Epithelial induction of stromal tenascin in the mouse mammary gland: from embryogenesis to carcinogenesis

Local accumulation of extracellular matrix regulates global morphogenetic patterning in the developing mammary gland

The tree-like pattern of the mammary epithelium is formed during puberty through a process known as branching morphogenesis. Although mammary epithelial branching is stochastic and generates an epithelial tree with a random pattern of branches, the global orientation of the developing epithelium is predictably biased along the long axis of the gland. Here, we combine analysis of pubertal mouse mammary glands, a three-dimensional (3D)-printed engineered tissue model, and computational models of morphogenesis to investigate the origin and the dynamics of the global bias in epithelial orientation during pubertal mammary development. Confocal microscopy analysis revealed that a global bias emerges in the absence of pre-aligned networks of type I collagen in the fat pad and is maintained throughout pubertal development until the widespread formation of lateral branches. Using branching and annihilating random walk simulations, we found that the angle of bifurcation of terminal end buds (TEBs) dictates both the dynamics and the extent of the global bias in epithelial orientation. Our experimental and computational data demonstrate that a local increase in stiffness from the accumulation of extracellular matrix, which constrains the angle of bifurcation of TEBs, is sufficient to pattern the global orientation of the developing mammary epithelium. These data reveal that local mechanical properties regulate the global pattern of mammary epithelial branching and may provide new insight into the global patterning of other branched epithelia.

The Cellular Organization of the Mammary Gland: Insights From Microscopy

Despite rapid advances in our knowledge of the cellular heterogeneity and molecular regulation of the mammary gland, how these relate to 3D cellular organization remains unclear. In addition to hormonal regulation, mammary gland development and function is directed by para- and juxtacrine signaling among diverse cell-types, particularly the immune and mesenchymal populations. Precise mapping of the cellular landscape of the breast will help to decipher this complex coordination. Imaging of thin tissue sections has provided foundational information about cell positioning in the mammary gland and now technological advances in tissue clearing and subcellular-resolution 3D imaging are painting a more complete picture. In particular, confocal, light-sheet and multiphoton microscopy applied to intact tissue can fully capture cell morphology, position and interactions, and have the power to identify spatially rare events. This review will summarize our current understanding of mammary gland cellular organization as revealed by microscopy. We focus on the mouse mammary gland and cover a broad range of immune and stromal cell types at major developmental stages and give insights into important tissue niches and cellular interactions.

Mesenchymal proteases and tissue fluidity remodel the extracellular matrix during airway epithelial branching in the embryonic avian lung

Reciprocal epithelial-mesenchymal signaling is essential for morphogenesis, including branching of the lung. In the mouse, mesenchymal cells differentiate into airway smooth muscle that wraps around epithelial branches, but this contractile tissue is absent from the early avian lung. Here, we have found that branching morphogenesis in the embryonic chicken lung requires extracellular matrix (ECM) remodeling driven by reciprocal interactions between the epithelium and mesenchyme. Before branching, the basement membrane wraps the airway epithelium as a spatially uniform sheath. After branch initiation, however, the basement membrane thins at branch tips; this remodeling requires mesenchymal expression of matrix metalloproteinase 2, which is necessary for branch extension but for not branch initiation. As branches extend, tenascin C (TNC) accumulates in the mesenchyme several cell diameters away from the epithelium. Despite its pattern of accumulation, TNC is expressed exclusively by epithelial cells. Branch extension coincides with deformation of adjacent mesenchymal cells, which correlates with an increase in mesenchymal fluidity at branch tips that may transport TNC away from the epithelium. These data reveal novel epithelial-mesenchymal interactions that direct ECM remodeling during airway branching morphogenesis.

Prenatal Mammary Gland Development in the Mouse: Research Models and Techniques for Its Study from Past to Present

Mammary gland development starts during prenatal life, when at designated positions along the ventrolateral boundary of the embryonic or fetal trunk, surface ectodermal cells coalesce to form primordia for mammary glands, instead of differentiating into epidermis. With the wealth of genetically engineered mice available as research models, our understanding of the prenatal phase of mammary development has recently greatly advanced. This understanding includes the recognition of molecular and mechanistic parallels between prenatal and postnatal mammary morphogenesis and even tumorigenesis, much of which can moreover be extrapolated to human. This makes the murine embryonic mammary gland a useful model for a myriad of questions pertaining to normal and pathological breast development. Hence, unless indicated otherwise, this review describes embryonic mammary gland development in mouse only, and lists mouse models that have been examined for defects in embryonic mammary development. Techniques that originated in the field of developmental biology, such as explant culture and tissue recombination, were adapted specifically to research on the embryonic mammary gland. Detailed protocols for these techniques have recently been published elsewhere. This review describes how the development and adaptation of these techniques moved the field forward from insights on (comparative) morphogenesis of the embryonic mammary gland to the understanding of tissue and molecular interactions and their regulation of morphogenesis and functional development of the embryonic mammary gland. It is here furthermore illustrated how generic molecular biology and biochemistry techniques can be combined with these older, developmental biology techniques, to address relevant research questions. As such, this review should provide a solid starting point for those wishing to familiarize themselves with this fascinating and important subdomain of mammary gland biology, and guide them in designing a relevant research strategy.

Transcriptional regulation of tenascin genes

Extracellular matrix proteins of the tenascin family resemble each other in their domain structure, and also share functions in modulating cell adhesion and cellular responses to growth factors. Despite these common features, the 4 vertebrate tenascins exhibit vastly different expression patterns. Tenascin-R is specific to the central nervous system. Tenascin-C is an “oncofetal” protein controlled by many stimuli (growth factors, cytokines, mechanical stress), but with restricted occurrence in space and time. In contrast, tenascin-X is a constituitive component of connective tissues, and its level is barely affected by external factors. Finally, the expression of tenascin-W is similar to that of tenascin-C but even more limited. In accordance with their highly regulated expression, the promoters of the tenascin-C and -W genes contain TATA boxes, whereas those of the other 2 tenascins do not. This article summarizes what is currently known about the complex transcriptional regulation of the 4 tenascin genes in development and disease.

Can stroma reaction predict cancer lethality?

Stromal features in carcinomas may provide a relatively consistent means to stratify patients afflicted with solid tumors. Stroma-derived transcriptome signatures can now be used to make predictions about patient survival, suggesting the potential for their clinical application in precision medicine to predict disease progression and emergence of therapeutic resistance.

Mammary stroma in development and carcinogenesis

Mammary glands of adult human females are secretory organs comprised of interdependent epithelial and mesenchymal cells. These cells constitute an assemblage of collecting ducts that end in terminal duct lobular units with hollow alveolar ductules that can differentiate to produce and expel milk. Systemic and maternal hormones, autocrine and paracrine growth factors, and cytokines regulate virtually all phases of mammary gland development. During organogenesis, epithelial and mesenchymal cells interact to form precursors of the parenchyma and stroma in the mature gland. Organogenesis precedes five stages of postnatal development: puberty, pregnancy, lactation, involution, and menopause. Each stage requires a specific set of morphogenetic changes in glandular structure and function. Cycles of cell proliferation, differentiation, and involution may recur until menopause. In addition, physiological responses such as inflammation and pathological events such as tumorigenesis are remarkable for their similarities to embryonic morphogenesis. Here we take a succinct look at the ever-improving understanding of stroma-epithelial interactions and mesenchyme function in mammary gland biology.

Parathyroid hormone-related protein specifies the mammary mesenchyme and regulates embryonic mammary development

Parathyroid Hormone related Protein (PTHrP) is a critical regulator of mammary gland morphogenesis in the mouse embryo. Loss of PTHrP, or its receptor, PTHR1, results in arrested mammary buds at day 15 of embryonic development (E15). In contrast, overexpression of PTHrP converts the ventral epidermis into hairless nipple skin. PTHrP signaling appears to be critical for mammary mesenchyme specification, which in turn maintains mammary epithelial identity, directs bud outgrowth, disrupts the male mammary rudiment and specifies the formation of the nipple. In the embryonic mammary bud, PTHrP exerts its effects on morphogenesis, in part, through epithelial-stromal crosstalk mediated by Wnt and BMP signaling. Recently, PTHLH has been identified as a strong candidate for a novel breast cancer susceptibility locus, although PTHrP's role in breast cancer has not been clearly defined. The effects of PTHrP on the growth of the embryonic mammary rudiment and its invasion into the dermis may, in turn, have connections to the role of PTHrP in breast cancer.

The role of the tumor microenvironment in regulating angiogenesis

The tumor-associated stroma has been shown to play a significant role in cancer formation. Paracrine signaling interactions between epithelial tumor cells and stromal cells are a key component in the transformation and proliferation of tumors in several organs. Whereas the intracellular signaling pathways regulating the expression of several pro- and antiangiogenic proteins have been well characterized in human cancer cells, the intercellular signaling that takes place between tumor cells and the surrounding tumor-associated stroma has not been as extensively studied with regard to the regulation of angiogenesis. In this chapter we define the key players in the regulation of angiogenesis and examine how their expression is regulated in the tumor-associated stroma. The resulting analysis is often seemingly paradoxical, underscoring the complexity of intercellular signaling within tumors and the need to better understand the environmental context underlying these signaling mechanisms.

Transcriptome analysis of embryonic mammary cells reveals insights into mammary lineage establishment

INTRODUCTION

The mammary primordium forms during embryogenesis as a result of inductive interactions between its constitutive tissues, the mesenchyme and epithelium, and represents the earliest evidence of commitment to the mammary lineage. Previous studies of embryonic mouse mammary epithelium indicated that, by mid-gestation, these cells are determined to a mammary cell fate and that a stem cell population has been delimited. Mammary mesenchyme can induce mammary development from simple epithelium even across species and classes, and can partially restore features of differentiated tissue to mouse mammary tumours in co-culture experiments. Despite these exciting properties, the molecular identity of embryonic mammary cells remains to be fully characterised.

METHODS

Here, we define the transcriptome of the mammary primordium and the two distinct cellular compartments that comprise it, the mammary primordial bud epithelium and mammary mesenchyme. Pathway and network analysis was performed and comparisons of embryonic mammary gene expression profiles to those of both postnatal mouse and human mammary epithelial cell sub-populations and stroma were made.

RESULTS

Several of the genes we have detected in our embryonic mammary cell signatures were previously shown to regulate mammary cell fate and development, but we also identified a large number of novel candidates. Additionally, we determined genes that were expressed by both embryonic and postnatal mammary cells, which represent candidate regulators of mammary cell fate, differentiation and progenitor cell function that could signal from mammary lineage inception during embryogenesis through postnatal development. Comparison of embryonic mammary cell signatures with those of human breast cells identified potential regulators of mammary progenitor cell functions conserved across species.

CONCLUSIONS

These results provide new insights into genetic regulatory mechanisms of mammary development, particularly identification of novel potential regulators of mammary fate and mesenchymal-epithelial cross-talk. Since cancers may represent diseases of mesenchymal-epithelial communications, we anticipate these results will provide foundations for further studies into the fundamental links between developmental, stem cell and breast cancer biology.

Integrated morphodynamic signalling of the mammary gland

The mammary gland undergoes a spectacular series of changes as it develops, and maintains a remarkable capacity to remodel and regenerate for several decades. Mammary morphogenesis has been investigated for over 100 years, motivated by the dairy industry and cancer biologists. Over the past decade, the gland has emerged as a major model system in its own right for understanding the cell biology of tissue morphogenesis. Multiple signalling pathways from several cell types are orchestrated together with mechanical cues and cell rearrangements to establish the pattern of the mammary gland. The integrated mechanical and molecular pathways that control mammary morphogenesis have implications for the developmental regulation of other epithelial organs.

Expression of tenascin-C and its isoforms in the breast

Tenascin-C (TNC) is an extracellular matrix glycoprotein which is frequently up-regulated in a variety of pathological conditions including chronic inflammation and cancer. TNC has been implicated in the modulation of cell migration, proliferation, invasion and angiogenesis. Multiple isoforms of TNC can be generated through the alternative splicing of nine exons located in the fibronectin type III region of the molecule. The profile of isoforms expressed differs between cancers and normal breast, with the fully truncated TNC isoform being predominant in normal and benign tissues and higher molecular weight isoforms induced predominantly in cancer. The addition of extra domains within the fibronectin type III repeat domain greatly affects TNC function with multiple exon combinations available for splicing. Exons 14 and 16 are considered to be tumour-associated and have been shown to affect breast cell line invasion and growth in vitro to a greater extent than the full-length TNC isoform. This mini review will provide a summary of the literature to date regarding the expression of TNC isoforms in the breast and also discuss more recent developments in the field regarding exon AD1.

Crosstalk between the p190-B RhoGAP and IGF signaling pathways is required for embryonic mammary bud development

P190-B RhoGAP (p190-B, also known as ARHGAP5) has been shown to play an essential role in invasion of the terminal end buds (TEBs) into the surrounding fat pad during mammary gland ductal morphogenesis. Here we report that embryos with a homozygous p190-B gene deletion exhibit major defects in embryonic mammary bud development. Overall, p190-B-deficient buds were smaller in size, contained fewer cells, and displayed characteristics of impaired mesenchymal proliferation and differentiation. Consistent with the reported effects of p190-B deletion on IGF-1R signaling, IGF-1R-deficient embryos also displayed a similar small mammary bud phenotype. However, unlike the p190-B-deficient embryos, the IGF-1R-deficient embryos exhibited decreased epithelial proliferation and did not display mesenchymal defects. Because both IGF and p190-B signaling affect IRS-1/2, we examined IRS-1/2 double knockout embryonic mammary buds. These embryos displayed major defects similar to the p190-B-deficient embryos including smaller bud size. Importantly, like the p190-B-deficient buds, proliferation of the IRS-1/2-deficient mesenchyme was impaired. These results indicate that IGF signaling through p190-B and IRS proteins is critical for mammary bud formation and ensuing epithelial-mesenchymal interactions necessary to sustain mammary bud morphogenesis.

The mesenchyme in cancer therapy as a target tumor component, effector cell modality and cytokine expression vehicle

Tissues and organs harbor a component of supportive mesenchymal stroma. The organ stroma is vital for normal functioning since it expresses factors instructing growth and differentiation along with molecules that restrain these processes. Similarly, the growth of tumors is strictly dependent on the tumor stroma. This review first discusses the possibility of developing tools to block the propagation of the tumor-associated stroma, that may halt tumor progression. It further describes how the tropism of mesenchymal stroma to tumor sites may be utilized to cause regression of the cancerous tissue. Mesenchyme can be genetically modified to overexpress specific regulatory molecules with known effects on specific tumors, such as interferon beta, studied in the context of melanoma and glioma and activin A, a transforming growth factor beta cytokine, examined in multiple myeloma. These studies point to the possibility that genetically modified mesenchymal cells may be used as a therapeutic modality for incurable human diseases. It is proposed that further development of methods of tumor stroma targeting, or alternatively the use of stromal mesenchyme as a cell or cell/gene therapy modalities, may yield novel clinical tools for the treatment of human cancers.

Modulation of response to tumor therapies by the extracellular matrix

The composition of the extracellular matrix in tumors is vastly different from that found in the normal tissue counterparts. As the extracellular matrix can signal to cells via integrin binding and activation, which is known to modulate cell proliferation, survival and migration, it may influence the response of both tumor and endothelial cells to anticancer therapies. Certain tumor-associated extracellular matrix proteins have been shown to confer resistance to chemotherapeutic drugs, radiation and anti-angiogenic factors. The current literature regarding this phenomenon and the potential therapeutic modalities to overcome extracellular matrix-induced resistance will be discussed.

Tenascin-C expression in Merkel cell carcinoma lymph node metastasis

Expression of tenascin-C (Tn-C) has been shown to correlate with invasion and metastasis in Merkel cell carcinoma (MCC). Cytokeratin-20 (CK-20) is used in differential diagnostics of the primary tumour. The aim of this study was to demonstrate the expression of Tn-C in MCC lymph node metastases. Immunohistochemical staining was performed for five metastatic lymph nodes using a monoclonal antibody against Tn-C and CK-20. All five metastatic lymph nodes expressed Tn-C. The expression concentrated around the vascular structures, invasion borders and fibrotic septae. One of the metastatic lymph nodes was strongly positive for CK-20 while the others showed a focal or negative pattern. The normal lymphoid tissue was negative for Tn-C. Tn-C detected metastatic MCC tissue within the lymph nodes undisputedly. There was a clear distinction between the metastatic and normal lymphatic tissue. Furthermore, invasion to the surrounding tissue was easily demonstrated. Contrary to previous studies, CK-20 expression seemed to fluctuate.

Histochemical and immunohistochemical evaluation of gingival collagen and metalloproteinases in peri-implantitis

The extra-cellular matrix of the gingival tissue plays an important role in the homeostasis of dental implants. In this work we have studied immunohistochemically the distribution of collagen I-III-IV-V, tenascin, metalloproteinases (MMP) 1-3-8-13 and TIMP-1 in three groups of patients: (1) subjects with natural teeth (healthy periodontal tissue), (2) subjects with normal peri-implant mucosa and (3) subjects with clinically evident peri-implantitis. The immunolabelling for collagen I-III-IV showed a similar pattern in all three groups. The labelling for collagen V increased in lamina propria of healthy peri-implant tissue and peri-implantitis. Tenascin immunolabelling in healthy and peri-implant tissues was scattered in lamina propria. In peri-implantitis tenascin immunolabelling increased mainly near to the basal lamina. The MMP-1-3-8 and TIMP-1 immunolabelling were very faint and localized in the stroma in all three groups. In healthy and peri-implant tissues MMP-13 immunolabelling was found in the lamina propria whereas in peri-implantitis MMP-13 immunolabelling was also in epithelium. On the whole, these data suggest that in the extracellular matrix of peri-implantitis there are alterations of collagen V, tenascin and MMP-13 patterns.

Functional interface between cathepsins and growth factors in the kidney development

During kidney development many proteases are involved with the remodeling process of the extracellular matrix (ECM) during nephrogenesis. This study used embryonic kidneys culture, tridimensional cell culture, and reverse transcriptase-polymerase chain reaction (RT-PCR) techniques in order to investigate the expression of cathepsins S (CS) and cathepsin H (CH) during metanephrogenesis and their functional interface with hepatic growth factor (HGF) and nerve growth factor (NGF). Results have shown that cathepsin S has been expressed early than the cathepsin H in the nephrogenesis. NGF antibody in the embryonic kidney cultures, in a dose-dependent mechanism inhibited the CS but not CH genic expression by RT-PCR. The tridimensional cells culture with MDCK and IMCD cells confirmed the interface between HGF and CS and CH once their inhibitors added to the culture, reduced the fancy branching formation induced by this growth factor. In summary, this study suggests that CS and CH are differently expressed during nephrogenesis and also that they are involved with the tubulogenesis probably mediating specific growth factors such as NGF and HGF.

Tenascin-C in primary Merkel cell carcinoma

BACKGROUND/AIMS

Merkel cell carcinoma (MCC) is a rare malignant cutaneous neuroendocrine tumour that mostly affects the elderly. It shows rapid progression of the primary tumour, together with a vertical growth pattern into the underlying subcutaneous tissue. Metastatic dissemination to regional lymph nodes is early and frequent. Tenascin-C (Tn-C) is a large extracellular matrix glycoprotein that is expressed in various benign and malignant processes. Expression of Tn-C is also associated with invasion and cellular proliferation, and is often downregulated in fully evolved advanced carcinomas. In previous studies, Tn-C expression correlated with prognosis in tumours of different origin.

METHODS

Immunohistochemistry was used to investigate the expression of Tn-C in 25 MCC specimens and to evaluate the prognostic importance of this glycoprotein.

RESULTS

Seventeen samples expressed Tn-C. Staining was mainly seen in the invasion borders and within the connective tissue septae inside the tumours. The expression of Tn-C correlated significantly with large tumour size. There was also frequent expression of Tn-C in primary tumours with metastatic dissemination. Most of the Tn-C negative samples were of small size.

CONCLUSIONS

Tn-C expression seems to increase with tumour size and malignant behaviour. Expression was slightly enhanced in tumours with high proliferative indices. Expression is seen mainly in areas of invasive growth and, in this respect, resembles that of other invasive tumours.

Integrin signalling during tumour progression

During progression from tumour growth to metastasis, specific integrin signals enable cancer cells to detach from neighbouring cells, re-orientate their polarity during migration, and survive and proliferate in foreign microenvironments. There is increasing evidence that certain integrins associate with receptor tyrosine kinases (RTKs) to activate signalling pathways that are necessary for tumour invasion and metastasis. The effect of these integrins might be especially important in cancer cells that have activating mutations, or amplifications, of the genes that encode these RTKs.

Tenascin-C regulates angiogenesis in tumor through the regulation of vascular endothelial growth factor expression

In order to verify whether tenascin-C (TN-C) is involved in angiogenesis as an extracellular signal molecule during tumorigenesis, cancerous cell transplantation experiments and coculture experiments were carried out, focusing on the regulation of vascular endothelial growth factor (VEGF). The A375 human melanoma cells introduced the GFP gene (A375-GFP), implanted subcutaneously into BALB/cA nude (WT) and TN-C knockout BALB/cA nude (TNKO) congenic mice. Furthermore, coculture experiments between A375-GFP and embryonic mesenchyme, which was prepared from both genotypes, were carried out to investigate the molecular mechanism in the cell-cell interactions. Both the content of TN-C and that of VEGF in the tumor and the conditioned medium were analyzed by the sandwich ELISA method. Seven days after transplantation of the A375-GFP, capillary nets became far more abundant in the tumors grown in WT mice than those in TNKO mice. Interestingly, VEGF and TN-C expressions showed antithetical expression patterns between the tumors in WT mice and those in TNKO mice. This peculiar phenomenon seems to be caused by a time lag prior to the onset of the mesenchymal regulation for the TN-C expression of A375-GFP. The coculture experiments revealed that WT mesenchyme had a much stronger effect than TNKO mesenchyme on both TN-C and VEGF expression. However, the defects of TNKO mesenchyme were restored in all cases by additional TN-C. These results clearly indicated that the expressions of both TN-C and VEGF depend on the surrounding mesenchyme, and that the function of mesenchyme is regulated by its own mesenchymal TN-C. In conclusion, the present data suggest that the matrix microenvironment organized by the host mesenchyme is very important for angiogenesis in tumor development.

Mouse embryonic mammogenesis as a model for the molecular regulation of pattern formation

In this review we describe how mouse embryonic mammogenesis depends on a continuous communication between the epithelial and mesenchymal compartment of the mammary rudiment. Although the functions of only a few genes in the regulation of these epithelio-mesenchymal interactions during mouse mammary development are known so far, key roles are suggested for WNT, FGF and PTHrP signaling. However, the exact mechanism of action of these signaling pathways and their possible cross-talk in the induction of mammary development are not clear, nor does our current knowledge suffice to explain how the number and positions of the mammary rudiments are so well defined. Nonetheless, by the description of aberrant induction and/or maintenance of the mammary rudiments in a variety of inbred mouse strains and mutants, we have accumulated data demonstrating that the mammary rudiments develop independently of each other at these positions. In addition, each rudiment pair responds differently to altered levels of gene expression. This not only clarifies the unique identity of each placode, but the different molecular requirement of each placode also suggests that different molecular mechanisms may underlie the formation of such identical structures. For future investigations in the field, such a unique molecular identity of each mammary rudiment should be of critical concern.

Implantation-associated changes in bovine uterine expression of integrins and extracellular matrix

Appropriate integrin expression appears to be necessary for successful implantation of human embryos and varies considerably among species. The present study was undertaken to determine the distributions of integrin subunits alpha(1), alpha(3), and alpha(6) as well as the extracellular matrix (ECM) components collagen IV and laminin in implanting bovine trophoblast and endometrium. Immunohistochemical staining of cryostat sections prepared from nonpregnant endometrium, of preattachment through to early villus development pregnant endometrium (Days 18, 21, 24, and 30), and of isolated trophoblast binucleate cells was performed. Trophoblast down-regulated the integrin alpha(1) subunit as attachment proceeded, whereas reactivity scores for alpha(6) antibody tended to increase from Day 18 through 24 and remained high. A subpopulation of trophoblast binucleate cells expressed the alpha(3) integrin subunit. Uterine epithelium constitutively expressed alpha(3) and alpha(6) integrin subunits, but the alpha(1) subunit was down-regulated as the luminal epithelium was modified. Collagen IV and laminin reactivity increased in the basal lamina and underlying subepithelial stroma as pregnancy proceeded. The results suggest that binucleate cell fusion with the maternal epithelium initiates integrin and ECM changes in the subepithelial stroma.

Increased expression of tenascin in pheochromocytomas correlates with malignancy

Tenascin is a significant extracellular matrix glycoprotein, which is upregulated in various neoplasias and pathologic processes. Pheochromocytomas are rare tumors of the sympathoadrenal system, whose malignancy is almost impossible to predict. There are no histologic or chemical markers available that would define the malignant behavior of these tumors, except the discovery of metastases. In our search for new markers, we investigated the immunohistochemical expression of tenascin in a large number of pheochromocytomas and paragangliomas. Seven tumors were metastasized and were thus considered malignant. Normal adrenal medulla was tenascin negative. A striking difference was seen between malignant and benign pheochromocytomas. All malignant pheochromocytomas expressed stromal tenascin strongly or moderately, whereas most benign pheochromocytomas (28 of 37, 70%) showed no or only weak immunopositivity. The staining was strong or moderate also in 13 of 28 (46%) of the tumors that showed histologically suspicious features, here called borderline tumors. Paragangliomas showed a more heterogeneous staining pattern, and no significant difference was found between benign and malignant paragangliomas. To our knowledge, this is the first study to demonstrate the expression of tenascin in pheochromocytomas and particularly the enhanced expression in malignant pheochromocytomas. We therefore suggest that tenascin may be associated with the malignant transformation and metastasis of pheochromocytomas. It is also a potential marker predicting more aggressive behavior in pheochromocytomas.

Annexin II overexpression correlates with stromal tenascin-C overexpression: a prognostic marker in colorectal carcinoma

BACKGROUND

Overexpression of annexin II, a calcium-dependent phospholipid-binding protein, has been reported in various carcinomas. One of its ligands is tenascin-C, an extracellular matrix glycoprotein with predominantly antiadhesive qualities that also has been reported to be a prognostic marker for several carcinomas. In the current study, the authors investigated the correlation between the overexpression of annexin II and tenascin-C in colorectal carcinoma.

METHODS

Western blot analysis of annexin II expression was examined in four human colorectal carcinoma cell lines. Using immunohistochemical methods, the authors also examined expression of annexin II and tenascin-C in 105 primary colorectal carcinoma cases.

RESULTS

Although annexin II was expressed in human colon carcinoma cell lines, there was no apparent correlation between its expression level and the metastatic potential of these cell lines. The authors observed overexpression of annexin II and tenascin-C proteins in 29.5% and 49.5%, respectively, of colorectal carcinoma cases. Overexpression of annexin II was found to be correlated significantly with histologic type, tumor size, depth of invasion, and pTNM stage, whereas tenascin-C overexpression was noted to be correlated significantly with histologic type, depth of invasion, lymphatic invasion, venous invasion, lymph node metastasis, and pTNM stage. Expression of annexin II was shown to be correlated significantly with that of tenascin-C. Multivariate analysis demonstrated that annexin II and tenascin-C cooverexpression was an independent factor of poor prognosis in patients with colorectal carcinoma.

CONCLUSIONS

The data from the current study suggest that both annexin II and tenascin-C are overexpressed in advanced colorectal carcinoma and that they may be related to the progression and metastatic spread of colorectal carcinoma.

Differentiation therapy of human cancer: basic science and clinical applications

Current cancer therapies are highly toxic and often nonspecific. A potentially less toxic approach to treating this prevalent disease employs agents that modify cancer cell differentiation, termed 'differentiation therapy.' This approach is based on the tacit assumption that many neoplastic cell types exhibit reversible defects in differentiation, which upon appropriate treatment, results in tumor reprogramming and a concomitant loss in proliferative capacity and induction of terminal differentiation or apoptosis (programmed cell death). Laboratory studies that focus on elucidating mechanisms of action are demonstrating the effectiveness of 'differentiation therapy,' which is now beginning to show translational promise in the clinical setting.

Tenascin-C in development and disease: gene regulation and cell function

Tenascin-C (TN-C) is a modular and multifunctional extracellular matrix (ECM) glycoprotein that is exquisitely regulated during embryonic development and in adult tissue remodeling. TN-C gene transcription is controlled by intracellular signals that are generated by multiple soluble factors, integrins and mechanical forces. These external cues are interpreted by particular DNA control elements that interact with different classes of transcription factors to activate or repress TN-C expression in a cell type- and differentiation-dependent fashion. Among the transcriptional regulators of the TN-C gene that have been identified, the homeobox family of proteins has emerged as a major player. Downstream from TN-C, intracellular signals that are relayed via specific cell surface receptors often impart contrary cellular functions, even within the same cell type. A key to understanding this behavior may lie in the dual ability of TN-C-enriched extracellular matrices to generate intracellular signals, and to define unique cellular morphologies that modulate these signal transduction pathways. Thus, despite the contention that TN-C null mice appear to develop and act normally, TN-C biology continues to provide a wealth of information regarding the complex nature of the ECM in development and disease.

Tenascin-A marker for the malignant potential of preinvasive breast cancers

OBJECTIVE

Up to now, the mechanisms responsible for progression from noninvasive to invasive breast cancer have remained obscure. Tenascin is an extracellular matrix glycoprotein, present in embryonal and fetal tissues, which is also found in the stroma of various benign and malignant pathologies. We studied the expression and immunohistochemical behavior of tenascin in specimens of invasive and preinvasive breast cancer in order to assess its potential role as a marker for tumor invasion.

MATERIALS AND METHODS

Sixty-eight specimens including 29 noninvasive ductal cancers, 12 invasive ductal cancers, 5 adenoses, 7 fibroadenomas, and 15 samples of normal human breast tissue were evaluated. An immunofluorescent microscopic technique was used for analysis of the localization and distribution of tenascin. Paraffin-embedded biopsies were incubated with primary monoclonal anti-tenascin antibodies (1:25, Dako-tenascin, TN2). Subsequently, trimethylrhodamine-isothiocyanate-conjugated secondary antibodies (rabbit anti-mouse immunglobulins (Dakopatts, Denmark) were added to visualize the protein.

RESULTS

A significant tenascin expression was observed around the ducts in all samples of patients with preinvasive breast cancers. Intensive staining was also found in the periductal stroma of all specimens of patients with invasive breast cancers. Benign breast lesions showed weaker reactivity. No tenascin expression was detectable in normal human breasts, while tissue samples of in situ cancers presented variable staining intensities positively correlating with the degree of differentiation.

CONCLUSION

Tenascin immunofluorescence may prove a suitable and helpful adjunct for diagnosing malignant disease and for predicting the invasive potential of premalignant breast lesions.

The tenascin family of ECM glycoproteins: structure, function, and regulation during embryonic development and tissue remodeling

The determination of animal form depends on the coordination of events that lead to the morphological patterning of cells. This epigenetic view of development suggests that embryonic structures arise as a consequence of environmental influences acting on the properties of cells, rather than an unfolding of a completely genetically specified and preexisting invisible pattern. Specialized cells of developing multicellular organisms are surrounded by a complex extracellular matrix (ECM), comprised largely of different collagens, proteoglycans, and glycoproteins. This ECM is a substrate for tissue morphogenesis, lends support and flexibility to mature tissues, and acts as an epigenetic informational entity in the sense that it transduces and integrates intracellular signals via distinct cell surface receptors. Consequently, ECM-receptor interactions have a profound influence on major cellular programs including growth, differentiation, migration, and survival. In contrast to many other ECM proteins, the tenascin (TN) family of glycoproteins (TN-C, TN-R, TN-W, TN-X, and TN-Y) display highly restricted and dynamic patterns of expression in the embryo, particularly during neural development, skeletogenesis, and vasculogenesis. These molecules are reexpressed in the adult during normal processes such as wound healing, nerve regeneration, and tissue involution, and in pathological states including vascular disease, tumorigenesis, and metastasis. In concert with a multitude of associated ECM proteins and cell surface receptors that include members of the integrin family, TN proteins impart contrary cellular functions, depending on their mode of presentation (i.e., soluble or substrate-bound) and the cell types and differentiation states of the target tissues. Expression of tenascins is regulated by a variety of growth factors, cytokines, vasoactive peptides, ECM proteins, and biomechanical factors. The signals generated by these factors converge on particular combinations of cis-regulatory elements within the recently identified TN gene promoters via specific transcriptional activators or repressors. Additional complexity in regulating TN gene expression is achieved through alternative splicing, resulting in variants of TN polypeptides that exhibit different combinations of functional protein domains. In this review, we discuss some of the recent advances in TN biology that provide insights into the complex way in which the ECM is regulated and how it functions to regulate tissue morphogenesis and gene expression.

Parathyroid hormone-related protein signaling is necessary for sexual dimorphism during embryonic mammary development

Male mice lack mammary glands due to the interaction of circulating androgens with local epithelial-mesenchymal signaling in the developing mammary bud. Mammary epithelial cells induce androgen receptor (AR) within the mammary mesenchyme and, in response to androgens, the mesenchyme condenses around the epithelial bud, destroying it. We show that this process involves apoptosis and that, in the absence of parathyroid hormone-related protein (PTHrP) or its receptor, the PTH/PTHrP receptor (PPR1), it fails due to a lack of mesenchymal AR expression. In addition, the expression of tenascin C, another marker of the mammary mesenchyme, is also dependent on PTHrP. PTHrP expression is initiated on E11 and, within the ventral epidermis, is restricted to the forming mammary epithelial bud. In contrast, PPR1 expression is not limited to the mammary bud, but is found generally within the subepidermal mesenchyme. Finally, transgenic overexpression of PTHrP within the basal epidermis induces AR and tenasin C expression within the ventral dermis, suggesting that ectopic expression of PTHrP can induce the ventral mesenchyme to express mammary mesenchyme markers. We propose that PTHrP expression specifically within the developing epithelial bud acts as a dominant signal participating in cell fate decisions leading to a specialized mammary mesenchyme.

Tenascin-C modulates tumor stroma and monocyte/macrophage recruitment but not tumor growth or metastasis in a mouse strain with spontaneous mammary cancer

The local growth of tumors and their ability to metastasize are crucially dependent on their interactions with the surrounding extracellular matrix. Tenascin-C (TNC) is an extracellular matrix protein which is highly expressed during development, tissue repair and cancer. Despite the high levels of TNC in the stroma of primary and metastatic tumors, the function of TNC is not known. In the present study we have crossed TNC-null mice with a mouse strain where both female and male mice spontaneously develop mammary tumors followed by metastatic disease in the lungs. We report that the absence of TNC had no effect on the temporal occurrence of mammary tumors and their metastatic dissemination in lungs. Furthermore, the number and size of tumors, the number and size of metastatic foci in the lungs, the proliferation rate and apoptosis of tumor cells and tumor angiogenesis were not altered in the absence of TNC. Histological examination revealed that the tumor organisation, however, was modulated by TNC. In the presence of TNC both primary as well as metastatic tumors were organised in large tumor cell nests surrounded by thick layers of extracellular matrix proteins. In the absence of TNC these tumor cell nests were smaller but still separated from each other by extracellular matrix proteins. In addition, the TNC-null stromal compartment contained significantly more monocytes/macrophages than tumor stroma from TNC wild-type mice. Using in vitro coculture experiments we show that TNC-null tumor cells were still able to activate the TNC gene in fibroblasts which express low basal levels of TNC. Altogether these data indicate that TNC has a very limited role during the spontaneous development and growth of mamary tumors and their metastasis to the lungs.

Expression of tenascin in human cervical cancer--association of tenascin expression with clinicopathological parameters

OBJECTIVE

Tenascin is an extracellular matrix glycoprotein, relevant for embryonal and fetal development, which is reexpressed in the stroma of benign and malignant tumors. Little is known about the molecular interaction of tenascin during neoplastic transformation and tumor progression in cervical cancer.

METHOD

We studied the expression of tenascin in normal tissue of the cervix uteri, cervical carcinoma in situ, and invasive cervical carcinoma in paraffin sections by immunohistochemistry using a monoclonal antibody. Tenascin immunoreactivity was compared with various prognostic parameters.

RESULTS

In normal cervical tissue (n = 5) and in cervical carcinoma in situ (n = 10) only vessel walls showed a weak tenascin cross-reactivity, whereas tenascin was not expressed in the epithelial layer or the underlying connective tissue. In invasive cervical carcinoma (n = 89) tenascin expression was markedly increased. In 84% (n = 75) of the cases examined a strong tenascin immunoreactivity was noted around and within the tumor cell nests. Sixteen percent (n = 14) of infiltrating cervical carcinomas showed no tenascin immunoreactivity. A definite correlation was found between weak or no tenascin expression and slight desmoplastic mesenchymal reactivity (n = 42/91%, P < 0.001), lymphatic space invasion (n = 54/81%, P < 0.001), and lymph node metastases (n = 30/77%, P < 0.05). Tenascin-positive patients had a significantly better prognosis than tenascin-negative patients (mean survival time of 56.5 +/- 4.1 months versus 31.9 +/- 5.6 months, P < 0.05).

CONCLUSION

Based on these findings we discuss that the appearance of tenascin is an indicator of an adequate biological defense in cervical cancer patients. The tenascin staining may therefore be useful for detecting a subgroup of invasive cancer patients missing tenascin reactivity with alterations of stromal defense and a poorer prognosis.

Tenascin-C in the cochlea of the developing mouse

Tenascin-C is a glycoprotein of the extracellular matrix that acts in vitro as both a permissive and a nonpermissive substrate for neurite growth. We analyzed, by immunocytochemistry, the distribution of tenascin-C along neural growth pathways in the developing mouse cochlea. In the spiral lamina, tenascin-C coexists in a region where nerve bundles arborize. In the organ of Corti, tenascin-C lines the neural pathways along pillar and Deiters' cells before and during the time of nerve fiber ingrowth. By embryonic day 16, tenascin-C is abundant on the pillar side of the inner hair cell but does not accumulate on the modiolar side until about birth, a time after the arrival of afferent fibers. The synaptic zones beneath outer hair cells are strongly labeled during the time when early events in afferent synaptogenesis are progressing but not during the time of efferent synaptogenesis. At the age when most neural growth ceases, tenascin-C immunoreactivity disappears. Faint tenascin-C immunolabeling of normal hair cells, strong tenascin immunolabeling in pathological hair cells of Bronx waltzer (bv/bv) mice, and staining for beta-galactosidase, whose gene replaces tenascin in a "knockout" mouse, indicate that hair cells supply at least part of the tenascin-C. The changing composition of the extracellular matrix in the synaptic region during afferent and efferent synaptogenesis is consistent with a role for tenascin in synaptogenesis. The presence of tenascin-C along the growth routes of nerve fibers, particularly toward the outer hair cells, raises the possibility that growth cone interactions with tenascin-C helps to guide nerve fibers in the cochlea.

Immunolocalization of tenascin in the chinchilla inner ear

Tenascin was immunolocalized in the chinchilla cochlea and vestibular system to better understand the functional morphology of the inner ear. Inner ear tissues were fixed with acetone, decalcified and cryosectioned. Indirect immunofluorescence, using antibodies directed against human tenascin epitopes, were used to detect tenascin. As a positive control, tenascin immunoreactivity was found in kidney, cortical mesangial cells and the extracellular matrix of glomeruli and medullary tubule interstitial spaces, concurring with previously reported results. In the cochlea, tenascin immunoreactivity was present in osteocytes, the mesothelial cells underlying the basilar membrane (BM) and within the fibrous matrix of the BM. Greater reactivity was observed in the mesothelial cells than in the fibrous matrix of the BM. In the vestibular system, tenascin immunoreactivity formed a diffuse band directly beneath the basal lamina of the ampullary and otoconial organs. Tenascin immunoreactivity was also observed in cup-shaped regions between the type I vestibular hair cells and their surrounding VIII nerve calyces in the ampullary and otoconial organs. This is the first report of the anatomical distribution of tenascin in the adult, mammalian inner ear, other than our previously published abstract P.A. Santi and D. Swartz, Soc. Neurosci. Abstr. 23 (1997) 731.

Tenascin is differentially expressed in endometrium and endometriosis

Endometriosis is characterized by the presence of functional endometrial tissue outside the uterine cavity, most commonly on the ovary and peritoneum. The aetiology of endometriosis is not understood, although the adhesion of endometrial cells to the extracellular matrix (ECM) would be expected to play a central role in its pathogenesis. The expression of ECM molecules in endometrium and in endometriosis has been investigated using immunohistochemistry and western blotting techniques. The ECM components collagen IV, laminin, vitronectin, and fibronectin had a similar pattern of expression throughout the menstrual cycle in endometrium and endometriosis. Expression of tenascin was elevated in the stroma of the functionalis region of the endometrium during the proliferative stage of the menstrual cycle and in endometriosis. Tenascin expression in endometriosis was not modulated according to the stage of the menstrual cycle. It is concluded that expression of tenascin is strictly regulated in endometrium and may be important in endometrial regeneration and in the pathogenesis of endometriosis.

TGF-beta1 influences early gingival wound healing in rats: an immunohistochemical evaluation of stromal remodelling by extracellular matrix molecules and PCNA

The effect of topically applied transforming growth factor beta1 (TGF-beta1) on the rat gingival wound healing process after flap surgery was evaluated by immunohistochemistry for extracellular matrix molecules (ECM), such as tenascin, heparan sulfate proteoglycan (HSPG) and type IV collagen, and for proliferating cell nuclear antigen (PCNA) in fibroblasts. TGF-beta1 solution was applied to the surgical wound experimental sites. Two microg/microl were applied at the time of the operation, and 1 microg/microl at days 1 and 2 after surgery, with contralateral control sites receiving the vehicle alone. Periodontal tissues were histologically examined at 3 and 7 days post-surgery. Tenascin was found to be more strongly stained in the granulation tissue from experimental sites at 3 days post-surgery. At 7 days postsurgery, HSPG-positive areas in granulation tissue had become smaller and there was a prominent proliferation of PCNA-positive fibroblast-like cells and type IV collagen-positive blood vessels. These results suggest that TGF-beta1 applied to surgical wounds influences early proliferation of gingival fibroblast-like cells, the formation of blood vessels, and ECM remodelling. In conclusion, TGF-beta1 application appears to promote granulation tissue formation in periodontal wound healing.

Breast development gives insights into breast disease

AIMS

Studies of developing human breasts are essential for understanding the organogenesis as well as molecular pathogenesis of benign and malignant breast diseases. In this study we have examined the distribution of TGF-alpha, TGF-beta 1, tenascin-C and collagen type IV with the aim of starting to build a picture of the profile of molecules that may be involved in the development of the human breast.

METHODS AND RESULTS

Ten fetal breasts (16 to 23 weeks of gestation) and 45 infant breasts, ranging in age from newborn to 2 years, were used in this study. Paraffin sections from these samples were immunostained with antibodies for these proteins and for Ki67 to elucidate the level of proliferative activity in different stages of breast development. TGF-alpha immunoreactivity was observed both in the stromal and the epithelial cells within fetal and infant breasts up to 25 days. TGF-beta 1 immunoreactivity was localized in the extracellular matrix. Tenascin-C was found around the neck of the developing breast bud and in the extracellular matrix of the infant with peaks in the newborn at 6-12 weeks. The immunoreactivity for type IV collagen was more intense in the region of the breast bud neck in the fetal breasts and reduced around the tips of lobular and terminal-end buds within the infant breasts.

CONCLUSIONS

The distribution of the growth factors and extracellular matrix proteins within the developing human breast indicates that they play a significant role in different cellular compartments during morphogenesis and provides insights into breast disease.

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.

The expression of tenascin-C with the AD1 variable repeat in embryonic tissues, cell lines and tumors in various vertebrate species

Tenascin-C is a modular glycoprotein composed of domains of amino acid repeats. All forms of tenascin-C have eight constant fibronectin type III repeats, but additional fibronectin type III repeats can be spliced into a variable domain found between the fifth and sixth constant repeats. Four extra repeats, named A, B, C and D, have been examined previously. Here, we have used in situ hybridization to determine the tissue origins of the novel AD1 and AD2 repeats. In the embryonic-day-10 chicken embryo, transcripts encoding the AD2 repeat are limited to the tips of lung bronchioles and the base of feather buds. In contrast the AD1 hybridization signal was widespread. Quantitative in situ hybridization reveals AD1-containing transcripts represent up to 85% of the total tenascin-C mRNA in some tissues (developing bone), and are undetectable in others (e.g. radial glia). Avian and human tumor cell lines were examined for the expression of the AD1 repeat using the reverse transcriptase polymerase chain reaction (RT-PCR). Transcripts encoding six different tenascin-C splice variants incorporating the AD1 repeat were found in the fibrosarcoma cell line, QT6. Many human tumor cells, including malignant melanoma and ductal breast carcinoma, were positive for AD1 tenascin-C expression. In addition, we found evidence of AD1 tenascin-C expression in samples of excised human tumors. Our results show that a novel variant may be a major part of the tenascin-C of the embryonic extracellular matrix, and may also be found in the stroma surrounding some human tumors.

Tenascin expression in elastotic cuffs of invasive ductal carcinoma of the breast

We studied immunohistochemically one thousand one hundred and thirty-seven cases of primary invasive breast cancers (NST) and adjacent normal mammary glands for tenascin expression, and compared their elastic content to verify if a relationship exists between tenascin expression and elastosis. Periductal, perivascular and stromal elastosis were graded on a scale from 0 to 3 (absent to massive). All carcinomas showed tenascin expression and elastosis with various histological appearances. In the adjacent breast, teanscon was distributed around the normal ducts or with extasia and uctal hyperplasia without atypia. Digestion of the sections with elastase prior to staining resulted in a loss of the specific staining reactions in all areas where elastosis was present. Tenascin staining was observed in the mesenchyme closely surrounding the neoplastic ducts and the cancer cell nests. Stromal tenascin staining appeared stronger in those carcinomas that exhibited marked desmoplastic reactions. The highly differentiated tumours contained more elastosis in their tumour tissue than the poorly differentiated ones, whereas tenascin expression was stronger in poorly differentiated tumours than well differentiated tumours. A strong staining for tenascin was observed in the elastotic cuff. Tenascin staining did not disappear afterwards with elastase. We did not find a statistically significant correlation between tenascin expression, elastosis and prognostic factors such as size of the tumour, lymph node metastasis, tumour necrosis and age. In our study tenascin proved to be an additional element in elastotic areas even though the significance of an association between elastosis and tenascin is still unknown, as is that of elastosis itself.

Effect of snuff and smoking on tenascin expression in oral mucosa

We have shown, by using two monoclonal antibodies (143DB7 and 100EB2), that the expression of the extracellular matrix protein tenascin (Tn) is increased in the connective tissue of biopsies taken from snuff users' and tobacco smokers' oral mucosa. In normal oral mucosa Tn was seen to underlie the epithelium as a thin delicate band. The most increase in Tn reaction was observed in snuff users' mucosa while the immunoreaction in smokers' mucosa was less conspicuous. Often the most prominent Tn reaction took place in association with round cell inflammatory infiltration, indicating epithelial irritation. Tn has been shown to take part in epithelial-mesenchymal interactions during embryogenesis, wound healing and tumorigenesis. Here, a superficial epithelial irritant has been shown to cause conspicuous alterations not only in the epithelial cell layers but also in the underlying connective tissue by increasing its Tn content. As a result of our findings we suggest a further link for Tn in a dynamic epithelial-mesenchymal interplay by virtue of this marked connective tissue reaction in snuff users' and smokers' oral mucosa.

Extracellular matrices expression in invasion area of adenoid cystic carcinoma of salivary glands

Adenoid cystic carcinoma (ACC) is a salivary malignant tumor with poor long-term prognosis, that is known to have predilection for invasion of the adjacent stroma and neural tissues. This carcinoma has shown a high incidence of recurrence and distal metastasis. Invasive carcinomas have been associated with the distributions of extracellular matrices (ECM). Cell proliferation as a marker of tumor growth has been related to poor prognosis in oral carcinomas. Immunohistochemical analysis of 15 cases of ACC was done using antibodies to laminin, type IV collagen, fibronectin, tenascin and anti-proliferating nuclear antigen (PCNA). Laminin and type IV collagen were totally or partially absent in the ACC invasive areas. Tenascin was expressed in the stroma and cytoplasm and was associated with tumor cell proliferation. It can be concluded that basement membrane represents a barrier that is lost during cell invasion and tenascin may be involved in the detachment of cancer cells, increasing the invasive potential of ACC.

Human epidermal keratinocytes are a source of tenascin-C during wound healing

Tenascin-C is a large hexameric extracellular matrix glycoprotein that is expressed in a temporally and spatially restricted pattern associated with stromal-epithelial interactions. In adult human skin, the expression level of tenascin-C is low, but tenascin-C is abundantly present in the dermal compartment during embryogenesis and wound healing and in skin tumors. Herein we have investigated the cellular source of tenascin-C production in human skin, both in vivo and in vitro, by using immunohistochemistry, mRNA in situ hybridization, western blotting, and an enzyme-linked immunosorbent assay. In addition we studied the cell-matrix interaction between epidermal keratinocytes and purified tenascin-C. By using in vitro culture models, we found that keratinocytes not only synthesize and secrete tenascin-C but can also deposit tenascin-C in de-epidermized dermis in a pattern that is very similar to that in vivo. In vivo, during wound healing of normal human skin, we found tenascin-C extracellularly in the wound bed and also in a granular pattern within the neo-epidermis. By mRNA in situ hybridization, we could identify the basal migrated keratinocytes as the main source of tenascin-C in the early phase of wound healing. In the granulation phase, tenascin-C expression by the keratinocytes is downregulated. Cultured keratinocytes were found to adhere poorly to tenascin-C, and those that did adhere retained a rounded morphology. We conclude that human keratinocytes are a major source of tenascin-C during the early phase of wound healing, and we hypothesize that tenascin-C is unlikely to be an adhesive substrate for migrating keratinocytes.

The change in tenascin expression in mouse uterus during early pregnancy

PURPOSE

Our aim was to examine the changes in spatiotemporal tenascin (TN) expression in mouse uterus during early pregnancy, when the uterine tissue undergoes a tremendous restructuring.

METHODS

Using immunohistochemistry and in situ hybridization, the changes in distribution of TN protein in mouse uterine tissues in pregnancy Day 0 through Day 5 were analyzed.

RESULTS

Immunoreactive TN and TN mRNA were expressed in the basement membrane of the epithelium as well as in the smooth muscle layer, and their distribution shifted from the subbasement region on Day 0-3 to the smooth muscle layer on Days 4 and 5.

CONCLUSIONS

These results indicate that TN expression in the uterus during early pregnancy is spatiotemporally different and may be regulated by a different mechanism.

Tenascin expression in cutaneous fibrohistiocytic tumors. Immunohistochemical investigation of 24 cases

We studied the immunolocalization of the extracellular matrix glycoprotein tenascin in a series of 24 cutaneous fibrohistiocytic tumors, including seven benign lesions (benign fibrous histiocytoma/dermatofibroma), six intermediate malignancy lesions (dermatofibrosarcoma protuberans), and 11 malignant lesions (three atypical fibroxantomas and eight malignant fibrous histiocytomas). The results of the immunohistochemical staining were evaluated semiquantitatively. All lesions expressed tenascin in the extracellular matrix, with some differences in the distribution of the immunoreactivity. In benign fibrous histiocytoma and in dermatofibrosarcoma protuberans, there was a homogeneous, intense, and diffuse staining of the extracellular matrix (++); the only exception was the homogenized, sclerotic collagen present in late, regressing benign fibrous histiocytoma, which showed a weak and patchy reactivity (+). In atypical fibroxantomas and in malignant fibrous histiocytomas, there was an irregular distribution of the positivity within the tumor matrix (+). Prominent staining of the cytoplasm of several neoplastic cells was observed in atypical fibroxantoma and malignant fibrous histiocytoma (++), focal cytoplasmic staining of scattered cells was found in dermatofibrosarcoma protuberans (+), and cytoplasmic staining was absent from benign fibrous histiocytoma (-). These findings indicate a relationship between cytoplasmic and extracellular matrix expression of tenascin in these lesions, with an increase in cytoplasmic staining and a decrease in extracellular matrix staining in the malignant forms. Based on these different staining patterns, tenascin immunolocalization could furnish some help in the differential diagnosis among benign, intermediate malignancy, and malignant cutaneous fibrohistiocytic tumors. Moreover, the intense tenascin staining at the edge of the lesion could be helpful in defining its extent and therefore provide an additional criterion to evaluate the radicality of the surgical procedure.