Expression of small breast epithelial mucin (SBEM) protein in tissue microarrays (TMAs) of primary invasive breast cancers.

AIMS: Small breast epithelial mucin (SBEM) is a recently described gene product that shows promise as a new breast biomarker. The aim was to investigate for the first time SBEM protein expression in a large cohort (n = 300) of invasive breast cancers, its relationship to established clinical variables and its association with clinical outcome. METHODS AND RESULTS: Immunohistochemical analysis was performed on tissue microarrays consisting of 149 oestrogen receptor (ER) alpha- and 151 ERalpha+ breast cancers. Overall, 18% of tumours were SBEM+ (n = 53/300). However, SBEM protein was more frequently observed in ER- (22%) than in ER+ cancers (13%; P = 0.049). A significant association with psoriasin/S100A7 expression (P < or = 0.0001) was observed in the entire cohort. SBEM was also positively associated with HER-2 (P = 0.046) in ER- cancers, and increased levels of SBEM were strongly associated with higher tumour grade (P = 0.0015). Furthermore, SBEM expression showed a trend towards an association with reduced overall survival and relapse-free survival in the ER+ cohort (P = 0.063 and P = 0.072, respectively). CONCLUSIONS: Our results suggest that SBEM may identify a unique subset of breast cancers with poor prognosis and may have future implications for therapeutic management of this disease.

Improved PCR method for amplification of GC-rich DNA sequences.

Most housekeeping genes, tumor-suppressor genes, and approx 40% of tissue-specific genes contain G+C sequences in their promoter region that were very difficult to amplify. In this report, we propose an improved polymerase chain reaction (PCR) method to be used for successful amplification of the tissue factor pathway inhibitor (TFPI)-2 gene promoter region that exhibit >70% G+C content in a sequence of approx 300 bp and a complete CpG island region spanning exon 1, the three transcription initiation sites, and the translation start site. Therefore, this method can be recommended to amplify other GC-rich genomic templates.

Expression and methylation status of tissue factor pathway inhibitor-2 gene in non-small-cell lung cancer.

Tissue factor pathway inhibitor-2 (TFPI-2) is a Kunitz-type serine proteinase inhibitor that inhibits plasmin-dependent activation of several metalloproteinases. Downregulation of TFPI-2 could thus enhance the invasive potential of neoplastic cells in several cancers, including lung cancer. In this study, TFPI-2 mRNA was measured using a real-time PCR method in tumours of 59 patients with non-small-cell lung cancer (NSCLC). Tumour TFPI-2 mRNA levels appeared well correlated with protein expression evaluated by immunohistochemistry and were 4-120 times lower compared to those of nonaffected lung tissue in 22 cases (37%). Hypermethylation of the TFPI-2 gene promoter was demonstrated by restriction enzyme-polymerase chain reaction in 12 of 40 cases of NSCLC (30%), including nine of 17 for whom tumour TFPI-2 gene expression was lower than in noncancerous tissue. In contrast, this epigenetic modification was shown in only three of 23 tumours in which no decrease in TFPI-2 synthesis was found (P=0.016). Decreased TFPI-2 gene expression and hypermethylation were more frequently associated with stages III or IV NSCLC (eight out of 10, P=0.02) and the TFPI-2 gene promoter was more frequently hypermethylated in patients with lymph node metastases (eight out of 16, P=0.02). These results suggest that silencing of the TFPI-2 gene by hypermethylation might contribute to tumour progression in NSCLC.

The steroid receptor RNA activator is the first functional RNA encoding a protein.

The steroid receptor RNA activator (SRA) has previously been characterized as belonging to the growing family of functional non-coding RNAs. However, we recently reported the Western blot detection of a putative endogenous SRA protein (SRAP) in breast cancer cells. Herein, we successfully suppressed the expression of this protein through specific RNA interference assay, unequivocally confirming its existence. Moreover, using database searches and Western blot analysis, we also showed that SRAP is highly conserved among chordata. Overall, our results suggest that SRA is the first example of a new class of functional RNAs also able to encode a protein.

Human small breast epithelial mucin: the promise of a new breast tumor biomarker.

Breast cancer remains one of the most frequently diagnosed cancers today. In developed countries, one in eight women is expected to present with breast cancer within her lifetime and an estimated 1,000,000 cases are detected each year worldwide (Canadian Cancer Statistics, http://www.cancer.ca/vgn/images/ portal/cit_86751114/14/33/1959864 11niw_stats2004_en.pdf). For women with recurrent disease, the median time of survival is about 2 years. Despite optimal surgery, adjuvant irradiation, hormonal treatment, and chemotherapy, approximately 30% of patients with localized breast cancer finally develop distant metastases. Early detection, which enables intervention at a localized and potentially curable stage, remains a central goal in breast cancer treatment. Indeed, the 5-year survival rate for women with breast cancer has been shown to increase dramatically when the disease is diagnosed at an early stage: from less than 25% in women with disseminated cancer to about 75% in patients with regional disease and over 95% in women with a localized tumor (Breast Cancer Facts and Figures, 2001-2002, http://www.cancer.org/downloads/STT/BrCaFF 2001.pdf). Unfortunately, only 60% of all breast cancers are diagnosed at a local stage. Any improvement in early detection through identification of tumor biomarkers would have a significant impact on reducing overall breast cancer mortality.

Characterization and functional analysis of TFPI-2 gene promoter in a human choriocarcinoma cell line.

Tissue factor pathway Inhibitor-2 (TFPI-2) is associated with extracellular matrices and plays a major role in cell migration and tumor invasion. In this study, a 4.8-kb human TFPI-2 gene 5'-flanking region was isolated, cloned and sequenced. Promoter region analysis revealed a high GC-rich content without canonical TATA and CAAT boxes but three transcription initiation sites were identified. Moreover, several putative binding sites for transcription factors were identified (MyoD, LYF1, NF-Y, GATA, oct-1, AP-1, Sp1, NF1, NF-kappa B and egr-1). To characterize potential regulatory regions, TFPI-2/luciferase promoter constructs were then transfected in human choriocarcinoma JEG-3 cells. We first showed that the minimal TFPI-2 promoter is located between -166 and -111 from the translation start site. Luciferase activity consistently increased after stimulation of JEG-3 cells by phorbol 12-myristate 13-acetate indicating that NF1, NF-kappa B and egr-1/Sp1 binding sites are crucial in inducible TFPI-2 expression. Moreover, negative regulatory regions included AP-1 binding sites were identified. This study demonstrates that the TFPI-2 gene promoter exhibits typical features of a housekeeping gene.

Demonstration of estrogen receptor subtypes alpha and beta in human adipose tissue: influences of adipose cell differentiation and fat depot localization.

A novel ER-subtype, the ER-beta has recently been characterized in various tissues, furthermore five isoforms of the ER-beta are known (ER-beta1--ER-beta5). Using immunoblotting and real- time RT-PCR, ER-alpha and beta were studied in human adipose tissue. The expression of ER-alpha mRNA was equal in subcutaneous gluteal adipose tissue, subcutaneous abdominal and intra-abdominal adipose tissue, similar findings were obtained at the protein level. In contrast the amount of ER-beta1 (protein and mRNA) was significantly lower in intra-abdominal adipose tissue as compared with the subcutaneous adipose tissue (five-fold lower in women, P<0.005 and three-fold lower in men, P<0.005) whereas the expression of ER-beta4 and -beta5 mRNA isoforms were significantly higher in gluteal adipose tissue compared to subcutaneous abdominal adipose tissue. No significant gender differences in ER expression was detected in any of the fat depots investigated. During adipocyte differentiation the expression of ER-alpha, -beta4 and -beta5 mRNA declined, whereas, the expression of ER-beta1 mRNA was constant. In conclusion, the existence of ER-beta isoforms in human adipose tissue was demonstrated and the amount of these receptors was dependent upon fat depot localization, with much reduced expression of ER-beta1 in intra-abdominal adipose tissue compared to subcutaneous adipose tissue. These findings may indicate that estrogens could have differentiation and depot specific effects in human adipose tissue.

The two tumor necrosis factor receptors mediate opposite effects on differentiation and glucose metabolism in human adipocytes in primary culture.

Tumor necrosis factor-alpha (TNF) inhibits fat cell differentiation and may also mediate insulin resistance in adipocytes. Both TNF receptors are expressed in adipose tissue, but it is unknown how both receptors are involved in these biological functions. We therefore studied the effect of receptor-specific TNF muteins on adipose differentiation and insulin-stimulated glucose transport of in vitro differentiated human adipocytes in primary culture. Adipocyte precursor cells exposed to the 60-kDa TNF receptor (p60-TNFR)-specific TNF(R32W-S86T) showed a marked decrease in the percentage of differentiating cells in response to adipogenic factors as well as a reduction in peroxisome proliferator-activated receptor-gamma2 (PPARgamma2) messenger RNA (mRNA) and glycerophosphate dehydrogenase (GPDH) activity, but increased endogenous TNF mRNA expression. When cells were incubated with the p80-TNFR-specific TNF(D143N-A145R), adipogenesis and PPARgamma2 mRNA expression were stimulated, GPDH activity was unchanged, and TNF mRNA was completely suppressed. Insulin-stimulated 2-deoxy-D-glucose transport was inhibited by both muteins. The p60-TNFR-mediated inhibition increased continuously during 6 h of treatment and was associated with a down-regulation of glucose transporter-4 (GLUT4) mRNA and GLUT4 protein, whereas the p80-TNFR-specific mutein caused a transient increase in GLUT4 mRNA, but did not alter GLUT4 protein expression after a 24-h incubation. We conclude that p60-TNFR mediates the antiadipogenic effect as well as the down-regulation of GLUT4 by TNF, thereby leading to long-term inhibition of insulin-stimulated glucose transport. In contrast, activation of the p80-TNFR induces an adipogenic effect and transiently up-regulates GLUT4 expression. Here, the acute inhibition of insulin-stimulated glucose transport may be induced by interference with the insulin signaling pathway.

The phosphodiesterase inhibitor IBMX suppresses TNF-alpha expression in human adipocyte precursor cells: a possible explanation for its adipogenic effect.

Tumor necrosis factor-alpha (TNF) is known to inhibit fat cell development in vitro and to be expressed in adipose tissue suggesting that it may act as an auto-/paracrine regulator of adipose tissue mass in vivo. We demonstrate here that endogenous TNF-mRNA expression of cultured human preadipocytes and adipocytes is suppressed by the unspecific phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX), which is frequently used to trigger the differentiation process. As assessed by the measurement of glycerophosphate dehydrogenase, IBMX stimulated the differentiation of human preadipocytes in a dose dependent manner up to threefold but remained ineffective when cells were simultaneously treated with 1 nM TNF. These results suggest that the adipogenic effect of IBMX is mediated by suppression of endogenous TNF production.

Expression pattern of tumour necrosis factor receptors in subcutaneous and omental human adipose tissue: role of obesity and non-insulin-dependent diabetes mellitus.

BACKGROUND: Tumour necrosis factor alpha (TNF) mRNA expression has been reported to be up-regulated in adipose tissue from several rodent models of obesity and diabetes and from obese humans. This elevated expression has been assumed to be associated with the development of insulin resistance. However, the biological signal of TNF may be influenced by the expression of the two TNF receptors: the p60 TNF receptor, TNFR60, and the p80 TNF receptor, TNFR80. DESIGN: The aim of this study was to investigate the mRNA expression pattern of the two TNF receptors and their ligand in two adipose tissue depots of glucose-tolerant obese women [n = 18, body mass index (BMI) 48.2 +/- 8.4 kg m-2], obese women with impaired glucose tolerance or overt non-insulin-dependent diabetes mellitus (NIDDM) (n = 10, BMI 49.1 +/- 11.6 kg m-2) and healthy non-obese control subjects (n = 12, BMI 25.8 +/- 2.7 kg m-2). RNA expression was assessed by a semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) technique. RESULTS: The mean mRNA levels of both TNF receptors were two- to threefold higher in adipose tissue samples from the obese than from the non-obese women (P < 0.01 for each). Although TNFR60 mRNA did not vary within each obese group, there was a wide variation in the levels of TNFR80 mRNA and of TNF mRNA. A comparison of the expression levels between the subcutaneous abdominal and the omental adipose tissue depots showed significantly higher expression in the former. The TNFR60 expression level was positively correlated with BMI and fat cell size, whereas TNFR80 and TNF mRNA levels showed positive associations with serum insulin and triglyceride concentrations. No significant differences in the expression levels were observed between obese individuals with and without impaired glucose tolerance/NIDDM. CONCLUSION: These results indicate that severe obesity in women is characterized by increased amounts of the two TNF receptor mRNAs. The role of this up-regulation for the development of obesity-associated insulin resistance remains to be elucidated.

The role of TNF-alpha in human adipose tissue: prevention of weight gain at the expense of insulin resistance?

Since evidence has appeared that tumor necrosis factor-alpha (TNF) is involved in the loss of body fat in the course of wasting diseases, a large number of studies have investigated the physiological role of this cytokine in adipose tissue. TNF treatment of several in vitro models of adipogenesis clearly showed that TNF is a potent inhibitor of adipose differentiation. This antiadipogenic property is accompanied by suppression of developmental and metabolic markers of fat cell differentiation, such as peroxisome proliferator-activated receptor (PPAR)-gamma2, lipoprotein lipase (LPL), glycerol-3-phosphate dehydrogenase (GPDH) and GLUT4. Moreover, TNF promotes lipolysis in mature adipocytes and, subsequently, a reversion of the adipocyte phenotype. Recent studies demonstrated that TNF directly interferes with the insulin signaling cascade at early steps and, thus, impairs insulin-stimulated glucose transport. Further progress in understanding the role of TNF in adipose tissue was made when endogenous TNF mRNA expression was demonstrated in adipose tissue. Obesity was found to represent a state of overexpression of the TNF system. Such findings support the hypothesis that TNF is a mediator of obesity-linked insulin resistance. However, this concept is mainly based on animal data and is so far only partially supported by studies in humans. Taken together, the results of a variety of experimental and clinical studies suggest that TNF may act as an important auto/paracrine regulator of fat cell function which serves to limit adipose tissue expansion, probably by inducing insulin resistance which may in turn cause metabolic disturbances. Elucidation of the molecular mechanisms of TNF production and action in adipose tissue may help to find new approaches for the treatment of insulin resistance in humans.

Plasma concentrations of soluble TNF-alpha receptors in obese subjects.

BACKGROUND: Recent studies show an increased adipose production of tumor necrosis factor-alpha (TNF-alpha) in human obesity. It was hypothesized from this finding and other data, that TNF-alpha may be a mediator of obesity-linked insulin resistance. OBJECTIVE: The aim of this study was to measure plasma concentrations of the two soluble TNF-alpha receptors, together with those of TNF-alpha in subjects with severe obesity with and without type 2 diabetes mellitus, in comparison to a lean control group, to examine whether plasma concentrations reflect an up-regulation of the TNF system in adipose tissue. PATIENTS AND METHODS: Plasma concentrations of the two soluble TNF-alpha receptors were measured in 49 obese subjects (mean body mass index (BMI): 44.9 kg/m2, 95% confidence intervals (CI) 42.3-47.5 kg/m2, including 19 type 2 diabetic individuals) and 28 lean controls, by using a highly sensitive enzyme-linked immunoassay (ELISA) technique. TNF-alpha concentrations were determined in 28 obese (10 with diabetes) and 23 lean subjects. RESULTS: The obese subjects showed significantly higher plasma concentrations of the soluble p60 and p80 TNF receptor, respectively, compared to the lean control group, independent of the presence of diabetes. Multiple regression analysis, with the p80 TNF receptor as dependent variable, revealed that BMI and log insulin significantly affected the plasma concentration of this soluble receptor subtype, explaining 46% of the variance, whereas for the p60 TNF receptor, only BMI turned out to influence plasma concentrations. TNF-alpha plasma concentrations were not different between the three groups (Kruskal-Wallis test: P=0.34), but due to the low power of the test, an effect of obesity on TNF-alpha is not excluded. CONCLUSION: These data indicate that plasma concentrations of both soluble TNF receptors are elevated in obesity and insulin resistance, possibly as a function of excess body fat. The reported adipose overexpression of TNF-alpha does not seem to be reflected by elevated plasma concentrations, suggesting a primarily local role of the cytokine.

Contribution of androgens to the gender difference in leptin production in obese children and adolescents.

Recent studies demonstrated significantly higher serum leptin concentrations in females as compared with males, even after correction for differences in body fat mass. The aim of our study was to measure serum leptin concentrations in a large group of obese children and adolescents to determine the possible role of sex steroid hormones on both leptin serum concentrations and production in human adipocytes. Obese girls were found to have significantly higher leptin concentrations than boys at the same degree of adiposity (25.2+/-14.1 vs. 17.2+/-12.6 ng/ml, P < 0.001). In a multiple regression analysis with age and body mass index (percent body fat) as fixed variables, it turned out that testosterone had a potent negative effect on serum leptin in boys, but not in girls. In vitro experiments using newly developed human adipocytes in primary culture showed that both testosterone and its biologically active metabolite dihydrotestosterone are able to reduce leptin secretion into the culture medium by up to 62%. Using a semiquantitative reverse transcriptase-PCR method, testosterone was found to suppress leptin mRNA to a similar extent. These results suggest that, apart from differences in body fat mass, the higher androgen concentrations in obese boys are responsible for the lower leptin serum concentrations compared with obese girls.

Difference in leptin mRNA levels between omental and subcutaneous abdominal adipose tissue from obese humans.

Differences in fat cell size and function among adipose tissue depots are well known and may be important in the pathophysiology of the metabolic and cardiovascular complications of obesity. Since the newly discovered adipocyte hormone leptin is thought to be a central factor in the regulation of energy homeostasis, it may be interesting to know if there are regional differences in leptin production. The aim of this study was to compare the level of leptin expression in the omental and subcutaneous abdominal adipose tissue from obese humans. Adipose tissue samples were collected from 25 severely obese adults (mean BMI: 48.9 +/- 9.7 kg/m2) undergoing vertical gastric banding. Semi-quantitative determination of leptin mRNA by the RT-PCR technique showed significantly lower leptin expression in omental compared to subcutaneous abdominal adipose tissue (leptin/Sp1 ratio in omental vs. subcutaneous fat: 1.53 +/- 0.89 vs. 3.02 +/- 1.58, p < 0.01). Identical results were obtained when Northern blotting was applied in a subgroup. Leptin expression increased with age in omental adipose tissue (r = 0.42, p < 0.05), but not in subcutaneous tissue. No correlation was found between BMI or waist/hip ratio (WHR) and leptin expression in omental or subcutaneous adipose tissue. The regional difference in leptin expression was similar in the patients with impaired glucose tolerance/type-2 diabetes and those with normal glucose tolerance. In conclusion, the results of this study indicate that leptin expression is lower in omental than subcutaneous adipose tissue, possibly due to differences in fat cell size and/or sympathetic innervation.