Quantitatively relating brain endothelial cell-cell junction phenotype to global and local barrier properties under varied culture conditions via the Junction Analyzer Program

Bridging barriers: advances and challenges in modeling biological barriers and measuring barrier integrity in organ-on-chip systems

Biological barriers such as the blood-brain barrier, skin, and intestinal mucosal barrier play key roles in homeostasis, disease physiology, and drug delivery - as such, it is important to create representative in vitro models to improve understanding of barrier biology and serve as tools for therapeutic development. Microfluidic cell culture and organ-on-a-chip (OOC) systems enable barrier modelling with greater physiological fidelity than conventional platforms by mimicking key environmental aspects such as fluid shear, accurate microscale dimensions, mechanical cues, extracellular matrix, and geometrically defined co-culture. As the prevalence of barrier-on-chip models increases, so does the importance of tools that can accurately assess barrier integrity and function without disturbing the carefully engineered microenvironment. In this review, we first provide a background on biological barriers and the physiological features that are emulated through in vitro barrier models. Then, we outline molecular permeability and electrical sensing barrier integrity assessment methods, and the related challenges specific to barrier-on-chip implementation. Finally, we discuss future directions in the field, as well important priorities to consider such as fabrication costs, standardization, and bridging gaps between disciplines and stakeholders.

Cortistatin deficiency reveals a dysfunctional brain endothelium with impaired gene pathways, exacerbated immune activation, and disrupted barrier integrity

BACKGROUND

Brain activity governing cognition and behaviour depends on the fine-tuned microenvironment provided by a tightly controlled blood-brain barrier (BBB). Brain endothelium dysfunction is a hallmark of BBB breakdown in most neurodegenerative/neuroinflammatory disorders. Therefore, the identification of new endogenous molecules involved in endothelial cell disruption is essential to better understand BBB dynamics. Cortistatin is a neuroimmune mediator with anti-inflammatory and neuroprotective properties that exerts beneficial effects on the peripheral endothelium. However, its role in the healthy and injured brain endothelium remains to be evaluated. Herein, this study aimed to investigate the potential function of endogenous and therapeutic cortistatin in regulating brain endothelium dysfunction in a neuroinflammatory/neurodegenerative environment.

METHODS

Wild-type and cortistatin-deficient murine brain endothelium and human cells were used for an in vitro barrier model, where a simulated ischemia-like environment was mimicked. Endothelial permeability, junction integrity, and immune response in the presence and absence of cortistatin were evaluated using different size tracers, immunofluorescence labelling, qPCR, and ELISA. Cortistatin molecular mechanisms underlying brain endothelium dynamics were assessed by RNA-sequencing analysis. Cortistatin role in BBB leakage was evaluated in adult mice injected with LPS.

RESULTS

The endogenous lack of cortistatin predisposes endothelium weakening with increased permeability, tight-junctions breakdown, and dysregulated immune activity. We demonstrated that both damaged and uninjured brain endothelial cells isolated from cortistatin-deficient mice, present a dysregulated and/or deactivated genetic programming. These pathways, related to basic physiology but also crucial for the repair after damage (e.g., extracellular matrix remodelling, angiogenesis, response to oxygen, signalling, and metabolites transport), are dysfunctional and make brain endothelial barrier lacking cortistatin non-responsive to any further injury. Treatment with cortistatin reversed in vitro hyperpermeability, tight-junctions disruption, inflammatory response, and reduced in vivo BBB leakage.

CONCLUSIONS

The neuropeptide cortistatin has a key role in the physiology of the cerebral microvasculature and its presence is crucial to develop a canonical balanced response to damage. The reparative effects of cortistatin in the brain endothelium were accompanied by the modulation of the immune function and the rescue of barrier integrity. Cortistatin-based therapies could emerge as a novel pleiotropic strategy to ameliorate neuroinflammatory/neurodegenerative disorders with disrupted BBB.

20 kDa isoform of connexin-43 augments spatial reorganization of the brain endothelial junctional complex and lesion leakage in cerebral cavernous malformation type-3

Cerebral cavernous malformation type-3 (CCM3) is a type of brain vascular malformation caused by mutations in programmed cell death protein-10 (PDCD10). It is characterized by early life occurrence of hemorrhagic stroke and profound blood-brain barrier defects. The pathogenic mechanisms responsible for microvascular hyperpermeability and lesion progression in CCM3 are still largely unknown. The current study examined brain endothelial barrier structural defects formed in the absence of CCM3 in vivo and in vitro that may lead to CCM3 lesion leakage. We found significant upregulation of a 20 kDa isoform of connexin 43 (GJA1-20 k) in brain endothelial cells (BEC) in both non-leaky and leaky lesions, as well as in an in vitro CCM3 knockdown model (CCM3KD-BEC). Morphological, biochemical, FRET, and FRAP analyses of CCM3KD-BEC found GJA1-20 k regulates full-length GJA1 biogenesis, prompting uncontrolled gap junction growth. Furthermore, by binding to a tight junction scaffolding protein, ZO-1, GJA1-20 k interferes with Cx43/ZO-1 interactions and gap junction/tight junction crosstalk, promoting ZO-1 dissociation from tight junction complexes and diminishing claudin-5/ZO-1 interaction. As a consequence, the tight junction complex is destabilized, allowing "replacement" of tight junctions with gap junctions leading to increased brain endothelial barrier permeability. Modifying cellular levels of GJA1-20 k rescued brain endothelial barrier integrity re-establishing the spatial organization of gap and tight junctional complexes. This study highlights generation of potential defects at the CCM3-affected brain endothelial barrier which may underlie prolonged vascular leakiness.

A Rapid-Patterning 3D Vessel-on-Chip for Imaging and Quantitatively Analyzing Cell-Cell Junction Phenotypes

The blood-brain barrier (BBB) is a dynamic interface that regulates the molecular exchanges between the brain and peripheral blood. The permeability of the BBB is primarily regulated by the junction proteins on the brain endothelial cells. In vitro BBB models have shown great potential for the investigation of the mechanisms of physiological function, pathologies, and drug delivery in the brain. However, few studies have demonstrated the ability to monitor and evaluate the barrier integrity by quantitatively analyzing the junction presentation in 3D microvessels. This study aimed to fabricate a simple vessel-on-chip, which allows for a rigorous quantitative investigation of junction presentation in 3D microvessels. To this end, we developed a rapid protocol that creates 3D microvessels with polydimethylsiloxane and microneedles. We established a simple vessel-on-chip model lined with human iPSC-derived brain microvascular endothelial-like cells (iBMEC-like cells). The 3D image of the vessel structure can then be "unwrapped" and converted to 2D images for quantitative analysis of cell-cell junction phenotypes. Our findings revealed that 3D cylindrical structures altered the phenotype of tight junction proteins, along with the morphology of cells. Additionally, the cell-cell junction integrity in our 3D models was disrupted by the tumor necrosis factor α. This work presents a "quick and easy" 3D vessel-on-chip model and analysis pipeline, together allowing for the capability of screening and evaluating the cell-cell junction integrity of endothelial cells under various microenvironment conditions and treatments.

Matrix stiffness regulates the tight junction phenotypes and local barrier properties in tricellular regions in an iPSC-derived BBB model

The blood-brain barrier (BBB) can respond to various mechanical cues such as shear stress and substrate stiffness. In the human brain, the compromised barrier function of the BBB is closely associated with a series of neurological disorders that are often also accompanied by the alteration of brain stiffness. In many types of peripheral vasculature, higher matrix stiffness decreases barrier function of endothelial cells through mechanotransduction pathways that alter cell-cell junction integrity. However, human brain endothelial cells are specialized endothelial cells that largely resist changes in cell morphology and key BBB markers. Therefore, it has remained an open question how matrix stiffness affects barrier integrity in the human BBB. To gain insight into the effects of matrix stiffness on BBB permeability, we differentiated brain microvascular endothelial-like cells from human induced pluripotent stem cells (iBMEC-like cells) and cultured the cells on extracellular matrix-coated hydrogels of varying stiffness. We first detected and quantified the junction presentation of key tight junction (TJ) proteins. Our results show matrix-dependent junction phenotypes in iBMEC-like cells, where cells on softer gels (1 kPa) have significantly lower continuous and total TJ coverages. We also determined that these softer gels also lead to decreased barrier function in a local permeability assay. Furthermore, we found that matrix stiffness regulates the local permeability of iBMEC-like cells through the balance of continuous ZO-1 TJs and no junction regions ZO-1 in tricellular regions. Together, these findings provide valuable insights into the effects of matrix stiffness on TJ phenotypes and local permeability of iBMEC-like cells. STATEMENT OF SIGNIFICANCE: Brain mechanical properties, including stiffness, are particularly sensitive indicators for pathophysiological changes in neural tissue. The compromised function of the blood-brain barrier is closely associated with a series of neurological disorders often accompanied by altered brain stiffness. In this study, we use polymeric biomaterials and provide new evidence that biomaterial stiffness regulates the local permeability in iPSC-derived brain endothelial cells in tricellular regions through the tight junction protein ZO-1. Our findings provide valuable insights into the changes in junction architecture and barrier permeability in response to different substrate stiffnesses. Since BBB dysfunction has been linked to many diseases, understanding the influence of substrate stiffness on junction presentations and barrier permeability could lead to the development of new treatments for diseases associated with BBB dysfunction or drug delivery across BBB systems.

A novel mitochondria-related gene signature in esophageal carcinoma: prognostic, immune, and therapeutic features

Esophageal carcinoma (ESCA) is a common and lethal malignant tumor worldwide. The mitochondrial biomarkers were useful in finding significant prognostic gene modules associated with ESCA owing to the role of mitochondria in tumorigenesis and progression. In the present work, we obtained the transcriptome expression profiles and corresponding clinical information of ESCA from The Cancer Genome Atlas (TCGA) database. Differential expressed genes (DEGs) were overlapped with 2030 mitochondria-related genes to get mitochondria-related DEGs. The univariate cox regression, Least Absolute Shrinkage and Selection Operator (LASSO) regression, and multivariate cox regression were sequentially used to define the risk scoring model for mitochondria-related DEGs, and its prognostic value was verified in the external datasets GSE53624. Based on the risk score, ESCA patients were divided into high- and low-risk groups. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA) were performed to further investigate the difference between low- and high-risk groups at the gene pathway level. CIBERSORT was used to evaluate immune cell infiltration. The mutation difference between high- and low-risk groups was compared by using the R package "Maftools". Cellminer was used to assess the association between the risk scoring model and drug sensitivity. As the most important outcome of the study, a 6-gene risk scoring model (APOOL, HIGD1A, MAOB, BCAP31, SLC44A2, and CHPT1) was constructed from 306 mitochondria-related DEGs. Pathways including the "hippo signaling pathway" and "cell-cell junction" were enriched in the DEGs between high and low groups. According to CIBERSORT, samples with high-risk scores demonstrated a higher abundance of CD4⁺ T cells, NK cells, M0 and M2 macrophages, and a lower abundance of M1 macrophages. The immune cell marker genes were correlated with the risk score. In mutation analysis, the mutation rate of TP53 was significantly different between the high- and low-risk groups. Drugs with a strong correlation with the risk model were selected. In conclusion, we focused on the role of mitochondria-related genes in cancer development and proposed a prognostic signature for individualized integrative assessment.

Nanostars Carrying Multifunctional Neurotrophic Dendrimers Protect Neurons in Preclinical In Vitro Models of Neurodegenerative Disorders

A challenge in neurology is the lack of efficient brain-penetrable neuroprotectants targeting multiple disease mechanisms. Plasmonic gold nanostars are promising candidates to deliver standard-of-care drugs inside the brain but have not been trialed as carriers for neuroprotectants. Here, we conjugated custom-made peptide dendrimers (termed H3/H6), encompassing motifs of the neurotrophic S100A4-protein, onto star-shaped and spherical gold nanostructures (H3/H6-AuNS/AuNP) and evaluated their potential as neuroprotectants and interaction with neurons. The H3/H6 nanostructures crossed a model blood-brain barrier, bound to plasma membranes, and induced neuritogenesis with the AuNS, showing higher potency/efficacy than the AuNP. The H3-AuNS/NP protected neurons against oxidative stress, the H3-AuNS being more potent, and against Parkinson's or Alzheimer's disease (PD/AD)-related cytotoxicity. Unconjugated S100A4 motifs also decreased amyloid beta-induced neurodegeneration, introducing S100A4 as a player in AD. Using custom-made dendrimers coupled to star-shaped nanoparticles is a promising route to activate multiple neuroprotective pathways and increase drug potency to treat neurodegenerative disorders.

Dynamic Python-Based Method Provides Quantitative Analysis of Intercellular Junction Organization During S. pneumoniae Infection of the Respiratory Epithelium

Many respiratory pathogens compromise epithelial barrier function during lung infection by disrupting intercellular junctions, such as adherens junctions and tight junctions, that maintain intercellular integrity. This includes Streptococcus pneumoniae, a leading cause of pneumonia, which can successfully breach the epithelial barrier and cause severe infections such as septicemia and meningitis. Fluorescence microscopy analysis on intercellular junction protein manipulation by respiratory pathogens has yielded major advances in our understanding of their pathogenesis. Unfortunately, a lack of automated image analysis tools that can tolerate variability in sample-sample staining has limited the accuracy in evaluating intercellular junction organization quantitatively. We have created an open source, automated Python computer script called "Intercellular Junction Organization Quantification" or IJOQ that can handle a high degree of sample-sample staining variability and robustly measure intercellular junction integrity. In silico validation of IJOQ was successful in analyzing computer generated images containing varying degrees of simulated intercellular junction disruption. Accurate IJOQ analysis was further confirmed using images generated from in vitro and in vivo bacterial infection models. When compared in parallel to a previously published, semi-automated script used to measure intercellular junction organization, IJOQ demonstrated superior analysis for all in vitro and in vivo experiments described herein. These data indicate that IJOQ is an unbiased, easy-to-use tool for fluorescence microscopy analysis and will serve as a valuable, automated resource to rapidly quantify intercellular junction disruption under diverse experimental conditions.

Rhinovirus C replication is associated with the endoplasmic reticulum and triggers cytopathic effects in an in vitro model of human airway epithelium

The clinical impact of rhinovirus C (RV-C) is well-documented; yet, the viral life cycle remains poorly defined. Thus, we characterized RV-C15 replication at the single-cell level and its impact on the human airway epithelium (HAE) using a physiologically-relevant in vitro model. RV-C15 replication was restricted to ciliated cells where viral RNA levels peaked at 12 hours post-infection (hpi), correlating with elevated titers in the apical compartment at 24hpi. Notably, infection was associated with a loss of polarized expression of the RV-C receptor, cadherin-related family member 3. Visualization of double-stranded RNA (dsRNA) during RV-C15 replication revealed two distinct replication complex arrangements within the cell, likely corresponding to different time points in infection. To further define RV-C15 replication sites, we analyzed the expression and colocalization of giantin, phosphatidylinositol-4-phosphate, and calnexin with dsRNA. Despite observing Golgi fragmentation by immunofluorescence during RV-C15 infection as previously reported for other RVs, a high ratio of calnexin-dsRNA colocalization implicated the endoplasmic reticulum as the primary site for RV-C15 replication in HAE. RV-C15 infection was also associated with elevated stimulator of interferon genes (STING) expression and the induction of incomplete autophagy, a mechanism used by other RVs to facilitate non-lytic release of progeny virions. Notably, genetic depletion of STING in HAE attenuated RV-C15 and -A16 (but not -B14) replication, corroborating a previously proposed proviral role for STING in some RV infections. Finally, RV-C15 infection resulted in a temporary loss in epithelial barrier integrity and the translocation of tight junction proteins while a reduction in mucociliary clearance indicated cytopathic effects on epithelial function. Together, our findings identify both shared and unique features of RV-C replication compared to related rhinoviruses and define the impact of RV-C on both epithelial cell organization and tissue functionality–aspects of infection that may contribute to pathogenesis in vivo.

Rhinovirus C has a global distribution and significant clinical impact–especially in those with underlying lung disease. Although RV-C is genetically, structurally, and biologically distinct from RV-A and -B viruses, our understanding of the RV-C life cycle has been largely inferred from these and other related viruses. Here, we performed a detailed analysis of RV-C15 replication in a physiologically-relevant model of human airway epithelium. Our single-cell, microscopy-based approach revealed that–unlike other RVs–the endoplasmic reticulum is the primary site for RV-C15 replication. RV-C15 replication also stimulated STING expression, which was proviral, and triggered dramatic changes in cellular organization, including altered virus receptor distribution, fragmented Golgi stacks, and the induction of incomplete autophagy. Additionally, we observed a loss of epithelial barrier function and a decrease in mucociliary clearance, a major defense mechanism in the lung, during RV-C15 infection. Together, these data reveal novel insight into RV-C15 replication dynamics and resulting cytopathic effects in the primary target cells for infection, thereby furthering our understanding of the pathogenesis of RV-C. Our work highlights similar, as well as unique, aspects of RV-C15 replication compared to related pathogens, which will help guide future studies on the molecular mechanisms of RV-C infection.

Recent progress and new challenges in modeling of human pluripotent stem cell-derived blood-brain barrier

The blood-brain barrier (BBB) is a semipermeable unit that serves to vascularize the central nervous system (CNS) while tightly regulating the movement of molecules, ions, and cells between the blood and the brain. The BBB precisely controls brain homeostasis and protects the neural tissue from toxins and pathogens. The BBB is coordinated by a tight monolayer of brain microvascular endothelial cells, which is subsequently supported by mural cells, astrocytes, and surrounding neuronal cells that regulate the barrier function with a series of specialized properties. Dysfunction of barrier properties is an important pathological feature in the progression of various neurological diseases. In vitro BBB models recapitulating the physiological and diseased states are important tools to understand the pathological mechanism and to serve as a platform to screen potential drugs. Recent advances in this field have stemmed from the use of pluripotent stem cells (PSCs). Various cell types of the BBB such as brain microvascular endothelial cells (BMECs), pericytes, and astrocytes have been derived from PSCs and synergistically incorporated to model the complex BBB structure in vitro. In this review, we summarize the most recent protocols and techniques for the differentiation of major cell types of the BBB. We also discuss the progress of BBB modeling by using PSC-derived cells and perspectives on how to reproduce more natural BBBs in vitro.

Photodynamic Priming Modulates Endothelial Cell-Cell Junction Phenotype for Light-activated Remote Control of Drug Delivery

The blood-brain barrier (BBB) remains a major obstacle for drug delivery to the central nervous system. In particular, the tight and adherens junctions that join the brain capillary endothelial cells limit the diffusion of various molecules from the bloodstream into the brain. Photodynamic priming (PDP) is a non-cytotoxic modality that involves light activation of photosensitizers to photochemically modulate nearby molecules without killing the cells. Here we investigate the effects of sub-lethal photochemistry on junction phenotype (i.e., continuous, punctate, or perpendicular), as well as the BBB permeability in a transwell model of human brain microvascular endothelial cells (HBMECs). We showed that PDP decreases the continuous junction architecture by ~20%, increases the perpendicular junction architecture by ~40%, and has minimal impact on cell morphology in HBMECs. Furthermore, transwell permeability assay revealed that PDP improves the HBMEC permeability to dextran or nanoliposomes by up to 30-fold for 6-9 days. These results suggest that PDP could safely reverse the mature brain endothelial junctions without killing the HBMECs. This study not only emphasizes the critical roles of PDP in the modulation junction phenotype, but also highlights the opportunity to further develop PDP-based combinations that opens the cerebrum endothelium for enhanced drug transporter across the BBB.

Review of Design Considerations for Brain-on-a-Chip Models

In recent years, the need for sophisticated human in vitro models for integrative biology has motivated the development of organ-on-a-chip platforms. Organ-on-a-chip devices are engineered to mimic the mechanical, biochemical and physiological properties of human organs; however, there are many important considerations when selecting or designing an appropriate device for investigating a specific scientific question. Building microfluidic Brain-on-a-Chip (BoC) models from the ground-up will allow for research questions to be answered more thoroughly in the brain research field, but the design of these devices requires several choices to be made throughout the design development phase. These considerations include the cell types, extracellular matrix (ECM) material(s), and perfusion/flow considerations. Choices made early in the design cycle will dictate the limitations of the device and influence the end-point results such as the permeability of the endothelial cell monolayer, and the expression of cell type-specific markers. To better understand why the engineering aspects of a microfluidic BoC need to be influenced by the desired biological environment, recent progress in microfluidic BoC technology is compared. This review focuses on perfusable blood-brain barrier (BBB) and neurovascular unit (NVU) models with discussions about the chip architecture, the ECM used, and how they relate to the in vivo human brain. With increased knowledge on how to make informed choices when selecting or designing BoC models, the scientific community will benefit from shorter development phases and platforms curated for their application.

Ruffles and spikes: Control of tight junction morphology and permeability by claudins

Epithelial barrier function is regulated by a family of transmembrane proteins known as claudins. Functional tight junctions are formed when claudins interact with other transmembrane proteins, cytosolic scaffold proteins and the actin cytoskeleton. The predominant scaffold protein, zonula occludens-1 (ZO-1), directly binds to most claudin C-terminal domains, crosslinking them to the actin cytoskeleton. When imaged by immunofluorescence microscopy, tight junctions most frequently are linear structures that form between tricellular junctions. However, tight junctions also adapt non-linear architectures exhibiting either a ruffled or spiked morphology, which both are responses to changes in claudin engagement of actin filaments. Other terms for ruffled tight junctions include wavy, tortuous, undulating, serpentine or zig-zag junctions. Ruffling is under the control of hypoxia induced factor (HIF) and integrin-mediated signaling, as well as direct mechanical stimulation. Tight junction ruffling is specifically enhanced by claudin-2, antagonized by claudin-1 and requires claudin binding to ZO-1. Tight junction spikes are sites of active vesicle budding and fusion that appear as perpendicular projections oriented towards the nucleus. Spikes share molecular features with focal adherens junctions and tubulobulbar complexes found in Sertoli cells. Lung epithelial cells under stress form spikes due to an increase in claudin-5 expression that directly disrupts claudin-18/ZO-1 interactions. Together this suggests that claudins are not simply passive cargoes controlled by scaffold proteins. We propose a model where claudins specifically influence tight junction scaffold proteins to control interactions with the cytoskeleton as a mechanism that regulates tight junction assembly and function.

β adrenergic receptor modulated signaling in glioma models: promoting β adrenergic receptor-β arrestin scaffold-mediated activation of extracellular-regulated kinase 1/2 may prove to be a panacea in the treatment of intracranial and spinal malignancy and extra-neuraxial carcinoma

Neoplastically transformed astrocytes express functionally active cell surface β adrenergic receptors (βARs). Treatment of glioma models in vitro and in vivo with β adrenergic agonists variably amplifies or attenuates cellular proliferation. In the majority of in vivo models, β adrenergic agonists generally reduce cellular proliferation. However, treatment with β adrenergic agonists consistently reduces tumor cell invasive potential, angiogenesis, and metastasis. β adrenergic agonists induced decreases of invasive potential are chiefly mediated through reductions in the expression of matrix metalloproteinases types 2 and 9. Treatment with β adrenergic agonists also clearly reduce tumoral neoangiogenesis, which may represent a putatively useful mechanism to adjuvantly amplify the effects of bevacizumab. Bevacizumab is a monoclonal antibody targeting the vascular endothelial growth factor receptor. We may accordingly designate βagonists to represent an enhancer of bevacizumab. The antiangiogenic effects of β adrenergic agonists may thus effectively render an otherwise borderline effective therapy to generate significant enhancement in clinical outcomes. β adrenergic agonists upregulate expression of the major histocompatibility class II DR alpha gene, effectively potentiating the immunogenicity of tumor cells to tumor surveillance mechanisms. Authors have also demonstrated crossmodal modulation of signaling events downstream from the β adrenergic cell surface receptor and microtubular polymerization and depolymerization. Complex effects and desensitization mechanisms of the β adrenergic signaling may putatively represent promising therapeutic targets. Constant stimulation of the β adrenergic receptor induces its phosphorylation by β adrenergic receptor kinase (βARK), rendering it a suitable substrate for alternate binding by β arrestins 1 or 2. The binding of a β arrestin to βARK phosphorylated βAR promotes receptor mediated internalization and downregulation of cell surface receptor and contemporaneously generates a cell surface scaffold at the βAR. The scaffold mediated activation of extracellular regulated kinase 1/2, compared with protein kinase A mediated activation, preferentially favors cytosolic retention of ERK1/2 and blunting of nuclear translocation and ensuant pro-transcriptional activity. Thus, βAR desensitization and consequent scaffold assembly effectively retains the cytosolic homeostatic functions of ERK1/2 while inhibiting its pro-proliferative effects. We suggest these mechanisms specifically will prove quite promising in developing primary and adjuvant therapies mitigating glioma growth, angiogenesis, invasive potential, and angiogenesis. We suggest generating compounds and targeted mutations of the β adrenergic receptor favoring β arrestin binding and scaffold facilitated activation of ERK1/2 may hold potential promise and therapeutic benefit in adjuvantly treating most or all cancers. We hope our discussion will generate fruitful research endeavors seeking to exploit these mechanisms.