Abnormalities in pericytes on blood vessels and endothelial sprouts in tumors

Pericytes in Metastasis

Pericytes have long been known to contribute indirectly to tumour growth by regulating angiogenesis. Thus, remodelling tumour blood vessels to maintain blood supply is critical for continued tumour growth. A role for pericytes in restricting leakage of tumour cells through blood vessels has also become evident given that adequate pericyte coverage of these blood vessels is critical for maintaining vascular permeability. Interestingly, the relocation of pericytes from blood vessels to the tumour microenvironment results in the emergence of different properties in these cells that actively promote tumour growth and metastasis-functions not associated with their well-studied role in vascular stability and permeability. These form the focus of this review.

Neural regeneration by regionally induced stem cells within post-stroke brains: Novel therapy perspectives for stroke patients

Ischemic stroke is a critical disease which causes serious neurological functional loss such as paresis. Hope for novel therapies is based on the increasing evidence of the presence of stem cell populations in the central nervous system (CNS) and the development of stem-cell-based therapies for stroke patients. Although mesenchymal stem cells (MSCs) represented initially a promising cell source, only a few transplanted MSCs were present near the injured areas of the CNS. Thus, regional stem cells that are present and/or induced in the CNS may be ideal when considering a treatment following ischemic stroke. In this context, we have recently showed that injury/ischemia-induced neural stem/progenitor cells (iNSPCs) and injury/ischemia-induced multipotent stem cells (iSCs) are present within post-stroke human brains and post-stroke mouse brains. This indicates that iNSPCs/iSCs could be developed for clinical applications treating patients with stroke. The present study introduces the traits of mouse and human iNSPCs, with a focus on the future perspective for CNS regenerative therapies using novel iNSPCs/iSCs.

Prognostic value of microvessel density in stage II and III colon cancer patients: a retrospective cohort study

Background

Microvessel density (MVD), as a derived marker for angiogenesis, has been associated with poor outcome in several types of cancer. This study aimed to evaluate the prognostic value of MVD in stage II and III colon cancer and its relation to tumour-stroma-percentage (TSP) and expression of HIF1A and VEGFA.

Methods

Formalin-fixed paraffin-embedded (FFPE) colon cancer tissues were collected from 53 stage II and 54 (5-fluorouracil-treated) stage III patients. MVD was scored by digital morphometric analysis of CD31-stained whole tumour sections. TSP was scored using haematoxylin-eosin stained slides. Protein expression of HIF1A and VEGFA was determined by immunohistochemical evaluation of tissue microarrays.

Results

Median MVD was higher in stage III compared to stage II colon cancers (11.1% versus 5.6% CD31-positive tissue area, p < 0.001). High MVD in stage II patients tended to be associated with poor disease free survival (DFS) in univariate analysis (p = 0.056). In contrast, high MVD in 5FU-treated stage III patients was associated with better DFS (p = 0.006). Prognostic value for MVD was observed in multivariate analyses for both cancer stages.

Conclusions

MVD is an independent prognostic factor associated with poor DFS in stage II colon cancer patients, and with better DFS in stage III colon cancer patients treated with adjuvant chemotherapy.

Electronic supplementary material

The online version of this article (10.1186/s12876-019-1063-4) contains supplementary material, which is available to authorized users.

The Basics of Sentinel Lymph Node Biopsy: Anatomical and Pathophysiological Considerations and Clinical Aspects

Sentinel lymph node (SLN) is the first node to receive the drainage directly from a tumor. Detection and pathological examination of the SLN is an important oncological procedure that minimizes morbidity related to extensive nodal dissection. SLN biopsy was first reported in 1960 but took approximately 40 years to come into general practice following reports of good outcomes in patients with melanoma. After many years of observation and research on its use in various malignancies SLN biopsy has become the standard surgical treatment in patients with malignant melanoma, breast, vulvar, and cervical cancers. Along with the introduction of new technologies, such as the fluorescent dyes indocyanine green (ICG) and near-infrared fluorescence (NIR), and pathologic ultrastaging, SLN detection rate has increased and false-negative rate has decreased. This literature review aimed to present an overview of the basic concepts and clinical aspects of SLN biopsy in the light of the current research.

Modelling the transport of fluid through heterogeneous, whole tumours in silico

Cancers exhibit spatially heterogeneous, unique vascular architectures across individual samples, cell-lines and patients. This inherently disorganised collection of leaky blood vessels contribute significantly to suboptimal treatment efficacy. Preclinical tools are urgently required which incorporate the inherent variability and heterogeneity of tumours to optimise and engineer anti-cancer therapies. In this study, we present a novel computational framework which incorporates whole, realistic tumours extracted ex vivo to efficiently simulate vascular blood flow and interstitial fluid transport in silico for validation against in vivo biomedical imaging. Our model couples Poiseuille and Darcy descriptions of vascular and interstitial flow, respectively, and incorporates spatially heterogeneous blood vessel lumen and interstitial permeabilities to generate accurate predictions of tumour fluid dynamics. Our platform enables highly-controlled experiments to be performed which provide insight into how tumour vascular heterogeneity contributes to tumour fluid transport. We detail the application of our framework to an orthotopic murine glioma (GL261) and a human colorectal carcinoma (LS147T), and perform sensitivity analysis to gain an understanding of the key biological mechanisms which determine tumour fluid transport. Finally we mimic vascular normalization by modifying parameters, such as vascular and interstitial permeabilities, and show that incorporating realistic vasculatures is key to modelling the contrasting fluid dynamic response between tumour samples. Contrary to literature, we show that reducing tumour interstitial fluid pressure is not essential to increase interstitial perfusion and that therapies should seek to develop an interstitial fluid pressure gradient. We also hypothesise that stabilising vessel diameters and permeabilities are not key responses following vascular normalization and that therapy may alter interstitial hydraulic conductivity. Consequently, we suggest that normalizing the interstitial microenvironment may provide a more effective means to increase interstitial perfusion within tumours.

The structure of tumours varies widely, with dense and chaotically-formed networks of blood vessels that differ between each individual tumour and even between different regions of the same tumour. This atypical environment can inhibit the delivery of anti-cancer therapies. Computational tools are urgently required which facilitate a deeper understanding of the relationship between blood vessel architectures and therapeutic response. We have developed a computational framework which integrates the complex tumour vascular architecture to predict fluid transport across all lengths scales in whole tumours. We apply our model to two tumour cell-lines and show that differences in their inherent vascular structures influence flow through cancerous tissue. We also use our platform to predict the fluid dynamic response following vascular normalization therapy in realistic, static tumour networks and show that the response is dependent on tumour vascular architecture. We hypothesise that therapy may alter the permeability of interstitial tissue to fluid transport and show that lowering interstitial fluid pressure is not a necessary therapeutic outcome to increase tumour perfusion.

Uveal Melanoma, Angiogenesis and Immunotherapy, Is There Any Hope?

Uveal melanoma is considered a rare disease but it is the most common intraocular malignancy in adults. Local treatments are effective, but the systemic recurrence rate is unacceptably high. Moreover, once metastasis have developed the prognosis is poor, with a 5-year survival rate of less than 5%, and systemic therapies, including immunotherapy, have rendered poor results. The tumour biology is complex, but angiogenesis is a highly important pathway in these tumours. Vasculogenic mimicry, the ability of melanomas to generate vascular channels independently of endothelial cells, could play an important role, but no effective therapy targeting this process has been developed so far. Angiogenesis modulates the tumour microenvironment of melanomas, and a close interplay is established between them. Therefore, combining immune strategies with drugs targeting angiogenesis offers a new therapeutic paradigm. In preclinical studies, these approaches effectively target these tumours, and a phase I clinical study has shown encouraging results in cutaneous melanomas. In this review, we will discuss the importance of angiogenesis in uveal melanoma, with a special focus on vasculogenic mimicry, and describe the interplay between angiogenesis and the tumour microenvironment. In addition, we will suggest future therapeutic approaches based on these observations and mention ways in which to potentially enhance current treatments.

Pericyte Plasticity in the Brain

Cerebral pericytes are perivascular cells that stabilize blood vessels. Little is known about the plasticity of pericytes in the adult brain in vivo. Recently, using state-of-the-art technologies, including two-photon microscopy in combination with sophisticated Cre/loxP in vivo tracing techniques, a novel role of pericytes was revealed in vascular remodeling in the adult brain. Strikingly, after pericyte ablation, neighboring pericytes expand their processes and prevent vascular dilatation. This new knowledge provides insights into pericyte plasticity in the adult brain.

ACE2 inhibits breast cancer angiogenesis via suppressing the VEGFa/VEGFR2/ERK pathway

BACKGROUND

Breast cancer angiogenesis is key for metastasis and predicts a poor prognosis. Angiotensin-converting enzyme 2 (ACE2), as a member of the renin-angiotensin system (RAS), was reported to restrain the progression of hepatocellular carcinoma (HCC) and non-small cell lung cancer (NSCLC) through inhibiting angiogenesis. However, the relationship between ACE2 and breast cancer angiogenesis remains unclear.

METHODS

The prognosis and relative gene selection were analysed using the GEPIA, GEO, TCGA and STRING databases. ACE2 expression in breast cancer tissue was estimated by reverse transcription-quantitative polymerase chain reaction (qPCR). Breast cancer cell migration, proliferation and angiogenesis were assessed by Transwell migration, proliferation, tube formation, and wound healing assays. The expression of vascular endothelial growth factor A (VEGFa) was detected by qPCR and Western blotting. The phosphorylation of vascular endothelial growth factor receptor 2 (VEGFR2), mitogen-activated protein kinase 1/2 (MEK1/2), and extracellular signal-regulated protein kinase 1/2 (ERK1/2) was examined by Western blotting. Breast cancer metastasis and angiogenesis in vivo were measured using a zebrafish model.

RESULTS

ACE2 was downregulated in breast cancer patients. Patients with higher ACE2 expression had longer relapse-free survival (RFS). In vitro, ACE2 inhibited breast cancer migration. Meanwhile, ACE2 in breast cancer cells inhibited human umbilical vascular endothelial cell (HUVEC) proliferation, tube formation and migration. In the zebrafish model, ACE2 inhibited breast cancer cell metastasis, as demonstrated by analyses of the number of disseminated foci and the metastatic distance. Neo-angiogenesis was also decreased by ACE2. ACE2 downregulated the expression of VEGFa in breast cancer cells. Furthermore, ACE2 in breast cancer cells inactivated the phosphorylation of VEGFR2, MEK1/2, and ERK1/2 in HUVECs.

CONCLUSIONS

Our findings suggest that ACE2, as a potential resister to breast cancer, might inhibit breast cancer angiogenesis through the VEGFa/VEGFR2/ERK pathway.

TRIAL REGISTRATION

Retrospectively registered.

Pericytes Act as Key Players in Spinal Cord Injury

Spinal cord injury results in locomotor impairment attributable to the formation of an inhibitory fibrous scar, which prevents axonal regeneration after trauma. The scarcity of knowledge about the molecular and cellular mechanisms involved in scar formation after spinal cord lesion impede the design of effective therapies. Recent studies, by using state-of-the-art technologies, including genetic tracking and blockage of pericytes in combination with optogenetics, reveal that pericyte blockage facilitates axonal regeneration and neuronal integration into the local neural circuitry. Strikingly, a pericyte subset is essential during scarring after spinal cord injury, and its arrest results in motor performance improvement. The arising knowledge from current research will contribute to novel approaches to develop therapies for spinal cord injury. We review novel advances in our understanding of pericyte biology in the spinal cord.

Isocitrate dehydrogenase1 mutation reduces the pericyte coverage of microvessels in astrocytic tumours

INTRODUCTION

Tumour-associated angiogenesis is associated with the malignancy and poor prognosis of glioma. Isocitrate dehydrogenase (IDH) mutations are present in the majority of lower-grade (WHO grade II and III) and secondary glioblastomas, but their roles in tumour angiogenesis remain unclear.

METHODS

Using magnetic resonance imaging (MRI), the cerebral blood flow (CBF) of IDH-mutated glioma was measured and compared with the IDH-wildtype glioma. The densities of microvessels in IDH-mutated and wildtype astrocytoma and glioblastoma were assessed by immunohistochemical (IHC) staining with CD34, and the pericytes were labelled with α-smooth muscle antigen (α-SMA), neural-glial antigen 2 (NG2) and PDGF receptor-β (PDGFR-β), respectively. Furthermore, glia-specific mutant IDH1 knock-in mice were generated to evaluate the roles of mutant IDH1 on brain vascular architectures. The transcriptions of the angiogenesis-related genes were assessed in TCGA datasets, including ANGPT1, PDGFB and VEGFA. The expressions of these genes were further determined by western blot in U87-MG cells expressing a mutant IDH1 or treated with 2-HG.

RESULTS

The MRI results indicated that CBF was reduced in the IDH-mutated gliomas. The IHC staining showed that the pericyte coverages of microvessels were significantly decreased, but the microvessel densities (MVDs) were only slightly decreased in IDH-mutated glioma. The mutant IDH1 knock-in also impeded the pericyte coverage of brain microvessels in mice. Moreover, the TCGA database showed the mRNA levels of angiogenesis factors, including ANGPT1, PDGFB and VEGFA, were downregulated, and their promoters were also highly hyper-methylated in IDH-mutated gliomas. In addition, both mutant IDH1 and D-2-HG could downregulate the expression of these genes in U87-MG cells.

CONCLUSIONS

Our results suggested that IDH mutations could reduce the pericyte coverage of microvessels in astrocytic tumours by inhibiting the expression of angiogenesis factors. As vascular pericytes play an essential role in maintaining functional blood vessels to support tumour growth, our findings imply a potential avenue of therapeutic strategy for IDH-mutated gliomas.

Angiogenesis and vascular stability in eicosanoids and cancer

Angiogenesis and inflammation are hallmarks of cancer. Arachidonic acid and other polyunsaturated fatty acids (PUFAs) are primarily metabolized by three distinct enzymatic systems initiated by cyclooxygenases, lipoxygenases, and cytochrome P450 enzymes (CYP) to generate bioactive eicosanoids, including prostanoids, leukotrienes, hydroxyeicosatetraenoic acids, and epoxyeicosatrienoic acids. As some of the PUFA metabolites playing essential roles in inflammatory processes, these pathways have been widely studied as therapeutic targets of inflammation. Because of their anti-inflammatory effects, these pathways were also proposed as anti-cancer targets. However, although the eicosanoids were linked to endothelial cell proliferation and angiogenesis almost two decades ago, it is only recently PUFA metabolites, especially those generated by CYP enzymes and the soluble epoxide hydrolase (sEH), have been recognized as important signaling mediators in physiological and pathological angiogenesis. Despite the fact that tumor growth and invasion are heavily dependent on inner-tumor angiogenesis and influenced by vascular stability, the role played by PUFA metabolites in tumor angiogenesis and vessel integrity has been largely overlooked. This review highlights current knowledge on the function of PUFA metabolites generated by the CYP/sEH pathway in angiogenesis and vascular stability as well as their potential involvement in cancer development.

Fluorescence Guidance in Surgical Oncology: Challenges, Opportunities, and Translation

Surgical resection continues to function as the primary treatment option for most solid tumors. However, the detection of cancerous tissue remains predominantly subjective and reliant on the expertise of the surgeon. Surgery that is guided by fluorescence imaging has shown clinical relevance as a new approach to detecting the primary tumor, tumor margins, and metastatic lymph nodes. It is a technique to reduce recurrence and increase the possibility of a curative resection. While significant progress has been made in developing this emerging technology as a tool to assist the surgeon, further improvements are still necessary. Refining imaging agents and tumor targeting strategies to be a precise and reliable surgical strategy is essential in order to translate this technology into patient care settings. This review seeks to provide a comprehensive update on the most recent progress of fluorescence-guided surgery and its translation into the clinic. By highlighting the current status and recent developments of fluorescence image-guided surgery in the field of surgical oncology, we aim to offer insight into the challenges and opportunities that require further investigation.

Challenges and Opportunities from Basic Cancer Biology for Nanomedicine for Targeted Drug Delivery

Background:

Effective cancer therapy is still a great challenge for modern medical research due to the complex underlying mechanisms of tumorigenesis and tumor metastasis, and the limitations commonly associated with currently used cancer therapeutic options. Nanotechnology has been implemented in cancer therapeutics with immense potential for improving cancer treatment.

Objective:

Through information about the recent advances regarding cancer hallmarks, we could comprehensively understand the pharmacological effects and explore the mechanisms of the interaction between the nanomaterials, which could provide opportunities to develop mechanism-based nanomedicine to treat human cancers.

Methods:

We collected related information and data from articles.

Results:

In this review, we discussed the characteristics of cancer including tumor angiogenesis, abnormalities in tumor blood vessels, uncontrolled cell proliferation markers, multidrug resistance, tumor metastasis, cancer cell metabolism, and tumor immune system that provide opportunities and challenges for nanomedicine to be directed to specific cancer cells and portray the progress that has been accomplished in application of nanotechnology for cancer treatment.

Conclusion:

The information presented in this review can provide useful references for further studies on developing effective nanomedicine for the treatment of cancer.

Biological Principles of Stereotactic Body Radiation Therapy (SBRT) and Stereotactic Radiation Surgery (SRS): Indirect Cell Death

PURPOSE

To review the radiobiological mechanisms of stereotactic body radiation therapy stereotactic body radiation therapy (SBRT) and stereotactic radiation surgery (SRS).

METHODS AND MATERIALS

We reviewed previous reports and recent observations on the effects of high-dose irradiation on tumor cell survival, tumor vasculature, and antitumor immunity. We then assessed the potential implications of these biological changes associated with SBRT and SRS.

RESULTS

Irradiation with doses higher than approximately 10 Gy/fraction causes significant vascular injury in tumors, leading to secondary tumor cell death. Irradiation of tumors with high doses has also been reported to increase the antitumor immunity, and various approaches are being investigated to further elevate antitumor immunity. The mechanism of normal tissue damage by high-dose irradiation needs to be further investigated.

CONCLUSIONS

In addition to directly killing tumor cells, high-dose irradiation used in SBRT and SRS induces indirect tumor cell death via vascular damage and antitumor immunity. Further studies are warranted to better understand the biological mechanisms underlying the high efficacy of clinical SBRT and SRS and to further improve the efficacy of SBRT and SRS.

LINGO-1 shRNA Loaded by Pluronic F-127 Promotes Functional Recovery After Ventral Root Avulsion

Spinal root avulsion typically leads to massive motoneuron death and severe functional deficits of the target muscles. Multiple pathological factors such as severe neuron loss, induction of inhibitory molecules, and insufficient regeneration are responsible for the poor functional recovery. Leucine-rich repeat and immunoglobulin-like domain-containing Nogo receptor-interacting protein 1 (LINGO-1), a central nervous system (CNS)-specific transmembrane protein that is selectively expressed on neurons and oligodendrocytes, serves as a potent negative mediator of axonal regeneration and myelination in CNS injuries and diseases. Although accumulating evidence has demonstrated improvement in axonal regeneration and neurological functions by LINGO-1 antagonism in CNS damage, the possible effects of LINGO-1 in spinal root avulsion remain undiscovered. In this study, a LINGO-1 knockdown strategy using lentiviral vectors encoding LINGO-1 short hairpin interfering RNA (shRNA) delivered by the Pluronic F-127 (PF-127) hydrogel was described after brachial plexus avulsion (BPA). We provide evidence that following BPA and immediate reimplantation, transplantation of LINGO-1 shRNA lentiviral vectors encapsulated by PF-127 rescued the injured motoneurons, enhanced axonal outgrowth and myelination, rebuilt motor endplates, facilitated the reinnervation of terminal muscles, improved angiogenesis, and promoted recovery of avulsed forelimbs. Altogether, these data suggest that delivery of LINGO-1 shRNA by a gel scaffold is a potential therapeutic approach for root avulsion. Impact Statement In this study, we attempted transplantation of lentivirus (LV)/leucine-rich repeat and immunoglobulin-like domain-containing Nogo receptor-interacting protein 1 (LINGO-1)-short hairpin interfering RNA (shRNA) encapsulated by the Pluronic F-127 (PF-127) hydrogel into a brachial plexus avulsion (BPA)-reimplantation model. We found that administration of LV/LINGO-1 shRNA facilitates neuron survival and axonal regeneration, attenuates muscle atrophy and motor endplate (MEP) loss, enhances neovascularization, and promotes functional recovery in BPA rats. Co-transplantation of LV/LINGO-1 shRNA and gel reinforces the survival-promoting effect, axonal outgrowth, and angiogenesis in comparison with LV/LINGO-1 shRNA application alone. Our research provides evidence that LV /LINGO-1 shRNA delivered by PF-127 represents a new treatment strategy for BPA repair.

Phase-specific functions of macrophages determine injury-mediated corneal hem- and lymphangiogenesis

Macrophages are critical mediators of injury-associated corneal hemangiogenesis (HA) and lymphangiogenesis (LA). Yet, molecular regulators of the hem- and lymphangiogenic potential of corneal wound macrophages are poorly understood. Using two different mouse models of acute (perforating corneal incision injury) and chronic (corneal suture placement model) corneal injury, here we identified distinct functions of early- versus late-phase corneal wound macrophages in corneal HA and LA. Whereas early-phase wound macrophages are essential for initiation and progression of injury-mediated corneal HA and LA, late-phase wound macrophages control maintenance of established corneal lymphatic vessels, but not blood vessels. Furthermore, our findings reveal that the hem- and lymphangiogenic potential of corneal wound macrophages is controlled by the type of the corneal damage. Whereas perforating corneal incision injury induced primarily wound macrophages with lymphangiogenic potential, corneal suture placement provoked wound macrophages with both hem- and lymphangiogenic potential. Our findings highlight a previously unrecognized injury-context dependent role of early- versus late-phase corneal wound macrophages with potential clinical impact on therapy development for sight-threatening corneal neovascular diseases.

Pericytes in Sarcomas and Other Mesenchymal Tumors

Tumors of mesenchymal origin are a diverse group, with >130 distinct entities currently recognized by the World Health Organization. A subset of mesenchymal tumors grow or invade in a perivascular fashion, and their potential relationship to pericytes is a matter of ongoing interest. In fact, multiple intersections exist between pericytes and tumors of mesenchymal origin. First, pericytes are the likely cell of origin for a group of mesenchymal tumors with a common perivascular growth pattern. These primarily benign tumors grow in a perivascular fashion and diffusely express canonical pericyte markers such as CD146, smooth muscle actin (SMA), platelet-derived growth factor receptor beta (PDGFR-β), and RGS5. These benign tumors include glomus tumor, myopericytoma, angioleiomyoma, and myofibroma. Second and as suggested by animal models, pericytes may give rise to malignant sarcomas. This is not a suggestion that all sarcomas within a certain subtype arise from pericytes, but that genetic modifications within a pericyte cell type may give rise to sarcomas. Third, mesenchymal tumors that are likely not a pericyte derivative co-opt pericyte markers in certain contexts. These include the PEComa family of tumors and liposarcoma. Fourth and finally, as "guardians" that enwrap the microvasculature, nonneoplastic pericytes may be important in sarcoma disease progression.

Pericytes in Breast Cancer

Breast cancer is a heterogeneous disease driven not only by evolutionally diverse cancer cell themselves but also by highly dynamic microenvironment. At the center of the tumor microenvironment, tumor vasculature plays multiple roles from supporting tumor growth to providing a route for metastasis to the distant organ sites. Blood vessels in breast cancer present with perfusion defects associated with vessel dilation, tortuosity, and poor perivascular coverage (Li et al., Ultrasound Med 32:1145-1155, 2013; Eberhard et al., Cancer Res 60:1388-1393, 2000; Cooke et al., Cancer Cell 21:66-81, 2012). Such abnormal vascular system is partly due to the morphological and molecular alteration of pericytes that is accompanied by a significant heterogeneity within the populations (Kim et al., JCI Insight 1:e90733, 2016). While pericytes are implicated for their controversial roles in breast cancer metastasis (Cooke et al., Cancer Cell 21:66-81, 2012; Gerhardt and Semb, J Mol Med (Berl) 86:135-144, 2008; Keskin et al., Cell Rep 10:1066-1081, 2015; Meng et al., Future Oncol 11:169-179, 2015; Xian et al., J Clin Invest 116:642-651, 2006), the impact of their heterogeneity on breast cancer progression, metastasis, intratumoral immunity, and response to chemotherapy are largely unknown. Due to the complexity of angiogenic programs of breast cancer, the anti-angiogenic or anti-vascular treatment has been mostly unsuccessful (Tolaney et al., Proc Natl Acad Sci U S A 112:14325-14330, 2015; Mackey et al., Cancer Treat Rev 38:673-688, 2012; Sledge, J Clin Oncol 33:133-135, 2015) and requires much in-depth knowledge on different components of tumor microenvironment and how these stromal cells are interacting and communicating to each other. Therefore, understanding pericyte heterogeneity and their differential functional contribution will shed light on new potential approaches to treat breast cancer.

Working with Hypoxia

A hypoxic environment can be defined as a region of the body or the whole body that is deprived of oxygen. Hypoxia is a feature of many diseases, such as cardiovascular disease, tissue trauma, stroke, and solid cancers. A loss of oxygen supply usually results in cell death; however, when cells gradually become hypoxic, they may survive and continue to thrive as described for conditions that promote metastatic growth. The role of hypoxia in these pathogenic pathways is therefore of great interest, and understanding the effect of hypoxia in regulating these mechanisms is fundamentally important. This chapter gives an extensive overview of these mechanisms. Moreover, given the challenges posed by tumor hypoxia we describe the current methods to simulate and detect hypoxic conditions followed by a discussion on current and experimental therapies that target hypoxic cells.

Pathological Process of Prompt Connection between Host and Donor Tissue Vasculature Causing Rapid Perfusion of the Engineered Donor Tissue after Transplantation

The shortage of donors for transplantation therapy is a serious issue worldwide. Tissue engineering is considered a potential solution to this problem. Connection and perfusion in engineered tissues after transplantation is vital for the survival of the transplanted tissue, especially for tissues requiring blood perfusion to receive nutrients, such as the heart. A myocardial cell sheet containing an endothelial cell network structure was fabricated in vitro using cell sheet technology. Transplantation of the three-dimensional (3D) tissue by layering myocardial sheets could ameliorate ischemic heart disease in a rat model. The endothelial cell network in the 3D tissue was able to rapidly connect to host vasculature and begin perfusion within 24 h after transplantation. In this review, we compare and discuss the engineered tissue⁻host vasculature connection process between tissue engineered constructs with hydrogels and cell sheets by histological analysis. This review provides information that may be useful for further improvements of in vivo engineered tissue vascularization techniques.

PHD3 Acts as Tumor Suppressor in Mouse Osteosarcoma and Influences Tumor Vascularization via PDGF-C Signaling

Cancer cell proliferation and insufficient blood supply can lead to the development of hypoxic areas in the tumor tissue. The adaptation to the hypoxic environment is mediated by a transcriptional complex called hypoxia-inducible factor (HIF). HIF protein levels are tightly controlled by oxygen-dependent prolyl hydroxylase domain proteins (PHDs). However, the precise roles of these enzymes in tumor progression and their downstream signaling pathways are not fully characterized. Here, we study PHD3 function in murine experimental osteosarcoma. Unexpectedly, PHD3 silencing in LM8 cells affects neither HIF-1α protein levels, nor the expression of various HIF-1 target genes. Subcutaneous injection of PHD3-silenced tumor cells accelerated tumor progression and was accompanied by dramatic phenotypic changes in the tumor vasculature. Blood vessels in advanced PHD3-silenced tumors were enlarged whereas their density was greatly reduced. Examination of the molecular pathways underlying these alterations revealed that platelet-derived growth factor (PDGF)-C signaling is activated in the vasculature of PHD3-deficient tumors. Silencing of PDGF-C depleted tumor growth, increased vessel density and reduced vessel size. Our data show that PHD3 controls tumor growth and vessel architecture in LM8 osteosarcoma by regulating the PDGF-C pathway, and support the hypothesis that different members of the PHD family exert unique functions in tumors.

Tumour-vasculature development via endothelial-to-mesenchymal transition after radiotherapy controls CD44v6+ cancer cell and macrophage polarization

It remains controversial whether targeting tumour vasculature can improve radiotherapeutic efficacy. We report that radiation-induced endothelial-to-mesenchymal transition (EndMT) leads to tumour vasculature with abnormal SMA⁺NG2⁺ pericyte recruitment during tumour regrowth after radiotherapy. Trp53 (but not Tgfbr2) deletion in endothelial cells (ECs) inhibited radiation-induced EndMT, reducing tumour regrowth and metastases with a high CD44v6⁺ cancer-stem-cell (CSC) content after radiotherapy. Osteopontin, an EndMT-related angiocrine factor suppressed by EC-Trp53 deletion, stimulated proliferation in dormant CD44v6⁺ cells in severely hypoxic regions after radiation. Radiation-induced EndMT significantly regulated tumour-associated macrophage (TAM) polarization. CXCR4 upregulation in radioresistant tumour ECs was highly associated with SDF-1⁺ TAM recruitment and M2 polarization of TAMs, which was suppressed by Trp53 deletion. These EndMT-related phenomena were also observed in irradiated human lung cancer tissues. Our findings suggest that targeting tumour EndMT might enhance radiotherapy efficacy by inhibiting the re-activation of dormant hypoxic CSCs and promoting anti-tumour immune responses.

Radiotherapy is the main treatment for most cancer, but it is unclear if targeting tumour vasculature can enhance tumour radiosensitivity. Here, the authors show that tumour endothelial-mesenchymal transition after radiotherapy leads to proliferation of radioresistant CSCs and tumour associated macrophages polarization.

Nitric oxide-releasing nanoparticles improve doxorubicin anticancer activity

Purpose

Anticancer drug delivery systems are often limited by hurdles, such as off-target distribution, slow cellular internalization, limited lysosomal escape, and drug resistance. To overcome these limitations, we have developed a stable nitric oxide (NO)-releasing nanoparticle (polystyrene-maleic acid [SMA]-tert-dodecane S-nitrosothiol [tDodSNO]) with the aim of enhancing the anticancer properties of doxorubicin (Dox) and a Dox-loaded nanoparticle (SMA-Dox) carrier.

Materials and methods

Effects of SMA-tDodSNO and/or in combination with Dox or SMA-Dox on cell viability, apoptosis, mitochondrial membrane potential, lysosomal membrane permeability, tumor tissue, and tumor growth were studied using in vitro and in vivo model of triple-negative breast cancer (TNBC). In addition, the concentrations of SMA-Dox and Dox in combination with SMA-tDodSNO were measured in cells and tumor tissues.

Results

Combination of SMA-tDodSNO and Dox synergistically decreased cell viability and induced apoptosis in 4T1 (TNBC cells). Incubation of 4T1 cells with SMA-tDodSNO (40 µM) significantly enhanced the cellular uptake of SMA-Dox and increased Dox concentration in the cells resulting in a twofold increase (P<0.001). Lysosomal membrane integrity, evaluated by acridine orange (AO) staining, was impaired by 40 µM SMA-tDodSNO (P<0.05 vs control) and when combined with SMA-Dox, this effect was significantly potentiated (P<0.001 vs SMA-Dox). Subcutaneous administration of SMA-tDodSNO (1 mg/kg) to xenografted mice bearing 4T1 cells showed that SMA-tDodSNO alone caused a twofold decrease in the tumor size compared to the control group. SMA-tDodSNO in combination with SMA-Dox resulted in a statistically significant 4.7-fold reduction in the tumor volume (P<0.001 vs control), without causing significant toxicity as monitored through body weight loss.

Conclusion

Taken together, these results suggest that SMA-tDodSNO can be used as a successful strategy to increase the efficacy of Dox and SMA-Dox in a model of TNBC.

Sensitivity of Multiphase Pseudocontinuous Arterial Spin Labelling (MP pCASL) Magnetic Resonance Imaging for Measuring Brain and Tumour Blood Flow in Mice

Brain and tumour blood flow can be measured noninvasively using arterial spin labelling (ASL) magnetic resonance imaging (MRI), but reliable quantification in mouse models remains difficult. Pseudocontinuous ASL (pCASL) is recommended as the clinical standard for ASL and can be improved using multiphase labelling (MP pCASL). The aim of this study was to optimise and validate MP pCASL MRI for cerebral blood flow (CBF) measurement in mice and to assess its sensitivity to tumour perfusion. Following optimization of the MP pCASL sequence, CBF data were compared with gold-standard autoradiography, showing close agreement. Subsequently, MP pCASL data were acquired at weekly intervals in models of primary and secondary brain tumours, and tumour microvessel density was determined histologically. MP pCASL measurements in a secondary brain tumour model revealed a significant reduction in blood flow at day 35 after induction, despite a higher density of blood vessels. Tumour core regions also showed reduced blood flow compared with the tumour rim. Similarly, significant reductions in CBF were found in a model of glioma 28 days after tumour induction, together with an increased density of blood vessels. These findings indicate that MP pCASL MRI provides accurate and robust measurements of cerebral blood flow in naïve mice and is sensitive to changes in tumour perfusion.

Targeting glioblastoma-derived pericytes improves chemotherapeutic outcome

Glioblastoma is the most common malignant brain cancer in adults, with poor prognosis. The blood-brain barrier limits the arrival of several promising anti-glioblastoma drugs, and restricts the design of efficient therapies. Recently, by using state-of-the-art technologies, including thymidine kinase targeting system in combination with glioblastoma xenograft mouse models, it was revealed that targeting glioblastoma-derived pericytes improves chemotherapy efficiency. Strikingly, ibrutinib treatment enhances chemotherapeutic effectiveness, by targeting pericytes, improving blood-brain barrier permeability, and prolonging survival. This study identifies glioblastoma-derived pericyte as a novel target in the brain tumor microenvironment during carcinogenesis. Here, we summarize and evaluate recent advances in the understanding of pericyte's role in the glioblastoma microenvironment.

Tumor Microenvironment Targeted Nanotherapy

Recent developments in nanotechnology have brought new approaches to cancer diagnosis and therapy. While enhanced permeability and retention effect promotes nano-chemotherapeutics extravasation, the abnormal tumor vasculature, high interstitial pressure and dense stroma structure limit homogeneous intratumoral distribution of nano-chemotherapeutics and compromise their imaging and therapeutic effect. Moreover, heterogeneous distribution of nano-chemotherapeutics in non-tumor-stroma cells damages the non-tumor cells, and interferes with tumor-stroma crosstalk. This can lead not only to inhibition of tumor progression, but can also paradoxically induce acquired resistance and facilitate tumor cell proliferation and metastasis. Overall, the tumor microenvironment plays a vital role in regulating nano-chemotherapeutics distribution and their biological effects. In this review, the barriers in tumor microenvironment, its consequential effects on nano-chemotherapeutics, considerations to improve nano-chemotherapeutics delivery and combinatory strategies to overcome acquired resistance induced by tumor microenvironment have been summarized. The various strategies viz., nanotechnology based approach as well as ligand-mediated, redox-responsive, and enzyme-mediated based combinatorial nanoapproaches have been discussed in this review.

Computational fluid dynamics with imaging of cleared tissue and of in vivo perfusion predicts drug uptake and treatment responses in tumours

Understanding the uptake of a drug by diseased tissue, and the drug's subsequent spatiotemporal distribution, are central factors in the development of effective targeted therapies. However, the interaction between the pathophysiology of diseased tissue and individual therapeutic agents can be complex, and can vary across tissue types and across subjects. Here, we show that the combination of mathematical modelling, high-resolution optical imaging of intact and optically cleared tumour tissue from animal models, and in vivo imaging of vascular perfusion predicts the heterogeneous uptake, by large tissue samples, of specific therapeutic agents, as well as their spatiotemporal distribution. In particular, by using murine models of colorectal cancer and glioma, we report and validate predictions of steady-state blood flow and intravascular and interstitial fluid pressure in tumours, of the spatially heterogeneous uptake of chelated gadolinium by tumours, and of the effect of a vascular disrupting agent on tumour vasculature.

Combining Vascular Normalization with an Oncolytic Virus Enhances Immunotherapy in a Preclinical Model of Advanced-Stage Ovarian Cancer

PURPOSE

Intravenous delivery of oncolytic viruses often leads to tumor vascular shutdown, resulting in decreased tumor perfusion and elevated tumor hypoxia. We hypothesized that using 3TSR to normalize tumor vasculature prior to administration of an oncolytic Newcastle disease virus (NDV) would enhance virus delivery and trafficking of immunologic cell subsets to the tumor core, resulting in systemically enhanced immunotherapy and regression of advanced-stage epithelial ovarian cancer (EOC).

EXPERIMENTAL DESIGN

Using an orthotopic, syngeneic mouse model of advanced-stage EOC, we pretreated mice with 3TSR (4 mg/kg per day) alone or followed by combination with fusogenic NDV(F3aa) (1.0 × 10⁸ plaque-forming units).

RESULTS

Treatment with 3TSR normalized tumor vasculature, enhanced blood perfusion of primary EOC tumors, and induced disease regression. Animals treated with combination therapy had the greatest reduction in primary tumor mass, ascites accumulation, and secondary lesions (50% of mice were completely devoid of peritoneal metastases). Combining 3TSR + NDV(F3aa) led to enhanced trafficking of immunologic cells into the primary tumor core.

CONCLUSIONS

We have shown, for the first time, that NDV, like other oncolytic viruses, is a potent mediator of acute vascular shutdown and that preventing this through vascular normalization can promote regression in a preclinical model of advanced-stage ovarian cancer. This challenges the current focus on induction of intravascular thrombosis as a requisite for successful oncolytic virotherapy.See related commentary by Bykov and Zamarin, p. 1446.

Fibronectin Produced by Cerebral Endothelial and Vascular Smooth Muscle Cells Contributes to Perivascular Extracellular Matrix in Late-Delayed Radiation-Induced Brain Injury

Late-delayed radiation-induced brain injury (RIBI) is a major adverse effect of fractionated whole-brain irradiation (fWBI). Characterized by progressive cognitive dysfunction, and associated cerebrovascular and white matter injury, RIBI deleteriously affects quality of life for cancer patients. Despite extensive morphological characterization of the injury, the pathogenesis is unclear, thus limiting the development of effective therapeutics. We previously reported that RIBI is associated with increased gene expression of the extracellular matrix (ECM) protein fibronectin (FN1). We hypothesized that fibronectin contributes to perivascular ECM, which may impair diffusion to the dependent parenchyma, thus contributing to the observed cognitive decline. The goal of this study was to determine the localization of fibronectin in RIBI and further characterize the composition of perivascular ECM, as well as identify the cell of origin for FN1 by in situ hybridization. Briefly, fibronectin localized to the vascular basement membrane of morphologically normal blood vessels from control comparators and animals receiving fWBI, and to the perivascular space of edematous and fibrotic vascular phenotypes of animals receiving fWBI. Additional mild diffuse parenchymal staining in areas of vascular injury suggested blood-brain-barrier disruption and plasma fibronectin extravasation. Perivascular ECM lacked amyloid and contained lesser amounts of collagens I and IV, which localized to the basement membrane. These changes occurred in the absence of alterations in microvascular area fraction or microvessel density. Fibronectin transcripts were rarely expressed in control comparators, and were most strongly induced within cerebrovascular endothelial and vascular smooth muscle cells after fWBI. Our results demonstrate that fibronectin is produced by cerebrovascular endothelial and smooth muscle cells in late-delayed RIBI and contributes to perivascular ECM, which we postulate may contribute to diffusion barrier formation. We propose that pathways that antagonize fibronectin deposition and matrix assembly or enhance degradation may serve as potential therapeutic targets in RIBI.

Chemo-manipulation of tumor blood vessels by a metal-based anticancer complex enhances antitumor therapy

Human pleural mesothelioma is an incurable and chemoresistant cancer. Using a nude mouse xenograft model of human pleural mesothelioma, we show that RAPTA-T, a compound undergoing preclinical evaluation, enhances tumor vascular function by decreasing blood vessel tortuosity and dilation, while increasing the coverage of endothelial cells by pericytes and vessel perfusion within tumors. This in turn significantly reduces the interstitial fluid pressure and increases oxygenation in the tumor. Consequently, RAPTA-T pre-treatment followed by the application of cisplatin or liposomal cisplatin (Lipoplatin) leads to increased levels of the cytotoxin in the tumor and enhanced mesothelioma growth inhibition. We demonstrate that the vascular changes induced by RAPTA-T are related, in part, to the inhibition of poly-(ADP-ribose) polymerase 1 (PARP-1) which is associated to tumor vascular stabilization. These findings suggest novel therapeutic implications for RAPTA-T to create conditions for superior drug uptake and efficacy of approved cytotoxic anti-cancer drugs in malignant pleural mesothelioma and potentially other chemoresistant tumors.

Unraveling the Role of Angiogenesis in Cancer Ecosystems

Activation of the tumor and stromal cell-driven angiogenic program is one of the first requirements in the tumor ecosystem for growth and dissemination. The understanding of the dynamic angiogenic tumor ecosystem has rapidly evolved over the last decades. Beginning with the canonical sprouting angiogenesis, followed by vasculogenesis and intussusception, and finishing with vasculogenic mimicry, the need for different neovascularization mechanisms is further explored. In addition, an overview of the orchestration of angiogenesis within the tumor ecosystem cellular and molecular components is provided. Clinical evidence has demonstrated the effectiveness of traditional vessel-directed antiangiogenics, stressing on the important role of angiogenesis in tumor establishment, dissemination, and growth. Particular focus is placed on the interaction between tumor cells and their surrounding ecosystem, which is now regarded as a promising target for the development of new antiangiogenics.

Tissue Specific Origin, Development, and Pathological Perspectives of Pericytes

Pericytes are mural cells surrounding blood vessels, adjacent to endothelial cells. Pericytes play critical roles in maturation and maintenance of vascular branching morphogenesis. In the central nervous system (CNS), pericytes are necessary for the formation and regulation of the blood-brain barrier (BBB) and pericyte deficiency accompanies CNS diseases including multiple sclerosis, diabetic retinopathy, neonatal intraventricular hemorrhage, and neurodegenerative disorders. Despite the importance of pericytes, their developmental origins and phenotypic diversity remain incompletely understood. Pericytes express multiple markers and the origin of pericytes differs by tissue, which may cause difficulty for the identification and understanding of the ontogeny of pericytes. Also, pericytes have the potential to give rise to different tissues in vitro but this is not clear in vivo. These studies indicate that pericytes are heterogeneous in a tissue- and context- dependent manner. This short review focuses on recent studies about identification of pericytes, heterogeneous origin of pericytes during development and in adults, and the differentiation capacity of pericytes, and pericytes in pathological settings.

Spatiotemporal endothelial cell - pericyte association in tumors as shown by high resolution 4D intravital imaging

Endothelial cells and pericytes are integral cellular components of the vasculature with distinct interactive functionalities. To study dynamic interactions between these two cells we created two transgenic animal lines. A truncated eNOS (endothelial nitric oxide synthase) construct was used as a GFP tag for endothelial cell evaluation and an inducible Cre-lox recombination, under control of the Pdgfrb (platelet derived growth factor receptor beta) promoter, was created for pericyte assessment. Also, eNOStag-GFP animals were crossed with the already established Cspg4-DsRed mice expressing DsRed fluorescent protein in pericytes. For intravital imaging we used tumors implanted in the dorsal skinfold of these transgenic animals. This setup allowed us to study time and space dependent complexities, such as distribution, morphology, motility, and association between both vascular cell types in all angiogenetic stages, without the need for additional labeling. Moreover, as fluorescence was still clearly detectable after fixation, it is possible to perform comparative histology following intravital evaluation. These transgenic mouse lines form an excellent model to capture collective and individual cellular and subcellular endothelial cell – pericyte dynamics and will help answer key questions on the cellular and molecular relationship between these two cells.

Organotypic three-dimensional assays based on human leiomyoma-derived matrices

Alongside cancer cells, tumours exhibit a complex stroma containing a repertoire of cells, matrix molecules and soluble factors that actively crosstalk between each other. Recognition of this multifaceted concept of the tumour microenvironment (TME) calls for authentic TME mimetics to study cancer in vitro. Traditionally, tumourigenesis has been investigated in non-human, three-dimensional rat type I collagen containing organotypic discs or by means of mouse sarcoma-derived gel, such as Matrigel^®. However, the molecular compositions of these simplified assays do not properly simulate human TME. Here, we review the main properties and benefits of using human leiomyoma discs and their matrix Myogel for in vitro assays. Myoma discs are practical for investigating the invasion of cancer cells, as are cocultures of cancer and stromal cells in a stiff, hypoxic TME mimetic. Myoma discs contain soluble factors and matrix molecules commonly present in neoplastic stroma. In Transwell, IncuCyte, spheroid and sandwich assays, cancer cells move faster and form larger colonies in Myogel than in Matrigel^®. Additionally, Myogel can replace Matrigel^® in hanging-drop and tube-formation assays. Myogel also suits three-dimensional drug testing and extracellular vesicle interactions. To conclude, we describe the application of our myoma-derived matrices in 3D in vitro cancer assays.

This article is part of the discussion meeting issue ‘Extracellular vesicles and the tumour microenvironment’.

Implications of nestin in breast cancer pathogenesis (Review)

The aim of the present review was to summarize the current knowledge of the involvement of nestin in breast cancer (BC) pathogenesis. Nestin is a member of the class VI family of intermediate filament proteins, originally identified as a marker of neural stem cells and subsequently demonstrated to be expressed in BC and other cancer types. In normal breast tissue, nestin is expressed in the basal/myoepithelial cells of the mammary gland. In BC, nestin identifies basal-like tumours and predicts aggressive behaviour and poor prognosis. Nestin expression has also been detected in BC stem cells and newly-formed tumour vessels, being a factor in promoting invasion and metastasis. The present review provides an up-to-date overview of the involvement of nestin in processes facilitating BC pathogenesis and progression.

Antiangiogenic therapy: Markers of response, "normalization" and resistance

Currently in cancer treatment, one premise is to use antiangiogenic therapies in association with chemotherapy or radiotherapy to augment their efficacy by benefiting from the vascular "normalization" induced by antiangiogenic therapy. This concept defines the time during which the tumor blood vessels adopt normal-like morphology and functionality, i.e. the blood vessels become more mature, the perfusion augments and hypoxia decreases. To date, there is such a diversity of treatment protocols where the type of antiangiogenic to adopt, its dose and duration of administration are different, that knowing when and how to treat is problematic. In this review, we analyzed thoroughly preclinical and clinical studies that use antiangiogenic treatments to benefit from the "normalization" and showed that the effects depend on the type of antiangiogenic administrated (anti-VEGF, anti-VEGFR, Multi-Kinase Inhibitor) and on the duration of treatment. Finally, biomarkers of "normalization" and resistance that could be used in the clinic are presented.

Establishment and characterization of an embryonic pericyte cell line

OBJECTIVE

Pericytes are specialized perivascular cells embedded within the basement membrane. These cells envelope the abluminal surface of endothelial cells and promote microvessel homeostasis. Recent discoveries of unique pericyte functions, particularly in neural tissues, underscore the need for overcoming existing challenges in establishing a functionally validated pericyte cell line. Here, we present methodologies for addressing these challenges as well as an embryonic pericyte cell line for use with in vitro and ex vivo experimental models.

METHODS

We isolated an enriched population of NG2:DsRed+ pericytes from E12.5 mice. This pericyte cell line was compared to MEFs with respect to gene expression, cell morphology and migration, and engagement with endothelial cells during junction stabilization and angiogenesis.

RESULTS

NG2+ pericytes displayed gene expression patterns, cell morphology, and 2D migration behaviors distinct from MEFs. In three different vessel formation models, pericytes from this line migrated to and incorporated into developing vessels. When co-cultured with HUVECs, these pericytes stimulated more robust VE-Cadherin junctions between HUVECs as compared to MEFs, as well as contributed to HUVEC organization into primitive vascular structures.

CONCLUSIONS

Our data support use of this pericyte cell line in a broad range of models to further understand pericyte functionality during normal and pathological conditions.

Pericytes in the Premetastatic Niche

The premetastatic niche formed by primary tumor-derived molecules contributes to fixation of cancer metastasis. The design of efficient therapies is limited by the current lack of knowledge about the details of cellular and molecular mechanisms involved in the premetastatic niche formation. Recently, the role of pericytes in the premetastatic niche formation and lung metastatic tropism was explored by using state-of-the-art techniques, including in vivo lineage-tracing and mice with pericyte-specific KLF4 deletion. Strikingly, genetic inactivation of KLF4 in pericytes inhibits pulmonary pericyte expansion and decreases metastasis in the lung. Here, we summarize and evaluate recent advances in the understanding of pericyte contribution to premetastatic niche formation. Cancer Res; 78(11); 2779-86. ©2018 AACR.

A single dose of intravenous combretastatin A4-phosphate is reasonably well tolerated and significantly reduces tumour vascularization in canine spontaneous cancers

Combretastatin A4-phosphate (CA4P) is an anti-tumour vascular targeting agent which selectively blocks tumour blood flow. Research on CA4P in rodent tumour models is extensive; however, knowledge of its effect on spontaneous cancer is scarce. This study was conducted in canine patients with spontaneous solid tumours. The goal was to assess the toxicity and efficacy of CA4P in various spontaneous tumour types. Eight dogs with spontaneous tumours were enrolled and treated with a single dose of 75 mg m^-2 intravenous CA4P. The dogs were screened and monitored before and after injection. Pre- and post-treatment tumour blood flow was analysed in vivo by power Doppler ultrasound (PDUS) and contrast-enhanced ultrasound (CEUS). Vessel destruction and tumour necrosis were evaluated by histopathology. Clinically relevant toxicity was limited to one case of temporary tetraparesis; other adverse events were mild. Significant cardiovascular changes were mostly confined to changes in heart rate and cTnI levels. Macroscopic tumour size reduction was evident in 2 dogs. Based on PDUS and CEUS, CA4P induced a significant decrease in vascular index and tumour blood flow. Post-treatment, histopathology revealed a significant increase of necrotic tumoural tissue and a significant reduction in microvessel density in tumoural tissue. Anti-vascular and necrotizing effects of CA4P were documented in a variety of canine spontaneous cancers with only minimal side effects. This is the first study reporting the administration of CA4P to canine cancer patients with in vivo and ex vivo assessment, and a first step toward implementing CA4P in combination therapies in veterinary oncology patients. The use of CA4P in canine patients was approved and registered by the Belgian Federal Agency for Medicines and Health Products (FAMHP) (approval number 0002588, registration number 6518 ID 2F12).

BaTiO3-core Au-shell nanoparticles for photothermal therapy and bimodal imaging

We report sub-100 nm metal-shell (Au) dielectric-core (BaTiO₃) nanoparticles with bimodal imaging abilities and enhanced photothermal effects. The nanoparticles efficiently absorb light in the near infrared range of the spectrum and convert it to heat to ablate tumors. Their BaTiO₃ core, a highly ordered non-centrosymmetric material, can be imaged by second harmonic generation, and their Au shell generates two-photon luminescence. The intrinsic dual imaging capability allows investigating the distribution of the nanoparticles in relation to the tumor vasculature morphology during photothermal ablation. Our design enabled in vivo real-time tracking of the BT-Au-NPs and observation of their thermally-induced effect on tumor vessels.

STATEMENT OF SIGNIFICANCE

Photothermal therapy induced by plasmonic nanoparticles has emerged as a promising approach to treating cancer. However, the study of the role of intratumoral nanoparticle distribution in mediating tumoricidal activity has been hampered by the lack of suitable imaging techniques. This work describes metal-shell (Au) dielectric-core (BaTiO₃) nanoparticles (abbreviated as BT-Au-NP) for photothermal therapy and bimodal imaging. We demonstrated that sub-100 nm BT-Au-NP can efficiently absorb near infrared light and convert it to heat to ablate tumors. The intrinsic dual imaging capability allowed us to investigate the distribution of the nanoparticles in relation to the tumor vasculature morphology during photothermal ablation, enabling in vivo real-time tracking of the BT-Au-NPs and observation of their thermally-induced effect on tumor vessels.

Lysophosphatidic Acid Receptor 4 Activation Augments Drug Delivery in Tumors by Tightening Endothelial Cell-Cell Contact

Vascular normalization in tumors may improve drug delivery and anti-tumor immunity. Angiogenesis inhibitors induce hypoxia, which may facilitate malignant progression; therefore, we investigated other methods to promote vascular maturation. Here, we show that lysophosphatidic acid (LPA) enhances blood flow by promoting fine vascular networks, thereby improving vascular permeability and suppressing tumor growth when combined with anti-cancer drug treatment. Six different G protein-coupled receptors have been identified as LPA receptors (LPA1-6). In studies using mutant mice, we found that LPA4 is involved in vascular network formation. LPA4 activation induces circumferential actin bundling beneath the cell membrane and enhances linear adherens junction formation by VE-cadherin in endothelial cells. Therefore, we conclude that activation of LPA4 is a promising approach for vascular regulation.

Glioblastoma-activated pericytes support tumor growth via immunosuppression

Glioblastoma multiforme is the most common and aggressive primary brain tumor, with an extremely poor prognosis. The lack of detailed knowledge about the cellular and molecular mechanisms involved in glioblastoma development restricts the design of efficient therapies. A recent study using state-of-art technologies explores the role of pericytes in the glioblastoma microenvironment. Glioblastoma-activated pericytes develop an immunosuppressive phenotype, reducing T-cell activation through the induction of an anti-inflammatory response. Strikingly, pericytes support glioblastoma growth in vitro and in vivo. Here, we describe succinctly the results and implications of the findings reported in pericytes' and glioblastomas' biology. The emerging knowledge from this study will be essential for the treatment of brain tumors.

Lumbar sympathectomy regulates vascular cell turnover in rat hindfoot plantar skin

BACKGROUND

Sympathetic denervation and impaired angiogenesis cause skin diseases. However, the relationship between the sympathetic nervous system and vascular cell turnover in normal skin remains unclear.

OBJECTIVE

To determine the effects of sympathetic denervation on vascular cell turnover in normal skin.

METHODS

Rats underwent bilateral L2-4 sympathetic trunk resection (sympathectomy group) or sham operation (control). Hindfoot plantar skin was analyzed 2 weeks and 3 months postoperatively.

RESULTS

Mural cell marker (α-smooth muscle actin; p < 0.001, and desmin; p = 0.047) expression decreased 2 weeks after sympathectomy, but recovered 3 months after sympathectomy (p > 0.05). CD31 levels were lower in the experimental group than in the control group at 2 weeks (p = 0.009), but not at 3 months. Von Willebrand factor, vascular endothelial growth factor, and angiopoietin-2 expression were not significantly different between the groups (p > 0.05). Angiopoietin-1 expression levels were higher in the experimental group than in the control group at 2 weeks (p = 0.035), but not at 3 months.

CONCLUSIONS

Lumbar sympathectomy regulates vascular cell turnover in rat hindfoot plantar skin by inhibiting mural cell proliferation and increasing angiopoietin-1 expression. Sympathetic nerves therefore play an important role in plantar skin vascular cell turnover.

Angiogenesis: Managing the Culprits behind Tumorigenesis and Metastasis

Deregulated angiogenesis has been identified as a key contributor in a number of pathological conditions including cancer. It is a complex process, which involves highly regulated interaction of multiple signalling molecules. The pro-angiogenic signalling molecule, vascular endothelial growth factor (VEGF) and its cognate receptor 2 (VEGFR-2), which is often highly expressed in majority of human cancers, plays a central role in tumour angiogenesis. Owing to the importance of tumour vasculature in carcinogenesis, tumour blood vessels have emerged as an excellent therapeutic target. The anti-angiogenic therapies have been shown to arrest growth of solid tumours through multiple mechanisms, halting the expansion of tumour vasculature and transient normalization of tumour vasculature which help in the improvement of blood flow resulting in more uniform delivery of cytotoxic agents to the core of tumour mass. This also helps in reduction of hypoxia and interstitial pressure leading to reduced chemotherapy resistance and more uniform delivery of cytotoxic agents at the targeted site. Thus, complimentary combination of different agents that target multiple molecules in the angiogenic cascade may optimize inhibition of angiogenesis and improve clinical benefit in the cancer patients. This review provides an update on the current trend in exploitation of angiogenesis pathways as a strategy in the treatment of cancer.