Aspirin inhibits thrombin action on endothelial cells via up-regulation of aminopeptidase N/CD13 expression

OBJECTIVE

We hypothesized that aspirin may exhibit its anti-atherosclerotic effects via mechanisms other than cyclooxygenase inhibition in platelets.

METHODS AND RESULTS

Using enhanced subtraction hybridization analysis, we found in human umbilical vein endothelial cells (HUVECs) that aspirin up-regulates the expression of aminopeptidase N (APN/CD13) mRNA and its surface protein levels in a dose-dependent manner. Enzymatic activity of APN/CD13 on HUVECs was increased approximately 1.5-fold by 1 mmol L(-1) of aspirin, and treatment with bestatin, an inhibitor for APN/CD13 metalloprotease activity, attenuated the enhanced activities of APN/CD13. Since activated thrombin receptor is reported to be inactivated by APN/CD13 in vitro, protective actions of aspirin on HUVECs by thrombin stimulation were examined, resulting in the suppression of endothelin-1 and reactive oxygen species productions in HUVECs. These inhibitory actions of aspirin were partially abrogated by bestatin.

CONCLUSIONS

Aspirin may exert its anti-atherothrombotic effects in part via the inhibition of thrombin action by up-regulating APN/CD13 on endothelial cells.

Altered expression of TFF-1 and CES-2 in Barrett's Esophagus and associated adenocarcinomas

Identification of biomarkers to recognize individuals with Barrett's esophagus (BE) predisposed to develop malignancy is currently a pressing issue. We utilized gene expression profiling to compare molecular signatures of normal esophagus and stomach, BE, and adenocarcinoma (AC) to identify such potential biomarkers. Over 22,000 genes were analyzed by oligonucleotide microarrays on 38 unique RNA Unsupervised and supervised clusterings were performed on a subset of 2849 genes that varied most significantly across the specimens. Immunohistochemistry (IHC) for two of the significantly differentially expressed gene products was performed on tissue microarrays. Unsupervised clustering identified two discernable molecular BE profiles, one of which was similar to normal gastric tissue ("BE1"), and another that was shared by several of the AC specimens ("BE2"). The BE1 profile included expression of several genes that have been described as tumor-suppressor genes, most notably trefoil factor 1 (TFF-1). The BE2 profile included expression of genes previously found overexpressed in cancers, such as carboxylesterase-2 (CES-2). IHC demonstrated the loss of TFF-1 late in the progression of BE to AC. It also revealed CES-2 as being upregulated in AC documented to have arisen in the presence of BE. These potential biomarkers, as well as the relative expression of genes from BE1 versus those from BE2, may be validated in the future to aid in risk stratification and guide treatment protocols in patients with BE and associated AC.

CD13 (aminopeptidase N) can associate with tumor-associated antigen L6 and enhance the motility of human lung cancer cells

Cancer metastasis is a multiple-step process that involves the regulated interaction of diverse cellular proteins. We recently reported that the expression of tumor-associated antigen L6 (TAL6) promoted the invasiveness of lung cancer cells and was inversely correlated with disease-free survival of squamous lung carcinoma patients. We now report that CD13 (aminopeptidase N) can associate with TAL6 and can enhance cancer cell migration. CD13 was shown by coimmunoprecipitation to associate in vitro with TAL6 on several cancer cell lines and to associate in vivo by antibody-mediated copatching immunofluorescence. CD13 was selectively expressed on highly invasive CL1-5 lung cancer cells as compared to poorly invasive CL1-0 lung cancer cells. The role of CD13 aminopeptidase activity in regulating cell motility was investigated with chemical inhibitors, specific antibodies and a catalytically inactive CD13 protein. Inhibition of CD13 aminopeptidase activity by nontoxic concentrations of leuhistin modestly decreased the migration of CL1-5 cells. In contrast, binding of CD13 by specific antibodies significantly reduced both the migration and the invasion of CL1-5 cells. Poorly invasive CL1-0 cells that stably expressed CD13 displayed significantly (p < or = 0.0005) enhanced cell migration (300% of control). Expression of an enzymatically inactive CD13 mutant on CL1-0 cells also significantly (p < or = 0.0005) enhanced cell migration (200% of control). Our results show that TAL6 and CD13 can form a complex on lung cancer cells, that these molecules can modulate cell migration and invasion and that the influence of CD13 on cell motility did not strictly depend on its aminopeptidase activity.

Bimodal cell populations are common in chronic lymphocytic leukemia but do not impact overall survival

Flow cytometric histograms were evaluated for bimodal antigen expression on samples from 246 patients diagnosed with chronic lymphocytic leukemia (CLL) at University Hospitals of Cleveland, Cleveland, OH. Survival data were obtained, and the clinical significance of bimodality was evaluated using the Kaplan-Meier method and the log-rank test. Bimodal antigen expression was found in 107 cases (43.5%). CD38 and CD13 were the most common antigens to demonstrate bimodality at 14.5% and 12.9%, respectively, and CD20, CD11c, CD5, FMC-7, and surface immunoglobulin also were frequently bimodal. Bimodal antigen expression, the number of bimodal antigens, and bimodality of a specific antigen were not associated with decreased survival in patients with CLL, although bimodality for CD38 trended toward worse overall survival. Therefore, although bimodal antigen expression is common in CLL, the presence of bimodality does not seem to have significant prognostic importance

Bacillus thuringiensis Cry1Ca-resistant Spodoptera exigua lacks expression of one of four Aminopeptidase N genes

Background

Insecticidal toxins from Bacillus thuringiensis bind to receptors on midgut epithelial cells of susceptible insect larvae. Aminopeptidases N (APNs) from several insect species have been shown to be putative receptors for these toxins. Here we report the cloning and expression analysis of four APN cDNAs from Spodoptera exigua.

Results

Suppression Subtractive Hybridization (SSH) was used to construct cDNA libraries of genes that are up-and down-regulated in the midgut of last instar larvae of beet armyworm, S. exigua exposed to B. thuringiensis Cry1Ca toxin. Among the clones from the SSH libraries, cDNA fragments coding for two different APNs were obtained (APN2 and APN4). A similar procedure was employed to compare mRNA differences between susceptible and Cry1Ca resistant S. exigua. Among the clones from this last comparison, cDNA fragments belonging to a third APN (APN1) were detected. Using sequences obtained from the three APN cDNA fragments and degenerate primers for a fourth APN (APN3), the full length sequences of four S. exigua APN cDNAs were obtained. Northern blot analysis of expression of the four APNs showed complete absence of APN1 expression in the resistant insects, while the other three APNs showed similar expression levels in the resistant and susceptible insects.

Conclusion

We have cloned and characterized four different midgut APN cDNAs from S. exigua. Expression analysis revealed the lack of expression of one of these APNs in the larvae of a Cry1Ca-resistant colony. Combined with previous evidence that shows the importance of APN in the mode of action of B. thuringiensis toxins, these results suggest that the lack of APN1 expression plays a role in the resistance to Cry1Ca in this S. exigua colony.

Aminopeptidase N/CD13 regulates the fetal liver microenvironment of hematopoiesis

Fetal liver (FL) hematopoiesis is thought to be important for expanding the cell number during ontogeny. In order to investigate the cellular interaction molecules among FL stromal and hematopoietic cells, we established a monoclonal antibody, Ndk-10, that reacts with FL stromal cells but not with dish non-adherent cells. When Ndk-10 was added to an FL stromal and hematopoietic cell-coculture, it inhibited the survival of c-kit+ cells. The inhibitory activity of Ndk-10 was also observed in the fetal liver organ culture. The Ndk-10 recognized a 150 kD molecule in the adherent cells of FL and kidney, and the N-terminal amino acid sequence was identical to that of mouse aminopeptidase N/CD13. The peptidase activity of CD13 was inhibited by Ndk-10, and addition of its specific inhibitor resulted in the same inhibitory activity as Ndk-10. We propose that aminopeptidase N/CD13 is a critical molecule that regulates the survival of c-kit+ cells in the FL microenvironment.

Myeloid antigens in childhood lymphoblastic leukemia: clinical data point to regulation of CD66c distinct from other myeloid antigens

Background

Aberrant expression of myeloid antigens (MyAgs) on acute lymphoblastic leukemia (ALL) cells is a well-documented phenomenon, although its regulating mechanisms are unclear. MyAgs in ALL are interpreted e.g. as hallmarks of early differentiation stage and/or lineage indecisiveness. Granulocytic marker CD66c – Carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) is aberrantly expressed on ALL with strong correlation to genotype (negative in TEL/AML1 and MLL/AF4, positive in BCR/ABL and hyperdiploid cases).

Methods

In a cohort of 365 consecutively diagnosed Czech B-precursor ALL patients, we analyze distribution of MyAg+ cases and mutual relationship among CD13, CD15, CD33, CD65 and CD66c. The most frequent MyAg (CD66c) is studied further regarding its stability from diagnosis to relapse, prognostic significance and regulation of surface expression. For the latter, flow cytometry, Western blot and quantitative RT-PCR on sorted cells is used.

Results

We show CD66c is expressed in 43% patients, which is more frequent than other MyAgs studied. In addition, CD66c expression negatively correlates with CD13 (p < 0.0001), CD33 (p = 0.002) and/or CD65 (p = 0.029). Our data show that different myeloid antigens often differ in biological importance, which may be obscured by combining them into "MyAg positive ALL". We show that unlike other MyAgs, CD66c expression is not shifted from the onset of ALL to relapse (n = 39, time to relapse 0.3–5.3 years). Although opposite has previously been suggested, we show that CEACAM6 transcription is invariably followed by surface expression (by quantitative RT-PCR on sorted cells) and that malignant cells containing CD66c in cytoplasm without surface expression are not found by flow cytometry nor by Western blot in vivo. We report no prognostic significance of CD66c, globally or separately in genotype subsets of B-precursor ALL, nor an association with known risk factors (n = 254).

Conclusion

In contrast to general notion we show that different MyAgs in lymphoblastic leukemia represent different biological circumstances. We chose the most frequent and tightly genotype-associated MyAg CD66c to show its stabile expression in patients from diagnosis to relapse, which differs from what is known on the other MyAgs. Surface expression of CD66c is regulated at the gene transcription level, in contrast to previous reports.

CCR2-mediated recruitment of fibrocytes to the alveolar space after fibrotic injury

Bone marrow-derived cells are known to play important roles in repair/regeneration of injured tissues, but their roles in pathological fibrosis are less clear. Here, we report a critical role for the chemokine receptor CCR2 in the recruitment and activation of lung fibrocytes (CD45(+), CD13(+), collagen 1(+), CD34(-)). Lung fibrocytes were isolated in significantly greater numbers from airspaces of fluorescein isothiocyanate-injured CCR2(+/+) mice than from CCR2(-/-) mice. Transplant of CCR2(+/+) bone marrow into CCR2(-/-) recipients restored recruitment of lung fibrocytes and susceptibility to fibrosis. Ex vivo PKH-26-labeled CCR2(+/+) lung fibrocytes also migrated to injured airspaces of CCR2(-/-) recipients in vivo. Isolated lung fibrocytes expressed CCR2 and migrated to CCL2, and CCL2 stimulated collagen secretion by lung fibrocytes. Fibrocytes could transition into fibroblasts in vitro, and this transition was associated with loss of CCR2 expression and enhanced production of collagen 1. This is the first report describing expression of CCR2 on lung fibrocytes and demonstrating that CCR2 regulates both recruitment and activation of these cells after respiratory injury.

The ectopeptidases CD10, CD13, CD26, and CD143 are upregulated in gastric cancer

Due to their extracellular orientation, the ectopeptidases CD10, CD13, CD26, and CD143 have numerous functions, including the post-secretory processing of the neuropeptides and peptide hormones involved in the regulation of growth and differentiation in the gastrointestinal tract. We investigated the transcription and expression pattern of these four ectopeptidases in gastric carcinomas (GC), the corresponding non-neoplastic epithelium, a selection of lymph node metastases (LNM), and the MKN28, AGS, NCI-N87, KATO III gastric cancer cell lines. The gastric foveolar epithelium did not express CD10, CD13, or CD143, but the intestinal metaplasia demonstrated strong immunoreactivity at the brush border for all four ectopeptidases. CD10, CD13, and CD143 were significantly up-regulated in GCs and the lymph node metastases, confirming that they are important for the tumor cell biology. However, there is a lack of correlation between expression in intestinal metaplasia and tumor, as well as in tumor and LNM. Cell proliferation assays were performed with MKN28 and AGS, in which inhibition of CD10 significantly reduced the growth of both cell lines, and inhibition of CD13 significantly increased the proliferation of the AGS cells, indicating that the ability to degrade gastrointestinal peptides may play an important role in the pathobiology of gastric cancer.

High-level gene expression in Lactobacillus plantarum using a pheromone-regulated bacteriocin promoter

AIMS

To use promoters and regulatory genes involved in the production of the bacteriocin sakacin P to obtain high-level regulated gene expression in Lactobacillus plantarum.

METHODS AND RESULTS

In a plasmid containing all three operons naturally involved in sakacin P production, the genes encoding sakacin P and its immunity protein were replaced by the aminopeptidase N gene from Lactococcus lactis (pepN) or the beta-glucuronidase gene from Escherichia coli (gusA). The new genes were precisely fused to the start codon of the sakacin P gene and the stop codon of the immunity gene. This set-up permitted regulated (external pheromone controlled) overexpression of both reporter genes in L. plantarum NC8. For PepN, production levels amounted to as much as 40% of total cellular protein.

CONCLUSIONS

Promoters and regulatory genes involved in production of sakacin P are suitable for establishing inducible high-level gene expression in L. plantarum.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study describes a system for controllable gene expression in lactobacilli, giving some of the highest expression levels reported so far in this genus.

Reduced growth, increased vascular area, and reduced response to cisplatin in CD13-overexpressing human ovarian cancer xenografts

PURPOSE

Expression of aminopeptidase N/CD13 can be detected in several solid tumor types. Thus far, the role of CD13 in ovarian cancer has not been studied. We have investigated the expression pattern and biological function of CD13 in ovarian cancer.

EXPERIMENTAL DESIGN

First, we studied the expression of CD13 in ovarian cancer tissue of 15 patients representing three different histological types (5 patients each) by immunohistochemistry. We then stably transfected the IGROV-1 human ovarian cancer cell line with a CD13 expression vector and examined the biological effect of CD13 in vitro and in vivo.

RESULTS

The expression of CD13 in ovarian cancer was associated with the histological subtype: CD13 expression in tumor cells was observed in 80-100% of the patients with a serous or mucinous carcinoma and in only 20% of the clear cell carcinoma patients. In all patients' tumor samples, CD13-positive blood vessels were present. CD13 overexpression in IGROV-1 cells did not affect in vitro cell growth and sensitivity to doxorubicin, cisplatin, or gemcitabine. CD13 overexpression reduced invasion in Matrigel, which appeared to be independent of the aminopeptidase activity of CD13. Furthermore, the growth rate of IGROV-1/CD13 xenografts was reduced. The area of the vessel lumens was enlarged in a small percentage of vessels in the CD13-overexpressing xenografts. In addition, the CD13-overexpressing tumors were less sensitive to cisplatin.

CONCLUSIONS

CD13 is expressed in tumor as well as endothelial cells in human ovarian cancer. Our results suggest that CD13 overexpression affects ovarian cancer growth, vascular architecture, and response to chemotherapy. Further elucidation of the mechanism of the observed effects of CD13 is warranted to better understand its role in the pathophysiology of ovarian cancer.

Cellular analysis of growth suppression induced by the Notch ligands, Delta-1 and Jagged-1 in two myeloid leukemia cell lines

It is known that Notch activation promotes the self-renewal of hematopoietic cells. However, we have previously found that the growth of a myeloid leukemia cell line, OCI/AML-6, was suppressed by Notch activation induced by stimulation with a recombinant Notch ligand, Delta-1 protein. We recently found that the growth of another leukemia cell line, THP-1, was also suppressed by the ligands Delta-1 and Jagged-1. In this study, we tried to clarify the cellular and molecular mechanism of the growth suppression induced by Notch activation. Flow cytometric analysis showed that Delta-1 stimulation increased the expression of differentiation markers such as CD11b and CD13 while it decreased the expression of CD117 (c-KIT), a marker for primitive cells in THP-1 cells. In OCI/AML-6 cells, Delta-1 stimulation decreased the expression of CD11b and CD14 and increased CD34 expression. Namely, Delta-1 showed the opposite effects on the differentiation markers of each cell line. Delta-1 stimulation did not increase the binding of annexin V, a marker for apoptotic cells in either cell line. Since the growth of myeloid cells is regulated by MAP kinase and JAK/STAT pathways, we investigated the effects of the ligand stimulation on these pathways. Delta-1 stimulation did not induce the phosphorylation of ERK1/2 and STAT3 proteins in either cell line. Pre-exposure to Delta-1 did not affect the phosphorylation of ERK1/2 and STAT3 induced by G-CSF in OCI/AML-6 cells, either. Namely, it is thought that these pathways are not involved in the growth suppression caused by Notch ligands. Our study revealed several findings on Notch function. However, the precise mechanism remains to be elucidated.

Hematological findings in SARS patients and possible mechanisms (review)

Severe acute respiratory syndrome (SARS) is a new human infectious disease. The causative agent of SARS is a novel coronavirus (SARS-CoV). This report summarizes the hematological findings in SARS patients and proposes the possible mechanisms of SARS-CoV related abnormal hematopoiesis. Hematological changes in patients with SARS are common and include lymphopenia, thrombocytopenia and occasionally leukopenia. A significant decrease was also observed in peripheral CD4+ and CD8+ T lymphocyte subsets and it was related to onset of SARS. A number of potential mechanisms may be involved. The development of auto-immune antibodies or immune complexes triggered by viral infection may play a major role in inducing lymphopenia and thrombocytopenia. Moreover, SARS-CoV may also directly infect hematopoietic stem/progenitor cells via CD13 or CD66a inducing their growth inhibition and apoptosis. The receptor for group I and III CoV is aminopeptidase N (CD13). CD13 has been identified in human bone marrow CD34+ cells, platelets, megakaryocytes, myeloid cells, and erythroid cells, but not in lymphocytes. The common receptor for group II CoV is CEACAM1a (CD66a). CD66a is an adhesion molecule expressed on bone marrow CD34+ cells, platelets, granulocytes and activated lymphocytes. In addition, glucocorticoids could induce lymphopenia and the use of steroids may account for the decrease of lymphocytes in some SARS patients. The increased consumption of platelets and/or the decreased production of platelets in the damaged lungs are a potential alternative but often overlooked mechanism that can contribute to thrombocytopenia in severe critical pulmonary conditions.

Microgranular and t(11;17)/PLZF-RARalpha variants of acute promyelocytic leukemia also present the flow cytometric pattern of CD13, CD34, and CD15 expression characteristic of PML-RARalpha gene rearrangement

Acute promyelocytic leukemia (APL) is a subtype acute myeloid leukemia in which leukemic promyelocytes predominate in the bone marrow (BM). Rapid diagnosis is critical for treatment decision since all-trans-retinoic acid must be administrated promptly. The microgranular variant may be of difficult diagnosis, as it may be confused with other diseases on morphological grounds. The purpose of this study was to determine if the microgranular variant has the same antigenic profile as the classical hypergranular type. The immunophenotype of leukemic cells from the bone marrow of 50 patients, with the PML-RARalpha gene rearrangement confirmed by RT-PCR, was determined by flow cytometry using a large panel of 22 monoclonal antibodies and a polyclonal anti-TdT antibody. Thirty-four cases were classified as classical APL and 16 as microgranular APL. The immunophenotypic profile of the two subtypes was indistinguishable concerning the presence or absence of these antigens, including the absence of reactivity for the HLA-DR antigen. The simultaneous immunophenotypic combination of a unique major cell population, heterogeneous intensity of expression of CD13, and the typical pattern of CD15/CD34 expression were similarly present in the hypergranular and microgranular subtypes. Homogeneous expression of CD33 was observed in 76% of the classical APL cases and in 100% of the microgranular cases. Additionally, we have studied two cases of PLZF-RARalpha APL that also displayed the same immunophenotype described for classical APL. Thus, the immunophenotypic profile highly characteristic of the PML-RARalpha gene rearrangement was also observed in microgranular and PLZF-RARalpha variants of APL.

Strategies for improving the anti-neoplastic activity of TNF by tumor targeting

The clinical use of tumor necrosis factor (TNF) as an anticancer drug has been so far limited to loco-regional treatments because of severe dose-limiting toxicity. This chapter intends to review the targeting approaches and the animal models that have been developed in an attempt to improve the therapeutic activity of this cytokine and to enable systemic administration of a therapeutic dose. Using various animal models, evidence was obtained to suggest that the targeting approach could indeed improve the therapeutic properties of this cytokine, either alone or in combination with chemotherapy. Targeted delivery of TNF can be achieved by targeting tumor cell antigens, directly or indirectly by a pretargeting approach, or by targeting antigens expressed within tumor vessels. In both cases the mechanism of the improved antitumor activity appears to be related to indirect effects of TNF on tumor-associated vessels. Thus, targeting markers that are selectively expressed or upregulated in angiogenic tumor vessels seems to be the best choice for developing TNF conjugates with improved activity.

C-kit receptor expression in acute leukemias—association with patient and disease characteristics and with outcome

We hypothesize that c-kit expression may be associated with disease-specific features and have prognostic value in acute leukemias. In acute lymphocytic leukemia (ALL), higher levels of c-kit expression predicted lower complete response (CR) rates, suggesting that these patients may benefit from acute myelogenous leukemia (AML) therapy. Despite a negative association with the Philadelphia-chromosome, there was no correlation with disease-free survival (DFS) in CR. In AML, c-kit was associated with older age and cytogenetic abnormality t(-5, -7). Consequently higher levels of c-kit predicted lower CR rates. However, after accounting for these covariates, multivariate analysis indicates that higher c-kit expression predicts higher CR rates, although there was no effect on DFS in CR.

Expression of CD13/aminopeptidase N and CD10/neutral endopeptidase on cultured human keratinocytes

Keratinocytes actively participate in immune response and inflammation by secreting cytokines and chemokines. Membrane-bound peptidases serve as negative loop in controlling concentration of peptide signalling molecules. Recently, they have also been proposed as additional mechanism of cell-to-cell interaction and as signalling molecules. In this study, we examined expression of two membrane-bound peptidases: aminopeptidase N (APN; EC 3.4.11.2; CD13) and neutral endopeptidase (NEP; EC 3.4.24.11; CD10) on nonstimulated cultured human keratinocytes obtained from healthy skin. Membrane expression of CD13 and CD10 was analysed by FACS and fluorescent microscope. Functional properties of CD13 and CD10 were examined by testing their enzymatic activity towards selective substrates. The data were compared to those obtained on cultured nonstimulated human skin fibroblasts expressing both CD13/APN and CD10/NEP. Approximately one-third (i.e. 31.7+/-2.8%; n=3) of cultured keratinocyte express CD13 as compared to fibroblasts which are 100% CD13(+) (n=3). Density of CD13 on keratinocytes is several times lower than on fibroblasts. Membrane CD13 expression on keratinocytes was associated with significant enzyme activity, which on the basis of substrate (L-Ala-betaNA) and inhibitor (bestatin, actinonin) selectivity could be ascribed to aminopeptidase N. Kinetic parameter V(max) revealed lower APN activity expressed on keratinocytes than on fibroblasts (V(max)=1.49+/-0.08 microM/60 min/5 x 10(4) cells for keratinocytes, n=3 versus V(max)=4.09+/-0.76 microM/60 min/5 x 10(4) cells for fibroblasts, n=3). Likewise, K(m) value of APN on keratinocytes was lower as compared to fibroblasts (K(m)=0.307+/-0.090 mM for keratinocytes, n=3 versus K(m)=0.766+/-0.065 mM for fibroblasts, n=3). CD13 demonstrated on cultured keratinocytes, is at least partly due to its constitutive expression since it was also found on freshly prepared epidermal skin cells. Inhibitors of APN, actinonin, bestatin and substance-P, as well as the APN blocking antibody WM-15, decreased keratinocytes growth. In contrast to membrane CD13 associated with APN enzyme activity, neither membrane CD10, nor its enzyme (NEP) activity could be found on the same keratinocyte samples. In conclusion, functional CD13, associated with APN activity, was found on about one third of cultured, non-stimulated keratinocytes, whereas no CD10/NEP was found on the same keratinocyte samples. Role of APN in regulation of keratinocyte growth is suggested, as its inhibition resulted in decreased keratinocyte growth.

In vitro targeted killing of human endothelial cells by co-incubation of human serum and NGR peptide conjugated human albumin protein bearing alpha (1-3) galactose epitopes

The NGR/alpha1,3Gal-HSA peptide was designed to specifically target CD13 positive cells and induce cell lysis. NGR is the targeting component of the peptide in that it binds the CD13 isoform (aminopeptidase) that is expressed in tumor vessels. Galactose alpha1,3-galactose terminal carbohydrate epitope (alpha1,3Gal) induces a strong antibody reaction in human and Old World Monkeys and in vivo, this reaction leads to organ rejection. The human serum albumin (HSA) bearing alpha1,3Gal epitope was therefore used to lyse cells. In the present study, we were able to demonstrate that NGR/alpha1,3Gal-HSA binds CD13 positive human umbilical vein endothelial cells (HUVEC). We also found by live/dead fluorescent staining that NGR/alpha1,3Gal-HSA was able to induce lysis of HUVECs upon incubation with human serum. Therefore, by conjugating NGR to HSA bearing alpha1,3Gal epitopes, we are able to specifically target and lyse cells expressing CD13. This strategy may be potentially useful in tumor anti-angiogenesis therapy.

Ectopeptidases are differentially expressed in hepatocellular carcinomas

We investigated the expression pattern of neprilysin (CD10), aminopeptidase N (CD13) and angiotensin-I converting enzyme (CD143) in hepatocellular carcinomas (HCC), and their putative roles in hepatocarcinogenesis. Tissue samples were obtained from 31 patients with HCC. Tissue samples obtained from non-neoplastic liver, fetal livers and focal nodular hyperplasias (FNH) were used by comparison. Transcription and expression of CD10, CD13, and CD143 were studied by quantitative RT-PCR, Western blotting, and immunohistochemistry. Cell proliferation assays were performed with the C3A hepatoma cell line. The mRNA and protein of each of CD10, CD13 and CD143 were differentially expressed in HCCs. CD10 was decreased in HCCs as compared to non-neoplastic liver tissue, while CD13 and CD143 were mildly increased. In fetal liver and FNHs, the expression of CD10 was less intense than in the surrounding non-tumorous liver. The expression patterns of CD13 and CD143 in fetal livers and FNHs were similar to HCCs and were predominantly localized in bile canaliculi (CD13) and endothelial cells (CD143). CD10 and CD13 mRNAs were expressed by C3A cells and blocking either CD10 or CD13 ectopeptidase activity retarded cell growth significantly in vitro. We demonstrate that ectopeptidases are differentially expressed in HCCs and may have influence on tumor biology. Overall, expression of CD10 in non-neoplastic and neoplastic hepatocytes appears to correlate inversely with their state of proliferation or differentiation. CD13 shows a characteristic canalicular distribution pattern and may be important for cell polarization and bile compartmentalization in HCCs, while CD143 may influence angiogenesis.

Biological significance of aminopeptidase N/CD13 in thyroid carcinomas

Aminopeptidase N (APN)/CD13 is a transmembrane ectopeptidase expressed on a wide variety of cells. However, the precise function of APN/CD13 in tumor cells and the relationship of APN/CD13 to thyroid cancer remain unclear. In our study, we quantified the expression of APN/CD13 and additionally dipeptidyl peptidase IV (DPIV)/CD26 in thyroid carcinoma cell lines and in tissues of patients with thyroid carcinomas. Undifferentiated anaplastic thyroid carcinomas expressed more APN/CD13 than differentiated thyroid carcinomas. DPIV/CD26 showed an opposite expression pattern. We detected higher levels of DPIV/CD26 in follicular thyroid carcinomas (FTCs) and papillary thyroid carcinomas than in undifferentiated anaplastic thyroid carcinomas. In the undifferentiated thyroid carcinoma cell line 1736, APN/CD13 mRNA expression could be increased by epidermal growth factor, basic fibroblast growth factor, interleukin-6, and tumor necrosis factor alpha. FTC-133 cells stably transfected with an expression vector for APN-enhanced green fluorescent protein showed a higher migration rate than FTC-133 cells transfected with the enhanced green fluorescent protein-control plasmid. Overexpression of APN/CD13 in stably transfected cells is associated with down-regulation of N-myc down-regulated gene (NDRG)-1, melanoma-associated antigen ME491/CD63, and DPIV/CD26 gene expression. Inhibition of APN/CD13 mRNA expression by small interfering RNA induced NDRG-1, ME491/CD63, and DPIV/CD26 mRNA expression in cells of the undifferentiated thyroid carcinoma cell line C643. We conclude that APN/CD13-associated down-regulation of NDRG-1, ME491/CD63, and DPIV/CD26 in thyroid carcinoma cells is an important step of tumor progression to more malignant phenotypes, and we underline the important role of APN/CD13 as mediator in a multimolecular process regulating cell migration.

Induction of CD13 on T-lymphocytes by adhesive interaction with gingival fibroblasts

Lymphocytes in peripheral blood do not express CD13 (aminopeptidase N), a membrane alanyl metallopeptidase. However, it has been demonstrated that locally infiltrated lymphocytes in chronic inflammatory sites can be CD13-positive, and possible involvement of stromal cell adherence in the induction of CD13 has been suggested. In this study, we examined whether T-lymphocyte/gingival-fibroblast interaction can activate T-lymphocytes to express CD13. CD13 expression was induced on PMA-activated T-lymphocytes only when they adhered directly to human gingival fibroblasts (HGF) at 2 hrs after the co-culture began, while an increase in the enzyme activity of CD13 was also confirmed in activated T-lymphocytes that had been co-cultured with HGF. Furthermore, CD13-positive T-lymphocytes were detected in inflamed gingival tissues in vivo. Analysis of these results indicates that direct interaction with HGF is essential for the induction of CD13 expression on T-lymphocytes that was also observed in periodontitis lesions.

Alternative splicing of the human cyclin D-binding Myb-like protein (hDMP1) yields a truncated protein isoform that alters macrophage differentiation patterns

We have cloned two novel, alternatively spliced messages of human cyclin D-binding Myb-like protein (hDMP1). The known, full-length protein has been named hDMP1alpha and the new isoforms, hDMP1beta and hDMP1gamma. The hDMP1alpha, -beta, and -gamma splice variants have unique expression patterns in normal hematopoietic cells; hDMP1beta mRNA transcripts are strongly expressed in quiescent CD34+ cells and freshly isolated peripheral blood leukocytes, as compared with hDMP1alpha. In contrast, activated T-cells and developing myeloid cells, macrophages, and granulocytes express low levels of hDMP1beta transcripts, and hDMP1gamma is ubiquitously and weakly expressed. Mouse Dmp1 has been shown to activate CD13/aminopeptidase N (APN) and p19ARF gene expression via binding to canonical DNA recognition sites in the respective promoters. Assessment of CD13/APN promoter responsiveness demonstrated that hDMP1alpha but not hDMP1beta and -gamma, is a transcriptional activator. Furthermore, hDMP1beta was found to inhibit the CD13/APN promoter transactivation ability of hDMP1alpha. Stable, ectopic expression of hDMP1beta and, to a lesser extent hDMP1gamma, reduced endogenous cell surface levels of CD13/APN in U937 cells. Moreover, stable, ectopic expression of hDMP1beta altered phorbol 12-myristate 13-acetate-induced terminal differentiation of U937 cells to macrophages and resulted in maintenance of proliferation. These results demonstrate that hDMP1beta antagonizes hDMP1alpha activity and suggest that cellular functions of hDMP1 may be regulated by cellular hDMP1 isoform levels.

Flow cytometric characterization of perfused human bone marrow cultures: identification of the major cell lineages and correlation with the CFU-GM assay

BACKGROUND

Prolific cultures of human bone marrow mononuclear cells (BM MNCs) were recently developed that include a full spectrum of hematopoietic and accessory cells, with the presence of autofluorescent cells indicating adequate cell expansion. However, phenotypic and functional clonogenic characterizations of the autofluorescent cells and the various other subpopulations present in these cultures have not been carried out.

METHODS

Cells from a continuously perfused bioreactor inoculated with BM MNCs and cultured for 12 days in serum-containing medium with PIXY321, erythropoietin, and with or without FLT3-L were evaluated by using flow cytometry.

RESULTS

Two antibodies, CD71 and CD13, allowed the separation of the autofluorescent cells into two distinct populations. The CD71+CD13++ autofluorescent population contained the colony-forming unit (CFU) fibroblast, and the CD71++CD13++ autofluorescent population contained macrophage/dendritic like cells. The CFU-granulocyte/macrophage (CFU-GM) could not be thoroughly evaluated with CD71 and CD13. However, the number of CD13+/++Lin- cells correlated with the number of CFU-GM (r = 0.83), with approximately 1 CFU-GM for every 30 CD13+/++Lin- cells.

CONCLUSIONS

The data showed that CD71 and CD13 antibodies separate the autofluorescent cells into two populations but do not separate hematopoietic cells into specific phenotypic populations. The data also showed that the number of CD13+/++Lin- cells correlated with the number of CFU-GM. These data present the initial step toward detailed phenotypic analysis of ex vivo expanded human BM MNC cultures.

Clinical significance of aminopeptidase N/CD13 expression in human pancreatic carcinoma

PURPOSE

We previously established a novel murine monoclonal antibody(MH8-11) that recognized aminopeptidase N (APN)/cluster of differentiation antigen 13 (CD13). This monoclonal antibody inhibited human umbilical vein endothelial cells migration and capillary-like tube formation of human umbilical vein endothelial cells on Matrigel. In this study, we investigated the expression of APN/CD13 and the intratumor microvessel density (IMD) as the number of microvessel counts in 50 patients with pancreatic carcinoma.

EXPERIMENTAL DESIGN

We investigated APN/CD13 gene expression using the reverse transcriptase-PCR. We also used immunohistochemistry with MH8-11 to investigate APN/CD13 protein expression. Moreover, we investigated the relationship between APN/CD13 expression and tumor angiogenesis by measuring the IMD.

RESULTS

APN/CD13 gene expression detected by reverse transcriptase-PCR was positive in 50.0% (25 of 50) of the tumors, and APN/CD13 protein positive was detected by immunohistochemistry in 48.0% (24 of 50). APN/CD13 gene expression agreed well with the immunohistochemical findings (90.0% concordance). APN/CD13 was also significantly associated with an increase of the IMD (r = 0.71, P = 0.0003). However, APN/CD13 expression was not associated with various prognostic factors. The median survival time of patients with APN/CD13 expression was significantly shorter than that of patients without APN/CD13 expression (P = 0.009), and multivariate analysis showed that the APN/CD13 status was a significant independent factor (P = 0.016).

CONCLUSIONS

Our data suggest that APN/CD13 may be a new prognostic marker for patients with pancreatic carcinoma and may have a relationship with the angiogenesis for this cancer.

The analogy in cell immunophenotype and parameters of cell cycle of ectopic thymus, normal thymus, and some acute lymphoblastic leukemia of T-phenotype

In our study we described the immunophenotypic characteristics of an ectopic thymus found in an eight month old male baby. Comparing with the results of normal thymic cells we did not found any difference or abnormalities in the phenotype. A brief discussion of theories of histogenesis and possible differential diagnosis of ectopic thymus is included. The most common immune pattern of both, ectopic and normal thymuses, was expression of TdT,CD7,cCD3,CD1 and dual CD4/CD8. Early results of immunological examination confirmed by histopathology stated the diagnosis of ectopic thymus and excluded other causes (infection, trauma, neoplasm and congenital abnormalities). The study of both, ectopic and normal thymic tissue provides a perfect model for comparative analysis of some T-acute lymphoblastic leukemia (T-ALL). Both, thymocytes and some cases of our T-ALL (20 of 48 examined T-ALL) had a specific late cortical T-cell phenotype. We observed new qualities of both, thymic cells and T-ALL cells of a late cortical phenotype that resulted in cell populations localized in the so-called "empty spaces", in fluorescence histograms, that might be discriminated from internal T-cell populations with normal antigen expression. An important sign of T-ALL in common is to display aberrant marker combinations and the tendency to drop specific normal T-cell antigens. Aberrant markers were present in our study in a phenotypic group of a late cortical T-ALL in 11 cases (55.0%) of the 20 studied. As aberrant markers we observed mostly CD10, CD34, HLA-DR and CD13. Furthermore, the tendency to drop specific normal T-cell markers could be recognized in one case of a late cortical T-ALL in the form of TCRab and TCRgd absence. DNA analysis did not reveal any changes in proliferation index either in thymocytes (normal or ectopic), or in T-ALL of a late cortical T-cell phenotype. Based on our findings the clinical utility of comparing the results obtained from the immunophenotypic characterization of healthy hematopoietic and leukemia cells can be concluded. An exact and early diagnosis of hematopoietic disorders (ectopic thymus, T-ALL and T-NHL) and identification of identical phenotypic patterns at different times (for more exact minimal residual disease detection during and after therapy) could be obtained.