Susan M. Dallabrida

Cardiotoxicity associated with tyrosine kinase inhibitor sunitinib

BACKGROUND Sunitinib, a multitargeted tyrosine-kinase inhibitor, which is approved by both US and European Commission regulatory agencies for clinical use, extends survival of patients with metastatic renal-cell carcinoma and gastrointestinal stromal tumours, but concerns have arisen about its cardiac safety. We therefore assessed the cardiovascular risk associated with sunitinib in patients with metastatic gastrointestinal stromal tumours. METHODS We retrospectively reviewed all cardiovascular events in 75 patients with imatinib-resistant, metastatic, gastrointestinal stromal tumours who had been enrolled in a phase I/II trial investigating the efficacy of sunitinib. The composite cardiovascular endpoint was cardiac death, myocardial infarction, and congestive heart failure. We also examined sunitinibs effects on left ventricular ejection fraction (LVEF) and blood pressure. We investigated potential mechanisms of sunitinib-associated cardiac effects by studies in isolated rat cardiomyocytes and in mice. FINDINGS Eight of 75 (11%) patients given repeating cycles of sunitinib in the phase I/II trial had a cardiovascular event, with congestive heart failure recorded in six of 75 (8%). Ten of 36 (28%) patients treated at the approved sunitinib dose had absolute LVEF reductions in ejection fraction (EF) of at least 10%, and seven of 36 (19%) had LVEF reductions of 15 EF% or more. Sunitinib induced increases in mean systolic and diastolic blood pressure, and 35 of 75 (47%) individuals developed hypertension (>150/100 mm Hg). Congestive heart failure and left ventricular dysfunction generally responded to sunitinib being withheld and institution of medical management. Sunitinib caused mitochondrial injury and cardiomyocyte apoptosis in mice and in cultured rat cardiomyocytes. INTERPRETATION Left ventricular dysfunction might be due, in part, to direct cardiomyocyte toxicity, exacerbated by hypertension. Patients treated with sunitinib should be closely monitored for hypertension and LVEF reduction, especially those with a history of coronary artery disease or cardiac risk factors.

Adipose tissue mass can be regulated through the vasculature

Tumor growth is angiogenesis dependent. We hypothesized that nonneoplastic tissue growth also depends on neovascularization. We chose adipose tissue as an experimental system because of its remodeling capacity. Mice from different obesity models received anti-angiogenic agents. Treatment resulted in dose-dependent, reversible weight reduction and adipose tissue loss. Marked vascular remodeling was evident in adipose tissue sections, which revealed decreased endothelial proliferation and increased apoptosis in treated mice compared with controls. Continuous treatment maintained mice near normal body weights for age without adverse effects. Metabolic adaptations in food intake, metabolic rate, and energy substrate utilization were associated with anti-angiogenic weight loss. We conclude that adipose tissue mass is sensitive to angiogenesis inhibitors and can be regulated by its vasculature.

Vascular Progenitor Cells Isolated From Human Embryonic Stem Cells Give Rise to Endothelial and Smooth Muscle–Like Cells and Form Vascular Networks In Vivo

We report that human embryonic stem cells contain a population of vascular progenitor cells that have the ability to differentiate into endothelial-like and smooth muscle (SM)-like cells. Vascular progenitor cells were isolated from EBs grown in suspension for 10 days and were characterized by expression of the endothelial/hematopoietic marker CD34 (CD34+ cells). When these cells are subsequently cultured in EGM-2 (endothelial growth medium) supplemented with vascular endothelial growth factor-165 (50 ng/mL), they give rise to endothelial-like cells characterized by a cobblestone cell morphology, expression of endothelial markers (platelet endothelial cell-adhesion molecule-1, CD34, KDR/Flk-1, vascular endothelial cadherin, von Willebrand factor), incorporation of acetylated low-density lipoprotein, and formation of capillary-like structures when placed in Matrigel. In contrast, when CD34+ cells are cultured in EGM-2 supplemented with platelet-derived growth factor-BB (50 ng/mL), they give rise to SM-like cells characterized by spindle-shape morphology, expression of SM cell markers (&agr;-SM actin, SM myosin heavy chain, calponin, caldesmon, SM &agr;-22), and the ability to contract and relax in response to common pharmacological agents such as carbachol and atropine but rarely form capillary-like structures when placed in Matrigel. Implantation studies in nude mice show that both cell types contribute to the formation of human microvasculature. Some microvessels contained mouse blood cells, which indicates functional integration with host vasculature. Therefore, the vascular progenitors isolated from human embryonic stem cells using methods established in the present study could provide a means to examine the mechanisms of endothelial and SM cell development, and they could also provide a potential source of cells for vascular tissue engineering.

Angiopoietin-1 Promotes Cardiac and Skeletal Myocyte Survival Through Integrins

Cardiac myocyte loss, regardless of insult, can trigger compensatory myocardial remodeling leading to heart failure. Identifying mediators of cardiac myocyte survival may advance clinical efforts toward myocardial preservation. Angiopoietin-1 limits ischemia-induced cardiac injury. This benefit is ascribed to angiogenesis because the receptor, tie2, is largely endothelial-specific. We propose that direct, non-tie2 interactions of angiopoietin-1 on cardiac myocytes contribute to this cardioprotection. We found that mouse C2C12 skeletal myocytes lack tie2, yet dose-dependently adhered to angiopoietin-1 and angiopoietin-2 similarly to laminin, fibronectin, vitronectin, and more than to collagen-I, -III, and -IV. Adhesion was divalent cation-mediated (Mn2+, Ca2+, not Mg2+), blocked with EDTA/EGTA, RGD-based peptides, and select integrin subunit antibodies. Similar findings were obtained with human skeletal myocytes (HSMs) and freshly isolated rat neonatal cardiac myocytes (NCMs). Furthermore, angiopoietin-1 conferred significant survival advantage exceeding that of most cell matrices, which was not fully explained by differences in cell adhesion. Angiopoietin-1 promoted survival of serum-starved C2C12, HSM, and NCM (MTT, trypan blue) and prevented taxol-induced apoptosis (caspase-3). Immobilized and soluble angiopoietin-1 phosphorylated AktS473 and MAPKp42/44, (not FAKY397) in C2C12 more than in endothelial cells and more than did angiopoietin-2 or cell matrices. EDTA, RGD-based peptides, and some integrin antibodies blocked these responses. Angiopoietin-1 activated HSM and NCM AktS473 and MAPKp42/44 survival pathways. We propose that this novel function contributes to developmental and cardioprotective actions of angiopoietin-1 presently attributed to vascular effects alone. Angiopoietin-1 may prove therapeutically valuable in cardiac remodeling by supporting myocyte viability and preserving pump function. The full text of this article is available online at http://circres.ahajournals.org.

Endostatin lowers blood pressure via nitric oxide and prevents hypertension associated with VEGF inhibition

Antiangiogenesis therapy has become a vital part of the armamentarium against cancer. Hypertension is a dose-limiting toxicity for VEGF inhibitors. Thus, there is a pressing need to address the associated adverse events so these agents can be better used. The hypertension may be mediated by reduced NO bioavailability resulting from VEGF inhibition. We proposed that the hypertension may be prevented by coadministration with endostatin (ES), an endogenous angiogenesis inhibitor with antitumor effects shown to increase endothelial NO production in vitro. We determined that Fc-conjugated ES promoted NO production in endothelial and smooth muscle cells. ES also lowered blood pressure in normotensive mice and prevented hypertension induced by anti-VEGF antibodies. This effect was associated with higher circulating nitrate levels and was absent in eNOS-knockout mice, implicating a NO-mediated mechanism. Retrospective study of patients treated with ES in a clinical trial revealed a small but significant reduction in blood pressure, suggesting that the findings may translate to the clinic. Coadministration of ES with VEGF inhibitors may offer a unique strategy to prevent drug-related hypertension and enhance antiangiogenic tumor suppression.

Subjects with osteoarthritis can easily use a handheld touch screen electronic device to report medication use: qualitative results from a usability study

Objectives Electronic data capture is increasingly used to improve collection of patient-reported outcome measures in clinical trials and care. The validation of electronic patient-reported outcome devices requires information on patient preference and ease of use. This study conducted usability testing for a General Symptom Questionnaire and Medication Module™ on a handheld device for subjects with osteoarthritis (OA) to determine whether subjects can report on their symptoms and medication use using an electronic diary. Methods Nine subjects with OA participating in a large US mode equivalency study were surveyed independently in this study. Subjects completed a General Symptom Questionnaire and Medication Module™ using the LogPad® LW handheld device. Demographic and technology use information was collected, and the subjects were queried on device usability. Results Subjects reported that the handheld device was easy to use and that they were able to complete a General Symptom Questionnaire and Medication Module™ with little or no assistance. They did not report any issues with the screen or size of the device. Subjects were willing to travel with the device to complete electronic diaries at home or in public. Participants indicated that they would be able to use the handheld device to answer questions during a clinical trial. Subjects with OA experienced no physical discomfort during completion of either questionnaire. Conclusion The General Symptom Questionnaire and Medication Module™ were usable and acceptable to subjects with OA on a handheld device. This was consistent regardless of previous experience and confidence with technology, despite the potential physical restrictions for an OA cohort.

870-6 The role of angiopoietin-1 in physiologic and pathologic cardiac remodeling and in promoting cardiac myocyte survival

Background: Recent studies indicated increased plasma oxypurine (hypoxanthine/xanthine/uric acid) levels as an independent risk factor for worsened heart failure, suggesting oxypurine potential role for diastolic dysfunction. Methods: We used a canine model of enhanced diastolic failure (1 week AII infusion + subacute tachypacing; 250 bpm for 48 hrs; AII+P), displaying pronounced diastolic stiffening and marked metalloproteinase (MMP) activation. MMP inhibition (MMPI) prevents diastolic stiffening, without influencing collagen content/subtype or cross-linking. Here we tested whether AII+P (n=7) enhances AMP catabolism to increase cardiac nucleoside/ oxypurine and diastolic stiffening, assessing the ability of MMPI to prevent these changes. Results: AII+P raised diastolic chamber stiffness and end-diastolic pressure ~100% and markedly activated gelatinases MMP-9 and MMP-2 (abundance and in situ assays). With AII+P, ATP declined while AMP catabolites increased: nucleotides (inosine, adenosine) raised from 254±94 to 1700± 363nmol/g (p<0.005), and oxypurines from 100±20 to 666± 67 nmol/g (p<0.001). MMP inhibition (PD-166793, 5 mg/kg/day, n=9) prevented diastolic stiffening as well as MMP-9 and -2 activation, and countered the rise in both nucleotides (804± 35 nmol/g, p<0.02 vs AII-P) and oxypurines (397± 17, p<0.001 vs AII-P). MMPI directly inhibited in vitro AMP deaminase activity in a dose-dependent manner but did not affect other steps of the purine catabolism cascade. In AII+P hearts hallmarks of oxidative stress were evident: malondialdehyde (lipid peroxidation index) raised from 0.31±0.1 (controls) to 6.7±2.3 nmol/g (p<0.01) while antioxidant levels (ascorbate and reduced glutathione) significantly declined. However, MMPI did not mitigate AII+P-induced oxidative stress (MDA = 6.1±1.3). Conclusions: Diastolic stiffening is associated with a rise in myocardial content of AMPbreakdown byproducts (i.e. nucleosides and oxypurines). MMP inhibition fully prevents diastolic stiffening by limiting this accumulation, direcly interfering with AMP catabolic activities (i.e.AMP deaminase), independently from the extent of cardiac oxidative stress.