Independent evolution of the core and accessory gene sets in the genus Neisseria: insights gained from the genome of Neisseria lactamica isolate 020-06

<p>Abstract</p> <p>Background</p> <p>The genus <it>Neisseria </it>contains two important yet very different pathogens, <it>N. meningitidis </it>and <it>N. gonorrhoeae</it>, in addition to non-pathogenic species, of which <it>N. lactamica </it>is the best characterized. Genomic comparisons of these three bacteria will provide insights into the mechanisms and evolution of pathogenesis in this group of organisms, which are applicable to understanding these processes more generally.</p> <p>Results</p> <p>Non-pathogenic <it>N. lactamica </it>exhibits very similar population structure and levels of diversity to the meningococcus, whilst gonococci are essentially recent descendents of a single clone. All three species share a common core gene set estimated to comprise around 1190 CDSs, corresponding to about 60% of the genome. However, some of the nucleotide sequence diversity within this core genome is particular to each group, indicating that cross-species recombination is rare in this shared core gene set. Other than the meningococcal <it>cps </it>region, which encodes the polysaccharide capsule, relatively few members of the large accessory gene pool are exclusive to one species group, and cross-species recombination within this accessory genome is frequent.</p> <p>Conclusion</p> <p>The three <it>Neisseria </it>species groups represent coherent biological and genetic groupings which appear to be maintained by low rates of inter-species horizontal genetic exchange within the core genome. There is extensive evidence for exchange among positively selected genes and the accessory genome and some evidence of hitch-hiking of housekeeping genes with other loci. It is not possible to define a 'pathogenome' for this group of organisms and the disease causing phenotypes are therefore likely to be complex, polygenic, and different among the various disease-associated phenotypes observed.</p

Low Dose, Low Cost Estradiol Pellets Can Support MCF-7 Tumour Growth in Nude Mice without Bladder Symptoms

MCF-7 cells are a slow growing estrogen receptor (ER) positive human breast cancer cell line that is commonly used to model estrogen responsive breast cancer cell growth in-vitro and tumour growth in-vivo. These tumours require estrogen supplementation, and in-vivo doses of between 0.72mg and 2mg estradiol pellets are commonly implanted in the dorsal flank of ovariectomised, immunocompromised mice. We wanted to grow MCF-7 tumours in immunocompromised mice without the need to be ovariectomised. When we treated immunocompromised mice with 0.72mg pellets to induce MCF7 tumour growth, the mice developed urosepsis. We have now shown that lower doses of estradiol pellets, 0.3mg and 0.5mg, induce elevated serum estrogen levels and maintain tumour growth, without causing urosepsis. Supplementation for only one week did not support sustained MCF7 tumour growth. In conclusion, 0.3mg and 0.5mg silastic pellets can be used to stimulate ER+ breast cancer growth in ovary-intact, immune compromised mice

PtdIns(3,4,5)P₃ -dependent rac exchanger 1 (PREX1) rac-guanine nucleotide exchange factor (GEF) activity promotes breast cancer cell proliferation and tumor growth via activation of extracellular signal-regulated kinase 1/2 (ERK1/2) signaling

PtdIns(3,4,5)P(3)-dependent Rac exchanger 1 (PREX1) is a Rac-guanine nucleotide exchange factor (GEF) overexpressed in a significant proportion of human breast cancers that integrates signals from upstream ErbB2/3 and CXCR4 membrane surface receptors. However, the PREX1 domains that facilitate its oncogenic activity and downstream signaling are not completely understood. We identify that ERK1/2 MAPK acts downstream of PREX1 and contributes to PREX1-mediated anchorage-independent cell growth. PREX1 overexpression increased but its shRNA knockdown decreased ERK1/2 phosphorylation in response to EGF/IGF-1 stimulation, resulting in induction of the cell cycle regulators cyclin D1 and p21(WAF1/CIP1). PREX1-mediated ERK1/2 phosphorylation, anchorage-independent cell growth, and cell migration were suppressed by inhibition of MEK1/2/ERK1/2 signaling. PREX1 overexpression reduced staurosporine-induced apoptosis whereas its shRNA knockdown promoted apoptosis in response to staurosporine or the anti-estrogen drug tamoxifen. Expression of wild-type but not GEF-inactive PREX1 increased anchorage-independent cell growth. In addition, mouse xenograft studies revealed that expression of wild-type but not GEF-dead PREX1 resulted in the formation of larger tumors that displayed increased phosphorylation of ERK1/2 but not AKT. The impaired anchorage-independent cell growth, apoptosis, and ERK1/2 signaling observed in stable PREX1 knockdown cells was restored by expression of wild-type but not GEF-dead-PREX1. Therefore, PREX1-Rac-GEF activity is critical for PREX1-dependent anchorage-independent cell growth and xenograft tumor growth and may represent a possible therapeutic target for breast cancers that exhibit PREX1 overexpression

Inositol polyphosphate 4-phosphatase II regulates PI3K/Akt signaling and is lost in human basal-like breast cancers

Inositol polyphosphate 4-phosphatase-II (INPP4B) is a regulator of the phosphoinositide 3-kinase (PI3K) signaling pathway and is implicated as a tumor suppressor in epithelial carcinomas. INPP4B loss of heterozygosity (LOH) is detected in some human breast cancers; however, the expression of INPP4B protein in breast cancer subtypes and the normal breast is unknown. We report here that INPP4B is expressed in nonproliferative estrogen receptor (ER)-positive cells in the normal breast, and in ER-positive, but not negative, breast cancer cell lines. INPP4B knockdown in ER-positive breast cancer cells increased Akt activation, cell proliferation, and xenograft tumor growth. Conversely, reconstitution of INPP4B expression in ER-negative, INPP4B-null human breast cancer cells reduced Akt activation and anchorage-independent growth. INPP4B protein expression was frequently lost in primary human breast carcinomas, associated with high clinical grade and tumor size and loss of hormone receptors and was lost most commonly in aggressive basal-like breast carcinomas. INPP4B protein loss was also frequently observed in phosphatase and tensin homolog (PTEN)-null tumors. These studies provide evidence that INPP4B functions as a tumor suppressor by negatively regulating normal and malignant mammary epithelial cell proliferation through regulation of the PI3K/Akt signaling pathway, and that loss of INPP4B protein is a marker of aggressive basal-like breast carcinomas

The genus Neisseria

The genus Neisseria comprises a number of closely related Gram-negative organisms isolated from humans and animals. Their interrelationships are poorly resolved by phenotypic approaches, and the classification of the species groups by molecular techniques has been confused by a combination of their genetic similarity and extensive shared sequence polymorphism as a consequence of shared ancestry, horizontal genetic exchange, or both. Whole genome sequence analysis, especially of large numbers of draft genome sequences, has enabled the comparison of core genes across the genus, and this has proved to be an effective means of defining species groups within the genus. This redefinition is largely consistent with previous species designations with relatively few adjustments necessary. Most members of the genus are not, or are very rarely, pathogenic, but the genus contains the globally significant pathogens Neisseria meningitidis, the meningococcus, and Neisseria gonorrhoeae, the gonococcus. The meningococcus is an ‘‘accidental pathogen’’: predominantly existing as a harmless commensal, with very few infections resulting in pathology. Pathology does not appear to play a role in the transmission of this organism, although some genotypes have a greater propensity to cause disease than others. The majority of work on the genus concentrates on the two pathogenic species, with attempts to develop a comprehensive vaccine against the meningococcus a major driver for research. The gonococcus is antigenically highly diverse but genetically quite uniform, and probably emerged from a single clone that changed its niche. Emerging antibiotic resistance of the gonococcus currently represents the most significant global health challenge presented by this genus