KLF4-dependent perivascular cell plasticity mediates pre-metastatic niche formation and metastasis

Spatial architecture of the immune microenvironment orchestrates tumor immunity and therapeutic response

Tumors are not only aggregates of malignant cells but also well-organized complex ecosystems. The immunological components within tumors, termed the tumor immune microenvironment (TIME), have long been shown to be strongly related to tumor development, recurrence and metastasis. However, conventional studies that underestimate the potential value of the spatial architecture of the TIME are unable to completely elucidate its complexity. As innovative high-flux and high-dimensional technologies emerge, researchers can more feasibly and accurately detect and depict the spatial architecture of the TIME. These findings have improved our understanding of the complexity and role of the TIME in tumor biology. In this review, we first epitomized some representative emerging technologies in the study of the spatial architecture of the TIME and categorized the description methods used to characterize these structures. Then, we determined the functions of the spatial architecture of the TIME in tumor biology and the effects of the gradient of extracellular nonspecific chemicals (ENSCs) on the TIME. We also discussed the potential clinical value of our understanding of the spatial architectures of the TIME, as well as current limitations and future prospects in this novel field. This review will bring spatial architectures of the TIME, an emerging dimension of tumor ecosystem research, to the attention of more researchers and promote its application in tumor research and clinical practice.

Categorization of lung mesenchymal cells in development and fibrosis

Pulmonary mesenchymal cells are critical players in both the mouse and human during lung development and disease states. They are increasingly recognized as highly heterogeneous, but there is no consensus on subpopulations or discriminative markers for each subtype. We completed scRNA-seq analysis of mesenchymal cells from the embryonic, postnatal, adult and aged fibrotic lungs of mice and humans. We consistently identified and delineated the transcriptome of lipofibroblasts, myofibroblasts, smooth muscle cells, pericytes, mesothelial cells, and a novel population characterized by Ebf1 expression. Subtype selective transcription factors and putative divergence of the clusters during development were described. Comparative analysis revealed orthologous subpopulations with conserved transcriptomic signatures in murine and human lung mesenchymal cells. All mesenchymal subpopulations contributed to matrix gene expression in fibrosis. This analysis would enhance our understanding of mesenchymal cell heterogeneity in lung development, homeostasis and fibrotic disease conditions.

Advancing therapy for osteosarcoma

Improving the survival of patients with osteosarcoma has long proved challenging, although the treatment of this disease is on the precipice of advancement. The increasing feasibility of molecular profiling together with the creation of both robust model systems and large, well-annotated tissue banks has led to an increased understanding of osteosarcoma biology. The historical invariability of survival outcomes and the limited number of agents known to be active in the treatment of this disease facilitate clinical trials designed to identify efficacious novel therapies using small cohorts of patients. In addition, trial designs will increasingly consider the genetic background of the tumour through biomarker-based patient selection, thereby enriching for clinical activity. Indeed, osteosarcoma cells are known to express a number of surface proteins that might be of therapeutic relevance, including B7-H3, GD2 and HER2, which can be targeted using antibody-drug conjugates and/or adoptive cell therapies. In addition, immune-checkpoint inhibition might augment the latter approach by helping to overcome the immunosuppressive tumour microenvironment. In this Review, we provide a brief overview of current osteosarcoma therapy before focusing on the biological insights from the molecular profiling and preclinical modelling studies that have opened new therapeutic opportunities in this disease.

Extracellular matrix remodeling associated with bleomycin-induced lung injury supports pericyte-to-myofibroblast transition

Of the many origins of pulmonary myofibroblasts, microvascular pericytes are a known source. Prior literature has established the ability of pericytes to transition into myofibroblasts, but provide limited insight into molecular cues that drive this process during lung injury repair and fibrosis. Fibronectin and RGD-binding integrins have long been considered pro-fibrotic factors in myofibroblast biology, and here we test the hypothesis that these known myofibroblast cues coordinate pericyte-to-myofibroblast transitions. Specifically, we hypothesized that αvβ3 integrin engagement on fibronectin induces pericyte transition into myofibroblastic phenotypes in the murine bleomycin lung injury model. Myosin Heavy Chain 11 (Myh11)-CreERT2 lineage tracing in transgenic mice allows identification of cells of pericyte origin and provides a robust tool for isolating pericytes from tissues for further evaluation. We used this murine model to track and characterize pericyte behaviors during tissue repair. The majority of Myh11 lineage-positive cells are positive for the pericyte surface markers, PDGFRβ (55%) and CD146 (69%), and display typical pericyte morphology with spatial apposition to microvascular networks. After intratracheal bleomycin treatment of mice, Myh11 lineage-positive cells showed significantly increased contractile and secretory markers, as well as αv integrin expression. According to RNASeq measurements, many disease and tissue-remodeling genesets were upregulated in Myh11 lineage-positive cells in response to bleomycin-induced lung injury. In vitro, blocking αvβ3 binding through cycloRGDfK prevented expression of the myofibroblastic marker αSMA relative to controls. In response to RGD-containing provisional matrix proteins present in lung injury, pericytes may alter their integrin profile.

ITIH5, a p53-responsive gene, inhibits the growth and metastasis of melanoma cells by downregulating the transcriptional activity of KLF4

ITIH5, a member of the inter-α-trypsin inhibitory (ITI) gene family, acts as a putative tumour-suppressor gene in many cancers. However, its role and the regulatory mechanism in melanoma are still unclear. Here, we found that the expression of ITIH5 was decreased in melanoma tissues compared with normal skin tissues. Decreased expression of ITIH5 was correlated with clinicopathological features and predicted poor prognosis in patients with melanoma. Forced expression of ITIH5 significantly inhibited melanoma cell proliferation and metastasis in vitro and ex vivo while knockdown of ITIH5 expression enhanced the malignant behaviour of melanoma cells. In further mechanistic studies, we showed that p53 can directly bind to the promoter of ITIH5 and thus promotes transcription of ITIH5 in melanoma cells. Additionally, we found that ITIH5 interacted with Krüppel-like factor 4 (KLF4) and inhibited its transcriptional activity. Collectively, our data not only identified a tumour-suppressive role of ITIH5 in melanoma but also revealed that upregulation of ITIH5 by p53 suppressed melanoma cell growth and migration likely by downmodulating the transcriptional activity of KLF4.

A single-cell atlas of human teeth

Teeth exert fundamental functions related to mastication and speech. Despite their great biomedical importance, an overall picture of their cellular and molecular composition is still missing. In this study, we have mapped the transcriptional landscape of the various cell populations that compose human teeth at single-cell resolution, and we analyzed in deeper detail their stem cell populations and their microenvironment. Our study identified great cellular heterogeneity in the dental pulp and the periodontium. Unexpectedly, we found that the molecular signatures of the stem cell populations were very similar, while their respective microenvironments strongly diverged. Our findings suggest that the microenvironmental specificity is a potential source for functional differences between highly similar stem cells located in the various tooth compartments and open new perspectives toward cell-based dental therapeutic approaches.

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Dental atlas of the pulp and periodontal tissues of human teeth

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Identification of three common MSC subclusters between dental pulp and periodontium

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Dental pulp and periodontal MSCs are similar, and their niches diverge

Genetically engineered myeloid cells rebalance the core immune suppression program in metastasis

Metastasis is the leading cause of cancer-related deaths, and greater knowledge of the metastatic microenvironment is necessary to effectively target this process. Microenvironmental changes occur at distant sites prior to clinically detectable metastatic disease; however, the key niche regulatory signals during metastatic progression remain poorly characterized. Here, we identify a core immune suppression gene signature in pre-metastatic niche formation that is expressed predominantly by myeloid cells. We target this immune suppression program by utilizing genetically engineered myeloid cells (GEMys) to deliver IL-12 to modulate the metastatic microenvironment. Our data demonstrate that IL12-GEMy treatment reverses immune suppression in the pre-metastatic niche by activating antigen presentation and T cell activation, resulting in reduced metastatic and primary tumor burden and improved survival of tumor-bearing mice. We demonstrate that IL12-GEMys can functionally modulate the core program of immune suppression in the pre-metastatic niche to successfully rebalance the dysregulated metastatic microenvironment in cancer.

Remodeling of Metastatic Vasculature Reduces Lung Colonization and Sensitizes Overt Metastases to Immunotherapy

Due to limited current therapies, metastases are the primary cause of mortality in cancer patients. Here, we employ a fusion compound of the cytokine LIGHT and a vascular targeting peptide (LIGHT-VTP) that homes to angiogenic blood vessels in primary tumors. We show in primary mouse lung cancer that normalization of tumor vasculature by LIGHT-VTP prevents cancer cell intravasation. Further, LIGHT-VTP efficiently targets pathological blood vessels in the pre-metastatic niche, reducing vascular hyper-permeability and extracellular matrix (ECM) deposition, thus blocking metastatic lung colonization. Moreover, we demonstrate that mouse and human metastatic melanoma deposits are targetable by VTP. In overt melanoma metastases, LIGHT-VTP normalizes intra-metastatic blood vessels and increases GrzB⁺ effector T cells. Successful treatment induces high endothelial venules (HEVs) and lymphocyte clusters, which sensitize refractory lung metastases to anti-PD-1 checkpoint inhibitors. These findings demonstrate an important application for LIGHT-VTP therapy in preventing metastatic development as well as exerting anti-tumor effects in established metastases.

Disease-Relevant Single Cell Photonic Signatures Identify S100β Stem Cells and their Myogenic Progeny in Vascular Lesions

A hallmark of subclinical atherosclerosis is the accumulation of vascular smooth muscle cell (SMC)-like cells leading to intimal thickening and lesion formation. While medial SMCs contribute to vascular lesions, the involvement of resident vascular stem cells (vSCs) remains unclear. We evaluated single cell photonics as a discriminator of cell phenotype in vitro before the presence of vSC within vascular lesions was assessed ex vivo using supervised machine learning and further validated using lineage tracing analysis. Using a novel lab-on-a-Disk(Load) platform, label-free single cell photonic emissions from normal and injured vessels ex vivo were interrogated and compared to freshly isolated aortic SMCs, cultured Movas SMCs, macrophages, B-cells, S100β⁺ mVSc, bone marrow derived mesenchymal stem cells (MSC) and their respective myogenic progeny across five broadband light wavelengths (λ465 - λ670 ± 20 nm). We found that profiles were of sufficient coverage, specificity, and quality to clearly distinguish medial SMCs from different vascular beds (carotid vs aorta), discriminate normal carotid medial SMCs from lesional SMC-like cells ex vivo following flow restriction, and identify SMC differentiation of a series of multipotent stem cells following treatment with transforming growth factor beta 1 (TGF- β1), the Notch ligand Jagged1, and Sonic Hedgehog using multivariate analysis, in part, due to photonic emissions from enhanced collagen III and elastin expression. Supervised machine learning supported genetic lineage tracing analysis of S100β⁺ vSCs and identified the presence of S100β⁺vSC-derived myogenic progeny within vascular lesions. We conclude disease-relevant photonic signatures may have predictive value for vascular disease.

Mural Cells: Potential Therapeutic Targets to Bridge Cardiovascular Disease and Neurodegeneration

Mural cells collectively refer to the smooth muscle cells and pericytes of the vasculature. This heterogenous population of cells play a crucial role in the regulation of blood pressure, distribution, and the structural integrity of the vascular wall. As such, dysfunction of mural cells can lead to the pathogenesis and progression of a number of diseases pertaining to the vascular system. Cardiovascular diseases, particularly atherosclerosis, are perhaps the most well-described mural cell-centric case. For instance, atherosclerotic plaques are most often described as being composed of a proliferative smooth muscle cap accompanied by a necrotic core. More recently, the role of dysfunctional mural cells in neurodegenerative diseases, such as Alzheimer’s and Parkinson’s disease, is being recognized. In this review, we begin with an exploration of the mechanisms underlying atherosclerosis and neurodegenerative diseases, such as mural cell plasticity. Next, we highlight a selection of signaling pathways (PDGF, Notch and inflammatory signaling) that are conserved across both diseases. We propose that conserved mural cell signaling mechanisms can be exploited for the identification or development of dual-pronged therapeutics that impart both cardio- and neuroprotective qualities.

The calcium binding protein S100β marks hedgehog-responsive resident vascular stem cells within vascular lesions

A hallmark of subclinical atherosclerosis is the accumulation of vascular smooth muscle cell (SMC)-like cells leading to intimal thickening. While medial SMCs contribute, the participation of hedgehog-responsive resident vascular stem cells (vSCs) to lesion formation remains unclear. Using transgenic eGFP mice and genetic lineage tracing of S100β vSCs in vivo, we identified S100β/Sca1 cells derived from a S100β non-SMC parent population within lesions that co-localise with smooth muscle α-actin (SMA) cells following iatrogenic flow restriction, an effect attenuated following hedgehog inhibition with the smoothened inhibitor, cyclopamine. In vitro, S100β/Sca1 cells isolated from atheroprone regions of the mouse aorta expressed hedgehog signalling components, acquired the di-methylation of histone 3 lysine 4 (H3K4me2) stable SMC epigenetic mark at the Myh11 locus and underwent myogenic differentiation in response to recombinant sonic hedgehog (SHh). Both S100β and PTCH1 cells were present in human vessels while S100β cells were enriched in arteriosclerotic lesions. Recombinant SHh promoted myogenic differentiation of human induced pluripotent stem cell-derived S100β neuroectoderm progenitors in vitro. We conclude that hedgehog-responsive S100β vSCs contribute to lesion formation and support targeting hedgehog signalling to treat subclinical arteriosclerosis.

Modulation of the Vascular-Immune Environment in Metastatic Cancer

Advanced metastatic cancer is rarely curable. While immunotherapy has changed the oncological landscape profoundly, cure in metastatic disease remains the exception. Tumor blood vessels are crucial regulators of tumor perfusion, immune cell influx and metastatic dissemination. Indeed, vascular hyperpermeability is a key feature of primary tumors, the pre-metastatic niche in host tissue and overt metastases at secondary sites. Combining anti-angiogenesis and immune therapies may therefore unlock synergistic effects by inducing a stabilized vascular network permissive for effector T cell trafficking and function. However, anti-angiogenesis therapies, as currently applied, are hampered by intrinsic or adaptive resistance mechanisms at primary and distant tumor sites. In particular, heterogeneous vascular and immune environments which can arise in metastatic lesions of the same individual pose significant challenges for currently approved drugs. Thus, more consideration needs to be given to tailoring new combinations of vascular and immunotherapies, including dosage and timing regimens to specific disease microenvironments.

TWIST1 induces phenotypic switching of vascular smooth muscle cells by downregulating p68 and microRNA-143/145

TWIST1 is an important basic helix‐loop‐helix protein linked to multiple physiological and pathological processes. Although TWIST1 is believed to be involved in vascular pathogenesis, its effects on homeostasis of smooth muscle cells (SMCs) remain poorly understood. Here, we show that TWIST1 protein levels were significantly elevated during SMC phenotypic switching in vivo and in vitro. TWIST1 overexpression promoted phenotypic switching of SMCs, while siRNA targeting of TWIST1 prevented cell transition. Mechanistically, TWIST1 decreased the level of microRNA‐143/145, which governs smooth muscle marker gene transcription. In addition, TWIST1 repressed p68 mRNA and protein expression, a crucial modulator of SMC behavior and microRNA biogenesis. Our co‐immunoprecipitation assay demonstrated a previously unrecognized molecular interaction between TWIST1 and p68 protein. Finally, we found that TWIST1 triggered SMC phenotypic switching and suppressed microRNA‐143/145 expression by promoting the proteasomal degradation of p68. These data suggest a novel role of TWIST1 in the regulation of SMC homeostasis by modulating p68/microRNA‐143/145 axis.

New insights in the expression of stromal caveolin 1 in breast cancer spread to axillary lymph nodes

Recent evidence suggests that a loss of expression of caveolin in the stromal compartment (sCav-1) of human invasive breast carcinoma (IBC) may be a predictor of disease recurrence, metastasis and poor outcome. At present, there is little knowledge regarding the expression of sCav-1 at the metastatic sites. We therefore studied sCav-1 expression in IBCs and in their axillary lymph nodes to seek a correlation with cancer metastasis. 189 consecutive invasive IBCs (53 with axillary lymph node metastases and 136 without) were studied by immunohistochemistry, using a rabbit polyclonal anti-Cav-1 antibody. In IBCs sCav-1 was evaluated in fibroblasts scattered in the tumor stroma whereas in lymph nodes sCav-1 was assessed in fibroblast-like stromal cells. For the first time, we observed a statistically significant progressive loss of sCav-1 from normal/reactive axillary lymph nodes of tumors limited to the breast to metastatic axillary lymph nodes, through normal/reactive axillary lymph nodes of tumors with axillary metastatic spread. These data indicate that Cav-1 expressed by the stromal compartment of lymph nodes, somehow, may possibly contribute to metastatic spread in IBC.

Characteristics of pre-metastatic niche: the landscape of molecular and cellular pathways

Metastasis is a major contributor to cancer-associated deaths. It involves complex interactions between primary tumorigenic sites and future metastatic sites. Accumulation studies have revealed that tumour metastasis is not a disorderly spontaneous incident but the climax of a series of sequential and dynamic events including the development of a pre-metastatic niche (PMN) suitable for a subpopulation of tumour cells to colonize and develop into metastases. A deep understanding of the formation, characteristics and function of the PMN is required for developing new therapeutic strategies to treat tumour patients. It is rapidly becoming evident that therapies targeting PMN may be successful in averting tumour metastasis at an early stage. This review highlights the key components and main characteristics of the PMN and describes potential therapeutic strategies, providing a promising foundation for future studies.

Pericytes contribute to the islet basement membranes to promote beta-cell gene expression

β-Cells depend on the islet basement membrane (BM). While some islet BM components are produced by endothelial cells (ECs), the source of others remains unknown. Pancreatic pericytes directly support β-cells through mostly unidentified secreted factors. Thus, we hypothesized that pericytes regulate β-cells through the production of BM components. Here, we show that pericytes produce multiple components of the mouse pancreatic and islet interstitial and BM matrices. Several of the pericyte-produced ECM components were previously implicated in β-cell physiology, including collagen IV, laminins, proteoglycans, fibronectin, nidogen, and hyaluronan. Compared to ECs, pancreatic pericytes produce significantly higher levels of α2 and α4 laminin chains, which constitute the peri-islet and vascular BM. We further found that the pericytic laminin isoforms differentially regulate mouse β-cells. Whereas α2 laminins promoted islet cell clustering, they did not affect gene expression. In contrast, culturing on Laminin-421 induced the expression of β-cell genes, including Ins1, MafA, and Glut2, and significantly improved glucose-stimulated insulin secretion. Thus, alongside ECs, pericytes are a significant source of the islet BM, which is essential for proper β-cell function.

Emerging paradigms in metastasis research

Historically, therapy of metastatic disease has essentially been limited to using strategies that were identified and established to shrink primary tumors. The limited efficacy of such treatments on overall patient survival stems from diverging intrinsic and extrinsic characteristics of a primary tumor and metastases originating therefrom. To develop better therapeutic strategies to treat metastatic disease, there is an urgent need to shift the paradigm in preclinical metastasis research by conceptualizing metastatic dissemination, colonization, and growth as spatiotemporally dynamic processes and identifying rate-limiting vulnerabilities of the metastatic cascade. Clinically, while metastatic colonization remains the most attractive therapeutic avenue, comprehensive understanding of earlier steps may unravel novel metastasis-restricting therapies for presurgical neoadjuvant application. Moving beyond a primary tumor-centric view, this review adopts a holistic approach to understanding the spatial and temporal progression of metastasis. After reviewing recent developments in metastasis research, we highlight some of the grand challenges and propose a framework to expedite mechanism-based discovery research feeding the translational pipeline.

Human ALS/FTD brain organoid slice cultures display distinct early astrocyte and targetable neuronal pathology

Amyotrophic lateral sclerosis overlapping with frontotemporal dementia (ALS/FTD) is a fatal and currently untreatable disease characterized by rapid cognitive decline and paralysis. Elucidating initial cellular pathologies is central to therapeutic target development, but obtaining samples from presymptomatic patients is not feasible. Here, we report the development of a cerebral organoid slice model derived from human induced pluripotent stem cells (iPSCs) that recapitulates mature cortical architecture and displays early molecular pathology of C9ORF72 ALS/FTD. Using a combination of single-cell RNA sequencing and biological assays, we reveal distinct transcriptional, proteostasis and DNA repair disturbances in astroglia and neurons. We show that astroglia display increased levels of the autophagy signaling protein P62 and that deep layer neurons accumulate dipeptide repeat protein poly(GA), DNA damage and undergo nuclear pyknosis that could be pharmacologically rescued by GSK2606414. Thus, patient-specific iPSC-derived cortical organoid slice cultures are a reproducible translational platform to investigate preclinical ALS/FTD mechanisms as well as novel therapeutic approaches.

KLF4 (Kruppel-Like Factor 4)-Dependent Perivascular Plasticity Contributes to Adipose Tissue inflammation

OBJECTIVE

Smooth muscle cells and pericytes display remarkable plasticity during injury and disease progression. Here, we tested the hypothesis that perivascular cells give rise to Klf4-dependent macrophage-like cells that augment adipose tissue (AT) inflammation and metabolic dysfunction associated with diet-induced obesity (DIO). Approach and Results: Using Myh11-CreERT2 eYFP (enhanced yellow fluorescent protein) mice and flow cytometry of the stromovascular fraction of epididymal AT, we observed a large fraction of smooth muscle cells and pericytes lineage traced eYFP+ cells expressing macrophage markers. Subsequent single-cell RNA sequencing, however, showed that the majority of these cells had no detectable eYFP transcript. Further exploration revealed that intraperitoneal injection of tamoxifen in peanut oil, used for generating conditional knockout or reporter mice in thousands of previous studies, resulted in large increase in the autofluorescence and false identification of macrophages within epididymal AT as being eYFP+; and unintended proinflammatory consequences. Using newly generated Myh11-DreERT2tdTomato mice given oral tamoxifen, we virtually eliminated the problem with autofluorescence and identified 8 perivascular cell dominated clusters, half of which were altered upon DIO. Given that perivascular cell KLF4 (kruppel-like factor 4) can have beneficial or detrimental effects, we tested its role in obesity-associated AT inflammation. While smooth muscle cells and pericytes-specific Klf4 knockout (smooth muscle cells and pericytes Klf4Δ/Δ) mice were not protected from DIO, they displayed improved glucose tolerance upon DIO, and showed marked decreases in proinflammatory macrophages and increases in LYVE1+ lymphatic endothelial cells in the epididymal AT.

CONCLUSIONS

Perivascular cells within the AT microvasculature dynamically respond to DIO and modulate tissue inflammation and metabolism in a KLF4-dependent manner.

The Tumour Microenvironment and Circulating Tumour Cells: A Partnership Driving Metastasis and Glycan-Based Opportunities for Cancer Control

Circulating tumour cells (CTC) are rare cells that actively detach or are shed from primary tumours into the lymph and blood. Some CTC subpopulations gain the capacity to survive, home and colonize distant locations, forming metastasis. This results from a multifactorial process in which cancer cells optimize motility, invasion, immune escape and cooperative relationships with microenvironmental cues. Here we present evidences of a self-fuelling molecular crosstalk between cancer cells and the tumour stroma supporting the main milestones leading to metastasis. We discuss how the tumour microenvironment supports pre-metastatic niches and CTC development and ultimately dictates CTC fate in targeted organs. Finally, we highlight the key role played by protein glycosylation in metastasis development, its prompt response to microenvironmental stimuli and the tremendous potential of glycan-based molecular signatures for liquid biopsies and targeted therapeutics.

TRPV5 attenuates abdominal aortic aneurysm in mice by regulating KLF4-dependent phenotype switch of aortic vascular smooth muscle cells

Abdominal aortic aneurysm (AAA) is a fatal vascular disease with insidious symptoms. However, the mechanism behind its development remains unclear. The transient receptor potential vanilloid (TRPV) family has crucial protective effects against cardiovascular diseases, but the role of TRPV5 in AAA has yet to be reported. In this study, ApoE^-/- mice were intraperitoneally injected with AAV-GFP or AAV-TRPV5. After 30 days, mice were further administered with angiotensin II (Ang II, 1.44 mg/kg/day) by using osmotic pumps to induce the AAA model or Saline for 28 days, (i.e., Saline + AAV-GFP, Saline + AAV-TRPV5, Ang II + AAV-GFP and Ang II + AAV-TRPV5 groups were established). Compared with the control group, the incidence of AAA and the maximal diameter of the abdominal aorta markedly decreased in Ang II + AAV-TRPV5, which was detected by vascular ultrasound at 28 day. Meanwhile, less collagen and elastin degradation were observed in the Ang II + AAV-TRPV5 group by using Masson and Elastin stains. Moreover, more α-SMA and less MMP2 was observed in the abdominal aortas collected at 28 day by immunohistochemistry. In vitro, primary mouse vascular smooth muscle cells (VSMCs) were treated with Ang II (1 μM) to induce phenotype switch. Sh-TRPV5 and AdTRPV5 were used to transfect VSMCs. PCR and Western blotting were used to access the expression of contractile marker, including α-SMA and SM-22α. The results showed that the mRNA and protein level of α-SMA and SM-22α were decreased under the stimulation of Ang II, but could be attenuated by TRPV5 overexpression. The cell scratch assay demonstrated that the migration ability of VSMCs was increased in Ang II treated group and could be ameliorated by TRPV5 overexpression. Above all, VSMCs transformed from the contractile into secretory phenotype under Ang II stimuli, but could be rescued by TRPV5 overexpression. Furthermore, TRPV5 overexpression suppressed the increased expression of KLF4 induced by Ang II treatment in VSMCs. The data demonstrated that TRPV5 could inhibit AAA formation and play a critical role in the VSMC phenotype switch by downregulating KLF4, suggesting TRPV5 as a new strategy for treating AAA.

Smooth muscle-derived progenitor cell myofibroblast differentiation through KLF4 downregulation promotes arterial remodeling and fibrosis

Resident vascular adventitial SCA1⁺ progenitor (AdvSca1) cells are essential in vascular development and injury. However, the heterogeneity of AdvSca1 cells presents a unique challenge in understanding signaling pathways orchestrating their behavior in homeostasis and injury responses. Using smooth muscle cell (SMC) lineage-tracing models, we identified a subpopulation of AdvSca1 cells (AdvSca1-SM) originating from mature SMCs that undergo reprogramming in situ and exhibit a multipotent phenotype. Here we employed lineage tracing and RNA-sequencing to define the signaling pathways regulating SMC-to-AdvSca1-SM cell reprogramming and AdvSca1-SM progenitor cell phenotype. Unbiased hierarchical clustering revealed that genes related to hedgehog/WNT/beta-catenin signaling were significantly enriched in AdvSca1-SM cells, emphasizing the importance of this signaling axis in the reprogramming event. Leveraging AdvSca1-SM–specific expression of GLI-Kruppel family member GLI1 (Gli1), we generated Gli1-CreER^T2-ROSA26-YFP reporter mice to selectively track AdvSca1-SM cells. We demonstrated that physiologically relevant vascular injury or AdvSca1-SM cell–specific Kruppel-like factor 4 (Klf4) depletion facilitated the proliferation and differentiation of AdvSca1-SM cells to a profibrotic myofibroblast phenotype rather than macrophages. Surprisingly, AdvSca1-SM cells selectively contributed to adventitial remodeling and fibrosis but little to neointima formation. Together, these findings strongly support therapeutics aimed at preserving the AdvSca1-SM cell phenotype as a viable antifibrotic approach.

Smooth muscle cell–derived resident vascular adventitial progenitor cells adopt a myofibroblast phenotype in response to vascular injury and play a dominant role in vascular fibrosis.

Pericyte in Oral Squamous Cell Carcinoma: A Systematic Review

The microenvironment of oral cancer is highly dynamic and has been proved to affect tumor progression. Pericytes are blood vessels surrounding cells that have recently gained attention for their roles in vascular and cancer biology. The objective of the present study was to survey the scientific literature for conclusive evidence about whether pericytes are part of blood vessels in oral squamous cell carcinoma (OSCC) and their roles in the tumor microenvironment and clinical outcomes. A systematic electronic search was undertaken in Medline Ovid, PubMed, Web of Science, and Scopus. Eligibility criteria were: publications adopting in vivo models of OSCC that included pericyte detection and assessment by pericyte markers (e.g., α-smooth muscle actin, neuron-glial antigen 2 and platelet-derived growth factor receptor-β). The search yielded seven eligible studies (from 2008 to 2018). The markers most commonly used for pericyte detection were α-smooth muscle actin and neuron-glial antigen 2. The studies reviewed showed the presence of immature vessels exhibiting a reduction of pericyte coverage in OSCC and indicated that anti-cancer therapies could contribute to vessel normalization and pericyte regain. The pericyte population is significantly affected during OSCC development and cancer therapy. While these findings might suggest a role for pericytes in OSCC progression, the limited data available do not allow us to conclude whether they modify the tumor microenvironment and clinical outcome.

The CXCL12-CXCR4 Signaling Axis Plays a Key Role in Cancer Metastasis and is a Potential Target for Developing Novel Therapeutics against Metastatic Cancer

Metastasis is the main cause of death in cancer patients; there is currently no effective treatment for cancer metastasis. This is primarily due to our insufficient understanding of the metastatic mechanisms in cancer. An increasing number of studies have shown that the C-X-C motif chemokine Ligand 12 (CXCL12) is overexpressed in various tissues and organs. It is a key niche factor that nurtures the pre-metastatic niches (tumorigenic soil) and recruits tumor cells (oncogenic "seeds") to these niches, thereby fostering cancer cell aggression and metastatic capabilities. However, the C-X-C motif chemokine Receptor 4 (CXCR4) is aberrantly overexpressed in various cancer stem/progenitor cells and functions as a CXCL12 receptor. CXCL12 activates CXCR4 as well as multiple downstream multiple tumorigenic signaling pathways, promoting the expression of various oncogenes. Activation of the CXCL12-CXCR4 signaling axis promotes Epithelial-Mesenchymal Transition (EMT) and mobilization of cancer stem/progenitor cells to pre-metastatic niches. It also nurtures cancer cells with high motility, invasion, and dissemination phenotypes, thereby escalating multiple proximal or distal cancer metastasis; this results in poor patient prognosis. Based on this evidence, recent studies have explored either CXCL12- or CXCR4-targeted anti-cancer therapeutics and have achieved promising results in the preclinical trials. Further exploration of this new strategy and its potent therapeutics effect against metastatic cancer through the targeting of the CXCL12- CXCR4 signaling axis may lead to a novel therapy that can clean up the tumor microenvironment ("soil") and kill the cancer cells, particularly the cancer stem/progenitor cells ("seeds"), in cancer patients. Ultimately, this approach has the potential to effectively treat metastatic cancer.

Recent Discoveries on the Involvement of Krüppel-Like Factor 4 in the Most Common Cancer Types

Krüppel-like factor 4 (KLF4) is a transcription factor highly conserved in evolution. It is particularly well known for its role in inducing pluripotent stem cells. In addition, KLF4 plays many roles in cancer. The results of most studies suggest that KLF4 is a tumor suppressor. However, the functioning of KLF4 is regulated at many levels. These include regulation of transcription, alternative splicing, miRNA, post-translational modifications, subcellular localization, protein stability and interactions with other molecules. Simple experiments aimed at assaying transcript levels or protein levels fail to address this complexity and thus may deliver misleading results. Tumor subtypes are also important; for example, in prostate cancer KLF4 is highly expressed in indolent tumors where it impedes tumor progression, while it is absent from aggressive prostate tumors. KLF4 is important in regulating response to many known drugs, and it also plays a role in tumor microenvironment. More and more information is available about upstream regulators, downstream targets and signaling pathways associated with the involvement of KLF4 in cancer. Furthermore, KLF4 performs critical function in the overall regulation of tissue homeostasis, cellular integrity, and progression towards malignancy. Here we summarize and analyze the latest findings concerning this fascinating transcription factor.

Premetastasis

Sterile inflammation within primary tumor tissues can spread to distant organs that are devoid of tumor cells. This happens in a manner dependent on tumor-led secretome, before the actual metastasis occurs. The premetastatic microenvironment is established in this way and is at least partly regulated by hijacking the host innate immune system. The biological manifestation of premetastasis include increased vascular permeability, cell mobilization via the blood stream, degradation of the extracellular matrix, immunosuppression, and host antineoplastic activities.

Jagged1-Notch1-deployed tumor perivascular niche promotes breast cancer stem cell phenotype through Zeb1

Zinc finger E-box binding homeobox 1 (Zeb1) has been demonstrated to participate in the acquisition of the properties of cancer stem cells (CSCs). However, it is largely unknown how signals from the tumor microenvironment (TME) contribute to aberrant Zeb1 expression. Here, we show that Zeb1 depletion suppresses stemness, colonization and the phenotypic plasticity of breast cancer. Moreover, we demonstrate that, with direct cell-cell contact, TME-derived endothelial cells provide the Notch ligand Jagged1 (Jag1) to neighboring breast CSCs, leading to Notch1-dependent upregulation of Zeb1. In turn, ectopic Zeb1 in tumor cells increases VEGFA production and reciprocally induces endothelial Jag1 in a paracrine manner. Depletion of Zeb1 disrupts this positive feedback loop in the tumor perivascular niche, which eventually lessens tumor initiation and progression in vivo and in vitro. In this work, we highlight that targeting the angiocrine Jag1-Notch1-Zeb1-VEGFA loop decreases breast cancer aggressiveness and thus enhances the efficacy of antiangiogenic therapy.

TGF-β-induced IGFBP-3 is a key paracrine factor from activated pericytes that promotes colorectal cancer cell migration and invasion

The crosstalk between cancer cells and the tumor microenvironment has been implicated in cancer progression and metastasis. Fibroblasts and immune cells are widely known to be attracted to and modified by cancer cells. However, the role of pericytes in the tumor microenvironment beyond endothelium stabilization is poorly understood. Here, we report that pericytes promoted colorectal cancer (CRC) cell proliferation, migration, invasion, stemness, and chemoresistance in vitro, as well as tumor growth in a xenograft CRC model. We demonstrate that coculture with human CRC cells induced broad transcriptomic changes in pericytes, mostly associated with TGF-β receptor activation. The prognostic value of a TGF-β response signature in pericytes was analyzed in CRC patient data sets. This signature was found to be a good predictor of CRC relapse. Moreover, in response to stimulation by CRC cells, pericytes expressed high levels of TGF-β1, initiating an autocrine activation loop. Investigation of secreted mediators and underlying molecular mechanisms revealed that IGFBP-3 is a key paracrine factor from activated pericytes affecting CRC cell migration and invasion. In summary, we demonstrate that the interplay between pericytes and CRC cells triggers a vicious cycle that stimulates pericyte cytokine secretion, in turn increasing CRC cell tumorigenic properties. Overall, we provide another example of how cancer cells can manipulate the tumor microenvironment.

Hypoxia in bone metastasis and osteolysis

Hypoxia is a common feature in tumors, driving pathways that promote epithelial-to-mesenchymal transition, invasion, and metastasis. Clinically, high levels of hypoxia-inducible factor (HIF) expression and stabilization at the primary site in many cancer types is associated with poor patient outcomes. Experimental evidence suggests that HIF signaling in the primary tumor promotes their dissemination to the bone, as well as the release of factors such as LOX that act distantly on the bone to stimulate osteolysis and form a pre-metastatic niche. Additionally, the bone itself is a generally hypoxic organ, fueling the activation of HIF signaling in bone resident cells, promoting tumor cell homing to the bone as well as osteoclastogenesis. The hypoxic microenvironment of the bone also stimulates the vicious cycle of tumor-induced bone destruction, further fueling tumor cell growth and osteolysis. Furthermore, hypoxia appears to regulate key tumor dormancy factors. Thus, hypoxia acts both on the tumor cells as well as the metastatic site to promote tumor cell metastasis.

Rethinking carcinogenesis: The detached pericyte hypothesis

The limiting step in cancer prevention is a lack of understanding of cancer biology. This limitation is exacerbated by a focus on the dominant somatic mutation theory (that driver mutations cause cancer) with little consideration of alternative theories of carcinogenesis. The recently proposed detached pericyte hypothesis explains many puzzling phenomena in cancer biology for which the somatic mutation theory offers no obvious explanation. These puzzling phenomena include foreign-body tumorigenesis, the link between denervation and cancer, tumors in transgenic mice that lack the inducing mutation, and non-genotoxic carcinogens. The detached pericyte hypothesis postulates that (1) a carcinogen or chronic inflammation causes pericytes to detach from blood cell walls, (2) some detached pericytes develop into myofibroblasts which alter the extracellular matrix (3) some detached pericytes develop into mesenchymal stem cells, (4) some of the mesenchymal stem cells adhere to the altered extracellular matrix (5) the altered extracellular matrix disrupts regulatory controls, causing the adjacent mesenchymal stem cells to develop into tumors. Results from experimental studies support the detached pericyte hypothesis. If the detached pericyte hypothesis is correct, pericytes should play a key role in metastasis - a testable prediction. Recent experimental results confirm this prediction and motivate a proposed experiment to partially test the detached pericyte hypothesis. If the detached pericyte hypothesis is correct, it could lead to new strategies for cancer prevention.

Pericyte-secreted IGF2 promotes breast cancer brain metastasis formation

Brain metastases are life-threatening complications of triple-negative breast cancer, melanoma, and a few other tumor types. Poor outcome of cerebral secondary tumors largely depends on the microenvironment formed by cells of the neurovascular unit, among which pericytes are the least characterized. By using in vivo and in vitro techniques and human samples, here we show that pericytes play crucial role in the development of metastatic brain tumors by directly influencing key steps of the development of the disease. Brain pericytes had a prompt chemoattractant effect on breast cancer cells and established direct contacts with them. By secreting high amounts of extracellular matrix proteins, pericytes enhanced adhesion of both melanoma and triple-negative cancer cells, which might be particularly important in the exclusive perivascular growth of these tumor cells. In addition, pericytes secreted insulin-like growth factor 2 (IGF2), which had a very significant pro-proliferative effect on mammary carcinoma, but not on melanoma cells. By inhibiting IGF2 signaling using silencing or picropodophyllin (PPP), we could block the proliferation-increasing effect of pericytes on breast cancer cells. Administration of PPP (a blood-brain barrier-permeable substance) significantly decreased the size of brain tumors in mice inoculated with triple-negative breast cancer cells. Taken together, our results indicate that brain pericytes have significant pro-metastatic features, especially in breast cancer. Our study underlines the importance of targeting pericytes and the IGF axis as potential strategies in brain metastatic diseases.

Activation of p38α stress-activated protein kinase drives the formation of the pre-metastatic niche in the lungs

Primary tumor-derived factors (TDFs) act upon normal cells to generate a pre-metastatic niche, which promotes colonization of target organs by disseminated malignant cells. Here we report that TDFs-induced activation of the p38α kinase in lung fibroblasts plays a critical role in the formation of a pre-metastatic niche in the lungs and subsequent pulmonary metastases. Activation of p38α led to inactivation of type I interferon signaling and stimulation of expression of fibroblast activation protein (FAP). FAP played a key role in remodeling of the extracellular matrix as well as inducing the expression of chemokines that enable lung infiltration by neutrophils. Increased activity of p38 in normal cells was associated with metastatic disease and poor prognosis in human melanoma patients whereas inactivation of p38 suppressed lung metastases. We discuss the p38α-driven mechanisms stimulating the metastatic processes and potential use of p38 inhibitors in adjuvant therapy of metastatic cancers.

A Novel Function for KLF4 in Modulating the De-differentiation of EpCAM-/CD133- nonStem Cells into EpCAM+/CD133+ Liver Cancer Stem Cells in HCC Cell Line HuH7

The complex and heterogeneous nature of hepatocellular carcinoma (HCC) hampers the identification of effective therapeutic strategies. Cancer stem cells (CSCs) represent a fraction of cells within tumors with the ability to self-renew and differentiate, and thus significantly contribute to the formation and maintenance of heterogeneous tumor mass. Increasing evidence indicates high plasticity in tumor cells, suggesting that non-CSCs could acquire stem cell properties through de-differentiation or reprogramming processes. In this paper, we reveal KLF4 as a transcription factor that can induce a CSC-like phenotype in non-CSCs through upregulating the EpCAM and E-CAD expression. Our studies indicated that KLF4 could directly bind to the promoter of EpCAM and increase the number of EpCAM⁺/CD133⁺ liver cancer stem cells (LCSCs) in the HuH7 HCC cell line. When KLF4 was overexpressed in EpCAM⁻/CD133⁻ non-stem cells, the expressions of hepatic stem/progenitor cell genes such as CK19, EpCAM and LGR5 were significantly increased. KLF4 overexpressing non-stem cells exhibited greater cell viability upon sorafenib treatment, while the cell migration and invasion capabilities of these cells were suppressed. Importantly, we detected an increased membranous expression and colocalization of β-CAT, E-CAD and EpCAM in the KLF4-overexpressing EpCAM⁻/CD133⁻ non-stem cells, suggesting that this complex might be required for the cancer stem cell phenotype. Moreover, our in vivo xenograft studies demonstrated that with a KLF4 overexpression, EpCAM⁻/CD133⁻ non-stem cells attained an in vivo tumor forming ability comparable to EpCAM⁺/CD133⁺ LCSCs, and the tumor specimens from KLF4-overexpressing xenografts had increased levels of both the KLF4 and EpCAM proteins. Additionally, we identified a correlation between the KLF4 and EpCAM protein expressions in human HCC tissues independent of the tumor stage and differentiation status. Collectively, our data suggest a novel function for KLF4 in modulating the de-differentiation of tumor cells and the induction of EpCAM⁺/CD133⁺ LCSCs in HuH7 HCC cells.

Tumor microenvironment complexity and therapeutic implications at a glance

The dynamic interactions of cancer cells with their microenvironment consisting of stromal cells (cellular part) and extracellular matrix (ECM) components (non-cellular) is essential to stimulate the heterogeneity of cancer cell, clonal evolution and to increase the multidrug resistance ending in cancer cell progression and metastasis. The reciprocal cell-cell/ECM interaction and tumor cell hijacking of non-malignant cells force stromal cells to lose their function and acquire new phenotypes that promote development and invasion of tumor cells. Understanding the underlying cellular and molecular mechanisms governing these interactions can be used as a novel strategy to indirectly disrupt cancer cell interplay and contribute to the development of efficient and safe therapeutic strategies to fight cancer. Furthermore, the tumor-derived circulating materials can also be used as cancer diagnostic tools to precisely predict and monitor the outcome of therapy. This review evaluates such potentials in various advanced cancer models, with a focus on 3D systems as well as lab-on-chip devices. Video abstract.

Plasticity of Cancer Stem Cell: Origin and Role in Disease Progression and Therapy Resistance

In embryonic development and throughout life, there are some cells can exhibit phenotypic plasticity. Phenotypic plasticity is the ability of cells to differentiate into multiple lineages. In normal development, plasticity is highly regulated whereas cancer cells re-activate this dynamic ability for their own progression. The re-activation of these mechanisms enables cancer cells to acquire a cancer stem cell (CSC) phenotype- a subpopulation of cells with increased ability to survive in a hostile environment and resist therapeutic insults. There are several contributors fuel CSC plasticity in different stages of disease progression such as a complex network of tumour stroma, epidermal microenvironment and different sub-compartments within tumour. These factors play a key role in the transformation of tumour cells from a stable condition to a progressive state. In addition, flexibility in the metabolic state of CSCs helps in disease progression. Moreover, epigenetic changes such as chromatin, DNA methylation could stimulate the phenotypic change of CSCs. Development of resistance to therapy due to highly plastic behaviour of CSCs is a major cause of treatment failure in cancers. However, recent studies explored that plasticity can also expose the weaknesses in CSCs, thereby could be utilized for future therapeutic development. Therefore, in this review, we discuss how cancer cells acquire the plasticity, especially the role of the normal developmental process, tumour microenvironment, and epigenetic changes in the development of plasticity. We further highlight the therapeutic resistance property of CSCs attributed by plasticity. Also, outline some potential therapeutic options against plasticity of CSCs. Graphical Abstract .

Primary tumors release ITGBL1-rich extracellular vesicles to promote distal metastatic tumor growth through fibroblast-niche formation

Tumor metastasis is a hallmark of cancer. Metastatic cancer cells often reside in distal tissues and organs in their dormant state. Mechanisms underlying the pre-metastatic niche formation are poorly understood. Here we show that in a colorectal cancer (CRC) model, primary tumors release integrin beta-like 1 (ITGBL1)-rich extracellular vesicles (EVs) to the circulation to activate resident fibroblasts in remote organs. The activated fibroblasts induce the pre-metastatic niche formation and promote metastatic cancer growth by secreting pro-inflammatory cytokine, such as IL-6 and IL-8. Mechanistically, the primary CRC-derived ITGBL1-enriched EVs stimulate the TNFAIP3-mediated NF-κB signaling pathway to activate fibroblasts. Consequently, the activated fibroblasts produce high levels of pro-inflammatory cytokines to promote metastatic cancer growth. These findings uncover a tumor-stromal interaction in the metastatic tumor microenvironment and an intimate signaling communication between primary tumors and metastases through the ITGBL1-loaded EVs. Targeting the EVs-ITGBL1-CAFs-TNFAIP3-NF-κB signaling axis provides an attractive approach for treating metastatic diseases.

Cellular signaling in Abdominal Aortic Aneurysm

Abdominal aortic aneurysms (AAAs) are highly lethal cardiovascular diseases without effective medications. However, the molecular and signaling mechanisms remain unclear. A series of pathological cellular processes have been shown to contribute to AAA formation, including vascular extracellular matrix remodeling, inflammatory and immune responses, oxidative stress, and dysfunction of vascular smooth muscle cells. Each cellular process involves complex cellular signaling, such as NF-κB, MAPK, TGFβ, Notch and inflammasome signaling. In this review, we discuss how cellular signaling networks function in various cellular processes during the pathogenesis and progression of AAA. Understanding the interaction of cellular signaling networks with AAA pathogenesis as well as the crosstalk of different signaling pathways is essential for the development of novel therapeutic approaches to and personalized treatments of AAA diseases.

Understanding and Modeling Metastasis Biology to Improve Therapeutic Strategies for Combating Osteosarcoma Progression

Osteosarcoma is a malignant primary tumor of bone, arising from transformed progenitor cells with osteoblastic differentiation and osteoid production. While categorized as a rare tumor, most patients diagnosed with osteosarcoma are adolescents in their second decade of life and underscores the potential for life changing consequences in this vulnerable population. In the setting of localized disease, conventional treatment for osteosarcoma affords a cure rate approaching 70%; however, survival for patients suffering from metastatic disease remain disappointing with only 20% of individuals being alive past 5 years post-diagnosis. In patients with incurable disease, pulmonary metastases remain the leading cause for osteosarcoma-associated mortality; yet identifying new strategies for combating metastatic progression remains at a scientific and clinical impasse, with no significant advancements for the past four decades. While there is resonating clinical urgency for newer and more effective treatment options for managing osteosarcoma metastases, the discovery of druggable targets and development of innovative therapies for inhibiting metastatic progression will require a deeper and more detailed understanding of osteosarcoma metastasis biology. Toward the goal of illuminating the processes involved in cancer metastasis, a convergent science approach inclusive of diverse disciplines spanning the biology and physical science domains can offer novel and synergistic perspectives, inventive, and sophisticated model systems, and disruptive experimental approaches that can accelerate the discovery and characterization of key processes operative during metastatic progression. Through the lens of trans-disciplinary research, the field of comparative oncology is uniquely positioned to advance new discoveries in metastasis biology toward impactful clinical translation through the inclusion of pet dogs diagnosed with metastatic osteosarcoma. Given the spontaneous course of osteosarcoma development in the context of real-time tumor microenvironmental cues and immune mechanisms, pet dogs are distinctively valuable in translational modeling given their faithful recapitulation of metastatic disease progression as occurs in humans. Pet dogs can be leveraged for the exploration of novel therapies that exploit tumor cell vulnerabilities, perturb local microenvironmental cues, and amplify immunologic recognition. In this capacity, pet dogs can serve as valuable corroborative models for realizing the science and best clinical practices necessary for understanding and combating osteosarcoma metastases.

Cancer-associated fibroblast heterogeneity in axillary lymph nodes drives metastases in breast cancer through complementary mechanisms

Although fibroblast heterogeneity is recognized in primary tumors, both its characterization in and its impact on metastases remain unknown. Here, combining flow cytometry, immunohistochemistry and RNA-sequencing on breast cancer samples, we identify four Cancer-Associated Fibroblast (CAF) subpopulations in metastatic lymph nodes (LN). Two myofibroblastic subsets, CAF-S1 and CAF-S4, accumulate in LN and correlate with cancer cell invasion. By developing functional assays on primary cultures, we demonstrate that these subsets promote metastasis through distinct functions. While CAF-S1 stimulate cancer cell migration and initiate an epithelial-to-mesenchymal transition through CXCL12 and TGFβ pathways, highly contractile CAF-S4 induce cancer cell invasion in 3-dimensions via NOTCH signaling. Patients with high levels of CAFs, particularly CAF-S4, in LN at diagnosis are prone to develop late distant metastases. Our findings suggest that CAF subset accumulation in LN is a prognostic marker, suggesting that CAF subsets could be examined in axillary LN at diagnosis.

Cancer Metastasis: The Role of the Extracellular Matrix and the Heparan Sulfate Proteoglycan Perlecan

Cancer metastasis is the dissemination of tumor cells to new sites, resulting in the formation of secondary tumors. This process is complex and is spatially and temporally regulated by intrinsic and extrinsic factors. One important extrinsic factor is the extracellular matrix, the non-cellular component of tissues. Heparan sulfate proteoglycans (HSPGs) are constituents of the extracellular matrix, and through their heparan sulfate chains and protein core, modulate multiple events that occur during the metastatic cascade. This review will provide an overview of the role of the extracellular matrix in the events that occur during cancer metastasis, primarily focusing on perlecan. Perlecan, a basement membrane HSPG is a key component of the vascular extracellular matrix and is commonly associated with events that occur during the metastatic cascade. Its contradictory role in these events will be discussed and we will highlight the recent advances in cancer therapies that target HSPGs and their modifying enzymes.

Promoters to Study Vascular Smooth Muscle

Smooth muscle cells (SMCs) are a critical component of blood vessel walls that provide structural support, regulate vascular tone, and allow for vascular remodeling. These cells also exhibit a remarkable plasticity that contributes to vascular growth and repair but also to cardiovascular pathologies, including atherosclerosis, intimal hyperplasia and restenosis, aneurysm, and transplant vasculopathy. Mouse models have been an important tool for the study of SMC functions. The development of smooth muscle-expressing Cre-driver lines has allowed for exciting discoveries, including recent advances revealing the diversity of phenotypes derived from mature SMC transdifferentiation in vivo using inducible CreER ^T2 lines. We review SMC-targeting Cre lines driven by the Myh11, Tagln, and Acta2 promoters, including important technical considerations associated with these models. Limitations that can complicate study of the vasculature include expression in visceral SMCs leading to confounding phenotypes, and expression in multiple nonsmooth muscle cell types, such as Acta2-Cre expression in myofibroblasts. Notably, the frequently employed Tagln/ SM22α- Cre driver expresses in the embryonic heart but can also confer expression in nonmuscular cells including perivascular adipocytes and their precursors, myeloid cells, and platelets, with important implications for interpretation of cardiovascular phenotypes. With new Cre-driver lines under development and the increasing use of fate mapping methods, we are entering an exciting new era in SMC research.

Fibronectin in the Tumor Microenvironment

Fibronectin (FN) is a large glycoprotein that plays a diverse set of biological roles. This chapter discusses the structural biology, the normal biological functions, and the molecular role of FN and its splice variants in cancer cell proliferation, metastasis, and chemoresistance. The potential role of FN in cancer imaging is discussed in detail. The chapter also discusses the future directions of basic and translational research of fibronectin in the context of the tumor microenvironment and its role in tumor biology.

Cancer-educated mesenchymal stem cells promote the survival of cancer cells at primary and distant metastatic sites via the expansion of bone marrow-derived-PMN-MDSCs

Bone marrow mesenchymal stem cells (BMSCs) are multipotent stromal cells that can differentiate into a variety of cell types. BMSCs are chemotactically guided towards the cancer cells and contribute to the formation of a cancer microenvironment. The homing of BMSCs was affected by various factors. Disseminated tumour cells (DTCs) in distant organs, especially in the bone marrow, are the source of cancer metastasis and cancer relapse. DTC survival is also determined by the microenvironment. Here we aim to elucidate how cancer-educated BMSCs promote the survival of cancer cells at primary tumour sites and distant sites. We highlight the dynamic change by identifying different gene expression signatures in intratumoral BMSCs and in BMSCs that move back in the bone marrow. Intratumoral BMSCs acquire high mobility and displayed immunosuppressive effects. Intratumoral BMSCs that ultimately home to the bone marrow exhibit a strong immunosuppressive function. Cancer-educated BMSCs promote the survival of lung cancer cells via expansion of MDSCs in bone marrow, primary tumour sites and metastatic sites. These Ly6G+ MDSCs suppress proliferation of T cells. CXCL5, nitric oxide and GM-CSF produced by cancer-educated BMSCs contribute to the formation of malignant microenvironments. Treatment with CXCL5 antibody, the iNOS inhibitor 1400w and GM-CSF antibody reduced MDSC expansion in the bone marrow, primary tumour sites and metastatic sites, and promoted the efficiency of PD-L1 antibody. Our study reveals that cancer-educated BMSCs are the component of the niche for primary lung cancer cells and DTCs, and that they can be the target for immunotherapy.

Upregulation of Protease-Activated Receptor 2 Promotes Proliferation and Migration of Human Vascular Smooth Muscle Cells (VSMCs)

Background

Protease-Activated Receptor 2 (PAR2), a G-protein-coupled receptor, has been proved to be enhanced in human coronary atherosclerosis lesions. We aimed to investigate whether PAR2 actively participates in the atherosclerosis process.

Material/Methods

PAR2 expression was assessed in blood samples by RT-qPCR from healthy controls and patients with atherosclerosis. Human vascular smooth muscle cells (VSMCs) were treated with oxidative low-density lipoprotein (ox-LDL). After PAR2 overexpression by transfection, cell proliferation was determined by CCK-8, and cell migration was evaluated by Transwell assay. The protein expressions associated with cell growth and migration were measured by Western blot. The distribution of α-SMA in VSMCs was evaluated by immunofluorescence.

Results

Expression of PAR2 was higher in patients with atherosclerosis compared with normal controls. PAR2 mRNA and protein expression was increased in ox-LDL-treated VSMCs compared with control cells. Induced overexpression of PAR2 in VSMCs led to a reduction in α-SMA expression compared to controls. In addition, PAR2 overexpression caused increased migration compared to normal controls, and upregulated MMP9 and MMP14 expression. PAR-2 overexpression promoted cell proliferation compared to control cells, and increased expression levels of CDK2, and CyclinE1, but reduced levels of p27. We preliminary explored the potential mechanism of PAR2, and results showed that overexpression of PAR2 increased expression levels of VEGFA and Angiopoietin 2 compared to controls. Moreover, overexpression of PAR2 enhanced production of tissue factor and IL-8 compared to normal controls.

Conclusions

PAR2 promotes cell proliferation and disrupts the quiescent condition of VSMCs, which may be a potential therapeutic target for atherosclerosis.

Pericytes in Chronic Lung Disease

Pericytes are supportive mesenchymal cells located on the abluminal surface of the microvasculature, with key roles in regulating microvascular homeostasis, leukocyte extravasation, and angiogenesis. A subpopulation of pericytes with progenitor cell function has recently been identified, with evidence demonstrating the capacity of tissue-resident pericytes to differentiate into the classic MSC triad, i.e., osteocytes, chondrocytes, and adipocytes. Beyond the regenerative capacity of these cells, studies have shown that pericytes play crucial roles in various pathologies in the lung, both acute (acute respiratory distress syndrome and sepsis-related pulmonary edema) and chronic (pulmonary hypertension, lung tumors, idiopathic pulmonary fibrosis, asthma, and chronic obstructive pulmonary disease). Taken together, this body of evidence suggests that, in the presence of acute and chronic pulmonary inflammation, pericytes are not associated with tissue regeneration and repair, but rather transform into scar-forming myofibroblasts, with devastating outcomes regarding lung structure and function. It is hoped that further studies into the mechanisms of pericyte-to-myofibroblast transition and migration to fibrotic foci will clarify the roles of pericytes in chronic lung disease and open up new avenues in the search for novel treatments for human pulmonary pathologies.

Metastatic-niche labelling reveals parenchymal cells with stem features

Direct investigation of the early cellular changes induced by metastatic cells within the surrounding tissue remains a challenge. Here we present a system in which metastatic cancer cells release a cell-penetrating fluorescent protein, which is taken up by neighbouring cells and enables spatial identification of the local metastatic cellular environment. Using this system, tissue cells with low representation in the metastatic niche can be identified and characterized within the bulk tissue. To highlight its potential, we applied this strategy to study the cellular environment of metastatic breast cancer cells in the lung. We report the presence of cancer-associated parenchymal cells, which exhibit stem-cell-like features, expression of lung progenitor markers, multi-lineage differentiation potential and self-renewal activity. In ex vivo assays, lung epithelial cells acquire a cancer-associated parenchymal-cell-like phenotype when co-cultured with cancer cells and support their growth. These results highlight the potential of this method as a platform for new discoveries.