Normalization of the vasculature for treatment of cancer and other diseases

Targeting tumor microenvironment with silibinin: promise and potential for a translational cancer chemopreventive strategy

Tumor microenvironment (TME) refers to the dynamic cellular and extra-cellular components surrounding tumor cells at each stage of the carcinogenesis. TME has now emerged as an integral and inseparable part of the carcinogenesis that plays a critical role in tumor growth, angiogenesis, epithelial to mesenchymal transition (EMT), invasion, migration and metastasis. Besides its vital role in carcinogenesis, TME is also a better drug target because of its relative genetic stability with lesser probability for the development of drug-resistance. Several drugs targeting the TME (endothelial cells, macrophages, cancer-associated fibroblasts, or extra-cellular matrix) have either been approved or are in clinical trials. Recently, non-steroidal anti-inflammatory drugs targeting inflammation were reported to also prevent several cancers. These exciting developments suggest that cancer chemopreventive strategies targeting both tumor and TME would be better and effective towards preventing, retarding or reversing the process of carcinogenesis. Here, we have reviewed the effect of a well established hepatoprotective and chemopreventive agent silibinin on cellular (endothelial, fibroblast and immune cells) and non-cellular components (cytokines, growth factors, proteinases etc.) of the TME. Silibinin targets TME constituents as well as their interaction with cancer cells, thereby inhibiting tumor growth, angiogenesis, inflammation, EMT, and metastasis. Silibinin is already in clinical trials, and based upon completed studies we suggest that its chemopreventive effectiveness should be verified through its effect on biological end points in both tumor and TME. Overall, we believe that the chemopreventive strategies targeting both tumor and TME have practical and translational utility in lowering the cancer burden.

Netrin-4 promotes mural cell adhesion and recruitment to endothelial cells

Netrins are secreted molecules involved in axon guidance and angiogenesis. We previously showed that Netrin-4 acts as an anti-angiogenic factor by inhibiting endothelial cell (EC) functions. In this study, we investigated the effects of Netrin-4 on vascular smooth muscle cell (VSMC) activity in vitro and in vivo. We show that exogenous Netrin-4 stimulated VSMC adhesion and migration, and increased their coverage on EC tubes (grown on a Matrigel substrate). siRNA knock-down of endogenous Netrin-4 expression in VSMC decreased their recruitment to EC tubes. VSMC expressed Netrin-4 and three of the six Netrin-1 cognate receptors: DCC, Neogenin, and Unc5B. Silencing of these receptors reduced Netrin-4 adhesion to VSMC, strongly suggesting that these receptors were involved in the recruitment process. We previously showed that Netrin-4 overexpression in PC3 cancer cells delayed tumor growth in a model of subcutaneous xenograft by reducing tumor vessel density. Here, we show that Netrin-4 overexpression improved tumor blood vessel structure and increased VSMC coverage. Thus, Netrin-4 induced mural cell recruitment may play a role in the inhibition of tumor growth. Our data suggest that Netrin-4 is important for blood vessel normalization through the regulation of both endothelial and perivascular cells.

Heterogeneity of tumor vasculature and antiangiogenic intervention: insights from MR angiography and DCE-MRI

PURPOSE

Solid tumor vasculature is highly heterogeneous, which presents challenges to antiangiogenic intervention as well as the evaluation of its therapeutic efficacy. The aim of this study is to evaluate the spatial tumor vascular changes due to bevacizumab/paclitaxel therapy using a combination approach of MR angiography and DCE-MRI method.

EXPERIMENTAL DESIGN

Tumor vasculature of MCF-7 breast tumor mouse xenografts was studied by a combination of MR angiography and DCE-MRI with albumin-Gd-DTPA. Tumor macroscopic vasculature was extracted from the early enhanced images. Tumor microvascular parameters were obtained from the pharmacokinetic modeling of the DCE-MRI data. A spatial analysis of the microvascular parameters based on the macroscopic vasculature was used to evaluate the changes of the heterogeneous vasculature induced by a 12 day bevacizumab/paclitaxel treatment in mice bearing MCF-7 breast tumor.

RESULTS

Macroscopic vessels that feed the tumors were not affected by the bevacizumab/paclitaxel combination therapy. A higher portion of the tumors was within close proximity of these macroscopic vessels after the treatment, concomitant with tumor growth retardation. There was a significant decrease in microvascular permeability and vascular volume in the tumor regions near these vessels.

CONCLUSION

Bevacizumab/paclitaxel combination therapy did not block the blood supply to the MCF-7 breast tumor. Such finding is consistent with the modest survival benefits of adding bevacizumab to current treatment regimens for some types of cancers.

The effect of the anti-angiogenic drug sunitinib malate on the vascular architecture of oral squamous cell carcinoma

The effects of anti-angiogenic therapies in guiding tumor angioarchitecture prompted us to examine the modifications in the vascular network of the oral squamous cell carcinoma (SCC) produced by the multitargeted tyrosine kinase inhibitor sunitinib malate. Twelve Syrian hamsters had their right buccal pouches submitted to tumor induction with dimethylbenzanthracene and carbamide peroxide for 55 days. The animals were then divided into two groups of six animals each; group I was treated with sunitinib malate and group II (control) was remained untreated. After 4 weeks, the hamsters had their vascular networks casted by Mercox® resin and analyzed by scanning electron microscopy. The qualitative study of the vascular network of the control tumor-bearing pouches showed images of intussusception and sprouting angiogenesis, flattened blood vessels, abrupt variations in their diameter, and a tortuous course. The samples treated with sunitinib exhibited a qualitative reduction of the signs of vascular proliferation. In addition, these casts presented an attenuation of the morphological features observed in the untreated tumor-bearing pouches. Quantitative analysis demonstrated that the pouches treated with sunitinib did not show a decrease (P > 0.05) in the vascular diameter and intervessel distances when compared with the control group. The results of the present study suggest that sunitinib may act on the vascular network of oral SCC, normalizing the blood vessels. However, further experiments should be performed in order to determine a judicious dose of this anti-angiogenic therapy.

T-type calcium channels blockers as new tools in cancer therapies

T-type calcium channels are involved in a multitude of cellular processes, both physiological and pathological, including cancer. T-type channels are also often aberrantly expressed in different human cancers and participate in the regulation of cell cycle progression, proliferation, migration, and survival. Here, we review the recent literature and discuss the controversies, supporting the role of T-type Ca(2+) channels in cancer cells and the proposed use of channels blockers as anticancer agents. A growing number of reports show that pharmacological inhibition or RNAi-mediated downregulation of T-type channels leads to inhibition of cancer cell proliferation and increased cancer cell death. In addition to a single agent activity, experimental results demonstrate that T-type channel blockers enhance the anticancer effects of conventional radio- and chemotherapy. At present, the detailed biological mechanism(s) underlying the anticancer activity of these channel blockers is not fully understood. Recent findings and ideas summarized here identify T-type Ca(2+) channels as a molecular target for anticancer therapy and offer new directions for the design of novel therapeutic strategies employing channels blockers. Physiological relevance: T-type calcium channels are often aberrantly expressed or deregulated in cancer cells, supporting their proliferation, survival, and resistance to treatment; therefore, T-type Ca(2+) channels could be attractive molecular targets for anticancer therapy.

Intermittent dosing of axitinib combined with chemotherapy is supported by (18)FLT-PET in gastrointestinal tumours

Background:

We evaluated week-on/week-off axitinib dosing plus chemotherapy in patients with gastrointestinal tumours, including tumour thymidine uptake by fluorine-18 3′-deoxy-3′-fluorothymidine positron emission tomography (¹⁸FLT-PET).

Methods:

During a lead-in period, patients received twice daily (b.i.d.) axitinib 7 mg (n=3) or 10 mg (n=18) for 7 days followed by a 7-day dosing interruption; serial ¹⁸FLT-PET scans were performed before day 1 and on days 7, 10, and 14. Axitinib plus FOLFIRI or FOLFOX was then administered in 2-week cycles; axitinib was interrupted on day 10 of each cycle for 7 days.

Results:

The maximum tolerated dose of axitinib was 10 mg b.i.d., in a week-on/week-off schedule, combined with FOLFIRI or FOLFOX. Common all-causality grade 3 adverse events were neutropenia (38%), hypertension (33%), and fatigue (29%). Of 21 patients, 2 (10%) had a partial response and 12 (57%) had stable disease. Following 7 days of continuous axitinib dosing, tumour ¹⁸FLT uptake decreased –49% from baseline and recovered to –28% and –17% from baseline, respectively, after 3 and 7 days of axitinib interruption.

Conclusion:

Axitinib administered in a week-on/week-off schedule combined with FOLFIRI or FOLFOX is supported by ¹⁸FLT-PET data and was well tolerated in patients with gastrointestinal tumours.

Stimulation of G protein-coupled bile acid receptor enhances vascular endothelial barrier function via activation of protein kinase A and Rac1

Bile acids are end products of cholesterol metabolism, and they constantly exist at high concentrations in the blood. Since vascular endothelial cells express G protein-coupled bile acid receptor (GPBAR), bile acids potentially modulate endothelial function. Here, we investigated whether and how GPBAR agonism affects endothelial barrier function. In bovine aortic endothelial cells (BAECs), treatment with a GPBAR agonist, taurolithocholic acid (TLCA) increased the transendothelial electrical resistance. In addition, TLCA suppressed the thrombin-induced dextran infiltration through the endothelial monolayer. Knockdown of GPBAR abolished the inhibitory effect of TLCA on hyperpermeability. These results indicate that stimulation of GPBAR enhances endothelial barrier function. TLCA increased intracellular cAMP production in BAECs. Inhibition of protein kinase A (PKA) or Rac1 significantly attenuated the TLCA-induced endothelial barrier protection. TLCA induced cortical actin polymerization, which was attenuated by a Rac1 inhibitor. In vivo, local administration of TLCA into the mouse ear significantly inhibited vascular leakage and edema formation induced by croton oil or vascular endothelial growth factor. These results indicate that stimulation of GPBAR enhances endothelial barrier function by cAMP/PKA/Rac1-dependent cytoskeletal rearrangement.

Normalization of the tumor microenvironment: evidence for tissue inhibitor of metalloproteinase-2 as a cancer therapeutic

Matrix metalloproteinases (MMPs) are members of the Metzincin family of proteases responsible for degrading the extracellular matrix (ECM). In early studies, MMP degradation of the sub-epithelial basement membrane was thought to be tumor cell autonomous and contribute to the invasive behavior of malignant cells. It is now recognized that MMPs have multiple roles that can either promote or inhibit tumor progression and metastasis. The endogenous inhibitors of the MMPs are the tissue inhibitors of metalloproteinases (TIMPs). Early studies on the tumor microenvironment revealed TIMP function to be principally through the inhibition of MMPs, thereby blocking tumor cell migration and invasion. However, data from a number of laboratories are now reporting that TIMPs have direct cellular functions, independent of their MMP inhibitory activity. The TIMPs can modulate normal tissue physiology and development, as well as pathology and progression in a variety of acute and chronic disease states. In this review, we briefly describe the role of MMPs and TIMPs in ECM turnover and formation of the tumor microenvironment. Based on the evidence presented, we postulate that TIMP-2 and other soluble components of the normal ECM may provide a novel therapeutic approach to cancer treatment through "normalization" of the tumor microenvironment.

Isolation and culture of primary mouse brain endothelial cells

Blood vessels in the central nervous system (CNS) are unique in forming the blood-brain barrier (BBB), which confers high electrical resistance and low permeability properties, thus protecting neural cells from potentially harmful blood components. Endothelial cells, which form the inner cellular lining of all blood vessels, play a critical role in this process by forming tight adhesive interactions between each other. To study the properties of primary brain endothelial cells (BECs), a number of different methods have been described. In this chapter, we present a relatively simple method that produces high numbers of primary mouse BECs that are highly pure (greater than 99 % CD31-positive). In addition, we also describe an immunocytochemical approach to demonstrate the endothelial purity of these cultures.

Cilengitide-induced temporal variations in transvascular transfer parameters of tumor vasculature in a rat glioma model: identifying potential MRI biomarkers of acute effects

Increased efficacy of radiotherapy (RT) 4-8 h after Cilengitide treatment has been reported. We hypothesized that the effects of Cilengitide on tumor transvascular transfer parameters might underlie, and thus predict, this potentiation. Athymic rats with orthotopic U251 glioma were studied at ~21 days after implantation using dynamic contrast-enhanced (DCE)-MRI. Vascular parameters, viz: plasma volume fraction (v_p), forward volume transfer constant (K^trans) and interstitial volume fraction (v_e) of a contrast agent, were determined in tumor vasculature once before, and again in cohorts 2, 4, 8, 12 and 24 h after Cilengitide administration (4 mg/kg; N = 31; 6-7 per cohort). Perfusion-fixed brain sections were stained for von Willebrand factor to visualize vascular segments. A comparison of pre- and post-treatment parameters showed that the differences between MR indices before and after Cilengitide treatment pivoted around the 8 h time point, with 2 and 4 h groups showing increases, 12 and 24 h groups showing decreases, and values at the 8 h time point close to the baseline. The vascular parameter differences between group of 2 and 4 h and group of 12 and 24 h were significant for K^trans (p = 0.0001 and v_e (p = 0,0271). Vascular staining showed little variation with time after Cilengitide. The vascular normalization occurring 8 h after Cilengitide treatment coincided with similar previous reports of increased treatment efficacy when RT followed Cilengitide by 8 h. Pharmacological normalization of vasculature has the potential to increase sensitivity to RT. Evaluating acute temporal responses of tumor vasculature to putative anti-angiogenic drugs may help in optimizing their combination with other treatment modalities.

Influence of soluble or matrix-bound isoforms of vascular endothelial growth factor-A on tumor response to vascular-targeted strategies

Antiangiogenic therapy based on blocking the actions of vascular endothelial growth factor-A (VEGF) can lead to "normalization" of blood vessels in both animal and human tumors. Differential expression of VEGF isoforms affects tumor vascular maturity, which could influence the normalization process and response to subsequent treatment. Fibrosarcoma cells expressing only VEGF120 or VEGF188 isoforms were implanted either subcutaneously (s.c.) or in dorsal skin-fold "window" chambers in SCID mice. VEGF120 was associated with vascular fragility and hemorrhage. Tumor-bearing mice were treated with repeat doses of SU5416, an indolinone receptor tyrosine kinase inhibitor with activity against VEGFR-2 and proven preclinical ability to induce tumor vascular normalization. SU5416 reduced vascularization in s.c. implants of both VEGF120 and VEGF188 tumors. However, in the window chamber, SU5416 treatment increased red cell velocity in VEGF120 (representing vascular normalization) but not VEGF188 tumors. SU5416 treatment had no effect on growth or necrosis levels in either tumor type but tended to counteract the increase in interstitial fluid pressure seen with growth of VEGF120 tumors. SU5416 pretreatment resulted in the normally fragile blood vessels in VEGF120-expressing tumors becoming resistant to the vascular damaging effects of the tubulin-binding vascular disrupting agent (VDA), combretastatin A4 3-O-phosphate (CA4P). Thus, vascular normalization induced by antiangiogenic treatment can reduce the efficacy of subsequent VDA treatment. Expression of VEGF120 made tumors particularly susceptible to vascular normalization by SU5416, which in turn made them resistant to CA4P. Therefore, VEGF isoform expression may be useful for predicting response to both antiangiogenic and vascular-disrupting therapy.

Tumor cell-mediated neovascularization and lymphangiogenesis contrive tumor progression and cancer metastasis

Robust neovascularization and lymphangiogenesis have been found in a variety of aggressive and metastatic tumors. Endothelial sprouting angiogenesis is generally considered to be the major mechanism by which new vasculature forms in tumors. However, increasing evidence shows that tumor vasculature is not solely composed of endothelial cells (ECs). Some tumor cells acquire processes similar to embryonic vasculogenesis and produce new vasculature through vasculogenic mimicry, trans-differentiation of tumor cells into tumor ECs, and tumor cell-EC vascular co-option. In addition, tumor cells secrete various vasculogenic factors that induce sprouting angiogenesis and lymphangiogenesis. Vasculogenic tumor cells actively participate in the formation of vascular cancer stem cell niche and a premetastatic niche. Therefore, tumor cell-mediated neovascularization and lymphangiogenesis are closely associated with tumor progression, cancer metastasis, and poor prognosis. Vasculogenic tumor cells have emerged as key players in tumor neovascularization and lymphangiogenesis and play pivotal roles in tumor progression and cancer metastasis. However, the mechanisms underlying tumor cell-mediated vascularity as they relate to tumor progression and cancer metastasis remain unclear. Increasing data have shown that various intrinsic and extrinsic factors activate oncogenes and vasculogenic genes, enhance vasculogenic signaling pathways, and trigger tumor neovascularization and lymphangiogenesis. Collectively, tumor cells are the instigators of neovascularization. Therefore, targeting vasculogenic tumor cells, genes, and signaling pathways will open new avenues for anti-tumor vasculogenic and metastatic drug discovery. Dual targeting of endothelial sprouting angiogenesis and tumor cell-mediated neovascularization and lymphangiogenesis may overcome current clinical problems with anti-angiogenic therapy, resulting in significantly improved anti-angiogenesis and anti-cancer therapies.

SILAC-based proteomics of human primary endothelial cell morphogenesis unveils tumor angiogenic markers

Proteomics has been successfully used for cell culture on dishes, but more complex cellular systems have proven to be challenging and so far poorly approached with proteomics. Because of the complexity of the angiogenic program, we still do not have a complete understanding of the molecular mechanisms involved in this process, and there have been no in depth quantitative proteomic studies. Plating endothelial cells on matrigel recapitulates aspects of vessel growth, and here we investigate this mechanism by using a spike-in SILAC quantitative proteomic approach. By comparing proteomic changes in primary human endothelial cells morphogenesis on matrigel to general adhesion mechanisms in cells spreading on culture dish, we pinpoint pathways and proteins modulated by endothelial cells. The cell-extracellular matrix adhesion proteome depends on the adhesion substrate, and a detailed proteomic profile of the extracellular matrix secreted by endothelial cells identified CLEC14A as a matrix component, which binds to MMRN2. We verify deregulated levels of these proteins during tumor angiogenesis in models of multistage carcinogenesis. This is the most in depth quantitative proteomic study of endothelial cell morphogenesis, which shows the potential of applying high accuracy quantitative proteomics to in vitro models of vessel growth to shed new light on mechanisms that accompany pathological angiogenesis. The mass spectrometry proteomics data have been deposited to the ProteomeXchange Consortium with the data set identifier PXD000359.

Enhancing microvascular formation and vessel maturation through temporal control over multiple pro-angiogenic and pro-maturation factors

Therapeutic stimulation of angiogenesis to re-establish blood flow in ischemic tissues offers great promise as a treatment for patients suffering from cardiovascular disease or trauma. Since angiogenesis is a complex, multi-step process, different signals may need to be delivered at appropriate times in order to promote a robust and mature vasculature. The effects of temporally regulated presentation of pro-angiogenic and pro-maturation factors were investigated in vitro and in vivo in this study. Pro-angiogenic factors vascular endothelial growth factor (VEGF) and angiopoietin 2 (Ang2) cooperatively promoted endothelial sprouting and pericyte detachment in a three-dimensional in vitro EC-pericyte co-culture model. Pro-maturation factors platelet-derived growth factor B (PDGF) and angiopoietin 1 (Ang1) inhibited the early stages of VEGF- and Ang2-mediated angiogenesis if present simultaneously with VEGF and Ang2, but promoted these behaviors if added subsequently to the pro-angiogenesis factors. VEGF and Ang2 were also found to additively enhance microvessel density in a subcutaneous model of blood vessel formation, while simultaneously administered PDGF/Ang1 inhibited microvessel formation. However, a temporally controlled scaffold that released PDGF and Ang1 at a delay relative to VEGF/Ang2 promoted both vessel maturation and vascular remodeling without inhibiting sprouting angiogenesis. Our results demonstrate the importance of temporal control over signaling in promoting vascular growth, vessel maturation and vascular remodeling. Delivering multiple growth factors in combination and sequence could aid in creating tissue engineered constructs and therapies aimed at promoting healing after acute wounds and in chronic conditions such as diabetic ulcers and peripheral artery disease.

Extracellular regulation of VEGF: isoforms, proteolysis, and vascular patterning

The regulation of vascular endothelial growth factor A (VEGF) is critical to neovascularization in numerous tissues under physiological and pathological conditions. VEGF has multiple isoforms, created by alternative splicing or proteolytic cleavage, and characterized by different receptor-binding and matrix-binding properties. These isoforms are known to give rise to a spectrum of angiogenesis patterns marked by differences in branching, which has functional implications for tissues. In this review, we detail the extensive extracellular regulation of VEGF and the ability of VEGF to dictate the vascular phenotype. We explore the role of VEGF-releasing proteases and soluble carrier molecules on VEGF activity. While proteases such as MMP9 can 'release' matrix-bound VEGF and promote angiogenesis, for example as a key step in carcinogenesis, proteases can also suppress VEGF's angiogenic effects. We explore what dictates pro- or anti-angiogenic behavior. We also seek to understand the phenomenon of VEGF gradient formation. Strong VEGF gradients are thought to be due to decreased rates of diffusion from reversible matrix binding, however theoretical studies show that this scenario cannot give rise to lasting VEGF gradients in vivo. We propose that gradients are formed through degradation of sequestered VEGF. Finally, we review how different aspects of the VEGF signal, such as its concentration, gradient, matrix-binding, and NRP1-binding can differentially affect angiogenesis. We explore how this allows VEGF to regulate the formation of vascular networks across a spectrum of high to low branching densities, and from normal to pathological angiogenesis. A better understanding of the control of angiogenesis is necessary to improve upon limitations of current angiogenic therapies.

Two-wave nanotherapy to target the stroma and optimize gemcitabine delivery to a human pancreatic cancer model in mice

Pancreatic ductal adenocarcinoma (PDAC) elicits a dense stromal response that blocks vascular access because of pericyte coverage of vascular fenestrations. In this way, the PDAC stroma contributes to chemotherapy resistance in addition to causing other problems. In order to improve the delivery of gemcitabine, a first-line chemotherapeutic agent, a PEGylated drug-carrying liposome was developed, using a transmembrane ammonium sulfate gradient to encapsulate the protonated drug up to 20% w/w. However, because the liposome was precluded from entering the xenograft site due to the stromal interference, we developed a first-wave nanocarrier that decreases pericyte coverage of the vasculature through interference in the pericyte recruiting TGF-β signaling pathway. This was accomplished using a polyethyleneimine (PEI)/polyethylene glycol (PEG)-coated mesoporous silica nanoparticle (MSNP) for molecular complexation to a small molecule TGF-β inhibitor, LY364947. LY364947 contains a nitrogen atom that attaches, through H-bonding, to PEI amines with a high rate of efficiency. The copolymer coating also facilitates systemic biodistribution and retention at the tumor site. Because of the high loading capacity and pH-dependent LY364947 release from the MSNPs, we achieved rapid entry of IV-injected liposomes and MSNPs at the PDAC tumor site. This two-wave approach provided effective shrinkage of the tumor xenografts beyond 25 days, compared to the treatment with free drug or gemcitabine-loaded liposomes only. Not only does this approach overcome stromal resistance to drug delivery in PDAC, but it also introduces the concept of using a stepwise engineered approach to address a range of biological impediments that interfere in nanocancer therapy in a spectrum of cancers.

Nanoparticles for combination drug therapy

Nanoparticles have recently emerged as a promising class of carriers for the co-delivery of multiple drugs. Combination therapies of small-molecule drugs are common in clinical practice, and it is anticipated that packaging into single macromolecular carriers will enable drug release in precisely balanced ratios and rates and in selectively targeted tissues and cells. This vast level of pharmacological control is intriguing, especially from the perspective of tailoring personalized treatments with maximized therapeutic synergy for individual patients. Here, we discuss promising formulations and opportunities to employ advanced screening tools and new animal models of disease that can improve chances for successful clinical translation.

hERG1 channels modulate integrin signaling to trigger angiogenesis and tumor progression in colorectal cancer

Angiogenesis is a potential target for cancer therapy. We identified a novel signaling pathway that sustains angiogenesis and progression in colorectal cancer (CRC). This pathway is triggered by β1 integrin-mediated adhesion and leads to VEGF-A secretion. The effect is modulated by the human ether-à-go-go related gene 1 (hERG1) K(+) channel. hERG1 recruits and activates PI3K and Akt. This in turn increases the Hypoxia Inducible Factor (HIF)-dependent transcription of VEGF-A and other tumour progression genes. This signaling pathway has novel features in that the integrin- and hERG1-dependent activation of HIF (i) is triggered in normoxia, especially after CRC cells have experienced a hypoxic stage, (ii) involves NF-kB and (iii) is counteracted by an active p53. Blocking hERG1 switches this pathway off also in vivo, by inhibiting cell growth, angiogenesis and metastatic spread. This suggests that non-cardiotoxic anti-hERG1 drugs might be a fruitful therapeutic strategy to prevent the failure of anti-VEGF therapy.

A systems biology view of blood vessel growth and remodelling

Blood travels throughout the body in an extensive network of vessels – arteries, veins and capillaries. This vascular network is not static, but instead dynamically remodels in response to stimuli from cells in the nearby tissue. In particular, the smallest vessels – arterioles, venules and capillaries – can be extended, expanded or pruned, in response to exercise, ischaemic events, pharmacological interventions, or other physiological and pathophysiological events. In this review, we describe the multi-step morphogenic process of angiogenesis – the sprouting of new blood vessels – and the stability of vascular networks in vivo. In particular, we review the known interactions between endothelial cells and the various blood cells and plasma components they convey. We describe progress that has been made in applying computational modelling, quantitative biology and high-throughput experimentation to the angiogenesis process.

Pushing tumor cells towards a malignant phenotype: stimuli from the microenvironment, intercellular communications and alternative roads

The tumor microenvironment produces different types of stimuli capable of endowing tumor cells with an aggressive behavior that is characterized by increased motility, invasiveness and propensity to metastasize, gain of a tumor-initiating phenotype, and drug resistance. The following classes of stimuli have been reported to promote such a malignant phenotype: (i) solid- or fluid-induced stress; (ii) altered composition of the extracellular matrix; (iii) hypoxia and low pH; (iv) innate and adaptive immune responses; (v) antitumor drugs. The simultaneous presence of more than one of these stimuli, as likely occurs in vivo, may lead to synergistic interactions in the induction of malignant traits. In many cases, the gain of a malignant phenotype is not the result of a direct effect of the stimuli on tumor cells but, rather, a stimulus-promoted cross-talk between tumor cells and other cell types within the tumor microenvironment. This cross-talk is mainly mediated by two classes of molecules: paracrine factors and adhesion receptors. Stimuli that promote a malignant phenotype can promote additional outcomes in tumor cells, including autophagy and cell death. We summarize here the available evidence about the variables that induce tumor cells to take one or the other of these roads in response to the same stimuli. At the end of this review, we address some unanswered questions in this domain and indicate future directions of research.

An integrated understanding of the physiological response to elevated extracellular phosphate

Recent studies have suggested that changes in serum phosphate levels influence pathological states associated with aging such as cancer, bone metabolism, and cardiovascular function, even in individuals with normal renal function. The causes are only beginning to be elucidated but are likely a combination of endocrine, paracrine, autocrine, and cell autonomous effects. We have used an integrated quantitative biology approach, combining transcriptomics and proteomics to define a multi-phase, extracellular phosphate-induced, signaling network in pre-osteoblasts as well as primary human and mouse mesenchymal stromal cells. We identified a rapid mitogenic response stimulated by elevated phosphate that results in the induction of immediate early genes including c-fos. The mechanism of activation requires FGF receptor signaling followed by stimulation of N-Ras and activation of AP-1 and serum response elements. A distinct long-term response also requires FGF receptor signaling and results in N-Ras activation and expression of genes and secretion of proteins involved in matrix regulation, calcification, and angiogenesis. The late response is synergistically enhanced by addition of FGF23 peptide. The intermediate phase results in increased oxidative phosphorylation and ATP production and is necessary for the late response providing a functional link between the phases. Collectively, the results define elevated phosphate, as a mitogen and define specific mechanisms by which phosphate stimulates proliferation and matrix regulation. Our approach provides a comprehensive understanding of the cellular response to elevated extracellular phosphate, functionally connecting temporally coordinated signaling, transcriptional, and metabolic events with changes in long-term cell behavior.

Antibody-functionalized magnetic polymersomes: in vivo targeting and imaging of bone metastases using high resolution MRI

Multifunctional polymersomes loaded with maghemite nanoparticles and grafted with an antibody, directed against human endothelial receptor 2, are developed as novel MRI contrast agents for bone metastasis imaging. Upon administration in mice bearing bone tumor grown from human breast cancer cells, MR images show targeting and enhanced retention of antibody-labeled polymersomes at the tumor site.

Strategies for advancing cancer nanomedicine

Cancer nanomedicines approved so far minimize toxicity, but their efficacy is often limited by physiological barriers posed by the tumour microenvironment. Here, we discuss how these barriers can be overcome through innovative nanomedicine design and through creative manipulation of the tumour microenvironment.

Exploiting nanotechnology to overcome tumor drug resistance: Challenges and opportunities

Tumor cells develop resistance to chemotherapeutic drugs through multiple mechanisms. Overexpression of efflux transporters is an important source of drug resistance. Efflux transporters such as P-glycoprotein reduce intracellular drug accumulation and compromise drug efficacy. Various nanoparticle-based approaches have been investigated to overcome efflux-mediated resistance. These include the use of formulation excipients that inhibit transporter activity and co-delivery of the anticancer drug with a specific inhibitor of transporter function or expression. However, the effectiveness of nanoparticles can be diminished by poor transport in the tumor tissue. Hence, adjunct therapies that improve the intratumoral distribution of nanoparticles may be vital to the successful application of nanotechnology to overcome tumor drug resistance. This review discusses the mechanisms of tumor drug resistance and highlights the opportunities and challenges in the use of nanoparticles to improve the efficacy of anticancer drugs against resistant tumors.

Oncogenes and angiogenesis: a way to personalize anti-angiogenic therapy?

The acquisition of oncogenic mutations and promotion of angiogenesis are key hallmarks of cancer. These features are often thought of as separate events in tumor progression and the two fields of research have frequently been considered as independent. However, as we highlight in this review, activated oncogenes and deregulated angiogenesis are tightly associated, as mutations in cancer cells can lead to perturbation of the pro- and anti-angiogenic balance thereby causing aberrant angiogenesis. We propose that normalization of the vascular network by targeting oncogenes in the tumor cells might lead to more efficient and sustained therapeutic effects compared to therapies targeting tumor vessels. We discuss how pharmacological inhibition of oncogenes in tumor cells restores a functional vasculature by bystander anti-angiogenic effect. As genetic alterations are tumor-specific, targeted therapy, which potentially blocks the angiogenic program activated by individual oncogenes may lead to personalized anti-angiogenic therapy.

Pyruvate dehydrogenase kinase as a potential therapeutic target for malignant gliomas

Metabolic aberrations in the form of altered flux through key metabolic pathways are the major hallmarks of several life-threatening malignancies including malignant gliomas. These adaptations play an important role in the enhancement of the survival and proliferation of gliomas at the expense of the surrounding normal/healthy tissues. Recent studies in the field of neurooncology have directly targeted the altered metabolic pathways of malignant tumor cells for the development of anti-cancer drugs. Aerobic glycolysis due to elevated production of lactate from pyruvate regardless of oxygen availability is a common metabolic alteration in most malignancies. Aerobic glycolysis offers survival advantages in addition to generating substrates such as fatty acids, amino acids and nucleotides required for the rapid proliferation of cells. This review outlines the role of pyruvate dehydrogenase kinase (PDK) in gliomas as an inhibitor of pyruvate dehydrogenase that catalyzes the oxidative decarboxylation of pyruvate. An in-depth investigation on the key metabolic enzyme PDK may provide a novel therapeutic approach for the treatment of malignant gliomas.

Enhancing radiation therapy for patients with glioblastoma

Radiation therapy has been the foundation of therapy following maximal surgical resection in patients with newly diagnosed glioblastoma for decades and the primary therapy for unresected tumors. Using the standard approach with radiation and temozolomide, however, outcomes are poor, and glioblastoma remains an incurable disease with the majority of recurrences and progression within the radiation treatment field. As such, there is much interest in elucidating the mechanisms of resistance to radiation therapy and in developing novel approaches to overcoming this treatment resistance.

Combining two strategies to improve perfusion and drug delivery in solid tumors

Blood perfusion in tumors can be significantly lower than that in the surrounding normal tissue owing to the leakiness and/or compression of tumor blood vessels. Impaired perfusion reduces oxygen supply and results in a hypoxic microenvironment. Hypoxia promotes tumor progression and immunosuppression, and enhances the invasive and metastatic potential of cancer cells. Furthermore, poor perfusion lowers the delivery of systemically administered drugs. Therapeutic strategies to improve perfusion include reduction in vascular permeability by vascular normalization and vascular decompression by alleviating physical forces (solid stress) inside tumors. Both strategies have shown promise, but guidelines on how to use these strategies optimally are lacking. To this end, we developed a mathematical model to guide the optimal use of these strategies. The model accounts for vascular, transvascular, and interstitial fluid and drug transport as well as the diameter and permeability of tumor vessels. Model simulations reveal an optimal perfusion region when vessels are uncompressed, but not very leaky. Within this region, intratumoral distribution of drugs is optimized, particularly for drugs 10 nm in diameter or smaller and of low binding affinity. Therefore, treatments should modify vessel diameter and/or permeability such that perfusion is optimal. Vascular normalization is more effective for hyperpermeable but largely uncompressed vessels (e.g., glioblastomas), whereas solid stress alleviation is more beneficial for compressed but less-permeable vessels (e.g., pancreatic ductal adenocarcinomas). In the case of tumors with hyperpermeable and compressed vessels (e.g., subset of mammary carcinomas), the two strategies need to be combined for improved treatment outcomes.

Mechanism of action of conventional and targeted anticancer therapies: reinstating immunosurveillance

Conventional chemotherapeutics and targeted antineoplastic agents have been developed based on the simplistic notion that cancer constitutes a cell-autonomous genetic or epigenetic disease. However, it is becoming clear that many of the available anticancer drugs that have collectively saved millions of life-years mediate therapeutic effects by eliciting de novo or reactivating pre-existing tumor-specific immune responses. Here, we discuss the capacity of both conventional and targeted anticancer therapies to enhance the immunogenic properties of malignant cells and to stimulate immune effector cells, either directly or by subverting the immunosuppressive circuitries that preclude antitumor immune responses in cancer patients. Accumulating evidence indicates that the therapeutic efficacy of several antineoplastic agents relies on their capacity to influence the tumor-host interaction, tipping the balance toward the activation of an immune response specific for malignant cells. We surmise that the development of successful anticancer therapies will be improved and accelerated by the immunological characterization of candidate agents.

License for destruction: tumor-specific cytokine targeting

Stroma is an integral part of solid tumors and plays a key role in growth promotion and immune suppression. Most current therapies focus on destroying tumors and/or abnormal vasculature. However, evidence is emerging that anticancer efficacy improves with vessel normalization rather than destruction. Specific targeting of cytokines into tumors provides proof-of-concept that tumor stroma is dynamic and can be remodeled to increase drug access and alleviate immune suppression. Changing the inflammatory milieu 'opens' tumors for therapy and thus provides a license for destruction. This involves reprogramming of paracrine signaling networks between multiple stromal components to break the vicious cycle of angiogenesis and immune suppression. With active immunotherapy rapidly moving into the clinic, local cytokine delivery emerges as an attractive adjuvant.

Developmental and tumoral vascularization is regulated by G protein-coupled receptor kinase 2

Tumor vessel dysfunction is a pivotal event in cancer progression. Using an in vivo neovascularization model, we identified G protein-coupled receptor kinase 2 (GRK2) as a key angiogenesis regulator. An impaired angiogenic response involving immature vessels was observed in mice hemizygous for Grk2 or in animals with endothelium-specific Grk2 silencing. ECs isolated from these animals displayed intrinsic alterations in migration, TGF-β signaling, and formation of tubular networks. Remarkably, an altered pattern of vessel growth and maturation was detected in postnatal retinas from endothelium-specific Grk2 knockout animals. Mouse embryos with systemic or endothelium-selective Grk2 ablation had marked vascular malformations involving impaired recruitment of mural cells. Moreover, decreased endothelial Grk2 dosage accelerated tumor growth in mice, along with reduced pericyte vessel coverage and enhanced macrophage infiltration, and this transformed environment promoted decreased GRK2 in ECs and human breast cancer vessels. Our study suggests that GRK2 downregulation is a relevant event in the tumoral angiogenic switch.

DNA vaccination against membrane-bound Kit ligand: a new approach to inhibiting tumour growth and angiogenesis

A functional c-Kit/Kit ligand (KitL) signalling network is required for tumour angiogenesis and growth, and therefore the c-Kit/KitL system might well be a suitable target for the cancer immunotherapy approach. We herein describe a strategy that targets membrane-bound KitL (mbKitL) via DNA vaccination. The vaccination procedure generated antibodies which are able to detect mbKitL on human tumour endothelial cells (TECs) and on the breast cancer cell line: TSA. DNA vaccination, interferes with tumour vessel formation and transplanted tumour growth in vivo. Histological analysis demonstrates that, while tumour cell proliferation and vessel stabilisation are impaired, vessel permeability is increased in mice that produce mbKitL-targeting antibodies. We also demonstrate that vessel stabilisation and tumour growth require Akt activation in endothelial cells but not in pericytes. Moreover, we found that regulatory T cells (Treg) and tumour infiltrating inflammatory cells, involved in tumour growth and angiogenesis, were reduced in number in the tumour microenvironment of mice that generate anti-mbKitL antibodies. These data provide evidence that mbKitL targeted vaccination is an effective means of inhibiting tumour angiogenesis and growth.

Targeting tumor micro-environment for design and development of novel anti-angiogenic agents arresting tumor growth

Angiogenesis: a process of generation of new blood vessels has been proved to be necessary for sustained tumor growth and cancer progression. Inhibiting angiogenesis pathway has long been remained a significant hope for the development of novel, effective and target orientated antitumor agents arresting the tumor proliferation and metastasis. The process of neoangiogenesis as a biological process is regulated by several pro- and anti-angiogenic factors, especially vascular endothelial growth factor, fibroblast growth factor, epidermal growth factor, hypoxia inducible factor 1 and transforming growth factor. Every endothelial cell destined for vessel formation is equipped with receptors for these angiogenic peptides. Moreover, numerous other angiogenic cytokines such as platelet derived growth factor (PGDF), placenta growth factor (PGF), nerve growth factor (NGF), stem-cell factor (SCF), and interleukins-2, 4, 6 etc. These molecular players performs critical role in regulating the angiogenic switch. Couple of decade's research in molecular aspects of tumor biology has unraveled numerous structural and functional mysteries of these angiogenic peptides. In present article, a detailed update on the functional and structural peculiarities of the various angiogenic peptides is described focusing on structural opportunities made available that has potential to be used to modulate function of these angiogenic peptides in developing therapeutic agents targeting neoplastic angiogenesis. The data may be useful in the mainstream of developing novel anticancer agents targeting tumor angiogenesis. We also discuss major therapeutic agents that are currently used in angiogenesis associated therapies as well as those are subject of active research or are in clinical trials.

RNAi-mediated gene knockdown and anti-angiogenic therapy of RCCs using a cyclic RGD-modified liposomal-siRNA system

Angiogenesis is one of crucial processes associated with tumor growth and development, and consequently a prime target for cancer therapy. Although tumor endothelial cells (TECs) play a key role in pathological angiogenesis, investigating phenotypical changes in neovessels when a gene expression in TEC is suppressed is a difficult task. Small interfering RNA (siRNA) represents a potential agent due to its ability to silence a gene of interest. We previously developed a system for in vivo siRNA delivery to cancer cells that involves a liposomal-delivery system, a MEND that contains a unique pH-sensitive cationic lipid, YSK05 (YSK-MEND). In the present study, we report on the development of a system that permits the delivery of siRNA to TECs by combining the YSK-MEND and a ligand that is specific to TECs. Cyclo(Arg-Gly-Asp-D-Phe-Lys) (cRGD) is a well-known ligand to αVβ3 integrin, which is selectively expressed at high levels in TECs. We incorporated cRGD into the YSK-MEND (RGD-MEND) to achieve an efficient gene silencing in TECs. Quantitative RT-PCR and the 5' rapid amplification of cDNA ends PCR indicated that the intravenous injection of RGD-MEND at a dose of 4.0mg/kg induced a significant RNAi-mediated gene reduction in TEC but not in endothelial cells of other organs. Finally, we evaluated the therapeutic potency of the RGD-MEND encapsulating siRNA against vascular endothelial growth factor receptor 2. A substantial delay in tumor growth was observed after three sequential RGD-MEND injections on alternate days. In conclusion, the RGD-MEND represents a new approach for the characterization of TECs and for us in anti-angiogenic therapy.

Distinct roles of DKK1 and DKK2 in tumor angiogenesis

Tumor angiogenesis is essential for tumor invasive growth and metastasis, and generates abnormal vascular structures unlike developmental neovessel formation. To reduce tumor vascular abnormalities such as leakage and perivascular cell coverage deficiency that limit cancer therapy effectiveness, novel therapeutic approaches focus on vessel normalization. We have previously shown that Dickkopf-1 (DKK1), a Wnt antagonist, inhibits and its homolog DKK2 enhances, angiogenesis in normal tissues. In the present study, we investigated the effects of DKK1 and DKK2 on tumor growth and angiogenesis. Treatment of B16F10 melanoma-bearing mice with adenovirus expressing DKK1 significantly reduced tumor growth but DKK2 increased growth compared with controls. Similar pattern of tumor growth was observed in endothelial-specific DKK1 and DKK2 transgenic mice. Interestingly, tumor vascular density and perfusion were significantly decreased by DKK1 but increased by DKK2. Moreover, coverage of blood vessels by pericytes was reduced by DKK1, while DKK2 increased it. We further observed that DKK1 diminished retinal vessel density and increased avascular area in an in vivo murine model of oxygen-induced retinopathy, whereas DKK2 showed opposite results. These findings demonstrate that DKK1 and DKK2 have differential roles in normalization and functionality of tumor blood vessels, in addition to angiogenesis.

Tumor delivery of chemotherapy combined with inhibitors of angiogenesis and vascular targeting agents

Numerous angiogenesis-vascular targeting agents have been admitted to the ranks of cancer therapeutics; most are used in polytherapy regimens. This review looks at recent progress and our own preclinical experience in combining angiogenesis inhibitors, mainly acting on VEGF/VEGFR pathways, and vascular targeting agents with conventional chemotherapy, discussing the factors that determine the outcome of these treatments. Molecular and morphological modifications of the tumor microenvironment associated with drug distribution and activity are reviewed. Modalities to improve drug delivery and strategies for optimizing combination therapy are examined.

Suppression of interactions between prostate tumor cell-surface integrin and endothelial ICAM-1 by simvastatin inhibits micrometastasis

Cancer micrometastasis relies on the ability of cancer cells to secrete angiogenic modulators, to interact with the vascular endothelium, and to overcome the resistance offered by the endothelial-barrier. Being an essential step prior to metastasis, blockage of micrometastasis can have potential applications in cancer therapy and metastasis prevention. Due to poorly known molecular mechanisms leading to micrometastasis, developing therapeutic strategies to target prostate cancer utilizing drugs that block micrometastasis is far from reality. Here, we demonstrate the potential benefits of simvastatin in the inhibition of prostate cancer micrometastasis and reveal the novel molecular mechanisms underlying this process. First, we showed that simvastatin inhibited the ability of human PC3 prostate cancer cells for transendothelial migration in vitro. Second, our data indicated that simvastatin modulates the expression of tumor-derived factors such as angiopoietins and VEGF-A at the mRNA and protein levels by the PC3 cells, thus preventing endothelial-barrier disruption. Third, simvastatin directly activated endothelial cells and enhances endothelial-barrier resistance. Apart from this, our study revealed that simvastatin-mediated effect on PC3 micrometastasis was mediated through inhibition of integrin αv β3 activity and suppression of interaction between prostate cancer cell integrin αv β3 with endothelial ICAM-1.

Effects of pressure and electrical charge on macromolecular transport across bovine lens basement membrane

Molecular transport through the basement membrane is important for a number of physiological functions, and dysregulation of basement membrane architecture can have serious pathological consequences. The structure-function relationships that govern molecular transport in basement membranes are not fully understood. The basement membrane from the lens capsule of the eye is a collagen IV-rich matrix that can easily be extracted and manipulated in vitro. As such, it provides a convenient model for studying the functional relationships that govern molecular transport in basement membranes. Here we investigate the effects of increased transmembrane pressure and solute electrical charge on the transport properties of the lens basement membrane (LBM) from the bovine eye. Pressure-permeability relationships in LBM transport were governed primarily by changes in diffusive and convective contributions to solute flux and not by pressure-dependent changes in intrinsic membrane properties. The solute electrical charge had a minimal but statistically significant effect on solute transport through the LBM that was opposite of the expected electrokinetic behavior. The observed transport characteristics of the LBM are discussed in the context of established membrane transport modeling and previous work on the effects of pressure and electrical charge in other basement membrane systems.

Interrogating tumor metabolism and tumor microenvironments using molecular positron emission tomography imaging. Theranostic approaches to improve therapeutics

Positron emission tomography (PET) is a noninvasive molecular imaging technology that is becoming increasingly important for the measurement of physiologic, biochemical, and pharmacological functions at cellular and molecular levels in patients with cancer. Formation, development, and aggressiveness of tumor involve a number of molecular pathways, including intrinsic tumor cell mutations and extrinsic interaction between tumor cells and the microenvironment. Currently, evaluation of these processes is mainly through biopsy, which is invasive and limited to the site of biopsy. Ongoing research on specific target molecules of the tumor and its microenvironment for PET imaging is showing great potential. To date, the use of PET for diagnosing local recurrence and metastatic sites of various cancers and evaluation of treatment response is mainly based on [(18)F]fluorodeoxyglucose ([(18)F]FDG), which measures glucose metabolism. However, [(18)F]FDG is not a target-specific PET tracer and does not give enough insight into tumor biology and/or its vulnerability to potential treatments. Hence, there is an increasing need for the development of selective biologic radiotracers that will yield specific biochemical information and allow for noninvasive molecular imaging. The possibility of cancer-associated targets for imaging will provide the opportunity to use PET for diagnosis and therapy response monitoring (theranostics) and thus personalized medicine. This article will focus on the review of non-[(18)F]FDG PET tracers for specific tumor biology processes and their preclinical and clinical applications.

Cancer-generated lactic acid: a regulatory, immunosuppressive metabolite?

The common preference of cancers for lactic acid-generating metabolic energy pathways has led to proposals that their reprogrammed metabolism confers growth advantages such as decreased susceptibility to hypoxic stress. Recent observations, however, suggest that it generates a novel way for cancer survival. There is increasing evidence that cancers can escape immune destruction by suppressing the anti-cancer immune response through maintaining a relatively low pH in their micro-environment. Tumours achieve this by regulating lactic acid secretion via modification of glucose/glutamine metabolisms. We propose that the maintenance by cancers of a relatively low pH in their micro-environment, via regulation of their lactic acid secretion through selective modification of their energy metabolism, is another major mechanism by which cancers can suppress the anti-cancer immune response. Cancer-generated lactic acid could thus be viewed as a critical, immunosuppressive metabolite in the tumour micro-environment rather than a ‘waste product’. This paradigm shift can have major impact on therapeutic strategy development. Copyright © 2013 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Angiogenesis and lymphangiogenesis in the spectrum of leprosy and its reactional forms

Background

Angiogenesis and lymphangiogenesis are the processes of neovascularization that evolve from preexisting blood and lymphatic vessels. There are few studies on angiogenesis and none on lymphangiogenesis in leprosy. Thus, the role of neovascularization in the pathophysiological mechanisms of the disease was studied across the spectrum of leprosy, its reactional states and its residual lesions.

Methodology/Principal Findings

Seventy-six biopsies of leprosy skin lesions and seven healthy controls were selected. Fifty-five serum samples were used for the detection of CD105 by ELISA. Histological sections were stained with antibodies against CD31 (blood and lymphatic vessels), D2-40/podoplanin (lymphatic vessels), and CD105/endoglin (neovessels). Microvessels were counted in 100 high-power fields (400x) and the number of vessels was evaluated in relation to the extension of the inflammatory infiltrate (0-3), to the bacillary index (0-6) and to the clinical forms. Angiogenesis, as marked by CD31 and CD105, was observed across the leprosy spectrum, compared with the controls. Additionally, there was a positive correlation between these markers with extension of the infiltrate (p <0.0001). For D2/40, lymphangiogenesis was observed in the tuberculoid form (p <0.0001). There was no statistical significance for values of CD105 detected in plasma by ELISA.

Conclusions/Significance

Angiogenesis is present across the spectrum of leprosy and in its reactional forms. The increase in the number of vessels, as detected by CD31 and CD105 staining, is related to the extension of the inflammatory infiltrate. Samples from reactional lesions have a higher number of CD31+ and CD105+ stained vessels, which indicates their involvement in the pathophysiological mechanisms of the reactional states. The regression of lesions is accompanied by the regression of neovascularization. Drugs inhibiting angiogenesis may be relevant in the treatment of leprosy, in addition to multidrugtherapy, and in the prevention of the development of reactions.

β-Adrenergic system, a backstage manipulator regulating tumour progression and drug target in cancer therapy

β-Adrenoceptors are broadly distributed in various tissues of the body. Stress hormones regulate a panel of important physiological functions and disease states including cancer. Nicotine and its derivatives could stimulate the release of stress hormones from cancer cells, leading to the promotion of cancer development. β-Blockers have been widely used to control hypertension for decades. Recently, these agents could have significant implications in cancer therapy through blockade of adrenoceptors in tumour tissues. In this review, we summarize recent advancements about the influence of stress hormones, nicotine and β-adrenoceptors on cancer cell proliferation, apoptosis, invasion and metastasis, and also tumour vasculature normalization. Relevant signal pathways and potential value of β-blockers in the treatment of cancer are also discussed in this review.