The cellular localization of autotaxin impacts on its biological functions in human thyroid carcinoma cells.

Autotaxin (ATX/NPP2) shows a nucleotide pyrophosphatase/phosphodiesterase and lysophospholipase D (lysoPLD) activity and is a member of a family of structurally-related mammalian ecto-nucleotide pyrophosphate/phosphodiesterases (E-NPP1-3). ATX is unique among E-NPP as it is secreted and not membrane-bound as are NPP1 and -3. The ATX gene activity is significantly higher in undifferentiated anaplastic (UTC) as compared to follicular (FTC) and papillary thyroid carcinomas (PTC) or goiter tissues. ATX also enhances the motility of thyroid tumor cells. We bio-engineered stable transfectants of the human thyroid carcinoma cell line FTC-238 expressing either bioactively-secreted (sATX) or membrane-anchored ATX (mATX) to identify the biological functions of ATX which critically depend on the E-NPP member being secreted and provide insight into the effects of high local ATX concentrations and cellular responses. An increased cell motility was exclusively observed with FTC-238 sATX transfectants, whereas membrane-anchored ATX appeared to impair motility. We identified IL-1beta as an upstream suppressor of ATX expression in FTC-238, ATX-mediated motility in FTC-238 and stable transfectants, with IL-1beta having the strongest motility-suppressive effect on FTC-238 sATX clones. sATX and mATX strongly increased the anchorage-independent colony formation of FTC-238 but the size and number of colonies formed in the soft agar were significantly smaller in FTC-238 mATX versus the FTC-238 sATX clones. The cancer-testis antigen BAGE was identified as a novel target gene of ATX in FTC-238. Transcript levels for BAGE were 6-fold higher in FTC-238 mATX versus sATX clones. Increased BAGE transcript levels were also detected in tissues of patients with UTC versus FTC, PTC or goiter tissues. In summary, enhanced tumor cell motility and tumorigenic capacity critically depended on sATX in thyroid carcinoma cells. Irrespective of its compartmentalization, the cancer-testis antigen BAGE was identified as a novel target gene of ATX in FTC-238 and a potential new tissue marker in UTC tissues, which we had previously shown to express high levels of ATX.

Expression of neutral endopeptidase (NEP/CD10) on pancreatic tumor cell lines, pancreatitis and pancreatic tumor tissues.

Neutral endopeptidase (NEP/CD10) is a cell surface zinc metalloprotease cleaving peptide bounds on the amino terminus of hydrophobic amino acids and inactivating multiple physiologically active peptides. Loss or decrease in NEP/CD10 expression have been reported in many types of malignancies, but the role of NEP/CD10 in pancreatic carcinoma has not yet been identified. Using real-time RT-PCR, flow cytometry as well as immunohistochemistry, NEP/CD10 expression was quantified in both pancreatic carcinoma cell lines and in tumor specimens obtained from patients with primary pancreatic carcinomas. Three out of 8 pancreatic carcinoma cell lines exhibit heterogeneous NEP/CD10 expression levels: PATU-8988T expressed the highest NEP/CD10 levels, whereas HUP-T4 and HUP-T3 cells showed a moderate to low NEP/CD10 expression. NEP/CD10 immunoreactivity was found in 6 of 24 pancreatic ductal adenocarcinomas, but also in 3 of 6 tissues of patients with chronic pancreatitis. NEP/CD10 expression in pancreatic tumor lesions and cell lines was not associated with tumor grading and staging. Treatment of PATU-8988T cells with the histone deacetylase inhibitors sodium butyrate and valproic acid induced an increase of NEP/CD10 expression. This was accompanied by a reduced cell proliferation rate of PATU-8988T cells, which was increased by the addition of the enzyme activity inhibitors phosphoramidon and thiorphan. Thus, NEP/CD10 is differentially expressed in pancreatic tumors and might be involved in the proliferative activity of pancreatic cancer cells. However, further studies are needed to provide more detailed information of the role of NEP/CD10 under physiological and pathophysiological conditions of the pancreas.

Expression, regulation and function of autotaxin in thyroid carcinomas.

Autotaxin (ATX/NPP2) is a tumor cell motility-stimulating factor that displays both a nucleotide pyrophosphatase/phosphodiesterase activity and a recently described lysophospholipase D (lysoPLD) activity. The precise function of ATX in tumor cells and the role of ATX in thyroid carcinoma remains unclear. We have quantified ATX mRNA expression in thyroid carcinoma cell lines and in tissues of patients with thyroid carcinomas. ATX gene activity was significantly higher in undifferentiated anaplastic thyroid carcinoma cell lines (UTC) and tumor tissues as compared to follicular thyroid carcinoma (FTC) cell lines, FTC tissues or goiter tissues that were used as a control. In the thyroid carcinoma cell line 1736, EGF and bFGF stimulated ATX mRNA expression, whereas the cytokines IL-4, IL-1beta and TGF-beta reduced ATX transcriptional levels. FTC-133 cells, stably transfected with an expression vector for ATX, showed a higher lysoPLD activity, a higher proliferation rate and an increased migratory behavior. In addition, ATX also displayed a paracrine stimulatory effect on the motility of different thyroid carcinoma cell lines. Overexpression of ATX in the stably transfected FTC-133 resulted in down-regulation of CD54/ intercellular adhesion molecule-1 (ICAM-1) gene expression and augmented gene activity of the pro-angiogenic chemokine IL-8. We conclude that ATX may be regarded as a new tissue marker for undifferentiated human thyroid carcinoma cells. ATX increases the proliferation and migration of thyroid carcinoma cell lines and may also affect the angiogenic potential of thyroid carcinoma cells. Further studies are needed to provide insight into the role of ATX in the normal and neoplastic thyroid gland.

Meningioma: is there an association with human leukocyte antigens?

The expression of human leukocyte antigen (HLA) alleles plays an important role in the development and recurrence of benign and malignant diseases. Association of single HLA alleles or haplotypes with neoplastic processes has been investigated previously, and correlation between HLA and solid tumors, such as head and neck cancers or uterine cervical squamous epithelial lesions, were reported. However, there is no published data on the influence of the HLA system on the development of symptomatic cerebral meningioma, a mostly benign intracranial tumor of mesenchymal origin in adults. The present investigation is comparing the frequency of single HLA alleles and haplotypes in 81 adult Caucasian patients with symptomatic central nervous system meningiomas to that of 157 area- and race-matched healthy controls. Both standard serological and molecular genetic (PCR) techniques were used for HLA typing. Our results suggest an association between single HLA alleles and occurrence of clinically symptomatic meningioma. Patients with HLA-A*02 had a 2.5-fold increased risk of meningioma (P = 0.02), and those with HLA-DQB1*05 had a 1.8-fold increased risk of meningioma (P = 0.05). Conversely, HLA-A*01, -B*08, and -DRB1*03 were associated with a 0.4-, 0.5-, and 0.5-fold, respectively, decreased risk of meningioma (P = 0.008, P = 0.05, and P = 0.04). Moreover, the occurrence rate of combinations and estimated haplotypes containing these HLA alleles was strikingly different in meningioma patients compared with controls: significantly increased for the haplotypes HLA-A*02:DRB1*04 (P = 0.02, relative risk = 2.5) and HLA-A*02:DRB1*04:DQB1*0302,DQB1*05 (P = 0.03, RR = 7.5), and significantly decreased for the haplotype HLA-A*01:B*08:DRB1*03 (P = 0.01, relative risk = 0.2). In conclusion, these data suggest that some single HLA alleles and haplotypes may protect from or predispose to developing symptomatic central nervous system meningioma during adult life. These associations may be indicative of the involvement of the immune system in the host antitumor surveillance, recognition, and destruction of de novo arising human tumor cells.

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.

Influence of spacer length on interaction of mannosylated liposomes with human phagocytic cells.

PURPOSE: To improve target specificity and uptake of liposomes by macrophages, one can improve high-affinity receptor binding to mannose determinants with their 175-kDa mannose receptor (MR), which is mainly influenced by the length and flexibility of the spacer between the carbohydrate head group and liposome surface. Liposomes containing alkylmannosides with hydrophilic spacers 0 to 8 ethyleneoxy units (EO) long (Man0...Man8) were used to investigate systematically the effects of spacer length on liposome-cell interactions. METHODS: Concanavalin A (ConA)-induced liposome aggregation was studied by turbidity measurement and cell uptake using PMA-induced HL-60 cells or native human macrophages by determining 6-CF after cell lysis or NBD-fluorescence with flow cytometry. Detection of MR in native cell populations was carried out by an antibody assay using flow cytometry; MR-representing cells were selected analytically. RESULTS: Liposomes containing mannosides with more than one EO spacer length were specifically aggregated by ConA, indicating accessibility of the carbohydrate ligands of these derivatives. Increase in EO spacer units of incorporated mannosides (two or more EO) led to suppression of cellular uptake of mannosylated liposomes by phagocytes lacking MR (HL60, U937). The extent of suppression increased with spacer length. Liposome uptake by native macrophages expressing MR was, on the contrary, improved, particularly by Man6 and Man8. CONCLUSIONS: Uptake of liposomes modified with Man6 or Man8 by native cells was enhanced but did not reach an optimum. Thus, Man6, Man8, and mannosides with even longer spacer arms are of potential use in receptor-mediated targeting.

Two C-terminal cysteines are necessary for proper folding of the peptidase neprilysin/CD10.

Neprilysin (NEP) consists of 749 amino acids with two conserved cysteines (734, 746) and a putative CAAX motif (residues 746-749, CRVW) at the C-terminus. To investigate the role of the C-terminal conserved cysteine residues, three NEP mutants (C734S, C746S, and double mutant C734S/C746S) were constructed by use of site-directed mutagenesis. Western blot analysis of lysates of transfected cells revealed the presence of three NEP forms in wild type and mutants with a different glycosylation pattern. Point mutations of C734 as well as C746 by serine dramatically diminished the plasma membrane association of NEP as detected by flow cytometry and laser scanning microscopy. Endoprotease enzyme activity was slightly diminished in the C746S-NEP variant and was not detectable in the C734S-form of NEP suggesting a pivotal role of the C734 in the proper folding of the enzyme. Prenylation of NEP was not detected in an in vivo assay.

Cell cycle retardation in monocytoid cells induced by aminopeptidase N (CD13).

Aminopeptidase N (APN, CD13) is highly expressed on human monocytes. Activation of leucocyte subpopulations, such as T-cells, can induce CD13 expression. However, little is known about the physiological role of CD13 expression on human leucocytes. It was suggested that CD13, similar to other peptidases, could be involved in control of cell growth. The hypothesis that CD13 influences proliferation of monocytoid cells by retarding the velocity of the cell cycle was tested. It was shown that CD13 expression was modulated within the cell cycle. Cells entering the S-phase of cell cycle decreased their CD13 surface expression. Occupation of the active center of CD13 with artificial ligands such as monoclonal antibodies (mab) or the low molecular weight inhibitor actinonin induced a prolongation of cell cycle and decreased the rate of cell growth. Additionally, after ligation of CD13 by mab the complex of CD13 and monoclonal antibody was actively internalized into the cell. We suggest that CD13 could have important functions for the proliferation of human monocytoid cells. Here we show for the first time that occupation of the CD13 active center by antibodies or inhibitors influences the cell cycle and thereby diminishes cell growth rate. Occupation of the active center by antibodies or inhibitors might prevent cleavage or binding and internalization of still unknown natural substrate(s) and could evoke a deceleration of the cell cycle and reduced cell growth rate.