Molecular cloning of a cell-surface glycoprotein that can potentially discriminate mesothelium from epithelium: its identification as vascular cell adhesion molecule 1

Ovarian Cancer-Associated Mesothelial Cells: Transdifferentiation to Minions of Cancer and Orchestrate Developing Peritoneal Dissemination

Ovarian cancer has one of the poorest prognoses among carcinomas. Advanced ovarian cancer often develops ascites and peritoneal dissemination, which is one of the poor prognostic factors. From the perspective of the "seed and soil" hypothesis, the intra-abdominal environment is like the soil for the growth of ovarian cancer (OvCa) and mesothelial cells (MCs) line the top layer of this soil. In recent years, various functions of MCs have been reported, including supporting cancer in the OvCa microenvironment. We refer to OvCa-associated MCs (OCAMs) as MCs that are stimulated by OvCa and contribute to its progression. OCAMs promote OvCa cell adhesion to the peritoneum, invasion, and metastasis. Elucidation of these functions may lead to the identification of novel therapeutic targets that can delay OvCa progression, which is difficult to cure.

Immunohistochemical distribution of tubulin beta II in human normal and neoplastic tissues

Tubulin is the major constituent protein of microtubules. In mammals, there are seven beta-tubulins and six alpha-tubulins. Each beta-tubulin isotype has a unique tissue distribution. The purpose of this study was to describe the distribution of tubulin beta II in normal and neoplastic human tissues with immunohistochemical techniques. We obtained normal tissues from 33 cases (8 fetuses, 17 neonates, 3 children and 5 adults) and 121 samples of neoplastic tissue from surgical specimens or at autopsy. Immunohistochemical staining for tubulin beta II was performed using a monoclonal antibody, KNY379 developed in our laboratory. Tubulin beta II was detected in various normal tissues, particularly in fetal and neonatal tissues, such as the nervous system, pulmonary alveoli, bronchioles and bronchi, colon, pancreatic ducts and acini, renal convoluted tubuli, skin epidermis, body cavity mesothelial cells, smooth muscle and thymus. In the adult, broad expression was also observed; however, the immunoreactivity was weaker and the extent of its distribution decreased with age. In neoplastic tissues, tubulin beta II immunoreactivity was detected in various nervous system neoplasms and other neoplasms such as pancreatic solid cystic carcinoma, pleomorphic adenoma, Warthin's tumor, nephroblastoma, basal cell carcinoma and malignant mesothelioma. We conclude that our monoclonal antibody, KNY379, may be useful as a marker of nervous system neoplasm, pancreatic solid cystic carcinoma, pleomorphic adenoma, Warthin's tumor, nephroblastoma, basal cell carcinoma and malignant mesothelioma.

Immunohistochemistry in the distinction between malignant mesothelioma and pulmonary adenocarcinoma: a critical evaluation of new antibodies

AIM

The value of immunohistochemical staining in differentiating between malignant mesothelioma and pulmonary adenocarcinoma was re-examined using newly available commercial antibodies, with the aim of increasing the sensitivity and specificity of diagnosis, and simplifying the antibody panel required.

METHODS

Forty one malignant mesotheliomas and 35 lung adenocarcinomas were studied. Commercial antibodies to calretinin, E-cadherin, N-cadherin, surfactant apoprotein A (SP-A), thyroid transcription factor 1 (TTF-1), thrombomodulin, and cytokeratin 5/6 were applied using the streptavidin-biotin-peroxidase complex procedure on formalin fixed, paraffin wax embedded tissue.

RESULTS

E-cadherin was expressed in all adenocarcinomas and in 22% of the mesotheliomas. TTF-1 expression was detected in 69% of the adenocarcinomas and none of the mesotheliomas. Positive staining with polyclonal anticalretinin was detected in 80% of the mesotheliomas and 6% of the adenocarcinomas. N-cadherin was expressed in 78% of mesotheliomas and 26% of adenocarcinomas. Thrombomodulin was expressed in 6% of the adenocarcinomas and in 53% of the mesotheliomas. Cytokeratin 5/6 expression was detected in 6% of the adenocarcinomas and 63% of the mesotheliomas. The results were compared with the standard laboratory panel for mesothelioma diagnosis: anticarcinoembryonic antigen (anti-CEA), LeuM1, BerEP4, and HBME-1.

CONCLUSION

Of the antibodies used in this study, E-cadherin was 100% sensitive for pulmonary adenocarcinoma and TTF-1 was 100% specific for pulmonary adenocarcinoma. The application of these two antibodies alone was adequate for the diagnosis of 69% of adenocarcinomas and 78% of mesotheliomas. Where TTF-1 is negative and E-cadherin is positive, a secondary panel of antibodies, including BerEP4 and LeuM1 (CD15) and antibodies directed against CEA, calretinin, cytokeratin 5/6, thrombomodulin, and N-cadherin, is required for differentiation between malignant mesothelioma and pulmonary adenocarcinoma.

Adenosine suppresses alpha(4)beta(7) integrin-mediated adhesion of T lymphocytes to colon adenocarcinoma cells

The interaction of T lymphocytes with tumor cells, a key step in the antitumor immune response, is suppressed by adenosine, a nucleoside produced at increased levels within the hypoxic tumor environment. We have explored the mechanism by which adenosine interferes with the lymphocyte:tumor cell interaction. The adhesion of anti-CD3-stimulated T cells to syngeneic MCA-38 mouse colon adenocarcinoma cells did not involve LFA-1 (alpha(L)beta(2)) or VLA-5 (alpha(5)beta(1)). However, antibodies against either lymphocyte alpha(4) or beta(7) (but not beta(1)) integrin subunits, or against VCAM-1 on the tumor cells, significantly suppressed adhesion, showing that the recognition of MCA-38 cells by T cells is strongly dependent upon the association of alpha(4)beta(7) on the effector cells with VCAM-1 on the tumor targets. This association is modulated by adenosine: The ability of adenosine to suppress T cell adhesion to MCA-38 cells was lost if alpha(4)beta(7) was functionally blocked with anti-alpha(4) antibodies (i) prior to or (ii) during the adhesion assay or if (iii) alpha(+)(4) cells were depleted from the T lymphocyte population. The binding of T cells to fibronectin through alpha(4)beta(1) was not suppressed by adenosine. We conclude that adenosine partially inhibits the interaction of T lymphocytes with tumor cells by blocking the function of integrin alpha(4)beta(7).

Asbestos exposure upregulates the adhesion of pleural leukocytes to pleural mesothelial cells via VCAM-1

This study was designed to assess the effects of in vitro and in vivo asbestos exposure on the adhesion of rat pleural leukocytes (RPLs) labeled with the fluorochrome calcein AM to rat pleural mesothelial cells (RPMCs). Exposure of RPMCs for 24 h to either crocidolite or chrysotile fibers (1.25-10 microgram/cm(2)) increased the adhesion of RPLs to RPMCs in a dose-dependent fashion, an effect that was potentiated by interleukin-1beta. These findings were not observed with nonfibrogenic carbonyl iron particles. Crocidolite and chrysotile plus interleukin-1beta also upregulated vascular cell adhesion molecule-1 mRNA and protein expression in RPMCs, and the binding of RPL to asbestos-treated RPMCs was abrogated by anti-vascular cell adhesion molecule-1 antibody. PRLs exposed by intermittent inhalation to crocidolite for 2 wk manifested significantly greater binding to RPMCs than did RPLs from sham-exposed animals. The ability of asbestos fibers to upregulate RPL adhesion to RPMCs may play a role in the induction and/or potentiation of asbestos-induced pleural injury.

Mesothelial cells induce the motility of human ovarian carcinoma cells

The dissemination of ovarian carcinoma cells within the abdominal cavity involves interaction of tumor cells with the peritoneal mesothelium. The aim of our study was to investigate whether mesothelial cells might directly affect the spreading of this tumor by inducing motility and invasiveness of human ovarian carcinoma cells. Serum-free supernatants of cultured human mesothelial cells [conditioned medium (CM)] induced chemotaxis and invasiveness of the human ovarian carcinoma cell lines SK-OV-3, OVCAR-5 and A2780 in a Boyden chamber. Checkerboard analysis indicated that the stimulated motility was prevalently directional. Most of the chemotactic activity was retained by a heparin affinity column, indicating that the motility factor(s) is a heparin-binding protein. Using different monoclonal antibodies (MAbs) directed against chemotactic factors that are secreted by mesothelial cells, we found that chemotaxis was partially prevented (64.8% inhibition) by antibodies against fibronectin (FN). CM also induced haptotactic migration of ovarian carcinoma cells, and anti-FN antibodies significantly inhibited haptotaxis. The presence of FN in the CM was confirmed by Western blot analysis. Our findings suggest that mesothelium plays an active role in inducing the intraperitoneal spread of ovarian carcinoma cells, and point to FN as being one of the main mediators of mesothelium-induced ovarian carcinoma cell motility.

Actinin-4, a novel actin-bundling protein associated with cell motility and cancer invasion

Regulation of the actin cytoskeleton may play a crucial role in cell motility and cancer invasion. We have produced a monoclonal antibody (NCC- Lu-632, IgM, k) reactive with an antigenic protein that is upregulated upon enhanced cell movement. The cDNA for the antigen molecule was found to encode a novel isoform of nonmuscle alpha-actinin. This isoform (designated actinin-4) was concentrated in the cytoplasm where cells were sharply extended and in cells migrating and located at the edge of cell clusters, but was absent from focal adhesion plaques or adherens junctions, where the classic isoform (actinin-1) was concentrated. Actinin-4 shifted steadily from the cytoplasm to the nucleus upon inhibition of phosphatidylinositol 3 kinase or actin depolymerization. The cytoplasmic localization of actinin-4 was closely associated with an infiltrative histological phenotype and correlated significantly with a poorer prognosis in 61 cases of breast cancer. These findings suggest that cytoplasmic actinin-4 regulates the actin cytoskeleton and increases cellular motility and that its inactivation by transfer to the nucleus abolishes the metastatic potential of human cancers.

Identification of semaphorin E as a non-MDR drug resistance gene of human cancers

To improve cancer chemotherapy, a better understanding of the molecular mechanisms of drug resistance is essential. To identify the molecules responsible for drug resistance that is unrelated to MDR1 or MRP gene products, a eukaryotic expression cDNA library of cis-diamminedichloroplatinum(II) (CDDP)-resistant ovarian cancer TYKnuR cells was introduced into Cos-7 cells. After repeated CDDP selection, cDNA homologous to murine semaphorin E was isolated from surviving cells. Human semaphorin E (H-sema E) was overexpressed in CDDP-resistant cell lines and was readily induced not only by diverse chemotherapeutic drugs but also by x-ray and UV irradiation. Transfection of H-sema E conferred a drug-resistant phenotype to CDDP-sensitive cells. In addition, the aberrant expression of H-sema E protein was detected immunohistochemically in 14 of 42 (33.3%) recurrent squamous cell carcinomas removed at autopsy after extensive radiochemotherapy. Recently, another member of the semaphorin family, CD100, was shown to significantly improve the viability of B lymphocytes. These results suggest the involvement of semaphorins in diverse cell survival mechanisms.

Newly marketed tissue markers for malignant mesothelioma: immunoreactivity of rabbit AMAD-2 antiserum compared with monoclonal antibody HBME-1 and a review of the literature on so-called antimesothelioma antibodies

A complementary DNA (cDNA) library was constructed from a human malignant mesothelioma (MM) cell line and a cDNA fragment encoding for a cytoplasmic mesothelial protein recognized by the polyclonal antibody AMAD-1 was then cloned and expressed in Escherichia coli. The purified recombinant protein was used to raise a novel antibody, named AMAD-2, in rabbits. This antibody reacted with normal mesothelium and most MM (15 of 17) on paraffin sections and featured a cytoplasmic labeling. Conversely, AMAD-2 immunostaining of normal and tumor tissues from body sites other than serosal membranes was limited with respect to the proportion of positive specimens and usually less conspicuous than in MM. AMAD-2 immunoreactivity was subsequently compared with staining for HBME-1, another newly marketed antimesothelial monoclonal antibody, concerning the ability to distinguish pleural MM from metastatic pleural tumors of epithelial type. A granular cytoplasmic immunoreactivity for AMAD-2 was present in 50% or more of tumor cells in all 84 MM, regardless of histological type, but also in 3 (7%) of 42 pleural metastases, albeit only focally. HBME-1 was shown in 63 of 66 epithelial MM and in the epithelial component of all 8 mixed MM, with a prevailingly membranous pattern, usually homogeneous and strong, whereas none of the 10 sarcomatous MM was positive. HBME-1 was also expressed in 6 (14%) of 42 pleural metastases in a cytoplasmic or membranous pattern. Compared with HBME-1, AMAD-2 showed a higher degree of specificity and sensitivity for MM. AMAD-2 still proved to be superior to HBME-1, also when sarcomatoid MM were excluded from the assessment. This finding supports the view that AMAD-2 is an antibody highly, although not entirely, specific for the mesothelial lineage, whereas HBME-1 is probably a cell marker more closely related to the epithelial differentiation of MM. Therefore, AMAD-2 is preferable as a positive tissue marker to be incorporated in the optimal immunohistochemical panel for the diagnosis of MM.

Calretinin: a novel immunocytochemical marker for mesothelioma

Immunohistochemistry is a powerful diagnostic adjunct in the differential diagnosis between malignant mesothelioma (especially of the epithelial type) and adenocarcinoma metastatic to the serous membranes. Most of the immunological probes commonly used, however, recognize antigens expressed by the epithelial malignancies and absent from mesothelial cells and mesotheliomas. Probes suitable for the positive identification of mesotheliomas are comparatively scarce and much less commonly used because of their reduced sensitivity and specificity, their unsuitability for staining routinely fixed and embedded tissues, or their lack of commercial availability. We now document that two different polyclonal antisera to calretinin consistently immunostain mesothelial cells and malignant mesotheliomas both in routinely fixed and embedded tissue sections and in cytological preparations of serous effusions. The diagnostic sensitivity of this novel immunocytochemical approach reached 100%, allowing immunostaining of all 44 mesotheliomas investigated, which included five biphasic and three sarcomatoid types. The specificity of calretinin immunoreactivity was checked against 294 adenocarcinomas of different origin (19 serosal metastases and 275 primary tumors potentially able to metastatize to serosal membranes) relevant for the discussion of the differential diagnosis with malignant mesothelioma: only 28 cases showed focal immunoreactivity for calretinin. We conclude that calretinin is a most useful marker for the positive identification of malignant mesotheliomas.

Simultaneous expression of cadherin-11 in signet-ring cell carcinoma and stromal cells of diffuse-type gastric cancer

We examined the expression of cadherin-11, a type II cadherin, in normal human tissues, cell lines and gastric cancer surgical specimens. Cadherin-11 was expressed widely in adult tissues, except the liver. It was expressed in fibroblast, mesothelial cell lines, and in only two signet ring cell carcinomas out of 16 various cancer cell lines. Cadherin-11 expression was detected in both signet ring cell carcinoma cells and surrounding fibroblasts of surgical specimens by in situ hybridization. These results suggest that cadherin-11 may play a role in the formation of diffuse-type gastric cancer through cancer-stromal interactions.