Expressions Of E-cad/cat Complex In So-called Pulmonary Sclerosing Hemangioma

IntroductionSo-called pulmonary sclerosing hemangioma ( PSH) was first reported by Liebow et al as an uncommon pulmonary lesion. So far its histological origin and nature are still uncertain. Although a majority of patients present a "benign" process clinically, there are a few reports declaring PSH with regional invasion or lymph node metastases. Up to date, most study results suggest that PSH is an epithelial neoplasm derived from primitive respiratory epithelium, indicate that the two different morphous cells of PSH, cuboidal cells and polygonal cells, are derived from the same cell, and this manifest may be interpreted as difference of directions and degrees of differentiation. Our previous study showed that cuboidal cells of papillary surface and the inner coving hemangioma pattern were very similar to the well differential type II pneumocytes, while stroma polygonal cells possess the capability for multipotential differentiation.E-cadherin is a calcium-dependent cell adhesion molecule, and mainly mediates cell-cell adhesion in epithelial cells. The cad-cat complex, formed by the combination of the carboxy cytoplasmic domain of E-cadherin with catenins, is essential to maintain the stability of cell-cell adhesion, and is also one of the characters of the well differential normal epithelial cell. P120~ctn , one member of catenin family, has the ability to control cadherin turnover, thereby regulating cadherin levels. It takes part in cell adhesion, mobility and is important in cell invasion and immigration. To explore differentiated status of the two different morphous cells, the present study applied immunohistochemistry to investigate the expressions of E-cad/cat complex in PSH, and hyperplastic type II pneumocytes of pulmonary inflammatory pseudotumor are used as control.Materials and methods1.1 Materials and methods25 PSH cases and 8 pulmonary inflammatory pseudotumor cases were obtained from the Pathology Diagnostic Center of the First Affiliated Hospital of China Medical University from 1995 to 2002. Specimens were fixed with neutral formalin. The paraffin sections were sliced into 4jxm thick samples, deparaf-finized in xylene, rehydiated in graded alcohol, and transferred to PBS. In combination with light microscopy on hematoxylinOeosin samples, immunohistochem-istry (S-P method) was performed with anti-E-cadherin (MAB-0247, Maixin) , anti-p-catenin (MAB-0259, Maixin) and anti-pi20ctn ( dilution l:200, Trans-duction). SP and DAB kit were the product of Fuzhou Maixin Biological Technique Company. All the specimens underwent antigen recovery with heat-induced epitope retrieval. The immunoreaction was visualized by demonstration of conjugated peroxidase with DAB as the substrate. The slides were counterstained with hematoxylin after DAB staining. For the negative control, phosphate buffered saline was used for the primary antibodies.1. 2 Result evalutionFive views were examined per slide, and 100 cells were observed per view, at 400 magnification. Semiquantitative evaluations of immunohistochemistry results were performed according to the percentages of positive cells;no positive cells (-) , positive cells ^25% ( + ) , 26 -50% ( ++ ) , 51 -75% ( ++ + ) , =576% (RESULTSGross and Histological FeaturesThe tumors were well circumscribed without capsule. They were medium soft and often had a pale-brown region caused by hemorrhage. Under light microscopy , the tumors displayed four histological patterns;solid, papillary, hem-orrhagic and sclerotic. The Four histological patterns transit among each other.There are two major tumor cells: polygonal cells and cuboidal cells. Polygonal cells lie in solid and papillary patterns. Cuboidal cells are on the surfaces of papillary and luman spaces. A few cuboidal cells in solid patterns appear cluster or glandular pattern. A number of basophilia mast cells appear in most patterns of PSH. In the stroma, there are lymphocytes, hemosiderin sediment calcification, and ossification.Immunohistochemical resultsImmunohistochemistry results showed that the expressions of E-cadherin, P-catenin and pl20ctn were distinct, continuous and strongly positive ( ++++ ) at membrane in the surface cuboidal cells of 25 PSH. Their expressions rates were 100%. The inner covering cells in the hemangioma pattern were positive in cytoplasm and on membrane positive for E-cadherin, (3-catenin and pl20ctn. The positive rates and expression densities of the three adhesive molecules were reduced significantly in the polygonal cells, and the positive signals were mainly in cytoplasm. They were negative or weakly positive for E-cadherin, cytoplasm positive for (3-catenin and a predominant cytoplasm positive with a little membranous positive for pl20ctn. In polygonal cells, all three adhesive molecules showed heterogeneity stain. The expressions of three adhesion molecules in hy-perplastic type II pneumocytes of pulmonary inflammatory pseudotumor were the same to the cuboidal cells of PSH.DISCUSSIONSince the first report and naming " sclerosing hemangioma of the lung" in 1956 by Liebow et al, a number of studies have provided us a comprehensive understanding towards the nature and histogenesis of PSH gradually. For example , Devouassous-Shisheborran et al found that both cuboidal and polygonal cells in the nucleus were strongly positive for TTF-1. TTF-1 (thyroid transcription fac-tor-1) was specifically expressed not only in adult type II pneumocytes and Clar-a cells but also in fetal lung epithetlial cell nuclei. These results suggested that PSH may originate from primitive respiratory epithelium. In our previous study, although cuboidal cells were positive for TTF-1, they also expressed SP-B andCK. At the same time, we found particular lamellar body presenting in cuboidal cells. It is plausible to speculate that they were very similar to the well differential type II pneumocytes, while stroma polygonal cells were positive not only for TTF-1 but also for Vimentin, as well as sporadically and weakly positive for CK, EM A and neuroendocrine markers ( eg. NSE). However, they were negtive for SP-B. These evidences suggested that polygonal cells possessed the capability for multipotential differentiation, while cuboidal cells didn't. Further studies compared the expression of E-cadherin/catenin complex, a commonly and stably expressed marker in normal epithelial cells, in cuboidal cells and polygonal cells of PSH contrast to its expression of hyperplastic type II pneumocytes of pulmonary inflammatory pseudotumor. The results showed that the surface cuboidal cells differentiate to type II pneumocytes of PSH were strongly positive on membrane for E-cadherin, p-catenin and pl20ctn, with cytoplasm positive expression of (3-catenin. The expressions of three adhesion molecules in hyperplastic type II pneumocytes of pulmonary inflammatory pseudotumor were very similar to the cuboidal cells of PSH, suggesting that the cuboidal cells differentiate to type II pneumocytes in the tumorigenesis. The expressions of E-cadherin, p-catenin and pl20ctn in polygonal cells are quite different from that in cuboidal cells: the positive rates and expression densities of the three adhesive molecules were reduced significantly in the polygonal cells, and the positive signals were mainly in cytoplasm. It is suggested that polygonal cells were different from cuboidal cells, they were in different differentiation situation. WhatS more, positive cell proportions of all the three adhesion molecules were different from case by case and from site to site in one case. In a word, all the three adhesion molecules showed heterogeneity stain in polygonal cells. These results were similar to that of Nagata et al (three epithelial markers as EMA, SC and surfactant apoprotein showed heterogeneity stain in polygonal cells of PSH) , suggesting that the polygonal cells originating from primitive respiratory epithelium were probably in different directions and/or degree of differentiation.It is well known that the decrease of cell-cell adhesion is the initial component in tumor matastisis. E-cadherin mediates intercellular adhesion on epithelial membrane. It plays a key role in the maintenance of cell morphous and tissueintegrity. The carboxy cytoplasmic domain of this molecule is associated with (3-catenin or 7- catenin to form the E-cadherin/catenin complex, and the latter is then bind to actin cytoskeleton through a-catenin. Moreover, p 120ctnassociates with E-cadherin via pl20ctnArm domain and the juxtamembrane domain (JMD) of E-cadherin. Thus the E-cadherin/catenin complex is formed. Any changes in E-cadherin or catenins of cad/cat complex can affect the adhesion function, leading to the decrease of cell-cell adhesion, loss of cell polarity, alinement loose, and more possibility to detachment, invasion and metastasis. Although a majority of PSH patients appeared a "benign" process clinically, it has reported that more than 10 cases of PSH with hilar, peribranchial and interlobar lymph node metastases up to date. It could be observed that a number of sheet polygonal cells and only a few or no cubiodal cells in the lymph node metastatic deposit. In our study all the cases have no lymph node metastasis, so the phenomenon above could not be observed. Whereas polygonal cells lack the ability of forming the E-cadherin/catenin complex, which support the standpoint that polygonal cells is not as mature as cubiodal cells.In the present study, we found the inner covering cells in the hemorrhagic pattern of PSH were positive in cytoplasm and on membrane for E-cadherin, |B-catenin and pl20cn, whereas the vascular endothelial cells in the tissue were negative for all these three adhesion molecules. However, the different expressions of E-cadherin, (3-catenin and pl20ctn between the inner covering cells in the hemorrhagic pattern and the cuboidal cells of PSH still need investigation.ConclusionTwo major cells of PSH may be in different differentiated stages. As for cuboidal cells have the character of the well differentiated epithelium similar as the hyperplastic type II pneumocytes, whereas polygonal cells in the stroma lack the capability of forming the E - cad/cat complex. *...