Detection of integrins in formalin-fixed, paraffin-embedded tissues

Novel approach to identifying autoantibodies in rheumatoid synovitis with a biotinylated human autoantigen library and the enzyme-labeled antigen method

Synovial tissue in rheumatoid arthritis (RA) shows dense infiltration of plasmacytes. The purpose of the present study is to identify and localize autoantibodies produced in these immunocytes in RA synovitis. We developed a novel screening system for detecting specific autoantigens. Protein antigens recognized by antibodies in the serum and synovial tissue extract from five RA patients were screened with the AlphaScreen method. For screening, a biotinylated human autoantigen library was constructed by the wheat germ cell-free protein synthesis system. The AlphaScreen analysis of 2183 proteins detected a limited number of antigens reactive with the serum and synovial tissue extract. Eighteen biotinylated proteins, containing top five showing high signals in each synovitis tissue extract, were utilized as probes for the enzyme-labeled antigen method, in order to visualize the site of specific antibody production in synovial lesions. Specific antibodies against two proteins, tripartite motif-containing 21 (TRIM21, also known as SSA/Ro52) and F-box only protein 2 (FBXO2), were visualized in the cytoplasm of plasmacytes in two RA synovitis lesions, respectively. Absorption experiments using unlabeled proteins confirmed the specificity of staining. No positive signals against these two proteins were identified in the additionally evaluated RA and osteoarthritis synovial lesions. The present study indicated 1) the usefulness of screening the human autoantigen library with the AlphaScreen assay for detecting autoantibodies in RA synovitis, and 2) the applicability of biotinylated proteins to the enzyme-labeled antigen method for visualizing the site of autoantibody production within the lesion.

Coexpression of alpha6beta4 integrin and guanine nucleotide exchange factor Net1 identifies node-positive breast cancer patients at high risk for distant metastasis

Preclinical data indicate that alpha6beta4 integrin signaling through Ras homolog gene family, member A, plays an important role in tumor cell motility. The objective of this study was to determine whether the combined expression of alpha6beta4 integrin and neuroepithelioma transforming gene 1 (Net1), a guanine nucleotide exchange factor specific for Ras homolog gene family member A, is associated with adverse clinical outcome in breast cancer patients. Immunohistochemical expression of each protein was evaluated in a tumor tissue microarray prepared from the primary tumors of 94 node-positive patients with invasive breast carcinoma treated with total mastectomy and doxorubicin-based chemotherapy without radiation with a median follow-up of 12.5 years. Associations between staining results and multiple clinicopathologic variables were investigated. Although there was no significant association between alpha6beta4 integrin or Net1 expression and clinical outcome when each marker was considered individually, coexpression of alpha6beta4 and Net1 was associated with decreased distant metastasis-free survival (P = 0.030). In the subset of patients with hormone receptor-positive tumors, coexpression of alpha6beta4 and Net1 was associated with a decrease in distant metastasis-free and overall survival (P < 0.001 and P = 0.006, respectively). Although an association between human epidermal growth factor receptor 2 expression and coexpression of alpha6beta4 and Net1 (P = 0.008) was observed, coexpression of alpha6beta4 and Net1 (hazard ratio, 1.63; P = 0.02) and lymphovascular invasion (hazard ratio, 2.35; P = 0.02) were the only factors independently associated with the development of distant metastasis in multivariate analysis. These findings suggest that coexpression of alpha6beta4 integrin and Net1 could be a useful biomarker for aggressive disease in node-positive breast cancer patients.

Enzyme-labeled antigen method: histochemical detection of antigen-specific antibody-producing cells in tissue sections of rats immunized with horseradish peroxidase, ovalbumin, or keyhole limpet hemocyanin

The enzyme-labeled antigen method is a histochemical technique that visualizes antigen-specific antibody-producing cells in tissue sections, originally documented in 1968. In this study, we attempted to reemerge this hidden but potentially useful method in rat models immunized with horseradish peroxidase (HRP), ovalbumin (OA), or keyhole limpet hemocyanin (KLH). After repeated immunization in footpads, popliteal, groin, and axillary lymph nodes and spleen were sampled. Paraformaldehyde-prefixed frozen sections were incubated with HRP, biotinylated OA, or biotinylated KLH. Proteinase K pretreatment and the secondary use of HPR-labeled streptavidin were applied in the latter two situations. Plasma cells producing antigen-specific antibodies were visualized. Proportions of antigen-specific antibody-producing cells in total plasma cells shown with the immunoperoxidase method for rat immunoglobulins were evaluated. The percentage of antigen-specific plasma cells reached approximately 50% of total plasma cells in the regional lymph nodes. The specificity was confirmed by (a) negativity in non-immune rat tissue, (b) negativity with indifferent antigen probes, and (c) abolishment of the reactivity with the corresponding rat serum. In buffered formalin-fixed, paraffin-embedded tissues, fewer plasma cells were labeled for HRP and KLH antibody reactivity after strong proteolysis and prolonged incubation. Expectedly, this method allows us to observe antigen-specific antibody-producing cells under varied pathological conditions.

Flow cytometric immunphenotyping of epithelial cancer cells in effusions—Technical considerations and pitfalls

BACKGROUND

Data regarding the role of flow cytometry (FCM) in the characterization of malignant effusions are limited to date. In the present study, we optimized the conditions for FCM immunphenotyping of effusions using a four-color analysis and investigated aspects related to the advantages and limitations of this method in this setting.

METHODS

FCM analysis optimization for the study of epithelial cells was undertaken using five carcinoma cell lines, and subsequently applied to malignant pleural and peritoneal effusions using antibodies against epithelial and mesothelial markers (Ber-EP4 and EMA), CD138, and integrin subunits. FCM of frozen versus fresh specimens and the performance of FCM compared to immunhistochemistry were evaluated.

RESULTS

FCM optimization was achieved and applied to clinical specimens, with resulting detection of epithelial markers and adhesion molecules on cancer cells. Frozen clinical specimens and cell lines showed reduced CD138 expression compared to fresh specimens, with conservation of the remaining epitopes. FCM generally showed comparable performance to immunhistochemistry.

CONCLUSIONS

FCM is an effective method for characterization of cancer cells in clinical effusion specimens in both the diagnostic and research setting, and is comparable to immunhistochemistry in terms of sensitivity and specificity, with the additional advantage of providing quantitative data. The majority of epitopes are conserved in frozen cells, but a minority may be lost, suggesting that the thorough testing of each antibody in both conditions is mandatory.

Integrin characterization in pulmonary bronchioles

Integrins are a family of cell surface glycoproteins that act as receptors for ECM proteins or for membrane bound counter-receptors on other cells. The integrin receptor family of vertebrates includes at least 16 distinct alpha subunits and at least 8 beta subunits which can associate to form more than 20 distinct integrins. So far, there are no published reports describing integrin characterization in mouse lung tissue and mouse Clara cells. This paper described the characterization of six integrins, mainly alpha(5), alpha(v), alpha(6), beta(1), beta(3), and beta(4), in mouse pulmonary bronchioles and also in Clara cell cultures. alpha(5), alpha(v), alpha(6), beta(1), and beta(4) integrins were present in Clara cells both in tissue sections and cultures. beta(3) integrin was found to be absent in mouse Clara cells.

Quantitative analysis of integrin expression in effusions using flow cytometric immunophenotyping

We have previously shown that flow cytometric (FCM) immunophenotyping is a useful adjunct to morphology, in the diagnosis of serous effusions. The objective of the present study was to evaluate the possible application of FCM to quantitative analysis of adhesion molecule expression in this clinical setting. Fresh frozen cells from 67 effusions underwent quantitative analysis of alphaV, alpha6, beta1, and beta3 integrin subunit expression, using FCM. Specimens were diagnosed as carcinoma (n = 48), reactive (n = 12), or malignant mesothelioma (MM; n = 7) using morphology and, in selected cases, immunocytochemistry prior to FCM analysis. Antibodies against established epithelial, lymphoid, and mesothelial cell epitopes (Ber-EP4, anti-epithelial membrane antigen; (EMA), anti-CD45, anti-CD14, and anti-CD15) completed the panel. Results (percentage of cells expressing the antigen) were analyzed for relationship with the morphologic diagnosis. Frequent expression of the alphaV, alpha6, and beta1 subunits was seen in all diagnostic groups, with significantly higher expression of the alpha6 subunit in MM (P = 0.029, Kruskal-Wallis H test). The beta3 integrin subunit was not detected in any of the specimens. Ber-EP4 and CD15 expression was significantly higher in carcinomas compared with reactive effusions and MM (P < 0.001 and P = 0.001, Kruskal-Wallis H test), and EMA expression was higher in carcinomas and MM, compared with reactive specimens (P < 0.001, Kruskal-Wallis H test). In conclusion, FCM is an efficient tool for quantitative analysis of adhesion molecules in effusions. The high alpha6 integrin subunit expression in MM suggests involvement of this receptor in tumor attachment to laminin. The frequent expression of the alphaV and beta1 subunits support attachment to fibronectin and vitronectin as the major ECM ligands in body cavities.

Endometrial function in vervet monkeys (Cercopithecus aethiops): morphology, beta3 integrin and insulin-like growth factor binding protein-1 expression during the menstrual cycle and pregnancy in the normal and disrupted endometrium

The expression of endometrial beta3 integrin and insulin-like growth factor binding protein-1 (IGFBP-1) was studied in cycling and pregnant vervet monkeys. There were clear changes of beta3 integrin expression during the menstrual cycle, with the strongest immunostaining observed on day 26. Moderate to strong expression was observed during pregnancy. The expression of IGFBP-1 during the menstrual cycle was weak but upregulated during pregnancy with moderate to strong staining. The administration of a single dose of onapristone at 10 mg/kg on days 17, 21 and 22 of the menstrual cycle, followed by a biopsy on days 22, 22 and 26, respectively, and during pregnancy (34-44 days menstrual age) 24 h before the biopsy, disrupted and desynchronized the endometrium. However, no effect on beta3 integrin expression could be observed and staining reflected the untreated patterns. The same applied to IGFBP-1 except that during pregnancy the expression of this protein was reduced or abolished. The results suggest that beta3 integrin is associated with endometrial receptivity in vervet monkeys and that IGFBP-1 plays an important role during pregnancy in this species. The administration of onapristone appeared to only influence IGFBP-1 expression. To our knowledge, this is the first time that these endometrial proteins have been investigated in vervet monkeys. This study should therefore contribute to improving our understanding of the reproductive function of this species.