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.

The in-vitro hematopoietic capacity of the adult human mesothelial cell: a model of cell differentiation induced by the structure of the microenvironment.

Upon exposure to collagen sponges, cultured adult human mesothelial cells were shown to differentiate into hematopoietic cells similar to those of the red bone marrow. This transformation was confirmed by morphological analysis and by cell immunoreactivity toward specific antibodies directed to antigens of the hematopoietic cell lines at various stages of differentiation. Besides demonstrating that the pluri-potentiality of the mesothelium persist into adulthood, this observation suggests that the process of differentiation may also be influenced by the structural organization of the microenvironment hosting the mesothelial cells.

Quantitative analysis of nucleoli and nucleolar organizer regions in cultured primary human normal, reactive and malignant mesothelial cells.

The number and the size of silver-stained intranuclear granules, which correspond to the nucleolus and nucleolar organizer regions, have been determined by means of quantitative methods in cultured primary human mesothelial cells obtained from normal, reactive and malignant mesothelium. The mean values per nucleus of the number, the total area, the average area, and the relative area of the silver-stained granules and the mean nuclear area were determined for each of the three conditions. Normal, reactive and malignant mesothelial cells differed significantly in all the features. These findings at the optical level reflect the differing rate of the nucleolar biosynthetic activity related to the different biological properties of the three cell types, and the features can be useful morphometric descriptors in the diagnostic pathology of the mesothelium.

Mitogenic effects of a mesothelial cell growth factor: evidence for a potential autocrine regulation of normal and malignant mesothelial cell proliferation.

We have investigated the growth-factor-like activity of a approximately 200-kDa, IP 8.3, cytoplasmic glycoprotein, the expression of which appears to be restricted to normal and malignant human mesothelium. This substance stimulated the growth of human mesothelioma cell cultures at greater rates than did foetal calf serum, but it failed to induce proliferation of lung carcinoma cell cultures. In addition, we have tried to trace the biosynthetic pathway of this mitogenic factor in normal human mesothelial cells by means of immuno-electron microscopy with a polyclonal antibody directed against this molecule. Positive immunogold labelling was found in the lumina of the cisternae of the endoplasmic reticulum, to a lesser extent on the outer surface of the plasma membrane, and also in structures corresponding to the coated pits. These ultrastructural findings are consistent with the hypothesis of the glycosylation of the newly synthesized protein in the endoplasmic reticulum and the subsequent uptake of the secreted molecule, which accumulates in the coated pits before internalization. The results suggest that this mitogenic glycoprotein could play a role in an autocrine growth control mechanism influencing mesothelial cell proliferation.

Synovial sarcoma: a new approach to the histological classification and a comparison with malignant mesothelioma. Immunohistochemical study with anti-mesothelial cell serum.

Routine paraffin-embedded sections from synovial sarcomas in 70 patients were stained immunohistochemically with monoclonal anti-cytokeratin antibody and serum against mesothelial cells. Positive reactions occurred in the epithelioid cells of biphasic tumors only. On the ground of the reaction with anti-mesothelial serum a hypothetical scheme of cell differentiation in synovial sarcoma was set up.

Cytologic diagnosis of malignant mesothelioma in serous effusions using an antimesothelial-cell antibody.

Differentiating mesothelioma, reactive mesothelium, and adenocarcinoma in serous effusions is often difficult, despite the application of ancillary techniques in support of the traditional cytomorphologic criteria. A polyclonal antimesothelial-cell antibody recently developed by our group was evaluated as a histogenetic marker on a series of primary (n = 12) and metastatic (n = 12) malignant effusions. Immunostaining was performed on paraffin sections from cell blocks. All mesothelioma effusions stained positive for the antibody, whereas, in contrast, all metastatic carcinoma specimens failed to react. These results (100 percent specificity and 100% sensitivity for mesothelioma) provide a basis for a reliable use of the antibody in the cytologic examination of suspicious or malignant serous effusions.

A new insight into the histogenesis of 'mesodermomas'--malignant mesotheliomas.

A myogenic phenotype was induced in cultures of human mesothelial cells treated for 72 h with atrazine, a triazine derivative. Immunoreactivity for both myosin and myoglobin was detected in a large number of these cells, irrespective of their polygonal or spindle morphology, whereas no expression of desmin was observed. These findings support the embryological identity of mesothelium and mesoderm, the former being, in the post-embryonic stage, potentially capable of differentiation along the same lineages which the latter normally displays during embryogenesis. In the light of this concept it can be assumed that primary malignancies arising from the mesothelium have the competence to express the pluripotent nature of embryonic mesoderm, and hence the term mesodermoma is appropriate for this group of tumours, including mesotheliomas in a classical sense. A postulated mechanism for the phenotypic change of mesothelial cells is also outlined, involving atrazine conversion to 5-aza-chloro-cytidine, a probable DNA hypomethylating and gene activating agent, like its analogue 5-azacytidine.

A one-year carcinogenicity study with 2,6-dichlorobenzonitrile (Dichlobenil) in male Swiss mice: preliminary note.

2,6-Dichlorobenzonitrile (Dichlobenil) is the active principle of a commercial herbicide that was previously shown to be carcinogenic for animals. Dichlobenil was administered to male Swiss albino mice in order to assess the possible oncogenic properties of the active principle alone. The substance at 2 ppm concentration was injected (0.0005 mg/injection) either by subcutaneous or intraperitoneal route to 2 randomized groups of 30 animals each every third day for 13 times. Dichlobenil induced a significant increase of malignant tumors (lymphoma, mesothelioma, hepatocellular carcinoma, and pulmonary alveologenic carcinoma) with respect to the controls (p less than 0.01 in both treated groups). As for tumor histotypes, only lymphoma incidence was significantly increased in the intraperitoneally treated animals (p less than 0.05). Dichlobenil can be suspected of being a possible carcinogen in Swiss mice but the mechanism of its action is not precisely known.

Use of monoclonal antibody B72.3 as a marker of metastatic carcinoma cells in neoplastic effusions.

The value of monoclonal antibody B72.3 as a diagnostic discriminator between mesothelioma and carcinoma cells in malignant effusions was assessed using the ABC method in a series of cell blocks prepared from centrifuged fluids. These were obtained from either pleural or peritoneal neoplastic effusions in patients with histologically verified malignant mesothelioma (n:10) or carcinoma (n:20). Reactivity with MAb B72.3 in at least 10% or more of tumour cells was found in 16 (80%) out of 20 metastatic carcinoma, whereas 2 mesotheliomas displayed positive immunostaining in less than 5% and approximately 20% of the malignant cells respectively. Reactive mesothelial cells were consistently non-immunostained. These results suggest that B72.3 positivity in greater than 10% of tumour cells is certainly indicative, but not absolutely diagnostic, of a metastatic origin of malignant effusions.

Putative mesothelial cell growth-promoting activity of a cytoplasmic protein expressed by the mesothelial cell. A preliminary report.

Mesothelioma cells produce a cytoplasmic protein unique to primary tumours of the mesothelium which induces the in vitro proliferation of human mesothelial cells in a dose-dependent fashion. When a polyclonal antibody to this protein was added to cultures of human mesothelioma cells, inhibition of their growth occurred. These results provide evidence for a growth-factor-like role of this mesothelial protein that may act through an autocrine mechanism.

New marker for mesothelioma: an immunoperoxidase study.

An antibody was raised against a protein isolated from the cytoplasm of mesothelioma cells. It was subsequently used in an immunoperoxidase procedure on formalin fixed, paraffin embedded tissue sections. A representative sample of benign and malignant tumours from all the systems of the human body was examined. All the tumours derived from coelomic surfaces (mesotheliomas of pleura, peritoneum, and ovary, and adenomatoid tumour of epididymis) reacted with the antibody. No other tumour tested in this study expressed the protein. These findings indicate that the antibody may be useful in the identification of mesothelioma cells in both histological and cytological diagnostic routine practice when morphological interpretation is in doubt.

Carcinogenicity testing of atrazine: preliminary report on a 13-month study on male Swiss albino mice treated by intraperitoneal administration.

A statistically significant increase (p less than 0.001) of lymphomas (4 of plasmacell type and two of histiocytic type) was found in a group of 30 Swiss albino mice which were given intraperitoneally 0.25 cc of a 2 ppm solution of atrazine for 13 times every third day to total administration of 0.26 mg of Atrazine/kg of body weight. Lymphomas arising in two groups of 50 controls was 0 and 1 respectively.

Primary malignant melanoma of the female urethral meatus.

The case of a 79-year-old woman with a malignant melanoma of the urethral meatus is reported. Melanomas originating from the urethra are exceedingly rare. Histogenetic theories are reviewed. Clinical presentation and therapeutic approach are discussed.

Androgenic juvenile granulosa cell tumour. Case report.

An androgenic juvenile granulosa cell tumour of the ovary in a postmenarcheal girl is presented. Distinctive histological features of this variant are stressed and virilizing effects are explained by an immunohistochemical study of hormones produced by granulosa and theca cells.

Ovarian mesothelial tumors and herbicides: a case-control study.

The ovarian cancer risk from herbicide exposure has been studied in a hospital-based, case-control study after some of these compounds have been shown to be carcinogenic for animals. This study includes 60 cases of primary mesothelial ovarian tumors and 127 controls with non-ovarian malignancies drawn from the same file and matched by year of diagnosis, age and residence. A positive association (relative risk 4.38) has been found between herbicide exposure and ovarian mesotheliomas.