CD24, a signal-transducing molecule expressed on human B lymphocytes, is a marker for human regenerating muscle

CD24 blockade as a novel strategy for cancer treatment

The CD24 protein is a heat-stable protein with a small core that undergoes extensive glycosylation. It is expressed on the surface of various normal cells, including lymphocytes, epithelial cells, and inflammatory cells. CD24 exerts its function by binding to different ligands. Numerous studies have demonstrated the close association of CD24 with tumor occurrence and progression. CD24 not only facilitates tumor cell proliferation, metastasis, and immune evasion but also plays a role in tumor initiation, thus, serving as a marker on the surface of cancer stem cells (CSCs). Additionally, CD24 induces drug resistance in various tumor cells following chemotherapy. To counteract the tumor-promoting effects of CD24, several treatment strategies targeting CD24 have been explored, such as the use of CD24 monoclonal antibodies (mAb) alone, the combination of CD24 and chemotoxic drugs, or the combination of these drugs with other targeted immunotherapeutic techniques. Regardless of the approach, targeting CD24 has demonstrated significant anti-tumor effects. Therefore, the present study focuses on anti-tumor therapy and provides a comprehensive review of the structure and fundamental physiological function of CD24 and its impact on tumor development, and suggests that targeting CD24 may represent an effective strategy for treating malignant tumors.

Stem Cell Growth and Differentiation in Organ Culture: New Insights for Uterine Fibroid Treatment

Organ culture allows for the understanding of normal and tumor cell biology, and tissues generally remain viable for 5–7 days. Strikingly, we determined that myometrial and MED12 mutant leiomyoma cells repopulated cell-depleted tissue slices after 20 days of culture. Using immunofluorescence and quantitative PCR of stem cell and undifferentiated cell markers, we observed clusters of CD49b⁺ cells in tumor slices. CD49b⁺ cells, however, were sparsely detected in the myometrial slices. Almost all LM cells strongly expressed Ki67, while only a few myometrial cells were stained for this proliferation marker. The CD73 marker was expressed only in tumor cells, whereas the mesenchymal stem cell receptor KIT was detected only in normal cells. HMGA2 and CD24 showed broader expression patterns and higher signal intensity in leiomyoma than in myometrial cells. In this study, we propose that activating CD49b⁺ stem cells in myometrium leads to asymmetrical division, giving rise to transit-amplifying KIT⁺ cells that differentiate to smooth muscle cells. On the contrary, activated leiomyoma CD49b⁺ cells symmetrically divide to form clusters of stem cells that divide and differentiate to smooth muscle cells without losing proliferation ability. In conclusion, normal and mutant stem cells can proliferate and differentiate in long-term organ culture, constituting a helpful platform for novel therapeutic discovery.

Macrophage targeting in cancer

Tumorigenesis is not only determined by the intrinsic properties of cancer cells but also by their interactions with components of the tumor microenvironment (TME). Tumor-associated macrophages (TAMs) are among the most abundant immune cells in the TME. During initial stages of tumor development, macrophages can either directly promote antitumor responses by killing tumor cells or indirectly recruit and activate other immune cells. As genetic changes occur within the tumor or T helper 2 (TH 2) cells begin to dominate the TME, TAMs begin to exhibit an immunosuppressive protumor phenotype that promotes tumor progression, metastasis, and resistance to therapy. Thus, targeting TAMs has emerged as a strategy for cancer therapy. To date, TAM targeting strategies have focused on macrophage depletion and inhibition of their recruitment into the TME. However, these strategies have shown limited therapeutic efficacy, although trials are still underway with combination therapies. The fact that macrophages have the potential for antitumor activity has moved the TAM targeting field toward the development of TAM-reprogramming strategies to support this antitumor immune response. Here, we discuss the various roles of TAMs in cancer therapy and their immunosuppressive properties, as well as implications for emerging checkpoint inhibitor-based immunotherapies. We review state-of-the-art TAM-targeting strategies, focusing on current ones at the preclinical and clinical trial stages that aim to reprogram TAMs as an oncological therapy.

CD24, A Review of its Role in Tumor Diagnosis, Progression and Therapy

CD24, is a mucin-like GPI-anchored molecules. By immunohistochemistry, it is widely detected in many solid tumors, such as breast cancers, genital system cancers, digestive system cancers, neural system cancers and so on. The functional roles of CD24 are either fulfilled by combination with ligands or participate in signal transduction, which mediate the initiation and progression of neoplasms. However, the character of CD24 remains to be intriguing because there are still opposite voices about the impact of CD24 on tumors. In preclinical studies, CD24 target therapies, including monoclonal antibodies, target silencing by RNA interference and immunotherapy, have shown us brighten futures on the anti-tumor application. Nevertheless, evidences based on clinical studies are urgently needed. Here, with expectancy to spark new ideas, we summarize the relevant studies about CD24 from a tumor perspective.

Coding Cell Identity of Human Skeletal Muscle Progenitor Cells Using Cell Surface Markers: Current Status and Remaining Challenges for Characterization and Isolation

Skeletal muscle progenitor cells (SMPCs), also called myogenic progenitors, have been studied extensively in recent years because of their promising therapeutic potential to preserve and recover skeletal muscle mass and function in patients with cachexia, sarcopenia, and neuromuscular diseases. SMPCs can be utilized to investigate the mechanisms of natural and pathological myogenesis via in vitro modeling and in vivo experimentation. While various types of SMPCs are currently available from several sources, human pluripotent stem cells (PSCs) offer an efficient and cost-effective method to derive SMPCs. As human PSC-derived cells often display varying heterogeneity in cell types, cell enrichment using cell surface markers remains a critical step in current procedures to establish a pure population of SMPCs. Here we summarize the cell surface markers currently being used to detect human SMPCs, describing their potential application for characterizing, identifying and isolating human PSC-derived SMPCs. To date, several positive and negative markers have been used to enrich human SMPCs from differentiated PSCs by cell sorting. A careful analysis of current findings can broaden our understanding and reveal potential uses for these surface markers with SMPCs.

Spatiotemporal analysis of putative notochordal cell markers reveals CD24 and keratins 8, 18, and 19 as notochord-specific markers during early human intervertebral disc development

In humans, the nucleus pulposus (NP) is composed of large vacuolated notochordal cells in the fetus but, soon after birth, becomes populated by smaller, chondrocyte-like cells. Although animal studies indicate that notochord-derived cells persist in the adult NP, the ontogeny of the adult human NP cell population is still unclear. As such, identification of unique notochordal markers is required. This study was conducted to determine the spatiotemporal expression of putative human notochordal markers to aid in the elucidation of the ontogeny of adult human NP cells. Human embryos and fetuses (3.5-18 weeks post-conception (WPC)) were microdissected to isolate the spine anlagens (notochord and somites/sclerotome). Morphology of the developing IVD was assessed using hematoxylin and eosin. Expression of keratin (KRT) 8, KRT18, KRT19, CD24, GAL3, CD55, BASP1, CTGF, T, CD90, Tie2, and E-cadherin was assessed using immunohistochemistry. KRT8, KRT18, KRT19 were uniquely expressed by notochordal cells at all spine levels at all stages studied; CD24 was expressed at all stages except 3.5 WPC. While GAL3, CD55, BASP1, CTGF, and T were expressed by notochordal cells at specific stages, they were also co-expressed by sclerotomal cells. CD90, Tie2, and E-cadherin expression was not detectable in developing human spine cells at any stage. This study has identified, for the first time, the consistent expression of KRT8, KRT18, KRT19, and CD24 as human notochord-specific markers during early IVD development. Thus, we propose that these markers can be used to help ascertain the ontogeny of adult human NP cells. © 2016 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. J Orthop Res 34:1327-1340, 2016.

CD24 gene polymorphism--a novel prognostic factor in esophageal cancer

BACKGROUND

The CD24 gene has been correlated with poor prognosis of various malignancies. The significance of CD24 in esophageal cancer remains unknown. Our aim was to evaluate the association between CD24 genetic polymorphism and esophageal cancer.

MATERIALS AND METHODS

Between June 2011 and May 2012 patients with esophageal cancer and healthy controls were prospectively enrolled and clinicopathological data were collected. Genomic DNA was extracted and restriction fragment length polymorphism (RFLP) analysis was performed to determine CD24 polymorphism at the coding region of CD24, which results in a substitution of the amino acid Ala by Val. Statistical significance was determined by unpaired t-test, χ²-test, and Fisher's exact test.

RESULTS

A total of 102 patients were included, of whom 51 had esophageal cancer and the rest comprised a healthy control group. The incidence of the polymorphism variant (Val/Val) among the healthy subjects and the esophageal cancer cohort was 6% in both groups. The incidence of N3 (metastasis in 7 or more regional lymph nodes) was markedly higher in those esophageal cancer patients who carried the polymorphism variant compared with those who did not carry it (66% and 2%, respectively, p=0.007). No significant difference was found between the groups with regard to age, gender, histology type, tumor location, tumor stage, and other histological characteristics of the tumor.

CONCLUSIONS

This CD24 polymorphism may serve as a novel prognostic marker identifying esophageal cancer patients with poor prognosis. Further studies are warranted to evaluate CD24 function and to validate its predictive potential with regard to esophageal cancer.

The CD24hi smooth muscle subpopulation is the predominant fraction in uterine fibroids

Uterine fibroids are the most common gynecological tumors affecting women in their reproductive age. Despite this high incidence the pathogenesis of fibroids is widely unsolved. Whereas formerly only imbalances in hormonal levels were considered to account for tumor development, the identification of genetic changes likely to affect myometrial stem cell reservoirs provided a novel approach to fibroid genesis. Here, we identified a certain subset of cells by the surface marker CD24 with increased abundance in fibroids compared with myometrial tissue. Fibroid cells expressing CD24 shared certain features of immature or progenitor-like cells such as quiescence, reduced expression of smooth muscle differentiation markers and elevated expression of genes involved in the wingless-type (WNT)-pathway such as beta-catenin. In addition, a positive correlation between CD24 and wingless-type family member 4 (WNT4) expression was observed in uterine fibroids with mediator subcomplex 12 gene (MED12) mutations. Our findings suggest that cells highly expressing CD24 represent a type of immature smooth muscle progenitor cells. Their accumulation might be driven by disturbed differentiation processes caused by genetic changes possibly involving MED12 mutations or high mobility group AT-hook (HMGA)2 rearrangements.

Expression of CD24, p21, p53, and c-myc in alpha-fetoprotein-producing gastric cancer: Correlation with clinicopathologic characteristics and survival

BACKGROUND AND OBJECTIVE

The aim of this study was to evaluate the expression of CD24, p21, p53, and c-myc in lesions of patients with Alpha-Fetoprotein (AFP)-producing gastric cancer and their correlation with clinicopathological features and prognosis.

METHODS

One hundred and four patients with AFP-producing gastric cancer were included into this study. The levels of CD24, p21, p53, and c-myc were examined by immunohistochemistry.The prognostic value of these biological markers and the correlation between biological markers and clinicopathological factors were investigated.

RESULTS

The percentages of positive expression of CD24, p21, p53, and c-myc were 31.7%, 77.9%, 75.0%, and 66.3%, respectively. CD24 expression correlated with histological grade (P = 0.045) and Lauren type (P = 0.006); p21expression with Borrmann type (P = 0.035); c-myc expression with Borrmann type (P = 0.029). p21 expression was related with poor survival in univariate analysis (P = 0.016). Multivariate analysis showed that p21 expression, vascular invasion, and pathological stage were defined as independent prognostic factors.

CONCLUSION

The expression of p21 was an independent prognostic factor for patients with AFP-producing gastric cancer.

Proximal tubular cells contain a phenotypically distinct, scattered cell population involved in tubular regeneration

Regeneration of injured tubular cells occurs after acute tubular necrosis primarily from intrinsic renal cells. This may occur from a pre-existing intratubular stem/progenitor cell population or from any surviving proximal tubular cell. In this study, we characterize a CD24-, CD133-, and vimentin-positive subpopulation of cells scattered throughout the proximal tubule in normal human kidney. Compared to adjacent 'normal' proximal tubular cells, these CD24-positive cells contained less cytoplasm, fewer mitochondria, and no brush border. In addition, 49 marker proteins are described that are expressed within the proximal tubules in a similar scattered pattern. For eight of these markers, we confirmed co-localization with CD24. In human biopsies of patients with acute tubular necrosis (ATN), the number of CD24-positive tubular cells was increased. In both normal human kidneys and the ATN biopsies, around 85% of proliferating cells were CD24-positive - indicating that this cell population participates in tubular regeneration. In healthy rat kidneys, the novel cell subpopulation was absent. However, upon unilateral ureteral obstruction (UUO), the novel cell population was detected in significant amounts in the injured kidney. In summary, in human renal biopsies, the CD24-positive cells represent tubular cells with a deviant phenotype, characterized by a distinct morphology and marker expression. After acute tubular injury, these cells become more numerous. In healthy rat kidneys, these cells are not detectable, whereas after UUO, they appeared de novo - arguing against the notion that these cells represent a pre-existing progenitor cell population. Our data indicate rather that these cells represent transiently dedifferentiated tubular cells involved in regeneration.

A critical re-evaluation of CD24-positivity of human embryonic stem cells differentiated into pancreatic progenitors

Differentiation of embryonic stem cells (ESCs) into insulin-producing cells for cell replacement therapy of diabetes mellitus comprises the stepwise recapitulation of in vivo developmental stages of pancreatic organogenesis in an in vitro differentiation protocol. The chemical compounds IDE-1 and (-)-indolactam-V can be used to direct mouse and human ESCs through these stages to form definitive endoderm via an intermediate mesendodermal stage and finally into pancreatic endoderm. Cells of the pancreatic endoderm express the PDX1 transcription factor and contribute to all pancreatic cell types upon further in vitro or in vivo differentiation. Even though this differentiation approach is highly effective and reproducible, it generates heterogeneous populations containing PDX1-expressing pancreatic progenitors amongst other cell types. Thus, a technique to separate PDX1-expressing cells from this mixture is very desirable. Recently it has been reported that PDX1-positive pancreatic progenitors, derived from human embryonic stem cells, express the surface marker CD24. Therefore were subjected mouse and human ESCs to a small molecule differentiation approach and the expression of the surface marker CD24 was monitored in undifferentiated cells, cells committed to the definitive endoderm and cells reminiscent of the pancreatic endoderm. We observed that both mouse and human ESCs expressed CD24 in the pluripotent state, during the whole process of endoderm formation and upon further differentiation towards pancreatic endoderm. Thus CD24 is not a suitable cell surface marker for identification of PDX1-positive progenitor cells.

A simple method to obtain pure cultures of multiciliated ependymal cells from adult rodents

Ependymal cells form an epithelium lining the ventricular cavities of the vertebrate brain. Numerous methods to obtain primary culture ependymal cells have been developed. Most of them use foetal or neonatal rat brain and the few that utilize adult brain hardly achieve purity. Here, we describe a simple and novel method to obtain a pure non-adherent ependymal cell culture from explants of the striatal and septal walls of the lateral ventricles. The combination of a low incubation temperature followed by a gentle enzymatic digestion allows the detachment of most of the ependymal cells from the ventricular wall in a period of 6 h. Along with ependymal cells, a low percentage (less than 6 %) of non-ependymal cells also detaches. However, they do not survive under two restrictive culture conditions: (1) a simple medium (alpha-MEM with glucose) without any supplement; and (2) a low density of 1 cell/µl. This purification method strategy does not require cell labelling with antibodies and cell sorting, which makes it a simpler and cheaper procedure than other methods previously described. After a period of 48 h, only ependymal cells survive such conditions, revealing the remarkable survival capacity of ependymal cells. Ependymal cells can be maintained in culture for up to 7-10 days, with the best survival rates obtained in Neurobasal supplemented with B27 among the tested media. After 7 days in culture, ependymal cells lose most of the cilia and therefore the mobility, while acquiring radial glial cell markers (GFAP, BLBP, GLAST). This interesting fact might indicate a reprogramming of the cell identity.

Transcriptional profiling of bovine milk using RNA sequencing

BACKGROUND

Cow milk is a complex bioactive fluid consumed by humans beyond infancy. Even though the chemical and physical properties of cow milk are well characterized, very limited research has been done on characterizing the milk transcriptome. This study performs a comprehensive expression profiling of genes expressed in milk somatic cells of transition (day 15), peak (day 90) and late (day 250) lactation Holstein cows by RNA sequencing. Milk samples were collected from Holstein cows at 15, 90 and 250 days of lactation, and RNA was extracted from the pelleted milk cells. Gene expression analysis was conducted by Illumina RNA sequencing. Sequence reads were assembled and analyzed in CLC Genomics Workbench. Gene Ontology (GO) and pathway analysis were performed using the Blast2GO program and GeneGo application of MetaCore program.

RESULTS

A total of 16,892 genes were expressed in transition lactation, 19,094 genes were expressed in peak lactation and 18,070 genes were expressed in late lactation. Regardless of the lactation stage approximately 9,000 genes showed ubiquitous expression. Genes encoding caseins, whey proteins and enzymes in lactose synthesis pathway showed higher expression in early lactation. The majority of genes in the fat metabolism pathway had high expression in transition and peak lactation milk. Most of the genes encoding for endogenous proteases and enzymes in ubiquitin-proteasome pathway showed higher expression along the course of lactation.

CONCLUSIONS

This is the first study to describe the comprehensive bovine milk transcriptome in Holstein cows. The results revealed that 69% of NCBI Btau 4.0 annotated genes are expressed in bovine milk somatic cells. Most of the genes were ubiquitously expressed in all three stages of lactation. However, a fraction of the milk transcriptome has genes devoted to specific functions unique to the lactation stage. This indicates the ability of milk somatic cells to adapt to different molecular functions according to the biological need of the animal. This study provides a valuable insight into the biology of lactation in the cow, as well as many avenues for future research on the bovine lactome.

CD24, a novel cancer biomarker, predicting disease-free survival of non-small cell lung carcinomas: a retrospective study of prognostic factor analysis from the viewpoint of forthcoming (seventh) new TNM classification

INTRODUCTION

Metastasis-associated protein CD24 has been identified as a new prognostic factor and stem cell marker in the human neoplasm. However, the importance of the CD24 in non-small cell lung carcinomas (NSCLCs) has not been elucidated well.

METHODS

We evaluated CD24 expression in 267 consecutive cases of NSCLC by immunohistochemistry using a tissue microarray technique and correlated with clinicopathologic parameters including forthcoming (seventh) new tumor node metastasis classification.

RESULTS

CD24-high expression was demonstrated in 87 of 267 (33%) and was associated with adenocarcinoma (ADC) histology than in squamous cell carcinoma histology (64 of 165 [39%] vs. 20 of 88 [23%]; p = 0.023). Patients with CD24-high tumors tended to have a higher risk of disease progression (p < 0.001) and cancer-related death (p = 0.002). Multivariate analysis proved CD24-high expression as independent prognostic factors of disease progression and cancer-related death (p = 0.002, hazard ratio = 1.78, 95% confidence interval = 1.23-2.58 and p = 0.017, hazard ratio = 1.93, 95% confidence interval =1.13-3.31). CD24-high expression had a tendency to correlate with new pathologic stage (p-stage) (p = 0.089) rather than old p-stage (p = 0.253). Performance status and new p-stage, regardless of the tumor histology, were identified as consistent independent prognostic factors of disease progression and cancer-related death. However, age was related to a significantly shorter cancer-specific survival in ADC only.

CONCLUSIONS

CD24 expression in NSCLC is associated with ADC histology and disease progression and cancer-related death, indicative of aggressive tumor behavior. Performance status and new p-stage, to a lesser extent, age correlated with progression-free survival and cancer-specific survival, regardless of tumor histology.

CD24: from A to Z

As a testament to the importance of CD24, researchers with diverse interests, including adaptive immunity, inflammation, autoimmune diseases and cancer, have encountered CD24. CD24 is overexpressed in many cancers and appears oncogenic. In the adaptive immune response, CD24 is a redundant costimulatory molecule in costimulation-rich lymphoid organs but is essential in selected target organs tested, such as brain and skin. More recent studies suggest it may have a role in discriminating danger and pathogen-associated molecular patterns by dendritic cells. The biology of CD24 is intriguing but poorly understood. Here we summarize the major findings associated with CD24 to stimulate new ideas for further research that may reveal the underlying link among the diverse processes mediated by CD24.

Regenerative potentials of the murine thyroid in experimental autoimmune thyroiditis: role of CD24

Hashimoto thyroiditis can be partially reproduced in mice by immunization with thyroglobulin or, more recently, thyroperoxidase. This experimental autoimmune thyroiditis (EAT) model has been extensively characterized during early disease phases (up to d 35 after immunization). By extending the analysis of EAT to 100 d after immunization, we noted a remarkable regenerative capacity of the thyroid and the expression of Oct-4, suggesting in vivo the existence of adult thyroid stem cells. After an almost complete destruction of the follicular architecture, occurring between d 21 and 28, the thyroid was capable of restoring its follicles and reducing the mononuclear infiltration, so that by d 100 after immunization, it regained its normal morphology and function. During this regeneration process, thyrocytes expressed high levels of CD24. We therefore assessed the role of CD24 in thyroid regeneration by inducing EAT in mice lacking CD24. Regeneration was faster in the absence of CD24, likely a consequence of the effect of CD24 on the infiltrating lymphocytes. The study suggests that the EAT model can also be used as a tool to investigate adult thyroid stem cells.

Myogenin regulates a distinct genetic program in adult muscle stem cells

In contrast to the detailed understanding we have for the regulation of skeletal muscle gene expression in embryos, similar insights into postnatal muscle growth and regeneration are largely inferential or do not directly address gene regulatory mechanisms. Muscle stem cells (satellite cells) are chiefly responsible for providing new muscle during postnatal and adult life. The purpose of this study was to determine the role that the myogenic basic helix-loop-helix regulatory factor myogenin has in postnatal muscle growth and adult muscle stem cell gene expression. We found that myogenin is absolutely required for skeletal muscle development and survival until birth, but it is dispensable for postnatal life. However, Myog deletion after birth led to reduced body size implying a role for myogenin in regulating body homeostasis. Despite a lack of skeletal muscle defects in Myog-deleted mice during postnatal life and the efficient differentiation of cultured Myog-deleted adult muscle stem cells, the loss of myogenin profoundly altered the pattern of gene expression in cultured muscle stem cells and adult skeletal muscle. Remarkably, these changes in gene expression were distinct from those found in Myog-null embryonic skeletal muscle, indicating that myogenin has separate functions during postnatal life.

Expression of CD24 in clear cell renal cell carcinoma and its prognostic significance

OBJECTIVES

To evaluate the expression patterns of CD24 in clear cell renal cell carcinoma (CCRCC) and to investigate its prognostic significance. CD24 is a cell adhesion molecule that has been thought to play an important role in tumor progression and metastasis of various cancers. CD24 expression has previously been reported in RCC, although little is known about its prognostic significance.

METHODS

We immunohistochemically analyzed CD24 expression using tissue microarray in 328 cases of CCRCC. The percentage of positively stained tumor cells was evaluated and classified into four categories: 0, 0%; 1+, 1% to 10%; 2+, 11% to 50%; and 3+, more than 50%. For statistical analysis, the cases were subdivided into a CD24-low-expression group (0 and 1+) and CD24-high-expression group (2+ and 3+).

RESULTS

High CD24 expression was significantly associated with a high nuclear grade (P = 0.005) and large tumor size (P = 0.04). The survival analysis revealed no significant association between CD24 expression and disease-specific survival (P = 0.141). However, the CD24-high-expression group had a significantly shortened progression-free survival (P = 0.005). Multivariate analysis also revealed that high CD24 expression was an independent covariate for poor progression-free survival (P = 0.043).

CONCLUSIONS

We investigated CD24 expression in CCRCC and found that high CD24 expression was associated with high nuclear grade, large tumor size, and shortened progression-free survival. Although the biologic function of CD24 in CCRCC remains unknown, the expression of CD24 can provide new prognostic information about disease progression.

Malignant ascites-derived exosomes of ovarian carcinoma patients contain CD24 and EpCAM

OBJECTIVE

CD24 is an established marker for poor prognosis in ovarian and other carcinomas. Acquisition of cytoplasmic CD24, as opposed to membranous expression, has been correlated with a higher invasiveness of tumor cells. Exosomes are small vesicles of endosomal origin that are often secreted by tumor cells. Given the emerging role of exosomes in tumor progression, we investigated whether cytoplasmic CD24 expression is correlated with the secretion of CD24 in exosomes.

METHODS

We used CD24 transfected carcinoma cell lines, ovarian carcinoma cell lines and malignant ascites fluid of ovarian carcinoma patients. Exosomes were isolated via ultracentrifugation and sucrose density fractionation and subsequently examined by Western blot analysis and gelatine zymography. In tissue sections CD24 was detected by immunohistochemical staining.

RESULTS

We show that CD24 is released by transfected as well as endogenously expressing cells in vesicles that represent exosomes. CD24 was also identified in exosomes isolated from ascites fluid of ovarian carcinoma patients. In 16 ovarian carcinomas analyzed no correlation between CD24 in tumor tissue sections and the appearance of CD24 in exosomes was detected. Furthermore, we provide evidence that the epithelial cell adhesion molecule (EpCAM), known to be overexpressed in ovarian carcinomas, is secreted in exosomes. The ascites exosomes contain gelatinolytic enzymes.

CONCLUSIONS

Our study identifies CD24 and EpCAM as cargo proteins of exosomes of cultured cell lines and malignant ascites. The exosome-associated proteolytic activity in the tumor vicinity might augment tumor invasion into the stroma.

Cytoplasmic CD24 expression is a novel prognostic factor in diffuse-type gastric adenocarcinoma

BACKGROUND

CD24, a mucin like cell surface adhesion molecule and a ligand for P-selectin, has been reported as a prognostic factor in a variety of human cancers. However, the role of CD24 in gastric adenocarcinoma remains largely unknown.

METHODS

The expression pattern of CD24 in 103 gastric adenocarcinomas (31 diffuse type, 60 intestinal type, and 12 mixed type) was analyzed by immunohistochemistry.

RESULTS

Cytoplasmic CD24 expression occurred in 50% of the gastric adenocarcinoma patients and was associated with high-stage tumor (Stage III-IV, P = .023), serosal invasion (SI, P = .010), lymphovascular invasion (LVI, P = .039), and lower 10-year survival (P = .0238). The CD24 staining pattern was different in intestinal and diffuse-type gastric adenocarcinomas. However, the tumor thrombi in lymphovascular spaces exhibited strong cytoplasmic CD24 expression in both types. Further analysis showed that cytoplasmic CD24 expression was, in fact, correlated with high-stage tumor, SI, LVI, and lower 10-year survival significantly (P = .020, P = .007, P = .018, P = .0285, respectively) in diffuse-type gastric adenocarcinoma. Moreover, multivariate analysis showed that cytoplasmic CD24 expression was an independent risk factor of SI and LVI respectively (P = .0083 and P = .0019), and thus it contributed to high-stage tumor and poor patient survival in diffuse- or mixed-type gastric adenocarcinoma.

CONCLUSIONS

Cytoplasmic expression of CD24 was associated with invasiveness and poorer prognosis and can serve as a novel target for prognostic prediction and adjuvant treatment of patients with diffuse-type gastric adenocarcinoma after tumor resection.

Mouse CD24 is required for homeostatic cell renewal

Under physiological conditions, some adult tissues retain a capacity for self-renewal. This property is attributable to the proliferation and differentiation of stem, transit-amplifying, and differentiating cells, which are regulated by cell-cell or cell-matrix interactions or by secreted factors. By gain and loss of function experiments, we demonstrate the involvement of mouse CD24 (mouse cluster of differentiation 24), which is a glycosyl phosphatidylinositol (GPI)-anchored cell-surface glycoprotein, in the regulation of homeostatic cell renewal. BrdU incorporation observations, at optical and electron-microscopic levels, have revealed increased cell proliferation in the developing brain and in the epithelia of mCD24-deleted mice. We have observed ectopic proliferative cells in the suprabasal layers of the mutant skin leading to a general disruption of basal and suprabasal layers. By contrast, ectopic mCD24 expression mediated by retroviral infection of the embryonic brain leads to a decreased number of clusters of cells generated in the progeny. Together, these results and our previous published data indicate that mCD24 contributes to the regulation of the production of differentiated cells by controlling the proliferation/differentiation balance between transit-amplifying and committed differentiated cells.

CD24 is expressed by myofiber synaptic nuclei and regulates synaptic transmission

The genes encoding several synaptic proteins, including acetylcholine receptors, acetylcholinesterase, and the muscle-specific kinase, MuSK, are expressed selectively by a small number of myofiber nuclei positioned near the synaptic site. Genetic analysis of mutant mice suggests that additional genes, expressed selectively by synaptic nuclei, might encode muscle-derived retrograde signals that regulate the differentiation of motor axon terminals. To identify candidate retrograde signals, we used a microarray screen to identify genes that are preferentially expressed in the synaptic region of muscle, and we analyzed one such gene, CD24, further. We show that CD24, which encodes a small, variably and highly glycosylated, glycosylphosphatidylinositol (GPI)-linked protein, is expressed preferentially by myofiber synaptic nuclei in embryonic and adult muscle, and that CD24 expression is restricted to the central region of muscle independent of innervation. Moreover, we show that CD24 has a role in presynaptic differentiation, because synaptic transmission is depressed and fails entirely, in a cyclical manner, after repetitive stimulation of motor axons in CD24 mutant mice. These deficits in synaptic transmission, which are accompanied by aberrant stimulus-dependent uptake of AM1-43 from axons, indicate that CD24 is required for normal presynaptic maturation and function. Because CD24 is also expressed in some neurons, additional experiments will be required to determine whether pre- or postsynaptic CD24 mediates these effects on presynaptic development and function.

Quantitative real-time RT-PCR of CD24 mRNA in the detection of prostate cancer

Background

Gene expression profiling has recently shown that the mRNA for CD24 is overexpressed in prostate carcinomas (Pca) compared to benign or normal prostate epithelial tissues. Immunohistochemical studies have reported the usefulness of anti-CD24 for detecting prostate cancer over the full range of prostate specimens encountered in surgical pathology, e.g. needle biopsies, transurethral resection of prostate chips, or prostatectomies. It is a small mucin-like cell surface protein and thus promises to become at least a standard adjunctive stain for atypical prostate biopsies. We tested the usefulness of real-time RT-PCR for specific and sensitive detection of CD24 transcripts as a supplementary measure for discriminating between malignant and benign lesions in prostatic tissues.

Methods

Total RNA was isolated from snap-frozen chips in 55 cases of benign prostatic hyperplasia (BPH) and from frozen sections in 59 prostatectomy cases. The latter contain at least 50% malignant epithelia. Relative quantification of CD24 transcripts was performed on the LightCycler instrument using hybridization probes for detection and porphobilinogen deaminase transcripts (PBGD) for normalization.

Results

Normalized CD24 transcript levels showed an average 2.69-fold increase in 59 Pca-cases (mean 0.21) when compared to 55 cases of BPH (mean 0.08). This difference was highly significant (p < 0.0001). The method has a moderate specificity (47.3%) but a high sensitivity (86.4%) if the cutoff is set at 0.0498. CD24 expression levels among Pca cases were not statistically associated with the tumor and lymph-node stage, the grading (WHO), the surgical margins, or the Gleason score.

Conclusion

The present study demonstrates the feasibility of quantitative CD24 RNA transcript detection in prostatic tissues even without previous laser microdissection.

Cytoplasmic CD24 expression in colorectal cancer independently correlates with shortened patient survival

PURPOSE

CD24 is a cell adhesion molecule that has been implicated in metastatic tumor progression of various solid tumors. We aimed to clarify the expression patterns of CD24 in colorectal cancer and to correlate these to clinicopathologic variables including patient survival.

EXPERIMENTAL DESIGN

147 colorectal carcinomas and two colon carcinoma cell lines were immunostained for CD24. Cytoplasmic and membranous immunoreactivity were semiquantitatively scored. Fisher's exact test, chi(2) test for trends, Kaplan-Meier analysis, and Cox's regression were applied.

RESULTS

The cell line CX-2 showed only a minimal membranous CD24 immunoreactivity, in contrast to HT29, which stained strongly in the cytoplasm. In colorectal cancer, 68.7% of the tumors showed membranous CD24 staining, whereas 84.4% showed cytoplasmic staining. In 10% of cases, an exceptionally strong cytoplasmic CD24 expression was observed. The latter significantly correlated to higher tumor stages (Dukes and pT), nodal or systemic metastasis, and higher tumor grade. In survival analysis, strong cytoplasmic CD24 expression correlated significantly (Cox's regression: P = 0.012, relative risk = 3.7) to shortened patient survival in the group of cases without distant metastases.

CONCLUSIONS

CD24 is commonly up-regulated in colorectal cancer and is a new independent prognostic marker which corroborates the importance of CD24 in tumor progression of this disease.

CD24 expression is a prognostic factor in intrahepatic cholangiocarcinoma

CD24, a cell surface protein originally identified in hematological malignancy, were found to be expressed in a large variety of solid tumors. It can function as a ligand for P-selectin, an adhesion receptor on activated endothelial cells and platelets. Overexpression of CD24 enhances the metastatic potential of cancer cells. We examined the expression of CD24 in 70 intrahepatic cholangiocarcinomas by immunohistochemistry and correlated the expression with clinicopathological parameters. CD24 was expressed in 36 of 70 (51%) intrahepatic cholangiocarcinomas. The expression did not significantly correlate the tumor size, stage, lymph node and distant metastasis. Patients with CD24 positive tumors had significant shorter survival time. In a multivariant analysis, CD24 expression and tumor stage were independent prognostic factors. Our data suggest that CD24 expression in intrahepatic cholangiocarcinoma is a novel prognostic marker for intrahepatic cholangiocarcinoma.

Gene expression studies provide clues to the pathogenesis of uterine leiomyoma: new evidence and a systematic review

BACKGROUND

Uterine leiomyomas are extremely common and a major cause of pelvic pain, bleeding, infertility, and the leading indication for hysterectomy. Familial and epidemiological studies provide compelling evidence that genetic alterations play an important role in leiomyoma development.

METHODS

Using Affymetrix U133A GeneChip we analysed expression profiles of 22,283 genes in paired samples of leiomyoma and adjacent normal myometrium. We compared our results with previously published data on gene expression in uterine leiomyoma and identified the overlapping gene alterations.

RESULTS

We detected 80 genes with average differences of > or = 2-fold and false discovery rates of < 5% (14 overexpressed and 66 underexpressed). A comparative analysis including eight previous gene expression studies revealed eight prominent genes (ADH1, ATF3, CRABP2, CYR61, DPT, GRIA2, IGF2, MEST) identified by at least five different studies, eleven genes (ALDH1, CD24, CTGF, DCX, DUSP1, FOS, GAGEC1, IGFBP6, PTGDS, PTGER3, TYMS) reported by four studies, twelve genes (ABCA, ANXA1, APM2, CCL21, CDKN1A, CRMP1, EMP1, ESR1, FY, MAP3K5, TGFBR2, TIMP3) identified by three studies, and 40 genes reported by two different studies.

CONCLUSIONS

Review of gene expression data revealed concordant changes in genes regulating retinoid synthesis, IGF metabolism, TGF-beta signaling and extracellular matrix formation. Gene expression studies provide clues to the relevant pathways of leiomyoma development.

Expression of CD24 in adenocarcinomas of the pancreas correlates with higher tumor grades

BACKGROUND/AIMS

CD24 is expressed in hematological malignancies as well as in a large variety of solid tumors and is often associated with a more aggressive course of the disease. We aimed to evaluate CD24 protein expression in pancreatic adenocarcinomas and to correlate it to clinicopathological data including patient survival.

METHODS

95 primary adenocarcinomas of the pancreas were immunostained using a monoclonal CD24 antibody (Ab-2, clone 24C02). Staining was evaluated as negative versus positive for statistical analysis.

RESULTS

CD24 expression was observed in 71.6% of cases with a heterogeneous distribution, and a significantly higher rate of positivity in high grade (G3) tumors. In univariate survival analyses, no association of CD24 expression with shortened overall survival of the patients could be demonstrated.

CONCLUSION

CD24 is commonly expressed in adenocarcinomas of the pancreas, preferentially high-grade tumors and thus might be a marker of disease progression.

CD24 expression is a significant predictor of PSA relapse and poor prognosis in low grade or organ confined prostate cancer

BACKGROUND

The prognostic impact of tumor grading and staging is markedly reduced in organ confined or moderately differentiated prostate cancer, which underscores the importance of new prognostic markers. Evaluating public expression data of prostate cancer, we found an upregulation of the candidate gene CD24.

METHODS

We examined immunohistochemically the expression of CD24 protein in 31 nodal metastases and 102 adenocarcinomas of the prostate and correlated our findings to clinicopathological parameters.

RESULTS

CD24 expression was found in 48% of primary prostate cancer cases and in 68% of lymph node metastases. Kaplan Meier curves and Cox regression analysis showed that CD24 expression was strongly linked to significantly earlier disease progression (relative risk = 3.2), which was especially pronounced in organ confined, or moderately differentiated primary prostate tumors.

CONCLUSIONS

We conclude that CD24 is an important prognostic tissue marker for prostate cancer which could help to define patients of low or high risk of recurrence.

Strategy for elucidating differentially expressed genes in leiomyomata identified by microarray technology

OBJECTIVE

cDNA microarray technology identifies genes that are differentially expressed between tissues. Our previous study identified several genes that might contribute to the fibroid phenotype. We therefore sought to confirm genes involved in three distinct signal transduction pathways.

DESIGN

Evaluation of differential mRNA and protein expression of Dlk, Frizzled-2, and CD-24 in fibroids compared with adjacent myometrium. University hospital.

PATIENT(S)

Five women undergoing medically indicated hysterectomy for symptomatic fibroids.

INTERVENTION(S)

Microarray analysis of up to 33000 genes, reverse transcriptase-polymerase chain reaction (RT-PCR), real-time RT-PCR, Western blot, and immunohistochemistry.

MAIN OUTCOME MEASURE(S)

Expression of mRNA transcripts and protein in fibroid compared with myometrium.A more extensive microarray confirmed differential expression of Frizzled-2 and CD-24 but did not confirm Dlk overexpression. RT-PCR and real-time PCR demonstrated equivalent Dlk mRNA expression between fibroid and myometrium (ratio, 1.02), a slight Frizzled-2 overexpression (ratio, 2.09), and robust CD-24 overexpression in fibroids (ratio, 12.35). Western blot and immunohistochemistry confirmed Frizzled-2 overexpression, but did not confirm Dlk overexpression.

CONCLUSION(S)

Microarray technology is the first phase of tissue evaluation, but changes in gene expression must be confirmed. Confirmed genes can then be used to generate hypotheses testing their involvement in fibroid development.

CD24 is an independent prognostic marker of survival in nonsmall cell lung cancer patients

Originally identified as a B-cell marker, expression of the cell surface molecule CD24 has meanwhile been observed in a variety of human malignancies. It appears to function as a ligand of P-Selectin, an adhesion molecule that is present in activated platelets and endothelial cells. We aimed to determine the rate of CD24 expression in our nonsmall cell lung cancer (NSCLC) collection and to clarify its correlation with clinicopathological parameters including patients' survival. A total of 89 NSCLC were analysed immunohistochemically using a monoclonal CD24 antibody (clone 24C02) and a standard detection system (LSAB, DAKO) on NSCLC tissue microarrays (TMA). The staining was semiquantitatively scored (0, 1+, 2+, 3+) and grouped into high (2+, 3+)- and low (0, 1+)-level expression for statistical analysis. A high level of CD24 expression was observed in 45% of the cases, preferentially adenocarcinomas. Patients whose tumours had a high CD24 expression showed a significantly shorter median survival time of 23 months vs 38 months (P=0.033, log-rank test). Similarly tumour, grading, nodal status and clinical stage were significant prognostic markers in univariate survival analysis. Importantly, in the Cox regression-based multivariate analysis, CD24 expression (P=0.025) together with tumour stage (P=0.006) and grade (P=0.011) proved to be independent prognostic parameters. We hypothesise that the decreased survival of NSCLC patients with strongly CD24-positive tumours is related to an enhanced propensity of haematogenous metastasis formation, which might be P-Selectin mediated.

CD44H is expressed by cells of the oligodendrocyte lineage and by oligodendrogliomas in humans

CD44, a family of cell surface glycoproteins involved in cell-cell and cell-extracellular matrix adhesion, is widely expressed in the white matter of the normal brain and in astrocytic gliomas under its standard form (CD44s also called CD44H). On the other hand, several variants have been found in brain metastases and rarely found in gliomas. We have investigated by immunohistochemistry CD44H and CD44v6 expression in 28 oligodendrogliomas. All tumors were CD44v6 negative whereas nearly all tumors were immunolabelled with anti-CD44H antibody. Immunostaining increased in parallel with grade and was particulary strong around vessels and in tumoral subpial nodules. Western blot analysis showed that oligodendrogliomas expressed the same 80-kDa CD44 isoform as normal brain. Since gliomas may arise from a dividing progenitor cell, we also studied CD44H expression during the oligodendrocyte lineage in vitro in parallel with specific markers of the O-2A cells. Precursor cells (PSA-NCAM positive), O-2A progenitor cells, as well as preoligodendrocytes (A2B5 positive cells) and immature oligodendrocytes (O4 positive cells), coexpressed CD44H. Our data showed that CD44H is expressed by cells of the oligodendrocyte lineage in vitro and by oligodendrogliomas in vivo especially in sites of dissemination such as subpial spaces. This suggests that CD44H could play a role in migration of tumor cells in oligodendrocytic tumors.

CD24 is expressed in ovarian cancer and is a new independent prognostic marker of patient survival

CD24 is a small heavily glycosylated glycosylphosphatidylinositol-linked cell surface protein, which is expressed in hematological malignancies as well as in a large variety of solid tumors. Very recently its expression in ovarian cancer has been found on RNA level by chip analysis. We evaluated CD24 protein expression by immunohistochemistry in 9 normal ovaries and 69 epithelial ovarian tumors (5 adenomas, 8 borderline tumors, and 56 carcinomas) with known follow-up data. Surface epithelium of normal ovaries as well as adenomas did not express CD24. In borderline tumors CD24 was expressed in membrane in 75% of cases, whereas cytoplasmic expression was detected in only one of nine cases. In invasive ovarian carcinomas, a membranous expression was detected in 84% and a cytoplasmic expression in 59% of cases. In univariate survival analysis of all invasive ovarian carcinomas, a highly significant association of increased cytoplasmic CD24 expression with shortened patient survival (mean 98 months versus 37 months, P = 0.0002, log rank test) was demonstrated. Other significant prognostic parameters were International Federation of Gynecology and Obstetrics (FIGO) stage, Silverberg grade, patient age, undifferentiated histological type, and metastatic disease. We did not detect a significant correlation of CD24 with these clinicopathological parameters. In multivariate analysis, only CD24 and FIGO stage were independent prognostic parameters. Our data suggest that the expression of CD24 as detected by immunohistochemistry is a new independent molecular marker for shortened survival time of patients with epithelial ovarian carcinomas.

Increased neurogenesis in adult mCD24-deficient mice

mCD24, a glycosylphosphatidylinositol-anchored highly glycosylated molecule, is expressed on differentiating neurons during development. In the adult CNS, its expression is restricted to immature neurons located in two regions showing ongoing neurogenesis: the subventricular zone (SVZ) of the lateral ventricle pathway and the dentate gyrus (DG) of the hippocampal formation. Here, combining bromodeoxyuridine (BrdU) and proliferating cell nuclear antigen labelings we confirmed that mCD24 is expressed on proliferating cells. To determine whether the inactivation of the molecule may affect adult neurogenesis, we analyzed the phenotype of mCD24-deficient mice (mCD24-/-). We labeled cells in S-phase with a pulse, a long, or a cumulative administration of BrdU and analyzed cells in different zones according to their dividing rate (rapid and slow) both in the control and mCD24-/-. We found a significant increase in the number of rapid (in the SVZ and the DG) and slow (in the SVZ) proliferating cells. Cumulative assays revealed a global reduction of the total cell cycle duration of rapidly proliferating precursors of SVZ. We investigated the fate of supernumerary cells and observed an increased number of apoptotic cells (terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling) in the mutant SVZ. Furthermore, we found no difference in the size of the olfactory bulb between wild-type (WT) and mutant mice. In support, mCD24 deletion did not appear to affect migration in the migratory stream. A comparison of the organization of migrating precursors between WT and mCD24 -/-, both in vivo at the optic and electron microscopic levels and in SVZ cultured explants, did not show any changes in the arrangement of neuroblasts in chain-like structures. Altogether, our data suggest that mCD24 regulates negatively cell proliferation in zones of secondary neurogenesis.

Diagnostic protein expression in human muscle biopsies

Using immunohistochemistry in diagnosing neuromuscular diseases is meant to enhance the diagnostic yield in two ways. The first application aims at visualizing molecules which are developmentally, neurally, and/or immunologically regulated and not expressed by normal muscle. They are upregulated in pathological conditions and may help assign a given muscular biopsy to one of the main diagnostic entities (muscular dystrophies, inflammatory myopathy, neurogenic atrophy). In the past, muscle-specific molecules with a defined expression pattern during fetal myogenesis served as antigens, with the rationale that the developmental program was switched on in new fibers. Recently, myofibers in diseased muscle are thought of as targets of stimuli which are released by macrophages in muscular dystrophy, by lymphocytes in inflammatory myopathies, or by a lesioned peripheral nerve in neurogenic atrophies. This has somewhat blurred the borders between the diagnostic groups, for certain molecules, e.g. cytokines, may be upregulated after experimental necrotization, denervation, and also in inflammatory myopathies. In the second part of this review we summarise the experiences of a Centre in the North of England that specialises in the diagnosis and clinical support of patients with muscular dystrophy. Emphasis is placed on the use of protein expression to guide mutation analysis, particularly in the limb-girdle muscular dystrophies (a group of diseases that are very difficult to differentiate on clinical grounds alone). We confirm that genetic analysis is essential to corroborate the results of protein analysis in certain conditions (particularly in calpainopathy). However, we conclude that analysing biopsies for abnormal protein expression is very useful in aiding the decision between alternative diagnoses.

Sequence of expression of MyoD1 and various cell surface and cytoskeletal proteins in regenerating mouse muscle fibers following treatment with sodium dihydrogen phosphate

An immunohistochemical study was performed in order to evaluate the sequence of expression of various cell surface proteins [neural cell adhesion molecule (NCAM) and its polysialylated isoform, PSA NCAM, and utrophin], cytoskeletal proteins (myosin heavy chain isoforms, desmin) and the transcription factor MyoD1 in regenerating mouse muscle fibers following treatment with sodium dihydrogen phosphate. The sequence of the regeneration process with this new myotoxic agent is similar to that which can be observed with other myotoxic substances (local anaesthetics such as bupivacaine or snake venoms). The results show that NCAM, PSA NCAM and desmin were already present on the first day after injury in the presumptive myoblasts. The highest level of all of these proteins was observed on the third day. At this stage, regenerating muscle fibers also strongly and diffusely expressed myosin heavy chain isoforms and utrophin throughout their sarcolemma, whereas MyoD1 expression was observed in the regenerating myonuclei. PSA NCAM and MyoD1 had gradually disappeared from the muscle fibers by the seventh day, by which time, the expression of the other developmentally regulated proteins had also decreased. On the 21st day after injury, a few fibers still expressed NCAM but not the other proteins. This study first shows that sodium dihydrogen phosphate is a new myotoxic agent that is cheap, widely available and easy to handle. It also establishes the schedule of expression of various developmentally regulated proteins in regenerating mouse muscle fibers.

The PEN5 epitope identifies an oligodendrocyte precursor cell population and pilocytic astrocytomas

PEN5 is a sulfated polylactosamine carbohydrate epitope first described in a subpopulation of mature natural killer cells. Here we report that it is also expressed in a developmentally regulated fashion in human and rat central nervous systems and that its protein carrier is P-selectin glycoprotein ligand-1 (PSGL-1), a ligand for selectins. In rat neural primary cultures, PEN5 is transiently and selectively expressed by oligodendrocyte precursor cells and marks the transition from proliferative to postmitotic stages. In concordance, in human central nervous system tumors, PEN5 is observed in a subset of oligodendrogliomas and in all pilocytic astrocytomas, a class of tumor of uncertain histogenesis. These data suggest that PEN5-PSGL-1 plays a role in the differentiation of oligodendrocytes and that pilocytic astrocytomas are likely to result from a dysregulation occurring in oligodendrocyte precursor cells at the crucial stage of exit from the cell cycle.

Sequence of expression of MyoD1 and various cell surface and cytoskeletal proteins in regenerating mouse muscle fibers following treatment with sodium dihydrogen phosphate

An immunohistochemical study was performed in order to evaluate the sequence of expression of various cell surface proteins [neural cell adhesion molecule (NCAM) and its polysialylated isoform, PSA NCAM, and utrophin], cytoskeletal proteins (myosin heavy chain isoforms, desmin) and the transcription factor MyoD1 in regenerating mouse muscle fibers following treatment with sodium dihydrogen phosphate. The sequence of the regeneration process with this new myotoxic agent is similar to that which can be observed with other myotoxic substances (local anaesthetics such as bupivacaine or snake venoms). The results show that NCAM, PSA NCAM and desmin were already present on the first day after injury in the presumptive myoblasts. The highest level of all of these proteins was observed on the third day. At this stage, regenerating muscle fibers also strongly and diffusely expressed myosin heavy chain isoforms and utrophin throughout their sarcolemma, whereas MyoD1 expression was observed in the regenerating myonuclei. PSA NCAM and MyoD1 had gradually disappeared from the muscle fibers by the seventh day, by which time, the expression of the other developmentally regulated proteins had also decreased. On the 21st day after injury, a few fibers still expressed NCAM but not the other proteins. This study first shows that sodium dihydrogen phosphate is a new myotoxic agent that is cheap, widely available and easy to handle. It also establishes the schedule of expression of various developmentally regulated proteins in regenerating mouse muscle fibers.

Differential mRNA display analysis of two related but functionally distinct rat insulinoma (RIN) cell lines: identification of CD24 and its expression in the developing pancreas

To identify genes that might play a role in growth and differentiation of pancreatic beta-cells, we have applied the technique of differential mRNA display to the lineage-related, but functionally distinct rat insulinoma (RIN) cell lines RIN-5AH and RIN-A12. Direct comparison of PCR-generated RIN-5AH and RIN-A12 cDNAs on DNA sequencing gels revealed 31 differentially expressed bands. By Northern blot hybridization, authentic differential expression was confirmed for three cDNAs derived from RIN-5AH cells and four cDNAs from RIN-A12 cells. Nucleotide sequences were determined for these cDNAs and database searches identified one known gene that encoded heat stable antigen CD24. Of the remaining six genes, three matched with established sequence tags from fetal tissue, and three were potentially novel. By RT-PCR analysis, five of the seven genes were expressed in normal fetal and/or adult pancreas. In a detailed survey of CD24 protein expression in the pancreas using the CD24-specific monoclonal antibody J11d, CD24 was predominantly expressed in ductal epithelial cells (E13.5-15.5), developing endocrine (alpha, beta and delta) and exocrine cells (E15.5-20.5) and mature exocrine and peripheral islet delta-cells post E20.5. The retention of CD24 expression in a large proportion of delta-cells but only in a minority of alpha- and beta-cells leads us to hypothesize that CD24 may mark a pool of precursor endocrine cells within adult islets.

Altered Erythrocytes and a Leaky Block in B-Cell Development in CD24/HSA-Deficient Mice

The heat stable antigen (HSA, or murine CD24) is a glycosyl phosphatidylinositol-linked surface glycoprotein expressed on immature cells of most, if not all, major hematopoietic lineages, as well as in developing neural and epithelial cells. It has been widely used to stage the maturation of B and T lymphocytes because it is strongly induced and then repressed again during their maturation. Terminally differentiated lymphocytes, as well as most myeloid lineages, are negative for HSA. Erythrocytes are an exception in that they maintain high levels of HSA expression. HSA on naive B cells has been shown to mediate cell-cell adhesion, while HSA on antigen-presenting cells has been shown to mediate a costimulatory signal important for activating T lymphocytes during an immune response. Here, we characterize mice that lack a functional HSA gene, constructed by homologous recombination in embryonic stem cells. While T-cell and myeloid development appears normal, these mice show a leaky block in B-cell development with a reduction in late pre-B and immature B-cell populations in the bone marrow. Nevertheless, peripheral B-cell numbers are normal and no impairment of immune function could be detected in these mice in a variety of immunization and infection models. We also observed that erythrocytes are altered in HSA-deficient mice. They show a higher tendency to aggregate and are more susceptible to hypotonic lysis in vitro. In vivo, the mean half-life of HSA-deficient erythrocytes was reduced. When infected with the malarial parasite Plasmodium chabaudi chabaudi, the levels of parasite-bearing erythrocytes in HSA-deficient mice were also significantly elevated, but the mice were able to clear the infection with kinetics similar to wild-type mice and were immune to a second challenge. Thus, apart from alterations in erythrocytes and a mild block in B-cell development, the regulated expression of HSA appears to be dispensable for the maturation and functioning of those cell lineages that normally express it.

Expression of developmentally regulated cytoskeleton and cell surface proteins in childhood spinal muscular atrophies

Expression of some developmentally regulated cytoskeleton components (desmin, vimentin and myosin heavy chain isoforms) and cell surface proteins (including neural cell adhesion molecule (NCAM), its polysialylated (PSA) isoform and CD24) have been studied by immunohistochemical detection in a series of 23 infantile spinal muscular atrophies (SMA). According to the clinical classification established by Byers and Banker in 1961, 8 cases were type I SMA (Werdnig-Hoffmann's disease), 10 cases were type II (intermediate form), and 5 cases were type III (Kugelberg-Welander's disease). In 15 cases, the percentage of immunoreactive fibers with the various antibodies used has been quantified and the results correlated with clinical data. The aim of the study was to search for variations in the pattern of expression of the proteins to improve the accuracy of diagnosis and prognosis, and to gain an understanding of the pathological processes involved in SMA. The results showed that the pattern of expression of these cytoskeleton and cell surface proteins is abnormal in all types of SMA. However, it was strikingly different in type I and II SMA as opposed to type III. In type I and II SMA, strong NCAM and developmental myosin heavy chain (MHC) expression was observed in atrophic fibers. Numerous atrophic fibers co-expressed desmin and vimentin as well as slow and fast adult MHC. Very few of them expressed PSA NCAM, fetal MHC and CD24. In type III SMA, the number of fibers expressing NCAM, developmental MHC and co-expressing slow and fast adult MHC was low and virtually none of them expressed vimentin or desmin. These findings are in favor of a denervation process occurring very early in life, probably even in utero, in type I and II SMA and leading to a severe impairment of muscle fibers maturation. In contrast, in type III SMA, the process is initiated well after birth and affects mature muscle fibers. In all types of SMA, the ability of muscle fibers to regenerate is low, although some fibers may be reinnervated. Immunohistochemical data was not related to the patients follow-up and thus has no prognostic value.

B-cell maturation in chimaeric mice deficient for the heat stable antigen (HSA/mouse CD24)

The murine differentiation marker heat stable antigen (HSA) is a GPI-anchored surface glycoprotein showing strong expression on immature B- and T-lymphocytes and gradually reduced expression during maturation. Although HSA has been suggested to be involved in adhesion and/or signalling, its function has not been clearly demonstrated so far. In order to elucidate the function of HSA, we analysed chimaeric mice that were generated by targeted disruption of both HSA alleles in ES cells. These mice contain normal numbers of peripheral B-cells and normal serum IgM and IgG titres of ES cell-derived allotype, demonstrating that HSA expression on B-cells is not an absolute requirement for their maturation. However, a reduction in immature B-cells in the bone marrow and an altered degree of bone marrow and blood chimaerism suggest that HSA expression influences the maturation of B-cells.

Differential expression of cell adhesion molecules (CAM), neural CAM and epithelial cadherin in ependymomas and choroid plexus tumors

A series of frozen specimens of 18 ependymomas and 7 choroid plexus tumors were examined for their expression of cell adhesion molecules, such as neural cell adhesion molecule (NCAM), its polysialylated isoforms (PSA NCAM), and epithelial (E-) cadherin, and of intermediate filament proteins, such as glial fibrillary acidic protein (GFAP) and cytokeratin, using various monoclonal and polyclonal antibodies. Normal choroid plexus and ependyma were taken as controls. Anti-E-cadherin immunoreactivity was observed on the basolateral part of most adult choroid plexus and benign choroid plexus papilloma cells. However, a small number of atypical papillomas and carcinoma cells showed anti- E-cadherin immunoreactivity throughout their cell surface membrane. NCAM were not expressed by adult choroid plexus and benign papilloma cells. Only a few cells expressed NCAM and PSA NCAM in developing choroid plexus, atypical papillomas and carcinomas. Cytokeratin expression was always observed in choroid plexus and their tumors; GFAP expression was variable from case to case. In contrast, ependymal cells and their tumors never expressed E-cadherin but strongly expressed NCAM. PSA NCAM was found in ependymomas exhibiting anaplastic features. All ependymomas strongly expressed GFAP and a few demonstrated slight expression of cytokeratin. These data suggest that, besides GFAP and cytokeratin, NCAM and E-cadherin are of potential diagnostic value in distinguishing choroid plexus tumors from ependymomas. E-cadherin and NCAM may play a role in the functional organization of normal choroid plexus and ependyma, respectively. In particular, incomplete or irregular anti-E-cadherin expression in choroid plexus tumors and PSA NCAM immunoreativity in ependymomas and choroid plexus tumors correlates with the emergence of anaplastic histological features.