesentery of the SHR and thus support the hypothesis that MMPs serve as regulators of microvascular dysfunction in hypertension.

Principles and mechanisms of vessel normalization for cancer and other angiogenic diseases

Despite having an abundant number of vessels, tumours are usually hypoxic and nutrient-deprived because their vessels malfunction. Such abnormal milieu can fuel disease progression and resistance to treatment. Traditional anti-angiogenesis strategies attempt to reduce the tumour vascular supply, but their success is restricted by insufficient efficacy or development of resistance. Preclinical and initial clinical evidence reveal that normalization of the vascular abnormalities is emerging as a complementary therapeutic paradigm for cancer and other vascular disorders, which affect more than half a billion people worldwide. Here, we discuss the mechanisms, benefits, limitations and possible clinical translation of vessel normalization for cancer and other angiogenic disorders.

Endothelialized biomaterials for tissue engineering applications in vivo

Rebuilding tissues involves the creation of a vasculature to supply nutrients and this in turn means that the endothelial cells (ECs) of the resulting endothelium must be a quiescent non-thrombogenic blood contacting surface. Such ECs are deployed on biomaterials that are composed of natural materials such as extracellular matrix proteins or synthetic polymers in the form of vascular grafts or tissue-engineered constructs. Because EC function is influenced by their origin, biomaterial surface chemistry and hemodynamics, these issues must be considered to optimize implant performance. In this review, we examine the recent in vivo use of endothelialized biomaterials and discuss the fundamental issues that must be considered when engineering functional vasculature.

A transgenic model for conditional induction and rescue of portal hypertension reveals a role of VEGF-mediated regulation of sinusoidal fenestrations

Portal hypertension (PH) is a common complication and a leading cause of death in patients with chronic liver diseases. PH is underlined by structural and functional derangement of liver sinusoid vessels and its fenestrated endothelium. Because in most clinical settings PH is accompanied by parenchymal injury, it has been difficult to determine the precise role of microvascular perturbations in causing PH. Reasoning that Vascular Endothelial Growth Factor (VEGF) is required to maintain functional integrity of the hepatic microcirculation, we developed a transgenic mouse system for a liver-specific-, reversible VEGF inhibition. The system is based on conditional induction and de-induction of a VEGF decoy receptor that sequesters VEGF and preclude signaling. VEGF blockade results in sinusoidal endothelial cells (SECs) fenestrations closure and in accumulation and transformation of the normally quiescent hepatic stellate cells, i.e. provoking the two processes underlying sinusoidal capillarization. Importantly, sinusoidal capillarization was sufficient to cause PH and its typical sequela, ascites, splenomegaly and venous collateralization without inflicting parenchymal damage or fibrosis. Remarkably, these dramatic phenotypes were fully reversed within few days from lifting-off VEGF blockade and resultant re-opening of SECs' fenestrations. This study not only uncovered an indispensible role for VEGF in maintaining structure and function of mature SECs, but also highlights the vasculo-centric nature of PH pathogenesis. Unprecedented ability to rescue PH and its secondary manifestations via manipulating a single vascular factor may also be harnessed for examining the potential utility of de-capillarization treatment modalities.

VEGF and c-Met blockade amplify angiogenesis inhibition in pancreatic islet cancer

Angiogenesis inhibitors that block VEGF receptor (VEGFR) signaling slow the growth of many types of tumors, but eventually the disease progresses. Multiple strategies are being explored to improve efficacy by concurrent inhibition of other functionally relevant receptor tyrosine kinases (RTK). XL880 (foretinib, GSK1363089) and XL184 (cabozantinib) are small-molecule inhibitors that potently block multiple RTKs, including VEGFR and the receptor of hepatocyte growth factor c-Met, which can drive tumor invasion and metastasis. This study compared the cellular effects of XL880 and XL184 with those of an RTK inhibitor (XL999) that blocks VEGFR but not c-Met. Treatment of RIP-Tag2 mice with XL999 resulted in 43% reduction in vascularity of spontaneous pancreatic islet tumors over 7 days, but treatment with XL880 or XL184 eliminated approximately 80% of the tumor vasculature, reduced pericytes and empty basement membrane sleeves, caused widespread intratumoral hypoxia and tumor cell apoptosis, and slowed regrowth of the tumor vasculature after drug withdrawal. Importantly, XL880 and XL184 also decreased invasiveness of primary tumors and reduced metastasis. Overall, these findings indicate that inhibition of c-Met and functionally related kinases amplifies the effects of VEGFR blockade and leads to rapid, robust, and progressive regression of tumor vasculature, increased intratumoral hypoxia and apoptosis, and reduced tumor invasiveness and metastasis.

Pericyte requirement for anti-leak action of angiopoietin-1 and vascular remodeling in sustained inflammation

Blood vessel leakiness is an early, transient event in acute inflammation but can also persist as vessels undergo remodeling in sustained inflammation. Angiopoietin/Tie2 signaling can reduce the leakiness through changes in endothelial cells. The role of pericytes in this action has been unknown. We used the selective PDGF-B-blocking oligonucleotide aptamer AX102 to determine whether disruption of pericyte-endothelial crosstalk alters vascular leakiness or remodeling in the airways of mice under four different conditions: i) baseline, ii) acute inflammation induced by bradykinin, iii) sustained inflammation after 7-day infection by the respiratory pathogen Mycoplasma pulmonis, or iv) leakage after bradykinin challenge in the presence of vascular stabilization by the angiopoietin-1 (Ang1) mimic COMP-Ang1 for 7 days. AX102 reduced pericyte coverage but did not alter the leakage of microspheres from tracheal blood vessels at baseline or after bradykinin; however, AX102 exaggerated leakage at 7 days after M. pulmonis infection and increased vascular remodeling and disease severity at 14 days. AX102 also abolished the antileakage effect of COMP-Ang1 at 7 days. Together, these findings show that pericyte contributions to endothelial stability have greater dependence on PDGF-B during the development of sustained inflammation, when pericyte dynamics accompany vascular remodeling, than under baseline conditions or in acute inflammation. The findings also show that the antileakage action of Ang1 requires PDGF-dependent actions of pericytes in maintaining endothelial stability.

Sunitinib for Taiwanese patients with gastrointestinal stromal tumor after imatinib treatment failure or intolerance

AIM: To report preliminary results of the efficacy and safety of sunitinib in the management of Taiwanese gastrointestinal stromal tumors (GIST) patients facing imatinib mesylate (IM) intolerance or failure.

METHODS: Between 2001 and May 2010, 199 Taiwanese patients with metastatic GIST were treated at Chang Gung Memorial Hospital. Among them, 23 (11.6%) patients receiving sunitinib were investigated.

RESULTS: Sixteen male and 7 female patients with a median age of 59 years (range: 24-83 years) received sunitinib. Twenty-two GIST patients changed to sunitinib because of IM failure and 1 because of intolerance. The median duration of sunitinib administration was 6.0 mo (range: 2-29 mo). The clinical benefit was 65.2% [2 complete response (CR), 4 partial response (PR), and 9 stationary disease (SD); 15/23]. In 12 patients harboring mutations of the kit gene at exon 11, the clinical benefit rate (CR, PR, and SD) was 75.0% and 6 patients with tumors containing kit exon 9 mutations had a clinical benefit of 50.0% (not significant, P = 0.344). The progression free survival (PFS) and overall survival (OS) did not differ between patients whose GISTs had wild type, KIT exon 9, or KIT exon 11 mutations. Hand-foot syndrome was the most common cause of grade III adverse effect (26.1%), followed by anemia (17.4%), and neutropenia (13.0%). During the median 7.5-mo follow-up after sunitinib use, the median PFS and OS of these 23 GIST patients after sunitinib treatment were 8.4 and 14.1 mo, respectively.

CONCLUSION: Sunitinib appears to be an effective treatment for Taiwanese with IM-resistant/intolerant GISTs and induced a sustained clinical benefit in more than 50% of Taiwanese advanced GIST patients.

Pleiotropic stromal effects of vascular endothelial growth factor receptor 2 antibody therapy in renal cell carcinoma models

The benefits of inhibiting vascular endothelial growth factor (VEGF) signaling in cancer patients are predominantly attributed to effects on tumor endothelial cells. Targeting non-endothelial stromal cells to further impact tumor cell growth and survival is being pursued through the inhibition of additional growth factor pathways important for the survival and/or proliferation of these cells. However, recent data suggest that VEGF receptor (VEGFR)-specific inhibitors may target lymphatic vessels and pericytes in addition to blood vessels. Here, in fact, we demonstrate that DC101 (40 mg/kg, thrice a week), an antibody specific to murine VEGFR2, significantly reduces all three of these stromal components in subcutaneous (SKRC-29) and orthotopic (786-O-LP) models of renal cell carcinoma (RCC) established in nu/nu athymic mice. Sunitinib (40 mg/kg, once daily), a receptor tyrosine kinase inhibitor of VEGFR2 and other growth factor receptors, also caused significant loss of tumor blood vessels in RCC models but had weaker effects than DC101 on pericytes and lymphatic vessels. In combination, sunitinib did not significantly add to the effects of DC101 on tumor blood vessels, lymphatic vessels, or pericytes. Nevertheless, sunitinib increased the effect of DC101 on tumor burden in the SKRC-29 model, perhaps related to its broader specificity. Our data have important implications for combination therapy design, supporting the conclusion that targeting VEGFR2 alone in RCC has the potential to have pleiotropic effects on tumor stroma.

VEGF and angiopoietin signaling in tumor angiogenesis and metastasis

Solid tumors require blood vessels for growth and dissemination, and lymphatic vessels as additional conduits for metastatic spread. The identification of growth factor receptor pathways regulating angiogenesis has led to the clinical approval of the first antiangiogenic molecules targeted against the vascular endothelial growth factor (VEGF)-VEGF receptor (VEGFR)-2 pathway. However, in many cases resistance to anti-VEGF-VEGFR therapy occurs, and thus far the clinical benefit has been limited to only modest improvements in overall survival. Therefore, novel treatment modalities are required. Here, we discuss the members of the VEGF-VEGFR family as well as the angiopoietin growth factors and their Tie receptors as potential novel targets for antiangiogenic and antilymphangiogenic therapies.

Vascular normalization in orthotopic glioblastoma following intravenous treatment with lipid-based nanoparticulate formulations of irinotecan (Irinophore C™), doxorubicin (Caelyx®) or vincristine

Background

Chemotherapy for glioblastoma (GBM) patients is compromised in part by poor perfusion in the tumor. The present study evaluates how treatment with liposomal formulation of irinotecan (Irinophore C™), and other liposomal anticancer drugs, influence the tumor vasculature of GBM models grown either orthotopically or subcutaneously.

Methods

Liposomal vincristine (2 mg/kg), doxorubicin (Caelyx^®; 15 mg/kg) and irinotecan (Irinophore C™; 25 mg/kg) were injected intravenously (i.v.; once weekly for 3 weeks) in Rag2M mice bearing U251MG tumors. Tumor blood vessel function was assessed using the marker Hoechst 33342 and by magnetic resonance imaging-measured changes in vascular permeability/flow (K_trans). Changes in CD31 staining density, basement membrane integrity, pericyte coverage, blood vessel diameter were also assessed.

Results

The three liposomal drugs inhibited tumor growth significantly compared to untreated control (p < 0.05-0.001). The effects on the tumor vasculature were determined 7 days following the last drug dose. There was a 2-3 fold increase in the delivery of Hoechst 33342 observed in subcutaneous tumors (p < 0.001). In contrast there was a 5-10 fold lower level of Hoechst 33342 delivery in the orthotopic model (p < 0.01), with the greatest effect observed following treatment with Irinophore C. Following treatment with Irinophore C, there was a significant reduction in K_trans in the orthotopic tumors (p < 0.05).

Conclusion

The results are consistent with a partial restoration of the blood-brain barrier following treatment. Further, treatment with the selected liposomal drugs gave rise to blood vessels that were morphologically more mature and a vascular network that was more evenly distributed. Taken together the results suggest that treatment can lead to normalization of GBM blood vessel the structure and function. An in vitro assay designed to assess the effects of extended drug exposure on endothelial cells showed that selective cytotoxic activity against proliferating endothelial cells could explain the effects of liposomal formulations on the angiogenic tumor vasculature.

Anaplastic thyroid carcinoma: A comprehensive review of current and future therapeutic options

Anaplastic thyroid carcinoma (ATC) is the rarest, but deadliest histologic type among thyroid malignancies, with a dismal median survival of 3-9 mo. Even though ATC accounts for less than 2% of all thyroid tumors, it is responsible for 14%-39% of thyroid carcinoma-related deaths. ATC clinically presents as a rapidly growing mass in the neck, associated with dyspnoea, dysphagia and vocal cord paralysis. It is usually locally advanced and often metastatic at initial presentation. For operable diseases, the combination of radical surgery with adjuvant radiotherapy or chemotherapy, using agents such as doxorubicin and cisplatin, is the best treatment strategy. Cytotoxic drugs for advanced/metastatic ATC are poorly effective. On the other hand, targeted agents might represent a viable therapeutic option. Axitinib, combretastatin A4, sorafenib and imatinib have been tested in small clinical trials of ATC, with a promising disease control rate ranging from 33% to 75%. Other clinical trials of targeted therapy for thyroid carcinoma are currently ongoing. Biological agents that are under investigation include pazopanib, gefitinib and everolimus. With the very limited therapeutic armamentarium available at the present time, targeted therapy constitutes an exciting new horizon for ATC. In future, biological agents will probably represent the standard of care for this aggressive malignancy, in the same fashion as it has recently occurred for other chemo-refractory tumors, such as kidney and hepatic cancer.

A patient presenting nasal septum perforation during bevacizumab-containing chemotherapy for advanced breast cancer

Nasal septum perforation is a rare but described complication of the anti-angiogenetic agent bevacizumab. This is the case of a 48-year-old female breast cancer patient, who developed a nasal septum perforation during treatment with paclitaxel and bevacizumab for advanced disease. After 2 cycles the patient developed nasal irritation and occasional epistaxis; after the 4th cycle with bevacizumab the symptoms worsened to include nasal congestion, major epistaxis and rhinorrhoea. Anterior rhinoscopy revealed a large perforation involving the antero-inferior portion of the cartilaginous nasal septum surrounded by necrotic mucosa. The upper septum and the columellar strut were intact. The patient denied use of cocaine or other intranasal irritants. Bevacizumab was discontinued and with only a topical intranasal vitamin application the symptoms improved. One month later anterior rhinoscopy showed that the lesion healed and normal mucosa surrounded the previous site of perforation. The patient continued successfully with other chemotherapy regimens (gemcitabine and then vinorelbine) until irreversible progressive disease led to her death in February 2010. Thus far 8 other cases of bevacizumab-related nasal septum perforation have been published: 5 patients with colorectal cancer, 2 patients with breast cancer and 1 with ovarian cancer. Nasal septum perforation is an emerging challenge with targeted therapies and in particular with antiangiogenetic or antivascular agents. A rapid diagnosis is important and hence we recommend that patients undergoing treatment with bevacizumab and presenting with nasal symptoms (epistaxis, crusting, rhinorrhoea, nasal congestion and local pain or irritation) should undergo anterior rhinoscopy immediately.

Rapid remodeling of airway vascular architecture at birth

Recent advances have documented the development of lung vasculature before and after birth, but less is known of the growth and maturation of airway vasculature. We sought to determine whether airway vasculature changes during the perinatal period and when the typical adult pattern develops. On embryonic day 16.5 mouse tracheas had a primitive vascular plexus unlike the adult airway vasculature, but instead resembling the yolk sac vasculature. Soon after birth (P0), the primitive vascular plexus underwent abrupt and extensive remodeling. Blood vessels overlying tracheal cartilage rings regressed from P1 to P3 but regrew from P4 to P7 to form the hierarchical, segmented, ladder-like adult pattern. Hypoxia and HIF-1α were present in tracheal epithelium over vessels that survived but not where they regressed. These findings reveal the plasticity of airway vasculature after birth and show that these vessels can be used to elucidate factors that promote postnatal vascular remodeling and maturation.

Effect of intravitreal bevacizumab on vascular endothelial growth factor expression in patients with proliferative diabetic retinopathy

PURPOSE

To investigate the effect of bevacizumab (Avastin; Genentech, San Francisco, CA, USA) on vascular endothelial growth factor (VEGF) expression and inflammation in fibrovascular membranes in patients with proliferative diabetic retinopathy (PDR).

MATERIALS AND METHODS

Fibrovascular membranes from 19 eyes of 18 patients with PDR were studied using immunohistochemistry and analyzed in the following 3 groups; group 1: 4 inactive PDR eyes, group 2: 10 active PDR eyes treated preoperatively with adjunctive intravitreal bevacizumab, group 3: five active PDR eyes not treated preoperatively with bevacizumab. Immunohistochemical staining for VEGF, CD31 and CD68 were done.

RESULTS

The immunoreactivity to VEGF and CD 31-positive blood vessels was significantly higher in membranes from group 3 than group 1 (p = 0.007 for VEGF, 0.013 for CD 31-positive vessels). Intravitreal bevacizumab caused a reduction in VEGF expression and vascular densities in 4 out of 10 (40%) excised membranes from eyes with PDR. However, six membranes (60%) in group 2 still demonstrated relatively strong VEGF expression and high vascular density. Infiltration of macrophages was observed in 16 out of the 19 membranes, and the density of macrophages was increased in group 2 compared with group 1 (p = 0.043).

CONCLUSION

Intravitreal bevacizumab injections caused some reduction in VEGF expression and vascular densities in a limited number of active PDR patients. A single intravitreal bevacizumab injection may not be enough to induce complete blockage of VEGF and pathologic neovascularization in active PDR patients. Repeated injections, panretinal photocoagulation and/or PPV may be necessary following intravitreal bevacizumab to reinforce the anti-VEGF effect of the drug.

Molecular Therapies in Thyroid Cancer

Thyroid cancer is a common diagnosis with greater than 34,000 cases per year in the United States. Early stage thyroid cancer is often managed with surgical intervention and radioactive iodine; however, for recurrent or metastatic disease, the treatment options, historically, have been limited to chemotherapy. Chemotherapy for metastatic thyroid cancer has been of limited efficacy. Encouragingly, molecular therapeutics have played a greater role in managing patients with advanced disease. These agents work primarily through disruption of tyrosine kinase pathways. This review will discuss the expanding role of molecular targets in managing patients with advanced thyroid cancer.

Hypertension induced by vascular endothelial growth factor signaling pathway inhibition: mechanisms and potential use as a biomarker

Drugs that inhibit the vascular endothelial growth factor (VEGF) signaling pathway are a rapidly growing chemotherapy class for treatment of solid tumors. This targeted therapy is more specific than traditional chemotherapy, causing fewer side effects. However, VEGF-targeted therapies cause hypertension in 30% to 80% of patients. Unlike traditional off-target side effects, hypertension is a mechanism-dependent, on-target toxicity, reflecting effective inhibition of the VEGF signaling pathway rather than nonspecific effects on unrelated signaling pathways. In this article, we review current understanding of the mechanisms of VEGF-targeted therapy-induced hypertension, discuss similarities with preeclampsia, review implications for therapy of this increasingly common clinical problem, and discuss the potential use of blood pressure increase as a biomarker for proper drug dosing and effective VEGF pathway inhibition.

Vascular endothelial growth factor as an anti-angiogenic target for cancer therapy

New blood vessel formation (angiogenesis) is fundamental to tumor growth, invasion, and metastatic dissemination. The vascular endothelial growth factor (VEGF) signaling pathway plays pivotal roles in regulating tumor angiogenesis. VEGF as a therapeutic target has been validated in various types of human cancers. Different agents including antibodies, aptamers, peptides, and small molecules have been extensively investigated to block VEGF and its pro-angiogenic functions. Some of these agents have been approved by FDA and some are currently in clinical trials. Combination therapies are also being pursued for better tumor control. By providing comprehensive real-time information, molecular imaging of VEGF pathway may accelerate the drug development process. Moreover, the imaging will be of great help for patient stratification and therapeutic effect monitoring, which will promote effective personalized molecular cancer therapy. This review summarizes the current status of tumor therapeutic agents targeting to VEGF and the applications of VEGF related molecular imaging.

A phase I study of continuous infusion cilengitide in patients with solid tumors

BACKGROUND

Cilengitide (EMD121974) is a cyclized pentapeptide that is a potent and selective integrin antagonist which has shown activity in malignant gliomas. In all previous studies, cilengitide has been administered in an intermittent fashion. However, cilengitide has a short half-life of 3-5 h with no evidence of drug accumulation. These data prompted the initiation of this phase I study of continuous infusion cilengitide.

METHODS

Cilengitide was administered as a continuous infusion without break in 4-week cycles. Plasma samples for pharmacokinetic studies were obtained weekly in cycle 1 immediately prior to and 2 h after infusion bag change.

RESULTS

Thirty-five patients were treated (median age 56; 23 males) at dose levels of 1, 2, 4, 8, 12, 18, 27, and 40 mg/h. Toxicities were limited to grade ≤ 2 and showed no relation to dose. Fatigue was most common (17%), while all other toxicities were reported in <10% of patients. No dose-limiting toxicities were observed, and therefore the maximum tolerated dose was not reached. Pharmacokinetic analysis showed that values for clearance and volume of distribution were comparable across dose levels, and the steady-state concentration increased proportionally with dose.

CONCLUSIONS

Cilengitide can be safely administered as a continuous infusion at doses up to at least 40 mg/h, which represents the maximum feasible dose due to drug solubility and delivery limitations. The pharmacokinetics of continuous infusion cilengitide are linear and consistent with the results obtained using a twice weekly infusion.

Clinical applications of VEGF-trap (aflibercept) in cancer treatment

Angiogenesis is one of the key acquired characteristics or "hallmarks" essential for the growth and development of all solid tumor types. The antiangiogenic agent vascular endothelial growth factor-Trap (VEGF-Trap) (aflibercept), which is a composite decoy receptor based on VEGF receptor-1 and VEGF receptor-2 fused to an Fc segment of immunoglobulin G1 that binds specifically to VEGF, has demonstrated preclinical efficacy in a range of different tumor types. VEGF-Trap exerts its antiangiogenic effects through regression of tumor vasculature, remolding or normalization of surviving vasculature, and inhibition of new tumor vessel growth. Preclinical and clinical studies have reported that VEGF-Trap can be combined effectively with both chemotherapy and radiotherapy. This review examines the main effects of VEGF-Trap on tumor vasculature and on different types of solid tumors, and explores the preclinical and clinical benefits of incorporating VEGF-Trap into anticancer treatment strategies.

The unique characteristics of tumor vasculature and preclinical evidence for its selective disruption by Tumor-Vascular Disrupting Agents

The vasculature of solid tumors is fundamentally different from that of normal vasculature and offers a unique target for anti-cancer therapy. Direct vascular-targeting with Tumor-Vascular Disrupting Agents (Tumor-VDAs) is distinctly different from anti-angiogenic strategies, and offers a complementary approach to standard therapies. Tumor-VDAs therefore have significant potential when combined with chemotherapy, radiotherapy, and angiogenesis-inhibiting agents. Preclinical studies with the different Tumor-VDA classes have demonstrated key tumor-selective anti-vascular and anti-tumor effects.

Vascular endothelial growth factor: much more than an angiogenesis factor

Vascular endothelial growth factor (VEGF) is best known as a cytokine essential for embryonic vasculogenesis and for the angiogenesis associated with various pathologies including cancer. However, VEGF also serves other functions that are less widely recognized. An early study (Berse et al., 1992) revealed widespread expression of VEGF transcripts in adult tissues devoid of ongoing neovascularization, thereby predicting additional VEGF functions distinct from angiogenesis. More recent studies have confirmed that VEGF does indeed serve multiple additional functions, including normal maintenance of endothelial and neural cell compartments. These findings have important implications for the use of VEGF antagonists and VEGF receptor antagonists in patients for which inhibition of pathological angiogenesis is the therapeutic goal.

Initial assessment, surveillance, and management of blood pressure in patients receiving vascular endothelial growth factor signaling pathway inhibitors

Hypertension is a mechanism-based toxic effect of drugs that inhibit the vascular endothelial growth factor signaling pathway (VSP). Substantial evidence exists for managing hypertension as a chronic condition, but there are few prospectively collected data on managing acute hypertension caused by VSP inhibitors. The Investigational Drug Steering Committee of the National Cancer Institute convened an interdisciplinary cardiovascular toxicities expert panel to evaluate this problem, to make recommendations to the Cancer Therapy Evaluation Program on further study, and to structure an approach for safe management by treating physicians. The panel reviewed: the published literature on blood pressure (BP), hypertension, and specific VSP inhibitors; abstracts from major meetings; shared experience with the development of VSP inhibitors; and established principles of hypertension care. The panel generated a consensus report including the recommendations on clinical concerns summarized here. To support the greatest possible number of patients to receive VSP inhibitors safely and effectively, the panel had four recommendations: 1) conduct and document a formal risk assessment for potential cardiovascular complications, 2) recognize that preexisting hypertension will be common in cancer patients and should be identified and addressed before initiation of VSP inhibitor therapy, 3) actively monitor BP throughout treatment with more frequent assessments during the first cycle of treatment, and 4) manage BP with a goal of less than 140/90 mmHg for most patients (and to lower, prespecified goals in patients with specific preexisting cardiovascular risk factors). Proper agent selection, dosing, and scheduling of follow-up should enable maintaining VSP inhibition while avoiding the complications associated with excessive or prolonged elevation in BP.

VEGF-A165b is cytoprotective and antiangiogenic in the retina

PURPOSE

A number of key ocular diseases, including diabetic retinopathy and age-related macular degeneration, are characterized by localized areas of epithelial or endothelial damage, which can ultimately result in the growth of fragile new blood vessels, vitreous hemorrhage, and retinal detachment. VEGF-A(165), the principal neovascular agent in ocular angiogenic conditions, is formed by proximal splice site selection in its terminal exon 8. Alternative splicing of this exon results in an antiangiogenic isoform, VEGF-A(165)b, which is downregulated in diabetic retinopathy. Here the authors investigate the antiangiogenic activity of VEGF(165)b and its effect on retinal epithelial and endothelial cell survival.

METHODS

VEGF-A(165)b was injected intraocularly in a mouse model of retinal neovascularization (oxygen-induced retinopathy [OIR]). Cytotoxicity and cell migration assays were used to determine the effect of VEGF-A(165)b.

RESULTS

VEGF-A(165)b dose dependently inhibited angiogenesis (IC(50), 12.6 pg/eye) and retinal endothelial migration induced by 1 nM VEGF-A(165) across monolayers in culture (IC(50), 1 nM). However, it also acts as a survival factor for endothelial cells and retinal epithelial cells through VEGFR2 and can stimulate downstream signaling. Furthermore, VEGF-A(165)b injection, while inhibiting neovascular proliferation in the eye, reduced the ischemic insult in OIR (IC(50), 2.6 pg/eye). Unlike bevacizumab, pegaptanib did not interact directly with VEGF-A(165)b.

CONCLUSIONS

The survival effects of VEGF-A(165)b signaling can protect the retina from ischemic damage. These results suggest that VEGF-A(165)b may be a useful therapeutic agent in ischemia-induced angiogenesis and a cytoprotective agent for retinal pigment epithelial cells.

Enhanced matrix metalloproteinase activity in the spontaneously hypertensive rat: VEGFR-2 cleavage, endothelial apoptosis, and capillary rarefaction

Besides an elevated blood pressure, the spontaneously hypertensive rat (SHR) has multiple microvascular complications including endothelial apoptosis with capillary rarefaction. The SHR also has elevated levels of proteolytic (e.g. matrix metalloproteinase, MMP) activity and apoptosis in microvascular cells compared to its normotensive control, but the specific enzymes involved and the molecular mechanism for apoptosis are unknown. We hypothesize that selected MMPs cleave the extracellular domain of vascular endothelial growth factor receptor-2 (VEGFR-2), which in turn causes endothelial apoptosis and capillary rarefaction. Zymographic analysis shows that gelatinase (MMP-2 and MMP-9) and matrilysin (MMP-7) activities are significantly enhanced in SHR plasma. The SHR has lower levels of the extracellular domains of VEGFR-2 in cardiac microvessels. Furthermore, application of plasma from the SHR, or purified MMP-9 and MMP-7 to naïve cells causes cleavage of the extracellular domain of VEGFR-2. The receptor cleavage was blocked by broad-acting MMP inhibitors (GM6001 1 microM, EDTA 10 mM, or doxycycline 11.3 microM). Chronic MMP inhibition (doxycycline, 5.4 mg/kg/day, 24 weeks) attenuated VEGFR-2 cleavage, endothelial apoptosis, and capillary rarefaction in the SHR. These results suggest elevated plasma MMP activities may cleave VEGFR-2, resulting in endothelial apoptosis and capillary rarefaction in the SHR.

Steroid-resistant lymphatic remodeling in chronically inflamed mouse airways

Angiogenesis and lymphangiogenesis participate in many inflammatory diseases, and their reversal is thought to be beneficial. However, the extent of reversibility of vessel remodeling is poorly understood. We exploited the potent anti-inflammatory effects of the corticosteroid dexamethasone to test the preventability and reversibility of vessel remodeling in Mycoplasma pulmonis-infected mice using immunohistochemistry and quantitative RT-PCR. In this model robust immune responses drive rapid and sustained changes in blood vessels and lymphatics. In infected mice not treated with dexamethasone, capillaries enlarged into venules expressing leukocyte adhesion molecules, sprouting angiogenesis and lymphangiogenesis occurred, and the inflammatory cytokines tumor necrosis factor and interleukin-1 increased. Concurrent dexamethasone treatment largely prevented the remodeling of blood vessels and lymphatics. Dexamethasone also significantly reduced cytokine expression, bacterial burden, and leukocyte influx into airways and lungs over 4 weeks of infection. In contrast, when infection was allowed to proceed untreated for 2 weeks and then was treated with dexamethasone for 4 weeks, most blood vessel changes reversed but lymphangiogenesis did not, suggesting that different survival mechanisms apply. Furthermore, dexamethasone significantly reduced the bacterial burden and influx of lymphocytes but not of neutrophils or macrophages or cytokine expression. These findings show that lymphatic remodeling is more resistant than blood vessel remodeling to corticosteroid-induced reversal. We suggest that lymphatic remodeling that persists after the initial inflammatory response has resolved may influence subsequent inflammatory episodes in clinical situations.

Rapid development of hypertension and proteinuria with cediranib, an oral vascular endothelial growth factor receptor inhibitor

BACKGROUND AND OBJECTIVES

Hypertension and proteinuria are common but poorly understood renal toxicities of vascular endothelial growth factor (VEGF) receptor signaling pathway inhibitors. In this phase II study of cediranib (AZD2171) for recurrent epithelial ovarian cancer, the time course and severity of BP changes and proteinuria were characterized.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

46 women ages 41 to 77 years were treated with cediranib. 26% had baseline hypertension. Twice-daily BP was recorded. Urinalyses were performed every 2 weeks, and in some patients proteinuria was further quantified.

RESULTS

31 women (67%) developed hypertension by day 3; 87% by the end of the study. 43% developed grade > or =3 hypertension. Mean systolic BP increase over 3 days was 18 mmHg. Women above the mean age (> or =57 years) had a larger rise in systolic BP by day 3 (15.9 versus 7.0 mmHg). 14 women developed proteinuria. There was a dose response (45 versus 30 mg daily). Proteinuria also developed rapidly, with 7 of 14 women developing proteinuria within 2 weeks. Only 7 of 20 women who developed grade 3 hypertension developed proteinuria.

CONCLUSIONS

Cediranib induced a rapid but variable rise in BP within 3 days of initiation in most patients. Proteinuria was common and also developed rapidly. The rapid development of hypertension suggests that acute inhibition of VEGF-dependent vasodilation might explain the BP rise with VEGF inhibitors. Clinicians must be vigilant in early detection and management of toxicities of this expanding drug class, especially in older patients.

Bronchial Fistula Associated with Sunitinib in a Patient Previously Treated with Radiation Therapy

Objective:

To report a case of bronchial fistula associated with sunitinib in a patient previously treated with radiation therapy.

Case Summary:

A 40-year-old man with renal cell cancer diagnosed in 2005 and initially treated by radical nephrectomy presented in March 2007 with a recurrence with cerebral, mediastinal, and lung metastases. A thoracic computed tomography (CT) scan showed a subcarinal tumor obstructing the bronchus intermedius. The patient was initially treated with cerebral and thoracic radiotherapy and then with sunitinib 50 mg/day (4 weeks on, 2 weeks off). Two months after the beginning of treatment, a CT scan revealed a dramatic reduction in the size of the tumor, associated with a bronchial fistula. This was confirmed by flexible bronchoscopy, which showed complete necrosis of the tumor and a large perforation of the bronchus intermedius. Sunitinib was immediately withdrawn and antibiotic prophylaxis was instituted. It was not possible to place an endobronchial stent. Two weeks later, flexible bronchoscopy revealed the reappearance of a yellowish mass protruding into the bronchus intermedius (40% obstruction). A few months later, the obstruction of the bronchus intermedius progressed to 90% and was associated with a contralateral obstruction of the left mainstem bronchus (20%). A rigid bronchoscopy was then performed to clear the obstruction and an endobronchial stent was placed, with satisfactory initial results. In February 2008, the patient presented with new bronchial obstruction under the endobronchial stent but refused a rigid bronchoscopy and died in March 2008.

Discussion:

Sunitinib, a multitarget tyrosine kinase inhibitor with antiangiogenic and antitumoral activities, has been approved for the treatment of advanced renal cell carcinoma. This treatment is generally well tolerated. Serious complications may occur, however. According to the Naranjo probability scale, the bronchial fistula was possibly related to sunitinib treatment.

Conclusions:

This is a rare case of a bronchial perforation leading to a fistula associated with sunitinib treatment after mediastinal radiation therapy. Clinicians may consider strict follow-up of patients with proximal lung metastases treated with sunitinib (CT scan and, if appropriate, placement of an endobronchial stent).