c-myb proto-oncogene is expressed by quiescent scleroderma fibroblasts and, unlike B-myb gene, does not correlate with proliferation

c-Myb and C/EBPβ regulate OPN and other senescence-associated secretory phenotype factors

Tumorigenesis results from the convergence of cell autonomous mutations and corresponding stromal changes that promote tumor cell growth. Senescent cells, which secrete a plethora of pro-tumorigenic factors termed the senescence-associated secretory phenotype (SASP), play an important role in tumor formation. Investigation into SASP regulation revealed that many but not all SASP factors are subject to NF-kB and p38MAPK regulation. However, many pro-tumorigenic SASP factors, including osteopontin (OPN), are not responsive to these canonical pathways leaving the regulation of these factors an open question. We report that the transcription factor c-Myb regulates OPN, IL-6, and IL-8 in addition to 57 other SASP factors. The regulation of OPN is direct as c-Myb binds to the OPN promoter in response to senescence. Further, OPN is also regulated by the known SASP regulator C/EBPβ. In response to senescence, the full-length activating C/EBPβ isoform LAP2 increases binding to the OPN, IL-6, and IL-8 promoters. The importance of both c-Myb and C/EBPβ is underscored by our finding that the depletion of either factor reduces the ability of senescent fibroblasts to promote the growth of preneoplastic epithelial cells.

Myb via TGFβ is required for collagen type 1 production and skin integrity

Skin integrity requires an ongoing replacement and repair orchestrated by several cell types. We previously investigated the architecture of the skin of avian myeloblastosis viral oncogene homolog (Myb) knock-out (KO) embryos and wound repair in Myb(+/)(-) mice revealing a need for Myb in the skin, attributed to fibroblast-dependent production of collagen type 1. Here, using targeted Myb deletion in keratin-14 (K14) positive cells we reveal further Myb-specific defects in epidermal cell proliferation, thickness and ultrastructural morphology. This was associated with a severe deficit in collagen type 1 production, reminiscent of that observed in patients with ichthyosis vulgaris and Ehlers-Danlos syndrome. Since collagen type 1 is a product of fibroblasts, the collagen defect observed was unexpected and appears to be directed by the loss of Myb with significantly reduced tumor growth factor beta 1 (Tgfβ-1) expression by primary keratinocytes. Our findings support a specific role for Myb in K14+ epithelial cells in the preservation of adult skin integrity and function.

Scleromyxedema: a case report and review of the literature

Scleromyxedema (SM) is a sclerotic variant of lichen or papular mucinosis in which lichenoid papules and scleroderma-like features are both present. It is a rare deposition disorder characterized by generalized papular and sclerodermoid eruptions, mucin deposition, increased fibroblast proliferation, fibrosis, and monoclonal gammopathy (also known as paraproteinemia) mainly of the immunoglobulin G-lambda type in the absence of thyroid disease. It usually affects middle-aged adults and shows no gender or racial predilection. In addition to the skin findings and paraproteinemia, patients with SM have variable multisystem affections that mimic systemic sclerosis; the systems which are commonly involved include the gastrointestinal tract, musculoskeletal, pulmonary, cardiovascular, renal, and central nervous systems, leading to significant morbidity and mortality. Prominent symptoms include dysphagia, proximal muscle weakness, and dyspnea on exertion; less common but important findings include central nervous system involvement in the form of encephalopathy, convulsions, coma, and psychosis.

A fibrotic focus is a prognostic factor and a surrogate marker for hypoxia and (lymph)angiogenesis in breast cancer: review of the literature and proposal on the criteria of evaluation

A fibrotic focus is a scar-like area in the centre of a carcinoma and can be regarded as a focus of exaggerated reactive tumour stroma formation. Although modern surgical pathology uses different histopathological and molecular markers to assess the aggressiveness and predict the behaviour of malignant tumours, markers reflecting stromal cell behaviour and interactions between epithelial cells and stromal cells are scarce. In this review we summarize all studies investigating the value of a fibrotic focus as a prognostic factor and as a surrogate marker for hypoxia and (lymph)angiogenesis in patients with breast cancer. These data show that a fibrotic focus can be used as a practical, easily assessable and reproducible integrative histological prognostic parameter in breast cancer. We propose a consensus methodology to assess the fibrotic focus in breast cancer.

Scleroderma fibroblasts demonstrate enhanced activation of Akt (protein kinase B) in situ

Recent studies suggest that, in addition to activation and hypersecretion of matrix components, fibroblasts from patients with systemic sclerosis (SSc) are relatively resistant to apoptosis. Transforming growth factor-beta (TGF)-beta is strongly implicated in the pathogenesis of SSc and we and others have shown that TGF-beta can activate Akt, a kinase with potent anti-apoptotic effects. To determine whether Akt was activated in SSc, we quantified phospho-Akt expression in skin fibroblasts in vitro by western blot analysis and a functional kinase assay. In addition, the relative proportion of fibroblasts containing activated Akt in was quantified by immunohistochemistry on skin sections insitu. Analysis of Akt phosphorylation of skin fibroblasts in vitro suggested increased phosphorylation of Akt, and evaluation of skin sections by immunohistochemistry revealed significantly higher percentages of fibroblasts that stained for phospho-Akt compared with controls (78% +/- 14.0% vs 13% +/- 9%, p < 0.001). In addition, co-incident staining of phospho-Akt and alpha-smooth muscle actin was observed in some fibroblasts. These findings indicate that Akt is activated insitu in skin fibroblasts from patients with SSc. Akt activation may contribute to resistance to apoptosis, selection of disease-inducing fibroblasts, and, possibly, myofibroblasts.

Cytokine regulation of pulmonary fibrosis in scleroderma

Pulmonary fibrosis occurs in up to 70% of scleroderma patients and progresses to cause severe restrictive lung disease in about 15% of patients. The mechanisms that cause pulmonary fibrosis in scleroderma remain incompletely understood. Increased amounts of mRNA or protein for multiple profibrotic cytokines and chemokines have been identified in lung tissue or broncholveolar lavage samples from scleroderma patients, when compared to healthy controls. These cytokines include transforming growth factor (TGF)-beta, connective tissue growth factor (CTGF), platelet-derived growth factor (PDGF), oncostatin M (OSM), monocyte chemotactic factor-1 and pulmonary and activation-regulated chemokine (PARC). Potential cellular sources of these profibrotic cytokines and chemokines in scleroderma lung disease include alternatively activated macrophages, activated CD8+ T cells, eosinophils, mast cells, epithelial cells and fibroblasts themselves. This review summarizes the literature on involvement of cytokines and chemokines in the development of pulmonary fibrosis in scleroderma.

B-Myb acts as a repressor of human COL1A1 collagen gene expression by interacting with Sp1 and CBF factors in scleroderma fibroblasts

We investigated the role of B-Myb, a cell-cycle-regulated transcription factor, in the expression of the alpha1 (I) pro-collagen gene (COL1A1) in scleroderma fibroblasts. Scleroderma or SSc (systemic sclerosis) is a fibrotic disease characterized by excessive production of extracellular matrix components, especially type I collagen. Northern-blot analysis showed an inverse relationship between COL1A1 mRNA expression and that of B-Myb during exponential cell growth and during quiescence in human SSc fibroblasts. Overexpression of B-Myb in SSc fibroblasts was correlated with decreased COL1A1 mRNA expression. Transient transfections localized the down-regulatory effect of B-Myb to a region containing the proximal 174 bp of the COL1A1 promoter that does not contain B-Myb consensus binding sites. Gel-shift analysis, using nuclear extracts from normal and SSc fibroblasts transfected with B-Myb, showed no differences in DNA-protein complex formation when compared with the nuclear extracts from mock-transfected cells. However, we found that B-Myb decreases Sp1 (specificity protein 1) and CBF (CCAAT-binding factor) binding for their specific sites localized in the 174 bp COL1A1 proximal promoter. These results were also confirmed using B-Myb-immunodepleted nuclear extracts. Furthermore, immunoprecipitation assays using SSc nuclear extracts demonstrated a physical interaction of B-Myb with Sp1 and CBF transcription factors, and also an interaction between Sp1 and CBF. In addition, by employing full-length or deleted B-Myb cDNA construct, we found that B-Myb down-regulates the COL1A1 proximal promoter through its C-terminal domain. Thus these results suggest that B-Myb may be an important factor in the pathway(s) regulating collagen production in SSc fibroblasts.

Characterization of the c-Myb-responsive region and regulation of the human type I collagen alpha 2 chain gene by c-Myb

We have characterized the role of c-Myb and B-Myb in the regulation of human type I collagen alpha2 chain gene expression in fibroblastic cells. We have identified four Myb-binding sites (MBSs) in the promoter. Transactivation assays on wild type and mutant promoter-reporter constructs demonstrated that c-Myb, but not B-Myb, can transactivate the human type I collagen alpha 2 chain gene promoter via the MBS-containing region. Electrophoretic mobility shift assay experiments showed that c-Myb specifically binds to each of the four MBS; however, the mutagenesis of site MBS-4 completely inhibited transactivation by c-Myb, at least in the full-length promoter. In agreement with these results, c-myb(-/-) mouse embryo fibroblasts (MEFs) showed a selective lack of expression of type I collagen alpha 2 chain gene but maintained the expression of fibronectin and type III collagen. Furthermore, transforming growth factor-beta induced type I collagen alpha 2 chain gene expression in c-myb(-/-) MEFs, implying that the transforming growth factor-beta signaling pathway is maintained and that the absence of COL1A2 gene expression in c-myb(-/-) MEFs is a direct consequence of the lack of c-Myb. The demonstration of the importance of c-Myb in the regulation of the type I collagen alpha 2 chain gene suggests that uncontrolled expression of c-Myb could be an underlying mechanism in the pathogenesis of several fibrotic disorders.

Factors involved in the regulation of type I collagen gene expression: implication in fibrosis

Type I collagen, the major component of extracellular matrix in skin and other tissues, is a heterotrimer of two alpha1 and one alpha2 collagen polypeptides. The synthesis of both chains is highly regulated by different cytokines at the transcriptional level. Excessive synthesis and deposition of collagen in the dermal region causes thick and hard skin, a clinical manifestation of scleroderma. To better understand the causes of scleroderma or other tissue fibrosis, it is very important to investigate the molecular mechanisms that cause upregulation of the Type I collagen synthesis in these tissues. Several cis-acting regulatory elements and trans-acting protein factors, which are involved in basal as well as cytokine-modulated Type I collagen gene expression, have been identified and characterized. Hypertranscription of Type I collagen in scleroderma skin fibroblasts may be due to abnormal activities of different positive or negative transcription factors in response to different abnormally induced signaling pathways. In this review, I discuss the present day understanding about the involvement of different factors in the regulation of basal as well as cytokine-modulated Type I collagen gene expression and its implication in scleroderma research.

Oxidative stress in scleroderma: maintenance of scleroderma fibroblast phenotype by the constitutive up-regulation of reactive oxygen species generation through the NADPH oxidase complex pathway

OBJECTIVE

To explore the role of reactive oxygen species (ROS) in the in vitro activation of skin fibroblasts from patients with systemic sclerosis (SSc).

METHODS

Fibroblasts were obtained from involved skin of patients with limited or diffuse SSc. Oxidative activity imaging in living cells was carried out using confocal microscopy. Levels of O2- and H2O2 released from fibroblasts were estimated by the superoxide dismutase (SOD)-inhibitable cytochrome c reduction and homovanilic acid assays, respectively. To verify NADPH oxidase activation, the light membrane of fibroblasts was immunoblotted with an anti-p47phox-specific antibody. Fibroblasts were stimulated with various cytokines and growth factors to determine whether any of these factors modulate ROS generation. Cell proliferation was estimated by 3H-thymidine incorporation. Northern blot analysis was used to study alpha1 and alpha2 type I collagen gene expression.

RESULTS

Unstimulated skin fibroblasts from SSc patients released more O2- and H2O2 in vitro through the NADPH oxidase complex pathway than did normal fibroblasts, since incubation of SSc fibroblasts with diphenylene iodonium, a flavoprotein inhibitor, suppressed the generation of ROS. This suppression was not seen with rotenone, a mitochondrial oxidase inhibitor, or allopurinol, a xanthine oxidase inhibitor. Furthermore, the cytosolic component of NADPH oxidase, p47phox, was translocated to the plasma membrane of resting SSc fibroblasts. A transient increase in ROS production was induced in normal but not in SSc fibroblasts by interleukin-1beta (IL-1beta), platelet-derived growth factor type BB (PDGF-BB), transforming growth factor beta1 (TGFbeta1), and H2O2. Treatment of normal and SSc fibroblasts with tumor necrosis factor a (TNFalpha), IL-2, IL-4, IL-6, IL-10, interferon-alpha (IFNalpha), IFNgamma, granulocyte-macrophage colony-stimulating factor (GM-CSP), G-CSF, or connective tissue growth factor (CTGF) had no effect on ROS generation. Constitutive ROS production by SSc fibroblasts was not inhibited when these cells were treated with catalase, SOD, IL-1 receptor antagonist, or antibodies blocking the effect of TGFbeta1, PDGF-BB, and other agonists (IL-4, IL-6, TNFalpha, CTGF). In contrast, treatment of SSc fibroblasts with the membrane-permeant antioxidant N-acetyl-L-cysteine inhibited ROS production, and this was accompanied by decreased proliferation of these cells and down-regulation of alpha1(I) and alpha2(I) collagen messenger RNA.

CONCLUSION

The constitutive intracellular production of ROS by SSc fibroblasts derives from the activation of an NADPH oxidase-like system and is essential to fibroblast proliferation and expression of type I collagen genes in SSc cells. Our results also exclude O2-, H2O2, IL-1beta, TGFbeta1, PDGF-BB, IL-4, IL-6, TNFalpha, or CTGF as mediators of a positive, autocrine feedback mechanism of ROS generation.

Highly proliferative fibroblasts forming fibrotic focus govern metastasis of invasive ductal carcinoma of the breast

We have already reported that invasive ductal carcinomas (IDCs) with fibrotic focus (FF) have more aggressive characteristics than those without FF. FF is composed of a mixture of fibroblasts and various amounts of collagen fibers, suggesting that highly proliferative fibroblasts forming FF increase the malignant potential of IDCs with FF. The purpose of this study was to examine whether there is a difference of proliferative activity of fibroblasts forming and not forming FF, which plays an important role in the tumor progression of IDCS: Two hundred three consecutive cases of IDC of the breast surgically treated at the National Cancer Center Hospital East formed the basis for this study. The proliferative activity of the fibroblasts forming the FF was immunohistochemically evaluated by using mouse MIB-1 monoclonal antibody against Ki-67 antigen. The MIB-1 labeling index (LI) is the percentage of fibroblasts forming FF that have positively stained nuclei, and 300 fibroblasts were counted in each FF. The significance of the proliferative activity of fibroblasts forming FF with regard to lymph node metastasis (LNM) or distant-organ metastasis (DOM) was compared with well-known prognostic parameters. Multivariate analysis demonstrated that high MIB-1 LI of fibroblasts forming FF significantly increased the relative risk of LNM and the hazard rate of DOM (P < .001 and P = .009). The present study indicated that the metastatic ability of IDCs with FF is highly dependent on the proliferative activity of the fibroblasts forming FF.

Genetic factors in the etiology of systemic sclerosis and Raynaud phenomenon

There is increasing evidence that genetic factors play important roles in susceptibility to and expression of systemic sclerosis (SSc), as well as primary Raynaud phenomenon. Familial aggregation for SSc, although infrequent (1.2%-1.5% of SSc families), has now been established, and when compared with population prevalence represents a significant risk factor for the disease and lays a firmer foundation for genetics in etiopathogenesis. Major histocompatibility complex class II alleles increase disease risk in some populations but are more strongly correlated with specific autoantibody profiles. Microchimerism influenced by human leukocyte antigen also remains an intriguing hypothesis. A variety of extracellular matrix genes, including fibrillin-1, have become additional candidates for contributing to what is likely a complex genetic disease. Reviewed here is evidence relating to these concepts, especially new data reported over the last year.

Proliferative activity of intratumoral fibroblasts is closely correlated with lymph node and distant organ metastases of invasive ductal carcinoma of the breast

Mitotic figures of fibroblasts are seen within invasive ductal carcinoma (IDC) of the breast. This suggests that the proliferative activity of fibroblasts may play an important role in IDC tumor progression. The purpose of this study was to examine whether the proliferative activity of fibroblasts can predict lymph node metastasis (LNM) or distant-organ metastasis (DOM) of IDCs. Two hundred four consecutive patients with IDC of the breast surgically treated at the National Cancer Center Hospital East constituted the basis of this study. Proliferative activity of fibroblasts was immunohistochemically evaluated by the mouse MIB-1 monoclonal antibody against Ki-67 antigen. The MIB-1 labeling index was the percentage of fibroblasts with positively stained nuclei, and fields for cell counting were selected in inner and outer areas within IDCs. In both areas, 300 fibroblasts were counted in each high-power field. The significance of proliferative activity of fibroblasts on LNM or DOM was compared with well-known prognostic parameters. Multivariate analyses demonstrated that a MIB-1 labeling index of more than 10% of fibroblasts in the inner area of IDCs significantly increased the relative risk of LNM and hazard rate of DOM (P < 0.001 and P = 0.007, respectively). The present study indicated that the metastatic ability of IDCs is closely dependent on proliferative activity of fibroblasts in the inner area.

Scleromyxedema

Scleromyxedema is a sclerotic variant of papular mucinosis, in which lichenoid papules and scleroderma-like features are present. We describe a patient with scleromyxedema with IgG type lambda chain paraprotein, a systemic sclerosis-like illness, and myositis. The patient's serum contained Scl 70 antibodies, characteristic of scleroderma. Electromyography showed signs of acute myositis and the creatine phosphokinase (CPK) level was elevated. Multiply passaged fibroblasts from the patient's skin lesions showed altered growth response in vitro. The patient was treated with cyclosporin (4 mg/kg/day) with improvement.

Expression of c-myb and B-myb oncogenes on myelofibrotic marrow fibroblasts

The term IMF (Idiopathic Myelofibrosis) refers to a primary bone marrow disease in which the normal haematopoietic bone marrow cells are for unknown reasons replaced by connective tissue. The pathogenesis of the disease has not been clarified yet. We have speculated that the increment of proliferation of bone marrow fibroblasts in IMF may be the consequence of the over-expression of some oncogenes, leading or contributing to the fibrosis via a cell amplification. Thus, we investigated the possible role of the c-myb and B-myb genes in IMF and control bone marrow fibroblasts in different culture conditions to evaluate proliferation parameters in the absence or presence of serum. Using the reverse transcriptase polymerase chain reaction technique, we demonstrated that the kinetics of induction was similar for both c-myb and B-myb during the proliferation of normal bone marrow fibroblasts. When compared to normal controls, cultured IMF fibroblasts showed more elevated values of c-myb and B-myb RNA; furthermore, after a 72 hours stimulation with serum, c-myb and B-myb messages remained relatively high in myelofibrotic fibroblasts. Finally, after serum starvation, c-myb and to a lesser extent B-myb RNA levels remained unusually high in IMF fibroblasts, while under the same experimental conditions c-myb and B-myb messages became virtually undetectable in normal bone marrow fibroblasts. To our knowledge this work represents the first description of an abnormal behavior of these genes in IMF fibroblasts.

C-myb, but not B-myb, upregulates type I collagen gene expression in human fibroblasts

C-myb and B-myb belong to the myb family of transcription factors. We have shown previously that c-myb is deregulated in fibroblasts from systemic sclerosis (scleroderma) patients relative to normal fibroblasts. Scleroderma fibroblasts are known to express elevated levels of collagen genes and transforming growth factor beta is known to be a pro-fibrotic cytokine and to induce transcription of type I collagen genes. We have therefore investigated the role of c-myb and B-myb in the regulation of type I collagen genes in response to transforming growth factor beta in normal human fibroblasts. We show that, in these cells, transforming growth factor beta treatment induces c-myb as well as collagen alpha1(I) and alpha2(I) gene expression, but not B-myb. Furthermore we demonstrate by cotransfection assays that c-myb can upregulate alpha1(I) and alpha2(I) collagen promoters by 6-10-fold whereas B-myb is inactive. The activity of c-myb on both type I collagen promoters requires a functional c-myb DNA binding domain suggesting a direct interaction between c-myb and these promoters. Indeed c-myb is active also on a 500 bp fragment of the alpha2(I) collagen promoter and can bind to this fragment in electrophoretic mobility shift assays. Finally, we show that anti-c-myb anti-sense treatment reduces alpha1(I) and to a lesser extent alpha2(I) collagen gene expression. These data strongly suggest that c-myb, but not B-myb, plays a direct role in the upregulation of type I collagen gene expression in response to transforming growth factor beta.

Increased expression of TGF-beta receptors by scleroderma fibroblasts: evidence for contribution of autocrine TGF-beta signaling to scleroderma phenotype

Scleroderma fibroblasts exhibit numerous phenotypic differences when compared with healthy skin fibroblasts. Some of these differences, in particular overexpression of collagen type I and other extracellular matrix proteins, parallel the effect of transforming growth factor-beta (TGF-beta) on dermal fibroblasts, suggesting that the scleroderma fibroblast phenotype may result from activation of autocrine TGF-beta signaling. To test this hypothesis we examined the role of TGF-beta Type I and Type II receptors in regulating collagen type I transcription. We have shown that overexpression of either Type I or Type II receptors significantly (3-4-fold) increases alpha2 (I) collagen promoter activity in transient transfection assays in dermal fibroblasts. Addition of anti-TGF-beta antibody abolished, whereas addition of plasmin enhanced, the stimulatory effect of receptor overexpression on collagen promoter activity, suggesting that this effect depends on autocrine TGF-beta. Moreover, these cotransfection experiments indicated that expression levels of TGF-beta receptors is a limiting factor in the autocrine regulation of collagen type I transcription by TGF-beta. Comparison of the TGF-beta receptor Type I and Type II mRA expression levels in scleroderma and normal fibroblasts have indicated elevated expression (2-fold) of both receptor types in scleroderma cells, which correlated with increased binding of TGF-beta. Significantly, elevated TGF-beta receptor levels correlated with elevated alpha2 (I) collagen mRNA levels. These results suggest that the elevated production of collagen type I by scleroderma fibroblasts results from overexpression of TGF-beta receptors.