Up-regulation of METCAM/MUC18 promotes motility, invasion, and tumorigenesis of human breast cancer cells

Mcam stabilizes a luminal progenitor-like breast cancer cell state via Ck2 control and Src/Akt/Stat3 attenuation

Cell state control is crucial for normal tissue development and cancer cell mimicry of stem/progenitor states, contributing to tumor heterogeneity, therapy resistance, and progression. Here, we demonstrate that the cell surface glycoprotein Mcam maintains the tumorigenic luminal progenitor (LP)-like epithelial cell state, leading to Basal-like mammary cancers. In the Py230 mouse mammary carcinoma model, Mcam knockdown (KD) destabilized the LP state by deregulating the Ck2/Stat3 axis, causing a switch to alveolar and basal states, loss of an estrogen-sensing subpopulation, and resistance to tamoxifen-an effect reversed by Ck2 and Stat3 inhibitors. In vivo, Mcam KD blocked generation of Basal-like tumors and Sox10+Krt14+ cells. In human tumors, MCAM loss was largely exclusive of the Basal-like subtype, linked instead to proliferative Luminal subtypes, including often endocrine-resistant Luminal B cancers. This study has implications for developing therapies targeting MCAM, CK2, and STAT3 and their likely effective contexts.

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.

METCAM/MUC18 Plays a Tumor Suppressor Role in the Development of Nasopharyngeal Carcinoma Type I

From previous studies of negatively correlating the expression of human METCAM/MUC18 with the pathology of nasopharyngeal carcinoma (NPC), we have suggested that human METCAM/MUC18 (huMETCAM/MUC18) might play a tumor suppressor role in the development of nasopharyngeal carcinoma. To scrutinize this hypothesis, we investigated the effects of huMETCAM/MUC18′s over-expression on in vitro cellular behavior and on the in vivo tumorigenesis of one NPC cell line (NPC-TW01). HuMETCAM/MUC18 cDNA was first transfected into the NPC-TW01 cell line, which was established from NPC type I, and many G418-resistant clones were obtained. Then, two NPC-TW01 clones, which expressed high and medium levels of huMETCAM/MUC18, respectively, and one empty vector (control) clone were used to test the effects of huMETCAM/MUC18′s over-expression on in vitro behaviors and on in vivo tumorigenesis (via subcutaneous injection) in athymic nude mice (Balb/cAnN.Cg-Foxnl^nu/Cr1Nar1). The time course of tumor proliferation and the final tumor weights were determined. Tumor sections were used for the histology and immunohistochemistry (IHC) studies. Tumor lysates were used for determining the expression levels of huMETCAM/MUC18 and various downstream key effectors. HuMETCAM/MUC18′s over-expression reduced in vitro motility and invasiveness and altered growth behaviors in 3D basement membrane culture assays, and it decreased the in vivo tumorigenicity of the NPC-TW01 cells. The tumor cells from a high-expressing clone were clustered and confined in small areas, whereas those from a vector control clone were more spread out, suggesting that the tumor cells from the high-expressing clone appeared to stay dormant in micro-clusters. Expression levels of the proliferation index, an index of the metabolic switch to aerobic glycolysis, angiogenesis indexes, and survival pathway indexes were reduced, whereas the pro-apoptosis index increased in the corresponding tumors. The over-expression of huMETCAM/MUC18 in the NPC-TW01 cells decreased the epithelial-to-mesenchymal transition and the in vitro and in vitro tumorigenesis, suggesting that it plays a tumor suppressor role in the development of type I NPC, perhaps by increasing apoptosis and decreasing angiogenesis, proliferation, and the metabolic switch to aerobic glycolysis.

Overexpression of MCAM induced by SMYD2-H3K36me2 in breast cancer stem cell properties

BACKGROUND

Melanoma cell adhesion molecule (MCAM) is highly expressed in various malignancies. However, studies on the effects of MCAM on stemness of cancer stem cells are limited. Here, we aimed to explore the relationship between MCAM and stem cell phenotype in breast cancer (BC).

METHODS

We analyzed the genes differentially expressed in BC from the oncomine database, followed by TCGA-BRCA database validation. We then used gene set enrichment analysis to analyze the signaling pathways enriched to the relevant genes, followed by loss-of-function experiments to analyze the role of MCAM in the growth of BC cells and the maintenance of stem cell properties. We analyzed the cause for the MCAM overexpression using ChIP-seq and clarified the upstream mechanism by constructing SE-Deleted cells. Finally, the role of SMYD2 in the growth of BC cells and the maintenance of stem cell properties were verified by rescue experiments.

RESULTS

MCAM was significantly overexpressed in BC, which predicted somber prognosis in patients. Knockdown of MCAM drastically hindered the growth and metastasis of BC cells in vitro and in vivo. Subsequently, the MCAM promoter was observed to have significant H3K36me2 modification and that SMYD2 could significantly promote the expression of MCAM. In addition, further overexpression of SMYD2 in cells with MCAM knockdown increased MCAM expression and promoted the growth as well as stemness of BC cells.

CONCLUSION

SMYD2 can elevate the expression of MCAM by promoting its H3K36me2 modification, which in turn expedites the growth and stem cell properties of BC cells.

Transmembrane MUC18 Targeted Polydopamine Nanoparticles and a Mild Photothermal Effect Synergistically Disrupt Actin Cytoskeleton and Migration of Cancer Cells

Transmembrane MUC18 is highly expressed on most metastatic cancers. Herein, we demonstrate that targeting MUC18 with polydopamine nanoparticles (PDA NPs) and a mild photothermal effect can completely cease the migration of melanoma and breast cancer cells without killing the cells. The inhibited cell migration can be attributed to the altered actin cytoskeleton, cell stiffness, and cell morphology, as revealed by nanomechanical and super resolution fluorescence imaging techniques. Further mechanistic studies at the molecular level show that MUC18 targeted PDA NPs and a mild photothermal treatment produce a synergistic effect on the actin cytoskeleton by downregulating the transmembrane MUC18 and interrupting ezrin-radixin-moesin phosphorylation, thereby releasing the actin cytoskeleton from the cell membrane and compromising force transduction through the actin cytoskeleton to the transmembrane MUC18. Overall, the concept of targeting transmembrane metastatic markers and disrupting their downstream effectors (i.e., actin and actin-binding proteins) opens up a new avenue to cancer therapy.

Enforced Expression of METCAM/MUC18 Decreases In Vitro Motility and Invasiveness and Tumorigenesis and In Vivo Tumorigenesis of Human Ovarian Cancer BG-1 Cells

OBJECTIVES

We tested if METCAM/MUC18 overexpression also plays a suppressor role in another human ovarian cancer cell line, BG-1, in addition to the SK-OV3 cell line.

METHODS

Human ovarian cancer BG-1 cells were transfected with METCAM/MUC18 cDNA and G418-resistant clones expressing different levels of METCAM/MUC18 were isolated. These clones were used to test the effects of enforced expression of METCAM/MUC18 on in vitro motility, invasiveness, and anchorage-independent colony formation (in vitro tumorigenesis), and in vivo tumorigenesis after SC injection and after IP injection in female athymic nude mice.

RESULTS

Overexpression of METCAM/MUC18 reduced in vitro motility and invasiveness of BG-1 cells and anchorage-independent colony formation (in vitro tumor formation). Higher expression of METCAM/MUC18 in BG-1 cells significantly reduced in vivo tumor proliferation of the BG-1 cells after IP injection (orthotopic route) of the clones in female nude mice, though it did not significantly affect in vivo tumor proliferation after SC injection (non-orthotopic route).

CONCLUSION

Similar to SK-OV3 cells, METCAM/MUC18 also plays a suppressor role in the progression of BG-1 cells in a xenograft mouse model.

Recognize the role of CD146/MCAM in the osteosarcoma progression: an in vitro study

Background

Osteosarcoma (OS) is a common malignant bone tumor with poor prognosis. We previously reviewed that CD146 is correlated with multiple cancer progression, while its impact on OS is currently not systematically studied.

Methods

MG63 was transfected with lentivirus to express CD146 ectopically, and anti-CD146 neutralizing antibody ab75769 was used to inhibit 143B. Cyclic migration of MG63 and co-culture between MG63 and 143B were used to explore the role of OS malignancy in CD146 expression. The effect of OS cell medium (CM) on endothelium behaviors was assessed, and the expression changes of CD146 before and after co-culture of endothelium and OS were evaluated. Finally, the expression of CD146 in OS was detected under different culture conditions, including hyperoxia, low oxygen, high glucose and low glucose conditions.

Results

CD146 promoted the colony formation, migration, invasion and homotypic adhesion of OS cells, and reducing the concentration of soluble CD146 in the OS medium inhibited the proliferation, migration and lumen formation of the cultured endothelium. However, CD146 did not affect the adhesion between OS and endothelium, nor did co-culture of both sides affect the CD146 expression. Similarly, the proliferation, migration and CD146 expression of MG63 remained unchanged after many cycles of migration itself, as did its co-culture with 143B for expressing CD146. In addition, we also showed that high glucose promoted the expression of CD146 in OS, while hypoxia had the opposite effect.

Conclusions

These findings demonstrate that CD146 promotes OS progression by mediating pro-tumoral and angiogenic effects. Thus, CD146 could be a potential therapeutic target for OS, especially for OS patients with diabetes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02006-7.

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.

Ral GTPases promote breast cancer metastasis by controlling biogenesis and organ targeting of exosomes

Cancer extracellular vesicles (EVs) shuttle at distance and fertilize pre-metastatic niches facilitating subsequent seeding by tumor cells. However, the link between EV secretion mechanisms and their capacity to form pre-metastatic niches remains obscure. Using mouse models, we show that GTPases of the Ral family control, through the phospholipase D1, multi-vesicular bodies homeostasis and tune the biogenesis and secretion of pro-metastatic EVs. Importantly, EVs from RalA or RalB depleted cells have limited organotropic capacities in vivoand are less efficient in promoting metastasis. RalA and RalB reduce the EV levels of the adhesion molecule MCAM/CD146, which favors EV-mediated metastasis by allowing EVs targeting to the lungs. Finally, RalA, RalB, and MCAM/CD146, are factors of poor prognosis in breast cancer patients. Altogether, our study identifies RalGTPases as central molecules linking the mechanisms of EVs secretion and cargo loading to their capacity to disseminate and induce pre-metastatic niches in a CD146-dependent manner.

Microphthalmia-Associated Transcription Factor-Dependent Melanoma Cell Adhesion Molecule Activation Promotes Peritoneal Metastasis of Ovarian Cancer

Ovarian cancer (OvCa) is one of the leading causes of death due to its high metastasis rate to the peritoneum. Recurrent peritoneal tumors also develop despite the use of conventional platinum-based chemotherapies. Therefore, it is still important to explore the factors associated with peritoneal metastasis, as these predict the prognosis of patients with OvCa. In this study, we investigated the function of microphthalmia-associated transcription factor (MITF), which contributes to the development of melanoma, in epithelial ovarian cancer (OvCa). High MITF expression was significantly associated with a poor prognosis in OvCa. Notably, MITF contributed to the motility and invasion of OvCa cells, and specifically with their peri-mesothelial migration. In addition, MITF-positive cells expressed the melanoma cell adhesion molecule (MCAM/CD146), which was initially identified as a marker of melanoma progression and metastasis, and MCAM expression was regulated by MITF. MCAM was also identified as a significant prognostic factor for poor progression-free survival in patients with OvCa. Collectively, our results suggest that MITF is a novel therapeutic target that potentially promotes peritoneal metastasis of OvCa.

Therapeutic targeting of soluble CD146/MCAM with the M2J-1 monoclonal antibody prevents metastasis development and procoagulant activity in CD146-positive invasive tumors

Initially discovered in human melanoma, CD146/MCAM is expressed on many tumors and is correlated with cancer progression and metastasis. However, targeting CD146 remains challenging since it is also expressed on other cell types, as vessel cells, where it displays important physiological functions. We previously demonstrated that CD146 is shed as a soluble form (sCD146) that vectorizes the effects of membrane CD146 on tumor angiogenesis, growth and survival. We thus generated a novel monoclonal antibody, the M2J-1 mAb, which specifically targets sCD146, but not membrane CD146, and counteracts these effects. In our study, we analyzed the effects of sCD146 on the dissemination and the associated procoagulant phenotype in two highly invasive human CD146-positive cancer cell lines (ovarian and melanoma). Results show that sCD146 induced epithelial to mesenchymal transition, favored the generation of cancer stem cells and increased the membrane expression of tissue factor. Treatment of cancer cells with sCD146 in two experimental models (subcutaneous xenografting and intracardiac injection of cancer cells in nude mice) led to increased tumor dissemination and procoagulant activity. The M2J-1 mAb drastically reduced metastasis but also procoagulant activity, in particular by decreasing the number of circulating tumor microparticles, and blocked the relevant signaling pathways as demonstrated by RNA expression profiling experiments. Thus, our findings demonstrate that sCD146 mediates important pro-metastatic and procoagulant effects in two CD146-positive tumors. Targeting sCD146 with the newly generated M2J-1 mAb could constitute an innovative strategy for preventing dissemination and thromboembolism in many CD146-positive tumors.

CD146 (Cluster of Differentiation 146)

CD146 (cluster of differentiation 146) is an adhesion molecule that is expressed by different cells constituting vessels, particularly endothelial cells. The last 30 years of research in this field have shown that CD146 plays a key role in the control of several vessel functions. Three forms of CD146 have been described, including 2 transmembrane isoforms and a soluble protein that is detectable in the plasma. These CD146 forms mediate pleiotropic functions through homophilic and heterophilic interactions with proteins present on surrounding partners. Several studies used neutralizing antibodies, siRNA, or genetically modified mice to demonstrate the involvement of CD146 in the regulation of angiogenesis, vascular permeability, and leukocyte transmigration. In this review, we will focus on the current knowledge of the roles of CD146 in vascular homeostasis and diseases associated with endothelial dysfunction.

Immunoglobulin superfamily genes are novel prognostic biomarkers for breast cancer

Breast cancer progression is associated with dysregulated expression of the immunoglobulin superfamily (IgSF) genes that are involved in cell-cell recognition, binding and adhesion. Despite widespread evidence that many IgSF genes could serve as effective biomarkers, this potential has not been realized because the studies have focused mostly on individual genes and not the entire network. To gain a global perspective of the IgSF-related biomarkers, we constructed an IgSF-directed neighbor network (IDNN) and an IgSF-directed driver network (IDDN) by integrating multiple levels of data, including IgSF genes, breast cancer driver genes, protein-protein interaction (PPI) networks and gene expression profiling data. Our study shows that IgSF genes in the PPI network have important topological features related to cancer. Most IgSF genes are either cancer driver genes themselves or associated with them. We also identified a 21-gene IgSF network module with enriched mutations that are associated with overall survival based on 450 breast cancer patient samples extracted from The Cancer Genome Atlas (TCGA) and multiple independent microarray validation datasets. These results highlight the potential of IgSF genes as novel diagnostic, prognostic and therapeutic targets for breast cancer.

A novel anti-CD146 antibody specifically targets cancer cells by internalizing the molecule

CD146 is an adhesion molecule present on many tumors (melanoma, kidney, pancreas, breast, ...). In addition, it has been shown to be expressed on vascular endothelial and smooth muscle cells. Generating an antibody able to specifically recognize CD146 in cancer cells (designated as tumor CD146), but not in normal cells, would thus be of major interest for targeting tumor CD146 without affecting the vascular system.

We thus generated antibodies against the extracellular domain of the molecule produced in cancer cells and selected an antibody that specifically recognizes tumor CD146. This antibody (TsCD146 mAb) was able to detect CD146-positive tumors in human biopsies and in vivo, by PET imaging, in a murine xenograft model. In addition, TsCD146 mAb antibody was able to specifically detect CD146-positive cancer microparticles in the plasma of patients. TsCD146 mAb displayed also therapeutic effects since it was able to reduce the growth of human CD146-positive cancer cells xenografted in nude mice. This effect was due to a decrease in the proliferation and an increase in the apoptosis of CD146-positive cancer cells after TsCD146-mediated internalization of the cell surface CD146.

Thus, TsCD146 mAb could be of major interest for diagnostic and therapeutic strategies against CD146-positive tumors in a context of personalized medicine.

METCAM/MUC18 promoted tumorigenesis of human breast cancer SK-BR-3 cells in a dosage-specific manner

OBJECTIVE

Overexpression of METCAM/MUC18, an immunoglobulin-like cell-adhesion molecule, promotes tumorigenesis and progression of human breast cancer cells. We also observed an intriguing phenomenon that a high-expressing SK-BR-3 clone manifested a transient tumor suppression effect in vivo. The purpose of this study was to understand if this was caused by clonal variation, METCAM/MUC18-dosage effect, or the number of cells injected.

MATERIALS AND METHODS

Several G418-resistant clones of SK-BR-3, expressing different levels of METCAM/MUC18, were obtained for testing effects of human METCAM/MUC18 on in vitro motility, invasiveness, and anchorage-independent colony formation (in vitro tumorigenicity) and in vivo tumorigenesis in female Balb/C athymic nude mice. Tumor sections were made for histology and immunohistochemistry analyses, and tumor lysates for Western blot analysis to determine the effects of human METCAM/MUC18 expression on levels of various downstream effectors.

RESULTS

METCAM/MUC18 promoted in vitro motility, invasiveness, and in vitro tumorigenicity of SK-BR-3 cells in a dosage-specific manner. Overexpression of METCAM/MUC18 could promote in vivo tumorigenesis of SK-BR-3 cells even when one tenth of the previously used cell number (5 × 10(5)) was injected and in vivo tumorigenesis of SK-BR-3 cells was directly proportional to the dosage of the protein. The previously observed transient tumor suppression effect from the same clone was no longer observed. The downstream effector, such as phospho-AKT/AKT ratio, was elevated in the tumors.

CONCLUSION

Transient suppression observed previously in the clone was caused by injection of a high cell number (2 × 10(6)-5 × 10(6)). METCAM/MUC18 positively promotes tumorigenesis of SK-BR-3 cells by increasing the survival and proliferation pathway.

Ectopic expression of MCAM/MUC18 increases in vitro motility and invasiveness, but decreases in vivo tumorigenesis and metastasis of a mouse melanoma K1735-9 subline in a syngeneic mouse model

Ectopic expression of MCAM/MUC18, a cell adhesion molecule in the immunoglobulin-like gene superfamily, induces two moMCAM/MUC18-minus, non-metastatic mouse melanoma K1735 sublines, K3 (tumor⁺/met^low) and K10 (tumor^-/met^low), to metastasize to lungs in a syngeneic C3H mouse model. In this report, we extended investigation of effects of moMCAM/MUC18 expression on tumorigenesis and metastasis in another lowly metastatic, however highly tumorigenic moMCAM/MUC18-minus mouse melanoma K1735 subline, K9 (tumor⁺⁺⁺/met^low). We transfected this subline with the moMCAM/MUC18 cDNA, selected for G418-resistant clones with different expression levels of moMCAM/MUC18, and used them for testing effects of MCAM/MUC18 expression on in vitro growth rate, motility, and invasiveness, in vivo subcutaneous tumor growth, and pulmonary metastasis in syngeneic C3H brown mice. Similar to K3 and K10 cells, increased expression of MCAM/MUC18 in K9 cells did not significantly affect in vitro growth rate, but increased in vitro motility and invasiveness. Surprisingly, increased expression of MCAM/MUC18 in K9 cells decreased their induction of tumorigenesis and suppressed their establishment of pulmonary nodules in syngeneic C3H brown mice. We concluded that increased MCAM/MUC18 expression in K9 subline increased in vitro epithelial-to-mesenchymal transition; however, it suppressed in vivo tumorigenicity and metastasis. Thus MCAM/MUC18 acts as a tumor and metastasis suppressor for the K9 subline, different from its role in other K1735 sublines, K3 and K10. Different intrinsic co-factors in different K1735 sublines, which modulate the functions of MCAM/MUC18 in the cells that interact differently to the tumor microenvironment, may render sublines manifest differently in tumorigenicity and metastasis in vivo.

Polyphenol-rich strawberry extract (PRSE) shows in vitro and in vivo biological activity against invasive breast cancer cells

We describe the biological effects of a polyphenol-rich strawberry extract (PRSE), obtained from the “Alba” variety, on the highly aggressive and invasive basal-like breast cancer cell line A17. Dose-response and time-course experiments showed that PRSE is able to decrease the cellular viability of A17 cells in a time- and dose-dependent manner. PRSE effect on cell survival was investigated in other tumor and normal cell lines of both mouse and human origin, demonstrating that PRSE is more active against breast cancer cells. Cytofluorimetric analysis of A17 cells demonstrated that sub-lethal doses of PRSE reduce the number of cells in S phase, inducing the accumulation of cells in G1 phase of cell cycle. In addition, the migration of A17 cells was studied monitoring the ability of PRSE to inhibit cellular mobility. Gene expression analysis revealed the modulation of 12 genes playing different roles in the cellular migration, adhesion and invasion processes. Finally, in vivo experiments showed the growth inhibition of A17 cells orthotopically transplanted into FVB syngeneic mice fed with PRSE. Overall, we demonstrated that PRSE exerts important biological activities against a highly invasive breast cancer cell line both in vitro and in vivo suggesting the strawberry extracts as preventive/curative food strategy.

The proteome signature of the inflammatory breast cancer plasma membrane identifies novel molecular markers of disease

Inflammatory Breast Cancer (IBC) is the most lethal form of breast cancer with a 35% 5-year survival rate. The accurate and early diagnosis of IBC and the development of targeted therapy against this deadly disease remain a great medical challenge. Plasma membrane proteins (PMPs) such as E-cadherin and EGFR, play an important role in the progression of IBC. Because the critical role of PMPs in the oncogenic processes they are the perfect candidates as molecular markers and targets for cancer therapies. In the present study, Stable Isotope Labeling with Amino Acids in Cell Culture (SILAC) followed by mass spectrometry analysis was used to compare the relative expression levels of membrane proteins (MP) between non-cancerous mammary epithelial and IBC cells, MCF-10A and SUM-149, respectively. Six of the identified PMPs were validated by immunoblotting using the membrane fractions of non-IBC and IBC cell lines, compared with MCF-10A cells. Immunohistochemical analysis using IBC, invasive ductal carcinoma or normal mammary tissue samples was carried out to complete the validation method in nine of the PMPs. We identified and quantified 278 MPs, 76% of which classified as PMPs with 1.3-fold or higher change. We identified for the first time the overexpression of the novel plasminogen receptor, PLGRKT in IBC and of the carrier protein, SCAMP3. Furthermore, we describe the positive relationship between L1CAM expression and metastasis in IBC patients and the role of SCAMP3 as a tumor-related protein. Overall, the membrane proteomic signature of IBC reflects a global change in cellular organization and suggests additional strategies for cancer progression. Together, this study provides insight into the specialized IBC plasma membrane proteome with the potential to identify a number of novel therapeutic targets for IBC.

Breast cancer cells compete with hematopoietic stem and progenitor cells for intercellular adhesion molecule 1-mediated binding to the bone marrow microenvironment

Adhesion-based cellular interactions involved in breast cancer metastasis to the bone marrow remain elusive. We identified that breast cancer cells directly compete with hematopoietic stem and progenitor cells (HSPCs) for retention in the bone marrow microenvironment. To this end, we established two models of competitive cell adhesion-simultaneous and sequential-to study a potential competition for homing to the niche and displacement of the endogenous HSPCs upon invasion by tumor cells. In both models, breast cancer cells but not non-tumorigenic cells competitively reduced adhesion of HSPCs to bone marrow-derived mesenchymal stromal cells (MSCs) in a tumor cell number-dependent manner. Higher adhesive force between breast cancer cells and MSCs, as compared with HSPCs, assessed by quantitative atomic force microscopy-based single-cell force spectroscopy could partially account for tumor cell mediated reduction in HSPC adhesion to MSCs. Genetic inactivation and blockade studies revealed that homophilic interactions between intercellular adhesion molecule 1 (ICAM-1) expressed on tumor cells and MSCs, respectively, regulate the competition between tumor cells and HSPCs for binding to MSCs. Moreover, tumor cell-secreted soluble ICAM-1(sICAM-1) also impaired HSPC adhesion via blocking CD18-ICAM-1 binding between HSPCs and MSCs. Xenotransplantation studies in NOD.Cg-Prkdc(scid) Il2rg(tm1Wjl)/SzJ mice revealed reduction of human HSPCs in the bone marrow via metastatic breast cancer cells. These findings point to a direct competitive interaction between disseminated breast cancer cells and HSPCs within the bone marrow micro environment. This interaction might also have implications on niche-based tumor support. Therefore, targeting this cross talk may represent a novel therapeutic strategy.

METCAM/MUC18 is a novel tumor and metastasis suppressor for the human ovarian cancer SKOV3 cells

BACKGROUND

Increased expression of METCAM/MUC18, a trans-membrane cell adhesion molecule in the Ig-like gene superfamily, has been associated with the malignant progression of epithelial ovarian carcinomas. To investigate if this is a fortuitous correlation or if METCAM/MUC18 actually plays a role in the progression of the cancer, we tested effects of enforced expression of METCAM/MUC18 on in vitro behaviors, in vivo tumorigenesis, and in vivo malignant progression of human ovarian cancer SK-OV-3 cells, which minimally expressed this protein.

METHODS

For in vitro and in vivo tests, we transfected human METCAM/MUC18 cDNA gene into SK-OV-3 cells in a mammalian expression vector pcDNA3.1+ and obtained G418-resistant (G418(R)) clones, which expressed various levels of human METCAM/MUC18. To mimic physiological situations, we used pooled METCAM/MUC18-expressing and control (vector) clones for testing effects of human METCAM/MUC18 over-expression on in vitro motility and invasiveness, and on in vivo tumor formation and metastasis in female athymic nude mice. Effects of METCAM/MUC18 on the expression of various downstream key factors related to tumorigenesis were also evaluated by Western blot analyses.

RESULTS

The over-expression of METCAM/MUC18 inhibited in vitro motility and invasiveness of SK-OV-3 cells. SK-OV-3 cells of the control (vector) clone (3D), which did not express human METCAM/MUC18, supported the formation of a solid tumor after SC injection of the cells at dorsal or ventral sites and also formation of solid tumor and ascites after IP injection in the intraperitoneal cavity of nude mice. In contrast, SK-OV-3 cells from the METCAM/MUC18-expressing clone (2D), which expressed a high level of METCAM/MUC18, did not support the formation of a solid tumor at SC sites, or formation of ascites in the intraperitoneal cavity of nude mice. Expression levels of downstream key factors, which may affect tumor proliferation and angiogenesis, were reduced in tumors induced by the METCAM/MUC18-expressing clone (2D).

CONCLUSIONS

We conclude that increased human METCAM/MUC18 expression in ovarian cancer SK-OV-3 cells suppressed tumorigenesis and ascites formation in nude mice, suggesting that human METCAM/MUC18 plays a suppressor role in the progression of ovarian cancer, perhaps by reducing proliferation and angiogenesis.

Evodiamine inhibits the migration and invasion of nasopharyngeal carcinoma cells in vitro via repressing MMP-2 expression

PURPOSE

Evodiamine is one of active alkaloids isolated from the traditional Chinese medicine Evodia rutaecarpa Bentham and has various pharmacological properties. In this study, we investigated its effects on the migration, invasion, and associated mechanism in human nasopharyngeal carcinoma (NPC) cells.

METHODS

Cell viability was determined by MTT assay after evodiamine treatment. Wound-healing assay and Boyden transwell system were used to evaluate the inhibitory effects of evodiamine on cell migration and invasion. MMP-2/9 activity was determined using commercial detection kits. The levels of associated proteins involved in the regulation of cell migration and invasion were analyzed by Western blotting.

RESULTS

Evodiamine effectively inhibited the migration and invasion of HONE1 and CNE1 cells, and hardly affected cell proliferation, but significantly suppressed cell adhesion activity in vitro. Additionally, evodiamine treatment significantly decreased mRNA and protein levels of MMP-2 and its activity in the NPC cells, but had little effects on MMP-9 mRNA and protein levels and its activity. Further investigation revealed that evodiamine inhibited the translocation of NF-κB p65, which involves the regulation of MMP-2 expression in cancer invasion. Additionally, evodiamine treatment did not significantly affect the protein levels of JNK, p38, Akt, and their phosphorylated forms and ERK1/2, but strongly attenuated ERK1/2 phosphorylation level, which at least partly accounts for the signal pathway of evodiamine-inhibited migration and invasion of NPC cells.

CONCLUSION

These findings demonstrate that evodiamine inhibits the migration and invasiveness of NPC cells, and it is probably a potential agent for the treatment of NPC invasion and metastasis.

Cancer metastases: challenges and opportunities

Cancer metastasis is the major cause of cancer morbidity and mortality, and accounts for about 90% of cancer deaths. Although cancer survival rate has been significantly improved over the years, the improvement is primarily due to early diagnosis and cancer growth inhibition. Limited progress has been made in the treatment of cancer metastasis due to various factors. Current treatments for cancer metastasis are mainly chemotherapy and radiotherapy, though the new generation anti-cancer drugs (predominantly neutralizing antibodies for growth factors and small molecule kinase inhibitors) do have the effects on cancer metastasis in addition to their effects on cancer growth. Cancer metastasis begins with detachment of metastatic cells from the primary tumor, travel of the cells to different sites through blood/lymphatic vessels, settlement and growth of the cells at a distal site. During the process, metastatic cells go through detachment, migration, invasion and adhesion. These four essential, metastatic steps are inter-related and affected by multi-biochemical events and parameters. Additionally, it is known that tumor microenvironment (such as extracellular matrix structure, growth factors, chemokines, matrix metalloproteinases) plays a significant role in cancer metastasis. The biochemical events and parameters involved in the metastatic process and tumor microenvironment have been targeted or can be potential targets for metastasis prevention and inhibition. This review provides an overview of these metastasis essential steps, related biochemical factors, and targets for intervention.

Frequent and increased expression of human METCAM/MUC18 in cancer tissues and metastatic lesions is associated with the clinical progression of human ovarian carcinoma

OBJECTIVES

Human METCAM/MUC18 (huMETCAM/MUC18), a cell adhesion molecule, plays an important role in the progression of several epithelial cancers; however, its role in the progression of epithelial ovarian cancers is unknown. To initiate the study we determined expression of this protein in normal and cancerous ovarian tissues, cystadenomas, metastatic lesions, and ovarian cancer cell lines.

MATERIALS AND METHODS

Immunoblotting and immunohistochemical (IHC) methods were used to determine huMETCAM/MUC18 expression in lysates of frozen and formalin-fixed, paraffin-embedded tissue sections of normal human ovaries, and ovarian (benign) cystadenomas, carcinomas and metastatic lesions. We also determined expression levels of several downstream effectors of METCAM/MUC18 in these tissues.

RESULTS

HuMETCAM/MUC18 levels in ovarian carcinomas and metastatic lesions were significantly higher than in normal tissues and cystadenomas. IHC results showed that expression of huMETCAM/MUC18 in normal tissues and cystadenomas was mostly absent from epithelial cells, but in carcinomas and metastatic lesions it was localized to epithelial cells. In higher pathological grades of ovarian cancer and metastatic lesions, the percentage of cells stained in IHC was increased. Thirty percent of normal tissues weakly expressed the huMETCAM/MUC18 antigen, but 70% of cancer tissues and 100% of metastatic lesions expressed the antigen. Expression levels of several downstream effectors of huMETCAM/MUC18, Bcl2, PCNA and VEGF, were elevated in cancerous tissues, however, not that of Bax. The phospho-AKT/AKT ratio was elevated in metastatic lesions.

CONCLUSION

Upexpression of huMETCAM/MUC18 may be a marker for the malignant potential of ovarian carcinomas. Progression of ovarian cancer may involve increased signaling in anti-apoptosis, proliferation, survival/proliferation pathway, and angiogenesis.

Prognostic value of melanoma cell adhesion molecule expression in cancers: a meta-analysis

Melanoma cell adhesion molecule (MACM) has been reported in many studies as a novel bio-marker for its prognosis value in cancers. But the prognosis significance of MACM expression in cancer remains inconclusive. Therefore, we conducted a system review and meta-analysis to assess its prognosis value in cancers. A systematic search through Pubmed, EMBASE and Cochran Library database was conducted. Hazard Ratios (HRs) and 95% confidence intervals (CIs) were used to evaluate the prognosis value of MACM expression. Eleven studies with 2657 cases were included after sorting out 462 articles for this meta-analysis. The results of the fixed-model depending on the heterogeneity in studies demonstrated that MACM expression was significantly associated with overall survival (OS) in cancer (HR=2.84, 95% CI: 1.10-7.31, P<0.00001). Furthermore, subgroup analysis indicated that high expressed MACM predicted a poor OS in both Asian (HR=2.52, 95% CI: 1.80-3.52, P<0.00001) and Caucasian (HR=2.40, 95% CI: 2.01-2.88, P<0.00001). In conclusion, high expression of MACM was significantly associated with a poor prognostic outcome in cancer. MACM can be regarded as a novel bio-marker in different types of cancers and can be used to evaluate the prognosis of therapeutic effect during clinical practices.

Expression of epithelial-mesenchymal transition-related markers in triple-negative breast cancer: ZEB1 as a potential biomarker for poor clinical outcome

Triple-negative breast cancer (TNBC) is a heterogeneous group of disease with a well-known association with epithelial-mesenchymal transition (EMT) and breast cancer stem cell phenotype. Recent studies have shown that TNBC can be classified into 6 subtypes, including basal-like, mesenchymal-like, and mesenchymal stem-like subtypes. However, clinical significance of the EMT in TNBC remains unclear. We analyzed immunohistochemical expression of EMT-related markers, including EMT markers (expression of vimentin, smooth muscle actin, osteonectin, and N-cadherin; loss of E-cadherin), EMT inducers (ZEB1 and CD146), and breast cancer stem cell markers (CD44(+)/CD24(-) and aldehyde dehydrogenase 1) in 173 TNBCs and correlated their expression with clinicopathological features of the tumors, including clinical outcome. Expressions of vimentin, CD44(+)/CD24(-), and CD146 were more frequent in basal-like TNBCs than non-basal-like TNBCs. Whereas CD146 expression was closely associated with the expression of various EMT markers and CD44(+)/CD24(-) phenotype, ZEB1 expression correlated only with the expression of smooth muscle actin. Expressions of vimentin, smooth muscle actin, osteonectin, and ZEB1 and loss of E-cadherin were more frequently found in metaplastic carcinomas than in other histologic subtypes. In survival analyses, EMT markers were not associated with patients' clinical outcomes. However, ZEB1 expression was found to be an independent prognostic factor for poor disease-free survival. These findings indicate that expression of EMT-related markers in TNBCs can be a signature of a certain subgroup of TNBC, which is associated with metaplastic carcinoma, and ZEB1 expression can serve as a potential biomarker to define a subgroup of TNBC associated with poor clinical outcomes.

Life is three dimensional-as in vitro cancer cultures should be

For many decades, fundamental cancer research has relied on two-dimensional in vitro cell culture models. However, these provide a poor representation of the complex three-dimensional (3D) architecture of living tissues. The more recent 3D culture systems, which range from ridged scaffolds to semiliquid gels, resemble their natural counterparts more closely. The arrangement of the cells in 3D systems allows better cell-cell interaction and facilitates extracellular matrix secretion, with concomitant effects on gene and protein expression and cellular behavior. Many studies have reported differences between 3D and 2D systems as regards responses to therapeutic agents and pivotal cellular processes such as cell differentiation, morphology, and signaling pathways, demonstrating the importance of 3D culturing for various cancer cell lines.

Significance of expression of human METCAM/MUC18 in nasopharyngeal carcinomas and metastatic lesions

Human METCAM/MUC18, a cell adhesion molecule (CAM) in the immunoglobulin-like gene super family, plays a dual role in the progression of several epithelium cancers; however, its role in the nasopharyngeal carcinoma (NPC) remains unclear. To initiate the study we determined human METCAM/MUC18 expression in tissue samples of normal nasopharynx (NP), NPCs, and metastatic lesions, and in two established NPC cell lines. Immunoblotting analysis was used for the determination in lysates of frozen tissues, and immunohistochemistry (IHC) for expression in formalin-fixed, paraffin-embedded tissue sections of 7 normal nasopharynx specimens, 94 NPC tissue specimens, and 3 metastatic lesions. Human METCAM/MUC18 was expressed in 100% of the normal NP, not expressed in 73% of NPC specimens (or expressed at very low levels in only about 27% of NPC specimens), and expressed again in all of the metastatic lesions. The level of human METCAM/MUC18 expression in NPC tissues was about one fifth of that in the normal NP and metastatic lesions. The low level of human METCAM/ MUC18 expression in NPC specimens was confirmed by a weak signal of RT-PCR amplification of the mRNA. Low expression levels of human METCAM/MUC18 in NPC tissues were also reflected in the seven established NPC cell lines. These findings provided the first evidence that diminished expression of human METCAM/MUC18 is an indicator for the emergence of NPC, but increased expression then occurs with metastatic progression, suggesting that huMETCAM/MUC18, perhaps similar to TGF-β, may be a tumor suppressor, but a metastasis promoter for NPC.

The H3K9 methyltransferase G9a is a marker of aggressive ovarian cancer that promotes peritoneal metastasis

BACKGROUND

Ovarian cancer (OCa) peritoneal metastasis is the leading cause of cancer-related deaths in women with limited therapeutic options available for treating it and poor prognosis, as the underlying mechanism is not fully understood.

METHOD

The clinicopathological correlation of G9a expression was assessed in tumor specimens of ovarian cancer patients. Knockdown or overexpression of G9a in ovarian cancer cell lines was analysed with regard to its effect on adhesion, migration, invasion and anoikis-resistance. In vivo biological functions of G9a were tested by i.p. xenograft ovarian cancer models. Microarray and quantitative RT-PCR were used to analyze G9a-regulated downstream target genes.

RESULTS

We found that the expression of histone methyltransferase G9a was highly correlated with late stage, high grade, and serous-type OCa. Higher G9a expression predicted a shorter survival in ovarian cancer patients. Furthermore, G9a expression was higher in metastatic lesions compared with their corresponding ovarian primary tumors. Knockdown of G9a expression suppressed prometastatic cellular activities including adhesion, migration, invasion and anoikis-resistance of ovarian cancer cell lines, while G9a over-expression promoted these cellular properties. G9a depletion significantly attenuated the development of ascites and tumor nodules in a peritoneal dissemination model. Importantly, microarray and quantitative RT-PCR analysis revealed that G9a regulates a cohort of tumor suppressor genes including CDH1, DUSP5, SPRY4, and PPP1R15A in ovarian cancer. Expression of these genes was also inversely correlated with G9a expression in OCa specimens.

CONCLUSION

We propose that G9a contributes to multiple steps of ovarian cancer metastasis and represents a novel target to combat this deadly disease.

Metastasis review: from bench to bedside

Cancer is the final result of uninhibited cell growth that involves an enormous group of associated diseases. One major aspect of cancer is when cells attack adjacent components of the body and spread to other organs, named metastasis, which is the major cause of cancer-related mortality. In developing this process, metastatic cells must successfully negotiate a series of complex steps, including dissociation, invasion, intravasation, extravasation, and dormancy regulated by various signaling pathways. In this review, we will focus on the recent studies and collect a comprehensive encyclopedia in molecular basis of metastasis, and then we will discuss some new potential therapeutics which target the metastasis pathways. Understanding the new aspects on molecular mechanisms and signaling pathways controlling tumor cell metastasis is critical for the development of therapeutic strategies for cancer patients that would be valuable for researchers in both fields of molecular and clinical oncology.

The mushroom Ganoderma lucidum suppresses breast-to-lung cancer metastasis through the inhibition of pro-invasive genes

Breast cancer metastasis is one of the major reasons for the high morbidity and mortality of breast cancer patients. In spite of surgical interventions, chemotherapy, radiation therapy and targeted therapy, some patients are considering alternative therapies with herbal/natural products. In the present study, we evaluated a well-characterized extract from the medicinal mushroom Ganoderma lucidum (GLE) for its affects on tumor growth and breast-to-lung cancer metastasis. MDA-MB-231 human breast cancer cells were implanted into the mammary fat pads of nude mice. GLE (100 mg/kg/every other day) was administered to the mice by an oral gavage for 4 weeks, and tumor size was measured using microcalipers. Lung metastases were evaluated by hematoxylin and eosin (H&E) staining. Gene expression in MDA-MB-231 cells was determined by DNA microarray analysis and confirmed by quantitative PCR. Identified genes were silenced by siRNA, and cell migration was determined in Boyden chambers and by wound-healing assay. Although an oral administration of GLE only slightly suppressed the growth of large tumors, the same treatment significantly inhibited the number of breast-to-lung cancer metastases. GLE also downregulated the expression of genes associated with invasive behavior (HRAS, VIL2, S100A4, MCAM, I2PP2A and FN1) in MDA-MB-231 cells. Gene silencing of HRAS, VIL2, S100A4, I2PP2A and FN1 by siRNA suppressed migration of MDA-MB‑231 cells. Our study suggests that an oral administration of GLE can inhibit breast-to-lung cancer metastases through the downregulation of genes responsible for cell invasiveness. The anti-metastatic benefits of GLE warrant further clinical studies.

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.

Cell adhesion molecules and their relation to (cancer) cell stemness

Despite decades of search for anticancer drugs targeting solid tumors, this group of diseases remains largely incurable, especially if in advanced, metastatic stage. In this review, we draw comparison between reprogramming and carcinogenesis, as well as between stem cells (SCs) and cancer stem cells (CSCs), focusing on changing garniture of adhesion molecules. Furthermore, we elaborate on the role of adhesion molecules in the regulation of (cancer) SCs division (symmetric or asymmetric), and in evolving interactions between CSCs and extracellular matrix. Among other aspects, we analyze the role and changes of expression of key adhesion molecules as cancer progresses and metastases develop. Here, the role of cadherins, integrins, as well as selected transcription factors like Twist and Snail is highlighted, not only in the regulation of epithelial-to-mesenchymal transition but also in the avoidance of anoikis. Finally, we briefly discuss recent developments and new strategies targeting CSCs, which focus on adhesion molecules or targeting tumor vasculature.

Masked selection: a straightforward and flexible approach for the selection of binders against specific epitopes and differentially expressed proteins by phage display

Phage display is a well-established procedure to isolate binders against a wide variety of antigens that can be performed on purified antigens, but also on intact cells. As selection steps are performed in vitro, it is possible to focus the outcome of the selection on relevant epitopes by performing some additional steps, such as depletion or competitive elutions. However in practice, the efficiency of these steps is often limited and can lead to inconsistent results. We have designed a new selection method named masked selection, based on the blockade of unwanted epitopes to favor the targeting of relevant ones. We demonstrate the efficiency and flexibility of this method by selecting single-domain antibodies against a specific portion of a fusion protein, by selecting binders against several members of the seven transmembrane receptor family using transfected HEK cells, or by selecting binders against unknown breast cancer markers not expressed on normal samples. The relevance of this approach for antibody-based therapies was further validated by the identification of four of these markers, Epithelial cell adhesion molecule, Transferrin receptor 1, Metastasis cell adhesion molecule, and Sushi containing domain 2, using immunoprecipitation and mass spectrometry. This new phage display strategy can be applied to any type of antibody fragments or alternative scaffolds, and is especially suited for the rapid discovery and identification of cell surface markers.

MCAM expression is associated with poor prognosis in non-small cell lung cancer

BACKGROUND

MCAM has been recently identified as a biomarker for epithelial-mesenchymal transition (EMT) and is potentially involved in metastasis of cancer. The current study aimed at investigating the expression of MCAM in non-small-cell lung cancer (NSCLC) and its clinico-pathological significance.

METHODS

A follow-up analysis was performed on 118 patients with NSCLC resected by lobectomy or pneumectomy with systematic lymph node dissection. All patients were followed for 6-60 months. Immunostaining of tissue sections from primary tumors and their lymph node metastasis was performed and evaluated using monoclonal antibody against MCAM, E-cadherin, and vimentin. Correlations were investigated between MCAM immunostaining in primary tumors and E-cadherin, vimentin immunostaining, lymph node metastasis, and survival.

RESULTS

MCAM protein expression was found in 46.61 % of squamous cell carcinomas and 37.47 % of adenocarcinomas; MCAM expression positively correlated with vimentin, but inversely with E-cadherin (both P values <0.05). There were significant correlations between the MCAM immunostaining score in primary tumors and in their lymph node metastasis (P = 0.03). According to the Kaplan-Meier survival estimate, the level of MCAM expression in primary tumors was a statistically significant prognostic factor (P < 0.05).

CONCLUSIONS

MCAM expression in surgically treated NSCLC is clearly associated with lymph node metastasis and poor prognosis.

The interaction between LYVE-1 with hyaluronan on the cell surface may play a role in the diversity of adhesion to cancer cells

Hyaluronan (HA), a simple disaccharide unit, can polymerize and is considered a primary component of the extracellular matrix, which has a wide range of biological functions. In recent years, HA was found on the surface of tumor cells. According to previous reports, differing HA content on the cell surface of tumor cells is closely related to lymph node metastases, but the mechanisms mediating this process remained unclear. This research intended to study the surface content of HA on tumor cells and analyze cell adhesive changes caused by the interaction between HA and its lymphatic endothelial receptor (LYVE-1). We screened and observed high HA content on HS-578T breast cells and low HA content on MCF-7 breast cells through particle exclusion, immunofluorescence and flow cytometry experiments. The expression of LYVE-1, the lymph-vessel specific HA receptor, was consistent with our previous report and enhanced the adhesion of HA^high-HS-578T cells to COS-7^LYVE-1(+) through HA in cell static adhesion and dynamic parallel plate flow chamber experiments. MCF-7 breast cells contain little HA on the surface; however, our results showed little adhesion difference between MCF-7 cells and COS-7^LYVE-1(+) and COS-7^LYVE-1(−) cells. Similar results were observed concerning the adhesion of HS-578T cells or MCF-7 cells to SVEC4-10 cells. Furthermore, we observed for the first time that the cell surface HA content of high transfer tumor cells was rich, and we visualized the cross-linking of HA cable structures, which may activate LYVE-1 on lymphatic endothelial cells, promoting tumor adhesion. In summary, high-low cell surface HA content of tumor cells through the interaction with LYVE-1 leads to adhesion differences.

CD146, a multi-functional molecule beyond adhesion

CD146 is a cell adhesion molecule (CAM) that is primarily expressed at the intercellular junction of endothelial cells. CD146 was originally identified as a tumor marker for melanoma (MCAM) due to its existence only in melanoma but not in the corresponding normal counterpart. However CD146 is not just a CAM for the inter-cellular and cell-matrix adhesion. Recent evidence indicates that CD146 is actively involved in miscellaneous processes, such as development, signaling transduction, cell migration, mesenchymal stem cells differentiation, angiogenesis and immune response. CD146 has increasingly become an important molecule, especially identified as a novel bio-marker for angiogenesis and for cancer. Here we have reviewed the dynamic research of CD146, particularly newly identified functions and the underlying mechanisms of CD146.

Concerted regulation of CD34 and CD105 accompanies mesenchymal stromal cell derivation from human adventitial stromal cell

Mesenchymal stromal cells (MSC) have been intensively studied for innovative therapeutic applications. MSC in vitro are characterized by plastic-adherent proliferation, their specific immunophenotype and multipotency, whereas MSC progenitors in vivo are described as perivascular cells. Whether MSC progenitors acquire in vitro MSC characteristics upon in vitro culture is still unclear. This question can be experimentally accessed by analyzing changes in cellular properties that occur during the early in vitro culture phase, the MSC derivation phase. Here, we examined dynamics in morphology, proliferation, and expression of surface markers used for MSC characterization (such as CD34, CD105, CD146, and CD271) in tight kinetics during the MSC derivation phase of adipose tissue-derived MSC (AT-MSC). Using multiparametric flow cytometry, we identified 3 major ex vivo stromal vascular cell subsets: CD34+ CD146-CD271(+/-) adventitial stromal cell-like cells (AdSC), CD34- CD146+ CD271(+/-) pericyte-like cells (PC), and CD34+ CD31+ CD146+ endothelial cells. Of these subsets, only AdSC, but not PC gave rise to MSC under MSC culture conditions. At day 4 of culture, AdSC became fibroblastoid and upregulated CD105, CD146, and CD271. Following this phenotypic transition, AdSC commenced proliferation and downregulated CD34. In our study, we demonstrate that AdSC are more clonogenic AT-MSC progenitors than PC. Moreover, we, for the first time have dissected the phenotypic transitions from MSC progenitors to in vitro MSC during the MSC derivation phase using multiparametric flow cytometry. Hence, we propose a model describing how de novo acquisition of the typical MSC morphology by AdSC is accompanied by concerted regulation of surface marker expression upon in vitro culture.

CD146 expression in human breast cancer cell lines induces phenotypic and functional changes observed in Epithelial to Mesenchymal Transition

BACKGROUND

Metastasis is an important step in tumor progression leading to a disseminated and often incurable disease. First steps of metastasis include down-regulation of cell adhesion molecules, alteration of cell polarity and reorganization of cytoskeleton, modifications associated with enhanced migratory properties and resistance of tumor cells to anoikis. Such modifications resemble Epithelial to Mesenchymal Transition (EMT). In breast cancer CD146 expression is associated with poor prognosis and enhanced motility.

METHODOLOGY/PRINCIPAL FINDINGS

On 4 different human breast cancer cell lines, we modified CD146 expression either with shRNA technology in CD146 positive cells or with stable transfection of CD146 in negative cells. Modifications in morphology, growth and migration were evaluated. Using Q-RT-PCR, we analyzed the expression of different EMT markers. We demonstrate that high levels of CD146 are associated with loss of cell-cell contacts, expression of EMT markers, increased cell motility and increased resistance to doxorubicin or docetaxel. Experimental modulation of CD146 expression induces changes consistent with the above described characteristics: morphology, motility, growth in anchorage independent conditions and Slug mRNA variations are strictly correlated with CD146 expression. These changes are associated with modifications of ER (estrogen receptor) and Erb receptors and are enhanced by simultaneous and opposite modulation of JAM-A, or exposure to heregulin, an erb-B4 ligand.

CONCLUSIONS

CD146 expression is associated with an EMT phenotype. Several molecules are affected by CD146 expression: direct or indirect signaling contributes to EMT by increasing Slug expression. CD146 may also interact with Erb signaling by modifying cell surface expression of ErbB3 and ErbB4 and increased resistance to chemotherapy. Antagonistic effects of JAM-A, a tight junction-associated protein, on CD146 promigratory effects underline the complexity of the adhesion molecules network in tumor cell migration and metastasis.

Dual Roles of METCAM in the Progression of Different Cancers

METCAM, an integral membrane cell adhesion molecule (CAM) in the Ig-like gene superfamily, is capable of performing typical functions of CAMs, such as mediating cell-cell and cell-extracellular interactions, crosstalk with intracellular signaling pathways, and modulating social behaviors of cells. METCAM is expressed in about nine normal cells/tissues. Aberrant expression of METCAM has been associated with the progression of several epithelial tumors. Further in vitro and in vivo studies show that METCAM plays a dual role in the progression of different tumors. It can promote the malignant progression of several tumors. On the other hand, it can suppress the malignant progression of other tumors. We suggest that the role of METCAM in the progression of different cancer types may be modulated by different intrinsic factors present in different cancer cells and also in different stromal microenvironment. Many possible mechanisms mediated by this CAM during early tumor development and metastasis are suggested.

Different expression of CD146 in human normal and osteosarcoma cell lines

The CD146 cell membrane adhesion molecule is highly expressed on the cell surface of several tumours. The level of its expression has been found to correlate directly with tumour progression and metastatic potential, thus establishing CD146 as an important candidate of tumour growth and metastasis. In order to characterize its expression in human osteosarcoma (OS) cell lines, we have examined the CD146 expression at protein and RNA levels in both normal and tumour osteoblast-like cell lines by several methods. Our results indicate that CD146 protein is expressed at low levels in normal osteoblast cells whereas it is highly expressed in all OS cell lines analysed, (SaOS, MG-63, U-2OS). Moreover, CD146 overexpression was partially reduced in shYY1 cells, where the Yin Yang 1 transcription factor, also found over-expressed in human OS cells, has been silenced.

The role of immunoglobulin superfamily cell adhesion molecules in cancer metastasis

Metastasis is a major clinical problem and results in a poor prognosis for most cancers. The metastatic pathway describes the process by which cancer cells give rise to a metastatic lesion in a new tissue or organ. It consists of interconnecting steps all of which must be successfully completed to result in a metastasis. Cell-cell adhesion is a key aspect of many of these steps. Adhesion molecules belonging to the immunoglobulin superfamily (Ig-SF) commonly play a central role in cell-cell adhesion, and a number of these molecules have been associated with cancer progression and a metastatic phenotype. Surprisingly, the contribution of Ig-SF members to metastasis has not received the attention afforded other cell adhesion molecules (CAMs) such as the integrins. Here we examine the steps in the metastatic pathway focusing on how the Ig-SF members, melanoma cell adhesion molecule (MCAM), L1CAM, neural CAM (NCAM), leukocyte CAM (ALCAM), intercellular CAM-1 (ICAM-1) and platelet endothelial CAM-1 (PECAM-1) could play a role. Although much remains to be understood, this review aims to raise the profile of Ig-SF members in metastasis formation and prompt further research that could lead to useful clinical outcomes.

METCAM/MUC18 augments migration, invasion, and tumorigenicity of human breast cancer SK-BR-3 cells

Previous research has identified METCAM/MUC18, an integral membrane cell adhesion molecule (CAM) in the Ig-like gene super-family, as a promoter or a suppressor in the development of human breast cancer by MCF7, MDA-MB-231, and MDA-MB-468. To resolve these conflicting results we have investigated the role of this CAM in the progression of the three aforementioned cell lines plus one additional human breast cancer cell line, SK-BR-3. We transfected the SK-BR-3 cells with human METCAM/MUC18 cDNA to obtain G418-resistant clones, which expressed different levels of the protein and which were used to test the effect of human METCAM/MUC18 expression on in vitro motility, invasiveness, anchorage-independent colony formation in soft agar, disorganized growth in a 3D basement membrane culture assay, and in vivo tumorigenesis in athymic nude mice. Enforced METCAM/MUC18 expression increased in vitro motility, invasiveness, and anchorage-independent colony formation of SK-BR-3 cells and favored disorganized growth of the cells in 3D basement membrane culture. Enforced expression also increased tumorigenicity and final tumor weights of SK-BR-3 clones/cells after subcutaneous injection of the cells under the left third nipple of female athymic nude mice. To understand the mechanisms, we also determined the expression of several downstream key effectors in the tumors. Tumor cells from METCAM/MUC18 expressing clones exhibited elevated expression of an anti-apoptotic and survival index (Bcl2), an aerobic glycolysis index (LDH-A), and pro-angiogenesis indexes (VEGF and VAGFR2). We concluded that human METCAM/MUC18 promotes the development of breast cancer cells by increasing an anti-apoptosis and survival pathway and augmenting aerobic glycolysis and angiogenesis.