Endothelial CD146 is required for in vitro tumor-induced angiogenesis: The role of a disulfide bond in signaling and dimerization

Netrin-1-CD146 and netrin-1-S100A9 are associated with early stage of lymph node metastasis in colorectal cancer

BACKGROUND

The netrin-1/CD146 pathway regulates colorectal cancer (CRC) liver metastasis, angiogenesis, and vascular development. However, few investigations have yet examined the biological function of netrin-1/CD146 complex in CRC. In this work, we investigated the relationship between the netrin-1/CD146 axis and S100 proteins in sentinel lymph node, and revealed a possible new clue for vascular metastasis of CRC.

METHODS

The expression levels of netrin-1 and CD146 proteins in CRC, as well as S100A8 and S100A9 proteins in the sentinel lymph nodes were determined by immunohistochemistry. Using GEPIA and UALCAN, we analyzed netrin-1 and CD146 gene expression in CRC, their association with CRC stage, and their expression levels and prognosis in CRC patients.

RESULTS

The expression level of netrin-1 in N1a+1b (CRC lymphatic metastasis groups, exculded N1c) was positively increased with N0 (p = 0.012). The level of netrin-1 protein was positively correlated with CD146 protein (p < 0.05). The level of S100A9 protein was positively correlated with CD146 protein (r = 0.492, p = 0.007). Moreover, netrin-1 expression was obviously correlated with S100A9 expression in the N1 stage (r = 0.867, p = 0.000). CD146 level was correlated with S100A9 level in the N2 stage (r = 0.731, p = 0.039). CD146 mRNA expression was higher in normal colorectal tissues than in CRC (p < 0.05). Netrin-1 and CD146 expression were not significantly associated with the tumor stages and prognosis of patients with CRC (p > 0.05).

CONCLUSIONS

The netrin-1/CD146 and netrin-1/S100A9 axis in CRC tissues might related with early stage of lymph node metastasis, thus providing potential novel channels for blocking lymphatic metastasis and guiding biomarker discovery in CRC patients.

CD146, a therapeutic target involved in cell plasticity

Since its identification as a marker for advanced melanoma in the 1980s, CD146 has been found to have multiple functions in both physiological and pathological processes, including embryonic development, tissue repair and regeneration, tumor progression, fibrosis disease, and inflammations. Subsequent research has revealed that CD146 is involved in various signaling pathways as a receptor or co-receptor in these processes. This correlation between CD146 and multiple diseases has sparked interest in its potential applications in diagnosis, prognosis, and targeted therapy. To better comprehend the versatile roles of CD146, we have summarized its research history and synthesized findings from numerous reports, proposing that cell plasticity serves as the underlying mechanism through which CD146 contributes to development, regeneration, and various diseases. Targeting CD146 would consequently halt cell state shifting during the onset and progression of these related diseases. Therefore, the development of therapy targeting CD146 holds significant practical value.

CD146-targeted nuclear medicine imaging in cancer: state of the art

The transmembrane glycoprotein adhesion molecule CD146 is overexpressed in a wide variety of cancers. Through molecular imaging, a specific biomarker's expression and distribution can be viewed in vivo non-invasively. Radionuclide-labeled monoclonal antibodies or relevant fragments that target CD146 may find potential applications in cancer imaging, thereby offering tremendous value in cancer diagnosis, staging, prognosis evaluation, and prediction of drug resistance. This review discusses the recent developments of CD146-targeted molecular imaging via nuclear medicine, especially in malignant melanoma, brain tumor, lung cancer, liver cancer, breast cancer, and pancreatic cancer. Many studies have proved that CD146 targeting may present a promising strategy for cancer theranostics.

S100A8 and S100A9 in Cancer

S100A8 and S100A9 are Ca²⁺ binding proteins that belong to the S100 family. Primarily expressed in neutrophils and monocytes, S100A8 and S100A9 play critical roles in modulating various inflammatory responses and inflammation-associated diseases. Forming a common heterodimer structure S100A8/A9, S100A8 and S100A9 are widely reported to participate in multiple signaling pathways in tumor cells. Meanwhile, S100A8/A9, S100A8, and S100A9, mainly as promoters, contribute to tumor development, growth and metastasis by interfering with tumor metabolism and the microenvironment. In recent years, the potential of S100A8/A9, S100A9, and S100A8 as tumor diagnostic or prognostic biomarkers has also been demonstrated. In addition, an increasing number of potential therapies targeting S100A8/A9 and related signaling pathways have emerged. In this review, we will first expound on the characteristics of S100A8/A9, S100A9, and S100A8 in-depth, focus on their interactions with tumor cells and microenvironments, and then discuss their clinical applications as biomarkers and therapeutic targets. We also highlight current limitations and look into the future of S100A8/A9 targeted anti-cancer therapy.

Markers of local kidney cancer recurrence: A surgeon's mistake or a pattern? Review

The influence of various morphological, anatomical, genetic and other factors on the local recurrence-free survival of patients who have undergone different renal cell cancer (RCC) treatment is still a rather complex, ambiguous and controversial issue for practicing oncourologists. This review evaluates the effect of several factors on both recurrence-free survival and local recurrence-free survival. The review includes articles, clinical cases, literature reviews, and meta-analyses highlighting the analysis of independent and interrelated predisposing factors for developing local recurrence of RCC from 1984 to 2020. The PubMed, Web of Science, and Scopus databases were searched in English, Spanish, and German. A review of the literature showed the role of the following indices in the local recurrence RCC: microvascular invasion (p = 0.001), tumor necrosis (p = 0.0001), high malignancy (Fuhrman III or IV) (HR = 38.3, 95% CI 3.1-467, p = 0.004) as histological factors, tumor size as an anatomical factor. Thus, the authors state that every centimeter of the tumor increases the risk of local recurrence (p < 0.05). A group from the Mayo Clinic showed the equivalence of different treatment methods in local RCC recurrence. Thus, in the group of patients with cT1a stage kidney cancer, the 5-year local recurrence-free survival rates were 97.7% (96.7-98.6), 95.9% (92.3-99.6), and 95.9% (92.3-99.6) for renal resection, RFA, and cryoablation, respectively. Surgical margin status is the most studied and controversial marker of local renal cell carcinoma recurrence. Researchers found a direct effect of PSM on the risk of local RCC recurrence (p < 0.01). The personalized approach with the search and evaluation of predisposing factors for the local recurrence, as well as further selection of the most optimal treatment, will allow oncourologists to improve both the effectiveness of primary treatment and the recurrence-free survival of patients.

Inhibition of CD146 lessens uveal melanoma progression through reducing angiogenesis and vasculogenic mimicry

PURPOSE

Anti-angiogenesis drug therapy is ineffective in treating uveal melanoma since it only targets angiogenesis leaving vasculogenic mimicry aside. There is no effective clinical strategy targeting vasculogenic mimicry, yet. We show here that CD146 is a novel target to inhibit uveal melanoma progression since it regulates both uveal melanoma angiogenesis and vasculogenic mimicry activity.

METHODS

CD146 inhibition was achieved with its specific siRNAs or antibody AA98. Tube formation and migration of primary human retinal microvascular endothelial cells and tube-like structure formation, migration, invasion of uveal melanoma cells were evaluated after CD146 inhibition. The underlying mechanisms were investigated by Western blot and immunofluorescence. Finally, uveal melanoma cells were injected subretinally into the eyes of nude mice and AA98 was administrated. Tumor size was revealed by H&E staining, and angiogenesis and vasculogenic mimicry were evaluated with CD31-PAS staining.

RESULTS

CD146 inhibition induced declines in tube formation and migration of primary human retinal microvascular endothelial cells and tube-like structure formation of uveal melanoma cells. CD146 mediated VEGFR/AKT/p38/NF-κB and FAK/VE-cadherin signal cascades were partially responsible for these biological effects. CD146 blockade by siRNA or AA98 also resulted in inhibition of migration and invasion as well as EMT process of uveal melanoma cells. The physiological relevance of such declines was confirmed by showing that AA98 treatment markedly suppressed the tumor growth, angiogenesis and vasculogenic mimicry induced by implantation of uveal melanoma cells into the eyes of nude mice.

CONCLUSIONS

CD146 is a novel mediator of both angiogenesis and vasculogenic mimicry in uveal melanoma. Its antibody AA98 has the potency to be developed as a new antibody drug for treating uveal melanoma. Our results warrant further assessment of CD146 as a potential target to improve therapeutic management of uveal melanoma in a clinical setting.

CD146 as a promising therapeutic target for retinal and choroidal neovascularization diseases

Blood vessel dysfunction causes several retinal diseases, including diabetic retinopathy, familial exudative vitreoretinopathy, macular degeneration and choroidal neovascularization in pathological myopia. Vascular endothelial growth factor (VEGF)-neutralizing proteins provide benefits in most of those diseases, yet unsolved haemorrhage and frequent intraocular injections still bothered patients. Here, we identified endothelial CD146 as a new target for retinal diseases. CD146 expression was activated in two ocular pathological angiogenesis models, a laser-induced choroid neovascularization model and an oxygen-induced retinopathy model. The absence of CD146 impaired hypoxia-induced cell migration and angiogenesis both in cell lines and animal model. Preventive or therapeutic treatment with anti-CD146 antibody AA98 significantly inhibited hypoxia-induced aberrant retinal angiogenesis in two retinal disease models. Mechanistically, under hypoxia condition, CD146 was involved in the activation of NFκB, Erk and Akt signalling pathways, which are partially independent of VEGF. Consistently, anti-CD146 therapy combined with anti-VEGF therapy showed enhanced impairment effect of hypoxia-induced angiogenesis in vitro and in vivo. Given the critical role of abnormal angiogenesis in retinal and choroidal diseases, our results provide novel insights into combinatorial therapy for neovascular fundus diseases.

CD146 Associates with Gp130 to Control a Macrophage Pro-inflammatory Program That Regulates the Metabolic Response to Obesity

The mechanism of obesity-related metabolic dysfunction involves the development of systemic inflammation, largely mediated by macrophages. Switching of M1-like adipose tissue macrophages (ATMs) to M2-like ATMs, a population of macrophages associated with weight loss and insulin sensitivity, is considered a viable therapeutic strategy for obesity-related metabolic syndrome. However, mechanisms for reestablishing the polarization of ATMs remain elusive. This study demonstrates that CD146+ ATMs accumulate in adipose tissue during diet-induced obesity and are associated with increased body weight, systemic inflammation, and obesity-induced insulin resistance. Inactivating the macrophage CD146 gene or antibody targeting of CD146 alleviates obesity-related chronic inflammation and metabolic dysfunction. Macrophage CD146 interacts with Glycoprotein 130 (Gp130), the common subunit of the receptor signaling complex for the interleukin-6 family of cytokines. CD146/Gp130 interaction promotes pro-inflammatory polarization of ATMs by activating JNK signaling and inhibiting the activation of STAT3, a transcription factor for M2-like polarization. Disruption of their interaction by anti-CD146 antibody or interleukin-6 steers ATMs toward anti-inflammatory polarization, thus attenuating obesity-induced chronic inflammation and metabolic dysfunction in mice. The results suggest that macrophage CD146 is an important determinant of pro-inflammatory polarization and plays a pivotal role in obesity-induced metabolic dysfunction. CD146 could constitute a novel therapeutic target for obesity complications.

Targeting the CD146/Galectin-9 axis protects the integrity of the blood-brain barrier in experimental cerebral malaria

Cerebral malaria (CM) is a life-threatening diffuse encephalopathy caused by Plasmodium falciparum, in which the destruction of the blood-brain barrier (BBB) is the main cause of death. However, increasing evidence has shown that antimalarial drugs, the current treatment for CM, do little to protect against CM-induced BBB damage. Therefore, a means to alleviate BBB dysfunction would be a promising adjuvant therapy for CM. The adhesion molecule CD146 has been reported to be expressed in both endothelial cells and proinflammatory immune cells and mediates neuroinflammation. Here, we demonstrate that CD146 expressed on BBB endothelial cells but not immune cells is a novel therapeutic target in a mouse model of experimental cerebral malaria (eCM). Endothelial CD146 is upregulated during eCM development and facilitates the sequestration of infected red blood cells (RBCs) and/or proinflammatory lymphocytes in CNS blood vessels, thereby promoting the disruption of BBB integrity. Mechanistic studies showed that the interaction of CD146 and Galectin-9 contributes to the aggregation of infected RBCs and lymphocytes. Deletion of endothelial CD146 or treatment with the anti-CD146 antibody AA98 prevents severe signs of eCM, such as limb paralysis, brain vascular leakage, and death. In addition, AA98 combined with the antiparasitic drug artemether improved the cognition and memory of mice with eCM. Taken together, our findings suggest that endothelial CD146 is a novel and promising target in combination with antiparasitic drugs for future CM therapies.

Targeting CD146 using folic acid-conjugated nanoparticles and suppression of tumor growth in a mouse glioma model

OBJECTIVE

Glioma stem cells (GSCs) are responsible for tumor initiation, therapeutic resistance, and recurrence. CD146 is mainly expressed in dividing GSCs and regulates cell cycle progression. However, the evaluation of the efficacy of targeted therapy against CD146 in vivo remains to be investigated. In this study, the authors aimed to develop gene therapy targeting GSCs using chitosan oligosaccharide lactate (COL) nanoparticles (NPs) conjugated with folic acid-polyethylene glycol (FA-PEG-COL NPs) for in vitro and in vivo delivery of CD146 small-interfering RNA (siCD146) and to determine the effect of CD146 knockdown on tumor growth.

METHODS

To examine the uptake of NPs by tumor cells, immunofluorescence staining, flow cytometry, and in vivo imaging were performed. The knockdown effect of siCD146 was measured by western blot and water-soluble tetrazolium salt-8 assay in mouse glioma cells. The efficacy of siRNA therapy-targeted GSCs was evaluated by monitoring tumor growth through in vivo imaging and histological analysis.

RESULTS

In vivo accumulation of the FA-PEG-COL NPs in subcutaneous and intracranial gliomas following NP administration via a mouse tail vein was observed. Additionally, in vitro delivery of siCD146 ionically cross-linked NPs, reduced CD146 levels, and suppressed growth in the glioma tumor sphere. Evaluation of the in vivo therapeutic effects of siCD146-cross-linked NPs in a mouse glioma model revealed significant suppression of intracranial tumor growth, with complete removal of the tumor observed in some mice on histological examination. Furthermore, delivery of siCD146 significantly reduced the Ki-67 index in residual tumor tissues relative to that in control mice.

CONCLUSIONS

CD146 is a potential therapeutic target, and folic acid-conjugated NPs delivering siRNA may facilitate gene therapy in malignant gliomas.

CD146+Mesenchymal stem cells treatment improves vascularization, muscle contraction and VEGF expression, and reduces apoptosis in rat ischemic hind limb

Peripheral arterial disease (PAD) is an increasingly common narrowing of the peripheral arteries that can lead to lower limb ischemia, muscle weakness and gangrene. Surgical vein or arterial grafts could improve PAD, but may not be suitable in elderly patients, prompting research into less invasive approaches. Mesenchymal stem cells (MSCs) have been proposed as potential therapy, but their effectiveness and underlying mechanisms in limb ischemia are unclear. We tested the hypothesis that treatment with naive MSCs (nMSCs) or MSCs expressing CD146 (^CD146+MSCs) could improve vascularity and muscle function in rat model of hind-limb ischemia. Sixteen month old Sprague-Dawley rats were randomly assigned to 4 groups: sham-operated control, ischemia, ischemia + nMSCs and ischemia+^CD146+MSCs. After 4 weeks of respective treatment, rat groups were assessed for ischemic clinical score, Tarlov score, muscle capillary density, TUNEL apoptosis assay, contractile force, and vascular endothelial growth factor (VEGF) mRNA expression. ^CD146+MSCs showed greater CD146 mRNA expression than nMSCs. Treatment with nMSCs or ^CD146+MSCs improved clinical and Tarlov scores, muscle capillary density, contractile force and VEGF mRNA expression in ischemic limbs as compared to non-treated ischemia group. The improvements in muscle vascularity and function were particularly greater in ischemia+^CD146+MSCs than ischemia + nMSCs group. TUNEL positive apoptotic cells were least abundant in ischemia+^CD146+MSCs compared with ischemia + nMSCs and non-treated ischemia groups. Thus, MSCs particularly those expressing CD146 improve vascularity, muscle function and VEGF expression and reduce apoptosis in rat ischemic limb, and could represent a promising approach to improve angiogenesis and muscle function in PAD.

Structure basis for AA98 inhibition on the activation of endothelial cells mediated by CD146

CD146 is an adhesion molecule that plays important roles in angiogenesis, cancer metastasis, and immune response. It exists as a monomer or dimer on the cell surface. AA98 is a monoclonal antibody that binds to CD146, which abrogates the activation of CD146-mediated signaling pathways and shows inhibitory effects on tumor growth. However, how AA98 inhibits the function of CD146 remains unclear. Here, we describe a crystal structure of the CD146/AA98 Fab complex at a resolution of 2.8 Å. Monomeric CD146 is stabilized by AA98 Fab binding to the junction region of CD146 domains 4 and 5. A higher-affinity AA98 variant (here named HA98) was thus rationally designed. Better binding to CD146 and prominent inhibition on cell migration were achieved with HA98. Further experiments on xenografted melanoma in mice with HA98 revealed superior inhibitory effects on tumor growth to those of AA98, which suggested future applications of this antibody in cancer therapy.

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Structural analysis elucidated how mAb AA98 inhibited CD146-mediated EC activation

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AA98-stabilized CD146 in monomer thus inhibited activation of EC

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Higher affinity monoclonal antibody HA98 was rationally designed for cancer treatment

Evaluation of a Novel Plasmid for Simultaneous Gene Electrotransfer-Mediated Silencing of CD105 and CD146 in Combination with Irradiation

Targeting tumor vasculature through specific endothelial cell markers represents a promising approach for cancer treatment. Here our aim was to construct an antibiotic resistance gene-free plasmid encoding shRNAs to simultaneously target two endothelial cell markers, CD105 and CD146, and to test its functionality and therapeutic potential in vitro when delivered by gene electrotransfer (GET) and combined with irradiation (IR). Functionality of the plasmid was evaluated by determining the silencing of the targeted genes using qRT-PCR. Antiproliferative and antiangiogenic effects were determined by the cytotoxicity assay tube formation assay and wound healing assay in murine endothelial cells 2H-11. The functionality of the plasmid construct was also evaluated in malignant melanoma tumor cell line B16F10. Additionally, potential activation of immune response was measured by induction of DNA sensor STING and proinflammatory cytokines by qRT-PCR in endothelial cells 2H-11. We demonstrated that the plasmid construction was successful and can efficiently silence the expression of the two targeted genes. As a consequence of silencing, reduced migration rate and angiogenic potential was confirmed in 2H-11 endothelial cells. Furthermore, induction of DNA sensor STING and proinflammatory cytokines were determined, which could add to the therapeutic effectiveness when used in vivo. To conclude, we successfully constructed a novel plasmid DNA with two shRNAs, which holds a great promise for further in vivo testing.

Tumor Endothelial Cells (TECs) as Potential Immune Directors of the Tumor Microenvironment - New Findings and Future Perspectives

The tumor microenvironment (TME) plays a central role in cancer development and progression. It represents a complex network of cancer cell (sub-)clones and a variety of stromal cell types. Recently, new technology platforms shed light on the cellular composition of the TME at very high resolution and identified a complex landscape of multi-lineage immune cells (e.g., T and B lymphocytes, myeloid cells, and dendritic cells), cancer associated fibroblasts (CAF) and tumor endothelial cells (TECs). A growing body of evidence suggests that metabolically, genetically and on their transcriptomic profile TECs exhibit unique phenotypic and functional characteristics when compared to normal endothelial cells (NECs). Furthermore, the functional role of TECs is multifaceted as they are not only relevant for promoting tumor angiogenesis but have also evolved as key mediators of immune regulation in the TME. Regulatory mechanisms are complex and profoundly impact peripheral immune cell trafficking into the tumor compartment by acting as major gatekeepers of cellular transmigration. Moreover, TECs are associated with T cell priming, activation and proliferation by acting as antigen-presenting cells themselves. TECs are also essential for the formation of tertiary lymphoid structures (TLS) within the tumor, which have recently been associated with treatment response to checkpoint antibody therapy. Further essential characteristics of TECs compared to NECs are their high proliferative potential as well as greatly altered gene expression profile (e.g., upregulation of pro-angiogenic, extracellular matrix remodeling, and stemness genes), which results in enhanced secretion of immunomodulatory cytokines and altered cell-surface receptors [e.g., major histocompatibility complex (MHC) and immune checkpoints]. The TEC phenotype may be rooted in an aggressive tumor micro-milieu based on cellular stress via hypoxia and reactive oxygen species (ROS). Vice versa TECs might modulate TME immunogenicity thereby fostering cancer-associated immune suppression. This review aims to elucidate the currently emergent pathophysiological aspects of TECs with a particular focus on their potential role as regulators of immune cell function in the TME. It is a main future challenge to deeply characterize the phenotypic and functional profile of TECs to illuminate their complex role within the TME. The ultimate goal is the identification of TEC-specific drug targets to improve cancer (immuno-)therapy.

CD146, from a melanoma cell adhesion molecule to a signaling receptor

CD146 was originally identified as a melanoma cell adhesion molecule (MCAM) and highly expressed in many tumors and endothelial cells. However, the evidence that CD146 acts as an adhesion molecule to mediate a homophilic adhesion through the direct interactions between CD146 and itself is still lacking. Recent evidence revealed that CD146 is not merely an adhesion molecule, but also a cellular surface receptor of miscellaneous ligands, including some growth factors and extracellular matrixes. Through the bidirectional interactions with its ligands, CD146 is actively involved in numerous physiological and pathological processes of cells. Overexpression of CD146 can be observed in most of malignancies and is implicated in nearly every step of the development and progression of cancers, especially vascular and lymphatic metastasis. Thus, immunotherapy against CD146 would provide a promising strategy to inhibit metastasis, which accounts for the majority of cancer-associated deaths. Therefore, to deepen the understanding of CD146, we review the reports describing the newly identified ligands of CD146 and discuss the implications of these findings in establishing novel strategies for cancer therapy.

Epithelial-Mesenchymal Transition in Asthma Airway Remodeling Is Regulated by the IL-33/CD146 Axis

Epithelial-mesenchymal transition (EMT) is essential in asthma airway remodeling. IL-33 from epithelial cells is involved in pulmonary fibrosis. CD146 has been extensively explored in cancer-associated EMT. Whether IL-33 regulates CD146 in the EMT process associated with asthma airway remodeling is still largely unknown. We hypothesized that EMT in airway remodeling was regulated by the IL-33/CD146 axis. House dust mite (HDM) extract increased the expression of IL-33 and CD146 in epithelial cells. Increased expression of CD146 in HDM-treated epithelial cells could be blocked with an ST2-neutralizing antibody. Moreover, HDM-induced EMT was dependent on the CD146 and TGF-β/SMAD-3 signaling pathways. IL-33 deficiency decreased CD146 expression and alleviated asthma severity. Similarly, CD146 deficiency mitigated EMT and airway remodeling in a murine model of chronic allergic airway inflammation. Furthermore, CD146 expression was significantly elevated in asthma patients. We concluded that IL-33 from HDM extract-treated alveolar epithelial cells stimulated CD146 expression, promoting EMT in airway remodeling in chronic allergic inflammation.

Deficiency of αII-spectrin affects endothelial cell-matrix contact and migration leading to impairment of angiogenesis in vitro

Background

Precise coordination of cytoskeletal components and dynamic control of cell adhesion and migration are required for crucial cell processes such as differentiation and morphogenesis. We investigated the potential involvement of αII-spectrin, a ubiquitous scaffolding element of the membrane skeleton, in the adhesion and angiogenesis mechanism.

Methods

The cell models were primary human umbilical vein endothelial cells (HUVECs) and a human dermal microvascular endothelial cell line (HMEC-1). After siRNA- and shRNA-mediated knockdown of αII-spectrin, we assessed its expression and that of its partners and adhesion proteins using western blotting. The phenotypes of the control and spectrin-depleted cells were examined using immunofluorescence and video microscopy. Capillary tube formation was assessed using the thick gel Matrigel matrix-based method and a microscope equipped with a thermostatic chamber and a Nikon Biostation System camera.

Results

Knockdown of αII-spectrin leads to: modified cell shape; actin cytoskeleton organization with the presence of peripheral actin patches; and decreased formation of stress fibers. Spectrin deficiency affects cell adhesion on laminin and fibronectin and cell motility. This included modification of the localization of adhesion molecules, such as αVβ3- and α5-integrins, and organization of adhesion structures, such as focal points. Deficiency of αII-spectrin can also affect the complex mechanism of in vitro capillary tube formation, as demonstrated in a model of angiogenesis. Live imaging revealed that impairment of capillary tube assembly was mainly associated with a significant decrease in cell projection length and stability. αII-spectrin depletion is also associated with significantly decreased expression of three proteins involved in capillary tube formation and assembly: VE-cadherin, MCAM and β3-integrin.

Conclusion

Our data confirm the role of αII-spectrin in the control of cell adhesion and spreading. Moreover, our findings further support the participation of αII-spectrin in capillary tube formation in vitro through control of adhesion molecules, such as integrins. This indicates a new function of αII-spectrin in angiogenesis.

Treatment of Hepatocellular Carcinoma by Intratumoral Injection of 125I-AA98 mAb and Its Efficacy Assessments by Molecular Imaging

Objective: To investigate the therapeutic efficacy of intratumoral injection of ¹²⁵I-AA98 mAb for hepatocellular carcinoma (HCC) and its therapy efficacy assessment by ^99mTc-HYNIC-duramycin and ^99mTc-HYNIC-3PRGD2 SPECT/CT imaging.

Methods: HCC xenograft tumor mice models were injected intratumorally with a single dose of normal saline, 10 microcurie (μCi) ¹²⁵I-AA98 mAb, free ¹²⁵I, AA98 mAb, 80 μCi ¹²⁵I-AA98 mAb, and 200 μCi ¹²⁵I-AA98 mAb. ^99mTc-HYNIC-duramycin and ^99mTc-HYNIC-3PRGD2 micro-SPECT/CT imaging were performed on days 3 and 7, respectively. The T/M ratio for each imaging was compared with the corresponding immunohistochemical staining at each time point. The relative tumor inhibition rates were documented.

Results: In terms of apoptosis, the 200 μCi group demonstrated the highest apoptotic index (11.8 ± 3.8%), and its T/M ratio achieved by ^99mTc-HYNIC-duramycin imaging on day 3 was higher than that of the normal saline group, 80 μCi group, 10 μCi group and free ¹²⁵I group on day 3, respectively (all P < 0.05). On day 3, there was a markedly positive correlation between T/M ratio from ^99mTc-HYNIC-duramycin imaging and apoptotic index by TUNEL staining (r = 0.6981; P < 0.05). Moreover, the 200 μCi group showed the lowest T/M ratio on ^99mTc-HYNIC-3PRGD2 imaging (1.0 ± 0.5) on day 7 (all P < 0.05) comparing to other groups. The T/M ratio on day 7 was not correlated with integrin α_νβ₃ staining (P > 0.05). The relative inhibitory rates of tumor on day 14 in the AA98 mAb, 10 μCi, 80 μCi, free ¹²⁵I, and 200 μCi groups were 26.3, 55.3, 60.5, 66.3, and 69.5%, respectively.

Conclusion:¹²⁵I-AA98 mAb showed more effective apoptosis induced ability for CD146 high expression Hep G2 HCC cells and hold the potential for HCC treatment. Moreover, ^99mTc-HYNIC-Duramycin (apoptosis-targeted) imaging and ^99mTc-HYNIC-3PRGD2 (angiogenesis-targeted) imaging are reliable non-invasive methods to evaluate the efficacy of targeted treatment of HCC.

Phage display screening of therapeutic peptide for cancer targeting and therapy

Recently, phage display technology has been announced as the recipient of Nobel Prize in Chemistry 2018. Phage display technique allows high affinity target-binding peptides to be selected from a complex mixture pool of billions of displayed peptides on phage in a combinatorial library and could be further enriched through the biopanning process; proving to be a powerful technique in the screening of peptide with high affinity and selectivity. In this review, we will first discuss the modifications in phage display techniques used to isolate various cancer-specific ligands by in situ, in vitro, in vivo, and ex vivo screening methods. We will then discuss prominent examples of solid tumor targeting-peptides; namely peptide targeting tumor vasculature, tumor microenvironment (TME) and over-expressed receptors on cancer cells identified through phage display screening. We will also discuss the current challenges and future outlook for targeting peptide-based therapeutics in the clinics.

CD146 T cells in lung cancer: its function, detection, and clinical implications as a biomarker and therapeutic target

CD146 alternatively called melanoma cell adhesion molecule (MCAM), is a biomarker and therapeutic target of clinical significance. It is found on different cells including the endothelial cells and lymphocytes which participate in heterotypic and homotypic ligand-receptor. This review concentrated on the CD146 expression T cells (or lymphocytes) centering on Treg in lung cancer. Here, we have also considered the vigorous investigation of CD146 mainly acknowledged new roles, essential mechanisms and clinical implications of CD146 in cancer. CD146 has progressively become a significant molecule, particularly recognized as a novel biomarker, prognosis and therapy for cancer. Hence, targeting CD146 expression by utilization of methanol extracts of Calotropis procera leaf may be useful for the treatment of carcinogenesis.

Dimerization and phosphorylation of Lutheran/basal cell adhesion molecule are critical for its function in cell migration on laminin

Tumor cell migration depends on the interactions of adhesion proteins with the extracellular matrix. Lutheran/basal cell adhesion molecule (Lu/BCAM) promotes tumor cell migration by binding to laminin α5 chain, a subunit of laminins 511 and 521. Lu/BCAM is a type I transmembrane protein with a cytoplasmic domain of 59 (Lu) or 19 (Lu(v13)) amino acids. Here, using an array of techniques, including site-directed mutagenesis, immunoblotting, FRET, and proximity-ligation assays, we show that both Lu and Lu(v13) form homodimers at the cell surface of epithelial cancer cells. We mapped two small-XXX-small motifs in the transmembrane domain as potential sites for monomers docking and identified three cysteines in the cytoplasmic domain as being critical for covalently stabilizing dimers. We further found that Lu dimerization and phosphorylation of its cytoplasmic domain were concomitantly needed to promote cell migration. We conclude that Lu is the critical isoform supporting tumor cell migration on laminin 521 and that the Lu:Lu(v13) ratio at the cell surface may control the balance between cellular firm adhesion and migration.

CD146-HIF-1α hypoxic reprogramming drives vascular remodeling and pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a vascular remodeling disease of cardiopulmonary units. No cure is currently available due to an incomplete understanding of vascular remodeling. Here we identify CD146-hypoxia-inducible transcription factor 1 alpha (HIF-1α) cross-regulation as a key determinant in vascular remodeling and PAH pathogenesis. CD146 is markedly upregulated in pulmonary artery smooth muscle cells (PASMCs/SMCs) and in proportion to disease severity. CD146 expression and HIF-1α transcriptional program reinforce each other to physiologically enable PASMCs to adopt a more synthetic phenotype. Disruption of CD146-HIF-1α cross-talk by genetic ablation of Cd146 in SMCs mitigates pulmonary vascular remodeling in chronic hypoxic mice. Strikingly, targeting of this axis with anti-CD146 antibodies alleviates established pulmonary hypertension (PH) and enhances cardiac function in two rodent models. This study provides mechanistic insights into hypoxic reprogramming that permits vascular remodeling, and thus provides proof of concept for anti-remodeling therapy for PAH through direct modulation of CD146-HIF-1α cross-regulation.

Clinical significance of melanoma cell adhesion molecule CD146 and VEGFA expression in epithelial ovarian cancer

Ovarian cancer is the fifth most common type of cancer in females; however, its asymptomatic progression and the lack of an efficient screening strategy leads to late diagnosis. The present study aimed to investigate the expression levels of cluster of differentiation (CD)146 and vascular endothelial growth factor A (VEGFA) in epithelial ovarian cancer, and their clinical significance. A total of 52 ovarian samples were tested, of which 22 were from patients with epithelial ovarian cancer and 30 were from non-cancer patients. The relative gene expression of CD146 and VEGFA was quantified using reverse transcription-quantitative polymerase chain reaction analysis. Western blotting was used to determine the protein expression levels. The relative gene expression levels of CD146 and VEGFA in tumor tissues were significantly increased compared with the control (4.92±0.44 vs. 1.05±0.06 and 3.08±0.17 vs. 1.06±0.07, P<0.01). The protein expression levels of CD146 and VEGFA in tumor tissue were also significantly increased compared with the control (0.70±0.02 vs. 0.41±0.07 and 0.54±0.01 vs. 0.26±0.01, P<0.01). There was a positive correlation between the expression levels of CD146 and VEGFA genes (r=0.78) and between the two proteins (r=0.69). Dot density frequency analysis indicated that CD146 and VEGFA were specifically present in tumor tissues. In conclusion, CD146 and VEGFA are co-overexpressed in ovarian cancer; their potential as tumor biomarkers or therapeutic targets for the treatment of ovarian cancer requires further investigation.

Markers for human brain pericytes and smooth muscle cells

Brain pericytes and vascular smooth muscle cells (vSMCs) are a critical component of the neurovascular unit and are important in regulating cerebral blood flow and blood-brain barrier integrity. Identification of subtypes of mural cells in tissue and in vitro is important to any study of their function, therefore we identified distinct mural cell morphologies in neurologically normal post-mortem human brain. Further, the distribution of mural cell markers platelet-derived growth factor receptor-β (PDGFRβ), α-smooth muscle actin (αSMA), CD13, neural/glial antigen-2 (NG2), CD146 and desmin was examined. We determined that PDGFRβ, NG2, CD13, and CD146 were expressed in capillary-associated pericytes. NG2, and CD13 were also present on vSMCs in large vessels, however abundant CD146 and desmin staining was also detected in vSMCs on large vessels, co-labelling with αSMA. To determine whether cultures recapitulated observations from tissue, primary human brain pericytes derived from neurologically normal autopsies were analysed for the presence of pericyte markers by immunocytochemistry, western blotting and qPCR. The proteins observed in brain pericytes in tissue (PDGFRβ, αSMA, desmin, CD146, CD13, and NG2) were present in vitro, validating a panel of proteins that can be used to label brain pericytes and vSMCs in tissue and in vitro. Finally, we showed that the proteins CD146 and desmin that are expressed on large vessels in situ, are also selective markers of a smooth muscle cell phenotype in vitro.

The dark side of tumor-associated endothelial cells

Angiogenesis is a hallmark of cancer and a requisite that tumors must achieve to fulfill their metabolic needs of nutrients and oxygen. As a critical step in cancer progression, the 'angiogenic switch' allows tumor cells to survive and grow, and provides them access to vasculature resulting in metastatic progression and dissemination. Tumor-dependent triggering of the angiogenic switch has critical consequences on tumor progression which extends from an increased nutrient supply and relies instead on the ability of the tumor to hijack the host immune response for the generation of a local immunoprivileged microenvironment. Tumor angiogenic-mediated establishment of endothelial anergy is responsible for this process. However, tumor endothelium can also promote immune tolerance by unbalanced expression of co-stimulatory and co-inhibitory molecules and by releasing soluble factors that restrain T cell function and induce apoptosis. In this review, we discuss the molecular properties of the tumor endothelial barrier and endothelial anergy and discuss the main immunosuppressive mechanisms triggered by the tumor endothelium. Lastly, we describe the current anti-angiogenic therapeutic landscape and how targeting tumor angiogenesis can contribute to improve clinical benefits for patients.

CD146 coordinates brain endothelial cell-pericyte communication for blood-brain barrier development

The blood-brain barrier (BBB) establishes a protective interface between the central neuronal system and peripheral blood circulation and is crucial for homeostasis of the CNS. BBB formation starts when the endothelial cells (ECs) invade the CNS and pericytes are recruited to the nascent vessels during embryogenesis. Despite the essential function of pericyte-EC interaction during BBB development, the molecular mechanisms coordinating the pericyte-EC behavior and communication remain incompletely understood. Here, we report a single cell receptor, CD146, that presents dynamic expression patterns in the cerebrovasculature at the stages of BBB induction and maturation, coordinates the interplay of ECs and pericytes, and orchestrates BBB development spatiotemporally. In mouse brain, CD146 is first expressed in the cerebrovascular ECs of immature capillaries without pericyte coverage; with increased coverage of pericytes, CD146 could only be detected in pericytes, but not in cerebrovascular ECs. Specific deletion of Cd146 in mice ECs resulted in reduced brain endothelial claudin-5 expression and BBB breakdown. By analyzing mice with specific deletion of Cd146 in pericytes, which have defects in pericyte coverage and BBB integrity, we demonstrate that CD146 functions as a coreceptor of PDGF receptor-β to mediate pericyte recruitment to cerebrovascular ECs. Moreover, we found that the attached pericytes in turn down-regulate endothelial CD146 by secreting TGF-β1 to promote further BBB maturation. These results reveal that the dynamic expression of CD146 controls the behavior of ECs and pericytes, thereby coordinating the formation of a mature and stable BBB.

Nestin and cluster of differentiation 146 expression in breast cancer: Predicting early recurrence by targeting metastasis?

The purpose of this study was to investigate the relationship between the expression of stem-cell markers nestin and cluster of differentiation 146 with clinicopathological characteristics in breast cancer and to determine whether a prognostic impact of nestin and CD146 expression exists regarding occurrence of disease relapse in breast cancer. A total of 141 patients who were histologically diagnosed with breast cancer and underwent radical operations from November 2006 to October 2013 in Laiko General Hospital, National and Kapodistrian University of Athens, were enrolled in the study. CD146 and nestin protein expression were evaluated using immunohistochemistry. Nestin expression was observed in 18.4% (26/141) of the cases, while CD146 expression was observed in 35.5% (50/141) of the cases. Nestin expression is significantly higher in younger patients with breast cancer. Nestin and CD146 expression were not correlated with the tumor size and the presence of lymph node metastasis. On the contrary, a significantly higher expression of nestin and CD146 was observed with triple-negative cancers (p < 0.0001 for both markers), low differentiated tumors (p = 0.021 for nestin and p = 0.008 for CD146), and increased Ki-67 expression (p = 0.007 for nestin and p < 0.0001 for CD146). The nestin-positive group of patients and the CD146-positive group of patients presented significantly higher rates of disease recurrence (log-rank test, p = 0.022 for nestin and p = 0.003 for CD146) with a distant metastasis, 30 months after the primary treatment. CD146 but not nestin, however, predicted independently (p = 0.047) disease recurrence. Nestin and CD146 are expressed in breast cancer cells with highly aggressive potency. They might contribute to disease relapse in breast cancer by activating the epithelial-mesenchymal transition pathway and assist tumor neovascularization.

Macrophagic CD146 promotes foam cell formation and retention during atherosclerosis

The persistence of cholesterol-engorged macrophages (foam cells) in the artery wall fuels the development of atherosclerosis. However, the mechanism that regulates the formation of macrophage foam cells and impedes their emigration out of inflamed plaques is still elusive. Here, we report that adhesion receptor CD146 controls the formation of macrophage foam cells and their retention within the plaque during atherosclerosis exacerbation. CD146 is expressed on the macrophages in human and mouse atheroma and can be upregulated by oxidized low-density lipoprotein (oxLDL). CD146 triggers macrophage activation by driving the internalization of scavenger receptor CD36 during lipid uptake. In response to oxLDL, macrophages show reduced migratory capacity toward chemokines CCL19 and CCL21; this capacity can be restored by blocking CD146. Genetic deletion of macrophagic CD146 or targeting of CD146 with an antibody result in much less complex plaques in high-fat diet-fed ApoE-/- mice by causing lipid-loaded macrophages to leave plaques. Collectively, our findings identify CD146 as a novel retention signal that traps macrophages within the artery wall, and a promising therapeutic target in atherosclerosis treatment.

MCAM/CD146 promotes tamoxifen resistance in breast cancer cells through induction of epithelial-mesenchymal transition, decreased ERα expression and AKT activation

Tamoxifen resistance presents a prominent clinical challenge in endocrine therapy for hormone sensitive breast cancer. However, the underlying mechanisms that contribute to tamoxifen resistance are not fully understood. In this study, we established a tamoxifen resistant MCF-7 cell line (MCF-7-Tam-R) by continuously incubating MCF-7 cells with 4-OH-tamoxifen. We found that melanoma cell adhesion molecule (MCAM/CD146), a unique epithelial-to-mesenchymal transition (EMT) inducer, was significantly up-regulated at both mRNA and protein levels in MCF-7-Tam-R cells compared to parental MCF-7 cells. Mechanistic research demonstrated that MCAM promotes tamoxifen resistance by transcriptionally suppressing ERα expression and activating the AKT pathway, followed by induction of EMT. Elevated MCAM expression was inversely correlated with recurrence-free and distant metastasis-free survival in a cohort of 4142 patients with breast cancer derived from a public database, particularly in the subgroup only treated with tamoxifen. These results demonstrate a novel function of MCAM in conferring tamoxifen resistance in breast cancer. Targeting MCAM might be a promising therapeutic strategy to overcome tamoxifen resistance in breast cancer patients.

Inhibiting CD146 by its Monoclonal Antibody AA98 Improves Radiosensitivity of Cervical Cancer Cells

Background

Cervical cancer is one of the major causes of cancer death of females worldwide. Radiotherapy is considered effective for cervical cancer treatment, but the low radiosensitivity found in some cases severely affects therapeutic outcomes. This study aimed to reveal the role of CD146, an important adhesion molecule facilitating tumor angiogenesis, in regulating radiosensitivity of cervical cancer cells.

Material/Methods

CD146 protein expression was compared in normal cells, cervical cancer cells with lower radiosensitivity, and cervical cancer cells with higher sensitivity from cervical squamous cell carcinoma patients. Anti-CD146 monoclonal antibody AA98 was used to inhibit CD146 in human cervical cancer SiHa cells with relatively low radiosensitivity, and then the cell survival and apoptosis changes after radiation were detected by colony formation assay and flow cytometry.

Results

CD146 protein was significantly up-regulated in cervical cancer cells (P<0.001), especially in cancer cells with lower radiosensitivity. The SiHa cells treated with AA98 showed more obvious inhibition in cell survival (P<0.05) and promotion in cell apoptosis (P<0.01) after radiation, compared to the untreated cells. More dramatic changes in apoptotic factors Caspase 3 and Bcl-XL were also detected in AA98-treated cells.

Conclusions

These results indicate that inhibiting CD146 improves the effect of radiation in suppressing SiHa cells. This study shows the potential of CD146 as a target for increasing radiosensitivity of cervical cancer cells, which might allow improvement in treatment outcome in cervical cancer. Further studies are necessary for understanding the detailed mechanism of CD146 in regulating radiosensitivity.

Comparative prognostic relevance of breast intra-tumoral microvessel density evaluated by CD105 and CD146: A pilot study of 42 cases

Angiogenesis is a key process for metastatic progression. While it has been established that the evaluation of breast tumoral microvessel density by CD105 marker is a potential prognostic parameter, its evaluation by CD146 marker has been poorly studied.

AIM

The purpose of this study was to compare the prognostic value of intra-tumoral microvessel density assayed by CD105 and CD146 in early breast cancer patients.

METHODS

42 women with breast infiltrative ductal carcinoma (I and II-stages) were retrospectively reviewed. Intra-tumoral microvessel density was immunohistochemically examined using antibodies anti-CD105 and CD146 in paraffin-embedded tissues, and their association with classical prognostic-markers, metastatic recurrence, metastasis-free survival and overall survival was analyzed.

RESULTS

High microvessel density assessed by CD146 was significantly associated with a higher risk of developing metastasis (p=0.0310) and a shorter metastasis-free survival (p=0.0197). In contrast, when we used the CD105-antibody, we did not find any significant association. Finally, CD146 showed to be an independent predictive indicator for metastasis-free survival (p=0.0055).

CONCLUSION

Our data suggest that the intra-tumoral microvessel density evaluated by CD146 may be a more suitable predictor of metastatic development than that evaluated by CD105 in early breast cancer.

Selection of scFv Antibody Fragments Binding to Human Blood versus Lymphatic Endothelial Surface Antigens by Direct Cell Phage Display

The identification of marker molecules specific for blood and lymphatic endothelium may provide new diagnostic tools and identify new targets for therapy of immune, microvascular and cancerous diseases. Here, we used a phage display library expressing human randomized single-chain Fv (scFv) antibodies for direct panning against live cultures of blood (BECs) and lymphatic (LECs) endothelial cells in solution. After six panning rounds, out of 944 sequenced antibody clones, we retrieved 166 unique/diverse scFv fragments, as indicated by the V-region sequences. Specificities of these phage clone antibodies for respective compartments were individually tested by direct cell ELISA, indicating that mainly pan-endothelial cell (EC) binders had been selected, but also revealing a subset of BEC-specific scFv antibodies. The specific staining pattern was recapitulated by twelve phage-independently expressed scFv antibodies. Binding capacity to BECs and LECs and differential staining of BEC versus LEC by a subset of eight scFv antibodies was confirmed by immunofluorescence staining. As one antigen, CD146 was identified by immunoprecipitation with phage-independent scFv fragment. This antibody, B6-11, specifically bound to recombinant CD146, and to native CD146 expressed by BECs, melanoma cells and blood vessels. Further, binding capacity of B6-11 to CD146 was fully retained after fusion to a mouse Fc portion, which enabled eukaryotic cell expression. Beyond visualization and diagnosis, this antibody might be used as a functional tool. Overall, our approach provided a method to select antibodies specific for endothelial surface determinants in their native configuration. We successfully selected antibodies that bind to antigens expressed on the human endothelial cell surfaces in situ, showing that BECs and LECs share a majority of surface antigens, which is complemented by cell-type specific, unique markers.

CD146: the unveiling of a pro-angiogenic netrin receptor

Netrin-1, a classic neuronal guidance cue, can promote angiogenesis under certain developmental and pathological conditions, but key receptors on vascular endothelium have remained elusive. A recent study published in Cell Research by Tu et al. reveals that CD146, an endothelial receptor of the immunoglobulin superfamily, binds netrin-1 with high affinity and may play an important role in regulating angiogenesis.

CD146 acts as a novel receptor for netrin-1 in promoting angiogenesis and vascular development

Angiogenesis, a process that newly-formed blood vessels sprout from pre-existing ones, is vital for vertebrate development and adult homeostasis. Previous studies have demonstrated that the neuronal guidance molecule netrin-1 participates in angiogenesis and morphogenesis of the vascular system. Netrin-1 exhibits dual activities in angiogenesis: either promoting or inhibiting angiogenesis. The anti-angiogenic activity of netrin-1 is mediated by UNC5B receptor. However, how netrin-1 promotes angiogenesis remained unclear. Here we report that CD146, an endothelial transmembrane protein of the immunoglobulin superfamily, is a receptor for netrin-1. Netrin-1 binds to CD146 with high affinity, inducing endothelial cell activation and downstream signaling in a CD146-dependent manner. Conditional knockout of the cd146 gene in the murine endothelium or disruption of netrin-CD146 interaction by a specific anti-CD146 antibody blocks or reduces netrin-1-induced angiogenesis. In zebrafish embryos, downregulating either netrin-1a or CD146 results in vascular defects with striking similarity. Moreover, knocking down CD146 blocks ectopic vascular sprouting induced by netrin-1 overexpression. Together, our data uncover CD146 as a previously unknown receptor for netrin-1 and also reveal a functional ligand for CD146 in angiogenesis, demonstrating the involvement of netrin-CD146 signaling in angiogenesis during vertebrate development.

The multifaceted role of CD146/MCAM in the promotion of melanoma progression

Human malignant melanoma is a common primary malignant cutaneous tumour derived from transformed epidermal melanocytes. Patients with melanoma have a high rate of mortality due to resistance to chemotherapeutic drugs, a major obstacle to a successful treatment. Several reports have suggested that CD146 plays an important role as a signalling molecule in human melanoma. This role includes CD146 as a participant in inflammation, differentiation, adhesion, tumourigenicity, metastasis, invasion and angiogenesis among other processes, which suggests that this molecule promotes the progression of human melanoma as a multifaceted regulator. In this article, we explore the effects and corresponding mechanisms with respect to the role of CD146/MUC18 in the promotion of human melanoma progression. Collectively, the studies indicated that targeting CD146, because it is a suitable marker of poor patient outcome, might be useful in the design of future strategies for the prevention and treatment of human melanoma.

Adult mesenchymal stem cells and women's health

Adult mesenchymal stem cells (MSCs) were previously described as multipotent cells that could differentiate into bone, cartilage, muscle, and other mesenchymal tissues. New information suggests that MSCs can be found in every tissue of the body because they function as perivascular cells--pericytes--found outside all blood vessels. When these vessels break or are inflamed, pericytes are detached and form MSCs, which are activated by their local microenvironment of injury. Such MSCs function to secrete powerful immune-modulatory and regenerative agents; more than 450 clinical trials are now ongoing, covering a huge spectrum of clinical conditions. How such activated MSCs affect menstrual cycle, menopause, or osteotrophic cancers has only recently been studied. This article outlines these issues and challenges the scientific and medical community to use this newfound knowledge to uncover new clinical logics and medial solutions for women.

Impaired tumor angiogenesis and VEGF-induced pathway in endothelial CD146 knockout mice

CD146 is a newly identified endothelial biomarker that has been implicated in angiogenesis. Though in vitro angiogenic function of CD146 has been extensively reported, in vivo evidence is still lacking. To address this issue, we generated endothelial-specific CD146 knockout (CD146(EC-KO)) mice using the Tg(Tek-cre) system. Surprisingly, these mice did not exhibit any apparent morphological defects in the development of normal retinal vasculature. To evaluate the role of CD146 in pathological angiogenesis, a xenograft tumor model was used. We found that both tumor volume and vascular density were significantly lower in CD146(EC-KO) mice when compared to WT littermates. Additionally, the ability for sprouting, migration and tube formation in response to VEGF treatment was impaired in endothelial cells (ECs) of CD146(EC-KO) mice. Mechanistic studies further confirmed that VEGF-induced VEGFR-2 phosphorylation and AKT/p38 MAPKs/NF-κB activation were inhibited in these CD146-null ECs, which might present the underlying cause for the observed inhibition of tumor angiogenesis in CD146(EC-KO) mice. These results suggest that CD146 plays a redundant role in physiological angiogenic processes, but becomes essential during pathological angiogenesis as observed in tumorigenesis.

Targeting endothelial CD146 attenuates colitis and prevents colitis-associated carcinogenesis

Recently, enhanced CD146 expression was reported on endothelial cells in intestinal biopsies from patients with inflammatory bowel disease. However, the underlying mechanism remains unknown. Here, we found that overexpressed endothelial CD146 promoted the inflammatory responses in inflammatory bowel disease, which further potentiated the occurrence of colitis-associated colorectal carcinogenesis. Eliminating endothelial CD146 by conditional knockout significantly ameliorated the severity of inflammation in two different murine models of colitis, and decreased tumor incidence and tumor progression in a murine model of colitis-associated colorectal carcinogenesis. Mechanistic study showed that cytokine tumor necrosis factor-α (TNF-α) up-regulated the expression of endothelial CD146 through NF-κB transactivation. In turn, the enhanced endothelial CD146 expression promoted both angiogenesis and proinflammatory leukocyte extravasations, contributing to inflammation. Using an anti-CD146 antibody, AA98, alone or together with an anti-TNF-α antibody significantly attenuated colitis and prevented colitis-associated colorectal carcinogenesis in mice. Our study provides the first evidence that CD146 plays a dual role on endothelium, facilitating leukocyte extravasations and angiogenesis, thus promoting inflammation. This finding not only reveals the function and regulating mechanism of CD146 in inflammatory bowel disease, but also provides a promising therapeutic strategy for treating inflammatory bowel disease and preventing colitis-associated colorectal carcinogenesis.

Adhesion molecule CD146 and its soluble form correlate well with carotid atherosclerosis and plaque instability

AIMS

Intraplaque neovascularization and foam cell infiltration contribute to the development of unstable plaque, leading to thromboembolism and stroke. Cell adhesion molecules (CAMs) have been reported to be involved in the progression of atherosclerosis and plaque vulnerability. The aim of this study was to assess the association of adhesion molecule CD146 with carotid plaque instability.

METHODS

We collected forty atherosclerotic plaques from 40 patients undergoing carotid endarterectomy. The clinical information of each patient was obtained, and the plaque morphology and characteristics were examined by the ultrasound. The CD146 expressions of the plaques were graded by using semiquantitative scales. The serum level of soluble form of CD146 was detected by enzyme-linked immunosorbent assay (ELISA).

RESULTS

CD146 expression was mainly on the intraplaque blood vessels and infiltrated macrophages. The CD146 expression was strongly correlated with the matrix metalloproteinase-9(MMP-9)expressions (P < 0.001) in the plaques. Soluble CD146 (sCD146) was also elevated in patients with atherosclerotic plaques. There was significant correlation between the increased CD146 expression and sCD146 level (P = 0.0057). sCD146 correlated well with serum MMP-9 (P < 0.0044), IL-6 (P = 0.0044) and high sensitivity C-reactive protein (hsCRP) (P = 0.005).

CONCLUSIONS

Adhesion molecules CD146 and its soluble form strongly correlated with the development of inflammation of atherosclerosis and plaque instability. CD146 may be a promising biomarker for monitoring the development and instability of atherosclerotic plaque in patients with carotid diseases.

Quantitative proteomics reveals ER-α involvement in CD146-induced epithelial-mesenchymal transition in breast cancer cells

The cell adhesion molecule CD146 is a novel inducer of epithelial-mesenchymal transition (EMT), which was associated with triple-negative breast cancer (TNBC). To gain insights into the complex networks that mediate CD146-induced EMT in breast cancers, we conducted a triple Stable Isotope Labeling with Amino Acids in Cell Culture (SILAC), to analyze whole cell protein profiles of MCF-7 cells that had undergone gradual EMT upon CD146 expression from moderate to high levels. In this study, we identified 2293 proteins in total, of which 103 exhibited changes in protein abundance that correlated with CD146 expression levels, revealing extensive morphological and biochemical changes associated with EMT. Ingenuity Pathway Analysis (IPA) showed that estrogen receptor (ER) was the most significantly inhibited transcription regulator during CD146-induced EMT. Functional assays further revealed that ER-α expression was repressed in cells undergoing CD146-induced EMT, whereas re-expression of ER-α abolished their migratory and invasive behavior. Lastly, we found that ER-α mediated its effects on CD146-induced EMT via repression of the key EMT transcriptional factor Slug. Our study revealed the molecular details of the complex signaling networks during CD146-induced EMT, and provided important clues for future exploration of the mechanisms underlying the association between CD146 and TNBC as observed in the clinic.

BIOLOGICAL SIGNIFICANCE

This study used a proteomics screen to reveal molecular changes mediated by CD146-induced epithelial-mesenchymal transition (EMT) in breast cancer cells. Estrogen receptor (ER) was found to be the most significantly inhibited transcription regulator, which mediated its effects on CD146-induced EMT via repression of the transcriptional factor Slug. Elucidation of protein interaction networks and signal networks generated from 103 significantly changed proteins would facilitate future investigation into the mechanisms underlying CD146 induced-EMT in breast cancers.

Control of the adaptive immune response by tumor vasculature

The endothelium is nowadays described as an entire organ that regulates various processes: vascular tone, coagulation, inflammation, and immune cell trafficking, depending on the vascular site and its specific microenvironment as well as on endothelial cell-intrinsic mechanisms like epigenetic changes. In this review, we will focus on the control of the adaptive immune response by the tumor vasculature. In physiological conditions, the endothelium acts as a barrier regulating cell trafficking by specific expression of adhesion molecules enabling adhesion of immune cells on the vessel, and subsequent extravasation. This process is also dependent on chemokine and integrin expression, and on the type of junctions defining the permeability of the endothelium. Endothelial cells can also regulate immune cell activation. In fact, the endothelial layer can constitute immunological synapses due to its close interactions with immune cells, and the delivery of co-stimulatory or co-inhibitory signals. In tumor conditions, the vasculature is characterized by an abnormal vessel structure and permeability, and by a specific phenotype of endothelial cells. All these abnormalities lead to a modulation of intra-tumoral immune responses and contribute to the development of intra-tumoral immunosuppression, which is a major mechanism for promoting the development, progression, and treatment resistance of tumors. The in-depth analysis of these various abnormalities will help defining novel targets for the development of anti-tumoral treatments. Furthermore, eventual changes of the endothelial cell phenotype identified by plasma biomarkers could secondarily be selected to monitor treatment efficacy.

MicroRNA signature and function in retinal neovascularization

Ischemic retinopathies are clinically well-defined chronic microvascular complications characterized by gradually progressive alterations in the retinal microvasculature and a compensatory aberrant neovascularization of the eye. The subsequent metabolic deficiencies result in structural and functional alterations in the retina which is highly susceptible to injurious stimuli such as diabetes, trauma, hyperoxia, inflammation, aging and dysplipidemia. Emerging evidence indicates that an effective therapy may require targeting multiple components of the angiogenic pathway. Conceptually, mircoRNA (miRNA)-based therapy provides the rationale basis for an effective antiangiogenic treatment. miRNAs are an evolutionarily conserved family of short RNAs, each regulating the expression of multiple protein-coding genes. The activity of specific miRNAs is important for vascular cell signaling and blood vessel formation and function. Recently, important progress has been made in mapping the miRNA-gene target network and miRNA-mediated gene expression control. Here we highlight the latest findings on angiogenic and antiangiogenic miRNAs and their targets as well as potential implications in ocular neovascular diseases. Emphasis is placed on how specific vascular-enriched miRNAs regulate cell responses to various cues by targeting several factors, receptors and/or signaling molecules in order to maintain either vascular function or dysfunction. Further improvement of our knowledge in not only miRNA specificity, turnover, and transport but also how miRNA sequences and functions can be altered will enhance the therapeutic utility of such molecules.

Melanoma biomolecules: independently identified but functionally intertwined

The majority of patients diagnosed with melanoma present with thin lesions and generally these patients have a good prognosis. However, 5% of patients with early melanoma (<1 mm thick) will have recurrence and die within 10 years, despite no evidence of local or metastatic spread at the time of diagnosis. Thus, there is a need for additional prognostic markers to help identify those patients that may be at risk of recurrent disease. Many studies and several meta-analyses have compared gene and protein expression in melanocytes, naevi, primary, and metastatic melanoma in an attempt to find informative prognostic markers for these patients. However, although a large number of putative biomarkers have been described, few of these molecules are informative when used in isolation. The best approach is likely to involve a combination of molecules. We believe one approach could be to analyze the expression of a group of interacting proteins that regulate different aspects of the metastatic pathway. This is because a primary lesion expressing proteins involved in multiple stages of metastasis may be more likely to lead to secondary disease than one that does not. This review focuses on five putative biomarkers – melanoma cell adhesion molecule (MCAM), galectin-3 (gal-3), matrix metalloproteinase 2 (MMP-2), chondroitin sulfate proteoglycan 4 (CSPG4), and paired box 3 (PAX3). The goal is to provide context around what is known about the contribution of these biomarkers to melanoma biology and metastasis. Although each of these molecules have been independently identified as likely biomarkers, it is clear from our analyses that each are closely linked with each other, with intertwined roles in melanoma biology.

MicroRNA 329 suppresses angiogenesis by targeting CD146

CD146, an endothelial biomarker, has been shown to be aberrantly upregulated during pathological angiogenesis and functions as a coreceptor for vascular endothelial growth factor receptor 2 (VEGFR-2) to promote disease progression. However, the regulatory mechanisms of CD146 expression during angiogenesis remain unclear. Using a microRNA screening approach, we identified a novel negative regulator of angiogenesis, microRNA 329 (miR-329), that directly targeted CD146 and inhibited CD146-mediated angiogenesis in vitro and in vivo. Endogenous miR-329 expression was downregulated by VEGF and tumor necrosis factor alpha (TNF-α), resulting in the elevation of CD146 in endothelial cells. Upregulation of CD146 facilitated an endothelial response to VEGF-induced SRC kinase family (SKF)/p38 mitogen-activated protein kinase (MAPK)/NF-κB activation and consequently promoted endothelial cell migration and tube formation. Our animal experiments showed that treatment with miR-329 repressed excessive CD146 expression on blood vessels and significantly attenuated neovascularization in a mouse model of pathological angiogenesis. Our findings provide the first evidence that CD146 expression in angiogenesis is regulated by miR-329 and suggest that miR-329 could present a potential therapeutic tool for the treatment of angiogenic diseases.

Soluble CD146 in cerebrospinal fluid of active multiple sclerosis

The soluble form of CD146 has been reported to be present in various inflammatory diseases and displays pro-inflammatory properties. However, little is known about sCD146 in multiple sclerosis (MS). Here we show that sCD146 is significantly elevated in the cerebrospinal fluid of patients with active MS compared with that of inactive MS or patients with non-demyelinating diseases. Moreover, abnormally increased sCD146 in the CSF of active MS patients correlated with albumin quotient, MBP antibody and MOG antibody from both CSF and sera. Importantly, the level of CSF sCD146 is correlated with levels of inflammatory factors, such as TNFα, IFNγ, IL-2, and IL-17A in the CSF. We also found that CSF sCD146 might originate from membrane-bound CD146 on inflamed blood-brain barrier (BBB) endothelial cells. In addition, sCD146 promotes leukocyte transmigration in vitro, at least in part by stimulating the expression of ICAM-1 and VCAM-1 on endothelial cells. Our findings suggest that CSF levels of sCD146 may provide a potential marker for monitoring disease activity in MS patients.