Telomerase activity in human pleural mesothelioma

BACKGROUND: Gradual telomere erosion eventually limits the replicative life span of somatic cells and is regarded as an ultimate tumour suppressor mechanism, eliminating cells that have accumulated genetic alterations. Telomerase, which has been found in over 85% of human cancers, elongates telomeres and may be required for tumorigenesis by the process of immortalisation. Malignant mesothelioma is an incurable malignancy with a poor prognosis. The disease becomes symptomatic decades after exposure to carcinogenic asbestos fibres, suggesting the long term survival of pre-malignant cell clones. This study investigated the presence of telomerase in pleural malignant mesothelioma, which may be the target for future anti-telomerase drugs. METHODS: Telomerase activity was semiquantitatively measured in extracts from 22 primary pleural mesotheliomas, two benign solitary fibrous tumours of the pleura, four mesothelioma cell lines, and six short term mesothelial cell cultures from normal pleura using a non-isotopic dilution assay of the telomeric repeat amplification protocol. RESULTS: Twenty of the 22 primary mesotheliomas (91%) and all tumour derived mesothelioma cell lines were telomerase positive. Different levels of enzyme activity were observed in the tumours of different histological subtypes. Telomerase activity could not be detected in the six normal mesothelial cell cultures or in the two mesotheliomas. Both benign solitary fibrous tumours showed strong telomerase activity. CONCLUSIONS: Telomerase activity is found in a high proportion of mesotheliomas and anti-telomerase drugs might therefore be useful clinically. The results are consistent with the hypothesis that telomerase activity may be a feature of carcinogenesis in mesotheliomas and possibly in many other cancers.     

Monoclonal antibody K1 reacts with epithelial mesothelioma but not with lung adenocarcinoma.

Immunoperoxidase histochemical staining of cryostat sections from human tumor tissues revealed that a murine monoclonal antibody (MAb), K1, can distinguish epithelial mesotheliomas from lung adenocarcinomas. All of 15 epithelial-type mesotheliomas and all four mixed type mesothelioma samples, but none of 23 lung adenocarcinomas with different degrees of histologic differentiation demonstrated reactivity with antibody K1. Of the cell populations in each mesothelioma tested, 80% to 100% showed strong and homogeneous staining with MAb K1. Immunofluorescence analysis of live cultured cells from an epithelioid mesothelioma (H-meso) and several lung carcinoma cell lines as well as a pleural effusion of a patient with mesothelioma also showed selective reactivity of K1 with the mesothelioma cells. These data indicate that K1 can be useful as a mesothelial cell marker for the differential pathological diagnosis of the epithelial form of mesothelioma; K1 may also be useful in the study of the pathogenesis, immunodiagnosis, and immunotherapy of epithelial-type and mixed-type human malignant mesothelioma.     

Omega-6 fatty acids can inhibit Fas-mediated apoptosis in a human colorectal carcinoma cell line: a potential mechanism for escape from immune surveillance

The Fas/Fas ligand pathway may play an important role in the pathogenesis of colorectal carcinoma by allowing tumor cells to evade host immune defenses. Since dietary fats, in particular omega-6 fatty acids, facilitate tumor development their influence on the Fas/Fas ligand pathway needs to be elucidated. The purpose of this study was to determine the effect of membrane free fatty acid (FFA) alterations on Fas expression and sensitivity. Two human colorectal carcinoma cell lines (CX-1 and CCL-188) were grown in cell culture media supplemented with omega-3 (docosahexanoic acid) and omega-6 (linoleic acid) fatty acids. Membrane alterations were confirmed by gas chromatography (GC). Cell surface Fas expression was determined with flow cytometry using an anti-Fas monoclonal antibody. Sensitivity to Fas mediated apoptosis was measured by now cytometric measurement of fragmented DNA stained with propidium iodide. Appropriate changes in the membrane FFA composition were found by GC. Cell surface Fas expression was unaffected in either cell line. Omega-3 fatty acids did not alter Fas sensitivity for either cell line compared to control (CX-1: 59.7%, +/- 5.4 vs 51.4% +/- 7.1 for control, CCL-188: 54.3% +/- 8.6 vs 51.2% +/- 4.8 for control). Omega-6 fatty acids produced a significant decrease in Fas-mediated apoptosis (CX-1: 34.2% +/- 4.8 and CCL-188: 22% +/- 6.0, p < 0.05 vs control). These data indicate that although membrane FFA alterations did not affect Fas expression, omega-6 fatty acids significantly decreased Fas-mediated apoptosis. This inhibitory effect may protect colorectal carcinoma cells from lymphocyte Fas-mediated cell death.     

Malignant mesothelioma of the pleura: relation between histological type and clinical behaviour.

The differing clinical behaviour of malignant mesothelioma of different cell types was studied in 115 cases of pleural mesothelioma, classified histologically into epithelial (60), sarcomatous (25), and mixed (30). Epithelial mesotheliomas were associated with clinical features characteristic of carcinomas rather than sarcomas, including spread of tumour by direct extension, large pleural effusions, contralateral pleural effusions, ascites, metastases in regional lymph nodes, and occasional response to radiotherapy. Sarcomatous mesotheliomas were associated with clinical features more characteristic of sarcomas, with more frequent distant metastases, little or no effusion, and shorter survival. Mixed tumours had features of both, large pleural effusions occurring as frequently as with epithelial tumours, but survival being almost as poor as in sarcomatous cases. Despite these differences there is evidence from published reports that epithelial, sarcomatous, and mixed mesotheliomas have a common origin from mesothelial cells or their precursor cells.     

Synergism of Fas-mediated apoptosis and tumor necrosis factor on adriamycin cytotoxicity to transitional cell carcinoma

OBJECTIVE: To explore the accurate Fas antigenic expression in transitional cell carcinoma (TCC) cells and and compare its synergistic modulation on adriamycin cytotoxicity with alpha-tumor necrosis factor (TNF-alpha). METHODS: The expression of Fas antigen in normal urothelium and TCC cell lines was measured by flow cytometry. The Fas/Fas ligand reaction-induced cytotoxic changes in tumor cells were evaluated by microculture MTT technique. The synergism efficacy of Fas-mediated apoptosis and TNF-alpha on adriamycin cytotoxicity of TCC cells was analyzed. The Fas/Fas ligand-induced apoptosis in tumor cells was studied by annexin-V apoptotic cell expression and DNA ladder fragmentation analysis. RESULTS: 75% of TCC cell lines showed Fas antigen expression. The Fas expression was not influenced by in vitro growth density of tumor cells. Apoptosis of TCC cells was observed during 48 h of treatment after activation of the Fas/Fas ligand pathway. TNF-alpha had a higher cytotoxicity activity on TCC cells than Fas ligand (17 vs. 0.7%) while combination of both reagents had 30% increased synergistic cytotoxicity. The increasing rate of apoptotic body after 3 days of treatment was 74% in adriamycin, 32% in Fas ligand, 60% in TNF-alpha, 69% in Fas and adriamycin combination and Fas and TNF-alpha combination, 103% in combination of TNF-alpha and adriamycin, and 136% in combination of these three reagents individually. In the DNA ladder analysis, Fas ligand had a 1.5-fold increase of DNA fragmentation when compared with adriamycin while TNF-alpha had a 4.4-fold increase and triple combination had a 5.5-fold increase after 3 days of treatment. CONCLUSIONS: Although the Fas antigen expression is common in TCC cells and apoptosis can be activated by the Fas/Fas ligand pathway activation, the synergistic cytotoxicity of adriamycin by the Fas/Fas ligand pathway is lower than that of TNF-alpha.     

Malignant pleural mesothelioma producing human chorionic gonadotropin. Report of two cases.

Two cases of malignant pleural tumor producing human chorionic gonadotropin, one confirmed at surgery and autopsy and the other by biopsy, are reported. Both of the patients had bilateral gynecomastia with high levels of serum human chorionic gonadotropin. The first patient underwent panpleuropneumonectomy because of diffuse malignant pleural tumor, but died five months later due to recurrent disease. The histological diagnosis was diffuse, malignant, monophasic mesothelioma of the epithelial type. Immunostaining for alpha-, beta-human chorionic gonadotropin and human placental lactogen was positive in syncytiotrophoblast-like cells. The second patient had diffuse pleural tumor with massive effusion. A pleural biopsy specimen showed diffuse proliferation of epithelioid large cells. Immunostaining for alpha, beta-human chorionic gonadotropin and human placental lactogen was positive in mono- and multinucleated bizarre giant cells mimicking trophoblasts. A diagnosis of malignant mesothelioma with trophoblastic differentiation seemed most likely in both cases in view of the clinical and pathological findings. In both cases, results of mucin histochemistry and various immunohistochemical stains for antigens or with antibodies were consistent with diagnosis of mesothelioma except in a few cells in the choriocarcinomatous portion. This may be the first report describing human chorionic gonadotropin-producing malignant mesotheliomas of the pleura.     

Diagnostic significance of carcinoembryonic antigen in the differential diagnosis of malignant mesothelioma

The histologic and cytologic distinction of malignant mesothelioma from carcinomas metastatic to the pleura or peritoneum is often problematic. For this reason immunologic methods are being increasingly used as diagnostic adjuncts. This review summarizes 40 studies on the expression of carcinoembryonic antigen in mesotheliomas and in lung and other carcinomas involving the pleura or peritoneum. Carcinoembryonic antigen was identified immunohistochemically in 11% of mesotheliomas and in 84% of carcinomas examined and immunocytochemically (in serous effusions) in 4% and 58%, respectively. In serum and in pleural or ascitic fluid, significantly elevated levels of carcinoembryonic antigen are commonly associated with (lung) carcinomas but rarely with mesotheliomas. Thus, together with identification of the antigen in serum, pleural fluid, or ascitic fluid, immunohistochemical and immunocytochemical techniques for detecting carcinoembryonic antigen provide a valuable aid for distinguishing malignant mesothelioma from metastatic carcinomas.     

Localized malignant mesothelioma

Localized malignant mesotheliomas are uncommon sharply circumscribed tumors of the serosal membranes with the microscopic appearance of diffuse malignant mesothelioma but without any evidence of diffuse spread. Little is known about their behavior. We report 23 new cases. The mean age at presentation was 63 years, and the sex ratio was approximately 2:1 (male/female). Twenty-one tumors were pleural and 2 were peritoneal. Sixteen tumors reproduced microscopic patterns of diffuse epithelial mesotheliomas, 6 had mixed epithelial and sarcomatous patterns, and 1 was purely sarcomatous. After surgical excision of the tumor, 10 of 21 patients with follow-up data were alive without evidence of disease from 18 months to 11 years after diagnosis. Patients who died had developed local recurrences and metastases, but none had diffuse pleural spread. Localized malignant mesotheliomas should be separated from diffuse malignant mesotheliomas because of their localized presentation, quite different biologic behavior, and far better prognosis.     

Sensitization of immunoresistant prostate carcinoma cell lines to Fas/Fas ligand-mediated killing by cytotoxic lymphocytes: independence of de novo protein synthesis.

BACKGROUND: We recently reported that drug-resistant prostate tumor cells (DU145, PC-3) are resistant to Fas-mediated killing by cytotoxic lymphocytes, and that this resistance can be overcome by treatment with subtoxic concentrations of chemotherapeutic drugs. Fas belongs to the tumor necrosis factor (TNF) family of receptors. Since resistance to TNF-alpha-mediated killing has been shown to be due, in part, to the presence of protective factors and that inhibitors of protein synthesis can sensitize cells to TNF-alpha killing, we hypothesized that resistance to Fas-mediated killing may be due to similar mechanisms. Since sensitization is achieved with chemotherapeutic drugs, and some chemotherapeutic drugs can also inhibit protein synthesis, we tested whether sensitization of prostate tumor cells to Fas ligand (Fas-L) occurred through inhibition of protein synthesis in a manner analogous to that of TNF-alpha. METHODS: The effect of chemotherapeutic drugs on protein synthesis in DU145 and PC-3 cells was characterized by (3)H-leucine incorporation assays. We also determined the ability of inhibitors of protein synthesis and chemotherapeutic drugs to sensitize Fas and TNF-resistant DU145 cells to killing. The ability of RNA (actinomycin-D, Act-D) and protein synthesis inhibitors (cyclohexamide (CHX), emetine) to block drug-mediated sensitization to Fas-L killing was analyzed. Sensitivity to Fas-L killing was determined by the (51)Cr-release assay using human lymphokine-activated killer cells (LAK) and tumor-infiltrating lymphocyte (TIL) effector cells and the murine Fas-L-expressing PMMI cells. RESULTS: The drugs cis-diamminedichloroplatinum (II) (CDDP), adriamycin (ADR), and etoposide (VP-16) sensitized DU145 and PC-3 cells to Fas killing. CDDP and ADR, which sensitized DU145 and PC-3 cells to Fas-L- and TNF-mediated killing, inhibited de novo protein synthesis in both cell lines, while VP-16 only inhibited protein synthesis in DU145 cells. Further, neither CHX nor emetine sensitized DU145 or PC-3 cells to Fas-L-mediated killing, despite blocking >90% de novo protein synthesis. In contrast, CDDP, VP-16, and the protein synthesis inhibitors, Act-D and CHX sensitized DU145 cells to TNF-alpha killing. Finally, pretreating cells with protein synthesis inhibitors (CHX, emetine) did not abrogate drug-mediated sensitization to Fas-mediated killing. CONCLUSIONS: These findings demonstrate that downregulation of protective factors by protein synthesis inhibition may not be the primary mechanism of drug-mediated sensitization to Fas-L killing in prostate cell lines. These findings also suggest that drug-mediated sensitization to Fas-L killing may be due to modifications of preexisting gene products that participate in Fas-L-mediated apoptosis.     

Pleural mesotheliomas. Current knowledge]

Pleural mesotheliomas are rare primary tumors of the pleura. Three groups are classified under the term mesothelioma: 1) benign pleural mesothelioma for which complete surgical treatment is curative with a good prognosis; 2) localized malignant mesothelioma which is a fibrosarcoma, best treated by wide en-bloc resection; 3) diffuse malignant mesothelioma which is mainly of epithelial type. The prognosis is poor in spite of all therapeutic approaches using irradiation, chemotherapy and surgery, alone or in combination, and long-term survivals are uncommon. Two surgical approaches are currently available for patients with diffuse mesothelioma: radical extrapleural pneumonectomy and pleurectomy/decortication. Rigorous combinations of multimodality therapy are needed to improve local control and survival.     

Lymphokine-activated killer cell suppressor factor in malignant effusions

We examined the possibility that tumor-released products inhibit lymphokine-activated killer cell activation. Lymphokine-activated killer cells from human peripheral blood lymphocytes were activated with recombinant interleukin 2 for 4 days in the presence of malignant effusions or conditioned media from cultured cell lines (10% vol/vol). Eight of 10 malignant effusions/media suppressed the induction of lymphokine-activated killer cell cytotoxicity, as measured in a 4-hour sodium chromate release assay. Seven of 10 effusions/media inhibited lymphokine-activated killer cell proliferation. Suppression was both dose and time dependent. A representative suppressive effusion was fractionated by agarose gel chromatography, treated with detergents disruptive of ionic bonds and lipids, and refractionated using polyacrylamide gel chromatography. Seven suppressive fractions ranging in molecular weight from 1 x 10(5) to 3 x 10(5) d were isolated. It is speculated that this suppressor factor may represent a large multimeric structure with ionic-bonded individual suppressive components.     

Fas and Fas-ligand expression in human pancreatic cancer

OBJECTIVE: To investigate Fas and FasL expression in pancreatic tissues and cultured pancreatic cancer cell lines, and to assess the ability of anti-Fas antibodies to induce apoptosis. SUMMARY BACKGROUND DATA: Activation of the Fas receptor by Fas-ligand (FasL) results in apoptosis, and dysregulation of this pathway may contribute to abnormal cell proliferation. METHODS: Northern blotting and immunohistochemistry were used to compare Fas and FasL expression in normal and cancerous tissues. DNA 3'-OH end labeling was used to detect apoptotic cells. The effects of Fas activation on cell growth and signaling pathways were investigated in culture. RESULTS: Pancreatic cancers exhibited increased Fas RNA levels, whereas FasL mRNA levels were similar in both groups. Despite the colocalization of Fas and FasL in the cancer cells, an apoptotic signal was present in approximately 10% of these cells in only 2 of 16 cancer samples. Fas and FasL were coexpressed in all four cell lines, whereas Fas-associated phosphatase 1 was below the level of detection in all cell lines. Only COLO-357 cells underwent apoptosis after Fas activation. Apoptosis was associated with enhanced activation of jun kinase (JNK) and p38 mitogen-activated protein kinase (MAPK). In the presence of actinomycin D, Fas antibody also induced apoptosis in the other three cell lines. CONCLUSIONS: These results suggest that pancreatic cancer cells are resistant to Fas-mediated apoptosis by mechanisms excluding receptor downregulation or Fas-associated phosphatase upregulation and raise the possibility that Fas-mediated apoptosis may be dependent on the activation of the JNK/p38 MAPK pathway in these cells.     

Malignant vascular tumours of the pleura in "asbestos" workers and endothelial differentiation in malignant mesothelioma

BACKGROUND: Three cases of diffuse malignant vascular tumours of the pleura are described which mimicked malignant mesothelioma clinically and pathologically (so called "pseudomesothelioma"). All had occupational histories of exposure to asbestos. The relationship of these tumours to mesothelioma and asbestos exposure is discussed. METHODS: To examine the histogenetic relationship between mesothelioma and these three tumours an immunohistochemical analysis of vascular marker (CD31, CD34, and Von Willebrand factor) expression was undertaken in 92 cases of pleural mesothelioma, in addition to these three tumours. Electron microscopic fibre analysis of lung tissue was performed on each of the three cases to assess asbestos fibre content. RESULTS: Diffuse pleural epithelioid haemangioendotheliomas may closely resemble malignant mesothelioma clinically and pathologically but, of the 92 pleural mesotheliomas tested, none showed expression of CD31, CD34, and Von Willebrand factor. Although all three cases had claimed exposure to asbestos, ferruginous bodies typical of asbestos were only seen by light microscopy in case 2, and only in this subject was the asbestos fibre content raised in comparison with the range seen in a non-exposed background population. The latent period in the pleural epithelioid haemangioendotheliomas ranged from 18 to 60 years. CONCLUSIONS: Endothelial differentiation does not appear to occur in mesothelioma and therefore should be clearly separated from it. No definite association between pleural epithelioid haemangioendothelioma and exposure to asbestos can be made from this small series but further investigation is warranted.     

Metabolic significance of the pattern, intensity and kinetics of 18F-FDG uptake in malignant pleural mesothelioma

BACKGROUND: Malignant pleural mesothelioma is an aggressive neoplasm with a highly variable course. This pilot study evaluated the significance of the pattern, intensity and kinetics of 18F-FDG uptake in mesothelioma in the context of histopathology and surgical staging. METHODS: Sixteen consecutive patients with pleural disease on CT scan underwent 18F-FDG imaging. Imaging was performed with a dual detector gamma camera operating in coincidence mode. Semiquantitative image analysis was performed by obtaining lesion-to-background ratios (18F-FDG uptake index) and calculating the increment of 18F-FDG lesion uptake over time (malignant metabolic potential index (MMPi)). RESULTS: Twelve patients had histologically proven malignant mesotheliomas (10 epithelial, two sarcomatoid). Thirty two lesions were positive for tumour. Patterns of uptake matched the extent of pleural and parenchymal involvement observed on CT scanning and surgery. Mean (SD) 18F-FDG uptake index for malignant lesions was 3.99 (1.92), range 1.5-9.46. Extrathoracic spread and metastases had higher 18F-FDG uptake indices (5.17 (2)) than primary (3.42 (1.52)) or nodal lesions (2.99 (1)). No correlation was found between histological grade and stage. The intensity of lesion uptake had poor correlation with histological grade but good correlation with surgical stage. 18F-FDG lesion uptake increased over time at a higher rate in patients with more advanced disease. The MMPi was a better predictor of disease aggressiveness than the histological grade. CONCLUSIONS: This pilot study suggests that the pattern, intensity, and kinetics of 18F-FDG uptake in mesothelioma are good indicators of tumour aggressiveness and are superior to the histological grade in this regard.     

Fas-Fas ligand system in the peripheral blood of patients with renal diseases

To clarify the role of the Fas-Fas ligand (FasL) system in the peripheral blood from patients with various renal diseases, the Fas and FasL expression on mononuclear cells (MNCs) and serum levels of soluble Fas (sFas) and soluble FasL were investigated. Patients were selected from those with various types of glomerular diseases showing various degrees of renal function. Fas expression on MNCs was analyzed by a FACScan, sFas and soluble FasL were measured with an ELISA kit, and FasL expression on MNCs was counted using a FACScan after a bioassay. Fas-positive MNCs and sFas increased with statistical significance concomitantly with deterioration in renal function. Moreover, there was a significant correlation between them. sFas- and FasL-positive MNCs were significantly correlated with proteinuria. However, the Fas expression percentage on MNCs and/or serum levels of sFas did not correlate with the number of TUNEL-positive cells in the glomeruli. Also, there was no disease specificity in the activation of Fas. These results indicate that Fas expression on MNCs is activated in accordance with the deterioration in renal function without disease specificity, corresponding to the elevation of serum sFas levels to protect against Fas-mediated apoptosis.     

Pathology of mesothelioma

In this article, progress in distinguishing mesothelioma from mesothelial hyperplasia and fibrosing pleuritis was discussed. Advances in the immunohistochemical characterization of mesothelioma, in the recognition of entities that mimic mesothelioma, and in their distinction from mesothelioma were reviewed. Cytogenetic and molecular genetic contributions to the diagnosis of pleural synovial sarcoma were briefly summarized. The diagnosis of epithelial type mesothelioma can be established in most cases. Several mesotheliomas, however, especially rare subtypes, and sarcomatoid, desmoplastic, and poorly differentiated mesotheliomas continue to present diagnostic challenges.     

The selective epidermal growth factor receptor tyrosine kinase inhibitor PD153035 suppresses expression of prometastasis phenotypes in malignant pleural mesothelioma cells in vitro

OBJECTIVE: Malignant pleural mesothelioma is notoriously refractory to aggressive multimodality therapy. Epidermal growth factor receptor expression has been observed on malignant pleural mesothelioma cells. Epidermal growth factor receptor-mediated signaling promotes tumorigenesis and metastasis of cancer cells. The purpose of this study is to evaluate the ability of the epidermal growth factor receptor tyrosine kinase inhibitor PD153035 to abrogate the expression of prometastasis phenotypes in malignant pleural mesothelioma cells in vitro. METHODS: Epidermal growth factor receptor expression of malignant pleural mesothelioma cells and primary normal cells was quantitated by means of flow cytometry. PD153035-mediated growth inhibition was determined by means of 1-(4,5-Dimethylthiazol-2-yl)-3,5-diphenylformazan and clonogenic assays. Cell motility and invasion of extracellular matrix was evaluated with in vitro wound-healing and Matrigel invasion assays, respectively. Vascular epidermal growth factor levels in conditioned media were measured by using enzyme-linked immunosorbent assay. RESULTS: Epidermal growth factor receptor expression was detected on all 6 cultured malignant pleural mesothelioma cells, with 4 of 6 having normal receptor expression and 2 of 6 overexpressing the receptor. PD153035 suppressed cell motility and cell invasion through a Matrigel membrane, regardless of the baseline epidermal growth factor receptor expression. Decreased vascular epidermal growth factor production and significant inhibition of growth only occurred in malignant pleural mesothelioma cells that overexpress epidermal growth factor receptor. CONCLUSIONS: Epidermal growth factor receptor tyrosine kinase inhibitor PD153035 significantly inhibited motility and invasion in malignant pleural mesothelioma cells in vitro, regardless of their epidermal growth factor receptor expression levels. Inhibition of epidermal growth factor receptor-dependent signaling might be a useful strategy to diminish malignant pleural mesothelioma recurrence after aggressive cytoreductive surgery.     

Xenogeneic human NK cytotoxicity against porcine endothelial cells is perforin/granzyme B dependent and not inhibited by Bcl-2 overexpression

Because of organ shortages in clinical allotransplantation, the potential of pig-to-human xenotransplantation is currently being explored showing a possible critical role for natural killer (NK) cells in the immune response against xenografts. Therefore, we analyzed the cytotoxic pathways utilized by human natural killer cells (hNK) against porcine endothelial cells (pEC). Transmission electron microscopy of pEC cocultured with hNK cells showed both apoptotic and necrotic cell death, whereas soluble factors such as Fas ligand or TNFα did not induce apoptosis in pEC. NK lysis of pEC was abrogated by concanamycin A and ammonium chloride, reagents inhibiting the perforin/granzyme B (grB) pathway, but only partially blocked by caspase inhibition with z-VAD-fmk. Overexpression of bcl-2 protected pEC against apoptosis induced by staurosporine or actinomycin D, but failed to prevent hNK cell-mediated lysis. In conclusion, pEC are lysed in vitro by hNK cells via the perforin/grB pathway and are not protected from NK lysis by overexpression of bcl-2.     

The separation of benign and malignant mesothelial proliferations

The separation of benign from malignant mesothelial proliferations has emerged as a major problem in the pathology of the serosal membranes. For both epithelial and spindle cell mesothelial processes, true stromal invasion is the most accurate indicator of malignancy, but stromal invasion is often difficult to assess, especially in small biopsies. In the pleural cavity, deep penetration of a thickened and fibrotic pleura or penetration of mesothelial cells into the fat of the chest wall are good indicators of malignancy; however, superficial entrapment of mesothelial cells and glands by organizing effusions is common in benign reactions and needs to be distinguished from invasion. In the peritoneal cavity, invasion of fat or of organ walls is again the most reliable indicator of malignancy, but entrapment of benign cells in organizing granulation tissue or between fat lobules is frequent and confusing. Proliferations confined to the pleural or peritoneal space, particularly linear arrays of atypical mesothelial cells on the free surface, should not be called malignant in the absence of unequivocal invasion. Cytologic atypia is often not helpful in separating benign from malignant reactions, because benign processes are commonly atypical and mesotheliomas are often deceptively monotonous. Densely packed mesothelial cells within the pleural space are frequent in benign reactions, but densely packed mesothelial cells within the stroma favor a diagnosis of malignancy. Organizing effusions (fibrous pleurisy) typically show zonation with high cellularity and cytologic atypia toward the pleural space and increasing fibrosis with decreasing cellularity and lesser atypia toward the chest wall, whereas sarcomatous (including desmoplastic) mesotheliomas do not demonstrate this type of zonation. Elongated capillaries perpendicular to the pleural surface are seen in organizing effusions but are not a feature of sarcomatous mesotheliomas. The combination of a paucicellular storiform pattern, plus invasion of the stroma (including fat and adjacent tissues), or bland necrosis, overtly sarcomatous foci, or distant metastases, is required for the diagnosis of desmoplastic mesothelioma. Necrosis is usually a sign of malignancy but is occasionally seen in benign mesothelial reactions. Keratin staining is useful in indicating the distribution of mesothelial cells, and particularly in demonstrating penetration of mesothelial cells into the stroma or adjacent structures, but is of no help in separating benign and malignant proliferations because both are keratin-positive. Although both p53 and EMA staining have been proposed as markers of mesothelial malignancy, in our experience they are not helpful for the individual case.     

The intrapleural administration of recombinant interleukin-2 (rIL-2) to patients with malignant pleural effusion: Clinical trials

Recombinant IL-2 (rIL-2) was administered intra-pleurally according to an original protocol to 11 patients with malignant pleural effusion, 7 of whom suffered from breast cancer and 4 from esophageal cancer. The pleural effusions either disappeared or decreased roentgenographically, and malignant cells disappeared from all 13 pleural cavities in the 11 patients, confirming the validity of this therapy to be 100%. The mean survival time from the initial administration of rIL-2 was 15.9 months. We ensured that the concentration of IL-2 in the effusion was maintained at a high level for a sufficient period of time, and that the lymphokine-activated killer (LAK) activity of lymphocytes in the effusion was augmented. Fever, eosinophilia, and a transient increase in the pleural effusion were the main side effects, but the symptoms were temporary and not serious. The results of this study therefore suggest the efficacy of intrapleural rIL-2 for patients with malignant pleural effusion.