MUC18, a member of the immunoglobulin superfamily, is expressed on bone marrow fibroblasts and a subset of hematological malignancies

Unveiling heterogeneity in MSCs: exploring marker-based strategies for defining MSC subpopulations

Mesenchymal stem/stromal cells (MSCs) represent a heterogeneous cell population distributed throughout various tissues, demonstrating remarkable adaptability to microenvironmental cues and holding immense promise for disease treatment. However, the inherent diversity within MSCs often leads to variability in therapeutic outcomes, posing challenges for clinical applications. To address this heterogeneity, purification of MSC subpopulations through marker-based isolation has emerged as a promising approach to ensure consistent therapeutic efficacy. In this review, we discussed the reported markers of MSCs, encompassing those developed through candidate marker strategies and high-throughput approaches, with the aim of explore viable strategies for addressing the heterogeneity of MSCs and illuminate prospective research directions in this field.

CD146 promotes malignant progression of breast phyllodes tumor through suppressing DCBLD2 degradation and activating the AKT pathway

BACKGROUND

As a rapid-progressing tumor, breast malignant phyllodes tumors (PTs) are challenged by the lack of effective therapeutic strategies and suitable prognostic markers. This study aimed to clarify the role and mechanism of CD146 on promoting PTs malignant progression, and to identify a novel prognosis marker and treatment target of breast malignant PTs.

METHODS

The expression and prognostic significance of CD146 in PTs was detected through single-cell RNA-sequencing (scRNA-seq), immunostaining, real-time PCR and other methodologies. Functional experiments including proliferation assay, colony formation assay, transwell assay, and collagen contraction assay were conducted to validate the role of CD146 in malignant progression of PTs. The efficacy of anti-CD146 monoclonal antibody AA98 against malignant PTs was corroborated by a malignant PT organoid model and a PT patient-derived xenograft (PDX) model. Transcriptome sequencing, proteomic analysis, co-immunoprecipitation, and pull-down assay was employed to identify the modulating pathway and additional molecular mechanism.

RESULTS

In this study, the scRNA-seq analysis of PTs disclosed a CD146-positive characteristic in the α-SMA+ fibroblast subset. Furthermore, a progressive elevation in the level of CD146 was observed with the malignant progression of PTs. More importantly, CD146 was found to serve as an independent predictor for recurrence in PT patients. Furthermore, CD146 was found to augment the viability and invasion of PTs. Mechanistically, CD146 acted as a protective "shield" to prevent the degradation of Discoidin, CUB, and LCCL domain-containing protein 2 (DCBLD2), thereby activating the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway and enhancing malignant behaviors of PT cells. In the malignant PT organoid and PDX model, a significant suppression of malignant PT growth was observed after the application of AA98.

CONCLUSIONS

These findings suggested that CD146 served as an efficacious marker for predicting PT malignant progression and showed promise as a prognosis marker and treatment target of breast malignant PTs. The study further unveiled the essential role of the CD146-DCBLD2/PI3K/AKT axis in the malignant progression of PTs.

Analysis of Circulating Tumour Cells in Early-Stage Uveal Melanoma: Evaluation of Tumour Marker Expression to Increase Capture

(1) Background: The stratification of uveal melanoma (UM) patients into prognostic groups is critical for patient management and for directing patients towards clinical trials. Current classification is based on clinicopathological and molecular features of the tumour. Analysis of circulating tumour cells (CTCs) has been proposed as a tool to avoid invasive biopsy of the primary tumour. However, the clinical utility of such liquid biopsy depends on the detection rate of CTCs. (2) Methods: The expression of melanoma, melanocyte, and stem cell markers was tested in a primary tissue microarray (TMA) and UM cell lines. Markers found to be highly expressed in primary UM were used to either immunomagnetically isolate or immunostain UM CTCs prior to treatment of the primary lesion. (3) Results: TMA and cell lines had heterogeneous expression of common melanoma, melanocyte, and stem cell markers. A multi-marker panel of immunomagnetic beads enabled isolation of CTCs in 37/43 (86%) patients with UM. Detection of three or more CTCs using the multi-marker panel, but not MCSP alone, was a significant predictor of shorter progression free (p = 0.040) and overall (p = 0.022) survival. (4) Conclusions: The multi-marker immunomagnetic isolation protocol enabled the detection of CTCs in most primary UM patients. Overall, our results suggest that a multi-marker approach could be a powerful tool for CTC separation for non-invasive prognostication of UM.

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.

A Method to Isolate, Purify, and Characterize Human Periodontal Ligament Stem Cells

Human periodontal ligament stem cells (PDLSCs) are a unique population of mesenchymal stem cells (MSCs) that demonstrate the capacity to generate cementum- and periodontal ligament-like structures in vivo. As such, PDLSCs represent a promising cell-based therapy in reconstructive dentistry for the treatment of periodontal disease. The present chapter describes two methods for isolating PDLSCs from human PDL tissue including traditional plastic adherence, and immunomagnetic selection based on the expression of MSC-associated surface markers STRO-1 antigen, CD146 (MUC-18), CD29 (Integrin β-1), CD44, and CD106 (VCAM-1). Although no single antibody demonstrates specificity for MSCs, isolation based on expression of individual markers results in homogenous preparations of PDLSCs. Methods to further characterize the immunophenotype and multipotent capacity of PDLSCs to differentiate into adipocytes, osteoblast-, and cementoblast-like cells in vitro, and cementum- and periodontal ligament-like tissues in vivo, are also described.

Expression of the immunoglobulin superfamily cell membrane adhesion molecule Cd146 in acute leukemia

BACKGROUND

The expression of the immunoglobulin superfamily cell membrane adhesion molecule CD146 has been reported on several normal and pathological cell types in human. The aim of this study was to investigate CD146 expression in acute leukemia using a multiparametric cytofluorimetric approach.

METHODS

Cytofluorimetric and cytogenetic studies were performed on peripheral blood and bone marrow samples from 162 patients with acute myeloid leukemia (AML, n = 121) and acute lymphoblastic leukemia (ALL, n = 41). ALL patients were subdivided in B-ALL (n = 38) and T-ALL (n = 3). Adult (n = 18) and pediatric (n = 20) B-ALL were considered as a whole group.

RESULTS

Four out of 121 (3.3%) AML cases, 14/38 (36.8%) B-ALL, and 2/3 (66.6%) T-ALL expressed CD146 on 12-98% of blasts (p < 0.001). CD146 expression was not observed in 10 healthy controls. Among B-ALL CD146-positive cases, 78.6% were associated with a "common"/BII-ALL and 21.4% with a pre-B/BIII-ALL immunophenotype while pro-B/BI-ALL and mature-B/BIV-ALL cases were CD146-negative. Statistical analysis showed CD146 expression strongly associated with Ph+ positivity in B-ALL with the highest percentage of CD146-positive blasts in all Ph-positive B-ALL cases (84 ± 22% Ph-positive B-ALL SD vs. 40 ± 24% SD in Ph-negative B-ALL; p < 0,001).

CONCLUSION

In our series, CD146 was expressed in all cases of Ph-positive B-ALL and in the vast majority of T-ALL, whereas it was rarely expressed by AML blasts. We suggest that CD146 may be considered as an additional marker for acute lymphoblastic leukemia diagnosis and monitoring of minimal residual disease in those cases which are CD146-positive at diagnosis. © 2015 International Clinical Cytometry Society.

CD146 as a new marker for an increased chondroprogenitor cell sub-population in the later stages of osteoarthritis

Cartilage-derived mesenchymal stem cells (MSCs) have been isolated with different methods. In this study lateral and medial femoral condyles were respectively collected from patients with late-stage osteoarthritis during the total knee arthroplasty. After digestion of the cartilage tissues with type II collagenase and analysis by fluorescence-activated cell sorting (FACS) with CD146, a chondroprogenitor cell sub-population were isolated and purified. The expression of other MSC-associated markers in the CD146+ chondroprogenitors was analyzed by flow cytometry. Multi-lineage differentiation capacity of CD146+ chondroprogenitors was compared with that of unsorted chondrocytes and adipose-derived MSCs (ADMSCs). Higher percentage of CD146+ chondroprogenitors isolated from the medial femoral condyles was observed than that from the lateral. CD146+ chondroprogenitors expressed high levels of MSC-specific surface antigens, and showed higher chondrogenesis capacity than ADMSCs and unsorted chondrocytes in a 3D cell pellet culture model. Thus CD146 might be a new cell surface marker for cartilage progenitor cell population in the late-stage osteoarthritis.

"Mesenchymal" stem cells

Two opposing descriptions of so-called mesenchymal stem cells (MSCs) exist at this time. One sees MSCs as the postnatal, self-renewing, and multipotent stem cells for the skeleton. This cell coincides with a specific type of bone marrow perivascular cell. In skeletal physiology, this skeletal stem cell is pivotal to the growth and lifelong turnover of bone and to its native regeneration capacity. In hematopoietic physiology, its role as a key player in maintaining hematopoietic stem cells in their niche and in regulating the hematopoietic microenvironment is emerging. In the alternative description, MSCs are ubiquitous in connective tissues and are defined by in vitro characteristics and by their use in therapy, which rests on their ability to modulate the function of host tissues rather than on stem cell properties. Here, I discuss how the two views developed, conceptually and experimentally, and attempt to clarify the confusion arising from their collision.

Differentiation of iPSC to Mesenchymal Stem-Like Cells and Their Characterization

Mesenchymal stem cells (MSC) are a unique population of adult stem cells that have the capacity to differentiate into numerous cell types as well as the ability to modulate the immune system. As such, MSC represent a promising stem cell population for use in the clinical treatment of a range of disorders involving tissue regeneration as well as the immune system. The lack of accessibility to MSC is currently limiting the use of MSC in mainstream clinical treatment strategies. It is therefore imperative for the future success of stem cell-based treatment approaches that are more reliable, and accessible sources of MSC are identified. The present chapter describes a method for generating MSC-like cells from induced pluripotent stem cells (iPSC), with equivalent growth and functional properties to parental MSC populations.

CD146 expression on mesenchymal stem cells is associated with their vascular smooth muscle commitment

Bone marrow mesenchymal stem cells (MSCs) are plastic adherent cells that can differentiate into various tissue lineages, including osteoblasts, adipocytes and chondrocytes. However, this progenitor property is not shared by all cells within the MSC population. In addition, MSCs vary in their proliferation capacity and expression of markers. Because of heterogeneity of CD146 expression in the MSC population, we compared CD146^−/Low and CD146^High cells under clonal conditions and after sorting of the non-clonal cell population to determine whether this expression is associated with specific functions. CD146^−/Low and CD146^High bone marrow MSCs did not differ in colony-forming unit-fibroblast number, osteogenic, adipogenic and chondrogenic differentiation or in vitro haematopoietic-supportive activity. However, CD146^−/Low clones proliferated slightly but significantly faster than did CD146^High clones. In addition, a strong expression of CD146 molecule was associated with a commitment to a vascular smooth muscle cell (VSMC) lineage characterized by a strong up-regulation of calponin-1 and SM22α expression and an ability to contract collagen matrix. Thus, within a bone marrow MSC population, certain subpopulations characterized by high expression of CD146, are committed towards a VSMC lineage.

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.

Optimization and scale-up culture of human endometrial multipotent mesenchymal stromal cells: potential for clinical application

We have previously identified and purified multipotent mesenchymal stromal cell (MSC)-like cells in the highly regenerative endometrial lining of the human uterus (eMSC) as CD140b⁺CD146⁺ cells. Due to ease of accessibility with minimal morbidity via biopsy, we are proposing to use eMSC in cell-based therapies; however, culture conditions compliant with Good Manufacturing Practice have not been established for eMSC. The aim of this study was to optimize serum-free and xeno-free culture conditions for expansion of eMSC for potential clinical use. Real-time cell assessment (Xcelligence) and MTS viability assays were used to measure attachment and proliferation of freshly isolated, flow cytometry-sorted CD140b⁺CD146⁺ eMSC cultured in several commercially available and in-house serum-free and xeno-free media in combination with five attachment matrices (fibronectin, collagen, gelatin, laminin, and Cell Start-XF®). Comparisons were made with a standard serum-containing medium, DMEM/F-12/10% fetal bovine serum. Under all conditions examined, eMSC attachment and proliferation was greatest using a fibronectin matrix, with Lonza TP-SF® and our in-house DMEM/SF/FGF2/EGF serum-free xeno-product-containing medium similar to serum-containing medium. Hypoxia increased eMSC proliferation in the DMEM/SF/FGF2/EGF serum-free medium. Culture of eMSC for 7 days on a fibronectin matrix in DMEM/SF/FGF2/EGF serum-free media in 5% O₂ maintained greater numbers of undifferentiated eMSC expressing CD140b, CD146, and W5C5 compared to culture under similar conditions in Lonza TP-SF medium. However, the percentage of cells expressing typical MSC phenotypic markers, CD29, CD44, CD73, and CD105, were similar for both media. EMSC showed greater expansion in 2D compared to 3D culture on fibronectin-coated microbeads using the optimized DMEM/SF/FGF2/EGF medium in 5% O₂. In the optimized 2D culture conditions, eMSC retained CFU activity, multipotency, and MSC surface phenotype, representing the first steps in their preparation for potential clinical use.

MCAM is a novel metastasis marker and regulates spreading, apoptosis and invasion of ovarian cancer cells

Melanoma cell adhesion molecule (MCAM) is a cell adhesion molecule that is abnormally expressed in a variety of tumours and is closely associated with tumour metastasis. The role of MCAM in ovarian cancer development has not been fully studied. In this study, through immunohistochemical staining of ovarian cancer tissue samples and RNA interference to silence MCAM in ovarian cancer cells, we examined the impact of MCAM on the biological functions of ovarian cancer cells and attempted to reveal the role of MCAM in ovarian cancer development. Our results showed that MCAM expression was particularly high in metastatic ovarian cancers compared with other pathological types of ovarian epithelial tissues. After MCAM silencing in the MCAM high-expression ovarian cancer cell line SKOV-3, the cell apoptosis was increased, whereas the cell spreading and invasion were significantly reduced, which may be related with dysregulation of small RhoGTPase (RhoA and Cdc42).These results suggest that MCAM expression in ovarian cancer is highly correlated with the metastatic potential of the cancer. MCAM is likely to participate in the regulation of the Rho signalling pathway to protect ovarian cancer cells from apoptosis and promote their malignant invasion and metastasis. Therefore, MCAM can be used not only as a molecular marker to determine the prognosis of ovarian cancer but also as a therapeutic target in metastatic ovarian cancer.

Study on Culture of Human Dental Pulp Stem Cells to Apply in Tissue Engineering

Dental pulp cell research might open a promising application in tooth tissue regeneration. The aim of this study is to establish a protocol for in vitro culture the human dental pulp stem cells to apply in tissue engineering. Human premolar and impacted third molars were collected and disinfected. Dental pulp fragments were cultured with Dulbecco's Modified Eagle Medium: Nutrient Mixture F-12 (DMEM/F12) medium supplemented with 10% Fetal Bovine Serum (FBS). Dental pulp stem cells (DPSCs) were identified using proliferation assay, RT-PCR and flow cytometry. Growth of DPSCs on dentin surface was assessed by MTT assay. The study showed that we successfully isolated, cultured and characterized dental pulp cells by outgrowth method. Cultured population of cells expressed in high level of Oct4, CD146, CD90, CD44. DPSCs proliferated on chemically and mechanically treated dentin surface. This research provides important information and a basis for further investigations to establish dental tissue engineering protocols.

Multi-composite bioactive osteogenic sponges featuring mesenchymal stem cells, platelet-rich plasma, nanoporous silicon enclosures, and Peptide amphiphiles for rapid bone regeneration

A novel bioactive sponge was created with a composite of type I collagen sponges or porous poly(ε-caprolactone) (PCL) scaffolds, platelet-rich plasma (PRP), BMP2-loaded nanoporous silicon enclosure (NSE) microparticles, mineralizing peptide amphiphiles (PA), and mesenchymal stem cells (MSC). Primary MSC from cortical bone (CB) tissue proved to form more and larger colony units, as well as produce more mineral matrix under osteogenic differentiation, than MSC from bone marrow (BM). Coating pre-treatments were optimized for maximum cell adhesion and mineralization, while a PRP-based gel carrier was created to efficiently deliver and retain MSC and microparticles within a porous scaffold while simultaneously promoting cell recruitment, proliferation, and angiogenesis. Components and composite sponges were evaluated for osteogenic differentiation in vitro. Osteogenic sponges were loaded with MSC, PRP, PA, and NSE and implanted subcutaneously in rats to evaluate the formation of bone tissue and angiogenesis in vivo. It was found that the combination of a collagen sponge with CB MSC, PRP, PA, and the BMP2-releasing NSE formed the most bone and was most vascularized by four weeks compared to analogous composites featuring BM MSC or PCL or lacking PRP, PA, and NSE. This study indicates that CB MSC should be considered as an alternative to marrow as a source of stem cells, while the PRP-PA cell and microparticle delivery system may be utilized for diverse tissue engineering applications.

IGFBP-4 activates the Wnt/beta-catenin signaling pathway and induces M-CAM expression in human renal cell carcinoma

The Wnt/β-catenin signaling pathway is inactivated by Wnt antagonists in most cancers and IGFBP-4 is an antagonist of the Wnt/ β-catenin signaling pathway. However, the function of IGFBP-4 is not currently understood in renal cell carcinoma (RCC). We initially found that the expression of IGFBP-4 was significantly lower in primary RCC and higher in metastatic RCC compared to normal human kidney tissues. To assess the function of IGFBP4, we established IGFBP4 transfectants (primary renal cancer cell line) and performed functional analyses including Tcf reporter assays, cell viability, invasive capability, mortality, and in vivo tumor growth. Interestingly IGFBP-4 transfectants promoted cell growth (in vitro and in vivo), invasion, and motility in primary renal cancer. Tcf transcriptional activity was significantly increased in IGFBP-4 transfectants compared to mock cells and β-catenin expression was increased. Also the β-catenin downstream effector, MT1-MMP showed increased expression in IGFBP4 transfectants. Additionally IGFBP4 induced the expression of M-CAM, a marker of tumor progression. In order to assess the role of IGFBP4 in metastatic renal cancer, IGFBP-4 mRNA in a metastatic renal cancer cell lines (ACHN) was knocked-down using a siRNA technique. The cell growth and motility was decreased in si-IGFBP4 transfected ACHN cells compared to cells transfected with control siRNA. Tcf activity in ACHN cells was also decreased with si-IGFBP-4 transfection. This is a first report documenting that IGFBP-4 expression in RCC activates cell growth, metastasis, Wnt/beta-catenin signaling and may be involved in RCC metastasis.

Mesenchymal Stem Cells

Stem cells have two features: the ability to differentiate along different lineages and the ability of self-renewal. Two major types of stem cells have been described, namely, embryonic stem cells and adult stem cells. Embryonic stem cells (ESC) are obtained from the inner cell mass of the blastocyst and are associated with tumorigenesis, and the use of human ESCs involves ethical and legal considerations. The use of adult mesenchymal stem cells is less problematic with regard to these issues. Mesenchymal stem cells (MSCs) are stromal cells that have the ability to self-renew and also exhibit multilineage differentiation. MSCs can be isolated from a variety of tissues, such as umbilical cord, endometrial polyps, menses blood, bone marrow, adipose tissue, etc. This is because the ease of harvest and quantity obtained make these sources most practical for experimental and possible clinical applications. Recently, MSCs have been found in new sources, such as menstrual blood and endometrium. There are likely more sources of MSCs waiting to be discovered, and MSCs may be a good candidate for future experimental or clinical applications. One of the major challenges is to elucidate the mechanisms of differentiation, mobilization, and homing of MSCs, which are highly complex. The multipotent properties of MSCs make them an attractive choice for possible development of clinical applications. Future studies should explore the role of MSCs in differentiation, transplantation, and immune response in various diseases.

Methods for the purification and characterization of human adipose-derived stem cells

Peripheral adipose tissue contains a population of clonogenic precursor cells referred to as adipose-derived stem cells (ASC) that retain the capacity to differentiate into multiple cell types including osteoblasts, adipocytes, chondrocytes, myocytes, and neuronal cells following ex vivo expansion. Recent studies have demonstrated that ASC are most likely derived from a perivascular niche within highly vascularised fat tissue, analogous to different mesenchymal cell populations identified in other tissues throughout the body. The following chapter describes techniques to prospectively isolate clonogenic ASC from adult human adipose tissue using antibodies directed against perivascular markers and methods to immunophenotypically characterize their ex vivo expanded progeny.

A method to isolate, purify, and characterize human periodontal ligament stem cells

Human periodontal ligament stem cells (PDLSCs) are a unique population of mesenchymal stem cells (MSCs) which demonstrate the capacity to generate cementum- and periodontal ligament-like structures in vivo. As such, PDLSCs represent a promising cell-based therapy in reconstructive dentistry for the treatment of periodontal disease. The present chapter describes two methods for isolating PDLSCs from human PDL tissue including traditional plastic adherence and immunomagnetic selection based on the expression of MSC-associated surface markers STRO-1 antigen, CD146 (MUC-18), CD29 (integrin beta-1), CD44, and CD106 (VCAM-1). Although no single antibody demonstrates specificity for MSCs, isolation based on the expression of individual markers results in homogeneous preparations of PDLSCs. Methods to further characterize the immunophenotype and multipotent capacity of PDLSCs to differentiate into adipocytes, osteoblast- and cementoblast-like cells in vitro, and cementum- and periodontal ligament-like tissues in vivo are also described.

Dental tissue regeneration - a mini-review

BACKGROUND

with today's 21st century technological advancements, it is expected that individuals will either retain their natural teeth or obtain functional tooth replacements throughout their entire life. Modern dental therapies for the replacement of missing teeth largely utilize partial or complete dentures and titanium implants capped with prosthetic crowns. Although these prostheses serve a purpose, they are not equivalent, neither in function nor aesthetics, to natural teeth. Recent progress in dental tissue engineering has lent significant credibility to the concept that biological replacement teeth therapies may soon be available to replace missing teeth.

OBJECTIVE

in this review, we summarize the emerging concepts of whole-tooth replacement strategies, using postnatal dental stem cells (DSCs) and dental tissue engineering approaches.

METHODS

we provide a thorough and extensive review of the literature.

RESULTS

current approaches to achieve clinically relevant biological replacement tooth therapies rely on the cultivation of DSCs capable of relaying odontogenic induction signals, through dental epithelial-mesenchymal cell interactions. DSC expansion and differentiation can be achieved by programming progenitor stem cells to adopt dental lineages, using instructive, bioengineered scaffold materials. Periodontal ligament regeneration in particular has demonstrated significant progress recently, despite the somewhat unpredictable clinical outcomes, with regard to its capacity to augment conventional metallic dental implants and as an important component for whole-tooth tissue engineering. Following recent advances made in DSC and tissue engineering research, various research groups are in the midst of performing 'proof of principle' experiments for whole-tooth regeneration, with associated functional periodontal tissues. This mini-review focuses on recent and promising developments in the fields of pulp and periodontal tissue DSCs that are of particular relevance for dental tissue and whole-tooth regeneration.

CONCLUSION

continued advances in the derivation of useable DSC populations and optimally designed scaffold materials unequivocally support the feasibility of dental tissue and whole-tooth tissue engineering.

Heat shock protein-90 beta is expressed at the surface of multipotential mesenchymal precursor cells: generation of a novel monoclonal antibody, STRO-4, with specificity for mesenchymal precursor cells from human and ovine tissues

Mesenchymal stromal cells (MSCs) and their precursor cells (MPCs) can proliferate and differentiate into multiple mesodermal and some ectodermal and endodermal tissues. Culture-expanded MSCs are currently being evaluated as a possible cell therapy to replace/repair injured or diseased tissues. While a number of mAb reagents with specificity to human MSCs, including STRO-1, STRO-3 (BLK ALP), CD71 (SH2, SH3), CD106 (VCAM-1), CD166, and CD271, have facilitated the isolation of purified populations of human MSCs from primary tissues, few if any mAb reagents have been described that can be used to isolate equivalent cells from other species. This is of particular relevance when assessing the tissue regenerative efficacy of MSCs in large immunocompetent, preclinical animal models of disease. In light of this, we sought to generate novel monoclonal antibodies (mAb) with specific reactivity against a cell surface molecule that is expressed at high levels by MSCs from different species. Using CD106 (VCAM-1)-selected ovine MSCs as an immunogen, mAb-producing hybridomas were selected for their reactivity to both human and ovine MSCs. One such hybridoma, termed STRO-4, produced an IgG mAb that reacted with <5% of human and ovine bone marrow (BM) mononuclear cells. As a single selection reagent, STRO-4 mAb was able to enrich colony-forming fibroblasts (CFU-F) in both human and ovine BM by 16- and 8-folds, respectively. Cells isolated with STRO-4 exhibited reactivity with markers commonly associated with MSCs isolated by plastic adherence including CD29, CD44, and CD166. Moreover, when placed in inductive culture conditions in vitro, STRO-4(+) MSCs exhibited multilineage differentiation potential and were capable of forming a mineralized matrix, lipid-filled adipocytes, and chondrocytes capable of forming a glycosaminoglycan-rich matrix. Biochemical analysis revealed that STRO-4 identified the beta isoform of heat shock protein-90 (Hsp90beta). In addition to identifying an antibody reagent that identifies a highly conserved epitope expressed by MSCs from different species, our study also points to a potential role for Hsp90beta in MSC biology.

Mesenchymal Stem Cell Therapy for Nonmusculoskeletal Diseases: Emerging Applications

Mesenchymal stem cells are stem/progenitor cells originated from the mesoderm and can different into multiple cell types of the musculoskeletal system. The vast differentiation potential and the relative ease for culture expansion have established mesenchymal stem cells as the building blocks in cell therapy and tissue engineering applications for a variety of musculoskeletal diseases, including repair of fractures and bone defects, cartilage regeneration, treatment of osteonecrosis of the femoral head, and correction of genetic diseases such as osteogenesis imperfect. However, research in the past decade has revealed differentiation potentials of mesenchymal stem cells beyond lineages of the mesoderm, suggesting broader applications than originally perceived. In this article, we review the recent developments in mesenchymal stem cell research with respect to their emerging properties and applications in nonmusculoskeletal diseases.

Trafficking and differentiation of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are a heterogeneous population of stem/progenitor cells with pluripotent capacity to differentiate into mesodermal and non-mesodermal cell lineages, including osteocytes, adipocytes, chondrocytes, myocytes, cardiomyocytes, fibroblasts, myofibroblasts, epithelial cells, and neurons. MSCs reside primarily in the bone marrow, but also exist in other sites such as adipose tissue, peripheral blood, cord blood, liver, and fetal tissues. When stimulated by specific signals, these cells can be released from their niche in the bone marrow into circulation and recruited to the target tissues where they undergo in situ differentiation and contribute to tissue regeneration and homeostasis. Several characteristics of MSCs, such as the potential to differentiate into multiple lineages and the ability to be expanded ex vivo while retaining their original lineage differentiation commitment, make these cells very interesting targets for potential therapeutic use in regenerative medicine and tissue engineering. The feasibility for transplantation of primary or engineered MSCs as cell-based therapy has been demonstrated. In this review, we summarize the current knowledge on the signals that control trafficking and differentiation of MSCs.

Characterisation and developmental potential of ovine bone marrow derived mesenchymal stem cells

Since discovery, significant interest has been generated in the potential application of mesenchymal stem cells or multipotential stromal cells (MSC) for tissue regeneration and repair, due to their proliferative and multipotential capabilities. Although the sheep is often used as a large animal model for translating potential therapies for musculoskeletal injury and repair, the characteristics of MSC from ovine bone marrow have been inadequately described. Histological and gene expression studies have previously shown that ovine MSC share similar properties with human and rodents MSC, including their capacity for clonogenic growth and multiple stromal lineage differentiation. In the present study, ovine bone marrow derived MSCs positively express cell surface markers associated with MSC such as CD29, CD44 and CD166, and lacked expression of CD14, CD31 and CD45. Under serum-deprived conditions, proliferation of MSC occurred in response to EGF, PDGF, FGF-2, IGF-1 and most significantly TGF-alpha. While subcutaneous transplantation of ovine MSC in association with a ceramic HA/TCP carrier into immunocomprimised mice resulted in ectopic osteogenesis, adipogenesis and haematopoietic-support activity, transplantation of these cells within a gelatin sponge displayed partial chondrogenesis. The comprehensive characterisation of ovine MSC described herein provides important information for future translational studies involving ovine MSC.

Towards understanding the mode of action of the multifaceted cell adhesion receptor CD146

CD146, also known as melanoma cell adhesion molecule or MCAM, is a key cell adhesion protein in vascular endothelial cell activity and angiogenesis. CD146 promotes tumor progression of many cancers including melanoma and prostate. Strikingly, its expression is frequently lost in breast carcinoma cells, and it may act as a suppressor of breast cancer progression. While upstream mechanisms regulating CD146 are well documented, our understanding of the downstream molecular events underlying its mode of action remains to be elucidated. This review aims to focus on the progress in understanding the signaling mechanisms and the functional relevance of CD146, a multifaceted molecule, in cancer with particular emphasis on its role in inhibiting breast cancer progression.

The therapeutic applications of multipotential mesenchymal/stromal stem cells in skeletal tissue repair

Four decades after the first isolation and characterization of clonogenic bone marrow stromal cells or mesenchymal stem cells (MSC) in the laboratory of Dr. Alexander Friedenstien, the therapeutic application of their progeny following ex vivo expansion are only now starting to be realized in the clinic. The multipotency, paracrine effects, and immune-modulatory properties of MSC present them as an ideal stem cell candidate for tissue engineering and regenerative medicine. In recent years it has come to light that MSC encompass plasticity that extends beyond the conventional bone, adipose, cartilage, and other skeletal structures, and has expanded to the differentiation of liver, kidney, muscle, skin, neural, and cardiac cell lineages. This review will specifically focus on the skeletal regenerative capacity of bone marrow derived MSC alone or in combination with growth factors, biocompatible scaffolds, and following genetic modification.

A microarray approach to the identification of polyurethanes for the isolation of human skeletal progenitor cells and augmentation of skeletal cell growth

The present study has examined the efficacy of a polymer microarray platform to screen a library of polyurethanes for applications such as human skeletal progenitor cell isolation and surface modification of tissue engineering scaffolds to enhance skeletal cell growth and differentiation. Analysis of polyurethane microarrays incubated with adult human bone marrow-derived STRO-1+ skeletal progenitor cells identified 31 polyurethanes (from the entire library of 120 polyurethanes) capable of binding to the STRO-1+ cells. Four polyurethanes (out of the 31 identified in the previous screen) were able to selectively immobilise cells of the STRO-1+ fraction from the heterogeneous human bone marrow mononuclear cell population. These four polyurethanes were highly selective for the STRO-1+ fraction of human bone marrow as they failed to bind STRO-1+ immature osteoblast-like MG63 cells, the STRO-1+ fraction of human fetal skeletal cells and differentiated osteoblast-like SaOs cells. Culture of human bone marrow-derived STRO-1+ cells on fibres of Polyglycolic acid (PGA) fleece surface modified by polyurethane adsorption, in osteogenic conditions, enhanced the expression of early osteogenic genes. Similarly, surface modification of PGA fleece fibres by polyurethane adsorption increased the responsiveness of MG63 cells, cultured on this scaffold, to 1,25 dihydroxy Vitamin D3, as demonstrated by enhanced Osteocalcin expression.

A subset of host B lymphocytes controls melanoma metastasis through a melanoma cell adhesion molecule/MUC18-dependent interaction: evidence from mice and humans

Host immunity affects tumor metastasis but the corresponding cellular and molecular mechanisms are not entirely clear. Here, we show that a subset of B lymphocytes (termed B-1 population), but not other lymphocytes, has prometastatic effects on melanoma cells in vivo through a direct heterotypic cell-cell interaction. In the classic B16 mouse melanoma model, one mechanism underlying this phenomenon is a specific up-regulation and subsequent homophilic interaction mediated by the cell surface glycoprotein MUC18 (also known as melanoma cell adhesion molecule). Presence of B-1 lymphocytes in a panel of tumor samples from melanoma patients directly correlates with MUC18 expression in melanoma cells, indicating that the same protein interaction exists in humans. These results suggest a new but as yet unrecognized functional role for host B-1 lymphocytes in tumor metastasis and establish a biochemical basis for such observations. Our findings support the counterintuitive central hypothesis in which a primitive layer of the immune system actually contributes to tumor progression and metastasis in a mouse model and in melanoma patients. Given that monoclonal antibodies against MUC18 are in preclinical development but the reason for their antitumor activity is not well understood, these translational results are relevant in the setting of human melanoma and perhaps of other cancers.

Circulating and imaging markers for angiogenesis

Abundant preclinical and indirect clinical data have for several decades convincingly supported the notion that anti-angiogenesis is an effective strategy for the inhibition of tumor growth. The recent success achieved in patients with metastatic colon carcinoma using a neutralizing antibody directed against vascular endothelial growth factor (VEGF) has translated preclinical optimism into a clinical reality.With this transformation in the field of angiogenesis has come a need for reliable surrogate markers. A surrogate marker by definition serves as a substitute for the underlying process in question, and in the case of angiogenesis, microvessel density (usually in so-called "hot-spots") has until now been the most widely used parameter. However, this parameter is more akin to a static "snap-shot" and does not lend itself either to the dynamic in situ assessment of the status of the tumor microvasculature or to the molecular factors that regulate its growth and involution. This has led to an acute need for developing circulating and imaging markers of angiogenesis that can be monitored in vivo at repeated intervals in large number of patients with a variety of tumors in a non-invasive manner. Such markers of angiogenesis are the subject of this review.

Skeletal stem cells: phenotype, biology and environmental niches informing tissue regeneration

Advances in our knowledge of the biology of skeletal stem cells, together with an increased understanding of the regeneration of normal tissue offer exciting new therapeutic approaches in musculoskeletal repair. Skeletal stem cells from various adult tissues such as bone marrow can be identified and isolated based on their expression of a panel of markers associated with smooth muscle cells, pericytes and endothelial cells. Thus, skeletal stem cell-like populations within bone marrow may share a common perivascular stem cell niche within the microvascular network. To date, the environmental niche that nurtures and maintains the stromal stem cell at different anatomical sites remains poorly understood. However, an understanding of the osteogenic and perivascular niches will inform identification of the key growth factors, matrix constituents and physiological conditions that will enhance the ex vivo amplification and differentiation of osteogenic stem cells to mimic native tissue critical for tissue repair. This review will examine skeletal stem cell biology, the advances in our understanding of the skeletal and perivascular niche and interactions therein and the opportunities to harness that knowledge for musculoskeletal regeneration.

Identification of surface markers for prospective isolation of human endometrial stromal colony-forming cells

BACKGROUND

Human endometrium is a highly regenerative tissue. We hypothesized that the source of endometrial stromal and vascular regeneration is a resident stromal stem/progenitor cell population. Putative human endometrial stromal stem/progenitor cells have been identified using clonal assays, a retrospective functional stem cell assay. Therefore, the aim of this study was to screen potential stem cell markers for the prospective isolation of human endometrial stromal stem/progenitor cells and to determine their capacity to identify colony-forming stromal cells.

METHODS

Single-cell suspensions of human endometrial stromal cells were sorted using fluorescence-activated cell sorting into positive and negative populations based on STRO-1, CD133, CD90 or CD146 expression for clonal assays. All markers were immunolocalized in human endometrium.

RESULTS

Small populations (2-9%) of human endometrial stromal cells expressed each of the markers. Only CD146(+) cells were enriched for colony-forming cells, and CD90(hi) cells showed a trend for greater enrichment compared with CD90(lo) cells. STRO-1 and CD146 were localized to perivascular cells of the endometrium. CD90 was strongly expressed by functionalis stroma and perivascular cells, but only weakly expressed in the basalis stroma. CD133 was expressed by epithelial cells of the endometrium, rather than by stroma or perivascular cells.

CONCLUSIONS

This study identified CD146 as a marker of colony-forming human endometrial stromal cells supporting the concept that human endometrium contains a population of candidate stromal stem/progenitor cells.

A method to isolate and purify human bone marrow stromal stem cells

The STRO-1 antibody can be used as a single reagent to isolate human bone marrow stromal stem cells (BMSSC), owing to its restricted specificity to a cell surface molecule expressed by clonogenic BMSSC, with little or no reactivity to hematopoietic stem/progenitor populations or mature stromal elements. The present protocol uses a combination of two different immunoselection methodologies in an attempt to generate highly purified preparations of BMSSC. This process involves the initial isolation of a minor subpopulation of bone marrow mononuclear cells (approx 10%) expressing the STRO-1 antigen, by means of magnetic activated cell sorting. Dual-color fluorescence activated cell sorting is then used as a secondary step to further purify the rare STRO-1bright expressing fraction that contains all of the colony-forming BMSSC, based on their co-expression of a secondary cell surface marker, CD106 (VCAM-1).

Specific plasma membrane protein phenotype of culture-amplified and native human bone marrow mesenchymal stem cells

We have studied the plasma membrane protein phenotype of human culture-amplified and native bone marrow mesenchymal stem cells (BM MSCs). We have found, using microarrays and flow cytometry, that cultured cells express specifically 113 transcripts and 17 proteins that were not detected in hematopoietic cells. These antigens define a lineage-homogenous cell population of mesenchymal cells, clearly distinct from the hematopoietic lineages, and distinguishable from other cultured skeletal mesenchymal cells (periosteal cells and synovial fibroblasts). Among the specific membrane proteins present on cultured MSCs, 9 allowed the isolation from BM mononuclear cells of a minute population of native MSCs. The enrichment in colony-forming units-fibroblasts was low for CD49b, CD90, and CD105, but high for CD73, CD130, CD146, CD200, and integrin alphaV/beta5. In addition, the expression of CD73, CD146, and CD200 was down-regulated in differentiated cells. The new marker CD200, because of its specificity and immunomodulatory properties, deserves further in-depth studies.

Postnatal skeletal stem cells

Postnatal skeletal stem cells are a subpopulation of the bone marrow stromal cell network. To date, the most straightforward way of assessing the activity of skeletal stem cells within the bone marrow stromal cell (BMSC) population is via analysis of the rapidly adherent, colony-forming unit-fibroblast (CFU-F), and their progeny, BMSCs. Several in vitro methods are employed to determine the differentiation capacity of BMSCs, using osteogenic and adipogenic "cocktails" and staining protocols, and pellet cell culture for chondrogenic differentiation. However, true differentiation potential is best determined by in vivo transplantation in either closed or open systems. By in vivo transplantation, approximately 10% of the clonal strains are able to form bone, stroma, and marrow adipocytes, and are true skeletal stem cells. Furthermore, when derived from patients or animal models with abnormalities in gene expression, they recapitulate the disease phenotype on in vivo transplantation. Although ex vivo expansion of BMSCs inevitably dilutes the skeletal stem cells, when used en masse, they are attractive candidates for reconstruction of segmental bone defects, and as targets for gene therapy.

Stem cells and tooth tissue engineering

The notion that teeth contain stem cells is based on the well-known repairing ability of dentin after injury. Dental stem cells have been isolated according to their anatomical locations, colony-forming ability, expression of stem cell markers, and regeneration of pulp/dentin structures in vivo. These dental-derived stem cells are currently under increasing investigation as sources for tooth regeneration and repair. Further attempts with bone marrow mesenchymal stem cells and embryonic stem cells have demonstrated the possibility of creating teeth from non-dental stem cells by imitating embryonic development mechanisms. Although, as in tissue engineering of other organs, many challenges remain, stem-cell-based tissue engineering of teeth could be a choice for the replacement of missing teeth in the future.

Clinical-Scale Expansion of a Mixed Population of Bone Marrow-Derived Stem and Progenitor Cells for Potential Use in Bone Tissue Regeneration

Preclinical and clinical studies have demonstrated the ability of bone marrow derived stem and progenitor cells to regenerate many tissues, including bone. Methods to expand or enrich progenitors from bone marrow are common; however, these methods include many steps not amenable to clinical use. A closed automated cell production culture system was developed for clinical-scale ex vivo production of bone marrow-derived stem and progenitor cells for hematopoietic reconstitution. The current study tested the ability of this bioreactor system to produce progenitor cells, termed tissue repair cells (TRC), possessing osteogenic potential. Three TRC formulations were evaluated: (a) cells cultured without exogenous cytokines (TRC); (b) cells cultured with exogenous cytokines (TRC-C); and (c) an adherent subset of TRC-C (TRC-C(Ad)). Starting human bone marrow mononuclear cells (BM MNC) and TRC products were characterized for the expression of cell surface markers, in vitro colony forming ability, and in vivo osteogenic potential. Results showed significant expansion of mesenchymal progenitors (CD90+, CD105+, and CD166+) in each TRC formulation. In vivo bone formation, measured by histology, was highest in the TRC group, followed by TRC-C(Ad) and TRC-C. The TRC product outperformed starting BM MNC and had equivalent bone forming potential to purified MSCs at the same cell dose. Post hoc analysis revealed that the presence of CD90+, CD105+, and CD166+ correlated strongly with in vivo bone formation scores (r(2) > .95). These results demonstrate that this bioreactor system can be used to generate, in a single step, a population of progenitor cells with potent osteogenic potential. Disclosure of potential conflicts of interest is found at the end of this article.

Co-expression of two perivascular cell markers isolates mesenchymal stem-like cells from human endometrium

BACKGROUND

Human endometrium has immense regenerative capacity, growing ~5 mm in 7 days every month. We have previously identified a small population of colony-forming endometrial stromal cells which we hypothesize are mesenchymal stem cells (MSC). The aim of this study was to determine if the co-expression of two perivascular cell markers, CD146 and platelet-derived growth factor-receptor beta (PDGF-Rbeta), will prospectively isolate endometrial stromal cells which exhibit MSC properties, and determine their location in human endometrium.

METHODS

Single cell suspensions of human endometrial stromal cells were fluorescence activated cell sorting (FACS) sorted into CD146(+)PDGF-Rbeta(+) and CD146(-)PDGF-Rbeta(-) populations and analysed for colony-forming ability, in vitro differentiation and expression of typical MSC markers. Full thickness human endometrial sections were co-stained for CD146 and PDGF-Rbeta.

RESULTS

FACS stromal CD146(+)PDGF-Rbeta(+) stromal cells (1.5% of sorted population) were enriched for colony-forming cells compared with CD146(-)PDGF-Rbeta(-) cells (7.7 +/- 1.7 versus 0.7 +/- 0.2% P <0.0001), and also underwent differentiation into adipogenic, osteogenic, myogenic and chondrogenic lineages. They expressed MSC phenotypic surface markers and were located near blood vessels.

CONCLUSION

This study shows that human endometrium contains a small population of MSC-like cells that may be responsible for its cyclical growth, and may provide a readily available source of MSC for tissue engineering applications.

Identification of tendon stem/progenitor cells and the role of the extracellular matrix in their niche

The repair of injured tendons remains a great challenge, largely owing to a lack of in-depth characterization of tendon cells and their precursors. We show that human and mouse tendons harbor a unique cell population, termed tendon stem/progenitor cells (TSPCs), that has universal stem cell characteristics such as clonogenicity, multipotency and self-renewal capacity. The isolated TSPCs could regenerate tendon-like tissues after extended expansion in vitro and transplantation in vivo. Moreover, we show that TSPCs reside within a unique niche predominantly comprised of an extracellular matrix, and we identify biglycan (Bgn) and fibromodulin (Fmod) as two critical components that organize this niche. Depletion of Bgn and Fmod affects the differentiation of TSPCs by modulating bone morphogenetic protein signaling and impairs tendon formation in vivo. Our results, while offering new insights into the biology of tendon cells, may assist in future strategies to treat tendon diseases.

The concept of mesenchymal stem cells

In this chapter we examine whether criteria usually defining adult tissue stem cells apply to mesenchymal stem cells (MSCs) that give rise to cells of the skeletal connective tissues. MSCs appear to constitute a heterogeneous population of undifferentiated and committed, lineage-primed cells, capable of: homing upon engraftment to a number of growth microenvironments, extensive proliferation, producing large numbers of differentiated progeny, and functional tissue repair after injury. In addition, MSCs are extensively distributed throughout tissues, and bone marrow MSCs provide the stromal component of the niche of hematopoietic stem cells. The capacity of apparently differentiated mesenchymal cells to shift their differentiation pathway with changing microenvironmental conditions (known as differentiation plasticity) may be due to de-differentiation and reprogramming in MSCs. Because they present several features setting them apart from other stem cells, MSCs may constitute another paradigm for stem cell systems, where self-renewal and hierarchy are no longer essential, but where plasticity is the major characteristic.

Bone marrow-derived mesenchymal stem cells for regenerative medicine in craniofacial region

The craniofacial region contains many specified tissues including bone, cartilage, muscle, blood vessels and neurons. Defect or dysfunction of the craniofacial tissue after post-cancer ablative surgery, trauma, congenital malformations and progressive deforming skeletal diseases has a huge influence on the patient's life. Therefore, functional reconstruction of damaged tissues is highly expected. Bone marrow-derived mesenchymal stem cells (BMMSCs) are one of the most well characterized postnatal stem cell populations, and considered to be utilized for cell-based clinical therapies. Here, the current understanding and the potential applications in craniofacial tissue regeneration of BMMSCs are reviewed, and the current limitations and drawbacks are also discussed.

Mesenchymal lineage precursor cells induce vascular network formation in ischemic myocardium

Mesenchymal lineage precursors can be reproducibly isolated from adult mammalian bone marrow and grown in culture. Immunoselection with monoclonal antibodies against STRO-1 and vascular-cell-adhesion molecule 1 (VCAM1/CD106) prior to expansion results in a 1,000-fold enrichment of mesenchymal precursors compared to standard isolation techniques. Intramyocardial injection of human STRO-1-selected precursors in an athymic rat model of acute myocardial infarction results in induction of vascular network formation and arteriogenesis coupled with global functional cardiac recovery.

A dileucine motif targets MCAM-l cell adhesion molecule to the basolateral membrane in MDCK cells

Melanoma cell adhesion molecule (MCAM), an adhesion molecule belonging to the Ig superfamily, is an endothelial marker and is expressed in different epithelia. MCAM is expressed as two isoforms differing by their cytoplasmic domain: MCAM-l and MCAM-s (long and short). In order to identify the respective role of each MCAM isoform, we analyzed MCAM isoform targeting in polarized epithelial Madin-Darby canine kidney (MDCK) cells using MCAM-GFP chimeras. Confocal microscopy revealed that MCAM-s and MCAM-l were addressed to the apical and basolateral membranes, respectively. Transfection of MCAM-l mutants established that a single dileucine motif (41-42) of the cytoplasmic domain was required for MCAM-l basolateral targeting in MDCK cells. Although double labelling experiments showed that MCAM-l is not a component of adherens junctions and focal adhesions, its expression on basolateral membranes suggests that MCAM-l is involved in epithelium insuring.

Enzymatic large-scale synthesis of MUC6-Tn glycoconjugates for antitumor vaccination

In cancer, mucins are aberrantly O-glycosylated, and consequently, they express tumor-associated antigens such as the Tn determinant (alpha-GalNAc-O-Ser/Thr). As compared with normal tissues, they also exhibit a different pattern of expression. In particular, MUC6, which is normally expressed only in gastric tissues, has been detected in intestinal, pulmonary, colorectal, and breast carcinomas. Recently, we have shown that the MCF7 breast cancer cell line expresses MUC6-Tn glycoproteins in vivo. Cancer-associated mucins show antigenic differences from normal mucins, and as such, they may be used as potential targets for immunotherapy. To develop anticancer vaccines based on the Tn antigen, we prepared several MUC6-Tn glycoconjugates. To this end, we performed the GalNAc enzymatic transfer to two recombinant MUC6 proteins expressed in Escherichia coli, using UDP-N-acetylgalactosamine: polypeptide N-acetylgalactosaminyltransferases (ppGalNAc-Ts), which catalyze in vivo the Tn antigen synthesis. We used either a mixture of ppGalNAc-Ts from MCF7 breast cancer cell extracts or a recombinant ppGalNAc-T1. In both cases, we achieved the synthesis of MUC6-Tn glycoconjugates at a semi-preparative scale (mg amounts). These glycoproteins displayed a high level of Tn antigens, although the overall density depends on both enzyme source and protein acceptor. These MUC6-Tn glycoconjugates were recognized by two anti-Tn monoclonal antibodies that are specific to human cancer cells. Moreover, the MUC6-Tn glycoconjugate glycosylated using MCF7 extracts as the ppGalNAc-T source was able to induce immunoglobulin G (IgG) antibodies that recognized a human tumor cell line. In conclusion, the large-scaled production of MUC6 with tumor-relevant glycoforms holds considerable promise for developing effective anticancer vaccines, and further studies of their immunological properties are warranted.