Paramecium tredecaurelia: A Unique Non-Polymorphic Species of the P. aurelia spp. Complex (Oligohymenophorea, Ciliophora)

New stands of Paramecium tredecaurelia, a rare species of the P. aurelia spp. complex, were identified in Thailand and Madagascar on the basis of mating reactions and molecular markers (rDNA and mtDNA). Analysis of DNA fragments showed that all P. tredecaurelia strains, the recently recorded ones and the ones known previously from France, Mexico, and Israel, form a monophyletic and well-defined clade in the P. aurelia species trees. All of these strains, collected from different localities around the world, represent identical or nearly identical haplotypes in terms of all the studied DNA fragments. Given the huge distances between particular collection sites, such a low level of variability of the studied sequences may result from a slow rate of evolution in P. tredecaurelia

Expression of angiogenic regulators, VEGF and leptin, is regulated by the EGF/PI3K/STAT3 pathway in colorectal cancer cells.

Abstract Both leptin and vascular endothelial growth factor (VEGF) are growth and angiogenic cytokines that are upregulated in different types of cancer and have been implicated in neoplastic progression. Here we investigated the molecular mechanism by which leptin and VEGF expression are regulated in colon cancer by epidermal growth factor (EGF). In colon cancer cell line HT-29, EGF induced the binding of signal transducer and activator transcription 3 (STAT3) to STAT3 consensus motifs within the VEGF and leptin promoters and stimulated leptin and VEGF mRNA and protein synthesis. All these EGF effects were significantly blocked when HT-29 cells were treated with an inhibitor of the phosphoinositide 3-kinase (PI3K) pathway, LY294002, or with small interfering RNA (siRNA) targeting STAT3. Thus, our study identified the EGF/PI3K/STAT3 signaling as an essential pathway regulating VEGF and leptin expression in EGF-responsive colon cancer cells. This suggests that STAT3 pathways might constitute attractive pharmaceutical targets in colon cancer patients where anti-EGF receptor drugs are ineffective

Mechanism of leptin expression in breast cancer cells: role of hypoxia-inducible factor-1alpha.

We reported previously that the obesity hormone leptin is overexpressed in breast cancer biopsies. Here, we investigated molecular mechanisms involved in this process, focusing on conditions that are associated with obesity, that is, hyperinsulinemia and induction of hypoxia. By using quantitative real-time PCR, immunofluorescent detection of proteins and enzyme-linked immunosorbent assays, we found that treatment of MCF-7 breast cancer cells with high doses of insulin or the hypoxia-mimetic agent CoCl2, or culturing the cells under hypoxic conditions significantly increased the expression of leptin mRNA and protein. Notably, the greatest leptin mRNA and protein expression were observed under combined hyperinsulinemia and hypoxia or hypoxia-mimetic treatments. Luciferase reporter assays suggested that increased leptin synthesis could be related to the activation of the leptin gene promoter. DNA affinity precipitation and chromatin immunoprecipitation experiments revealed that insulin, CoCl2 and/or hypoxia treatments augmented nuclear accumulation of hypoxia-inducible factor-1a (HIF-1a) and increased its interaction with several upstream leptin regulatory sequences, especially with the proximal promoter containing four hypoxia-response elements and three GC-rich regions. By using reverse chromatin precipitation, we determined that loading of HIF-1a on the proximal leptin promoter concurred with the recruitment of p300, the major HIF coactivator, suggesting that the HIF/p300 complex is involved in leptin transcription. The importance of HIF-1a in insulin- and CoCl2-activated leptin mRNA and protein expression was confirmed using RNA interferenc

Increased expression of leptin and the leptin receptor as a marker of breast cancer progression: possible role of obesity-related stimuli

PURPOSE: Recent in vitro studies suggested that the autocrine leptin loop might contribute to breast cancer development by enhancing cell growth and survival. To evaluate whether the leptin system could become a target in breast cancer therapy, we examined the expression of leptin and its receptor (ObR) in primary and metastatic breast cancer and noncancer mammary epithelium. We also studied whether the expression of leptin/ObR in breast cancer can be induced by obesity-related stimuli, such as elevated levels of insulin, insulin-like growth factor-I (IGF-I), estradiol, or hypoxic conditions. EXPERIMENTAL DESIGN: The expression of leptin and ObR was examined by immunohistochemistry in 148 primary breast cancers and 66 breast cancer metastases as well as in 90 benign mammary lesions. The effects of insulin, IGF-I, estradiol, and hypoxia on leptin and ObR mRNA expression were assessed by reverse transcription-PCR in MCF-7 and MDA-MB-231 breast cancer cell lines. RESULTS: Leptin and ObR were significantly overexpressed in primary and metastatic breast cancer relative to noncancer tissues. In primary tumors, leptin positively correlated with ObR, and both biomarkers were most abundant in G3 tumors. The expression of leptin mRNA was enhanced by insulin and hypoxia in MCF-7 and MDA-MB-231 cells, whereas IGF-I and estradiol stimulated leptin mRNA only in MCF-7 cells. ObR mRNA was induced by insulin, IGF-I, and estradiol in MCF-7 cells and by insulin and hypoxia in MDA-MB-231 cells. CONCLUSIONS: Leptin and ObR are overexpressed in breast cancer, possibly due to hypoxia and/or overexposure of cells to insulin, IGF-I, and/or estradiol

Founder mutations in BRCA1 and BRCA2 genes

BRCA1 and BRCA2 germline mutations contribute to a significant number of familial and hereditary breast and/or ovarian cancers. The proportion of high-risk families with breast and/or ovarian cancer cases due to mutations in these tumor suppressor genes varies widely among populations. In some population, a wide spectrum of different mutations in both genes are present, whereas in other groups specific mutations in BRCA1 and BRCA2 have been reported with high frequency. Most of these mutations are prevalent in restricted populations as consequence of a founder effect. The comparison of haplotypes between families with the same mutation can distinguish whether high-frequency alleles derive from an older or more recent single mutational event or whether they have arisen independently more than once. Here, we review some of the most well-known and significant examples of founder mutations in BRCA genes found in European and non-European populations. In conclusion, the identification of the ethnic group of families undergoing genetic counseling enables the geneticist and oncologist to make more specific choices, leading to simplify the clinical approach to genetic testing carried out on members of high-risk families. Futhermore, the high frequency of founder mutations, allowing to analyze a large number of cases, might provide accurate information regarding their penetrance

The estrogen receptor alpha:insulin receptor substrate 1 complex in breast cancer: structure-function relationships

Background: Insulin receptor substrate 1 (IRS-1) is a signaling molecule that exerts a key role in mediating cross talk between estrogen receptor a (ERa) and insulin-like growth factor 1 (IGF-1) in breast cancer cells. Previously, we demonstrated that a fraction of IRS-1 binds ERa, translocates to the nucleus, and modulates ERa-dependent transcription at estrogen response elements (ERE). Here, we studied structure–function relationships of the ERa:IRS-1 complex under IGF-1 and/or estradiol (E2) stimulation. Materials and methods: ERa and IRS-1 deletion mutants were used to analyze structural and functional ERa/IRS-1 interactions. IRS-1 binding to ERE and IRS-1 role in ERa-dependent ERE transcription was examined by chromatin immunoprecipitation and gene reporter analysis, respectively. The requirement for IRS-1 in ERa function was tested with RNAi technology. Results: Nuclear translocation of IRS-1 was induced by E2, IGF-1, and a combination of both stimuli. ERa/IRS-1 binding was direct and involved the activation function-1 (AF-1)/DNA binding domain (DBD) region of ERa and two discrete regions of IRS-1 (the N-terminal pleckstrin homology domain and a region within the C-terminus). IRS-1 knock down abrogated IGF-1-dependent transcriptional activity of unliganded ERa, but induced the activity of liganded ERa. Conclusions: ERa/IRS-1 interactions are direct and involve the ERa AF-1/DBD domain and IRS-1 domains mapping within N- and C-terminus. IRS-1 may act as a repressor of liganded ERa and coactivator of unliganded ERa

Is BRCA1-5083del19, identified in breast cancer patients of Sicilian origin, a Calabrian founder mutation?

Various studies have been published in Italy regarding the different BRCA1 mutations, but only the BRCA1-5083del19 mutation is recurrent and specific to individuals of Italian descent with a founder effect on the Calabrian population. In our previous study, BRCA1-5083del19 mutation carriers were found in four index cases of 106 Sicilian patients selected for familial and/or hereditary breast/ovarian cancers. The high frequency rate of this mutation identified in the Sicilian population led us to perform haplotype analysis in all family carriers. Five highly polymorphic microsatellite markers were used (D17S1320, D17S932, D17S1323, D17S1326, D17S1325) to establish whether or not all these families had a common ancestor. This analysis showed that all mutation carriers of these families had a common allele. None of the non-carriers of the mutation or of the 50 healthy Sicilian controls showed this haplotype. This allelotype analysis highlighted the presence of a common allele (ancestor), thus suggesting the presence of a founder effect in the Sicilian population. Our results are in contrast with other studies but only the allelotype analysis of all the BRCA1-5083del19 mutation carriers of two neighboring regions of the south of Italy (Calabria and Sicily) will make it possible to identify the real ancestor of this mutation

Effects of PPARγ agonists on the expression of leptin and vascular endothelial growth factor in breast cancer cells.

The obesity hormone leptin has been implicated in breast cancer development. Breast cancer cells express the leptin receptor and are able to synthesize leptin in response to obesity-related stimuli. Furthermore, leptin is a positive regulator of vascular endothelial growth factor (VEGF) and high levels of both proteins are associated with worse prognosis in breast cancer patients. Peroxisome proliferator-activated receptor (PPAR) ligands are therapeutic agents used in patient with Type 2 diabetes and obesity which have recently been studied for their potential anti-tumor effect. Here, we studied if these compounds, ciglitazone and GW1929, can affect the expression of leptin and VEGF in breast cancer cells. In MDA-MB-231 and MCF-7 breast cancer cells, treatment with submolar concentrations of ciglitazone and GW1929 elevated the expression of leptin and VEGF mRNA and protein, and increased cell viability and migration. These effects coincided with increased recruitment of PPAR to the proximal leptin promoter and decreased association of a transcriptional factor Sp1 with this DNA region