Lipocalins and cancer

Neutrophil gelatinase-associated lipocalin immunoexpression in colorectal carcinoma: A stage-specific prognostic factor?

TNM post-surgical staging is considered to be one of the most powerful prognosticators for colorectal carcinoma. Although patient survival mostly decreases concomitantly to stage increase, in a percentage of cases TNM stage appears only to express the anatomic extent of the neoplasia with no correlation with clinical outcome. Thus, the identification of additional prognostic markers for colorectal cancer is required. Neutrophil gelatinase-associated lipocalin (NGAL) is a 25-kDa protein that appears to play an important role in colorectal cancer progression. In order to evaluate whether NGAL expression may be considered as a predictor of colorectal cancer progression, we analyzed its correlation with clinicopathological characteristics, as well as with patient progression-free survival in a series of surgically resected colorectal carcinomas. A variable NGAL immunoexpression was found in 24 out of the 64 analyzed cases. When only the positive cases were considered, a significant association was found between a high NGAL expression and the presence of distant metastases or high tumor stage. In addition, the presence of NGAL was a significant negative prognostic marker correlated with a shorter progression-free survival in stage I colorectal carcinoma, but not in the remaining TNM stages. If our findings are confirmed in more extensive analyses on stage I colorectal carcinoma, NGAL assessment may be used in order to select those patients with a higher progression risk and to submit them to adjuvant therapies useful to prevent adverse outcome.

Up-regulation of lipocalin 2 is associated with high-risk human papillomavirus and grade of cervical lesion at baseline but does not predict outcomes of infections or incident cervical intraepithelial neoplasia

Our objective was to assess whether neutrophil gelatinase-associated lipocalin (NGAL)/lipocalin 2 (LCN2) expression in cervical human papillomavirus (HPV) lesions has implications on the outcome of HPV infections or disease progression. Cervical biopsy specimens from 225 women in the Latin American Screening study were analyzed for NGAL/LCN2 expression using immunohistochemical analysis, to assess associations with cervical intraepithelial neoplasia (CIN) grade, high-risk HPV, and in predicting outcomes of high-risk (HR)-HPV infections. Expression of NGAL/LCN2 increased with lesion grade (odds ratio [OR], 3.86; 95% confidence interval [CI], 1.53-9.71; P = .001). Up-regulation was also related to HR-HPV detection (OR, 2.21; 95% CI, 1.15-4.24; P = .016) and showed a linear relationship to HR-HPV load (P = .002). NGAL/LCN2 expression was of no value in predicting the outcomes of HR-HPV infections or the surrogate end points (incident CIN 1+ and CIN 2+) of progressive disease. Because the SV40 large T antigen is a powerful up-regulator of this lipocalin, up-regulation of NGAL/LCN2 in CIN is probably induced by HR-HPV E6 oncoprotein, most likely by eliminating its normal transcription repression exerted by wild-type p53.

Identification of lipocalin and apolipoprotein A1 as biomarkers of chronic obstructive pulmonary disease

RATIONALE

Much effort is being made to discover noninvasive biomarkers of chronic airway disease that might enable better management, predict prognosis, and provide new therapeutic targets.

OBJECTIVES

To undertake a comprehensive, unbiased proteomic analysis of induced sputum and identify novel noninvasive biomarkers for chronic obstructive pulmonary disease (COPD).

METHODS

Induced sputum was obtained from patients with COPD with a spectrum of disease severity and from control subjects. Two-dimensional gel electrophoresis and mass spectrometric identification of differentially expressed proteins were first applied to induced sputum from patients with GOLD stage 2 COPD and healthy smoker control subjects. Initial results thus obtained were validated by a combination of immunoassays (Western blotting and ELISA) applied to a large subject cohort. The biomarkers were localized to bronchial mucosa by immunohistochemistry.

MEASUREMENTS AND MAIN RESULTS

Of 1,325 individual protein spots identified, 37 were quantitatively and 3 qualitatively different between the two groups (P < 0.05%). Forty protein spots were subjected to tandem mass spectrometry, which identified 15 separate protein species. Seven of these were further quantified in induced sputum from 97 individuals. Using this sequential approach, two of these potential biomarkers (apolipoprotein A1 and lipocalin-1) were found to be significantly reduced in patients with COPD when compared with healthy smokers. Their levels correlated with FEV(1)/FVC, indicating their relationship to disease severity.

CONCLUSIONS

A potential role for apolipoprotein A1 and lipocalin-1 in innate defense has been postulated previously; our discovery of their reduction in COPD indicates a deficient innate defense system in airway disease that could explain increased susceptibility to infectious exacerbations.

Hepatocellular carcinoma: prevalence and molecular pathogenesis of Helicobacter spp

Helicobacter pylori infection is one of the most common chronic bacterial infections in humans. The association of other Helicobacter spp. with extragastric diseases in animals is well established, and a role of these bacteria in human liver disease is becoming clearer. Several case-control studies have reported possible associations of Helicobacter spp. with various liver diseases, including hepatocellular carcinoma, which is the fifth most common type of carcinoma among men worldwide, and the eighth most common among women. Thus, it is important to understand molecular mechanisms that may lead to hepatotoxicity or hepatocellular dysfunction in which Helicobacter spp. may play a role in inducing malignant transformation of liver cells.

Neutrophil gelatinase-associated lipocalin (NGAL) in human neoplasias: a new protein enters the scene

The small 25 kDa peptide, neutrophil gelatinase-associated lipocalin (NGAL), first known as an antibacterial factor of natural immunity, and an acute phase protein, is currently one of the most interesting and enigmatic proteins involved in the process of tumor development. The aim of the present review is to point out the main contradictory, sometimes even paradoxical, effects attributed to NGAL in human neoplasias. For instance, acting as an intracellular iron carrier and protecting MMP9 from proteolytic degradation, NGAL has a clear pro-tumoral effect, as has already been observed in different tumors (e.g. breast, stomach, oesophagus, brain) in humans. Moreover, in thyroid carcinomas, NGAL is strongly induced by NF-kB, an important factor involved both in tumor growth and in the link between chronic inflammation and neoplastic development. However, on the contrary, some studies have demonstrated that NGAL can inhibit the pro-neoplastic factor HIF-1alpha, FA-Kinase phosphorylation and also VEGF synthesis, thus suggesting that, in alternative conditions, NGAL also, paradoxically, has an anti-tumoral and anti-metastatic effect in neoplasias of, for example, the colon, ovary and pancreas. Finally, in the field of clinical oncology, attention is currently focused on the potential use of NGAL levels in making an early diagnosis, establishing a prognosis and predicting response to different treatments.

Lipocalin 2 promotes breast cancer progression

Here, we report that lipocalin 2 (Lcn2) promotes breast cancer progression, and we identify the mechanisms underlying this function. We first found that Lcn2 levels were consistently associated with invasive breast cancer in human tissue and urine samples. To investigate the function of Lcn2 in breast cancer progression, Lcn2 was overexpressed in human breast cancer cells and was found to up-regulate mesenchymal markers, including vimentin and fibronectin, down-regulate the epithelial marker E-cadherin, and significantly increase cell motility and invasiveness. These changes in marker expression and cell motility are hallmarks of an epithelial to mesenchymal transition (EMT). In contrast, Lcn2 silencing in aggressive breast cancer cells inhibited cell migration and the mesenchymal phenotype. Furthermore, reduced expression of estrogen receptor (ER) alpha and increased expression of the key EMT transcription factor Slug were observed with Lcn2 expression. Overexpression of ERalpha in Lcn2-expressing cells reversed the EMT and reduced Slug expression, suggesting that ERalpha negatively regulates Lcn2-induced EMT. Finally, orthotopic studies demonstrated that Lcn2-expressing breast tumors displayed a poorly differentiated phenotype and showed increased local tumor invasion and lymph node metastasis. Taken together, these in vitro, in vivo, and human studies demonstrate that Lcn2 promotes breast cancer progression by inducing EMT through the ERalpha/Slug axis and may be a useful biomarker of breast cancer.

The myxoid liposarcoma FUS-DDIT3 fusion oncoprotein deregulates NF-kappaB target genes by interaction with NFKBIZ

FUS (also called TLS), EWSR1 and TAF15 (also called TAF2N) are related genes involved in tumor type-specific fusion oncogenes in human malignancies. The FUS-DDIT3 fusion oncogene results from a t(12;16)(q13;p11) chromosome translocation and has a causative role in the initiation of myxoid/round cell liposarcomas (MLS/RCLS). The FUS-DDIT3 protein induces increased expression of the CAAT/enhancer-binding protein (C/EBP) and nuclear factor-kappaB (NF-kappaB)-controlled gene IL8, and the N-terminal FUS part is required for this activation. Chromatin immunoprecipitation analysis showed that FUS-DDIT3 binds the IL8 promoter. Expression studies of the IL8 promoter harboring a C/EBP-NF-kappaB composite site pinpointed the importance of NF-kappaB for IL8 expression in FUS-DDIT3-expressing cells. We therefore probed for possible interaction of FUS-DDIT3 with members of the NF-kappaB family. The nuclear factor NFKBIZ colocalizes with FUS-DDIT3 in nuclear structures, and immunoprecipitation experiments showed that FUS-DDIT3 binds the C-terminal of NFKBIZ. We also report that additional NF-kappaB-controlled genes are upregulated at the mRNA level in FUS-DDIT3-expressing cell lines and they can be induced by NFKBIZ. Taken together, the results indicate that FUS-DDIT3 deregulates some NF-kappaB-controlled genes through interactions with NFKBIZ. Similar mechanisms may be a part of the transformation process in other tumor types carrying FUS, EWSR1 and TAF15 containing fusion oncogenes.

Endometrial gene expression in early pregnancy: lessons from human ectopic pregnancy

Human endometrium undergoes modifications in preparation for embryonic implantation. This study investigated in vivo the endocrine effects of pregnancy on the endometrium, using the model of ectopic pregnancy. Endometrial biopsies from 9 subjects with ectopic pregnancy (Preg) were compared with 8 and 6 samples of mid and late secretory endometrium, respectively. After hybridizing with Affymetrix HGU133 Plus 2 chips, data were analyzed using GeneSpring GX and Ingenuity Pathways Analysis. From 54,675 genes, 3021 genes were significantly differentiated when mid-secretory endometrium was compared with the Preg (Volcano plot; P < .05, >or=2-fold change).The complement and coagulation cascade, phospholid degradation, glycosphingolipid biosynthesis (globoseries), retinol metabolism, antigen presentation pathway, glycosphingolipid biosynthesis, and O-glycan biosynthesis were main significant canonical pathways found in Preg samples. Validation was done with reverse transcriptase polymerase chain reaction. In conclusion, the ectopic embryo has a significant impact, by an endocrine mechanism, on endometrium, when compared with the window of implantation.

Early diagnosis of pancreatic cancer: neutrophil gelatinase-associated lipocalin as a marker of pancreatic intraepithelial neoplasia

Pancreatic cancer is a highly lethal malignancy with a dismal 5-year survival of less than 5%. The scarcity of early biomarkers has considerably hindered our ability to launch preventive measures for this malignancy in a timely manner. Neutrophil gelatinase-associated lipocalin (NGAL), a 24-kDa glycoprotein, was reported to be upregulated nearly 27-fold in pancreatic cancer cells compared to normal ductal cells in a microarray analysis. Given the need for biomarkers in the early diagnosis of pancreatic cancer, we investigated the expression of NGAL in tissues with the objective of examining if NGAL immunostaining could be used to identify foci of pancreatic intraepithelial neoplasia, premalignant lesions preceding invasive cancer. To examine a possible correlation between NGAL expression and the degree of differentiation, we also analysed NGAL levels in pancreatic cancer cell lines with varying grades of differentiation. Although NGAL expression was strongly upregulated in pancreatic cancer, and moderately in pancreatitis, only a weak expression could be detected in the healthy pancreas. The average composite score for adenocarcinoma (4.26+/-2.44) was significantly higher than that for the normal pancreas (1.0) or pancreatitis (1.0) (P<0.0001). Further, although both well- and moderately differentiated pancreatic cancer were positive for NGAL, poorly differentiated adenocarcinoma was uniformly negative. Importantly, NGAL expression was detected as early as the PanIN-1 stage, suggesting that it could be a marker of the earliest premalignant changes in the pancreas. Further, we examined NGAL levels in serum samples. Serum NGAL levels were above the cutoff for healthy individuals in 94% of pancreatic cancer and 62.5% each of acute and chronic pancreatitis samples. However, the difference between NGAL levels in pancreatitis and pancreatic cancer was not significant. A ROC curve analysis revealed that ELISA for NGAL is fairly accurate in distinguishing pancreatic cancer from non-cancer cases (area under curve=0.75). In conclusion, NGAL is highly expressed in early dysplastic lesions in the pancreas, suggesting a possible role as an early diagnostic marker for pancreatic cancer. Further, serum NGAL measurement could be investigated as a possible biomarker in pancreatitis and pancreatic adenocarcinoma.

Expression of neutrophil gelatinase-associated lipocalin in calcium-induced keratinocyte differentiation

In a previous search for the differentially expressed genes in keratinocyte differentiation, we identified neutrophil gelatinase-associated lipocalin (NGAL) as a calcium-induced gene. In this study, we further verified the expression of NGAL in cultured keratinocytes as well as in several skin diseases. Reverse transcription-polymerase chain reaction (RT-PCR), Western blot, and ELISA clearly showed that NGAL expression was markedly increased in calcium-induced keratinocyte differentiation in vitro. However, in our previous report, NGAL expression was not detected in normal skin tissue except for hair follicle by in situ hybridization and immunohistochemistry, indicating the difference of cell status between in vitro and in vitro conditions. Interestingly, NGAL expression was highly increased in psoriasis-like inflammatory disorders (lichen planus and pityriasis rubura pilaris) and skin cancers (keratoacanthoma and squamous cell carcinoma), implying that NGAL may be related with the epidermal hyperplasia. Collectively, these results reveal the potential importance of NGAL in the maintenance of skin homeostasis.

Lipocalin 2-mediated growth suppression is evident in human erythroid and monocyte/macrophage lineage cells

Lipocalin 2 (LCN2), a secreted protein of the lipocalin family, induces apoptosis in some types of cells and inhibits bacterial growth by sequestration of the iron-laden bacterial siderophore. We have recently reported that LCN2 inhibits the production of red blood cells in the mouse. Here we analyzed the role of LCN2 in human hematopoiesis. Expression of LCN2 was observed not only in mature cells such as those of the granulocyte/macrophage and erythroid lineages but also in hematopoietic stem/progenitor cells. We also examined expression of two candidate receptors for LCN2, brain type organic cation transporter (BOCT) and megalin, in various cell types. BOCT showed relatively high levels of expression in erythroid and hematopoietic stem/progenitor cells but lower levels in granulocyte/macrophage and T lymphoid cells. Megalin was expressed at high levels in T lymphoid and erythroid cells but at lower levels in granulocyte/macrophage lineage cells. LCN2 suppressed the growth of erythroid and monocyte/macrophage lineages in vitro, but did not have this effect on cells of other lineages. In addition, immature hematopoietic stem/progenitor cells were not sensitive to LCN2. These results demonstrate a lineage-specific role for LCN2 in human hematopoiesis that is reminiscent of its effects upon mouse hematopoiesis and strongly suggest an important in vivo function of LCN2 in the regulation of human hematopoiesis.

Transgenic expression of the forkhead box M1 transcription factor induces formation of lung tumors

The forkhead box m1 (Foxm1 or Foxm1b) protein (previously called HFH-11B, Trident, Win or MPP2) is abundantly expressed in human non-small cell lung cancers where it transcriptionally induces expression of genes essential for proliferation of tumor cells. In this study, we used Rosa26-Foxm1 transgenic mice, in which the Rosa26 promoter drives ubiquitous expression of Foxm1 transgene, to identify new signaling pathways regulated by Foxm1. Lung tumors were induced in Rosa26-Foxm1 mice using the 3-methylcholanthrene (MCA)/butylated hydroxytoluene (BHT) lung tumor initiation/promotion protocol. Tumors from MCA/BHT-treated Rosa26-Foxm1 mice displayed a significant increase in the number, size and DNA replication compared to wild-type mice. Elevated tumor formation in Rosa26-Foxm1 transgenic lungs was associated with persistent pulmonary inflammation, macrophage infiltration and increased expression of cyclooxygenase-2 (Cox-2), Cdc25C phosphatase, cyclin E2, chemokine ligands CXCL5, CXCL1 and CCL3, cathepsins and matrix metalloprotease-12. Cell culture experiments with A549 human lung adenocarcinoma cells demonstrated that depletion of Foxm1 by either short interfering RNA transfection or treatment with Foxm1-inhibiting ARF 26-44 peptide significantly reduced Cox-2 expression. In co-transfection experiments, Foxm1 protein-induced Cox-2 promoter activity and directly bound to the -2566/-2580 bp region of human Cox-2 promoter.

Gene expression profile of prostate cancer cell lines: effect of nerve growth factor treatment

A dysregulation of the nerve growth factor (NGF)-mediated control of prostate cell growth is associated with the malignant progression of prostate epithelial cells. Exogenous NGF induced in prostate cancer (PCa) cell lines DU145 and PC3 the expression of p75(NGFR), accompanied by a reduction of the cell malignancy. The aim of this study was to analyze the profile of NGF-regulated genes the PCa cell line DU145 by using the cDNA microarray technique. NGF treatment of DU145 cells decreased the expression of 52 known genes, while the expression of 40 known genes was increased. NGF treatment of the DU145 cell line modified the expression profile of clusters of genes involved in invasion and metastasis, in cell proliferation and apoptosis, inflammation, cell metabolism and transcriptional activity. Interestingly, NGF induced the same pattern of gene modifications in both PCa cell lines. Data presented here may help to identify gene/proteins that dispose to PCa progression and to assess future markers that could allow the development of new clinic diagnostic and therapeutical approaches.

DNMT3b overexpression contributes to a hypermethylator phenotype in human breast cancer cell lines

BACKGROUND

DNA hypermethylation events and other epimutations occur in many neoplasms, producing gene expression changes that contribute to neoplastic transformation, tumorigenesis, and tumor behavior. Some human cancers exhibit a hypermethylator phenotype, characterized by concurrent DNA methylation-dependent silencing of multiple genes. To determine if a hypermethylation defect occurs in breast cancer, the expression profile and promoter methylation status of methylation-sensitive genes were evaluated among breast cancer cell lines.

RESULTS

The relationship between gene expression (assessed by RT-PCR and quantitative real-time PCR), promoter methylation (assessed by methylation-specific PCR, bisulfite sequencing, and 5-aza-2'deoxycytidine treatment), and the DNA methyltransferase machinery (total DNMT activity and expression of DNMT1, DNMT3a, and DNMT3b proteins) were examined in 12 breast cancer cell lines. Unsupervised cluster analysis of the expression of 64 methylation-sensitive genes revealed two groups of cell lines that possess distinct methylation signatures: (i) hypermethylator cell lines, and (ii) low-frequency methylator cell lines. The hypermethylator cell lines are characterized by high rates of concurrent methylation of six genes (CDH1, CEACAM6, CST6, ESR1, LCN2, SCNN1A), whereas the low-frequency methylator cell lines do not methylate these genes. Hypermethylator cell lines coordinately overexpress total DNMT activity and DNMT3b protein levels compared to normal breast epithelial cells. In contrast, most low-frequency methylator cell lines possess DNMT activity and protein levels that are indistinguishable from normal. Microarray data mining identified a strong cluster of primary breast tumors that express the hypermethylation signature defined by CDH1, CEACAM6, CST6, ESR1, LCN2, and SCNN1A. This subset of breast cancers represents 18/88 (20%) tumors in the dataset analyzed, and 100% of these tumors were classified as basal-like, suggesting that the hypermethylator defect cosegregates with poor prognosis breast cancers.

CONCLUSION

These observations combine to strongly suggest that: (a) a subset of breast cancer cell lines express a hypermethylator phenotype, (b) the hypermethylation defect in these breast cancer cell lines is related to aberrant overexpression of DNMT activity, (c) overexpression of DNMT3b protein significantly contributes to the elevated DNMT activity observed in tumor cells expressing this phenotype, and (d) the six-gene hypermethylator signature characterized in breast cancer cell lines defines a distinct cluster of primary basal-like breast cancers.

Co-expression by keratinocytes of migration stimulating factor (MSF) and a functional inhibitor of its bioactivity (MSFI)

Migration stimulating factor (MSF) is a potent autocrine and paracrine factor expressed by fibroblasts and epithelial cells in foetal skin, tumours and healing wounds. In tissue culture, MSF bioactivity is present in the conditioned medium of foetal and tumour derived fibroblasts, but not in normal adult fibroblasts or keratinocytes. The conditioned medium of early passage keratinocytes or a keratinocyte line (HaCaT) effectively inhibited the motogenic activity of rhMSF. Fractionation of keratinocyte conditioned medium by size-exclusion chromatography revealed the presence of bioactive MSF as well as a functional inhibitor of MSF (MSFI) in fractions corresponding to approximately 70 kDa and 25 kDa, respectively. MSFI was purified and identified as neutrophil gelatinase-associated lipocalin (NGAL or lipocalin-2). Immunostaining confirmed that keratinocytes expressed both MSF and NGAL, whereas normal adult fibroblasts did not express either. Recombinant and cell-produced NGAL neutralised the motogenic activity of rhMSF. NGAL is known to bind MMP-9 and promote the activity of this protease. In contrast, there was no evidence of NGAL-MSF binding in keratinocyte conditioned medium. MSF displays a number of bioactivities of relevance to cancer progression and wound healing. Our findings indicate a novel function of NGAL and a possible mechanism for regulating MSF activity in tissues.

Use of high density antibody arrays to validate and discover cancer serum biomarkers

Perhaps the greatest barrier to translation of serum biomarker discoveries is the inability to evaluate putative biomarkers in high throughput validation studies. Here we report on the development, production, and implementation of a high-density antibody microarray used to evaluate large numbers of candidate ovarian cancer serum biomarkers. The platform was shown to be useful for evaluation of individual antibodies for comparative analysis, such as with disease classification, and biomarker validation and discovery. We demonstrate its performance by showing that known tumor markers behave as expected. We also identify several promising biomarkers from a candidate list and generate hypotheses to support new discovery studies.

Neutrophil gelatinase-associated lipocalin (NGAL) an early-screening biomarker for ovarian cancer: NGAL is associated with epidermal growth factor-induced epithelio-mesenchymal transition

The expression of neutrophil gelatinase-associated lipocalin (NGAL) has been shown to be upregulated in ovarian cancer cells. In this study, we report that the expression of immunoreactive NGAL (irNGAL) in ovarian tumors changes with disease grade and that this change is reflected in the concentration of NGAL in peripheral blood. A total of 59 ovarian tissues including normal, benign, borderline malignant and grades 1, 2 and 3 malignant were analyzed using immunohistochemistry. irNGAL was not present in normal ovaries and the NGAL expression was weak to moderate in benign tissues. Both borderline and grade 1 tumors displayed the highest amount of NGAL expression with moderate to strong staining, whereas in grade 2 and 3 tumors, the extent of staining was significantly less (p < 0.01) and staining intensity was weak to moderate. Staining in all cases was confined to the epithelium. NGAL expression was analyzed by ELISA in 62 serum specimens from normal and different grades of cancer patients. Compared to control samples, the NGAL concentration was 2 and 2.6-fold higher in the serum of patients with benign tumors and cancer patients with grade 1 tumors (p < 0.05) and that result was consistent with the expression of NGAL performed by Western blot. NGAL expression was evaluated by Western blot in an immortalized normal ovarian cell line (IOSE29) as well as ovarian cancer cell lines. Moderate to strong expression of NGAL was observed in epithelial ovarian cancer cell lines SKOV3 and OVCA433 while no expression of NGAL was evident in normal IOSE29 and mesenchyme-like OVHS1, PEO.36 and HEY cell lines. NGAL expression was downregulated in ovarian cancer cell lines undergoing epithelio-mesenchymal transition (EMT) induced by epidermal growth factor (EGF). Downregulation of NGAL expression correlated with the upregulation of vimentin expression, enhanced cell dispersion and downregulation of E-cadherin expression, some of the hallmarks of EMT. EGF-induced EMT phenotypes were inhibited in the presence of AG1478, an inhibitor of EGF receptor tyrosine kinase activity. These data indicate that NGAL may be a good marker to monitor changes of benign to premalignant and malignant ovarian tumors and that the molecule may be involved in the progression of epithelial ovarian malignancies.

Regulation of lipocalin-2 gene by the cancer chemopreventive retinoid 4-HPR

N-(4-Hydroxyphenyl)retinamide (4-HPR) is a nonclassical retinoid with cancer preventive effects in vivo and antiproliferative and apoptotic activities in vitro. Examining the transcriptional profile of human breast cancer cell lines, MCF7 and T47D, treated with 4-HPR, we identified the lipocalin member LCN2 (NGAL or 24p3) as a gene, markedly induced by the retinoid. Because of its presumed function in apoptosis, LCN2 was examined more thoroughly in response to 4-HPR. Like mRNA, the expression of LCN2 protein in MCF7 and T47D cells was highly induced in a time-dependent manner by 4-HPR, but not by its inactive metabolite 4-MPR and, to some extent, this event was linked to the free radicals normally generated by 4-HPR. All-trans retinoic acid also induced LCN2 protein, particularly in T47D cells. Ectopic LCN2 compromised cell viability, and the few MCF7 clones that survived LCN2 overexpression were less sensitive than do mock cells to 4HPR, indicating that selective pressure for survival to LCN2 confers cross-resistance to 4-HPR. Significantly, ablation of LCN2 induction by siRNA did not modify the response to 4-HPR, implying that LCN2 is not critical for apoptosis by 4-HPR. Our results indicate that 4-HPR markedly induces LCN2 expression, but this event may not represent an apoptotic response.

Identification of biomarkers of human pancreatic adenocarcinomas by expression profiling and validation with gene expression analysis in endoscopic ultrasound-guided fine needle aspiration samples

AIM: To compare gene expression profiles of pancreatic adenocarcinoma tissue specimens, human pancreatic and colon adenocarcinoma and leukemia cell lines and normal pancreas samples in order to distinguish differentially expressed genes and to validate the differential expression of a subset of genes by quantitative real-time RT-PCR (RT-QPCR) in endoscopic ultrasound-guided fine needle aspiration (EUS-guided FNA) specimens.

METHODS: Commercially dedicated cancer cDNA macroarrays (Atlas Human Cancer 1.2) containing 1176 genes were used. Different statistical approaches (hierarchical clustering, principal component analysis (PCA) and SAM) were used to analyze the expression data. RT-QPCR and immunohistochemical studies were used for validation of results.

RESULTS: RT-QPCR validated the increased expression of LCN2 (lipocalin 2) and for the first time PLAT (tissue-type plasminogen activator or tPA) in malignant pancreas as compared with normal pancreas. Immunohistochemical analysis confirmed the increased expression of LCN2 protein localized in epithelial cells of ducts invaded by carcinoma. The analysis of PLAT and LCN2 transcripts in 12 samples obtained through EUS-guided FNA from patients with pancreatic adenocarcinoma showed significantly increased expression levels in comparison with those found in normal tissues, indicating that a sufficient amount of high quality RNA can be obtained with this technique.

CONCLUSION: Expression profiling is a useful method to identify biomarkers and potential target genes. Molecular analysis of EUS-guided FNA samples in pancreatic cancer appears as a valuable strategy for the diagnosis of pancreatic adenocarcinomas.

Ectopic expression of neutrophil gelatinase-associated lipocalin suppresses the invasion and liver metastasis of colon cancer cells

Neutrophil gelatinase-associated lipocalin (NGAL), also known as lipocalin 2, is a 25-kDa lipocalin initially purified from neutrophil granules. It is thought to play a role in regulating cellular growth since its expression is highly upregulated in a variety of proliferative cells such as cancer cells. However, experimental evidence showing a clear causal relationship between NGAL expression and the proliferation of tumor cells is lacking. Here, we found NGAL expression in highly and poorly metastatic colon cancer cell lines of the same genetic origin correlated inversely with the metastatic potential of these cells, which suggests NGAL participates in the metastatic process. To explore the role NGAL plays in tumor growth and metastasis, the KM12SM human colon cancer cell line, which is highly metastatic while showing decreased NGAL expression, was genetically manipulated to overexpress NGAL. The effects of this on tumor growth and liver metastasis were then analyzed using experimental animal models established by injecting BALB/c nude mice with tumor cells subcutaneously or intrasplenically. Ectopic expression of NGAL in the colon cancer cells had little effect on the growth and viability of the tumor cells both in vitro and in vivo. However, NGAL expression not only suppressed the ability of the colon carcinoma cells to invade Matrigel in vitro, it also substantially inhibited liver metastasis in an experimental animal model. Collectively, these results indicate that NGAL may be a candidate metastasis suppressor in colon cancer cells.

Role of the Na/H exchanger NHE1 in cell migration

Cell migration plays a basic role in many physiological and pathophysiological processes such as embryogenesis, immune defence, wound healing or metastasis. The activity of the ubiquitously expressed NHE1 isoform of the plasma membrane Na+/H+ exchanger is one of the requirements for directed locomotion of migrating cells and also contributes to cell adhesion. The mechanisms by which NHE1 is involved in cell migration are multiple. NHE1 contributes to cell migration by affecting the cell volume, by regulating the intracellular pH and thereby the assembly and activity of cytoskeletal elements, by anchoring the cytoskeleton to the plasma membrane, by signalling, by regulating gene expression and by controlling cell adhesion. The present article gives a review of the different ways in which NHE1 is involved in and contributes to cell migration. These different mechanisms complement one another forming an intricate, integrative process.

Neutrophil gelatinase-associated lipocalin as a survival factor

NGAL (human neutrophil gelatinase-associated lipocalin) and its mouse analogue 24p3 are members of the lipocalin family of small secreted proteins. These proteins are up-regulated in a number of pathological conditions, including cancers, and may function as transporters of essential factors. Although previous publications have suggested that 24p3 has pro-apoptotic functions, other data are more suggestive of a survival function. The current study was designed to determine whether NGAL is pro- or anti-apoptotic. Apoptosis induced in human adenocarcinoma A549 cells by the 5-lipoxygenase-activating-protein inhibitor MK886, or several celecoxib-derived PDK1 (phosphoinositide-dependent kinase 1) inhibitors that are devoid of cyclo-oxygenase-2 inhibitory activity, was accompanied by a dose- and time-dependent increase of NGAL mRNA levels, as was reported previously with 24p3. A similar induction of NGAL mRNA was observed in human breast cancer MCF7 cells treated with MK886, indicating this was not a cell-specific effect. Treatment of A549 cells with up to 150 mug/10(6) cells of purified recombinant NGAL protein had no effect on viability, whereas antisera against the full-length NGAL protein induced apoptosis in these cells. The stable overexpression of NGAL in A549 cells had no effect on proliferation or viability. However, the cell death induced by a PDK1 inhibitor was reduced by 50% in NGAL-overexpressing cells. Decreasing NGAL mRNA and protein expression with siRNA (small interfering RNA) in A549 cells increased the toxicity of a PDK1 inhibitor by approx. 45%. These data indicate that, although the induction of NGAL correlates with apoptosis, this induction represents a survival response. Because NGAL is a secreted protein, it may play an extracellular role in cell defence against toxicants and/or facilitate the survival of the remaining cells.

Lipocalin 2 functions as a negative regulator of red blood cell production in an autocrine fashion

Members of the lipocalin protein family are typically small, secreted proteins that possess a variety of functions. Although the physiological role of lipocalin 2 remains to be fully elucidated, a few pivotal functions have recently been reported, e.g., regulation of the apoptosis of leukocytes. Unexpectedly, lipocalin 2 is abundantly expressed in erythroid progenitor cells. An in vitro culture experiment demonstrated that lipocalin 2 induces apoptosis and inhibits differentiation of erythroid progenitor cells. During acute anemia the expression of lipocalin 2 was reduced in erythroid cells by a feedback system. Furthermore, injection of recombinant lipocalin 2 into mice suffering from acute anemia retarded the recovery of red blood cell (RBC) numbers, suggesting the importance of reduced expression of lipocalin 2 for the efficient recovery of RBC numbers. These results indicate that lipocalin 2 suppresses RBC production in an autocrine fashion. Hence, anemia arising from pathological conditions, such as chronic inflammation, might be partly due to increased levels of lipocalin 2 secreted from expanded leukocytes and/or macrophages. Also, anemia arising from malignancies might be partly due to the abundant secretion of lipocalin 2 from tumor cells. Thus, lipocalin 2 may represent an attractive therapeutic target for anemia under certain pathological conditions.

Gefitinib-responsive EGFR-positive colorectal cancers have different proteome profiles from non-responsive cell lines

Biomarkers that predict response to therapy with inhibitors of epidermal growth factor receptor (EGFR) tyrosine kinase remain largely uncharacterized. In order to define proteins involved in potential resistance mechanisms, we examined the effect of gefitinib (ZD1839, Iressa) in the EGFR-positive colon cancer cell lines Caco-2, DiFi, HRT-18 and HT-29. None of them exhibited an activating mutation in exons 19 or 21 of EGFR. Proteome profiling with two-dimensional polyacrylamide gel electrophoresis followed by mass spectrometry revealed 12 proteins differentially expressed in responsive and non-responsive cells. These proteins are involved in metabolic pathways, partially relevant in malignant growth and four of them are known to interact with the EGFR signalling pathway. Ubiquitin carboxyl-terminated hydrolase isozyme L1 (UCH-L1) and galectin-3 are overexpressed in the responsive cell line Caco-2, whereas fatty acid-binding protein (E-FABP) and heat shock protein (hsp) 27 are expressed more in the resistant cell lines HRT-18 and HT-29 suggesting a role in non-responsiveness of cells to gefitinib.

Microarray data analysis of mouse neoplasia

Microarray gene expression analysis offers great promise to help us understand the molecular events of experimental carcinogenesis, but have such promises been fulfilled? Studies of gene expression profiles of rodent are being published and demonstrate that yes, indeed, gene array data is furthering our understanding of tumor biology. Recent studies have identified differentially expressed genes in rodent mammary, colon, lung, and liver tumors. Although relatively few genes on the rodent arrays have been fully characterized, information has been generated to better identify signatures of histologic type and grade, understand invasion and metastasis, identify candidate biomarkers of early development, identify gene networks in carcinogenesis, understand responses to therapy, and decifer overlap with molecular events in human cancers. Data from mouse lung, mammary gland, and liver tumor studies are reviewed as examples of how to approach and interpret gene array data. Methods of gene array data analysis were also applied for discovery of genes involved in the regression of mouse liver tumors induced by chlordane, a nongenotoxic murine hepatocarcinogen. Promises are beginning to be fulfilled and it is clear that pathologists and toxicologists, in collaboration with molecular biologists, bioinformatists,and other scientists are making great strides in the design, analysis, and interpretation of microarray data for cancer studies.

Estradiol and medroxyprogesterone acetate regulated genes in T47D breast cancer cells

Many mammary tumors express estrogen receptors (ER) and progesterone receptors (PR), and there is increasing evidence that progestins influence gene expression of breast tumor cells. To analyse the impact of progestins on breast cancer cells, we compared (a) the expression of two cytokines, involved in tumor progression, and searched (b) for differentially regulated genes by a microarray, containing 2400 genes, on T47D breast cancer cells cultured for 6 days with 17beta-estradiol (E2) or E2+medroxyprogesterone acetate (E2+MPA). Lower amounts of PDGF and TNFalpha were found in culture supernatants of E2+MPA treated T47D cells. MPA addition induced a 2.8-3.5-fold increase of the mRNA expression of (a) tristetraprolin, which is involved in the posttranscriptional regulation of cytokine biosynthesis, and (b) zinc-alpha2-glycoprotein and Na, K-ATPase alpha1-subunit, which both resemble differentiation markers of breast epithelium. In contrast, the mRNA expression of lipocalin 2, which promotes matrixmetalloproteinase-9 activity, was decreased five-fold in E2+MPA treated cells. Our data show that the expression of genes from various functional gene families is regulated differentially by E2 and E2+MPA treatment in T47D cells. This suggests that exogenous progestins applied for therapy and endogenous changes of the progesterone levels during the menstrual cycle both influence breast cancer pathophysiology.

Lipocalin 2 diminishes invasiveness and metastasis of Ras-transformed cells

Lipocalin 2, an iron-siderophore-binding protein, converts embryonic kidney mesenchyme to epithelia. We found that lipocalin 2 could also convert 4T1-Ras-transformed mesenchymal tumor cells to an epithelial phenotype, increase E-cadherin expression, and suppress cell invasiveness in vitro and tumor growth and lung metastases in vivo. The Ras-MAPK pathway mediated the epithelial to mesenchymal transition in part by increasing E-cadherin phosphorylation and degradation. Lipocalin 2 antagonized these effects at a point upstream of Raf activation. Lipocalin 2 action was enhanced by iron-siderophore. These data characterize lipocalin 2 as an epithelial inducer in Ras malignancy and a suppressor of metastasis.

24p3 in differentiation of myeloid cells

24p3 is a secreted lipocalin that has been variously related to apoptosis, proliferation, and the neutrophil lineage of blood cells. We have investigated the expression of 24p3 mRNA and protein in myeloid cell lines induced to differentiate by insulin-like growth factor 1 (IGF-1) and the granulocytic-colony simulating factor (G-CSF). Both these growth factors, which cause myeloid cells to differentiate into granulocytes, induced a marked increase in the expression of both 24p3 protein and mRNA. The mRNA especially appeared early after the cells were induced with either IGF-1 or G-CSF, at a time when the cells were still proliferating and are morphologically undifferentiated. 24p3 can be considered an early marker of granulocytic differentiation.

Different proteome pattern of epidermal growth factor receptor–positive colorectal cancer cell lines that are responsive and nonresponsive to C225 antibody treatment

The monoclonal antibody C225 directed against the epidermal growth factor receptor (EGFR) blocks downstream mitogenic signaling and is effective in patients with advanced colorectal cancer. Clinical data, however, suggest the presence of primary and secondary resistance mechanisms that are hardly understood. To define proteins involved in EGFR-triggered growth regulation and potential resistance mechanisms, we characterized the proteome profile of two colorectal cancer cell lines with a high expression of functional EGFR but a different response to treatment with C225. In Caco-2 and HRT-18, a complete saturation of EGFR was achieved after incubation with C225; whereas Caco-2 showed inhibition of proliferation, growth of HRT-18 was not suppressed. Using two-dimensional electrophoresis and subsequent mass spectrometry, we identified 14 proteins differentially expressed in both cell lines. All proteins are involved in metabolic pathways and malignant growth. Expression of enzymes such as ubiquitin carboxyl-terminal hydrolase isozyme 1, glutathione S-transferase P, and chloride intracellular channel protein 1 does not seem to interfere with the antiproliferative effect of anti-EGFR antibody. On the other hand, expression of proteins such as fatty acid binding protein and heat shock protein 27 might constitute strong antiapoptotic effects contributing to the nonresponse of HRT-18 to C225 treatment. Proteome-based investigations can help us better understand the complex protein interactions involved in EGFR signaling and its blockage by therapeutic monoclonal antibodies.

Purification and characterization of pheromaxein, the porcine steroid-binding protein. A member of the secretoglobin superfamily

Low molecular mass proteins are implicated in chemical communication throughout mammalian species, being involved in both perception and delivery of pheromonal compounds. In boars, pheromones are secreted in saliva to cause oestrous sows to take up the mating stance. These pheromones are the 16-androstene steroids, 5alpha-androsten-3alpha-ol and 5alpha-androsten-3-one. The submaxillary glands of boars contain a low molecular mass protein, pheromaxein, which is capable of binding these 16-androstene pheromones. Pheromaxein was purified, cloned and characterized. It was found to be a nonglycosylated heterodimeric protein, belonging to the secretoglobin superfamily and the major 16-androstene-binding protein present in submaxillary salivary glands of the boar. One subunit, pheromaxein A, was found to be homologous to prostatein peptides, C1 and C2 and lipophilin A and B, whereas the other subunit, pheromaxein C, was homologous to prostatein peptide C3 and lipophilin C. Transcription of pheromaxein A was limited to the prostate and submaxillary salivary glands from both the boar and sow, whereas transcription of the other subunit, pheromaxein C, was more widespread. This is similar to the transcription distribution of lipophilin in humans. Many isoforms of pheromaxein were found to exist, with a molecular mass range of 17,415-18,159 Da; these are probably products of a multigene family. Post-translational modifications, to generate mature pheromaxein isoforms, probably include C-terminal cleavage of pheromaxein A, followed by additional modifications.

Expression profile of genes regulated by activity of the Na-H exchanger NHE1

BACKGROUND

In mammalian cells changes in intracellular pH (pHi), which are predominantly controlled by activity of plasma membrane ion exchangers, regulate a diverse range of normal and pathological cellular processes. How changes in pHi affect distinct cellular processes has primarily been determined by evaluating protein activities and we know little about how pHi regulates gene expression.

RESULTS

A global profile of genes regulated in mammalian fibroblasts by decreased pHi induced by impaired activity of the plasma membrane Na-H exchanger NHE1 was characterized by using cDNA microarrays. Analysis of selected genes by quantitative RT-PCR, TaqMan, and immunoblot analyses confirmed results obtained from cDNA arrays. Consistent with established roles of pHi and NHE1 activity in cell proliferation and oncogenic transformation, grouping regulated genes into functional categories and biological pathways indicated a predominant number of genes with altered expression were associated with growth factor signaling, oncogenesis, and cell cycle progression.

CONCLUSION

A comprehensive analysis of genes selectively regulated by pHi provides insight on candidate targets that might mediate established effects of pHi on a number of normal and pathological cell functions.

A proteomic analysis of human bile

We have carried out a comprehensive characterization of human bile to define the bile proteome. Our approach involved fractionation of bile by one-dimensional gel electrophoresis and lectin affinity chromatography followed by liquid chromatography tandem mass spectrometry. Overall, we identified 87 unique proteins, including several novel proteins as well as known proteins whose functions are unknown. A large majority of the identified proteins have not been previously described in bile. Using lectin affinity chromatography and enzymatically labeling of asparagine residues carrying glycan moieties by (18)O, we have identified a total of 33 glycosylation sites. The strategy described in this study should be generally applicable for a detailed proteomic analysis of most body fluids. In combination with "tagging" approaches for differential proteomics, our method could be used for identification of cancer biomarkers from any body fluid.

The role of matrix metalloproteinase 9 in the pathogenesis of chronic lymphocytic leukaemia

Matrix metalloproteinases (MMPs) are important for the pathogenesis and progression of different tumours. MMPs-2 and -9 are the principal MMPs produced by lymphocytes; these enzymes can degrade a number of matrix proteins but are the two main MMPs that digest type IV collagen, the major component of basement membranes. Therefore, these enzymes are potentially important for tissue invasion and remodelling by malignant lymphocytes. This study showed that chronic lymphocytic leukaemia (CLL) cells produce and secrete variable amounts of pro-MMP-9, but no MMP-2 or tissue inhibitor of metalloproteinase 1 (TIMP-1). The pro-enzyme was found in monomeric and dimeric forms and also complexed with lipocalin. Moreover, a small fraction of secreted monomer became associated with the cell surface and activated upon cell adhesion to insolubilized type IV collagen. High levels of intracellular MMP-9 were associated with advanced (stage C) disease and with poor patient survival. Immunohistochemical studies demonstrated that MMP-9 was associated with areas of tissue invasion and remodelling. The relatively specific MMP-9 inhibitors, Ro31-9790 (3 micromol/l) and TIMP-1, reduced CLL-cell migration through type IV collagen and through endothelial monolayers suggesting that the enzyme may also be important in malignant cell entry and egress to and from involved tissue. Our data raise the possibility that MMP-9 modulation may have therapeutic potential in advanced CLL.

Modulation of pro-inflammatory gene expression by nuclear lysophosphatidic acid receptor type-1

Lysophosphatidic acid (LPA) is a bioactive molecule involved in inflammation, immunity, wound healing, and neoplasia. Its pleiotropic actions arise presumably by interaction with their cell surface G protein-coupled receptors. Herein, the presence of the specific nuclear lysophosphatidic acid receptor-1 (LPA1R) was revealed in unstimulated porcine cerebral microvascular endothelial cells (pCMVECs), LPA1R stably transfected HTC4 rat hepatoma cells, and rat liver tissue using complementary approaches, including radioligand binding experiments, electron- and cryomicroscopy, cell fractionation, and immunoblotting with three distinct antibodies. Coimmunoprecipitation studies in enriched plasmalemmal fractions of unstimulated pCMVEC showed that LPA1Rs are dually sequestrated in caveolin-1 and clathrin subcompartments, whereas in nuclear fractions LPA1R appeared primarily in caveolae. Immunofluorescent assays using a cell-free isolated nuclear system confirmed LPA1R and caveolin-1 co-localization. In pCMVEC, LPA-stimulated increases in cyclooxygenase-2 and inducible nitric-oxide synthase RNA and protein expression were insensitive to caveolea-disrupting agents but sensitive to LPA-generating phospholipase A2 enzyme and tyrosine kinase inhibitors. Moreover, LPA-induced increases in Ca2+ transients and/or iNOS expression in highly purified rat liver nuclei were prevented by pertussis toxin, phosphoinositide 3-kinase/Akt inhibitor wortmannin and Ca2+ chelator and channel blockers EGTA and SK&F96365, respectively. This study describes for the first time the nucleus as a potential organelle for LPA intracrine signaling in the regulation of pro-inflammatory gene expression.

Cell Transformation by the v-myc Oncogene Abrogates c-Myc/Max-mediated Suppression of a C/EBPβ-dependent Lipocalin Gene

Using differential hybridization techniques, a cDNA clone (Q83) was isolated that corresponds to a highly abundant mRNA in quail embryo fibroblasts transformed by the v-myc oncogene. The deduced 178 amino acid protein product of Q83 contains an N-terminal signal sequence and a lipocalin sequence motif, the hallmark of a family of secretory proteins binding and transporting small hydrophobic molecules of diverse biological function, including retinoids and steroids. The quail Q83 protein displays 87% sequence identity with a developmentally regulated chicken protein, termed p20K or Ch21. Cell transformation specifically by v-myc, but not by other oncogenic agents, induces high-level expression of Q83 mRNA and of the Q83 protein. Nucleotide sequence analysis and transcriptional mapping revealed that the Q83 gene encompasses seven exons with the coding region confined to exons 1 through 6. The promoter region contains consensus binding sites for the transcriptional regulators Myc and C/EBP beta. Transcriptional activation of Q83 is principally dependent on C/EBP beta, but is blocked in normal cells by the endogenous c-Myc/Max/Mad transcription factor network. In v-myc-transformed cells, high-level expression of the v-Myc protein and formation of highly stable v-Myc/Max heterodimers leads to abrogation of Q83 gene suppression and activation by C/EBP beta. A 157 amino acid residue recombinant protein representing the secreted form of Q83 was used for structure determination by nuclear magnetic resonance spectroscopy. Q83 folds into a single globular domain of the lipocalin-type. The central part consists of an eight-stranded up-and-down beta-barrel core flanked by an N-terminal 3(10)-like helix and a C-terminal alpha-helix. The orientation of the C-terminal alpha-helix is partially determined by a disulfide bridge between Cys59 and Cys152. The three-dimensional structure determination of the Q83 protein will facilitate the identification of its authentic ligand and the assessment of its biological function, including the putative role in myc-induced cell transformation.

Increased expression of the lipocalin 24p3 as an apoptotic mechanism for MK886

MK886, a strong proapoptotic agent, is an inhibitor of 5-lipoxygenase (LOX) through binding to the 5-LOX-activating protein (FLAP). Although MK886-induced apoptosis is through a FLAP-independent pathway, the precise mechanisms are not understood. In the present study, a possible role of 24p3, a lipocalin, in MK886-induced apoptosis was investigated. Exposure of murine prolymphoid progenitor cells (FL5.12) to 20 microM MK886 for 16 h dramatically increased 24p3 mRNA and protein expression. Induction could also be achieved with another FLAP inhibitor, MK591. The induction of 24p3 by MK886 was dose- and time-dependent. The up-regulated 24p3 mRNA expression by MK886 was enhanced a further 3.1-fold by WY14643, an activator of peroxisome-proliferator-activated receptor alpha, whereas ciglitazone, an activator of peroxisome-proliferator-activated receptor gamma attenuated the MK886-induced 24p3 expression by more than 50%. Neither WY14643 nor ciglitazone alone had any effect on the expression of 24p3. The induction of 24p3 by MK886 was dependent on the synthesis of new protein(s), since cycloheximide, an inhibitor of protein synthesis, prevented this effect. In all cases, including the inhibition of MK886-induced 24p3 protein expression by stable transfection with antisense cDNA of 24p3, the extent of apoptosis closely paralleled 24p3 levels. Apoptosis induced by MK886, or enhanced by WY14643, was accompanied by the cleavage and activation of caspase-3. The overexpression of bcl-2 or bcl-x(L) in FL5.12 cells inhibited apoptosis induced by MK886 as well as the enhancement of apoptosis by WY14643. Thus 24p3 is an MK886-inducible gene and may play an important role in MK886-induced apoptosis.

Antisense down-regulation of lipocalin-interacting membrane receptor expression inhibits cellular internalization of lipocalin-1 in human NT2 cells

There is increasing experimental evidence demonstrating that many lipocalins bind to specific cell surface receptors. However, whereas the binding of lipocalins to their lipophilic ligands has now been characterized in much detail, there is a lack of knowledge about the nature of lipocalin receptors, the physiological role of receptor binding, and the molecular mechanism of ligand delivery. We previously identified a novel human membrane protein (lipocalin-1-interacting membrane receptor (LIMR)), which interacts with lipocalin-1 (Wojnar, P., Lechner, M., Merschak, P., and Redl, B. (2001) J. Biol. Chem. 276, 20206-20212). In the present study, we investigated the physiological role of LIMR and found this protein to be essential for mediating internalization of lipocalin-1 (Lcn-1) in NT2 cells, leading to its degradation. Whereas control NT2 cells rapidly internalized (125)I-Lcn-1 or fluorescein isothiocyanate-labeled Lcn-1, NT2 cells that were made LIMR deficient by cDNA antisense expression greatly accumulated Lcn-1 in the culture medium but did not internalize it. Because sequence and structure analysis indicated that proteins similar to LIMR are present in several organisms and at least two closely related orthologues are found in human and mouse, we suggest LIMR to be the prototype of a new family of endocytic receptors, which are topographically characterized by nine putative transmembrane domains and a characteristic large central cytoplasmic loop.

Native disulfide bonds in plasma retinol-binding protein are not essential for all-trans-retinol-binding activity

A human plasma retinol-binding protein (RBP) mutant, named RBP-S, has been designed and produced in which the six native cysteine residues, involved in the formation of three disulfide bonds, have been replaced with serine. A hexa-histidine tag was also added to the C-terminus of RBP for ease of purification. The removal of the disulfide bonds led to a decrease in the affinity of RBP for all trans-retinol. Data indicates all-trans-retinol binds RBP and RBP-S with Kd = 4 x 10(-8) M and 1 x 10(-7) M, respectively, at approximately 20 degrees C. RBP-S has reduced stability as compared to natural RBP below pH 8.0 and at room temperature. Circular dichroism in the far-UV shows that there is a relaxation of the RBP structure upon the removal of its disulfide bonds. Circular dichroism in the near-UV shows that in the absence of the disulfide bonds, the optical activity of RBP is higher in the 310-330 nm than in the 280-290 nm range. This work suggests that the three native disulfide bonds aid in the folding of RBP but are not essential to produce a soluble, active protein.

A chondrogenesis-related lipocalin cluster includes a third new gene, CALgamma

We have previously reported the modulation, during chondrogenesis and/or inflammation, of two chicken genes laying in the same genomic locus and coding for two polypeptides of the lipocalin protein family, the extracellular fatty acid binding protein (ExFABP) and the chondrogenesis associated lipocalin beta (CALbeta). A third gene, located within the same cluster and coding for a new lipocalin, CALgamma, has been identified and is here characterized. Tissue distribution analyzed by real-time quantitative reverse transcriptase-polymerase chain reaction in chicken embryos shows a ubiquitous expression with predominant levels of mRNA transcripts in the liver and the brain. In the developing tibia, a high expression of CALgamma mRNA was evidenced by in situ hybridization within the pre-hypertrophic and the hypertrophic zones of the bone-forming cartilage. In agreement, dedifferentiated chondrocytes in vitro express the transcripts to the highest level when they re-differentiate reaching hypertrophy. Such peculiar developmental pattern of expression that is analogous to those already described for Ex-FABP and CALbeta suggests that all three proteins may act synergistically in the process of endochondral bone formation. Moreover, like Ex-FABP and CALbeta, CALgamma is also highly induced in dedifferentiated chondrocytes upon stimulation with lypopolysaccharides, indicating that the whole cluster quite possibly is transcriptionally activated not only in physiological morphogenic differentiation but also in pathological acute phase response.

Genes that co-cluster with estrogen receptor alpha in microarray analysis of breast biopsies

The estrogen receptor plays a critical role in the pathogenesis and clinical behavior of breast cancer. To better understand the molecular basis of estrogen-dependent forms of this disease we studied gene expression profiles from 53 primary breast cancer biopsies. Gene expression data for more than 7000 genes were generated from each tumor sample with oligo microarrays. A standard correlation-clustering algorithm identified 18 genes that co-clustered with estrogen receptor alpha. Eleven of these genes had previously been associated with estrogen regulation or breast tumorigenesis including trefoil factor 1 and estrogen regulated LIV-1. Additional study of these 18 genes may further delineate the role of estrogen receptor in breast cancer, generate new predictive biomarkers for response to endocrine therapies and identify novel therapeutic targets.

CALbeta, a novel lipocalin associated with chondrogenesis and inflammation

We have previously demonstrated the association of the chicken lipocalin Ex-FABP with cartilage formation and inflammatory responses as a marker of these processes (Descalzi Cancedda et al., Biochim. Biophys. Acta 1482, 127-135, 2000). Here we report the isolation and characterisation of a new lipocalin gene laying upstream the Ex-FABP, thus representing the second member of a possible genomic cluster. This gene contains an open reading frame coding for a polypeptide of about 19 kDa. The amino-acid sequence revealed a conserved lipocalin secondary structure. Tissue distribution of the protein in developing embryos showed a preferential expression in the heart although mRNA transcripts could be detected also in muscle, lung and liver. The lowest expression was observed in the stomach, brain and skin. During endochondral formation of long bones, the protein is differentially distributed, as the transcripts, evidenced in the tibia by in situ hybridisation, are present in the hypertrophic cone of the cartilage and mostly absent in the area of the proliferating chondrocytes. Such developmental regulation was observed also in vitro in cultured chondrocytes where the transcripts were barely detectable in dedifferentiated cells but highly expressed in hypertrophic chondrocytes. The protein was also significantly induced by lipopolysaccharide stimulation of chondrocytes, indicating a possible involvement in acute phase response. Raising specific antibodies in a rabbit allowed validating, at the protein level, all the transcriptional data. Moreover, we gained evidence that the protein is actively secreted in the extracellular matrix surrounding the chondrocytes. Because of its peculiar expression in cartilage, this new protein was named chondrogenesis-associated lipocalin beta (thereafter referred to as CAL beta). The close similarity between Ex-FABP and CAL beta expression patterns supports the hypothesis of a genomic organisation in a cluster where both genes could be co-ordinately regulated.

Proposed lipocalin fold for apolipoprotein M based on bioinformatics and site-directed mutagenesis

Apolipoprotein M (apoM) is a novel apolipoprotein that is predominantly present in high-density lipoprotein. Sensitive sequence searches, threading and comparative model building experiments revealed apoM to be structurally related to the lipocalin protein family. In a 3D model, characterized by an eight-stranded anti-parallel beta-barrel, a segment including Asn135 could adopt a closed or open conformation. Using site-directed mutagenesis, we demonstrated Asn135 in wild-type apoM to be glycosylated, suggesting that the segment is solvent exposed. ApoM displays two strong acidic patches of potential functional importance, one around the N-terminus and the other next to the opening of the beta-barrel.