Tenascin in breast cancer development--is epithelial tenascin a marker for poor prognosis?

The Role of Extracellular Matrix Proteins in Breast Cancer

The extracellular matrix is a structure composed of many molecules, including fibrillar (types I, II, III, V, XI, XXIV, XXVII) and non-fibrillar collagens (mainly basement membrane collagens: types IV, VIII, X), non-collagenous glycoproteins (elastin, laminin, fibronectin, thrombospondin, tenascin, osteopontin, osteonectin, entactin, periostin) embedded in a gel of negatively charged water-retaining glycosaminoglycans (GAGs) such as non-sulfated hyaluronic acid (HA) and sulfated GAGs which are linked to a core protein to form proteoglycans (PGs). This highly dynamic molecular network provides critical biochemical and biomechanical cues that mediate the cell–cell and cell–matrix interactions, influence cell growth, migration and differentiation and serve as a reservoir of cytokines and growth factors’ action. The breakdown of normal ECM and its replacement with tumor ECM modulate the tumor microenvironment (TME) composition and is an essential part of tumorigenesis and metastasis, acting as key driver for malignant progression. Abnormal ECM also deregulate behavior of stromal cells as well as facilitating tumor-associated angiogenesis and inflammation. Thus, the tumor matrix modulates each of the classically defined hallmarks of cancer promoting the growth, survival and invasion of the cancer. Moreover, various ECM-derived components modulate the immune response affecting T cells, tumor-associated macrophages (TAM), dendritic cells and cancer-associated fibroblasts (CAF). This review article considers the role that extracellular matrix play in breast cancer. Determining the detailed connections between the ECM and cellular processes has helped to identify novel disease markers and therapeutic targets.

Cell Intrinsic and Extrinsic Mechanisms of Caveolin-1-Enhanced Metastasis

Caveolin-1 (CAV1) is a scaffolding protein with a controversial role in cancer. This review will initially discuss earlier studies focused on the role as a tumor suppressor before elaborating subsequently on those relating to function of the protein as a promoter of metastasis. Different mechanisms are summarized illustrating how CAV1 promotes such traits upon expression in cancer cells (intrinsic mechanisms). More recently, it has become apparent that CAV1 is also a secreted protein that can be included into exosomes where it plays a significant role in determining cargo composition. Thus, we will also discuss how CAV1 containing exosomes from metastatic cells promote malignant traits in more benign recipient cells (extrinsic mechanisms). This ability appears, at least in part, attributable to the transfer of specific cargos present due to CAV1 rather than the transfer of CAV1 itself. The evolution of how our perception of CAV1 function has changed since its discovery is summarized graphically in a time line figure.

Caveolin-1-containing extracellular vesicles transport adhesion proteins and promote malignancy in breast cancer cell lines

Breast cancer is one of the most frequently diagnosed cancers and the leading cause of cancer-related deaths in women worldwide, whereby mortality is largely attributable to the development of distant metastasis. Caveolin-1 (CAV1) is a multifunctional membrane protein that is typically upregulated in the final stages of cancer and promotes migration and invasion of tumor cells. Elevated levels of CAV1 have been detected in extracellular vesicles (EVs) from advanced cancer patients. EVs are lipid enclosed vesicular structures that contain bioactive proteins, DNA and RNAs, which can be transferred to other cells and promote metastasis. Therefore, we hypothesized that CAV1 containing EVs released from breast cancer cells may enhance migration and invasion of recipient cells. EVs were purified from conditioned media of MDA-MB-231 wild-type (WT), MDA-MB-231 (shCAV1; possessing the plasmid pLKO.1 encoding a 'small hairpin' directed against CAV1) and MDA-MB-231 (shC) short hairpin control cells. Nanoparticle tracking analysis revealed an average particle size of 40-350 nm for all preparations. As anticipated, CAV1 was detected in MDA-MB-231 WT and shC EVs, but not in MDA-MB-231 (shCAV1) EVs. Mass spectrometry analysis revealed the presence of specific cell adhesion-related proteins, such as Cyr61, tenascin (TNC) and S100A9 only in WT and shC, but not in shCAV1 EVs. Importantly, EVs containing CAV1 promoted migration and invasion of cells lacking CAV1. We conclude that the presence of CAV1 in EVs from metastatic breast cancer cells is associated with enhanced migration and invasiveness of recipient cells in vitro, suggesting that intercellular communication promoted by EVs containing CAV1 will likely favor metastasis in vivo.

Fibroblasts in the Tumor Microenvironment: Shield or Spear?

Tumorigenesis is a complex process involving dynamic interactions between malignant cells and their surrounding stroma, including both the cellular and acellular components. Within the stroma, fibroblasts represent not only a predominant cell type, but also a major source of the acellular tissue microenvironment comprising the extracellular matrix (ECM) and soluble factors. Normal fibroblasts can exert diverse suppressive functions against cancer initiating and metastatic cells via direct cell-cell contact, paracrine signaling by soluble factors, and ECM integrity. The loss of such suppressive functions is an inherent step in tumor progression. A tumor cell-induced switch of normal fibroblasts into cancer-associated fibroblasts (CAFs), in turn, triggers a range of pro-tumorigenic signals accompanied by distraction of the normal tissue architecture, thus creating an optimal niche for cancer cells to grow extensively. To further support tumor progression and metastasis, CAFs secrete factors such as ECM remodeling enzymes that further modify the tumor microenvironment in combination with the altered adhesive forces and cell-cell interactions. These paradoxical tumor suppressive and promoting actions of fibroblasts are the focus of this review, highlighting the heterogenic molecular properties of both normal and cancer-associated fibroblasts, as well as their main mechanisms of action, including the emerging impact on immunomodulation and different therapy responses.

Extracellular matrix components in breast cancer progression and metastasis

The extracellular matrix (ECM) is composed of highly variable and dynamic components that regulate cell behavior. The protein composition and physical properties of the ECM govern cell fate through biochemical and biomechanical mechanisms. This requires a carefully orchestrated and thorough regulation considering that a disturbed ECM can have serious consequences and lead to pathological conditions like cancer. In breast cancer, many ECM proteins are significantly deregulated and specific matrix components promote tumor progression and metastatic spread. Intriguingly, several ECM proteins that are associated with breast cancer development, overlap substantially with a group of ECM proteins induced during the state of tissue remodeling such as mammary gland involution. Fibrillar collagens, fibronectin, hyaluronan and matricellular proteins are matrix components that are common to both involution and cancer. Moreover, some of these proteins have in recent years been identified as important constituents of metastatic niches in breast cancer. In addition, specific ECM molecules, their receptors or enzymatic modifiers are significantly involved in resistance to therapeutic intervention. Further analysis of these ECM proteins and the downstream ECM mediated signaling pathways may provide a range of possibilities to identify druggable targets against advanced breast cancer.

The niche under siege: novel targets for metastasis therapy

Metastasis is an inefficient process and most cancer cells fail to colonize secondary sites. There are several possible reasons for this. First, the nature of the infiltrating cells is important as a small population of cancer stem cells has been shown to have exclusive metastasis-initiating potential. Secondly, supportive niches are required to promote the outgrowth of disseminated tumour cells. Such niches are either produced prior to the arrival of cancer cells in the target organ or are induced ad hoc upon cell infiltration. Components of the extracellular matrix (ECM) have been found to play a role in establishing these niches. This has highlighted the importance of the ECM for metastatic progression, and suggests that such components may provide alternative targets for treatment of metastatic disease.

Regulation of tenascin expression in bone

Tenascins regulate cell interaction with the surrounding pericellular matrix. Within bone, tenascins C and W influence osteoblast adhesion and differentiation, although little is known about the regulation of tenascin expression. In this study we examined the effect of osteogenic differentiation, bone morphogenetic protein (BMP) and Wnt growth factors, and mechanical loading on tenascin expression in osteogenic cells. Osteogenic differentiation increased tenascin C (TnC), and decreased tenascin W (TnW), expression. Both growth factors and mechanical loading increased both TnC and TnW expression, albeit via distinct signaling mechanisms. Both BMP-2 and Wnt5a induction of tenascin expression were mediated by MAP kinases. These data establish a role for BMP, Wnts, and mechanical loading in the regulation of tenascin expression in osteoblasts.

Increased presence of stromal myofibroblasts and tenascin-C with malignant progression in canine mammary tumors

The aims of this study were to determine whether the appearance of stromal myofibroblasts and the expression of tenascin-C (Tn-C) correlate with the grade of malignancy in canine mammary tumors and to determine the main cellular source of Tn-C in these tumors. Single or double immunostaining using antibodies against α-smooth muscle actin (α-SMA) and Tn-C was performed on serial sections of normal canine mammary glands as well as those with lobular hyperplasia, simple adenoma, and simple carcinoma. Thirty-nine of 42 simple carcinomas (93%) exhibited stromal α-SMA-positive myofibroblasts and Tn-C expression. Only 6 of 11 cases of simple adenoma (55%) showed these changes, whereas no changes were observed in normal mammary gland tissue or cases of lobular hyperplasia. The distribution of stromal Tn-C correlated with the presence of myofibroblasts. However, Tn-C immunoreactivity was also occasionally observed in the basement membrane zone surrounding the myoepithelial layer in normal tissue, benign lesions, and tubulopapillary carcinomas. This pattern of staining was not related to the presence of myofibroblasts. The appearance of stromal myofibroblasts and expression of Tn-C were significantly correlated with higher histological grades of malignancy and vascular/lymphatic invasion in simple carcinomas. Stromal myofibroblasts appear to be a major cellular source of Tn-C and play an important role in the development of canine mammary tumors. The Tn-C expressed in the basement membrane zone of normal, hyperplastic, and neoplastic mammary tissue, which is likely produced by neighboring myoepithelial cells, may differ functionally from the Tn-C produced by myofibroblasts.

Lymph node status as a guide to selection of available prognostic markers in breast cancer: the clinical practice of the future?

Prognosticators evaluating survival in breast cancer vary in significance in respect to lymph node status. Studies have shown e.g. that HER2/neu immunohistochemistry or HER2/neu gene amplification analysis do perform well as prognosticators in lymph node positive (LN +) patients but are less valuable in lymph node negative (LN -) patients. We collected data from different studies and tried to evaluate the relative significance of different prognosticators in LN+/LN- patient groups. In LN+ patients HER2/neu and E-cadherin immunohistochemistry were the statistically most significant prognosticators followed by proliferation associated features (mitotic counts by SMI (standardised mitotic index) or MAI (mitotic activity index), or S-phase fraction). Bcl-2 immunohistochemistry was also significant but p53 and cystatin A had no significance as prognosticators. In LN- patients proliferation associated prognosticators (SMI, MAI, Ki-67 index, PCNA immunohistochemistry, S-phase fraction) are especially valuable and also Cathepsin D, cystatin A, and p53 are significant, but HER2/neu or bcl-2, or E-cadherin less significant or without significance. We find that in studies evaluating single prognosticators one should distinguish between prognosticators suitable for LN+ and LN- patients. This will allow the choice of best prognosticators in evaluating the prospects of the patient. The distinction between LN+ and LN- patients in this respect may also be of special value in therapeutic decisions.

Induction of tenascin-C by tumor-specific EWS-ETS fusion genes

Ewing sarcoma (ES) and peripheral primitive neuroectodermal tumors (PNETs) are associated with a chromosomal translocation resulting in a fusion of the amino-terminus of EWS with the DNA-binding domain of an ETS transcription factor (most commonly FLI1 or ERG). Although previous reports suggested that these chimera proteins would act as aberrant transcription factors, their downstream targets have not been fully elucidated. To identify downstream targets of these EWS-ETS fusion proteins, we introduced EWS-ETS fusion constructs into a human fibrosarcoma cell line, HT-1080, by retroviral transduction. Here we report that Tenascin-C (TNC) is induced to a significantly higher level in cells expressing EWS-ETSs than in cells expressing normal ETSs. Furthermore, through use of an antisense cDNA expression vector we show that expression of endogenous TNC mRNA and protein were reduced coordinately with attenuation of EWS-FLI1 fusion protein expression. A chromatin immunoprecipitation assay showed direct interaction between the TNC promoter and the EWS-FLI1 fusion protein in vivo. In addition, a luciferase reporter assay revealed that EWS-ETSs upregulated the TNC gene through four ETS binding sites in the TNC promoter. High levels of TNC expression were observed in a subset of ES cell lines (3 of 6) and primary tumors (4 of 6). Together with previous studies showing that TNC expression is involved in the invasive and malignant phenotype of several tumor types, our data suggest that the oncogenic effect of EWS-ETS may be mediated in part by upregulating of TNC expression.

Extracellular matrix components in breast carcinomas

A malignant process interferes with the normal 'programme' of extracellular matrix biosynthesis and can modify extensively the structure and composition of the matrix. This effect appears to be attributable to several processes such as direct production of some selected matrix macromolecules by malignant cells or indirectly by the production of factors by malignant cells interfering with the regulation of normal matrix production. Other possibilities may also exist, such as the direct action of an environmental carcinogen on otherwise normal mesenchymal cells. The result is a more or less profound modification of tissue structure and composition with possible feedback effects on the malignant process. Some examples will be discussed such as elastin production by some tumours as well as the biosynthesis of some other selected matrix macromolecules as tenascin and osteopontin by breast tumours. Although the detailed mechanisms of these specific matrix productions is not yet completely elucidated, the rapidly increasing knowledge on the regulation of specific matrix production process and deranged matrix production might represent a new area of crosstalk between cancer research and matrix biology.

Tenascin expression in normal, hyperplastic, and neoplastic endometrium

Tenascin (TN) is an extracellular matrix glycoprotein (ECM) that participates in embryogenesis and carcinogenesis. The aim of this study was to investigate immunohistochemically the expression of TN in the normal, hyperplastic, and neoplastic endometrium (endometrial adenocarcinoma). In the adenocarcinomas, the results were correlated with patient age, menopausal status, stage, grade, myometrial invasion, and vascular invasion. TN expression was studied in the following cases: proliferative endometrium (10 cases), early secretory endometrium (10), secretory endometrium (10), simple hyperplasia (15), complex hyperplasia (15), atypical hyperplasia (15), and endometrial adenocarcinomas (25). Staining of basal membranes and the cytoplasm of the stromal and epithelial cells was evaluated semiquantitatively. Positive staining was observed in the vascular and glandular basal membranes, stromal cells, and epithelial cells of proliferative, hyperplastic, and neoplastic endometrium. The difference in percentage of stained stromal cells between the neoplastic and the nonneoplastic (proliferative and hyperplastic) endometrium was significant (p<0.005). However, the percentage of stained epithelial cell area in hyperplasia was significantly higher than that of adenocarcinoma and functional endometrium (p<0.005). We conclude that TN is an extracellular matrix glycoprotein that plays a role in proliferation and possibly endometrial carcinogenesis.

Co-expression of tenascin-C and vimentin in human breast cancer cells indicates phenotypic transdifferentiation during tumour progression: correlation with histopathological parameters, hormone receptors, and oncoproteins

Loss of epithelial morphology and the acquisition of mesenchymal characteristics are typical for carcinoma cells in tumour progression. In human breast carcinomas, up-regulation of tenascin-C (TN-C) and vimentin (Vim) is frequently observed in cancer cells and correlates with increased malignancy. Thus, it is possible that TN-C is co-expressed with Vim, representing cancer cells that have undergone epithelial-mesenchymal transition (EMT). This study examined 128 breast carcinomas using immunohistochemical techniques to demonstrate that mammary cancer cells are a prominent source of both TN-C and Vim. Statistical analysis revealed a significant association between TN-C and Vim expression in cancer cells. TN-C expression also correlated positively with overexpression of c-erbB-2 oncoprotein and down-regulation of oestrogen receptors (ERs). Eleven human mammary cancer cell lines and two 'normal' cell lines were examined by western blotting and immunohistochemistry. Co-expression of TN-C and Vim was detected in the carcinosarcoma cell line HS 578T, SK-BR-3 (B), fibroblast-like MDA-MB-231 cells, and the myoepithelial cell line HBL 100. These findings suggest that TN-C and Vim, when co-expressed in mammary carcinoma cells, represent regulator genes likely to be involved in EMT during mammary carcinogenesis.

Tenascin expression and angiogenesis in breast cancers

The expression and the distribution of tenascin as well as the extent of blood vessel formation (angiogenesis) were investigated in 70 invasive human breast carcinomas. Formalin-fixed, paraffin-embedded specimens were stained with monoclonal antibody against tenascin-C (DAKO and Biogenex). Anti-CD31 antibody (Biogenex), an acknowledged marker of stromal angiogenesis, was used to detect endothelial cells. Tenascin immunostaining was positive in the tumours around the persisting normal ducts, around tumour-cell nests, in the neostroma, in some tumour cells, and it was found in or around vascular channels. Tumour vascularity was assessed by quantitative vascular grading (Chalkley point count) and was related to the localization and intensity of tenascin immunoreactivity. 19 tumours (27.1%) were scored as low, 35 (50%) as medium, and 16 (22.9%) as having a high vascular grade. The positive correlation between the vascular grade and the tenascin immunopositivity in tumour stroma was observed. Our results suggest that tenascin expression may be associated with endothelial cell activation and may play an important role in tumour angiogenesis.

Tenascin expression in primary and recurrent breast carcinomas and the effect of tenascin on breast tumor cell cultures

Tenascin is generally classified as an anti-adhesive protein. Many cells do not adhere to tenascin or if they adhere they do not spread. In this study we analysed the stromal expression of tenascin-C in primary, second primary and recurrent breast carcinomas and the ability of tenascin-C to stimulate the focal adhesion plaques in MDA-MB-435 breast carcinoma cell line. To assess the tenascin-C expression formalin-fixed, paraffin-embedded specimens of 20 specially selected breast carcinomas and their recurrences (14) or a second primary breast cancer of the same patient (6) were examined with immunohistochemical methods. We also studied the effect of tenascin-C on focal adhesion plaques added to MDA-MB-435 breast carcinoma cell line. During a median 2,9-year patient follow up 14 local recurrences and 6-second primary breast carcinomas developed in the 20 patients. In 3 cases a second recurrence occurred. The presence of tenascin in tumor cells, in the proliferating and some normal ducts, near to the tumor cell nests, in the stroma and in ductal carcinoma in situ component of the invasive carcinoma may suggest the role of tenascin played in tumor cell migration. Soluble tenascin added to the cell culture had minimal or no effect on focal adhesion plaques. Tenascin only seems not to be of prognostic value in predicting the local recurrence of breast cancer.

Ets transcription factors cooperate with Sp1 to activate the human tenascin-C promoter

Tenascin-C (TN-C), an extracellular matrix glycoprotein is expressed during embryonic development, but is present only at low levels in normal adult tissues. TN-C is re-expressed during wound healing, fibrotic diseases and in cancer. To better understand the mechanisms that control TN-C gene expression, we examined the regulation of the human TN-C promoter in human fibroblasts. We demonstrate that a short segment of the TN-C promoter between bp -133 and -27 contains three evolutionarily conserved Ets binding sites (EBS). These three EBSs bind in vitro expressed Fli1 protein and mediate transactivation of the TN-C gene by Fli1. Furthermore, two proximal EBSs contribute significantly to basal activity of the TN-C promoter. GABP, which is present in human fibroblast nuclear extracts, interacts with the two proximal EBSs. In addition, several Sp1 and Sp3 binding sites have been located in close proximity to the EBSs within this promoter region. The studies performed in Drosophila cells demonstrate that either Fli1 or GABPalpha+beta1 functionally interact with Sp1 resulting in a synergistic stimulation of the TN-C promoter activity. In conclusion, this study shows for the first time that the TN-C gene is regulated by Ets proteins, which together with Sp1 act as potent activators of TN-C expression.

Retinoic acid and 1,25-dihydroxyvitamin D3 inhibit tenascin-C expression in rat glioma C6 cells

Tenascin-C (Tn-C) is an extracellular matrix protein with growth-, invasive-, and angiogenesis-promoting activities. Tn-C is upregulated during wound healing, tumorigenesis, and other pathological conditions. Highly malignant gliomas with poor prognosis exhibit high levels of Tn-C expression. Here we demonstrate that Tn-C RNA expression in glioma C6 cells is inhibited in a dose-dependent manner by retinoic acid (RA) and 1,25-dihydroxyvitamin D3 (1,25-D3). No additive or synergistic effects were found. Inhibition is maximum 24 hr after RA or 1,25-D3 treatment, prior to a delayed cytotoxic effect starting at day 4-5 of treatment, and correlates with a reduction in the synthesis of Tn-C protein. Tn-C expression is also inhibited, but to a lesser extent by prostaglandin D2 (PGD2). Furthermore, both RA and 1,25-D3, but not PGD2 abolish the induction of Tn-C by the tumor promoter 12-O-tetradecanoyl phorbol 13-acetate. The inhibition of Tn-C expression might be relevant for the anti-cancer activity of RA and 1,25-D3.

Inhibition of tenascin-C expression in mammary epithelial cells by thyroid hormone

Multiple data suggest a relationship between thyroid hormone (triiodothyronine (T3)) and carcinogenesis. Studies on breast cancer have been inconclusive, suggesting contradictory effects of thyroid status and diseases. Recently, we reported that expression of the extracellular matrix glycoprotein tenascin-C is modulated by T3 during rat brain development. Because tenascin-C has been reported to have growth-, motility-, and angiogenic-promoting activities and to become upregulated during tumorigenesis in breast carcinoma and stromal cells, we analyzed the effects of T3 on tenascin-C expression in mammary epithelial cells. In this study, we showed that tenascin-C RNA expression was inhibited by T3 in normal un-transformed EpH4 mouse mammary epithelial cells expressing appropriate receptors. T3's action appeared to be due to a decreased half-life of the tenascin-C mRNA, with a maximum effect (85% at 100 nM) 48 h after addition. T3 also downregulated tenascin-C in the human mammary tumor cell line SKBR-3, which expresses endogenous thyroid receptors. Immunoprecipitation experiments confirmed that tenascin-C protein content was also decreased by T3 in EpH4 cells (70% reduction at 100 nM). Dexamethasone had a similar inhibitory effect (70% at 100 nM), whereas estradiol, the antiestrogen ICI 164,384, progesterone, and all-trans retinoic acid did not alter tenascin-C expression. Our data demonstrate an inhibitory action of T3 on tenascin-C expression in mammary epithelial cells that may play a role in the physiological regulation of this gene and in neoplastic processes.

An odyssey from breast to bone: multi-step control of mammary metastases and osteolysis by matrix metalloproteinases

Development of metastases distant to the primary site of solid tumors marks late stages of tumor progression. Almost all malignant mammary tumors are carcinomas arising from the breast epithelium, but the morphological and molecular alterations in the mammary stroma surrounding the premalignant and the growing tumor contribute to its conversion into neoplastic tissue. Two parameters are critical for initiation of the metastatic process and access of tumor cells to the circulation. These are the ability of tumor cells to invade the basement membrane and the stroma, and the neovascularization of breast tumor tissue. A major site for development of distant metastases is the skeleton. After colonizing the bone, tumor cells promote a cascade of events leading to recruitment of osteoclasts and subsequent osteolytic bone destruction. A ubiquitous theme of neoplastic progression of breast tumors is the overproduction of matrix metalloproteinases. In this review, we summarize the recent insights into the functional consequences of matrix metalloproteinase expression and activation during malignant conversion in the breast, and after bone colonization. The current literature supports the hypothesis that matrix metalloproteinases play a key role in the metastatic expansion of most, if not all, mammary tumors and in the ensuing bone loss.

Tenascin-C expression in invasion border of early breast cancer: a predictor of local and distant recurrence

We have recently demonstrated an association between distant metastasis and the expression of the extracellular matrix glycoprotein tenascin-C (Tn-C) in the invasion border of small axillary node-negative breast carcinomas. Our purpose was to assess the relationship between the expression of Tn-C in the tumour invasion border and several histopathological and biological variables and to compare their usefulness in predicting local and distant disease recurrences. The original patient group consisted of 143 women with axillary node-negative breast cancer (one bilateral) treated with breast-conserving surgery and post-operative radiotherapy, and followed for a median of 8 years. Because of the small number of recurrences an additional group of 15 similarly treated women with recurrent breast cancer was also studied. The size of the tumour, its histology, including a possible intraductal component, and grade were re-evaluated. The expression of erbB-2, p53, Ki-67 and Tn-C was evaluated by immunohistochemistry. Ploidy and S-phase fraction (SPF) were assessed by flow cytometry. The only statistically significant prognostic factor for local recurrence was Tn-C expression in the invasion border. For metastasis Ki-67 positivity, tumour size and Tn-C expression in the invasion border were statistically significant, but Ki-67 positivity was the only independent prognostic factor. Tn-C expression in the invasion border was associated with a higher proliferation rate measured by Ki-67 and SPF, which is consistent with the suggested growth-promoting activity of Tn-C. Tn-C may be a useful marker in selecting patients for adjuvant therapies to reduce the rate of both local and distant cancer recurrences.

Migration of breast epithelial cells on Laminin-5: differential role of integrins in normal and transformed cell types

We examined the role of Laminin-5 (Ln-5) an extracellular matrix component of breast gland basement membrane, in supporting migration of normal (HUMEC), immortalized (MCF-10A), and malignant breast epithelial cells that exhibit different degrees of metastatic potential (MDA-MB-435>MDA-MB-231>MCF-7). HUMEC, MCF-10A, and MCF-7 cells all adhered to purified Ln-5 through the alpha3beta1 integrin receptor in adhesion assays. However, HUMEC and MCF-10A cells remained statically adherent, while MCF-7 cells migrated on Ln-5 in Transwell and colloidal gold displacement assays. Anti-alpha3 integrin antibodies blocked migration of MCF-7 cells on Ln-5. MDA-MB-231 and MDA-MB-435 cells bound and migrated on Ln-5 through a beta1 integrin receptor that is insensitive to antibodies that block the function of alpha1, alpha2, alpha3, alpha4, alpha5, alpha6, and alphaV integrin subunits. Migration of all cell types tested was blocked by CM6, a monoclonal antibody directed to a cell adhesion site on the alpha3 chain of Ln-5. Thus, Ln-5 may play an important role in regulating adhesion and migration in normal and transformed breast epithelium. Our results indicate that the type of integrin utilized by breast cells to interact with Ln-5, as well as its functional state, may determine whether cells will be statically adherent or migratory on Ln-5.

Expression of periglandular tenascin-C and basement membrane laminin in normal prostate, benign prostatic hyperplasia and prostate carcinoma

OBJECTIVE

To evaluate the structural relationship of the distribution between tenascin (tenascin-C, an extra-cellular matrix glycoprotein involved in stromal-epithelial interactions in both normal and pathological conditions) and laminin, an important component of the basement membrane, in normal and neoplastic human prostate, and to establish whether changes in the basement membrane are accompanied by changes in tenascin staining.

MATERIALS AND METHODS

Seventy-five snap-frozen prostate samples representing normal glands, nodular benign prostatic hyperplasia and prostate carcinoma were stained for tenascin. From these, 15 samples were selected for dual-immunofluorescence staining and a confocal laser scan microscope was used to simultaneously visualize tenascin and laminin immunoreactivity.

RESULTS

Tenascin was expressed in the extracellular matrix, mainly at the periphery of the glands, in tumour foci and blood vessels. In cases with intact basement membranes, e.g. normal glands and hyperplastic lesions, tenascin expression was weak. Low- and moderate-grade tumours were characterized by strong tenascin expression, while laminin expression was weak and/or showed discontinuities, indicating disturbances in basement membrane composition. High-grade tumours had sparse tenascin staining and a marked loss of laminin immunoreactivity.

CONCLUSION

These results indicate that periglandular tenascin expression correlates with the integrity of the basement membrane in the human prostate. By influencing stromal-epithelial interactions, tenascin may play a role in maintaining tissue homeostasis in the prostate.

Tenascin pattern of expression and established prognostic factors in invasive breast carcinoma

BACKGROUND AND OBJECTIVES

Immunohistochemical methods were used to study Tenascin (TN) expression in invasive duct cell carcinoma (IDCC) of the breast and its established prognostic factors.

METHODS

We studied 115 patients with IDCC. The mean patient age was 62 years; all tumors were graded according to Scarf-Bloom and Richardson. Complete survival information was available for all patients (median follow-up 65 months). Formalin-fixed, paraffin-embedded archival tissue from all 115 IDCC were immunostained with monoclonal mouse Anti-Human Tenascin (DAKO-TN2M636; 1/50 dilution). Positivity was recorded on a scale of 0-4 for percentage of TN staining in the tumor stroma.

RESULTS

TN showed thick bands around advancing tumor nests and in poorly differentiated tumors, TN fibers had an interstitial pattern surrounding single tumor cells. TN score was significantly positively correlated with high nuclear grade (P < 0.05), histologic grade (P < 0.01), mitotic grade (P < 0.005), and combined grade (P < 0.01). TN score did not correlate with long-term survival or with other prognostic factors studied.

CONCLUSIONS

TN expression was more prominent in tumors with a high combined histologic grade. Our results may suggest that while TN may play a role in limiting tumor spread as proposed by other studies, it may not represent a prognostic factor in invasive breast carcinoma.

1,25-Dihydroxyvitamin D3 inhibits tenascin-C expression in mammary epithelial cells

Tenascin-C is an extracellular matrix protein with growth-, invasion- and angiogenesis-promoting activities. Tenascin-C is upregulated in breast carcinoma and stromal cells, and in many other cell types during tumorigenesis. We demonstrate that tenascin-C RNA expression is inhibited by 1,25-dihydroxyvitamin D3 (1,25-D3) in a variety of mouse and human mammary epithelial cell lines exhibiting normal or malignant phenotype. In EpH4 cells, the inhibition is maximum 24 h after 1,25-D3 treatment and correlates with a dose-dependent reduction in the synthesis of tenascin-C protein. Furthermore, 1,25-D3 also abolishes the induction of tenascin-C by serum or the tumor promoter 12-O-tetradecanoyl phorbol 13-acetate. The inhibition of tenascin-C expression may be relevant for the anticancer activity of 1,25-D3.

Expression of tenascin-C by human endometrial adenocarcinoma and stroma cells: heterogeneity of splice variants and induction by TGF- b

Localization of tenascin-C in vivo and cell culture experiments in vitro have provided evidence for stromal production of tenascin-C in malignant tumors of a variety of organs. Here we raised the question of whether the mesenchymal stroma in the case of endometrial adenocarcinoma is the unique source of tenascin-C. Therefore, the expression of tenascin-C mRNA by human endometrial adenocarcinoma cells and endometrial stroma cells was investigated. Several preparations of endometrial stroma cells produced tenascin-C mRNA. Using a serum-free defined cell culture medium, production of tenascin-C mRNA could be increased by adding either serum or 20 ng TGF- beta /mL to the cell culture medium. Reverse transcriptase polymerase chain reaction analysis revealed that five out of six endometrial adenocarcinoma cell lines produced tenascin-C mRNA. Northern blot experiments and ribonuclease protection assays provided evidence that the number of copies of tenascin-C mRNA was small. Analysis of expressed splice variants by reverse transcriptase polymerase chain reaction analysis revealed the abundance of one major splice variant that lacked all potential alternatively spliced fibronectin type-III-like repeats. Regarding larger splice variants, all fragment sizes that could theoretically originate from seven alternatively spliced fibronectin type-III-like repeats were observed. Evaluating relative signal intensities, the splice variants containing a single fibronectin type-III-like repeat and the variant possessing all but one alternatively spliced repeats were most frequent. In summary, evidence is provided that tenascin-C can originate from both tissue compartments of the human endometrium stroma and (tumor) epithelium. Splice variant analysis revealed a high number of splice variants and a relative high proportion of variants that have so far been regarded as minor constituents of expressed tenascin-C. Key words: gene expression, splice variant analysis, extracellular matrix, endometrial cancer, growth factors.

Multicellular origin of tenascin in skin tumors--an in situ hybridization study

Tenascin mRNA expression was studied by an in situ hybridization method in 27 skin tumors. Tenascin synthesis was increased in all skin tumors when compared to uninvolved skin but there was variation in the site of cellular synthesis between different types of tumors. In melanocytic nevi and precancerous keratinocyte lesions, tenascin seemed to be of epidermal or stromal origin. In basal cell carcinoma, squamous cell carcinoma and malignant melanoma, there was tenascin synthesis also in tumor cells. These findings are in concordance with earlier studies which suggest a role of tenascin as an anti-adhesive and motility-promoting factor in malignant skin tumors.

Expression of tenascin in invasion border of early breast cancer correlates with higher risk of distant metastasis

Tenascin (Tn) is an extracellular matrix glycoprotein transiently expressed in epithelial-mesenchymal interaction areas during embryogenesis. Tn is expressed in a limited manner in adult tissues but emerges during wound healing and tumorigenesis. We have studied Tn expression by immunohistochemistry in 137 small node-negative breast cancers treated with breast-conserving surgery and post-operative radiotherapy during 1985-1989. None of the patients had undergone any adjuvant hormonal therapy or chemotherapy. Stromal Tn expression itself could not predict distant metastasis. However, Tn staining in the area of the invasion border seemed to be a strong predictor of distant metastasis, with an estimated 5-year metastasis-free survival (MFS) of 85% in Tn-positive cases compared to 98% in Tn-negative ones. The prognostic impact of Tn in the invasion border on MFS was stronger than that of tumour size and grade. This staining appears to be a useful adjunct for the estimation of breast-cancer metastasis.