CD43 expression in a B cell lymphoma, WEHI 231, reduces susceptibility to G1 arrest and extends survival in culture upon serum depletion

SOX11 inhibits tumor proliferation and promotes cell adhesion mediated-drug resistance via a CD43 dependent manner in mantle cell lymphoma

SOX11 is a critical biomarker for mantle cell lymphoma (MCL) diagnosis; however, its role remains unclear in MCL. Here, clinical-pathological analysis showed Ki67 index was negatively relevant to SOX11 expression only in CD43 positive cases. Coexpression of SOX11/CD43 indicated longer overall survival. In vitro, knockout/overexpression of SOX11 or CD43 promoted/inhibited cell proliferation respectively. CD43 overexpression reversed tumor proliferation induced by SOX11 knockdown. Furthermore, overexpressing/silencing the SOX11/CD43 gene affects phosphorylation of p38-MAPK while p38 inhibitor reversed proliferation induced by si-SOX11 or si-CD43, respectively. In CAM-DR model, both SOX11 and CD43 in MCL cells were elevated when co-cultured with M2-10B4 bone marrow fibroblasts or fibronectin. Knockdown/overexpression of SOX11 decreased/increased cell adhesion, respectively, and the effect induced by silencing SOX11 was reversed by overexpression of CD43. Collectively, SOX11 could inhibit tumor proliferation and promote CAM-DR in a CD43 dependent manner.

Coexpression of CD5 and CD43 predicts worse prognosis in diffuse large B-cell lymphoma

Both CD5 and CD43 are expressed on the surface of B lymphocytes of definite phase and associated with the adverse outcome in diffuse large B-cell lymphoma (DLBCL). However, the relationship between CD5 and CD43 expression and the prognostic value of CD5/CD43 coexpression in DLBCL are unknown. We herein determined the correlation between CD5 and CD43 expression, as separate factors or in combination, with the clinicopathological features and survival of 200 patients with DLBCL receiving standard chemotherapy with or without rituximab. Among these DLBCL patients, CD5 expression, CD43 expression, and CD5/CD43 coexpression were detected in 18 (9%), 57 (27%), and 10 (5%) patients, respectively, and all were positively correlated with advanced age and nongerminal cell type. CD5-positive and CD43-positive DLBCL patients had poorer event-free survival (EFS, P < 0.001) and overall survival (OS, P < 0.001) than CD5-negative and CD43-negative patients, respectively. CD5/CD43 coexpression was correlated with a significantly worse prognosis than CD5 or CD43 expression alone. Univariate analysis showed that CD5 expression, CD43 expression, and CD5/CD43 coexpression were all adverse prognostic factors for DLBCL patient survival, and CD5/CD43 coexpression was associated with a greater relative risk for recurrence and death than either CD5 or CD43 expression alone. Multivariate analysis demonstrated that CD5/CD43 coexpression was an independent prognostic factor for EFS (P < 0.001) and OS (P < 0.001) in DLBCL. In conclusion, our data indicate that DLBCL patients with CD5/CD43 coexpression represent a specific subgroup with a significantly worse prognosis than those expressing either marker alone.

An alternative mode of CD43 signal transduction activates pro-survival pathways of T lymphocytes

CD43 is one of the most abundant co-stimulatory molecules on a T-cell surface; it transduces activation signals through its cytoplasmic domain, contributing to modulation of the outcome of T-cell responses. The aim of this study was to uncover new signalling pathways regulated by this sialomucin. Analysis of changes in protein abundance allowed us to identify pyruvate kinase isozyme M2 (PKM2), an enzyme of the glycolytic pathway, as an element potentially participating in the signalling cascade resulting from the engagement of CD43 and the T-cell receptor (TCR). We found that the glycolytic activity of this enzyme was not significantly increased in response to TCR+CD43 co-stimulation, but that PKM2 was tyrosine phosphorylated, suggesting that it was performing moonlight functions. We report that phosphorylation of both Y¹⁰⁵ of PKM2 and of Y⁷⁰⁵ of signal transducer and activator of transcription 3 was induced in response to TCR+CD43 co-stimulation, resulting in activation of the mitogen-activated protein kinase kinase 5/extracellular signal-regulated kinase 5 (MEK5/ERK5) pathway. ERK5 and the cAMP response element binding protein (CREB) were activated, and c-Myc and nuclear factor-κB (p65) nuclear localization, as well as Bad phosphorylation, were augmented. Consistent with this, expression of human CD43 in a murine T-cell hybridoma favoured cell survival. Altogether, our data highlight novel signalling pathways for the CD43 molecule in T lymphocytes, and underscore a role for CD43 in promoting cell survival through non-glycolytic functions of metabolic enzymes.

CD43 expression in diffuse large B-cell lymphoma, not otherwise specified: CD43 is a marker of adverse prognosis

CD43 (leukosialin) is a transmembrane glycoprotein expressed in a variety of hematopoietic cells, including B lymphocytes, and a variety of malignancies including lymphoma, leukemia, and solid tumors. CD43 plays an important role in the development of many diseases, and coexpression of CD43 and CD20 on peripheral B cells is a predictive factor of hematopoietic malignancy. Although CD43 is expressed in approximately 25% of diffuse large B-cell lymphomas (DLBCLs), its prognostic significance remains unclear. To analyze CD43 expression in DLBCL, not otherwise specified (DLBCL, NOS), and assess its prognostic value, we analyzed clinical data from 160 patients with DLBCL, NOS. We observed that CD43 expression was detected in 47 (29.4%) of 160 cases. CD43 expression was positively correlated with old age (>60 years), high serum lactate dehydrogenase level, B symptoms, non-germinal center type, and DLBCL, NOS, mortality. Patients with CD43-positive DLBCL, NOS, had poorer overall survival (P < .001, log-rank test) and event-free survival (P < .001, log-rank test) than CD43-negative patients. Univariate analysis showed that CD43 expression, age, sex, Ann Arbor stage, International Prognostic Index category, and germinal center phenotype were prognostic factors for DLBCL, NOS, patient survival. Multivariate analysis showed that CD43 expression was an independent significant prognostic factor for event-free survival (P < .001) and overall survival (P < .001). Based on these data, we conclude that CD43 expression is a novel adverse prognostic factor for patients with DLBCL, NOS.

CD43 expression is an adverse prognostic factor in diffuse large B-Cell lymphoma

BACKGROUND

CD43 is a transmembrane glycoprotein expressed in different hematopoietic cells, including some subsets of B lymphocytes. About a quarter of diffuse large B-cell lymphomas (DLBCLs) express CD43, but its prognostic significance is unknown.

PATIENTS AND METHODS

We analyzed the prognostic effect of immunohistochemically determined CD43 expression in 119 patients with newly diagnosed DLBCL. All were treated with CHOP (cyclophosphamide/doxorubicin/vincristine/prednisone)-like chemotherapy, 57 without and 62 with rituximab.

RESULTS

A total of 31 DLBCL cases (26%) expressed CD43. Patients with CD43+ and CD43- lymphomas did not differ regarding sex, International Prognostic Index (IPI) factors and score, rituximab treatment, presence of bulky disease, or germinal center subtype. Median follow-up was 45 months. Patients with CD43+ DLBCL had significantly lower complete response rates (59% vs. 80%; P = .019), 2-year event-free survival (EFS) rates (34% vs. 64%; P = .003), and overall survival (OS) rates (45% vs. 76%; P = .002). The prognostic significance of CD43 expression was retained in multivariate analysis (relative risk [RR] 2.04; P = .013 for EFS; RR 2.17; P = .016 for OS). In subgroup analysis, the effect of CD43 expression was significant in patients treated with rituximab and those with low IPI, whereas it was not reached in patients treated without rituximab. The effect was not observed in patients with high IPI.

CONCLUSION

These results indicate that CD43 expression is an important independent adverse prognostic factor in DLBCL.

CD43 promotes cell growth and helps to evade FAS-mediated apoptosis in non-hematopoietic cancer cells lacking the tumor suppressors p53 or ARF

CD43 is a highly glycosylated transmembrane protein expressed on the surface of most hematopoietic cells. Expression of CD43 has also been demonstrated in many human tumor tissues, including colon adenomas and carcinomas, but not in normal colon epithelium. The potential contribution of CD43 to tumor development is still not understood. Here, we show that overexpression of CD43 increases cell growth and colony formation in mouse and human cells lacking expression of either p53 or ARF (alternative reading frame) tumor-suppressor proteins. In addition, CD43 overexpression also lowers the detection of the FAS death receptor on the cell surface of human cancer cells, and thereby helps to evade FAS-mediated apoptosis. However, when both p53 and ARF proteins are present, CD43 overexpression activates p53 and suppresses colony formation due to induction of apoptosis. These observations suggest CD43 as a potential contributor to tumor development and the functional ARF-p53 pathway is required for the elimination of cells with aberrant CD43 expression.

Shedding and gamma-secretase-mediated intramembrane proteolysis of the mucin-type molecule CD43

CD43 is a transmembrane molecule that contains a 123-aminoacids-long cytoplasmic tail and a highly O-glycosylated extracellular domain of mucin type. Endogenous CD43 expressed in COLO 205, K562 and Jurkat cells revealed a membrane-associated, 20 kDa CD43-specific cytoplasmic tail fragment (CD43-CTF) upon inhibition of gamma-secretase. This fragment was formed by an extracellular cleavage, as it was not accumulated after treating cells with 1,10-phenanthroline, a metalloprotease inhibitor. When CD43 was transfected into HEK-293 cells expressing dominant-negative PS1 (presenilin-1), the CD43-CTF was accumulated, but not in cells with wild-type PS1. Owing to its accumulation in the presence of a non-functional PS variant, it may thus be a novel gamma-secretase substrate. This CTF is formed by an extracellular cleavage close to the membrane, is a fragment that can be concluded to be a substrate for gamma-secretase. However, the intracellular gamma-secretase product has not been possible to detect, suggesting a quick processing of this product. During normal growth the CTF was not found without gamma-secretase inhibition, but when the cells (COLO 205) were very confluent the fragment could be detected. The intracellular domain of CD43 has previously been shown to contain a functional nuclear localization signal, and has been suggested to be involved in gene activation. From this and the present results, a novel way to explain how mucin-type molecules may transduce intracellular signals can be proposed.

Differential expression of GL7 activation antigen on bone marrow B cell subpopulations and peripheral B cells

GL7 was originally described as a 35-kDa late activation antigen on mouse T and B cells. GL7 expression has also been demonstrated on thymocytes, germinal center B cells and some neuronal cell types. Flow-cytometry and immunohistochemistry were used to follow changes in the expression of GL7 during B cell development, amongst B cell subpopulations and various anatomical locations. GL7 is expressed as early as the pro-B cell stage and increases up to the pre-B-I stadium. Expression remains high on pre-B-II and on immature B cells, although slightly decreases during maturation. GL7 is almost completely downregulated when IgD appears on the cell surface. On the periphery only a few B cells are positive and these cells are almost exclusively found in the sIgD- germinal center areas of lymph nodes and spleen. The staining pattern of GL7 is very similar to that of PNA in the lymph nodes but in the bone marrow we have found both B220+PNA+GL7- and B220+PNA+GL7+ populations, showing that GL7 and the antigen recognized by PNA are different. After in vitro stimulation, the GL7(hi) B cell population has also been found to be IgD negative. Functional comparison between in vitro activated and MACS sorted GL7(hi) and GL7(lo/-) spleen B cells of immunized mice showed significantly higher specific and total antibody production as well as antigen presenting capacity in the GL7(hi) population.

Reduced CD43 expression on the neutrophils of MDS patients correlates with an activated phenotype of these cells

CD43 (also known as leukosialin and sialophorin) is a surface sialoglycoprotein expressed at high levels on most leukocytes implicated in adhesion, antiadhesion, and activation/proliferation mechanisms. We studied the expression of this molecule on the leukocytes of patients with myelodysplastic syndromes (MDSs) in an effort to detect acquired deficiencies of this molecule. We used immunofluorescence flow cytometry in analyzing whole blood and isolated neutrophils from 49 MDS patients, 33 men and 16 women aged 33 to 85 years (median, 75 years), and 18 healthy individuals aged 35 to 80 years (median, 72 years). According to French-American-British classification criteria, 13 patients had refractory anemia, 18 had refractory anemia with ringed sideroblasts, 9 had refractory anemia with excess of blasts, 4 had refractory anemia with excess of blasts in transformation to acute leukemia, and 5 had chronic myelomonocytic leukemia. We found decreased expression of CD43 on the neutrophils of these patients, and we correlated this finding with the activation status of these cells as it is defined by their phenotypes. We studied the expression of CD11b, CD18, CD35, CD67, CD69, CD44, and CD53 molecules known to be changed in the activated form of neutrophils. CD43 expression correlated positively with CD53 and CD44 expression and negatively with CD11b, CD18, CD35, CD67, and CD69 expression. Additionally, increased levels of soluble vascular cell adhesion molecules were detected in these patients, suggesting endothelial cell activation. In conclusion, we believe that the decreased expression of CD43 on the neutrophils of MDS patients is associated with activation of these cells and is probably due to cleavage of the molecule from the cell surface and that the same mechanism is possibly responsible for the parallel down-regulation of CD44 and CD53.

Antiadhesive function of 130-kd glycoform of CD43 expressed in CD4 T-lymphocyte clones and transfectant cell lines

Conflicting findings regarding proadhesion and antiadhesion in cell-to-cell interactions were previously reported for CD43. We examined possible differences in the role of the 130-kd glycoform and the 115-kd glycoform of CD43 in cellular adhesion in vitro. We generated a monoclonal antibody (MFT3) that discriminates between helper and nonhelper murine T-cell clones. Characterization of MFT3 with use of biochemical analysis and complementary DNA (cDNA) transfection experiments showed that it is specific for the 130-kd glycoform of CD43. T-cell clones that expressed the 130-kd CD43 glycoform showed decreased homocytic aggregation and decreased adhesion to spleen cells, B-lymphoma cell lines, and fibroblastic cell lines compared with T-cell clones negative for the 130-kd glycoform. Expression of core 2 β-1, 6-N-acetylglucosaminyltransferase (C2GnT) cDNA together with CD43 cDNA resulted in expression of both the 130-kd CD43 glycoform and the 115-kd CD43 glycoform in fibroblastic cell lines. Using these cell lines, we showed that the 130-kd glycoform but not the 115-kd glycoform of CD43 has an antiadhesive function in cellular interactions. Our findings suggest that the antiadhesive function of CD43 is primarily carried out by the 130-kd glycoform.

Antiadhesive function of 130-kd glycoform of CD43 expressed in CD4 T-lymphocyte clones and transfectant cell lines

Conflicting findings regarding proadhesion and antiadhesion in cell-to-cell interactions were previously reported for CD43. We examined possible differences in the role of the 130-kd glycoform and the 115-kd glycoform of CD43 in cellular adhesion in vitro. We generated a monoclonal antibody (MFT3) that discriminates between helper and nonhelper murine T-cell clones. Characterization of MFT3 with use of biochemical analysis and complementary DNA (cDNA) transfection experiments showed that it is specific for the 130-kd glycoform of CD43. T-cell clones that expressed the 130-kd CD43 glycoform showed decreased homocytic aggregation and decreased adhesion to spleen cells, B-lymphoma cell lines, and fibroblastic cell lines compared with T-cell clones negative for the 130-kd glycoform. Expression of core 2 β-1, 6-N-acetylglucosaminyltransferase (C2GnT) cDNA together with CD43 cDNA resulted in expression of both the 130-kd CD43 glycoform and the 115-kd CD43 glycoform in fibroblastic cell lines. Using these cell lines, we showed that the 130-kd glycoform but not the 115-kd glycoform of CD43 has an antiadhesive function in cellular interactions. Our findings suggest that the antiadhesive function of CD43 is primarily carried out by the 130-kd glycoform.

Antigen-specific B cell memory: expression and replenishment of a novel b220(-) memory b cell compartment

The mechanisms that regulate B cell memory and the rapid recall response to antigen remain poorly defined. This study focuses on the rapid expression of B cell memory upon antigen recall in vivo, and the replenishment of quiescent B cell memory that follows. Based on expression of CD138 and B220, we reveal a unique and major subtype of antigen-specific memory B cells (B220(-)CD138(-)) that are distinct from antibody-secreting B cells (B220(+/)-CD138(+)) and B220(+)CD138(-) memory B cells. These nonsecreting somatically mutated B220(-) memory responders rapidly dominate the splenic response and comprise >95% of antigen-specific memory B cells that migrate to the bone marrow. By day 42 after recall, the predominant quiescent memory B cell population in the spleen (75-85%) and the bone marrow (>95%) expresses the B220(-) phenotype. Upon adoptive transfer, B220(-) memory B cells proliferate to a lesser degree but produce greater amounts of antibody than their B220(+) counterparts. The pattern of cellular differentiation after transfer indicates that B220(-) memory B cells act as stable self-replenishing intermediates that arise from B220(+) memory B cells and produce antibody-secreting cells on rechallenge with antigen. Cell surface phenotype and Ig isotype expression divide the B220(-) compartment into two main subsets with distinct patterns of integrin and coreceptor expression. Thus, we identify new cellular components of B cell memory and propose a model for long-term protective immunity that is regulated by a complex balance of committed memory B cells with subspecialized immune function.

Downregulation of CD43 in RAEB and RAEB-T patients. Report of 3 cases

CD43 (leukosialin, sialophorin) is a cell surface mucin expressed at high levels on most leukocytes and is reported to be involved in adhesion, anti-adhesion, and signal transduction prodders. Regulation of its expression is thought to take place through methylation of the DNA in the nonproducing cells, and the methylation inhibitor 5-azacytidine induces expression of the sialophorin gene. Here we report three cases of patients with myelodysplastic syndromes in which acquired severe deficiency of the CD43 antigen on the surface of most hemopoietic cells was observed. Peripheral blood mononuclear (PBMC) cells from 32 MDS patients and 20 healthy individuals were analyzed by flow cytometry after labeling with an anti-CD43 (DF-T1) monoclonal antibody. In 1 patient with refractory anemia with excess of blasts (RAEB) and 2 patients with refractory anemia with excess of blasts in transformation (RAEB-t), the percentages of CD43(+) PBMC were 3.8%, 6%, and 9.9%, respectively. The deficiency was observed at protein and RNA level as confirmed by western and southern blot, while analysis of the DNA by single-strand conformation polymorphism and sequencing did not reveal any difference in the gene sequence between the CD43(+) and CD43(-) cells of these patients. It is known that patients with MDS may have normal and dysplastic population of hemopoietic cells. Further studies are needed to reveal the mechanism of downregulation of the gene in these 3 patients and whether the phenomenon is related to the dysplastic population only or not.

High level expression of CD43 inhibits T cell receptor/CD3-mediated apoptosis

In a screen designed to identify genes that regulate T cell receptor (TCR)/CD3-mediated apoptosis, we found that high level expression of CD43 protected T cell hybridomas from activation-induced cell death. The protection appears to result from its capacity to block Fas-mediated death signals rather than from inhibition of the upregulation of Fas and/or Fas ligand after T cell stimulation. We found that peripheral CD4(+) T cells can be divided into two subsets based on the level of CD43 surface expression. The CD4(+)CD43(low) subset exhibits a naive T cell phenotype, being CD62L(high)CD45RB(high)CD44(low), whereas CD4(+)CD43(high) cells exhibit a memory phenotype, being CD62L(low)CD45RB(low)CD44(high). Recent studies have demonstrated that engagement of TCR and Fas induces naive CD4(+) T cells to undergo apoptosis, and the same treatment enhances the proliferation of memory CD4(+) T cells. We confirm here that peripheral CD4(+)CD43(high) T cells are resistant to TCR/CD3-mediated cell death. These results suggest that the expression levels of CD43 on naive and memory CD4(+) T cells determine their susceptibility to Fas-dependent cell death and that high level expression of CD43 may be used as a marker to define CD4(+) memory T cells. Expression of CD43 provides a novel mechanism by which tumor cells expressing abnormally high levels of CD43 may escape Fas-mediated killing.

CD43, a molecule with multiple functions

To initiate a specific immune response, lymphoid cells integrate a variety of signals generated through the orchestrated interaction of multiple cell surface molecules with their counter-receptors. As a result of the specific recognition of the antigen through antigen-specific receptors, and of the monitoring of their particular environment through the so-called coreceptor molecules, lymphoid cells go through elaborate processes of maturation and activation, contributing to the plasticity and sensitivity of immune response. CD43 is the major sialic acid rich protein on the surface of lymphocytes. However, the specific roles of this protein in different lymphoid cells under normal physiological conditions remain largely unknown. In this review we will mainly focus on the recent advances concerning the functions of this molecule as a coreceptor of different lymphoid cells as well as on the participation of this molecule in different pathologies.

Establishment of MAIDS-defective virus-infected B cell lines and their characterization

Mice inoculated with the murine AIDS (MAIDS)-defective virus develop severe B and T cell dysfunctions. The primary event in the development of this disease is the infection and polyclonal expansion of the target cells of this defective virus, which have been reported to belong to the B cell lineage. To further study the central role that these cells play in the development of MAIDS, we attempted to establish MAIDS-defective virus-infected B cell lines in vitro. We succeeded in establishing two cell lines, SD1 and CSTB5, from the enlarged organs of C57BL/6 mice inoculated with helper-free stocks of the MAIDS-defective virus. Both cell lines are not transplantable in syngeneic C57BL/6 mice or in nude or CD8-/- mice and are apparently not malignant. They both belong to the B lineage, as their immunoglobulin (Ig) genes, but not the T cell receptor (TcR) beta locus, are rearranged, suggesting that they are relatively mature B cells. However, analysis of cell surface marker expression by FACS revealed a surface phenotype similar to that of pre-B cells (MHC I+, MHC II+, B7.2+, sIgM-, sIgG-, kappa-, B220-, CD5-, Thy1.2-, TcR-, CD3-, CD4-, CD8-, Mac-1-, 33D1-). Additionally, the CSTB5 cells express CD40 and the SD1 cells express CD43. Both cell lines contain the MAIDS-defective provirus and express the expected 4.2-kb viral RNA and the corresponding Pr60gag protein. The CSTB5 cells are nonproducer, while the SD1 cell line produces what appears to be an endogenous MuLV. The phenotype of these cell lines is very similar to what is known about the target B cells of this virus in vivo. These new established cell lines are likely to be useful in elucidating the mechanism(s) by which the MAIDS-defective virus causes its target B cells to proliferate and induce T cell anergy in infected animals.