CAFs vs. TECs: when blood feuds fuel cancer progression, dissemination and therapeutic resistance

Neoplastic progression involves complex interactions between cancer cells and the surrounding stromal milieu, fostering microenvironments that crucially drive tumor progression and dissemination. Of these stromal constituents, cancer-associated fibroblasts (CAFs) emerge as predominant inhabitants within the tumor microenvironment (TME), actively shaping multiple facets of tumorigenesis, including cancer cell proliferation, invasiveness, and immune evasion. Notably, CAFs also orchestrate the production of pro-angiogenic factors, fueling neovascularization to sustain the metabolic demands of proliferating cancer cells. Moreover, CAFs may also directly or indirectly affect endothelial cell behavior and vascular architecture, which may impact in tumor progression and responses to anti-cancer interventions. Conversely, tumor endothelial cells (TECs) exhibit a corrupted state that has been shown to affect cancer cell growth and inflammation. Both CAFs and TECs are emerging as pivotal regulators of the TME, engaging in multifaceted biological processes that significantly impact cancer progression, dissemination, and therapeutic responses. Yet, the intricate interplay between these stromal components and the orchestrated functions of each cell type remains incompletely elucidated. In this review, we summarize the current understanding of the dynamic interrelationships between CAFs and TECs, discussing the challenges and prospects for leveraging their interactions towards therapeutic advancements in cancer.

TNFα-mediated necroptosis in brain endothelial cells as a potential mechanism of increased seizure susceptibility in mice following systemic inflammation

BACKGROUND

Systemic inflammation is a potent contributor to increased seizure susceptibility. However, information regarding the effects of systemic inflammation on cerebral vascular integrity that influence neuron excitability is scarce. Necroptosis is closely associated with inflammation in various neurological diseases. In this study, necroptosis was hypothesized to be involved in the mechanism underlying sepsis-associated neuronal excitability in the cerebrovascular components (e.g., endothelia cells).

METHODS

Lipopolysaccharide (LPS) was used to induce systemic inflammation. Kainic acid intraperitoneal injection was used to measure the susceptibility of the mice to seizure. The pharmacological inhibitors C87 and GSK872 were used to block the signaling of TNFα receptors and necroptosis. In order to determine the features of the sepsis-associated response in the cerebral vasculature and CNS, brain tissues of mice were obtained for assays of the necroptosis-related protein expression, and for immunofluorescence staining to identify morphological changes in the endothelia and glia. In addition, microdialysis assay was used to assess the changes in extracellular potassium and glutamate levels in the brain.

RESULTS

Some noteworthy findings, such as increased seizure susceptibility and brain endothelial necroptosis, Kir4.1 dysfunction, and microglia activation were observed in mice following LPS injection. C87 treatment, a TNFα receptor inhibitor, showed considerable attenuation of increased kainic acid-induced seizure susceptibility, endothelial cell necroptosis, microglia activation and restoration of Kir4.1 protein expression in LPS-treated mice. Treatment with GSK872, a RIP3 inhibitor, such as C87, showed similar effects on these changes following LPS injection.

CONCLUSIONS

The findings of this study showed that TNFα-mediated necroptosis induced cerebrovascular endothelial damage, neuroinflammation and astrocyte Kir4.1 dysregulation, which may coalesce to contribute to the increased seizure susceptibility in LPS-treated mice. Pharmacologic inhibition targeting this necroptosis pathway may provide a promising therapeutic approach to the reduction of sepsis-associated brain endothelia cell injury, astrocyte ion channel dysfunction, and subsequent neuronal excitability.

Analysis of cerebrovascular dysfunction caused by chronic social defeat in mice

Psychological stress and affective disorders are clinically associated with hypertension and vascular disease, but the biological links between the conditions have not been fully explored. To examine this relationship, we used chronic social defeat (CSD) stress, which produces anxiety-like and depressive-like behavioral declines in susceptible mice. In such mice, CSD also produces cerebrovascular microbleeds in scattered locations. Here, we showed further evidence of vascular pathology and blood-brain barrier breakdown by visualizing plasma immunoglobulins and erythrocytes within the parenchyma and perivascular spaces of CSD brains. To further characterize the impact of stress on the cerebrovasculature, brain endothelial cells (bECs) were isolated, and global gene expression profiles were generated. Bioinformatic analysis of CSD-induced transcriptional changes in bECs showed enrichment in pathways that delineate the vascular response to injury. These pathways followed a temporal sequence of inflammation, oxidative stress, growth factor signaling, and wound healing (i.e., platelet aggregation, hemostasis, fibrinogen deposition, and angiogenesis). Immunohistochemical staining for markers of fibrinogen deposition and angiogenesis confirmed the existence of the markers at the sites of vascular disruptions. Recovery after CSD cessation was marked by recruitment of leukocytes perhaps participating in vascular repair. The data suggest that co-morbidity of affective disorders and vascular diseases may be attributed in part to a common link in altered endothelial cell function.

Reciprocal communication between astrocytes and endothelial cells is required for astrocytic glutamate transporter 1 (GLT-1) expression

Astrocytes have diverse functions that are supported by their anatomic localization between neurons and blood vessels. One of these functions is the clearance of extracellular glutamate. Astrocytes clear glutamate using two Na⁺-dependent glutamate transporters, GLT-1 (also called EAAT2) and GLAST (also called EAAT1). GLT-1 expression increases during synaptogenesis and is a marker of astrocyte maturation. Over 20 years ago, several groups demonstrated that astrocytes in culture express little or no GLT-1 and that neurons induce expression. We recently demonstrated that co-culturing endothelia with mouse astrocytes also induced expression of GLT-1 and GLAST. These increases were blocked by an inhibitor of γ-secretase. This and other observations are consistent with the hypothesis that Notch signaling is required, but the ligands involved were not identified. In the present study, we used rat astrocyte cultures to further define the mechanisms by which endothelia induce expression of GLT-1 and GLAST. We found that co-cultures of astrocytes and endothelia express higher levels of GLT-1 and GLAST protein and mRNA. That endothelia activate Hes5, a transcription factor target of Notch, in astrocytes. Using recombinant Notch ligands, anti-Notch ligand neutralizing antibodies, and shRNAs, we provide evidence that both Dll1 and Dll4 contribute to endothelia-dependent regulation of GLT-1. We also provide evidence that astrocytes secrete a factor(s) that induces expression of Dll4 in endothelia and that this effect is required for Notch-dependent induction of GLT-1. Together these studies indicate that reciprocal communication between astrocytes and endothelia is required for appropriate astrocyte maturation and that endothelia likely deploy additional non-Notch signals to induce GLT-1.

Effects of hydroxyethyl starch (HES 130/0.42) on endothelial and epithelial permeability in vitro

Hydroxyethyl starch (HES) is employed to sustain normovolemia in patients. Using a perfused organ model, we recently showed that HES impairs the intestinal barrier which is constituted of endothelial and epithelial cell layers. However, the target cells and molecular actions of HES in the intestine are mainly unknown. Employing a model of human endothelial (HUVEC) and intestinal epithelial cells (Caco-2), we investigated the impact of HES, albumin and HES/albumin on cellular integrity/permeability and evaluated underlying molecular mechanisms. Monolayers of HUVEC and Caco-2 were cultured with HES (3%), albumin (3%) or HES/albumin (1.5%/1.5%). Integrity and permeability of the cell layers were evaluated by FITC-dextran transfer, measurements of cell detachment, vitality, cell volume, LDH release and caspase-3/7 activity. Cellular mechanisms were analyzed by Westernblotting for P-akt, P-erk, claudin-3 and I-FABP. HES application resulted in higher numbers of non-adherent/floating HUVEC cells (P<0.05) but did not change vitality or cell volume. Both, HES and HES/albumin increased the permeability of HUVEC monolayers (P<0.001), while LDH release, caspase-3/7 activity, akt/erk phosphorylation and claudin-3 expression were not affected. HES and HES/albumin did not change any of the parameters in cultures of Caco-2 cells. HES is able to disturb the integrity of the endothelial but not the epithelial barrier in vitro. HES effects are unrelated to cell damage and apoptosis but may involve reduced cell-cell or cell-matrix adhesion.

Poly(ADP-ribose) polymerase-1 regulates microglia mediated decrease of endothelial tight junction integrity

Alzheimer's disease pathology includes, beside neuronal damage, reactive gliosis and reduced blood-brain barrier (BBB) integrity. Microglia are intimately associated with the BBB and upon AD pathology, pro-inflammatory responses of microglia could contribute to BBB damage. To study whether microglia can directly affect BBB integrity, the effects of amyloid beta (Aβ) -stimulated primary murine microglia on co-cultured mouse brain endothelial cells (bEnd3) and murine astrocyte cultures were assessed. We also assessed whether microglial phenotype modulation via poly(ADP-ribose) polymerase-1 (PARP-1) inhibition/ablation can reverse microglial impact on these BBB forming cells. Unstimulated microglia promoted expression of tight junction proteins (TJPs), zonula ocluden-1 (ZO-1) and occludin in co-cultured endothelia cells, whereas Aβ-stimulated microglia reduced endothelial expression of ZO-1 and occludin. Astrocytes co-cultured with microglia showed elevated glial fibrillary acidic protein (GFAP) expression, which was further increased if microglia had been stimulated with Aβ. Aβ induced microglial release of nitric oxide (NO) and tumour necrosis factor alpha (TNFα), which resulted in reduced endothelial expression of TJPs and increased paracellular permeability. Microglial PARP-1 inhibition attenuated these Aβ-induced events. These findings demonstrate that PARP-1 mediated microglial responses (NO and TNFα) can directly reduce BBB integrity by promoting TJP degradation, increasing endothelial cell permeability and inducing astrogliosis. PARP-1 as a modulator of microglial phenotype can prevent microglial BBB damaging events, and thus is a potential therapeutic target.

Astrocytes Can Adopt Endothelial Cell Fates in a p53-Dependent Manner

Astrocytes respond to a variety of CNS injuries by cellular enlargement, process outgrowth, and upregulation of extracellular matrix proteins that function to prevent expansion of the injured region. This astrocytic response, though critical to the acute injury response, results in the formation of a glial scar that inhibits neural repair. Scar-forming cells (fibroblasts) in the heart can undergo mesenchymal-endothelial transition into endothelial cell fates following cardiac injury in a process dependent on p53 that can be modulated to augment cardiac repair. Here, we sought to determine whether astrocytes, as the primary scar-forming cell of the CNS, are able to undergo a similar cellular phenotypic transition and adopt endothelial cell fates. Serum deprivation of differentiated astrocytes resulted in a change in cellular morphology and upregulation of endothelial cell marker genes. In a tube formation assay, serum-deprived astrocytes showed a substantial increase in vessel-like morphology that was comparable to human umbilical vein endothelial cells and dependent on p53. RNA sequencing of serum-deprived astrocytes demonstrated an expression profile that mimicked an endothelial rather than astrocyte transcriptome and identified p53 and angiogenic pathways as specifically upregulated. Inhibition of p53 with genetic or pharmacologic strategies inhibited astrocyte-endothelial transition. Astrocyte-endothelial cell transition could also be modulated by miR-194, a microRNA downstream of p53 that affects expression of genes regulating angiogenesis. Together, these studies demonstrate that differentiated astrocytes retain a stimulus-dependent mechanism for cellular transition into an endothelial phenotype that may modulate formation of the glial scar and promote injury-induced angiogenesis.

Seeing is Believing, or How GFP Changed My Approach to Science

The field of "Developmental Biology" has dramatically changed over the past three decades. While genetic analysis had been center stage in the 1980s and continues to be a corner stone for investigations, the introduction of green fluorescent protein (GFP) in the 1990s has allowed us to look into living, developing embryos, and see how cells form tissues and how organ morphogenesis proceeds in real time. The introduction of protein binders into developmental studies some years ago has raised the precision yet another step, since it will allow the manipulation and study of how proteins function in real time. This chapter is a personal account on how GFP has, and how protein binders may, change the design of studies in the field of developmental biology.

Bioenergetic disruption of human micro-vascular endothelial cells by antipsychotics

Antipsychotics (APs) are widely used medications, however these are not without side effects such as disruption of blood brain barrier function (BBB). To investigate this further we have studied the chronic effects of the typical APs, chlorpromazine (CPZ) and haloperidol (HAL) and the atypical APs, risperidone (RIS) and clozapine (CLZ), on the bioenergetics of human micro-vascular endothelial cells (HBVECs) of the BBB. Alamar blue (AB) and ATP assays showed that these APs impair bioenergenesis in HBVECs in a concentration and time dependent manner. However since these effects were incomplete they suggest a population of cell bioenergetically heterogeneous, an idea supported by the bistable nature by which APs affected the mitochondrial transmembrane potential. CPZ, HAL and CLZ inhibited the activity of mitochondrial complexes I and III. Our data demonstrates that at therapeutic concentrations, APs can impair the bioenergetic status of HBVECs, an action that help explains the adverse side effects of these drugs when used clinically.

Upregulation of ICAM-1 in diabetic rats after transient forebrain ischemia and reperfusion injury

Background

Hyperglycemia exacerbates brain damage caused by cerebral ischemia. Neuroinflammation may play a role in mediating such enhanced damage. The objectives of this study were to examine the mRNA and protein levels and cell type distribution of ICAM-1 after cerebral ischemia in normo-and diabetic hyperglycemic rats.

Results

Compared to normoglycemic ischemia animals, diabetes aggravated neuronal death, decreased Nissl body staining, and increased ICAM-1 mRNA and protein levels in the frontal cortex. The increased ICAM-1 was located not only in vascular endothelial cells but also in cortical neurons.

Conclusions

Our results suggest that exacerbated neuro-inflammation in the brain may mediate the detrimental effects of diabetes on the ischemic brain.

Endothelial cell-derived plasmin promotes human glioma cell proliferation

The pathogenesis of glioma is unclear. The therapeutic results are very poor currently. This study aims to investigate the endothelial cell-derived plasminogen in the promotion of glioma cell proliferation. The results showed that after exposure to polyIC, the production of plasminogen by Huvecs was markedly increased. Plasmin cleaved PAR2 on glioma cells to induce the release of IL-6 from glioma cells. Tregs differentiated into Th17(+) cells induced by IL-6 in conjunction with TGF-β in Tregs. The Th17 cells released IL-17 to facilitate the glioma cell growth. We conclude that the vascular endothelial cell-derived plasmin induces the release IL-6 from glioma cells. The IL-6 induces the production of IL-17 by Tregs. The IL-17(+) Tregs promote the glioma cell proliferation.

Leukocyte infiltration into spinal cord of EAE mice is attenuated by removal of endothelial leptin signaling

Leptin, a pleiotropic adipokine, crosses the blood-brain barrier (BBB) and blood-spinal cord barrier (BSCB) from the periphery and facilitates experimental autoimmune encephalomyelitis (EAE). EAE induces dynamic changes of leptin receptors in enriched brain and spinal cord microvessels, leading to further questions about the potential roles of endothelial leptin signaling in EAE progression. In endothelial leptin receptor specific knockout (ELKO) mice, there were lower EAE behavioral scores in the early phase of the disorder, better preserved BSCB function shown by reduced uptake of sodium fluorescein and leukocyte infiltration into the spinal cord. Flow cytometry showed that the ELKO mutation decreased the number of CD3 and CD45 cells in the spinal cord, although immune cell profiles in peripheral organs were unchanged. Not only were CD4(+) and CD8(+) T lymphocytes reduced, there were also lower numbers of CD11b(+)Gr1(+) granulocytes in the spinal cord of ELKO mice. In enriched microvessels from the spinal cord of the ELKO mice, the decreased expression of mRNAs for a few tight junction proteins was less pronounced in ELKO than WT mice, as was the elevation of mRNA for CCL5, CXCL9, IFN-γ, and TNF-α. Altogether, ELKO mice show reduced inflammation at the level of the BSCB, less leukocyte infiltration, and better preserved tight junction protein expression and BBB function than WT mice after EAE. Although leptin concentrations were high in ELKO mice and microvascular leptin receptors show an initial elevation before inhibition during the course of EAE, removal of leptin signaling helped to reduce disease burden. We conclude that endothelial leptin signaling exacerbates BBB dysfunction to worsen EAE.

Tubulogenesis

Metazoans require epithelial and endothelial tubes to transport liquids and gasses throughout their bodies. Although biological tubes may look relatively similar at first glance, there are multiple and distinct mechanisms by which tubes form and even more regulatory events driving the cell shape changes that produce tubes of specific dimensions. An overview of the current understanding of the molecular processes and physical forces involved in tubulogenesis is presented in this review and the accompanying poster.

Reduced ingestion of sweetened milk induced by interleukin-1 and lipopolysaccharide is associated with induction of cyclooxygenase-2 in brain endothelia

Previous studies have shown that interleukin-1 (IL-1) and lipopolysaccharide (LPS) administration to animals induces behavioral changes, including a reduction in feeding. These effects of IL-1 and LPS have been shown to be sensitive to inhibitors of cyclooxygenase (COX).

OBJECTIVES

To determine the relationships between induction of COX-2 in the brain with IL-1beta- and LPS-induced changes in body temperature, plasma corticosterone and feeding.

METHODS

Mice were injected with intraperitoneal doses of IL-1beta and LPS that decreased feeding. The induction of COX-2 was studied immunocytochemically in the brain, in parallel with core body temperature, the drinking of sweetened milk, and plasma concentrations of corticosterone.

RESULTS

COX-2 immunoreactivity (ir) was sparse in the brains of the untreated mice, but IL-1beta and LPS both increased its expression. This COX-2 induction appeared to be confined to blood vessels, and was not markedly region specific. Induction was evident 30 min after IL-1 or LPS, and was greater at 90 than at 30 min. COX-2-ir in the parenchyma did not change significantly. Thus induction of COX-2 occurred in brain endothelia in parallel with the reduction in feeding. This is consistent with the previously determined sensitivity of IL-1-induced changes in feeding to selective COX-2 inhibitors, and the responses to IL-1 in COX-2-deficient mice. The time courses of the IL-1- and LPS-induced increases in plasma corticosterone paralleled those in the reduction in milk drinking, however, the changes in body temperature appeared later.

CONCLUSIONS

Endothelial COX-2 may be involved in IL-1- and LPS-induced decreases in milk drinking, and possibly in the HPA axis activation. The decreased milk drinking may occur when IL-1 and LPS bind to receptors on brain endothelial cells subsequently inducing COX-2 and the production of prostanoids which elicit the reductions in milk drinking. Thus the behavioral effects of peripherally administered IL-1 and LPS appear to be mediated by multiple mechanisms, including endothelial COX-2, and vagal afferents.