Kallikrein 4 is expressed in malignant mesothelioma--further evidence for the histogenetic link between mesothelial and epithelial cells

The objective of this study was to analyze Kallikrein 4 protein (hK4) expression in effusions and solid tumors of patients diagnosed with malignant mesothelioma (MM) and compare hK4 expression in MM with that in breast and ovarian adenocarcinomas. Sections from 65 MM (21 effusions, 44 solid tumors) and 63 breast carcinomas (28 effusions, 35 solid tumors) were stained for hK4 using immunohistochemistry. Results were compared with our previously published data for 284 ovarian carcinomas (181 effusions, 103 solid tumors). Expression of hK4 was detected in 26/65 (40%) MM and 52/63 (83%) breast carcinomas. Ovarian carcinoma showed staining values that were comparable to those in breast carcinoma (expression of hK4 in 144/181; 80% effusions and 85/103; 83% solid tumors). As opposed to our previous findings in ovarian carcinoma, hK4 expression was higher in solid tumors when compared with to effusions in both MM (P = 0.013) and breast carcinoma (P = 0.002). Comparative analysis of the three tumor types showed significantly higher expression in ovarian and breast adenocarcinomas when compared with MM (P < 0.001). In conclusion, hK4 is frequently expressed in MM, with higher levels detected in solid tumors, although its expression is more limited than in gynecological adenocarcinomas. The presence of hK4 in MM, a non-hormonally regulated tumor, provides further support to the histogenetic link between mesothelial and epithelial cells.     

Expression of the chromatin remodeling factor Rsf-1 is down-regulated in breast carcinoma effusions

We recently identified Rsf-1, a chromatin-remodeling gene, as a potential oncogene that is frequently amplified and overexpressed in ovarian serous carcinoma, and demonstrated that its expression in carcinoma cells in effusions is associated with poor prognosis. In the present study, we assessed the clinical significance of Rsf-1 overexpression in breast carcinoma effusions. Formalin-fixed paraffin-embedded sections from 47 effusions were analyzed for Rsf-1 expression by immunohistochemistry. Matched primary tumors (n = 30) and solid metastases (n = 26) from 30 patients were additionally studied. Rsf-1 expression in tumor cells in effusions was analyzed for association with clinicopathologic parameters and survival. Rsf-1 protein expression was found in carcinoma cells in 34 (72%) of 47 effusions, 24 (80%) of 30 primary carcinomas, and 24 (92%) of 26 metastases. Rsf-1 immunoreactivity in effusions showed no association with HER-2 or hormone receptor status. Rsf-1 expression level was significantly lower in effusions compared with primary tumors (P = .026 and P = .011 for extent and intensity, respectively) and lymph node metastases (P = .023 and P = .013 for extent and intensity, respectively). Staining extent and intensity were both significantly lower in breast compared with ovarian carcinoma effusions (P = .001 for extent, P < .001 for intensity). Rsf-1 expression showed no association with survival. In conclusion, in contrast to ovarian carcinoma, Rsf-1 expression is down-regulated in breast carcinoma cells in effusions compared with the solid counterparts and has no prognostic role at this anatomic site.     

Expression and clinical role of the bric-a-brac tramtrack broad complex/poxvirus and zinc protein NAC-1 in ovarian carcinoma effusions

We recently identified NAC-1, member of the bric-a-brac tramtrack broad complex/poxvirus and zinc domain family, as an overexpressed gene in ovarian serous carcinoma and found more frequent NAC-1 protein expression in recurrent compared to primary tumors. In the present study, we assessed the clinical significance of NAC-1 expression in ovarian carcinoma effusions. Formalin-fixed, paraffin-embedded sections from 176 effusions (137 peritoneal, 39 pleural) and 197 corresponding solid tumors (69 primary tumors, 128 solid metastases) were analyzed for NAC-1 expression using immunohistochemistry. Staining intensity and extent results were analyzed for possible association with clinicopathologic parameters and survival. Nuclear NAC-1 immunoreactivity was found in carcinoma cells in 98% of (173/176) effusions, 94% (65/69) of primary tumors, and 95% (121/128) of metastases. Staining intensity and extent were significantly higher in effusions compared with matched solid tumors (P = .002 for intensity, P = .003 for extent compared with primary tumors; P < .001 for both intensity and extent compared with metastases). Furthermore, NAC-1 expression intensity was significantly higher in specimens obtained after the administration of chemotherapy (P = .002) and correlated with shorter progression-free survival (PFS) in analysis of 62 patients with post-chemotherapy effusions (P = .039). International Federation of Gynecology and Obstetrics stage (IV versus III) was the only clinical parameter associated with PFS in this group (P = .004). In Cox analysis, only the International Federation of Gynecology and Obstetrics stage was an independent predictor of shorter PFS (P = .009). In conclusion, NAC-1 expression is higher in ovarian carcinoma cells in effusions compared with their solid tumor counterparts. NAC-1 is up-regulated in tumor cells after chemotherapy, suggesting a role for this protein in tumor progression and in the development of chemotherapy resistance in ovarian cancer.     

MUC4 is upregulated in ovarian carcinoma effusions and differentiates carcinoma cells from mesothelial cells

Using gene expression arrays, we recently showed that MUC4 expression is significantly higher in ovarian/primary peritoneal serous carcinoma (OC/PPC) compared to diffuse peritoneal malignant mesothelioma (DMPM). In the present study, we analyzed the anatomic site-related expression of MUC4 in OC/PPC and studied its prognostic role. We additionally studied the ability of MUC4 to differentiate between OC/PPC and reactive mesothelial cells (RMC). OC/PPC effusions (n = 142) and benign reactive effusions (n = 10) were immunostained for MUC4 expression. Immunoreactivity was scored in carcinoma cells and RMC and was compared with tumor cell expression in 60 previously studied primary carcinomas and solid metastases and analyzed for association with clinicopathologic parameters, including survival. MUC4 was detected in carcinoma cells in 141/142 (99%) effusions, with comparable expression in peritoneal and pleural effusions. RMC were present in 72 malignant effusions and were MUC4-negative in all specimens, as well as in the 10 reactive effusions. MUC4 expression in carcinoma cells in effusions was significantly higher than in primary carcinomas and solid metastases (P < 0.001). Higher MUC4 expression was seen in tumors from older (>60 year) patients (P = 0.049). No association was found between MUC4 expression and other clinicopathologic parameters, including survival. MUC4 is universally expressed in OC/PPC effusions and is upregulated at this anatomic site compared to primary carcinomas and solid metastases. The data in the present study, together with our earlier report, show that MUC4 is an excellent marker for differentiating OC/PPC from both benign and malignant mesothelial cells.     

Expression of HLA-G in malignant mesothelioma and clinically aggressive breast carcinoma

The aim of the present study was to evaluate HLA-G expression in breast carcinoma and malignant mesothelioma (MM). Malignant breast carcinoma effusions (46) and corresponding solid tumors (39) and 104 MM (26 effusions, 78 solid tumors) were analyzed using immunohistochemistry (IHC). HLA-G protein and mRNA expression were further studied using immunoblotting (IB) and RT-PCR. HLA-ABC expression was analyzed using flow cytometry (FCM). IHC showed predominantly focal HLA-G expression in 12 of 46 (26%) breast carcinoma effusions and 16 of 39 (41%) solid lesions. In MM, 20 of 78 (26%) solid lesions and 14 of 26 (54%) effusions were focally HLA-G positive. Expression in MM was higher in effusions (p=0.008). IB showed more frequent HLA-G expression in MM compared with breast carcinoma effusions, while RT-PCR showed HLA-G mRNA expression in both tumors. FCM showed conserved HLA-ABC expression in 15 of 15 effusions. Breast cancer patients with HLA-G-positive tumor cells had shorter disease-free survival (mean 37 vs 85, median 25 vs 31 months), though not significantly (p=0.14). In conclusion, HLA-G is focally expressed in MM and breast carcinoma, while HLA-ABC expression is conserved. However, the up-regulated expression of HLA-G in MM effusions and its possible association with shorter disease-free survival in advanced stage of breast carcinoma suggest a possible role in immune response evasion in some tumors.     

Interleukin-8 and vascular endothelial growth factor mRNA and protein levels are down-regulated in ovarian carcinoma cells in serous effusions

Angiogenic factors are involved in tumor growth and spread. The aim of this study was to evaluate the expression of angiogenesis-related genes in malignant serous effusions of patients with advanced-stage (FIGO stage III and IV) ovarian carcinoma. In addition, to compare the results for carcinoma cells in effusions with corresponding primary tumors and metastatic lesions, and analyze their prognostic role. Sections from 66 effusions and 90 primary and metastatic lesions from 62 ovarian and primary peritoneal carcinoma patients, were evaluated for expression of basic fibroblast factor (bFGF), interleukin-8 (IL-8), and vascular endothelial growth factor (VEGF) using mRNA in situ hybridization (ISH). Protein expression was evaluated in a subset of specimens using immunohistochemistry (IHC). ISH results were correlated with clinical parameters. In both effusions and solid tumors, bFGF mRNA was the most commonly expressed factor (93% of effusions and 95% of solid tumors) followed by IL-8, while VEGF was expressed in a minority of the specimens (P<0.001 for bFGF vs. IL-8 and VEGF). In solid tumors, angiogenic mRNA expression was seen in both tumor and stromal cells in the majority of positive cases. ISH results did not differ in primary and metastatic tumors. However, carcinoma cells in effusions showed down-regulated expression of VEGF, when compared with both primary tumors (P=0.029) and metastases (P=0.015). IL-8 showed a similar down-regulation in effusions, when compared with metastases (P=0.005). IHC showed excellent agreement with mRNA findings on protein level. In the study of clinico-pathologic parameters, IL-8 mRNA expression in effusions was associated with higher tumor grade (P=0.044). Angiogenic gene expression in effusions showed no correlation with patient age, previous treatment, residual tumor size, FIGO stage or disease outcome in survival analysis (P>0.05). Peritoneal and pleural effusions showed similar expression patterns. In conclusion, bFGF is the major angiogenic factor expressed in ovarian carcinoma at the mRNA level. It is highly expressed in both solid tumors and serous effusions, while IL-8 and VEGF are down regulated in carcinoma cells in effusions, possibly due to the lack of interaction with stromal cells. mRNA expression of VEGF, bFGF, and IL-8 does not appear to be a predictor of disease outcome in advanced-stage ovarian carcinoma. Carcinoma cells in pleural and peritoneal effusions show a similar metastatic expression profile, in agreement with our previous findings, supporting the true metastatic nature of ovarian carcinoma cells in ascites. (R.R. is affiliated with the David R. Bloom Center for Pharmacy at the Hebrew University) affiliated with Sackler School of Medicine, Tel-Aviv University This revised version was published online in July 2006 with corrections to the Cover Date.     

Expression of the 67 kDa laminin receptor and the α6 integrin subunit in serous ovarian carcinoma

The aim of this study was to analyze the expression of two laminin receptors, the 67kDa laminin receptor (LBP) precursor and the α6 integrin subunit, in effusions and solid tumors of patients diagnosed with serous ovarian carcinoma and to evaluate their predictive role. Eighty-eight effusions and one hundred sixteen primary (= forty-one) and metastatic (= seventy-five) ovarian carcinomas were evaluated for expression of the above-mentioned mRNAs using in situ hybridization (ISH). LBP protein expression was studied in 24 effusions and 43 solid tumors using immunohistochemistry (IHC). α6 integrin subunit protein expression was studied in 27 effusions using flow cytometry (FCM). Expression of LBP mRNA was frequently detected in both carcinoma (92 of 116 cases, 79%) and stromal (79 of 116 cases, 68%) cells in solid tumors. Expression was still higher in cancer cells in effusions (85 of 88 specimens, 96%). In contrast, α6 integrin subunit was less frequently detected in both solid tumors (33 of 116; 28% in carcinoma cells, 23 of 116; 20% in stromal cells) and effusions (36 of 88; 41%). LBP protein expression was found in 19 of 24 (79%) effusions and 40 of 43 (93%) solid tumors, and was higher in effusions of patients who received chemotherapy prior to tapping (P = 0.024). FCM showed protein expression of the α6 integrin subunit in 17 of 27 (63%) effusions. Expression of the α6 integrin subunit mRNA in tumor cells of solid lesions was significantly lower in solid tumors of FIGO stage-IV patients compared to those of patients diagnosed with stage-III-disease (P = 0.004), and its absence predicted significantly shorter overall survival (OS) in univariate analysis (P = 0.018). Absence of α6 integrin subunit protein expression using FCM predicted median OS of 12 months compared to 26 months for patients with tumors expressing the protein, although this finding did not reach significance (P = 0.27). In conclusion, as opposed to previous reports, both mRNA and protein expression of the α6 integrin subunit do not appear to be down-regulated in effusions compared to solid tumors. Loss of α6 integrin subunit mRNA (and possibly protein) expression is a novel prognostic marker in advanced-stage ovarian carcinoma. LBP mRNA and protein expression is independent of that of the α6 integrin subunit in both solid tumors and effusions of serous ovarian carcinoma. This revised version was published online in July 2006 with corrections to the Cover Date.     

Claudin upregulation in ovarian carcinoma effusions is associated with poor survival

Claudins are tight junction proteins that are highly expressed in ovarian carcinoma (OC). The objective of this study was to analyze the anatomic site-related expression and clinical role of claudins in OC. Effusions (n = 218), corresponding primary tumors (n = 81), and solid metastases (n = 164) (total = 463 tumors) were immunostained for claudin-1, claudin-3, claudin-4, and claudin-7. Results were analyzed for association with anatomic site, clinicopathologic parameters, and survival. All 4 claudins were expressed in >85% of tumors at all anatomic sites. However, staining extent of all except claudin-4 was significantly higher in effusions compared with both primary carcinomas and solid metastases (P < .001). In univariate survival analysis of the entire cohort, higher claudin-3 (P = .038) and claudin-7 (P = .035) expression in effusions correlated with shorter overall survival (OS), with similar results for claudin-7 in analysis of progression-free survival (P = .026). In separate analysis for patients with prechemotherapy effusions, higher claudin-7 expression correlated with shorter OS (P = .045). For patients with postchemotherapy effusions, higher claudin-1 (P = .018) and claudin-3 (P = .009) expression correlated with shorter OS. In multivariate survival analysis of the entire cohort, claudin-7 expression was an independent predictor of poor progression-free survival (P = .017). Claudin-3 independently predicted poor OS for patients with postchemotherapy effusions (P = .012). With the exception of claudin-4, claudins are upregulated in OC effusions compared with solid tumors, in agreement with our previous data for cadherins and integrins in this cancer type, suggesting a prosurvival role for these surface molecules. Claudin-3 and claudin-7 expression in effusions independently predicts poor survival in OC.     

Survivin, a member of the inhibitors of apoptosis family, is down-regulated in breast carcinoma effusions

We analyzed the expression and prognostic role of inhibitors of apoptosis in breast carcinoma effusions. We used immunoblotting to analyze 22 effusions for XIAP, survivin, and livin expression. Based on immunoblotting results, 49 effusions and 46 corresponding solid tumors were immunostained for XIAP and survivin. Results were analyzed for association with anatomic site, clinicopathologic parameters, and survival. Immunoblotting showed frequent expression of XIAP and survivin and no expression of livin. Carcinoma cells in effusions showed lower survivin immunostaining compared with lymph node metastases (P = .008) and primary carcinomas (P = .041). Higher cytoplasmic survivin expression correlated with poor disease-free survival for patients with postchemotherapy effusions (P = .035). XIAP and survivin, but not livin, are frequently expressed in advanced breast carcinoma. Survivin is down-regulated in effusions compared with solid tumors, possibly in relation to the different cellular economy at this anatomic site. Survivin expression may predict disease-free survival for patients with postchemotherapy effusions.     

Carbohydrate antigen expression in primary tumors, metastatic lesions, and serous effusions from patients diagnosed with epithelial ovarian carcinoma: evidence of up-regulated Tn and Sialyl Tn antigen expression in effusions

The object of this study was the investigation of carbohydrate antigen expression in malignant epithelial cells and benign mesothelial cells in serous effusions from patients diagnosed with epithelial ovarian carcinomas. In addition, to compare antigen expression in carcinoma cells in effusions with those of corresponding primary tumors and metastatic lesions. Sections from 63 malignant effusions from ovarian carcinoma patients and 15 reactive effusions were immunohistochemically stained, using 5 monoclonal antibodies for Lewis(y), Sialyl Lewis(x), Tn, and Sialyl Tn antigens. Tissue sections (n = 97) from corresponding primary ovarian carcinomas and metastatic lesions, as well as from 12 malignant mesotheliomas, were additionally stained using the above panel. Staining for the 4 antigens was seen in carcinoma cells in serous effusions in the majority of cases (range = 71% to 85%). In contrast, immunoreactivity was detected in mesothelial cells in only 6% to 23% of the specimens studied (P < .001 for all 5 markers). With the exception of B3 antibody against Lewis(y) antigen, malignant mesotheliomas stained negative, infrequently showing focal immunoreactivity. An up-regulation of Tn and Sialyl Tn expression was detected in carcinoma cells in effusions when compared with both primary tumors (P < .003 and P < .007, respectively) and metastatic lesions (P < .034 and .041, respectively). Cancer-associated carbohydrate antigens can thus be used as an adjunct in the differentiation between malignant epithelial and reactive mesothelial cells. Ovarian carcinoma cells in effusions show up-regulation of Tn and Sialyl Tn, possibly representing a transient phenotypic alteration facilitating metastasis.     

Netrin‐4 is upregulated in breast carcinoma effusions compared to corresponding solid tumors

We recently identified overexpression of the NTN4 gene in breast carcinoma effusions compared to primary carcinomas using gene‐expression arrays. The objective of this study was to validate this finding at protein level and analyze the clinical role of Netrin‐4 in breast carcinoma effusions. We additionally studied Netrin‐4 expression and its clinical relevance in Müllerian (ovarian, peritoneal, and tubal) carcinoma effusions. Sections from 82 breast carcinomas (53 effusions and 29 solid tumors) and 57 Müllerian carcinoma effusions were stained for Netrin‐4 using immunohistochemistry. Immunoreactivity was scored in carcinoma cells and analyzed for association with clinicopathologic parameters, including survival. In breast carcinoma, expression of Netrin‐4 was detected in carcinoma cells in 30/53 (57%) effusions compared to 3/29 (10%) solid tumors (P < 0.001). Netrin‐4 was further expressed in 31/57 (54%) Müllerian carcinoma effusions. No association was found between Netrin‐4 expression in breast or Müllerian carcinoma effusions and clinicopathologic parameters, including survival. Our data provide validation on protein level of upregulated Netrin‐4 expression in breast carcinoma effusions. The frequent expression of Netrin‐4 in Müllerian carcinoma effusions suggests a biological role for this molecule in metastases from gynecological malignancies. Netrin‐4 expression in effusions does not appear to be a predictor of disease outcome. Diagn. Cytopathol. 2011. © 2010 Wiley‐Liss, Inc.     

EMMPRIN (extracellular matrix metalloproteinase inducer) is a novel marker of poor outcome in serous ovarian carcinoma

EMMPRIN is a member of the immunoglobulin superfamily of adhesion molecules and has a role in the activation of several matrix metalloproteinases (MMP). The objective of this study was to investigate the expression of EMMPRIN in effusions, primary and metastatic tumors of serous ovarian carcinoma patients, as well as to evaluate its association with clinicopathologic parameters and with MMP and integrin expression. Eighty effusions and eighty-three solid lesions were evaluated for expression of EMMPRIN mRNA using in situ hybridization (ISH). Protein expression was studied in 75 effusions and 55 biopsies using immunohistochemistry (IHC). EMMPRIN mRNA and protein were detected in carcinoma cells in 63/80 (79%) and 64/75 (85%) effusions, respectively. Expression was similar in peritoneal and pleural effusions. EMMPRIN was co-expressed with MMP-1 (P<0.001), MMP-9 (P=0.006) and the αv (P=0.013) and β1 (P=0.029) integrin subunits. In solid lesions, EMMPRIN localized most often to tumor cells (51/83 using ISH, 51/55 using IHC), but was also expressed in stromal and endothelial cells in approximately one third of the cases. EMMPRIN mRNA expression in tumor cells was most frequent in peritoneal metastases (P=0.03). EMMPRIN expression in carcinoma cells of solid tumors showed an association with that of MMP-9 (P=0.018), while labeling of stromal cells showed co-localization with the β1 integrin subunit (P=0.043). In survival analysis, EMMPRIN protein expression in stromal cells of primary tumors (P=0.012) and in endothelial cells of all solid tumors (P=0.023) correlated with poor survival. In conclusion, EMMPRIN is a novel prognostic marker in ovarian carcinoma, and is co-expressed with other metastasis-associated molecules in this malignancy. The identical phenotype of carcinoma cells in pleural and peritoneal effusions provides further evidence to our theory that cells at these sites share similar genotypic and phenotypic profiles. This revised version was published online in July 2006 with corrections to the Cover Date.     

HMGA2 protein expression in ovarian serous carcinoma effusions, primary tumors, and solid metastases

The objective of this study was to analyze the expression and clinical role of the high mobility group AT hook (HMGA) protein in advanced-stage serous ovarian carcinoma. HMGA2 protein expression was investigated in 199 effusions and in 50 patient-matched primary tumors and solid metastases using immunohistochemistry. Results were analyzed for association with clinicopathologic parameters, including chemotherapy response, and survival. HMGA2 was expressed in tumor cells in 94.5 %, 96 %, and 90 % of specimens, respectively. There was no difference in HMGA2 expression between patient-matched samples from different anatomic sites (p > 0.3). HMGA2 expression in chemo-na?ve samples was significantly higher in older patients (p = 0.006, p = 0.01, and p = 0.005 for effusions, primary tumors, and solid metastases, respectively). No association was found with residual disease volume. Furthermore, HMGA2 expression was not associated with FIGO stage (p > 0.2), except in chemo-na?ve effusions (n = 106, p = 0.016). There was no difference in HMGA2 expression between chemo-na?ve samples and samples obtained post-chemotherapy in effusions (p = 0.2) or primary tumors (p = 0.1). However, solid metastases obtained after chemotherapy exposure had higher HMGA2 expression compared with chemo-na?ve samples (p = 0.032). HMGA2 expression was unrelated to chemotherapy response or survival. However, it was directly related to protein expression of the previously studied cancer stem cell marker Nestin (p = 0.01) and the gap junction protein claudin-7 (p = 0.02) and inversely related to the mRNA level of the E-cadherin repressor SIP1 (p = 0.02). This study provides evidence that HMGA2 is universally expressed in advanced-stage ovarian serous carcinoma irrespective of anatomic site, suggesting that HMGA2 may have a clinical role as therapeutic target.     

Expression of inhibitor-of-apoptosis protein family members in malignant mesothelioma

Inhibitor-of-apoptosis proteins (IAPs) mediate cancer cell survival and chemoresistance. We analyzed the expressions of X-linked IAP (XIAP), survivin, and livin in malignant mesothelioma. Ten effusions were analyzed for XIAP, survivin, and livin expression using immunoblotting. Based on the immunoblotting results, 112 mesotheliomas from 94 patients (pleural, n = 77; peritoneal, n = 35; solid, n = 68; effusions, n = 44) were immunostained for XIAP and survivin expression. Results were analyzed for associations with anatomic site (pleura versus peritoneum), specimen type (solid versus effusion), proliferation (Ki-67 score), and survival. Immunoblotting showed expression of XIAP in 9 of 10 effusions and that of survivin in 4 of 10 effusions, but no expression of livin. Immunohistochemistry showed cytoplasmic XIAP expression in 71 of the 112 (63%) tumors. XIAP expression was significantly higher in peritoneal mesotheliomas than in pleural mesotheliomas (P = .001) and in effusions than in solid lesions (P = .017). Cytoplasmic survivin was found in 75 of the 112 (67%) tumors and showed no site-related difference. Nuclear survivin was expressed in 37 of the 112 (33%) tumors, with a trend for positive association with the Ki-67 score (P = .051). Nuclear survivin (P = .003) and Ki-67 (P = .013) were downregulated in effusions as compared with solid tumors. Higher XIAP expression and Ki-67 score were associated with a trend for poor overall survival (P = .064 for both) in the univariate analysis. XIAP and survivin, but not livin, are frequently expressed in malignant mesotheliomas. Nuclear survivin expression is reduced in effusions as compared with solid lesions concomitantly with reduced proliferation. XIAP is upregulated in mesothelioma effusions and peritoneal mesotheliomas, suggesting a prosurvival role in malignant mesothelioma cells, particularly at these anatomic sites.     

E-cadherin and alpha-, beta-, and gamma-catenin protein expression is up-regulated in ovarian carcinoma cells in serous effusions

The aims of this study were firstly, to investigate the expression of E-cadherin complex proteins in ovarian carcinoma cells in serous effusions and in primary and metastatic lesions; and secondly to study the value of these four proteins and calretinin, a mesothelial marker, in the differential diagnosis of ovarian carcinoma cells from reactive mesothelial cells in effusions. Sixty-seven malignant effusions and 97 corresponding primary (n=36) and metastatic (n=61) lesions were immunohistochemically stained for E-cadherin and alpha-, beta-, and gamma-catenin. Staining extent and intensity were scored. Effusion specimens were additionally analysed for calretinin immunoreactivity. Membrane immunoreactivity for E-cadherin and alpha-, beta-, and gamma-catenin was detected on carcinoma cells in the majority of the effusions, but rarely on reactive mesothelial cells (p<0.001 for all markers). Calretinin immunoreactivity was confined to mesothelial cells (p<0.001). An association was seen between E-cadherin and alpha-catenin expression, in both effusions and solid tumours, and for beta-catenin in solid tumours (range p<0. 001 to p=0.014). Up-regulation of all four cadherin complex proteins was seen in carcinoma cells in effusions, when compared with corresponding primary tumours (range p<0.001 to p=0.028). As with effusions, metastatic lesions showed up-regulation of alpha-, beta-, and gamma-catenin when compared with primary carcinomas (p=0.002-0. 015). Carcinoma cells in effusions showed in addition elevated levels of E-cadherin when compared with metastatic lesions (p<0.001). Staining results in effusions showed no association with effusion site, tumour type or histological grade. Immunoblotting on 29 malignant effusions confirmed the presence of all four proteins in the majority of samples and co-precipitation of E-cadherin and beta-catenin was seen in ten specimens examined. E-cadherin complex proteins are widely expressed in ovarian carcinoma cells. Together with calretinin, they form a powerful battery of markers for the cytological diagnosis of carcinoma cells in effusions. The up-regulation of E-cadherin complex proteins in serous effusions and metastatic lesions may mark an early metastatic phenotype and possibly mediates survival of tumour cells at these sites through the inhibition of apoptosis.