Expression of HER-2/neu receptor protein in adrenal tumors

The HER-2/neu protein is overexpressed in many human carcinomas obtained from different tissues and may represent a useful target for therapy with the commercially available monoclonal antibody trastuzumab (herceptin). Novel therapeutic options are needed for metastasized adrenocortical cancer. Therefore, we studied expression of the HER-2/neu cell surface receptor protein using three different antibodies in 12 adrenal adenomas, 17 adrenocortical carcinomas and 5 pheochromocytomas. Normal adrenals (n = 5) served as controls. One adenoma showed very weak membranous immunostaining with the Dako antibody, two others showed a nonspecific cytoplasmic staining pattern. A nonspecific reaction in the cytoplasm was demonstrable in seven carcinomas with the Novocastra antibody. In all pheochromocytomas, a granular intracytoplasmic and, rarely, slightly membranous immunostaining with the Dako antibody was found. From our data we conclude that specific and significant membranous immunostaining indicating strong overexpression (grade 3) of HER-2/neu protein is not present in adrenocortical tumors. The granular cytoplasmic immunostaining of the medulla may be helpful for differentiation of adrenocortical tumors from pheochromocytomas.     

Immunohistochemical reactivity of a monoclonal antibody prepared against human breast carcinoma

Summary The reactivity profile of an IgM monoclonal antibody, MBR1, raised against the human breast cancer cell line MCF7, was studied in a variety of human tumours and non-neoplastic tissues by light microscopic immunohistochemistry. The range of reactivity included specific types of non-neoplastic epithelial cells and a number of epithelial tumours. Most mammary carcinomas reacted with MBR1, but adenocarcinomas and squamous carcinomas from different sites were also strongly positive. Different patterns of immunoreactivity were apparent in microscopically normal tissues, in tissues with inflammatory changes and in carcinomas. Heterogeneous staining, despite morphological similarities, was documented in neoplastic and non-neoplastic epithelial cells. The reactivity of MBR1 was different from that reported for other monoclonal antibodies, but revealed similarities to that of monoclonal antibodies and polyclonal sera against human milk fat globule membrane.     

Cytokeratin expression in adrenocortical neoplasia: an immunohistochemical and biochemical study with implications for the differential diagnosis of adrenocortical, hepatocellular, and renal cell carcinoma.

The immunostaining patterns of adrenocortical tumors are not clearly defined, primarily due to their inconsistent expression of cytokeratins (CK). To address this issue and to investigate whether adrenocortical tumors can be immunohistochemically differentiated from histologically similar tumors arising from the kidney and liver, we studied four normal adrenal glands, two adrenocortical adenomas (ACAs), 31 adrenocortical carcinomas (ACCs), 37 renal cell carcinomas (RCCs), and 33 hepatocellular carcinomas (HCCs) with anti-CK antibodies AE1, CAM 5.2, UCD/PR10.11, 35BH11, PKK1, and Ks19.1, as well as antibodies to vimentin (VIM), epithelial membrane antigen (EMA), and HMFG-2. Normal adrenal cortical cells showed variable staining with all anti-CK antibodies on fixed and frozen sections. In contrast, only one of two fixed ACAs stained with a single anti-CK, although both neoplasms reacted with multiple anti-CK antibodies on frozen sections. Similarly, 20 of 31 fixed ACCs contained VIM, but only one tumor stained for CK; frozen sections of this and another, previously negative tumor, however, stained with most of the anti-CK antibodies tested. One-dimensional Western immunoblot analysis confirmed the presence of CKs 18 and 19 in two examples of normal adrenal cortex, one ACA, and the ACC immunohistochemically positive on fixed and frozen sections, with CK 19 identified in the ACC that was positive on frozen section alone. All fixed HCCs and most RCCs stained with multiple anti-CK antibodies (33 and 34 cases, respectively), with a proportion of tumors positive for VIM (six and 22 cases, respectively), EMA (seven and 30 cases, respectively), and HMFG-2 (15 and 28 cases, respectively). The results suggest that CK expression is diminished in most adrenocortical tumors to levels too low to be recognized following the deleterious effects of fixation. While the immunohistochemical absence of CK, EMA, and HMFG-2 in fixed sections in the majority of ACCs is distinctive, sufficient phenotypic overlap exists such that differentiation between RCC and HCC may not be possible in an individual case.     

Immunocytochemical differential diagnosis of adrenocortical neoplasms using the monoclonal antibody D11

Summary The monoclonal antibody D11 is a valuable aid in the accurate typing of adrenal tumours as, in formalin-fixed, paraffin-embedding material, strong nuclear D11 positivity was observed only in adrenocortical cells in 190 neoplasms (including 100 adrenal tumours). This pattern was demonstrated for all zona glomerulosa cells in 27 normal adrenals and for the neoplastic cells of 15 adrenocortical adenomas derived from that zone, as judged from clinically evident hyperaldosteronism. Normal cells of zona fasciculata and reticularis also showed strong diffuse D11 immunostaining and the same nuclear plus cytoplasmic D11 reactivity was evident in 15 benign and malignant adrenocortical neoplasms derived from these zones, documented by hypercortisolism. Cytoplasmic and/or nuclear D11 staining made topohistogenetic typing possible in 15 non-functioning cortical tumours. D11 immunostaining gave negative results in 50 specimens containing normal, hyperplastic and neoplastic adrenomedullary cells. In addition, absence of D11 reactivity was recorded in 4 adrenal metastases of extra-adrenal carcinomas, 5 paragangliomas, 25 primary renal carcinomas and 59 of 60 primary thyroid carcinomas. D11 immunocytochemistry allows the accurate typing of benign and malignant adrenocortical neoplasms, irrespective of histology and function. With this method, primary adrenocortical tumours can be separated from carcinomas metastatic to the adrenal gland, including secondary tumours of similar phenotype (such as renal carcinomas). By exclusion, D11 negativity provides evidence of the medullary origin of primary adrenal tumours even in the absence of clinical, structural, histochemical and conventional immunohistochemical indicators of phaeochromocytoma. Dedicated to Prof. Dr. Dr. h.c. mult. Wilhelm Doerr on the occasion of his 75th birthday. This study has been sponsored by the Deutsche Forschungsgemeinschaft and the Hamburger Krebsgesellschaft and was presented in part at the 80th Annual Meeting of the American Association for Cancer Research, San Francisco, California, 24–27 May 1989 (Schr?der et al. 1989)     

Expression of intermediate filament proteins in adrenal cortex and related tumours

The intermediate filament profile of adrenal cortex and its related tumours has been evaluated. Most adrenocortical cells contained cytokeratin 8 and 18 as demonstrated by monoclonal antibodies CAM 5.2, M20, M9 and RGE53. Cytokeratin immunoreactivity was not confined to a functional zone of the adrenal cortex. Only a small number of the adrenocortical cells showed vimentin immunoreactivity. From normal adrenal cortex through adenomas, to carcinomas, there is a progressive decrease or even loss of cytokeratin immunoreactivity and an increase in vimentin immunoreactivity. Aberrant cytokeratin expression was not found in adrenocortical adenomas and carcinomas with the antibodies used. Awareness of the possible absence of cytokeratin immunoreactivity in adrenocortical carcinomas is important whenever antibodies to cytokeratins and vimentin are used for diagnostic purposes in poorly differentiated neoplasms.     

Monoclonal antibody HISL-19 as an immunocytochemical probe for neuroendocrine differentiation. Its application in diagnostic pathology.

The monoclonal islet cell antibody HISL-19 was generated after immunization of BALB/c mice with human islet cell preparations. Besides reactivity with all cells of the human pancreatic islet, MAb HISL-19 also reacted with other cells of the diffuse neuroendocrine system, including anterior pituitary cells, C cells of the thyroid, endocrine cells of the gut and bronchus, the adrenal medulla, and central and peripheral neurons. In this study the authors screened a series of 53 neuroendocrine and 71 nonneuroendocrine tumors for their reactivity with MAb HISL-19 using an indirect immunoperoxidase technique on formalin-fixed and Paraplast-embedded sections. MAb HISL-19 reacted strongly with all insulomas (10), carcinoids (8), C-cell carcinomas of the thyroid (8), pituitary adenomas (6), neuroendocrine carcinomas of the skin (4), paragangliomas of the carotid body (3), and pheochromocytomas (2) tested. Neuroblastomas (3), oat-cell carcinomas of the lung (2), and melanomas (4) exhibited only very few immunoreactive cells scattered throughout the tumor or remained unstained with MAb HISL-19. With the exception of one lobular carcinoma of the breast (1/3), one adenocarcinoma of the endometrium (1/4), and one adenocarcinoma of the stomach (1/6), nonneuroendocrine tumors were negative with MAb HISL-19. Biochemical findings obtained by SDS-PAGE, "Western" immunoblotting, immunoaffinity chromatography, and absorption experiments indicate that the MAb HISL-19-defined antigen is not related to neuron specific enolase. Because the epitope recognized by MAb HISL-19 is well preserved in formalin-fixed and routinely processed tissues, this monoclonal antibody finds potential applications in diagnostic pathology as an indicator for neuroendocrine cells and their neoplasms.     

N-cadherin expression in adrenal tumors: upregulation in malignant pheochromocytoma and downregulation in adrenocortical carcinoma

Cell adhesion molecules (CAMs) are important regulators of tumor growth. The aim of the present study was to evaluate the expression pattern of CAMs in adrenal tumors regarding origin (cortex vs medulla) and biologic behavior (benign vs malignant). Eighty-seven adrenal tumors were investigated by immunocytochemistry (ICC) using monoclonal antibodies against N-cadherin (NCAD), E-cadherin (ECAD), neural cell adhesion molecule (NCAM), and CD44. Western blotting was performed on 30 tumors using the same antibodies. Markers for proliferation (Ki-67) and catecholamine synthesis (tyrosine hydroxylase) were also analyzed in tumors by ICC. NCAD was expressed in 12/27 benign pheochromocytomas (BPCs) (12 familial cases), 8/8 malignant pheochromocytomas (MPCs), 28/30 adrenocortical adenomas, and 9/22 adrenocortical carcinomas. ECAD was expressed in 0/27 BPCs, 0/8 MPCs, 0/30 adrenocortical adenomas, and 2/22 adrenocortical carcinomas. NCAM was expressed in 26/27 BPCs, 7/8 MPCs, 21/30 adrenocrotical adenomas, and 17/22 adrenocortical carcinomas. CD44 was expressed in 23/27 BPCs, 6/8 MPCs, 7/30 adrenocortical adenomas, and 4/22 adrenocortical carcinomas. Both cortical and medullary adrenal tumors expressed NCAD, NCAM, and CD44 but were devoid of ECAD. The expression of CD44 and NCAM did not correlate with the malignant potential of tumors. NCAD was upregulated in MPCs, but downregulated in adrenocortical carcinoma. Thus, NCAD appears to be involved in the development of both cortical and medullary adrenal tumors.     

Murine monoclonal antibody to mitochondria reacts with the 72 kD antigen of primary biliary cirrhosis.

BALB/c mice were immunized with canine gastric mucosal cells enriched to 70% for parietal cells, to produce monoclonal antibodies (MoAb). Three MoAb, FMM-4C5, FMM-4C9 and FMM-2B2, were obtained which reacted by indirect immunofluorescence with gastric parietal cells and kidney tubules, predominantly distal kidney tubules, with a pattern similar to that of the M2 autoantibodies of primary biliary cirrhosis (PBC). The antibodies also reacted with tissues from rabbit, rat, pig, human and with rod-shaped structures in acetone-fixed monolayer cultures of human fibroblasts and HEp 2 cells. FMM-4C9 and FMM-2B2 reacted with tissues from BALB/c mice but FMM-4C5 did not. Immunoblots of FMM-4C5 with mitochondrial fractions showed that the antibody recognized a 63 kD antigen from dog stomach, rat kidney and rat liver, and a 72 kD antigen from human placenta; mouse preparations were not reactive. The antigen co-migrated with that recognized by serum from cases of PBC and some cases of progressive systemic sclerosis. Absorption of the mitochondrial fraction with PBC sera removed reactivity by immunoblotting with the murine autoantibody and vice versa. Two dimension immunoblots showed that the murine and human antibodies recognized an identical series of paired 'spots'. FMM-4C5 also reacted by immunoblotting with a rat recombinant mitochondrial polypeptide which has disease-specific reactivity with PBC sera. Absorption with recombinant polypeptide removed anti-mitochondrial activity by immunoblotting and immunofluorescence. These observations suggest that the MoAb FMM-4C5 recognizes part of the same 72 kD molecule recognized by human PBC sera. The murine monoclonal antibodies should be useful probes for further studies of the structure, function and possible pathogenicity of the 72 kD autoantigen.     

Differential diagnosis of benign epithelial proliferations and carcinomas of the breast using antibodies to cytokeratins

The immunohistochemical reactivity on frozen sections of diverse benign and malignant epithelial proliferations of human breast tissue from 156 patients was examined using antibodies to different cytokeratins. Antibodies recognizing cytokeratins 18 and 19 reacted with luminal epithelial cells but not with myoepithelial cells of normal mammary gland, cystic disease, adenosis, papilloma, and fibroadenoma or with a subpopulation of proliferating cells in sclerosing adenosis and epitheliosis. These antibodies reacted with the tumor cells of all in situ and invasive carcinomas. KA1 antibody, which by one- and two-dimensional gel electrophoresis and immunoblotting was shown to bind preferentially to cytokeratin 14 in a complex with cytokeratin 5, reacted with the nonproliferating myoepithelium of normal gland, cystic disease, adenosis, papilloma, fibroadenoma, and in situ carcinoma; it also reacted with a subpopulation of proliferating cells in sclerosing adenosis and epitheliosis (papillomatosis) but was negative with the tumor cells of all preinvasive and most invasive carcinomas. In adenotic and epitheliotic proliferations, groups of cells were identified that reacted strongly with KA1 antibody in addition to antibodies to cytokeratins 18 and 19. The data are discussed with respect to epithelial cell heterogeneity in the breast. We show that by using such antibodies, benign epithelial proliferations are clearly distinguished from carcinomas.     

Three monoclonal antibodies defining distinct differentiation antigens associated with different high molecular weight polypeptides on the surface of human embryonal carcinoma cells

Two monoclonal antibodies (TRA-1-60 and TRA-1-81) recognizing distinct cell surface antigens on human embryonal carcinoma (EC) cells were produced and characterized. These antibodies reacted strongly with undifferentiated human EC cells in indirect radioimmunoassays (RIA) and immunofluorescence (IF) assays, but only weakly or not at all with cells derived from pluripotent EC cells differentiating in vitro or in xenograft tumors, nor with other germ cell tumor cell lines that did not also express the typical features of human EC cells. They did not react with murine teratocarcinoma cell lines. A survey of other human tumor cell lines and normal human tissues disclosed that molecules recognized by these antibodies are not confined to human EC cells but that cross-reacting epitopes appear on several neoplastic and normal tissues, although in a different anatomical pattern for each antibody. Both antibodies immunoprecipitated a major polypeptide (apparent molecular weight approximately 240,000) and a minor polypeptide (apparent molecular weight approximately 415,000) from lysates of 125I surface-labeled human EC cells, in this respect resembling another monoclonal antibody, 8-7D, previously described by Blaineau et al. (1,2) However, sequential immunoprecipitation revealed that each of the three antibodies reacted with different molecules of slightly different molecular weights. The epitopes defined by the present antibodies differ from those recognized by the other human EC cell-specific monoclonal antibodies that have been described and provide new markers for studying the differentiation of pluripotent human EC cells.     

Monoclonal antibody directed against neuroendocrine properties of both normal and malignant cells

A monoclonal antibody, 6H7, was produced by the immunization of small cell carcinoma of the lung (SCCL). Immunohistochemical examination indicated that 6H7 reacted not only with SCCL but also various neuronal and/or endocrine tumors such as neuroblastoma, pheochromocytoma, carcinoid and adrenal cortical tumors. 6H7 was also reactive with normal neuroendocrine tissues including brain, spinal cord, thyroid follicular cells, pancreatic islet cells and adrenal cells. 6H7 did not react with squamous cell carcinomas, one large cell carcinoma or most adenocarcinomas of the lung, or carcinomas of the stomach, colon, pancreas, breast and esophagus. The antigen recognized by 6H7 was analyzed on gel filtration after purification of the antigen by liquid chromatography which indicated the molecular weight of the antigen to be 270,000-300,000. From SDS-PAGE analysis the antigen reactive with 6H7 appeared to consist of polypeptide dimers of 128,000.     

Immunohistochemical localization of the ACTH (MC-2) receptor in the rat placenta and adrenal gland

The adrenocorticotropic hormone (ACTH) acts on adrenocortical cells and promotes steroidogenesis by specific binding to the ACTH (MC-2) receptor (ACTHR). To gain an insight into ACTH action on local steroidogenic organs, we examined the immunohistochemical expression of ACTHR in rat adrenal glands and placentas during the mid-late gestation period. Antibodies against synthetic ACTHR peptides were raised in rabbits, and Western blot analysis showed that the antibody reacted with specific proteins in the rat adrenal glands and placentas. The peroxidase-labeled antibody method revealed that ACTHR was distributed in the plasma membrane and cytoplasm of the parenchymal cells of the adrenocortical zona fasciculata. In the placenta, ACTHR was distributed in the junctional spongiotrophoblasts at day 13 of gestation--with a gradual decrease in the staining during the gestational period, whereas ACTHR appeared in the placental labyrinthine cells from days 15 to 19 of gestation. Immunoelectron microscopy revealed that ACTHR was also localized in the ribosomes of the fasciculata cells and the labyrinthine cells. Our findings suggest that ACTHR may play a physiological role in steroidogenesis in the adrenal cortical parenchymal cells as well as in the trophoblasts of rat placentas during mid-late gestation.     

Monoclonal antibodies against the GP-2 subunit of laminin

Two stable rat X mouse hybridoma lines have been isolated. These hybridoma lines produce IgG antibodies directed against the polypeptide portion of the GP-2 subunit of laminin. Antibodies produced by the hybridomas have been shown to be IgG 2b (lambda) and IgG 2a (kappa), respectively. In competition ELISA assays the monoclonal antibodies exhibited different binding affinities for laminin. Furthermore, the two antibodies were partially additive in their reactivity to laminin. Preliminary results also indicate that the antibodies recognized different antigenic determinants in laminin as determined by their reactivity to basement membranes in human and mouse tissues. The monoclonal antibody designated LAM-I stained a broad spectrum of human and mouse tissues; the other monoclonal antibody LAM-II reacted with mouse, but not human tissues. The results indicate that these monoclonal antibodies could be utilized to explore the organization of laminin in basement membranes of different tissues and species.     

Immunohistochemical staining of normal, hyperplastic, and neoplastic adrenal cortex with a monoclonal antibody against alpha inhibin.

AIMS: To investigate the immunohisto-chemical staining of normal, hyperplastic, and neoplastic adrenal cortex with a monoclonal antibody against alpha inhibin. Also, to determine whether immunostaining with this antibody is useful in differentiating between adrenal cortical neoplasms and other tumours involving the adrenal gland that might mimic them. METHODS: Normal adrenal tissue (n = 20) and specimens from cases of adrenal hyperplasia (n = 13), adrenal cortical adenoma (n = 15), adrenal cortical carcinoma (n = 4), phaeochromocytoma (n = 8), and adrenal metastatic tumour (n = 7) were stained with a monoclonal antibody against the alpha subunit of human inhibin. RESULTS: Positive staining with the anti-alpha inhibin monoclonal antibody was seen in all normal adrenal glands. Immunoreactivity was largely confined to the inner cell layers of the adrenal cortex, with no staining of the adrenal medulla. All hyperplastic adrenal glands and adrenal cortical adenomas and carcinomas were also immunoreactive. The other tumours studied were negative. CONCLUSIONS: There is consistent immunoreactivity with the anti-alpha inhibin monoclonal antibody in normal adrenal cortex and in hyperplastic and neoplastic adrenal cortical lesions. In the normal adrenal cortex, positive staining is mainly confined to the zona reticularis. Other neoplasms involving the adrenal gland are negative. Immunohistochemical staining with anti-alpha inhibin monoclonal antibody, performed as part of a panel, may prove to be of value in the distinction between adrenal cortical carcinoma and phaeochromocytoma or metastatic tumour.     

Conserved antigen expression in epithelial tumors recognized by monoclonal antibody 4A9 generated against canine mammary carcinoma cells

Hybridoma-derived murine monoclonal antibodies (MoAbs) were generated by fusing P3X63-Ag8.653 myeloma cells with splenic cells from BALB/c mouse which had been immunized with viable canine mammary adenocarcinoma cells, CMT-2. Fifteen MoAbs were shown to react with immunizing cells in indirect immunofluorescence (IFA) and enzyme-linked immunosorbent (ELISA) assays. The reactivity of one IgM MoAb, designated 4A9, was evaluated. The antigen recognized by 4A9 on CMT-2 cells appeared to be localized both in cell membrane and cytoplasm against fixed and unfixed preparations by IFA. The 4A9 MoAb was found to bind with four of five canine mammary carcinoma cell lines while no binding was detected with normal fibroblastic cell lines. In vivo tissue distribution of 4A9 antigen was evaluated by indirect immunoperoxidase (IP) assay against formalin-fixed, paraffin-embedded sections of normal and neoplastic tissues. 4A9 MoAb reacted strongly to moderately with 75% of mammary carcinomas, moderately to weakly with 57% of benign mammary tumors, and strongly with squamous cell and perianal gland carcinomas (100%), interstitial cell tumors (100%), transitional cell carcinomas (43%), lung adenocarcinomas (40%), colon carcinomas (33%), and pancreatic adenocarcinomas (20%). Moderate to weak staining was detected with granulosa cell tumors (25%) and apocrine gland adenocarcinomas (50%). Strong reactivity with perianal gland carcinomas contrasted to no reactivity with perianal gland adenomas. No immunostaining was detected with a large variety and number of normal adult and fetal tissues tested; negligible and very restricted staining was observed in a few adult and fetal tissues. Normal mammary gland was negative. Since the antigen is expressed on the cell surface and in the cytoplasm of most mammary carcinoma cells and a variety of other epithelial tumor cells, the 4A9 antibody may have potential application in diagnosis and management of canine mammary cancer and a variety of other epithelial tumors.     

抗人白细胞单克隆抗体1C34-5与正常及肿瘤组织或细胞的反应性

用免疫组化方法及EUSA测检研究抗人白细胞单克隆抗体1C34-5与正常及肿瘤细胞组织的反应性,发现1C34-5仅与正常的白细胞和淋巴造血组织来源的肿瘤细胞反应。在所观察的1例毛细胞白血病、10例恶性淋巴病,2例何杰金氏病的肿瘤组织均与1C34-5呈不同程度的阳性反应,而31例各种不同类型非淋巴造血组织来源的肿瘤均为阴性反应。浸润到肿瘤细胞间或邻近部位的淋巴样细胞也为阳性反应。此抗体在辅助鉴别形态学难以区分的小圆细胞癌和淋巴瘤的病理诊断中,将有一定意义。此外也为观察判断转移癌细胞分布及浸润程度,以及宿主抗肿瘤的免疫反应提供了一种新手段。     

Analysis of the thymic microenvironment by monoclonal antibodies with special reference to thymic nurse cells

Two hybridoma cell lines secreting monoclonal antibodies against stromal tissues of mouse thymus were produced using the spleen cells of BALB/C mice immunized with newborn thymic homogenate of C57BL/6 mice emulsified in Freund's complete adjuvant. The monoclonal antibody Th-3 reacted with stromal cells in the thymic cortex and the monoclonal antibody Th-4 reacted with stromal cells in the thymic medulla. The stromal cells revealed by Th-3 showed a meshwork structure in the cortex, and formed a monolayered border at the cortical surface and around the vasculature. Each mesh of this structure was connected to each other, forming a complex labyrinth and being open toward the medullary area. Neither lymphoid cells nor any cells in any other organs were reacted with this Th-3 antibody. However, the reactivity of Th-3 with the thymic cortical stromal cells was observed not only in C57BL/6 mice which had been used as source of antigen, but also in other strains of mice such as C3H and BALB/C. Immunoelectron microscopy revealed that Th-3 monoclonal antibody was reactive with some component, diffusely present in the cytoplasm of cortical epithelial cells. The pattern of Th-3 positive meshwork in the thymic cortex was quite similar to that stained by either anti-IA or anti-IE antibody, but the Th-3 positive reaction was not inhibited by these anti-IA and anti-IE antibodies. Thymic nurse cells prepared by the method of Wekerle were positive for Th-3 antibody. On the contrary, Th-4 reacted only with epithelial cells in the thymic medulla. It was suggested that Th-3 monoclonal antibody detected some antigen specific to so called thymic nurse cells.     

Immunofluorescence microscopic evaluation of the intermediate filament expression of the adrenal cortex and medulla and their tumors.

Normal adrenal glands (10 specimens) and adrenal gland tumors (58 cases) were immunohistochemically evaluated for different types of intermediate filament (IF) proteins. Some of the normal cortical cells showed cytokeratin positivity, and no positivity was seen for epidermal keratin or other types of IF. In the adrenal medulla, neurofilament positivity was seen in nerve axons, some ganglion cells, and chromaffin cells; and cytokeratin-positive cells could not be detected. Only the vascular and connective tissue elements showed vimentin positivity in both cortical and medullary areas. In half of the cortical carcinomas (13/25), cytokeratin-positive tumor cells were found. Furthermore, vimentin-positive tumor cells were present in 10 of 25 cases, in some of them together with cytokeratin-positive cells. Thus, the results show heterogeneity among the adrenal cortical carcinomas. Interestingly, many benign adrenal cortical tissues and some carcinomas lacked immunoreactivity for all types of IF, suggesting a poorly developed IF system in these tissues. In contrast to adrenal cortical tumors, pheochromocytomas contained neurofilamentlike immunoreactivity. These results reflect the different cellular nature of adrenal cortical and medullary tumors, which apparently can be distinguished from each other with antibodies to intermediate filament proteins.     

Monoclonal antibodies to human malignant mesothelioma

Murine monoclonal antibodies were used to identify tumor-cell membrane antigens on a new human mesothelioma cell line. Hybridomas were constructed by fusing SP2/0 mouse myeloma cells with spleen cells from Balb/C mice immunized by the human mesothelioma cell line MT-1. Hybridoma antibody was detected in 55/672 microculture wells that reacted to these MT-1 tumor cells by an indirect¹²⁵I-protein A binding assay. Six cultures produced antibody binding selectively to the MT-1 tumor cells but not to a human lymphoblastoid cell line. These six hybridomas were cloned: three were IgG and three were IgM antibodies. One monoclonal, MAb 45, reacted with 4 of 7 human mesothelioma cell lines but with only 1 of 11 carcinomas, 1 of 3 sarcomas, 4 of 11 melanomas, and 0 of 5 lymphoid lines. The other five monoclonals had a much broader cross-reactivity. Using an immunoperoxidase technique, MAb 45 bound to mixed-type malignant mesotheliomas but not to normal lung and pleura. The specificity of MAb 45 for diffuse mesotheliomas and the low cross-reactivity with carcinomas and normal adjacent tissues suggest that this monoclonal may be clinically useful.