Preclinical development of siRNA therapeutics for AL amyloidosis.

Amyloid light chain (AL) amyloidosis is a rare hematologic disorder characterized by the accumulation of a misfolded monoclonal immunoglobulin (Ig) light chain (LC) as fibrillar protein deposits. Current treatments, including cytotoxic chemotherapy and immunomodulatory therapy, are directed at killing the plasma cells that produce the LCs, but have significant toxicity for other cell types. We have designed small interfering RNAs (siRNAs) targeting the amyloidogenic LC messenger RNA (mRNA) in order to reduce expression of the amyloid precursor protein. Using nanomolar concentrations of siRNAs, we have inhibited synthesis of LC in transfected cells in vitro in a dose-dependent fashion. Furthermore, in an in vivo plasmacytoma mouse model of AL amyloidosis, we have demonstrated that these siRNAs can significantly reduce local production and circulating levels of LC. This model system highlights the therapeutic potential of siRNA for AL amyloidosis.

Cathepsin B activity and protein levels in thyroid carcinoma, Graves' disease, and multinodular goiters.

Cathepsin B (CB) is involved in the hydrolysis of thyroglobulin (Tg) and thought to be regulated by thyroid stimulating hormone (TSH) in the normal thyroid. Our analyses of 91 thyroid tissues from 71 patients with Graves' disease (GD), multinodular goiter (MNG), papillary carcinoma (PC), or follicular carcinoma (FC), demonstrated a 2-fold increase in expression of CB in GD and an average increase of 1.5-fold in MNG (varying from 10-fold below normal to 6-fold above normal in MNG nodules), as might be predicted by the altered functional status of thyroid follicular cells in those diseases. However, CB activity was not downregulated in conjunction with the known "blocking effect" of malignancy on many thyroid functions, but rather increased on average 9-fold in papillary carcinomas (n = 33), and also showed a marked increase in 2 follicular carcinomas. Activity measurements were confirmed by CB protein detection on Western blot with moderately increased CB protein levels demonstrated in GD, variable expression in nodules of MNG, and markedly increased protein expression in carcinomas. In all diseased states, increased protein was detected primarily as overexpression of the 27 kd heavy chain of 2-chain mature CB and less frequently as overexpression of 31 kd single-chain mature CB. However, an additional 35 kd protein form was noted in 3 of 9 PCs, 1 of 2 FCs, and 1 of 4 GD cases but in none of 10 MNG cases. In conjunction with elevated CB activity plus additional protein bands on Western blots, altered patterns of CB immunohistochemical staining were observed, irrespective of the type of thyroid disease, suggesting certain common changes in CB expression, posttranslational processing, and vesicular trafficking. In summary, GD and MNG thyroid tissues demonstrated altered CB expression in keeping with predicted functional changes in thyroid follicular cells, while increased CB expression in carcinomas indicated a more pathological role for CB in thyroid cancers, possibly related to the processes of invasion or metastasis.

Response of lymphoepithelial parotid cysts to antiretroviral treatment in HIV-infected adults.

BACKGROUND: Surgical resection has been the usual therapy for HIV-infected patients with lymphoepithelial parotid cysts. OBJECTIVE: To study antiretroviral therapy for lymphoepithelial parotid cysts. DESIGN: Case series. SETTING: HIV outpatient clinics. PATIENTS: HIV-infected patients with lymphoepithelial parotid cysts. INTERVENTION: Antiretroviral therapy. MEASUREMENTS: Change in size of the parotid cyst, CD4 lymphocyte count, and HIV viral load. RESULTS: Nine HIV-infected adults presented with chronic, large parotid cysts, eight of which were bilateral. In at least seven patients, the cysts were the initial sign of HIV infection. In six patients, the cysts resolved completely with combination antiretroviral therapy. Four of these patients also received prednisone. Three patients who did not comply with antiretroviral therapy had partial responses followed by relapses. CONCLUSIONS: Parotid cysts are an unrecognized sign of early HIV infection. These cysts respond to combination antiretroviral therapy, with or without corticosteroids. Surgical resection should be reserved for patients in whom medical therapy has failed or those who refuse or are poorly compliant with medical therapy.

Localization of tumor-associated glycoprotein DF3 in normal, inflammatory, and neoplastic lesions of the colon.

BACKGROUND: The expression of DF3 was assessed by a monoclonal antibody in normal, inflammatory, and neoplastic conditions in the large bowel. METHODS: Using immunohistochemistry, expression was examined in formalin-fixed paraffin-embedded biopsy and resection samples of 19 normal colonic mucosal specimens, 49 inflammatory lesions, 34 adenomas, and 38 primary colonic adenocarcinomas. In addition, Western blots of normal colonic mucosa and adenocarcinoma were examined. RESULTS: DF3 expression was detected in 84% of the adenocarcinomas with coarse membrane staining, intense positivity of luminal secretions, and focal cytoplasmic and intracytoplasmic vacuole staining. Nine of 32 areas of transitional mucosa revealed reactivity along apical membranes in crypt cells. Five adenomas containing carcinoma revealed DF3 positivity in the malignant areas only, whereas the remaining 29 were negative. Staining was membrane, luminal, and intracytoplasmic. Two examples of active ulcerative colitis revealed focal reactivity along the apical membrane of crypt cells. No other areas of staining were noted, including 12 cases containing dysplasia. Four of 10 other inflammatory lesions also revealed similar membrane reactivity in crypt cells. Normal colonic mucosa was nonreactive. Examples of normal colonic mucosa were negative for DF3 by Western blot analysis, whereas two carcinoma samples that reacted immunohistochemically were positive. CONCLUSIONS: DF3 is not detectable in normal colonic tissues. It is expressed focally and predominantly along the apical membrane of crypt cells in some inflammatory lesions and in the transitional mucosa of primary adenocarcinomas. Most adenocarcinomas of the colon and adenomas with foci of invasive carcinoma demonstrate reactivity in the cytoplasm and luminal secretions.

Intracytoplasmic inclusion bodies of erythrocyte origin within hepatocytes in a hepatic allograft.

Intracytoplasmic inclusion bodies with an unusual immunohistochemical profile, histologically similar to alpha 1 antitrypsin globules and megamitochondria, were seen within hepatocytes in a liver allograft biopsy. Electron microscopy revealed that these structures were erythrocytes in various stages of degradation. Their appearance following an episode of Pneumocystis carinii pneumonia suggests a possible relationship between bouts of hypoxia and erythrocyte entry into hepatocytes.

Monoclonal antibody SEN7 recognizes a new epitope on the neural cell adhesion molecule present on small cell lung cancer but not on lymphocytes.

In our continuing attempt to select monoclonal antibodies for immunotargeting of small cell lung carcinoma (SCLC) we have developed the IgG1 murine antibody SEN7 which by immunofluorescence stained all SCLC cell lines tested. On frozen tumor section six of seven SCLCs were positively stained. The reactivity of this antibody in a series of lung tumors and on normal tissues has some similarities with cluster 1 antibodies and cluster w4 antibodies, as defined by the First and Second International Workshop on Lung Cancer Antigens [P.C.L. Beverley, Y. Olabrian, J.A. Ledermann, L.G. Bobrow, and R.L. Souhami, Br. J. Cancer, 63 (Suppl): 10-19, 1991], particularly with regard to staining of neuroendocrine tissues. The similarities in staining of neuroendocrine tissues between antibody SEN7 and cluster 1 and cluster w4 antibodies prompted us to examine the binding of SEN7 with transfectants expressing the respective antigens. On the murine lymphoma cells B-9, stably transfected with a complementary DNA clone coding for an M(r) 140,000 isoform of human SCLC neural cell adhesion molecule (NCAM), antibody SEN7 reacted positively whereas the cluster w4 antibody was negative. The reaction of antibody SEN7 with the NCAM transfected murine lymphoma cells was unexpected in view of its lack of binding to peripheral blood mononuclear cells which regularly stain positive with NCAM antibodies. Western blotting of a renatured SCLC extract revealed a strong band around M(r) 180,000 in contrast to other cluster 1 antibodies which recognized a broad polydisperse band with a molecular weight of 140,000 to 210,000. Antibody binding was sensitive to tunicamycin treatment, suggesting the epitope to reside on an N-linked carbohydrate structure. No significant competition for SEN7 binding on SCLC cells was seen with other NCAM antibodies against the three distinct epitopes described on SCLC. This finding together with the lack of staining of peripheral blood mononuclear cells and the selected reactivity with the M(r) 180,000 band of NCAM indicate the antibody SEN7 recognizes an epitope on NCAM which has not been described previously. Biodistribution studies with radiolabeled SEN7 in nude mice bearing s.c. SCLC xenografts demonstrated the selective localization of more than 30% of the total injected dose per g tissue at day 4 following i.v. injection. The homogeneous binding to SCLC, the lack of binding to peripheral blood mononuclear cells, and the favorable tumor localization in a xenograft model indicates that SEN7 is a good antibody for immunotargeting of SCLC.

Carcinoembryonic antigen: enhancement of liver colonisation through retention of human colorectal carcinoma cells.

Carcinoembryonic antigen (CEA) is an oncofetal antigen whose function in the progression of colorectal carcinoma remains unclear although recent studies suggest it participates in homotypic cellular adhesion. We have previously shown that 40 micrograms of CEA injected intravenously into athymic nude mice enhances experimental metastasis in liver and lung by two human colorectal carcinoma cell lines that are injected intrasplenically 30 min later. The metastatic potential of another three moderately to highly metastatic colorectal carcinoma cell lines and of one weakly metastatic line has now been analysed in this model. CEA pretreatment only enhanced colony formation by cell lines that were weakly metastatic in untreated nude mice; it did not affect experimental metastasis by highly metastatic lines. CEA pretreatment enhanced the retention of 125I Idudr-labelled weakly metastatic tumour cells within the liver and lungs 4 h after intrasplenic injection but not the retention of highly metastatic tumour cells or inert latex beads. A significant correlation existed between the formation of experimental metastases and the early retention of tumour cells within the liver after intrasplenic injection. Aggregation did not appear to be important for retention in liver because CEA did not aggregate colorectal carcinoma cells in vitro. Also CEA did not alter natural host effector cell function in a cytolysis assay in vitro. We suggest that CEA facilitates liver colonisation by three of eight human colorectal carcinomas in athymic nude mice by increasing the hepatic retention of tumour cells. The potential mechanisms by which CEA may increase the retention of tumour cells in the liver are discussed.

Sucrase-isomaltase expression in chronic ulcerative colitis and dysplasia.

Sucrase-isomaltase (SI) is a mucosal disaccharidase that is present in normal small intestine and fetal colon. It also has been noted in colonic adenomas and adenocarcinomas. We used a polyclonal antibody to human SI to investigate enzyme presence and utility in detecting dysplastic changes in chronic ulcerative colitis. Sections from 32 cases were reviewed for the presence or absence of active colitis and dysplasia. Immunostaining of these cases for SI was performed and the results were reported based on location of immunoreactivity (ie, membrane and cytoplasmic staining in superficial and crypt epithelial cells) and percentage of positivity. Of 81 sections examined, 48 were rated negative for dysplasia (23 inactive colitis, 20 active, and five probably negative) and 28 were rated positive (eight low grade and 20 high grade). Surface membrane staining of epithelial cells was noted in all 28 dysplastic slides and positive cases (sensitivity, 100%) but also in 29 of 48 negative sections (P less than .001). In contrast, cytoplasmic positivity was present in 25 of 28 dysplastic and in only two of 48 negative slides (P less than .0001). The presence of cytoplasmic staining of SI in the superficial or crypt cells revealed a sensitivity of 92% and a specificity of 94%. There were five additional sections rated as indefinite for dysplasia (probably positive or unknown); two showed staining patterns typical of negative slides and three showed positive staining patterns. Of the 18 samples of transitional mucosa next to areas of dysplasia, surface membrane staining of SI was seen in all samples and cytoplasmic staining was seen in 15. We conclude that membrane staining of SI can be detected in inflammatory, regenerative, and dysplastic mucosa in ulcerative colitis. Cytoplasmic staining, however, correlates strongly with the presence of dysplastic change and may help in its detection.

Malignant epithelial cells in primary human lung carcinomas coexpress in vivo platelet-derived growth factor (PDGF) and PDGF receptor mRNAs and their protein products.

Lung cancer represents one of the major human carcinomas with the highest degree of mortality. Epidemiologic studies have linked this disease to "chronic injury," largely induced by cigarette smoking. In the present studies, we demonstrate the in vivo expression of platelet-derived growth factor (PDGF) and PDGF receptor (PDGF-R) beta mRNAs and their respective protein products in malignant epithelial cells of primary human lung carcinomas. In contrast, nonmalignant epithelial cells in control, normal lung tissue specimen did not express PDGF and PDGF-R mRNAs and did not produce their respective protein products. Epithelial cells in lung specimen from patients with idiopathic pulmonary fibrosis expressed only PDGF mRNA but not PDGF-R beta mRNA. These findings of the inappropriate coexpression of a potent mitogen, PDGF, and its receptor in lung cancer epithelial cells suggest the presence of a powerful in vivo mechanism contributing to the self-stimulation and unregulated growth of lung cancer tumor cells.

Spindle cell pseudotumor due to Mycobacterium avium-intracellulare in patients with acquired immunodeficiency syndrome (AIDS). Positive staining of mycobacteria for cytoskeleton filaments.

A rare spindle-cell pseudotumor caused by Mycobacterium avium-intracellulare (MAI) that mimics a mesenchymal tumor, was recently reported (7,14). We report on three such pseudotumors in patients with the acquired immunodeficiency syndrome (AIDS), two involving lymph nodes and one involving the bone marrow. In the course of investigating the first-encountered example of this tumor for evidence of smooth-muscle origin of the spindle cells, it was noted that these cells stained positively for desmin by immunoperoxidase techniques (IPX), as did a variety of other cytoskeleton filaments of all sizes. Electron microscopic examination of one of these lesions revealed spindle cells containing lysosomes and large numbers of microorganisms compatible with MAI but no filaments or organelles suggestive of smooth-muscle cells. Further studies revealed that the typical lesions produced by MAI in patients with AIDS, namely aggregates of histiocytes or individual histiocytes laden with organisms, rather than the expansile spindle-cell pseudotumor, also strain strongly for cytoskeleton filaments, as do M. tuberculosis and Mycobacterium leprae. Awareness of the existence of this unusual manifestation of MAI infection in AIDS patients and its desmin positivity can avoid misdiagnosis of a primary or metastatic smooth-muscle neoplasm. The cell of origin appears to be the histiocyte.

Monoclonal antibodies defining the cluster-5A small cell lung carcinoma antigen.

The cluster-5A antigen on small cell lung cancer has been previously identified by the murine IgG2a monoclonal antibody SWA20. We now describe four new murine monoclonal antibodies. SEN3 (IgG1), SEN11 (IgG3), SEN12 (IgG2b) and SEN31 (IgG1) which recognise the same antigen. The antibodies have similar binding characteristics as antibody SWA20 on cell lines and on a limited number of frozen sections of human tissues when examined by immunofluorescence and immunohistochemistry. Radioimmunoassays on fixed cells showed competitive binding of all antibodies with radiolabelled antibody SWA20. Solid phase radioimmunoassays with the new antibodies on biochemically treated target cells showed similar characteristics to antibody SWA20, including sensitivity to treatment with periodate and neuraminidase. Immunoblotting experiments with all antibodies revealed similar bands at molecular weights of 180, 100 and 50 kD. Binding studies after incubation of cells with inhibitors of glycoprotein synthesis suggest the cluster-5A antigen to be a N-linked sialoglycoprotein.

Expression of enzymatically active sucrase-isomaltase is a ubiquitous property of colon adenocarcinomas.

Adenocarcinoma of the colon is one of the most prevalent and lethal of all human malignancies. The early diagnosis and management of this disease could be improved if biological markers, whose expression was restricted to malignant colon cells, were identified. Sucrase-isomaltase is a glycoprotein hydrolase expressed throughout the small intestine and fetal colon but not in the normal adult colon. This study shows that the expression of enzymatically active sucrase-isomaltase is a ubiquitous property of primary and metastatic colon adenocarcinoma. Significant sucrase enzyme activity (i.e., greater than 5 mU/mg protein) was observed in 16 colon carcinomas but not in adjacent normal colon mucosa. Sucrase-isomaltase messenger RNA was identified in all tumors using reverse transcriptase polymerase chain reaction. Using a quantitative polymerase chain reaction analysis, this study shows that the amount of sucrase-isomaltase messenger RNA in tumors examined (3.4 x 10(-8) to 3.19 x 10(-7) micrograms/micrograms total RNA) was greater than in adjacent mucosa (0 to 3.4 x 10(-8) micrograms/micrograms total RNA). This induction of sucrase-isomaltase messenger RNA and enzyme activity was corroborated by immunostaining. Of 30 colon adenocarcinomas examined, 80% were positive for sucrase-isomaltase. In addition, all colon carcinoma metastases examined were positive for sucrase-isomaltase. The staining pattern was distinct and demarcated tumor cells from the surrounding histologically normal tissue. No sucrase-isomaltase staining was seen in normal mucosa from the same patients. With the exception of lung, no sucrase-isomaltase immunostaining was observed in a variety of examined noncolonic adenocarcinomas. Thus, the specificity and ubiquity of sucrase-isomaltase expression in adenocarcinomas of the colon can be exploited to improve the clinical management of this disease. In addition, studies on the structure of the sucrase-isomaltase gene and its regulatory elements should contribute toward understanding the alteration of gene expression by oncogenic transformation of the colonic mucosa.

Surgical resection of a solitary liver metastasis in a 46-year-old patient with a malignant thymoma.

Clinical history, surgical treatment, and pathologic findings of a solitary liver metastasis of a malignant thymoma in a 46-year-old female are reported. An extensive literature review has revealed no record of surgical resection of liver metastasis in a patient with invasive thymoma.

Infiltration of the lower respiratory tract by helper/inducer T lymphocytes in HTLV-1-associated adult T-cell leukemia/lymphoma.

The human T-cell lymphotropic virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia/lymphoma (ATLL), a disorder in which peripheral blood and multiple organs are infiltrated by malignantly transformed T lymphocytes. We investigated the nature of pulmonary disease in a patient with serologic evidence of HTLV-1 infection. In this case, endobronchial biopsy specimens showed infiltration of the bronchial mucosa by pleomorphic cells exhibiting a high degree of nuclear irregularity. These cells were morphologically identical in appearance to malignant cells found in peripheral blood and infiltrating the dermis, expressed the OKT4/Leu3 phenotype and the receptor for interleukin 2, and, by analogy to gene rearrangement studies on leukemic blood cells, were monoclonal in origin. However, in situ hybridization of endobronchial biopsy specimens with full-length HTLV-1 probes failed to detect retroviral RNA or proviral DNA. These studies indicate that T lymphocytic involvement of the lower respiratory tract in HTLV-1-associated ATLL is characterized by expression of a malignant phenotype despite the inability to document actual cellular infection with this retrovirus by a molecular hybridization technique.

Sucrase-isomaltase: a marker associated with the progression of adenomatous polyps to adenocarcinomas.

Adenocarcinomas of the colon arise from adenomatous polyps. We hypothesized that sucrase-isomaltase (SI), a glycoprotein hydrolase, found in normal small intestine, fetal colon, and colon carcinomas is a marker associated with progression of adenomatous polyps with dysplasia to adenocarcinomas. To examine this hypothesis, we performed immunostaining using a polyclonal antihuman SI antibody in 32 adenomatous polyps with varying degrees of dysplasia. In addition, sucrase enzyme activity was determined in three sets of simultaneously harvested polyps, cancer, and adjacent normal mucosa from the same patient. All severely dysplastic polyps (6/6) exhibited SI staining. Most polyps (85%) with 3+ staining (i.e., greater than 10% of polyp positive for SI) had severe dysplasia, whereas those with mild dysplasia had either 1% to 5% staining or no staining in 95% of the cases. These data indicate that the extent of SI immunostaining in polyps correlates with the degree of dysplasia (p = 0.0001). Sucrase-isomaltase activity in the polyps was 18.1 +/- 1.8 mU/mg (mean +/- SD); in adjacent carcinoma SI activity was 29.1 +/- 1.8 mU/mg. Adjacent mucosa showed no activity in all cases. In summary, our results suggest that SI expression correlates with the progression of dysplastic adenomatous polyps to carcinoma. Sucrase-isomaltase expression may be useful as a clinical marker to improve our prognostic capabilities in patients with dysplastic lesions of the colon, that is, inflammatory bowel disease.

ME1. A monoclonal antibody that distinguishes epithelial-type malignant mesothelioma from pulmonary adenocarcinoma and extrapulmonary malignancies.

ME1 is a monoclonal antibody reactive in frozen tissue sections with normal mesothelial cells and malignant mesotheliomas. In this immunoperoxidase study, ME1 reacted with all 40 epithelial type malignant mesotheliomas. Fifty percent or more of the mesothelioma cells were stained in all cases and the staining intensity was strong in 32 and moderate in eight. In contrast, all 19 well- and moderately differentiated pulmonary adenocarcinomas were completely negative, and of the total 88 non-mesotheliomatous malignancies studied, staining comparable to the mesotheliomas was seen in only 6 tumors (2 pulmonary adenocarcinomas, 2 adenocarcinomas of the breast, 1 adenocarcinoma of the pancreas, and 1 melanoma), although limited, weaker staining was seen in additional cases. Five of the six strongly to moderately positive nonmesotheliomatous tumors had immunoreactivity for complementary immunoreactants (CEA, Leu-M1, S-100 protein, HMB-45). Our results with ME1, the first monoclonal antibody that recognizes malignant mesothelial cells, provides a basis for using this reagent in the differential diagnosis of tumors of the pleura and peritoneum.

Peripheral/post-thymic T-cell lymphomas: a spectrum of disease. Clinical, pathologic, and immunologic features of 78 cases.

The clinical, pathologic, and immunologic features of 78 cases of peripheral/post-thymic T-cell lymphomas are described. These neoplasms were extremely heterogeneous and were classified as small lymphocytic, mixed small and large cell, large cell, lymphoepithelioid cell, angiocentric, and adult T-cell leukemia/lymphoma type. Some cases revealed angioimmunoblastic or Hodgkin's-like features. These neoplasms mainly affected older adults (mean age, 57 years; median age, 60 years). Lymphadenopathy represented the most frequent clinical presentation, although most patients demonstrated both nodal (87%) and extranodal involvement (77%) during the course of disease. Sites of extranodal disease included skin/soft tissue, spleen, lung, liver, bone, gastrointestinal tract, central nervous system, peripheral blood, nasopharynx, and retrovaginal tissue. Splenomegaly at presentation was most frequently observed in lymphoepithelioid cell lymphomas. Angiocentric lymphomas involved lung. A mediastinal presentation was typically observed in young adults and associated with a poor prognosis. Patients with gastrointestinal lymphomas presented with bleeding and/or malabsorption. B symptoms were present in most cases (65%). Hypercalcemia occurred in four patients. Phenotypic studies of T-cell antigens demonstrated the loss of one or more pan-T-cell markers in eight of 47 cases evaluated. Assessment of T-cell subsets revealed a helper/inducer phenotype for nearly all immunoreactive cases. For the overall series, 32 patients died of disease (median survival time, 11.5 mo). There was a statistical difference between the combined groups of small lymphocytic and lymphoepithelioid cell types as compared with mixed and large cell types, with a poorer survival for the latter group. Angiocentric and adult T-cell leukemia/lymphoma were associated with poor survival. This series of T-cell lymphomas further documents the marked heterogeneity of this group of neoplasms as well as the poor prognosis observed for certain histologic types.

Tumor-associated membrane sialoglycoprotein on human small cell lung carcinoma identified by the IgG2a monoclonal antibody SWA20.

A mouse IgG2a monoclonal antibody, SWA20, defining a tumor-associated cell surface antigen on small cell carcinoma of the lung (SCC) was generated. The reactivity of the antibody with cell lines was examined by indirect immunofluorescence staining and solid phase radioimmunoassay and the reactivity with tissues by immunoperoxidase staining. The antibody reacts with a proportion of small cell carcinoma cell lines (4 of 8) and tissues (7 of 12), but not with other pulmonary or extrapulmonary cell lines (0 of 30) or tumor tissues (0 of 78). The antibody was unreactive with primary cultures of normal bronchial epithelial cells, RBC, and WBC. Immunoperoxidase staining of normal tissues showed rare antigen-positive cells in suprabasal layers of bronchial epithelium and less than 10% of positive cells in colon epithelium. Immunoblots of SCC extracts demonstrated antibody reactivity with a doublet band at Mr 40,000, a broader band at Mr 100,000, and a band at Mr 180,000. The antigen was not present in crude lipid extracts of SCC cells. Solid phase radioimmunoassays and immunoblots showed binding competition with the lectin Triticum vulgaris, sensitivity of the antigen to neuraminidase, and a partial sensitivity to treatment with periodate. The antigen was coexpressed on SCC cell lines with the antigen sGP90-135 defined first by antibody LAM8 (R. Waibel, C. J. O'Hara, and R. A. Stahel. Cancer Res., 47:3766-3770, 1987) but differed from it by lack of reactivity with Lea-positive saliva and partial resistance to periodate treatment. There was no binding competition between radiolabeled antibodies SWA20 and LAM8 to SCC target cells. The IgG2a antibody SWA20 identifies a previously undescribed tumor-associated surface membrane antigen, sGP100, expressed selectively on a proportion of SCC.

The ultrastructural and immunohistochemical demonstration of viral particles in lymph nodes from human immunodeficiency virus-related and non-human immunodeficiency virus-related lymphadenopathy syndromes.

Viral particles have been demonstrated by electron microscopy in lymph nodes from patients with acquired immune deficiency syndrome AIDS-related persistent generalized lymphadenopathy (PGL) syndrome. Immunohistochemical and in situ hybridization studies have identified these viruses as the human immunodeficiency virus (HIV). In this study, we examined 20 PGL lymph nodes and found viral particles in 18 cases. Immunohistochemical studies on these cases revealed positive staining for the HIV core protein P24 within germinal centers of secondary follicles. In addition we found viral particles, morphologically indistinguishable from those observed in PGL lymph nodes, in 13 of 15 non-HIV related reactive lymph nodes. Immunohistochemical staining of these lymph nodes for the P24 core protein was negative. None of the patients in this group had risk factors for developing AIDS and none exhibited clinical evidence of immune deficiency. We conclude that the viral particles observed in PGL lymph nodes are most likely HIV, but similar particles can be seen in reactive lymph nodes not associated with HIV infection. The discrete localization of these particles within germinal centers has been observed for other viruses and immune complexes and a possible mechanism of this antigen deposition is discussed.

Monoclonal antibodies against mesothelial membrane antigen discriminate between malignant mesothelioma and lung adenocarcinoma.

Monoclonal antibodies (MAbs) were generated by immunizing mice with the mesothelioma cell line SPC111 and selected by indirect immunofluorescence on viable cells. Indirect immunofluorescence staining and radioimmunoassays demonstrated selective binding of the antibodies ME1 and ME2 with the surface membrane of mesothelioma, but not with lung adenocarcinoma cell lines. Lung small-cell carcinoma cell lines were unreactive, while staining was seen in a proportion of lung squamous-cell carcinoma cell lines. The antibodies were unreactive with other cell lines, including breast, colon, ovarian, and renal-cell carcinoma, leukemia, and lung fibroblast. The antibodies stained normal mesothelial cells, but were unreactive with normal bronchial epithelial cells in primary cultures, or peripheral blood cells. Immunohistochemical staining of cryostat sections of tumor tissues confirmed the ability of the antibodies to distinguish between mesothelioma and lung adenocarcinoma. All 12 mesothelioma tissues, but none of 9 lung adenocarcinomas or large-cell carcinomas, stained with the MAbs. Staining of malignant mesothelioma tissues was very homogeneous. Some lung squamous-cell carcinomas and breast carcinomas were stained focally by both, and some ovarian carcinomas by one antibody. Solid-phase radioimmunoassays demonstrated antigen sensitivity to chymotrypsin digestion and binding competition between the antibodies. The antibodies ME1 and ME2 identify a surface membrane antigen with preferential expression on normal and malignant mesothelial cells. They distinguish malignant mesothelioma from lung adenocarcinoma on cryostat sections and promise to be useful tools in biological studies of mesothelial cells.