Dynamics of T cell repertoire renewal following autologous hematopoietic stem cell transplantation in multiple sclerosis.

Autologous hematopoietic stem cell transplantation (aHSCT) is a highly effective treatment of multiple sclerosis (MS). It depletes autoreactive cells and subsequently renews adaptive immune cells. The possible proinflammatory potential of surviving T cells early after aHSCT has not been studied. Here, we examined the dynamics of new and surviving T cells in 27 patients after aHSCT by multidimensional flow cytometry, T cell receptor (TCR) sequencing, specificity testing, telomere length profiling, and HLA genotyping. Early after aHSCT, naïve T cells are barely detectable, whereas effector memory (EM) T cells quickly reconstitute to pre-aHSCT values. EM CD4+ T cells early after aHSCT have shorter telomeres, have higher expression of senescence and exhaustion markers, and proliferate less than those before aHSCT. We find a median TCR repertoire overlap of 26% between the early post-aHSCT EM CD4+ T cells and pre-aHSCT, indicating persistence of EM CD4+ T cells early after transplantation. The EM CD4+ TCR repertoire overlap declines to 15% at 12 months after aHSCT, whereas the naïve TCR repertoire entirely renews. HLA-DR-associated EM CD4+ T cell reactivity toward MS-related antigens decreased after aHSCT, whereas reactivity toward EBV increased. Our data show substantial survival of pre-aHSCT EM CD4+ T cells early after transplantation but complete renewal of the T cell repertoire by nascent T cells later.

Characterization of Antigen-Induced CD4+ T-Cell Senescence in Multiple Sclerosis.

Antigen-induced T-cell exhaustion and T-cell senescence are peripheral regulatory mechanisms that control effector T-cell responses. Markers of exhaustion and senescence on T Cells indicate the previous activation by repetitive stimulation with specific antigens. Malignant tumors are accompanied by enhanced T-cell exhaustion and T-cell senescence resulting in immune evasion, while these control mechanisms might be diminished in autoimmune diseases including multiple sclerosis (MS). To better understand the involvement of antigen-induced T-cell senescence in controlling CD4+ T-cell-mediated autoimmune responses in MS, we have analyzed the re-expression of CD45RA and the downregulation of CD28 and CD27 molecules as markers of antigen-induced T-cell senescence in fresh cerebrospinal fluid (CSF)-infiltrating and paired circulating T cells from patients with MS. Patients with different levels of CD4+ T-cell senescence were identified and characterized regarding demographical and clinical features as well as intrathecal markers of neurodegeneration. CD4+ T-cell senescence was also analyzed in control patients to explore a putative deficit of this regulatory mechanism in MS. This study shows heterogeneity of markers of CD4+ T-cell senescence in patients with MS. Patients with high levels of CD4+ T-cell senescence in peripheral blood showed increased frequencies of CSF-infiltrating CD28+ CD27-EM CD4+ T cells with a proinflammatory Th1 functional phenotype. The correlation of these cells with the intrathecal levels of neurofilament light chain, a marker of neurodegeneration, suggests their relevance in disease pathogenesis and the involvement of T-cell senescence in their regulation. Markers of antigen-induced T-senescence, therefore, show promise as a tool to identify pathogenic CD4+ T cells in patients with MS.

T-Cell Specificity Influences Disease Heterogeneity in Multiple Sclerosis.

BACKGROUND AND OBJECTIVES: Encouraged by the enormous progress that the identification of specific autoantigens added to the understanding of neurologic autoimmune diseases, we undertook here an in-depth study of T-cell specificities in the autoimmune disease multiple sclerosis (MS), for which the spectrum of responsible autoantigens is not fully defined yet. The identification of target antigens in MS is crucial for therapeutic strategies aimed to induce antigen-specific tolerance. In addition, knowledge of relevant T-cell targets can improve our understanding of disease heterogeneity, a hallmark of MS that complicates clinical management. METHODS: The proliferative response and interferon gamma (IFN-γ) release of CSF-infiltrating CD4+ T cells from patients with MS against several autoantigens was used to identify patients with different intrathecal T-cell specificities. Fresh CSF-infiltrating and paired circulating lymphocytes in these patients were characterized in depth by ex vivo immunophenotyping and transcriptome analysis of relevant T-cell subsets. Further examination of these patients included CSF markers of inflammation and neurodegeneration and a detailed characterization with respect to demographic, clinical, and MRI features. RESULTS: By testing CSF-infiltrating CD4+ T cells from 105 patients with MS against seven long-known myelin and five recently described GDP-l-fucose synthase peptides, we identified GDP-l-fucose synthase and myelin oligodendrocyte glycoprotein (35-55) responder patients. Immunophenotyping of CSF and paired blood samples in these patients revealed a significant expansion of an effector memory (CCR7- CD45RA-) CD27- Th1 CD4+ cell subset in GDP-l-fucose synthase responders. Subsequent transcriptome analysis of this subset demonstrated expression of Th1 and cytotoxicity-associated genes. Patients with different intrathecal T-cell specificities also differ regarding inflammation- and neurodegeneration-associated biomarkers, imaging findings, expression of HLA class II alleles, and seasonal distribution of the time of the lumbar puncture. DISCUSSION: Our observations reveal an association between autoantigen reactivity and features of disease heterogeneity that strongly supports an important role of T-cell specificity in MS pathogenesis. These data have the potential to improve patient classification in clinical practice and to guide the development of antigen-specific tolerization strategies.

Mechanistic and Biomarker Studies to Demonstrate Immune Tolerance in Multiple Sclerosis.

The induction of specific immunological tolerance represents an important therapeutic goal for multiple sclerosis and other autoimmune diseases. Sound knowledge of the target antigens, the underlying pathomechanisms of the disease and the presumed mechanisms of action of the respective tolerance-inducing approach are essential for successful translation. Furthermore, suitable tools and assays to evaluate the induction of immune tolerance are key aspects for the development of such treatments. However, investigation of the mechanisms of action underlying tolerance induction poses several challenges. The optimization of sensitive, robust methods which allow the assessment of low frequency autoreactive T cells and the long-term reduction or change of their responses, the detection of regulatory cell populations and their immune mediators, as well as the validation of specific biomarkers indicating reduction of inflammation and damage, are needed to develop tolerance-inducing approaches successfully to patients. This short review focuses on how to demonstrate mechanistic proof-of-concept in antigen-specific tolerance-inducing therapies in MS.

NK Cells and Innate-Like T Cells After Autologous Hematopoietic Stem Cell Transplantation in Multiple Sclerosis.

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system, in which autoreactive T and B cells play important roles. Other lymphocytes such as NK cells and innate-like T cells appear to be involved as well. To name a few examples, CD56bright NK cells were described as an immunoregulatory NK cell subset in MS while innate-like T cells in MS were described in brain lesions and with proinflammatory signatures. Autologous hematopoietic stem cell transplantation (aHSCT) is a procedure used to treat MS. This procedure includes hematopoietic stem/progenitor cell (HSPC) mobilization, then high-dose chemotherapy combined with anti-thymocyte globulin (ATG) and subsequent infusion of the patients own HSPCs to reconstitute a functional immune system. aHSCT inhibits MS disease activity very effectively and for long time, presumably due to elimination of autoreactive T cells. Here, we performed multidimensional flow cytometry experiments in peripheral blood lymphocytes of 27 MS patients before and after aHSCT to address its potential influence on NK and innate-like T cells. After aHSCT, the relative frequency and absolute numbers of CD56bright NK cells rise above pre-aHSCT levels while all studied innate-like T cell populations decrease. Hence, our data support an enhanced immune regulation by CD56bright NK cells and the efficient reduction of proinflammatory innate-like T cells by aHSCT in MS. These observations contribute to our current understanding of the immunological effects of aHSCT in MS.

Hyaluronan mediates the adhesion of porcine peripheral blood mononuclear cells to poly (I:C)-treated intestinal cells and modulates their cytokine production.

Hyaluronan (HA), a major component of the extracellular matrix (ECM), has been increasingly recognized as a regulator of inflammation. Its role is complex since it has pro- and anti-inflammatory actions by modulating the expression of inflammatory genes, the recruitment of inflammatory cells and the production of inflammatory cytokines, but also by attenuating the course of inflammation and providing protection against tissue damage. Certain viruses and other inflammatory stimuli induce organization of HA into cable-like structures, which may be responsible for leukocyte recruitment and, on the other hand, low molecular weight fragments of HA have been shown to activate various inflammatory responses. The aim of the present study was to analyze the effects of a simulated infection with the viral mimetic Poly (I:C) on HA deposition on different porcine intestinal cells (primary colonic muscular smooth muscle cells (SMC), and epithelial IPEC-J2 and IPI-2I cell lines) and on the recruitment of peripheral blood mononuclear cells (PBMC) to intestinal cell layers. We show that Poly (I:C) treatment induces the formation of an HA-based pericellular matrix coat in muscular SMC and in intestinal epithelial cells (IECs) and that, on differentiated IPEC-J2 cells, HA accumulates in the basolateral membrane. Porcine PBMCs bind to Poly (I:C)-treated cells and this binding is dependent on HA, since the increase in adhesion is abolished by hyaluronidase treatment of the cell layers. A second goal was to study the effect of different molecular weight HA forms on the production of pro-inflammatory cytokines and chemokines (TNF-α, IL-1ß and IL-8) by porcine PBMCs. Low molecular weight HA fragments (100-150kDa), in contrast to high molecular weight HA (2500kDa), stimulate the release of these pro-inflammatory mediators by porcine PBMCs. Our results suggest that HA is involved in the inflammatory response against pathogenic insults to the porcine gut.

Molecular Pathology of Cryptorchidism-Induced Infertility.

Cryptorchidism is the most common cause of non-obstructive azoospermia in man. In contrast to the general belief that temperature-dependent effects on the undescended gonad damage cryptorchid testes before sexual maturation is complete, molecular pathology strongly supports the theory that impaired mini-puberty is responsible for azoospermia and infertility in cryptorchidism. Molecular biological observations favor LH deficiency, with EGR4 as a master regulatory gene in Leydig cell dysgenesis, as the reason for impaired mini-puberty, and recent evidence supports the idea that infertility in cryptorchidism is a consequence of alterations in the Piwi pathway.

Expression of matrix metalloproteinase-2 and -9 and membrane-type 1 matrix metalloproteinase in melanocytic tumors of dogs and canine melanoma cell lines.

OBJECTIVE: To evaluate expression of matrix metalloproteinase (MMP)-2 and -9 and membrane-type 1 MMP (MT1-MMP) in melanocytomas and malignant melanomas of dogs, analyze in vitro production of MMPs by canine melanoma cell lines and primary dermal fibroblasts, and investigate mutual communication between tumor cells and fibroblasts and the influence of collagen on MMP regulation. SAMPLE: 35 biopsy specimens from melanocytic tumors and primary dermal fibroblasts of dogs and 3 canine melanoma cell lines (CML-1, CML-10c2, and CML-6M). PROCEDURES: MMP-2, MMP-9, and MT1-MMP were detected in tumor samples by use of immunohistochemical analysis. In vitro production was analyzed via reverse transcriptase-PCR assay, immunocytochemical analysis, zymography, and immunoblotting. RESULTS: MMP-9 was overexpressed in malignant melanomas, compared with expression in melanocytomas, whereas no significant differences in MMP-2 and MT1-MMP immunostaining were detected. Stromal cells also often had positive staining results. In vitro, all 3 melanoma cell lines and dermal fibroblasts had evidence of MMP-2 and MT1-MMP, but only melanoma cells had evidence of MMP-9. Coculture of CML-1 or CML-10c2 cells and dermal fibroblasts induced an increase in expression of the active form of MMP-2. Culture of melanoma cells on type I collagen increased the activation state of MT1-MMP. CONCLUSIONS AND CLINICAL RELEVANCE: MMP-9 expression was increased in malignant melanomas of dogs. Stromal cells were a source for MMPs. Stromal cells, in combination with matrix components such as type I collagen, can interact with tumor cells to regulate MMP production. Information about MMP production and regulation could help in the development of new treatments.

Increased HAS2-driven hyaluronic acid synthesis in shar-pei dogs with hereditary cutaneous hyaluronosis (mucinosis).

The Chinese shar-pei dog is known for its distinctive feature of wrinkled and thickened skin, defined as primary or hereditary cutaneous mucinosis. In a recent report, we identified the mucinous material deposited in the shar-pei skin as the polysaccharide hyaluronan (HA). In the present work, the molecular and cellular mechanisms underlying this phenotype have been identified in dermal fibroblasts isolated from shar-pei dogs. The production of HA, which appeared to be mainly associated with cell membrane protrusions and also intracellular, was higher in shar-pei fibroblasts than in control cells. The HA accumulation is related to a higher mRNA expression of the isoform HAS2 of the HA-synthesizing enzyme family, hyaluronan synthases (HAS). The higher expression of HAS2 in shar-pei fibroblasts was confirmed at the protein level. The other HAS isoenzymes, HAS1 and HAS3, and the HA-degrading enzymes, Hyal1 and Hyal2, were not differentially expressed in shar-pei fibroblasts compared with cells from control dogs. Fibroblasts from shar-pei dogs and from control dogs are morphologically different as observed by transmission electron microscopy. Scanning electron microscopy revealed a large number of cellular protrusions with associated globular deposits. Electron microscopy after labelling with biotinylated HA-binding protein confirmed an increased HA content in shar-pei fibroblasts, which could be localized in several subcellular structures. The authors propose the name hereditary cutaneous hyaluronosis (HCH) for affected dogs, because it better defines the cutaneous mucinosis of shar-pei dogs.

A novel unstable duplication upstream of HAS2 predisposes to a breed-defining skin phenotype and a periodic fever syndrome in Chinese Shar-Pei dogs.

Hereditary periodic fever syndromes are characterized by recurrent episodes of fever and inflammation with no known pathogenic or autoimmune cause. In humans, several genes have been implicated in this group of diseases, but the majority of cases remain unexplained. A similar periodic fever syndrome is relatively frequent in the Chinese Shar-Pei breed of dogs. In the western world, Shar-Pei have been strongly selected for a distinctive thick and heavily folded skin. In this study, a mutation affecting both these traits was identified. Using genome-wide SNP analysis of Shar-Pei and other breeds, the strongest signal of a breed-specific selective sweep was located on chromosome 13. The same region also harbored the strongest genome-wide association (GWA) signal for susceptibility to the periodic fever syndrome (p(raw) = 2.3 × 10⁻6, p(genome) = 0.01). Dense targeted resequencing revealed two partially overlapping duplications, 14.3 Kb and 16.1 Kb in size, unique to Shar-Pei and upstream of the Hyaluronic Acid Synthase 2 (HAS2) gene. HAS2 encodes the rate-limiting enzyme synthesizing hyaluronan (HA), a major component of the skin. HA is up-regulated and accumulates in the thickened skin of Shar-Pei. A high copy number of the 16.1 Kb duplication was associated with an increased expression of HAS2 as well as the periodic fever syndrome (p < 0.0001). When fragmented, HA can act as a trigger of the innate immune system and stimulate sterile fever and inflammation. The strong selection for the skin phenotype therefore appears to enrich for a pleiotropic mutation predisposing these dogs to a periodic fever syndrome. The identification of HA as a major risk factor for this canine disease raises the potential of this glycosaminoglycan as a risk factor for human periodic fevers and as an important driver of chronic inflammation.

Role of versican V0/V1 and CD44 in the regulation of human melanoma cell behavior.

Versican is a hyaluronan-binding, large extracellular matrix chondroitin sulfate proteoglycan whose expression is increased in malignant melanoma. Binding to hyaluronan allows versican to indirectly interact with the hyaluronan cell surface receptor CD44. The aim of this work was to study the effect of silencing the large versican isoforms (V0 and V1) and CD44 in the SK-mel-131 human melanoma cell line. Versican V0/V1 or CD44 silencing caused a decrease in cell proliferation and migration, both in wound healing assays and in Transwell chambers. Versican V0/V1 silencing also caused an increased adhesion to type I collagen, laminin and fibronectin. These results support the proposed role of versican as a proliferative, anti-adhesive and pro-migratory molecule. On the other hand, CD44 silencing caused a decrease in cell adhesion to vitronectin, fibronectin and hyaluronan. CD44 silencing inhibited the binding of a FITC-hyaluronan complex to the cell surface and its internalization into the cytoplasm. Our results indicate that both versican and CD44 play an important role regulating the behavior of malignant melanoma cells.

V3 versican isoform alters the behavior of human melanoma cells by interfering with CD44/ErbB-dependent signaling.

Versican is a hyaluronan-binding, extracellular chondroitin sulfate proteoglycan produced by several tumor types, including malignant melanoma, which exists as four different splice variants. The short V3 isoform contains the G1 and G3 terminal domains of versican that may potentially interact directly or indirectly with the hyaluronan receptor CD44 and the EGFR, respectively. We have previously described that overexpression of V3 in MeWo human melanoma cells markedly reduces tumor cell growth in vitro and in vivo. In this study we have investigated the signaling mechanism of V3 by silencing the expression of CD44 in control and V3-expressing melanoma cells. Suppression of CD44 had the same effects on cell proliferation and cell migration than those provoked by V3 expression, suggesting that V3 acts through a CD44-mediated mechanism. Furthermore, CD44-dependent hyaluronan internalization was blocked by V3 expression and CD44 silencing, leading to an accumulation of this glycosaminoglycan in the pericellular matrix and to changes in cell migration on hyaluronan. Furthermore, ERK1/2 and p38 activation after EGF treatment were decreased in V3-expressing cells suggesting that V3 may also interact with the EGFR through its G3 domain. The existence of a EGFR/ErbB2 receptor complex able to interact with CD44 was identified in MeWo melanoma cells. V3 overexpression resulted in a reduced interaction between EGFR/ErbB2 and CD44 in response to EGF treatment. Our results indicate that the V3 isoform of versican interferes with CD44 and the CD44-EGFR/ErbB2 interaction, altering the signaling pathways, such as ERK1/2 and p38 MAPK, that regulate cell proliferation and migration.

Differential expression of endoglin in human melanoma cells expressing the V3 isoform of versican by microarray analysis.

Versican is a large chondroitin sulfate proteoglycan produced by several tumor types, including malignant melanoma, which exists as four different splice variants. The large isoforms V0 and V1 promote melanoma cell proliferation. We previously described that overexpression of the short V3 isoform in MeWo human melanoma cells markedly reduced tumor cell growth in vitro and in vivo, but favored the appearance of secondary tumors. This study aimed to elucidate the mechanisms of V3 by identifying differentially expressed genes between parental and V3-expressing MeWo melanoma cells using microarray analysis. V3 expression significantly reduced the expression of endoglin, a transforming growth factor-ß superfamily co-receptor. Other differentially expressed genes were VEGF and PPP1R14B. Changes in endoglin levels were validated by qRT-PCR and Western blotting.

Structure and regulation of the versican promoter: the versican promoter is regulated by AP-1 and TCF transcription factors in invasive human melanoma cells.

Versican is a large chondroitin sulfate proteoglycan of the extracellular matrix that is involved in a variety of cellular processes. We showed previously that versican, which is overexpressed in cutaneous melanomas as well as in premalignant lesions, contributes to melanoma progression, favoring the detachment of cells and the metastatic dissemination. Here, we investigated the transcriptional regulation of the versican promoter in melanoma cell lines with different levels of biological aggressiveness and stages of differentiation. We show that versican promoter up-regulation accounts for the differential expression levels of mRNA and protein detected in the invasive SK-mel-131 human melanoma cells. The activity of the versican promoter increased 5-fold in these cells in comparison with that measured in non-invasive MeWo melanoma cells. Several transcriptional regulatory elements were identified in the proximal promoter, including AP-1, Sp1, AP-2, and two TCF-4 sites. We show that promoter activation is mediated by the ERK/MAPK and JNK signaling pathways acting on the AP-1 site, suggesting that BRAF mutation present in SK-mel-131 cells impinge upon the up-regulation of the versican gene through signaling elicited by the ERK/MAPK pathway. This is the first time the AP-1 transcription factor family has been shown to be related to the regulation of versican expression. Furthermore, deletion of the TCF-4 binding sites caused a 60% decrease in the promoter activity in SK-mel-131 cells. These results showing that AP-1 and TCF-4 binding sites are the main regulatory regions directing versican production provide new insights into versican promoter regulation during melanoma progression.

Altered expression of versican and hyaluronan in melanocytic tumors of dogs.

OBJECTIVE: To analyze the expression of versican and hyaluronan in melanocytomas and malignant melanomas of dogs, to correlate their expression with expression of the hyaluronan receptor CD44, and to identify enzymes responsible for the synthesis and degradation of hyaluronan in canine dermal fibroblasts and canine melanoma cell lines. SAMPLE POPULATION: 35 biopsy specimens from melanocytic tumors of dogs, canine primary dermal fibroblasts, and 3 canine melanoma cell lines. PROCEDURES: Versican, hyaluronan, and CD44 were detected in tumor samples by use of histochemical or immunohistochemical methods. Expression of hyaluronan-metabolizing enzymes was analyzed with a reverse transcriptase-PCR assay. RESULTS: Versican was found only in some hair follicles and around some blood vessels in normal canine skin, whereas hyaluronan was primarily found within the dermis. Hyaluronan was found in connective tissue of the oral mucosa. Versican and, to a lesser extent, hyaluronan were significantly overexpressed in malignant melanomas, compared with expression in melanocytomas. No significant difference was found between malignant tumors from oral or cutaneous origin. The expression of both molecules was correlated, but hyaluronan had a more extensive distribution than versican. Versican and hyaluronan were mainly associated with tumor stroma. Canine fibroblasts and melanoma cell lines expressed hyaluronan synthase 2 and 3 (but not 1) and hyaluronidase 1 and 2. CONCLUSIONS AND CLINICAL RELEVANCE: Versican may be useful as a diagnostic marker for melanocytic tumors in dogs. Knowledge of the enzymes involved in hyaluronan metabolism could reveal new potential therapeutic targets.

V3 versican isoform expression has a dual role in human melanoma tumor growth and metastasis.

Versican is a large chondroitin sulfate proteoglycan produced by several tumor cell types, including malignant melanoma, which exists as four different splice variants. The presence of versican in the extracellular matrix plays a role in tumor cell growth, adhesion and migration, which could be altered by altering the ratio between versican isoforms. We have previously shown that overexpression of the V3 isoform of versican in human melanoma cell lines markedly reduces cell growth in vitro and in vivo, since V3-overexpressing (LV3SN) cultured cells as well as primary tumors arising from these cells grow slower than their vector-only counterparts (LXSN). In the present work, we have extended these observations to demonstrate that the delayed cell growth is due to multiple events since differences in proliferative index as well as in apoptosis are observed in LV3SN cells and tumors compared to LXSN. For example, LV3SN melanoma cells exhibit delayed activation of MAPK in response to EGF, we have also characterized further the primary tumors originated in nude mice from V3-transduced melanoma cells to determine if other events affect the V3 tumor phenotype. For example, hyaluronan content of LV3SN tumors was higher than in LXSN tumors, whereas other related matrix components and vascularization were unaffected. Furthermore, lung metastasis in nude mice occurred only in animals carrying LV3SN tumors, indicating a dual role for this molecule, both as an inhibitor of tumor growth and a metastasis inductor.

V3 versican isoform expression alters the phenotype of melanoma cells and their tumorigenic potential.

Versican is a large chondroitin sulfate proteoglycan produced by several tumor cell types, including malignant melanoma. The expression of increased amounts of versican in the extracellular matrix may play a role in tumor cell growth, adhesion and migration. We have expressed the V3 isoform of versican in human and canine melanoma cell lines. Retroviral overexpression of V3 did not change the morphology of any of the cell lines but markedly reduces cell growth in the V3 versican expressing melanoma cells. The V3-overexpressing melanoma cells retain their diminished growth potential in vivo because primary tumors arising from these cell lines growth more slowly than their vector only counterparts. This effect was accompanied by increases in cell adhesion on hyaluronan and an enhanced ability to migrate on hyaluronan-coated transwell chambers. This enhanced migration is blocked when cells are preincubated with soluble hyaluronan, or anti-CD44 antibodies, suggesting that V3 acts by altering the hyaluronan-CD44 interaction. Hyaluronan content and CD44 expression are not altered in V3-overexpressing cells compared to vector-transduced cells. Our results show that V3 overproduction modulates the in vitro behavior of human and canine melanoma cell lines and reduces their tumorigenicity in vivo.

Differential expression of versican isoforms is a component of the human melanoma cell differentiation process.

Versican is a large chondroitin sulfate proteoglycan produced by human melanoma cell lines and malignant melanocytic lesions. In the present work, we have analyzed the expression of versican spliced variants V0, V1, V2 and V3 in human melanoma cell lines at several differentiation degrees. The isoform expression pattern depends on the degree of cell differentiation. Differentiated cell lines do not produce any of the versican isoforms as analyzed by Western blot, Northern blot and RT-PCR. All cell lines with an early or intermediate degree of differentiation (AX3, SK-mel-37, Rider, SK-mel-1.36-1-5 and SK-mel-3.44) expressed V0 and V1 transcripts, whereas V2 and V3 expression was shown only by the undifferentiated cell lines SK-mel-1.36-1-5 and Rider. Furthermore, we have analyzed the expression of versican isoforms in SK-mel-3.44 and SK-mel-1.36-1-5 cells induced to differentiate by TPA treatment. The expression of the large V0, V1 and V2 isoforms practically disappears in differentiated cells, whereas V3 remains detectable by RT-PCR analysis.