Inverse correlation of cell proliferation and expression of progesterone receptors in tumor spheroids and monolayer cultures of human meningiomas

OBJECTIVE

The progesterone receptor (PgR) can be detected in 60 to 70% of meningiomas using immunohistochemistry] in situ. Whereas in monolayer tissue cultures the PgR is only rarely expressed, we were able recently to demonstrate the preservation of the PgR in fragment spheroid cultures of meningiomas. The aim of the present study was to evaluate the stability of PgR expression in meningioma spheroids in vitro and the correlation of PgR expression and cell proliferation in spheroids and whether meningioma cells reaggregated to spheroids from monolayer cultures to reexpress the PgR again.

METHODS

Tumor fragment spheroids (Weeks 1-6) and cell monolayers (Passages 1 and 3) of 15 PgR-positive meningiomas were investigated by immunohistochemistry for the expression of PgRs and their proliferative activity, as demonstrated by positivity for the proliferation-related antigen Ki-67. To study PgR reexpression in reaggregated spheroids, Northern blots were performed. In addition, a reverse transcriptase-polymerase chain reaction technique was established and evaluated in combination with immunohistochemistry. Growth of meningioma spheroids was quantified in the presence of progesterone and the specific antagonist onapristone.

RESULTS

The PgR remained stable in spheroids for 6 weeks in 9 of 13 cases that were able to be evaluated. All tumor fragment spheroids exhibited a proliferation index of 5 to 40% Ki-67-positive cells. Monolayer cell cultures, on the other hand, failed to express PgRs but revealed higher proliferation indices (40-90%) to a significant extent. The detection of PgR messenger ribonucleic acid in reaggregated spheroids by means of reverse transcriptase-polymerase chain reaction correlated to the nuclear expression of PgR in immunohistochemistry. Neither progesterone nor its antagonist onapristone altered spheroid growth in vitro.

CONCLUSION

The expression of the PgR in meningiomas is preserved in spheroid cultures with low proliferation indices for at least 6 weeks, whereas monolayer cell cultures with a high proliferative activity lack PgR expression. The inverse pattern of Ki-67-positive cells in the outer regions of the spheroids and PgR-expressing tumor cells in the spheroid centers leads us to the conclusion that proliferating meningioma tumor cells do not express PgRs. This might also explain why tumor cell growth in vitro was neither affected by progesterone nor by onapristone. Monolayer cell cultures can be reaggregated to spheroids, the consequence being a reexpression of PgRs and, therefore, a down-regulation of proliferation.

Cyclin D1 expression in mantle cell lymphoma is accompanied by downregulation of cyclin D3 and is not related to the proliferative activity

The cell cycle regulatory protein cyclin D1 is essential for G1-S phase transition in several epithelial and mesenchymal tissues but is apparently not essential in normal mature B cells. An overexpression of cyclin D1 is induced by the chromosomal translocation t(11;14)(q13;q32), which characterizes non-Hodgkin's lymphomas (NHLs) of mantle cell type. We studied 26 cases of mantle cell lymphoma (MCL) for the expression of cyclins D1 and D3. A total of 23 lymphomas showed a nuclear staining for cyclin D1, whereas reactive B cells of residual germinal centers were constantly negative. When compared with cyclin D3, an inverse staining pattern emerged. Whereas the B cells of residual germinal centers reacted strongly positive for cyclin D3, there was low or missing expression of cyclin D3 in MCL cells. In other B-cell lymphomas (n = 55), including chronic lymphocytic leukemia, low-grade lymphomas of mucosa-associated lymphatic tissue, follicular lymphomas, and diffuse large B-cell lymphomas, no cyclin D1 expression could be detected and 89% of these cases displayed cyclin D3 positivity. Lymphoma cell lines harboring the t(11;14) showed cyclin D1 protein but no or very low levels of cyclin D3; three other B-cell lines, a T-cell line, and peripheral blood lymphocytes strongly expressed cyclin D3 and reacted negatively for cyclin D1. We conclude that the chromosomal translocation t(11;14) leads to an abnormal protein expression of cyclin D1 in the tumor cells of MCL and induces a consecutive downregulation of cyclin D3. In contrast to other B-NHLs, cyclin D1 and D3 expression in MCL is not related to the growth fraction.

Alterations of the cyclin D1/p16-pRB pathway in mantle cell lymphoma

Mantle cell lymphoma (MCL) has recently become generally accepted as a subentity of malignant lymphomas that is characterized by the chromosomal translocation t(11;14)(q13;q32), resulting in the overexpression of cyclin D1. Cyclin D1 forms a complex with cell cycle-dependent kinase (cdk) 4, which inactivates the retinoblastoma protein (pRB) via phosphorylation. However, in transgenic mice, the overexpression of cyclin D1 alone is not sufficient for the development of malignant lymphoma. To determine whether other members of the pRB pathway contribute to the malignant transformation of MCL, we analyzed 37 cases of MCL that were well characterized by morphology, immunophenotype, and/or interphase cytogenetics [detection of t(11;14)(q13;q32)]. Interphase fluorescence in situ hybridization was performed using a cosmid contig (250 kb) of the CDKN2/p16 region (encoding an inhibitor of the cyclin D1/cdk4 complex) and a phage contig (200 kb) of the Rb region. CDKN2/p16 deletion was detected in 15 cases (41%), including 6 homozygous deletions; Rb was deleted in 15 cases (41%), all of which were hemizygous deletions. Nine cases (24%) had deletions of both CDKN2/p16 and Rb. Further analysis of a subset of 17 MCLs revealed a highly significant correlation between CDKN2/p16 deletion and proliferation index, determined by the rate of Ki67 expression (P = 0.014; t test). No significant correlation was found between CDKN2/p16 deletion and the blastoid variant of MCL (P = 0.23; Fisher's test) or between proliferation index and blastoid morphology (P = 0.51; t test). Deletion of Rb did not have any impact on cell proliferation in addition to CDKN2/p16 deletion (P = 0.76; t test). Additional analysis of 13q14 deletions suggests that these deletions may target another gene telomeric to Rb. We conclude that deletion of CDKN2/p16 occurs in approximately one-half of MCLs and is a more relevant indicator of the proliferative features as compared to morphological criteria. In contrast, although deletions of chromosomal band 13q14 are frequent in MCL, inactivation of Rb seems not to be involved in the pathogenesis of MCL.

p53 protein in endometrial cancer is related to proliferative activity and prognosis but not to expression of p21 protein

Expression of the tumor suppressor gene product p53 and the cyclin-dependent kinase inhibitor p21, which is transcriptionally activated by p53, was investigated and compared with patient survival in a retrospective longitudinal study of 202 cases of endometrial carcinoma. The median duration of follow-up was 4.3 years. P53 was observed immunohistochemically in 63 (31%) of the tumors and was found by univariate analysis to be related to reduced adjusted survival (p = 0.00028) and disease-free survival (p = 0.04). However, p53 expression was not found by multivariate analysis to be an independent prognostic factor when compared with FIGO stage, histologic grade, and proliferative activity, as determined by immunoreactivity for topoisomerase IIalpha with the antibody Ki-S1. Overexpression of p53 was related to histologic grade (p < 0.00001), proliferative activity (p = 0.0071), and inversely to progesterone receptor content (p = 0.042). Immunohistochemical identification of p21 was investigated in 95 cases and found to be positive in 19 (39%) of 49 tumors with p53 overexpression and in 13 (28%) of 46 tumors without p53 overexpression (p = 0.28). Expression of p21 is therefore not related to p53 expression, nor was it found to be related to proliferative activity. Strong expression of p21 was observed in tumors negative for progesterone receptors (p = 0.0028). P53 in endometrial carcinoma is not associated with induction of the cell cycle inhibitor p21, but is associated with an enhanced proliferative activity. The findings of multivariate analysis suggest that the prognostic significance of p53 is related mainly to cell proliferation.

The t(11;18)(q21;q21) chromosome translocation is a frequent and specific aberration in low-grade but not high-grade malignant non-Hodgkin's lymphomas of the mucosa-associated lymphoid tissue (MALT-) type

Primary extranodal malignant non-Hodgkin's lymphoma arising from the mucosa-associated lymphoid tissue (MALT-type lymphoma) represents a subtype of B-cell lymphoid malignancies with distinct clinicopathological features and is often associated with a favorable prognosis. Unlike the situation in nodal non-Hodgkin's lymphoma of B-cell lineage, few data are still available concerning the chromosomal constitution of MALT-type lymphomas. Until now, cytogenetic data from 29 low-grade MALT lymphomas with karyotypic alterations have been reported from different institutions, and virtually no data were available for high-grade MALT-type lymphomas. We have analyzed the cytogenetics of 44 MALT lymphomas arising in the stomach, parotid gland, thyroid gland, lung, breast, and conjunctiva. Clonal chromosome aberrations have been detected in 13 of 20 (65%) low-grade and 20 of 24 (83%) high-grade tumors. More than half of the low-grade lymphomas with abnormal karyotypes (7 of 13 cases, 53%) displayed clonal t(11;18)(q21;q21), thus specifically associating this translocation with MALT-type lymphomas for the first time in a larger series. In contrast, t(11;18) was not found in a single case of 20 high-grade MALT-type lymphomas with abnormal karyotypes, nor were translocations t(14;18) or t(3;14), characterizing about 10-35% of primary nodal large cell lymphomas. Instead, these lymphomas were associated with t(8;14)(q24;q32) in three cases, frequent deletions in the long arm of chromosome 6, and partial or whole gains of chromosomes 3, 7, 17, 18, and 21.

Active fulminant myocarditis characterized by T-lymphocytes expressing the gamma-delta T-cell receptor: a new disease entity?

Lymphocytic myocarditis is thought to be a virus-induced disease. T cells expressing the alpha-beta T-cell receptor seem to play a central role in the pathogenesis and to mediate tissue injury in this disease. A case of active fulminant myocarditis is described, which was analyzed by immunohistochemical, molecular biologic, and serologic methods. Infiltration of the heart tissue predominantly by gamma-delta T cells was detected by immunohistochemistry. No evidence of viral disease could be obtained by in situ hybridization with different enterovirus-specific DNA probes; by reverse-transcriptase polymerase chain reaction using specific primers for enteroviruses, adenoviruses, herpes simplex viruses, influenza A and B viruses, and cytomegaloviruses; or by enzyme-linked immunosorbent assay and electron microscopy. Because gamma-delta T cells may have an autoimmune capacity, we propose that these cells may trigger autoimmune myocarditis. These findings may be important in order to identify subgroups of patients who may benefit from immunosuppressive therapy.

Susceptibility to the development of pigment cell tumors in a clone of the Amazon molly, Poecilia formosa, introduced through a microchromosome

The Amazon molly Poecilia formosa is a gynogenetic fish that reproduces through the development of ameiotic diploid eggs triggered by insemination by males of related species without following karyogamie. This leads to clonal offspring. In rare cases, however, this gynogenesis is leaky, and paternal DNA in the form of small supernumerary chromosomes is included into the maternal genome. We have obtained a clone where one such microchromosome contains a pigmentary locus, resulting in macromelanophore pigmentation of the carrier. Approximately 5% of these fish spontaneously develop exophytic nodular or papillomatous pigment cell tumors. The tumors display considerable differences with respect to growth characteristics and invasiveness, despite the genetic uniformity of the affected animals. Following transplantation to syngeneic hosts, a remarkable clonal variability was observed. Oncogenes that are involved in tumorigenesis in hereditary melanoma of the closely related fish Xiphophorus appear not to be instrumental for induction of the P. formosa pigment cell tumors. Moreover, a new genetic locus is defined that mediates susceptibility to pigment cell tumor development and leads to transformation of chromatoblasts.

The Epstein-Barr virus in malignant non-Hodgkin's lymphoma of the upper aerodigestive tract

Sixty malignant non-Hodgkin's lymphomas originating in the upper aerodigestive tract have been analyzed for their cytologic type, immunophenotype and association with the Epstein-Barr virus (EBV). The majority of these tumors were B-cell lymphomas of blastic cytology (78%) with the exception of lymphomas in the parotid gland. Large B-cell lymphomas were the most frequent encountered in the sinonasal region and Waldeyer's ring. Twelve lymphomas were of T- or T/NK (natural killer)-cell lineage. They were in the nasal cavity and the paranasal sinuses (4), the tonsil (5), and the oral cavity (3). Epstein-Barr sequences were detected in five angiocentric T/NK-lymphomas, one peripheral T-cell lymphoma, one lymphoma of lymphomatoid granulomatosis type, one large B-cell lymphoma, and in a lymphoroliferative disorder in an HIV-positive patient. These results suggest that EBV is not involved in lymphomagenesis of B-cell tumors, but is associated with angiocentric T/NK-cell lymphoma in the upper aerodigestive tract.

Low-grade B cell lymphomas of mucosa-associated lymphoid tissue (MALT-type) require CD40-mediated signaling and Th2-type cytokines for in vitro growth and differentiation

To investigate the mechanisms of T cell dependence underlying the development of extranodal mucosa-associated lymphoid tissue (MALT)-type B cell lymphomas, the activation, proliferation, and differentiation of lymphoma B cells were studied using ligand binding to the CD40 membrane receptor. The activation and proliferative response of all investigated low-grade MALT-type lymphomas (n = 6) was strongly dependent on anti-CD40-mediated signals and was complemented by cytokines produced by T helper cells of the Th2 type (interleukin-4 (IL-4) and/or IL-10). Th1 cytokines (IL-2 and/or interferon-gamma) bad little effect. Low-grade, but less so high-grade, MALT-type lymphoma B cells were induced to secrete large amounts of tumor immunoglobulin in response to IL-10. In contrast, high-grade MALT-type lymphomas (n = 5) proliferated in response to both Th2- and Th1-type cytokines and CD40 stimulation, whereas Burkitt lymphomas (n = 3) could not be rescued from apoptosis by CD40 stimulation with or without cytokines. These results suggest that CD40 signaling in combination with Th2 cytokines are essential for the development and progression of low-grade MALT-type B cell lymphoma. We conclude that T cells, which activate B cells in a CD40-dependent fashion, may contribute to lymphoma pathogenesis.

MALT-type lymphoma of the stomach is associated with Helicobacter pylori strains expressing the CagA protein

BACKGROUND & AIMS

Helicobacter pylori is considered to be involved in the pathogenesis of gastric lymphoma of mucosa-associated lymphoid tissue (MALT) type. Strains expressing the CagA protein (CagA+ strains) have been strongly associated with severe gastritis, duodenal ulceration, and gastric adenocarcinoma. The aim of this study was to determine the presence of H. pylori as well as incidence of CagA+ strains in gastric MALT-type lymphoma.

METHODS

Sera of 68 patients with gastric MALT-type lymphoma (22 with low grade, 36 with high grade, and 10 with secondary high grade) were obtained, and the serological response to CagA was studied by immunoblotting using a purified recombinant CagA protein, a CagA+ strain, and the corresponding isogenic CagA- mutant.

RESULTS

Of the patients with MALT-type lymphoma, 98.5% (67 of 68 patients) were H. pylori seropositive. In the only seronegative patient, the bacterium was detected histologically by Warthin-Starry staining. Of the seropositive patients, 95.5% had serum immunoglobulin G antibodies to CagA compared with 67% of an H. pylori-positive control group (33 of 49 patients; P = 0.000037) with chronic active gastritis.

CONCLUSIONS

These results indicate infection of almost all patients with MALT-type lymphoma by CagA+ H. pylori strains. Strains expressing the CagA protein seem to play a crucial role in the pathogenesis of gastric MALT-type lymphoma.

Pathogenesis of myasthenia gravis

Various studies over the last 25 years in Man and animal models have revealed many steps in the pathogenesis of myasthenia gravis (MG) which is now considered the classical organ specific, autoantibody mediated and T cell dependent human autoimmune disease. Though not a disease entity, MG is associated with pathological alterations of the thymus in about 80% of cases. These are described here with reference to distinct models of autoimmunization against the acetylcholine receptor (AChR). In MG with thymitis, intrathymic production of AChR-specific autoantibodies is the result of a classical antigen-driven immune reaction that occurs completely inside the thymus and probably involves AChR on myoid cells as the triggering (myasthenogenic) antigen. Genetic factors contribute essentially to the pathogenesis of this form of MG. In thymoma-associated MG genetic factors are probably of marginal significance. Neither intratumour autoantibody production nor T cell activation seem to occur and the AChR is not the myasthenogenic antigen. Instead, abnormal neurofilaments that share epitopes with the AChR and other auto-antigen targets in paraneoplastic MG are expressed in thymomas and may trigger autoantigen-specific, non-tolerogenic T cell selection by molecular mimicry. These data support the hypothesis that initial steps in the pathogenesis of most MG cases take place within abnormal thymic microenvironments, be they inflammatory or neoplastic. Where these initial steps occur in MG cases without thymic pathology is not known. Likewise, the factors involved in the initial triggering of MG remain enigmatic in all MG subtypes.

Intraclonal offspring expansion of gastric low-grade MALT-type lymphoma: evidence for the role of antigen-driven high-affinity mutation in lymphomagenesis

Recent studies have shown that gastric mucosa-associated lymphoid tissue (MALT)-type lymphoma B cells are the malignant counterparts of hypermutated, postgerminal-center memory B cells. To further elucidate the role of antigen selection in the evolution of gastric low-grade MALT-type lymphoma, we analyzed intraclonal variations of the immunoglobulin heavy-chain variable region (Ig VH) genes expressed in three cases of lymphoma. The Ig VH genes expressed by tumor cells were amplified by PCR using primers for individual tumor-specific markers (complementarity-determining region 3 (CDR3)) and primers for six VH family leaders and then sequenced. The corresponding germ-line VH gene from these patients was also sequenced. The somatic mutations were highly concentrated in the CDR or framework region, with a clustering of replacement mutations in the CDR but only a few in the framework region. Each of the Ig VH genes of tumor cell clones of Cases 1 and 3 showed different mutations, whereas Case 2 showed no intraclonal variation. Although all three mutation pattern variants of Cases 1 and 3 occurred in postgerminal memory B cells, only one offspring from each case resulted in a dominant expansion. This finding suggests that antigen-driven high-affinity somatic mutation may play an important role in the expansion of intraclonal offspring from low-grade MALT-type lymphomas.

Differential expression of apoptosis receptors on diffuse and intestinal type stomach carcinoma

BACKGROUND

Intestinal and diffuse adenocarcinomas of the stomach differ in phenotypic properties, morphology, and growth behavior. Apoptosis (programmed cell death) is induced via specific cell-surface receptors (SC-1, Fas/APO-1/CD95) and coregulated by intracellular molecules (bcl-2, p53, etc.); the success of apoptotic processes is dependent on the expression of these signals. Differences in the expression of specific apoptosis receptors and intracellular-related signals might help to explain the molecular pathogenesis of these two types of stomach adenocarcinoma.

METHODS

Immunohistochemical studies were performed on frozen sections of tumor tissue using human monoclonal antibody SC-1 and murine monoclonal antibodies Fas and p53, followed by peroxidase-coupled second antibodies. To determine binding of SC-1 and Fas antibodies to stomach carcinoma cells on the molecular level, Western blot analysis was performed with cell extract preparations from stomach carcinoma cells. To investigate functional apoptotic activity, MTT assays were performed with SC-1 and Fas antibodies on stomach carcinoma cells.

RESULTS

On frozen sections intestinal type stomach carcinoma cells demonstrate little or no expression of SC-1 and Fas receptors (4 of 17 and 1 of 17, respectively). Diffuse type stomach carcinoma cells show just the opposite: greater than 50% express SC-1 and Fas at a high level (15 of 30 and 22 of 30, respectively). Normal stomach mucosa is negative with both antibodies. Expression of p53 is positively correlated with intestinal type carcinomas (11 of 17) but not with diffuse type (5 of 30). In functional studies MTT assay) the SC-1 and Fas antibodies react with stomach carcinoma by inducing apoptosis and inhibiting growth. On Western blot analysis of extracts from stomach carcinoma cells, SC-1 detects a protein of 50 kilodalton (kD) and Fas proteins of approximately 30, 45, and 60 kD.

CONCLUSIONS

These data indicate that gastric carcinoma cells of the intestinal and diffuse type differ in their expression of the apoptotic receptors SC-1 and Fas and the tumor suppressor gene product p53. These new data on phenotypic differences support the hypothesis that these two types of stomach carcinoma do not only differ in morphology, growth pattern, and risk factors but also in genetic pathways.

Differential expression of apoptosis receptors on diffuse and intestinal type stomach carcinoma

BACKGROUND

Intestinal and diffuse adenocarcinomas of the stomach differ in phenotypic properties, morphology, and growth behavior. Apoptosis (programmed cell death) is induced via specific cell-surface receptors (SC-1, Fas/APO-1/CD95) and coregulated by intracellular molecules (bcl-2, p53, etc.); the success of apoptotic processes is dependent on the expression of these signals. Differences in the expression of specific apoptosis receptors and intracellular-related signals might help to explain the molecular pathogenesis of these two types of stomach adenocarcinoma.

METHODS

Immunohistochemical studies were performed on frozen sections of tumor tissue using human monoclonal antibody SC-1 and murine monoclonal antibodies Fas and p53, followed by peroxidase-coupled second antibodies. To determine binding of SC-1 and Fas antibodies to stomach carcinoma cells on the molecular level, Western blot analysis was performed with cell extract preparations from stomach carcinoma cells. To investigate functional apoptotic activity, MTT assays were performed with SC-1 and Fas antibodies on stomach carcinoma cells.

RESULTS

On frozen sections intestinal type stomach carcinoma cells demonstrate little or no expression of SC-1 and Fas receptors (4 of 17 and 1 of 17, respectively). Diffuse type stomach carcinoma cells show just the opposite: greater than 50% express SC-1 and Fas at a high level (15 of 30 and 22 of 30, respectively). Normal stomach mucosa is negative with both antibodies. Expression of p53 is positively correlated with intestinal type carcinomas (11 of 17) but not with diffuse type (5 of 30). In functional studies MTT assay) the SC-1 and Fas antibodies react with stomach carcinoma by inducing apoptosis and inhibiting growth. On Western blot analysis of extracts from stomach carcinoma cells, SC-1 detects a protein of 50 kilodalton (kD) and Fas proteins of approximately 30, 45, and 60 kD.

CONCLUSIONS

These data indicate that gastric carcinoma cells of the intestinal and diffuse type differ in their expression of the apoptotic receptors SC-1 and Fas and the tumor suppressor gene product p53. These new data on phenotypic differences support the hypothesis that these two types of stomach carcinoma do not only differ in morphology, growth pattern, and risk factors but also in genetic pathways.

Characterization of the human thymic microenvironment: lymphoepithelial interaction in normal thymus and thymoma

Recent advances in tissue culture technology and molecular biology have extended our understanding of the functional morphology of the thymus. The importance of a crosstalk between lymphoid cells and stroma has been appreciated as a prerequisite for the normal development of both. The network of direct cellular interactions and soluble factors comprising part of the microenvironment is far from being elucidated but the highly ordered thymic architecture clearly plays a pivotal role in normal thymic function. Insight into the genetic control of stroma development is only emerging while knowledge on the genetic control of the various steps in T cell development is already advanced and rapidly expanding. The present paper gives an overview on the cellular components and matrix molecules of the human thymic microenvironment and their development during ontogeny. The intrathymic cytokine network is shortly reviewed. Special emphasis is put on molecules mediating lymphoepithelial interactions that are necessary for the expansion and early selection of immature thymocytes from precursor cells and for the generation of an MHC restricted and self tolerant T cell repertoire by positive and negative selection. Considering these physiological mechanisms we summarize the molecular pathology of the microenvironment and lymphocyte/stroma interactions in thymic epithelial tumors (thymomas). Finally, a pathogenetic model for paraneoplastic myasthenia gravis is given. We suggest abnormal auto-antigen-specific positive selection of naive T cells as the essential molecular mechanism by which thymomas contribute to the autoimmunization against the acetylcholine receptor and other muscle proteins.

Blastoid variants of mantle cell lymphoma: frequent bcl-1 rearrangements at the major translocation cluster region and tetraploid chromosome clones

Sixty-four cases of mantle cell (centrocytic) non-Hodgkin's lymphomas have been analyzed for their cytomorphologic features, proliferation indices, bcl-1 rearrangements, p53 expression patterns, and DNA content by both interphase cytogenetic and DNA flow cytometric analyses. According to cytomorphology, three subtypes were recognized: a common, a lymphoblastoid, and a pleomorphic variant of mantle cell lymphoma (MCL). Blastoid MCL subtypes were characterized by distinctly elevated mitotic counts (57 and 51/10 HPF v 21/10 high-power fields in common MCL), proliferation indices (58% and 53% v 27% in common types, respectively; P < .001), frequent bcl-1 rearrangements at the major translocation cluster locus (59% v 40%), and overexpression of p53 (21% v 6%). However, the most interesting finding was a striking tendency of blastoid MCL subtypes to harbor chromosome numbers in the tetraploid range (36% of lymphoblastoid and 80% of pleomorphic types v 8% of common variants, P < .001), a feature clearly separating these neoplasms from other types of B-cell non-Hodgkin's lymphoma and possibly being related to cyclin D1 overexpression. Our data indicate that, although characterized by a uniform immunophenotype and common biologic background, MCL shows a broad spectrum of morphologic features ranging from small cell to blastoid types and that the morphologic spectrum is mirrored by distinct biologic features.

Differential expression of apoptosis receptors on diffuse and intestinal type stomach carcinoma

BACKGROUND

Intestinal and diffuse adenocarcinomas of the stomach differ in phenotypic properties, morphology, and growth behavior. Apoptosis (programmed cell death) is induced via specific cell-surface receptors (SC-1, Fas/APO-1/CD95) and coregulated by intracellular molecules (bcl-2, p53, etc.); the success of apoptotic processes is dependent on the expression of these signals. Differences in the expression of specific apoptosis receptors and intracellular-related signals might help to explain the molecular pathogenesis of these two types of stomach adenocarcinoma.

METHODS

Immunohistochemical studies were performed on frozen sections of tumor tissue using human monoclonal antibody SC-1 and murine monoclonal antibodies Fas and p53, followed by peroxidase-coupled second antibodies. To determine binding of SC-1 and Fas antibodies to stomach carcinoma cells on the molecular level, Western blot analysis was performed with cell extract preparations from stomach carcinoma cells. To investigate functional apoptotic activity, MTT assays were performed with SC-1 and Fas antibodies on stomach carcinoma cells.

RESULTS

On frozen sections intestinal type stomach carcinoma cells demonstrate little or no expression of SC-1 and Fas receptors (4 of 17 and 1 of 17, respectively). Diffuse type stomach carcinoma cells show just the opposite: greater than 50% express SC-1 and Fas at a high level (15 of 30 and 22 of 30, respectively). Normal stomach mucosa is negative with both antibodies. Expression of p53 is positively correlated with intestinal type carcinomas (11 of 17) but not with diffuse type (5 of 30). In functional studies MTT assay) the SC-1 and Fas antibodies react with stomach carcinoma by inducing apoptosis and inhibiting growth. On Western blot analysis of extracts from stomach carcinoma cells, SC-1 detects a protein of 50 kilodalton (kD) and Fas proteins of approximately 30, 45, and 60 kD.

CONCLUSIONS

These data indicate that gastric carcinoma cells of the intestinal and diffuse type differ in their expression of the apoptotic receptors SC-1 and Fas and the tumor suppressor gene product p53. These new data on phenotypic differences support the hypothesis that these two types of stomach carcinoma do not only differ in morphology, growth pattern, and risk factors but also in genetic pathways.

Endothelial cells are the major source of sICAM-1 in rheumatoid synovial tissue

The objective of this research was to investigate the cellular source of soluble ICAM-1 (siCAM-1) from rheumatoid synovial tissue (RS) and its relation to sICAM-1 in synovial fluid (SF) and serum, and to study the expression of ICAM-1 in isolated cells of RS. sICAM-1 was determined by using the enzyme-linked immunosorbent assay (ELISA) and Western blot analysis in supernatants from RS cultured for short periods (n = 19), in SF (n = 7) and in serum (n = 19). ICAM-1 expression, vascularization and inflammatory infiltration (CD3, CD68, CD22) were characterized immunohistochemically in cytospin preparations (n = 18), cryosections (n = 18) and in conventionally stained paraffin sections (n = 19) of RS. The degree of RS vascularization was analysed morphometrically in immunohistochemically stained cryosections (factor VIII related antigen). We found 90-kD sICAM-1 in supernatants of cultured cells, in SF and in sera. sICAM-1 in cellular supernatant correlated significantly (P < 0.01) with SF sICAM-1. The amount of sICAM in cellular supernatants showed no correlation to the score of inflammatory infiltration, but correlated significantly (P < 0.001) with the vascularization index of RS. The percentage of ICAM-1-expressing cells correlated significantly (P < 0.001) with the percentage of CD68-positive macrophages, but not with CD3- and CD22-positive lymphocytes. Macrophages, multinucleated giant cells and endothelial cells exhibited a higher expression of ICAM-1 as compared to lymphocytes and fibroblasts. The differential expression of ICAM-1 on infiltrating leucocytes and resident cells of RS indicates a functional role of ICAM-1 in the local inflammatory process. SF sICAM-1 originated in RS, but serum sICAM-1 did not. Shedding of sICAM-1 by RS was independent of inflammatory infiltration, but depended on the degree of vascularization, indicating that endothelial cells are the major source of sICAM-1 in RS.

Receptor analysis of idiotype antibodies derived from MALT type B-cell lymphoma hybridomas

The generation of human antibodies derived from extranodal MALT type B-cell lymphomas allows to evaluate steps in their pathogenesis as well as to establish potential immunological therapies. Intraclonal diversity and the existence of bystander nonmalignant B-cells outline the need for reliable identification of the tumor immunoglobulin representing hybridomas. Human heterohybridomas were generated from five cases of MALT type B-cell lymphomas (4 low grade, one high grade) by the fusion of lymphoma B-cells with the murine myeloma cell line NSO and tested for isotype identity with the tumor. RT-PCR using VH Fr1/JH primers was performed with RNA of tumors and hybridomas that share the same isotype with the tumor. PCR-products were sequenced directly. In each case lymphomas were hybridized with a comparable fusion efficiency. DNA sequence analysis of the immunoglobulin heavy chain identified one or more hybridomas derived from the tumor. However some other hybridomas which share the same isotype with the tumor, may be different in their VH family or their sequence. Hybridomas can be used as a tool for the research on the MALT lymphoma immunoglobulin receptor. For the identification of tumor immunoglobulin, secreting hybridomas sequencing and the check of molecular identity is indispensable after isotype determination.

Nature and sequence of simian immunodeficiency virus-induced central nervous system lesions: a kinetic study

To determine the onsets and specificities of neuropathological features observed after simian immunodeficiency virus (SIV) infection of macaques, brains of 19 clinically unaffected rhesus monkeys (group A) were examined after intervals ranging from 1 to 48 weeks post-infection and compared to 8 animals with AIDS (group B) as well as to 8 uninfected controls. Based on morphological and virological parameters, seven patterns specific for SIV infection of the central nervous system (CNS) were discerned. In both groups of infected but not control animals, we found mononuclear aggregates in meninges, perivascular space, and choroid plexus stroma (designated pattern 1), isolated infected cells within CNS parenchyma (pattern 2), axonal degeneration (pattern 3), spongy change (pattern 4), microglial proliferation (pattern 5), and small vessel proliferation (pattern 6). SIV encephalitis (pattern 7) was only evident in animals with clinically evident disease. Changes characteristic of patterns 3, 5 and 6 appeared to be chronic and non-progressive, whereas lesions of patterns 1, 2 and 4 appeared to have progressed in animals with AIDS. The main component of mononuclear aggregates in animals of group A were lymphocytes, in contrast to animals of group B, in which macrophages dominated the inflammatory infiltrates. Altogether, our results demonstrate that subtle leukoencephalopathy was a specific feature of clinically silent as well as clinically evident phases of SIV infection. This might explain the neurological impairment of HIV-positive non-AIDS individuals.