Apical Membrane Expression of Distinct Sulfated Glycans Is a Characteristic Feature of Ductules and Their Reactive and Neoplastic Counterparts

Structural Elucidation and Prognostic Relevance of 297-11A-Sulfated Glycans in Ovarian Carcinoma

Ovarian carcinoma is usually diagnosed at an advanced stage with peritoneal dissemination and/or lymph node metastasis, and the prognosis for such advanced carcinoma is very poor. Therefore, new biomarkers to predict patient prognosis are needed. Miyamoto et al. previously showed that keratan sulfate (KS) detected by the 5D4 monoclonal antibody was expressed in ovarian carcinoma. However, the detailed structure of such KS was not determined, and the biological significance of this finding remained to be clarified. We previously generated the 297-11A monoclonal antibody, which recognizes galactose (Gal)-6-O-sulfated N-acetyllactosamine (LacNAc) located at the nonreducing terminus. Because the 297-11A epitope overlaps with that of 5D4, here we chose to use the 297-11A antibody as a tool to analyze KS and related structures. We conducted immunohistochemical analysis of 98 ovarian carcinoma cases with 297-11A antibody combined with a series of glycosidases and performed mass spectrometry analysis of the human serous ovarian carcinoma cell line OVCAR-3 to deduce the glycan structure of 297-11A-sulfated glycans. We also performed western blot analysis to assess a potential association of 297-11A-sulfated glycans with the mucin core protein mucin 16 (MUC16; also known as cancer antigen 125 (CA125)). Finally, we examined the relationship between 297-11A expression and patient prognosis. Consequently, 297-11A-sulfated glycans were primarily expressed in serous and endometrioid carcinomas and poorly expressed in mucinous and clear cell carcinomas. We reveal that structurally, 297-11A-sulfated glycans expressed in ovarian carcinoma are O-glycans carrying partially sialylated, Gal-6-O-sulfated LacNAc and that these glycans are likely displayed on MUC16 mucin core proteins. Of clinical importance is that expression of 297-11A-sulfated glycans correlated with shorter progression-free survival in patients. Thus, 297-11A-sulfated glycans may serve as a predictor of ovarian carcinoma recurrence.

Expression of low-sulfated keratan sulfate in non-mucinous ovarian carcinoma

Keratan sulfate glycosaminoglycan is composed of repeating N-acetyllactosamine (LacNAc) disaccharide units consisting of galactose (Gal) and N-acetylglucosamine (GlcNAc), both often 6-O-sulfated. Sulfate contents of keratan sulfate are heterogeneous depending upon the origins. In this study, keratan sulfate is classified as either highly sulfated (in which both GlcNAc and Gal residues are 6-O-sulfated) or low-sulfated (in which only GlcNAc residues are 6-O-sulfated). It is reported that highly sulfated keratan sulfate detected by the 5D4 monoclonal antibody is preferentially expressed in normal epithelial cells lining the female genital tract and in their neoplastic counterparts; however, expression of low-sulfated keratan sulfate in either has not been characterized. In the present study, we generated the 294-1B1 monoclonal antibody, which selectively recognizes low-sulfated keratan sulfate, and performed precise glycan analysis of sulfated glycans expressed on human serous ovarian carcinoma OVCAR-3 cells. We found that OVCAR-3 cells do not express highly sulfated keratan sulfate but rather express low-sulfated form, which was heterogeneous in 294-1B1 reactivity. Comparison of mass spectrometry spectra of sulfated glycans in 294-1B1-positive versus -negative OVCAR-3 cells indicated that the 294-1B1 epitope is likely at least 2, and possibly 3 or more, tandem GlcNAc-6-O-sulfated LacNAc units. Then, using the 294-1B1 antibody, we performed quantitative immunohistochemical analysis of 40 specimens from patients with ovarian cancer, consisting of 10 each of serous, endometrioid, clear cell, and mucinous carcinomas, and found that among them low-sulfated keratan sulfate was widely expressed in all but mucinous ovarian carcinoma.

Paradoxical Expression of R-10G-reactive Antigen in Human Testicular Embryonal Carcinoma

Thus far, several monoclonal antibodies directed against cell-surface carbohydrate antigens have been generated. Among them, R-10G reportedly reacts selectively with human embryonic stem and induced pluripotent stem cells, but not with embryonal carcinoma (EC) cells. However, EC cells derived from patients' EC tumors may exhibit varying levels of R-10G-reactive antigen expression. Thus, we asked whether human EC tissues or germ cell tumor (GCT) tissues other than EC express R-10G-reactive antigen. To do so, we quantitatively analyzed R-10G-reactive antigen expression in 83 testicular GCT surgical specimens containing a total of 125 various GCT components. Accordingly, in all EC components examined, the EC cell plasma membrane was immunolabeled with R-10G, while most seminoma components were R-10G-negative. In non-seminomatous GCT (NSGCT) other than EC (non-EC NSGCT), R-10G-reactive antigen expression was variable, but signal distribution was focal, and the average intensity was weaker than that seen in EC. The percentages of R-10G-positive cells in these three groups varied with high statistical significance (p<0.001 for all combinations). These findings indicate that the R-10G-reactive antigen is preferentially expressed in human testicular EC tissues and, thus, could be used as a diagnostic marker for this malignancy.

Expression and Clinical Significance of Spi-B in B-cell Acute Lymphoblastic Leukemia

Spi-B, a member of the E26 transformation-specific (ETS) family of transcription factors, plays an important role in B cell differentiation. Spi-B also functions in development of diffuse large B-cell lymphoma; thus, we hypothesized that it may participate in leukemogenesis of B-cell acute lymphoblastic leukemia (B-ALL). To test this hypothesis, we first generated an anti-Spi-B monoclonal antibody that recognized Spi-B on formalin-fixed, paraffin-embedded tissue sections. This antibody, designated S28-5, selectively stained B cell nuclei at the pre-plasma cell stage (including centrocytes and centroblasts in germinal centers) and nuclei of plasmacytoid dendritic cells, but not fully differentiated plasma cells, T cells, macrophages, or follicular dendritic cells. Employing S28-5, we then performed immunohistochemical staining of bone marrow aspiration biopsy specimens obtained from B-ALL patients (n=62). Cases that showed stronger nuclear S28-5 signals than T-cell ALL were scored positive. In 26 (42%) of 62 specimens, leukemic cells showed nuclear Spi-B expression, and positivity was associated with patient age at diagnosis, and serum uric acid and creatinine levels. Moreover, Spi-B-positive patients demonstrated significantly shorter overall survival than did Spi-B-negative patients. These results suggest that Spi-B expression may serve as a prognostic indicator of B-ALL.

The Percentage of PNAd-Expressing Vessels is Correlated with Disease Severity in Eosinophilic Chronic Rhinosinusitis

BACKGROUND

Eosinophilic chronic rhinosinusitis (ECRS) is a chronic inflammatory condition of the paranasal sinuses characterized by intractable nasal polyps with prominent eosinophil infiltration. These eosinophils are presumably recruited from peripheral blood via vessels expressing peripheral lymph node addressin (PNAd), a set of glycoproteins decorated with 6-sulfo sialyl Lewis x (sLe^x) glycans that serve as L-selectin ligands. Based on the severity classification algorithm proposed by the Japanese Epidemiological Survey of Refractory Eosinophilic Chronic Rhinosinusitis (JESREC) study group, ECRS is divided into mild, moderate and severe groups; however, as yet there are few reports comparing the clinicopathological differences among these groups.

OBJECTIVE

Our goal was to elucidate clinicopathological differences among the three different severities of ECRS with special reference to eosinophils and PNAd-expressing vessels.

METHODS

We performed quantitative immunohistochemical analysis of PNAd-expressing vessels using surgical specimens of nasal polyps from patients exhibiting varying severity of ECRS (n = 35) and from individuals with non-ECRS (n = 10). To this end, we immunostained tissue sections with anti-PNAd and anti-CD34 monoclonal antibodies, and then determined the number of vessels immunolabeled with each antibody.

RESULTS

The number of eosinophils infiltrating nasal polyps was correlated with ECRS severity. We also found that the PNAd + /CD34 + vessel ratio, namely, the percentage of PNAd-expressing vessels among all vessels, was positively correlated not only with ECRS severity but also with the number of eosinophils infiltrating nasal polyps formed in ECRS.

CONCLUSION

These results strongly suggest that PNAd-expressing vessels play at least a partial role in eosinophil recruitment to nasal polyps and consequent severity of ECRS.

Sulfated Glycans Recognized by S1 Monoclonal Antibody can Serve as a Diagnostic Marker for Malignant Pleural Mesothelioma

PURPOSE

Malignant pleural mesothelioma (MPM) is a malignant neoplasm of the pleura caused by asbestos exposure. For diagnosis of MPM, immunohistochemistry using multiple markers is recommended to rule out differential diagnoses, such as pulmonary adenocarcinoma. However, the specificity of currently used markers is not fully satisfactory. We previously developed a monoclonal antibody named S1, which recognizes 6-sulfo sialyl Lewis x, an L-selectin ligand expressed on high endothelial venules. During the screening process, we discovered that this antibody stained normal pleural mesothelium. This finding prompted us to hypothesize that the epitope recognized by S1 might serve as a new diagnostic marker for MPM.

METHODS

To test this hypothesis, we immunostained human MPM (n = 22) and lung adenocarcinoma (n = 25) tissues using S1 antibody.

RESULTS

77.3% of MPM were S1 positive, and if limited to epithelioid type, the positivity rate was 100%, while that of lung adenocarcinoma was only 36.0%. Statistical analysis revealed a significant difference in the S1 positivity rate between each disease. Furthermore, immunohistochemistry using a series of anti-carbohydrate antibodies combined with glycosidase digestion revealed the structure of sulfated glycans expressed in MPM to be 6-sulfo sialyl N-acetyllactosamine attached to core 2-branched O-glycans.

CONCLUSION

We propose that the S1 glycoepitope could serve as a new diagnostic marker for MPM.