Two distinct mechanisms underlie progesterone-induced proliferation in the mammary gland.

The mouse mammary gland develops postnatally under the control of female reproductive hormones. Estrogens and progesterone trigger morphogenesis by poorly understood mechanisms acting on a subset of mammary epithelial cells (MECs) that express their cognate receptors, estrogen receptor alpha (ERalpha) and progesterone receptor (PR). Here, we show that in the adult female, progesterone drives proliferation of MECs in two waves. The first, small wave, encompasses PR(+) cells and requires cyclin D1, the second, large wave, comprises mostly PR(-) cells and relies on the tumor necrosis factor (TNF) family member, receptor activator of NF-kappaB-ligand (RANKL). RANKL elicits proliferation by a paracrine mechanism. Ablation of RANKL in the mammary epithelium blocks progesterone-induced morphogenesis, and ectopic expression of RANKL in MECs completely rescues the PR(-/-) phenotype. Systemic administration of RANKL triggers proliferation in the absence of PR signaling, and injection of a RANK signaling inhibitor interferes with progesterone-induced proliferation. Thus, progesterone elicits proliferation by a cell-intrinsic and a, more important, paracrine mechanism.

Integrative genome-wide expression profiling identifies three distinct molecular subgroups of renal cell carcinoma with different patient outcome.

BACKGROUND: Renal cell carcinoma (RCC) is characterized by a number of diverse molecular aberrations that differ among individuals. Recent approaches to molecularly classify RCC were based on clinical, pathological as well as on single molecular parameters. As a consequence, gene expression patterns reflecting the sum of genetic aberrations in individual tumors may not have been recognized. In an attempt to uncover such molecular features in RCC, we used a novel, unbiased and integrative approach. METHODS: We integrated gene expression data from 97 primary RCC of different pathologic parameters, 15 RCC metastases as well as 34 cancer cell lines for two-way nonsupervised hierarchical clustering using gene groups suggested by the PANTHER Classification System. We depicted the genomic landscape of the resulted tumor groups by means of Single Nuclear Polymorphism (SNP) technology. Finally, the achieved results were immunohistochemically analyzed using a tissue microarray (TMA) composed of 254 RCC. RESULTS: We found robust, genome wide expression signatures, which split RCC into three distinct molecular subgroups. These groups remained stable even if randomly selected gene sets were clustered. Notably, the pattern obtained from RCC cell lines was clearly distinguishable from that of primary tumors. SNP array analysis demonstrated differing frequencies of chromosomal copy number alterations among RCC subgroups. TMA analysis with group-specific markers showed a prognostic significance of the different groups. CONCLUSION: We propose the existence of characteristic and histologically independent genome-wide expression outputs in RCC with potential biological and clinical relevance.

Epidermal receptor activator of NF-kappaB ligand controls Langerhans cells numbers and proliferation.

Langerhans cells (LC) are the dendritic APC population of the epidermis, where they reside for long periods and are self-replicating. The molecular signals underlying these characteristics are unknown. The TNF superfamily member receptor activator of NF-kappaB ligand (RANKL, TNFSF11) has been shown to sustain viability of blood dendritic cells in addition to its role in promoting proliferation and differentiation of several cell types, notably osteoclasts. In this study, we have studied expression of the RANKL system in skin and have defined a key role for this molecule in LC homeostasis. In vitro and in vivo, human KC expressed RANKL and epidermal LC expressed cell surface RANK. In vitro, RANKL sustained CD34(+) progenitor-derived LC viability following 72-h cultures in cytokine-free medium (79.5 +/- 1% vs 55.2 +/- 5.7% live cells, respectively; n = 4; p < 0.05). In vivo, RANKL-deficient mice displayed a marked reduction in epidermal LC density (507.1 +/- 77.2 vs 873.6 +/- 41.6 LC per mm(2); n = 9; p < 0.05) and their proliferation was impaired without a detectable effect on apoptosis. These data indicate a key role for the RANKL system in the regulation of LC survival within the skin and suggest a regulatory role for KC in the maintenance of epidermal LC homeostasis.

The secreted protease Adamts18 links hormone action to activation of the mammary stem cell niche.

Estrogens and progesterone control breast development and carcinogenesis via their cognate receptors expressed in a subset of luminal cells in the mammary epithelium. How they control the extracellular matrix, important to breast physiology and tumorigenesis, remains unclear. Here we report that both hormones induce the secreted protease Adamts18 in myoepithelial cells by controlling Wnt4 expression with consequent paracrine canonical Wnt signaling activation. Adamts18 is required for stem cell activation, has multiple binding partners in the basement membrane and interacts genetically with the basal membrane-specific proteoglycan, Col18a1, pointing to the basement membrane as part of the stem cell niche. In vitro, ADAMTS18 cleaves fibronectin; in vivo, Adamts18 deletion causes increased collagen deposition during puberty, which results in impaired Hippo signaling and reduced Fgfr2 expression both of which control stem cell function. Thus, Adamts18 links luminal hormone receptor signaling to basement membrane remodeling and stem cell activation.

Discretization of Gene Expression Data Unmasks Molecular Subgroups Recurring in Different Human Cancer Types.

Despite the individually different molecular alterations in tumors, the malignancy associated biological traits are strikingly similar. Results of a previous study using renal cell carcinoma (RCC) as a model pointed towards cancer-related features, which could be visualized as three groups by microarray based gene expression analysis. In this study, we used a mathematic model to verify the presence of these groups in RCC as well as in other cancer types. We developed an algorithm for gene-expression deviation profiling for analyzing gene expression data of a total of 8397 patients with 13 different cancer types and normal tissues. We revealed three common Cancer Transcriptomic Profiles (CTPs) which recurred in all investigated tumors. Additionally, CTPs remained robust regardless of the functions or numbers of genes analyzed. CTPs may represent common genetic fingerprints, which potentially reflect the closely related biological traits of human cancers.

Sugar transport systems of Bifidobacterium longum NCC2705.

Here we present the complement of the carbohydrate uptake systems of the strictly anaerobic probiotic Bifidobacterium longum NCC2705. The genome analysis of this bacterium predicts that it has 19 permeases for the uptake of diverse carbohydrates. The majority belongs to the ATP-binding cassette transporter family with 13 systems identified. Among them are permeases for lactose, maltose, raffinose, and fructooligosaccharides, a commonly used prebiotic additive. We found genes that encode a complete phosphotransferase system (PTS) and genes for three permeases of the major facilitator superfamily. These systems could serve for the import of glucose, galactose, lactose, and sucrose. Growth analysis of NCC2705 cells combined with biochemical characterization and microarray data showed that the predicted substrates are consumed and that the corresponding transport and catabolic genes are expressed. Biochemical analysis of the PTS, in which proteins are central in regulation of carbon metabolism in many bacteria, revealed that B. longum has a glucose-specific PTS, while two other species (Bifidobacterium lactis and Bifidobacterium bifidum) have a fructose-6-phosphate-forming fructose-PTS instead. It became obvious that most carbohydrate systems are closely related to those from other actinomycetes, with a few exceptions. We hope that this report on B. longum carbohydrate transporter systems will serve as a guide for further in-depth analyses on the nutritional lifestyle of this beneficial bacterium.

Lactose-over-glucose preference in Bifidobacterium longum NCC2705: glcP, encoding a glucose transporter, is subject to lactose repression.

Analysis of culture supernatants obtained from Bifidobacterium longum NCC2705 grown on glucose and lactose revealed that glucose utilization is impaired until depletion of lactose. Thus, unlike many other bacteria, B. longum preferentially uses lactose rather than glucose as the primary carbon source. Glucose uptake experiments with B. longum cells showed that glucose transport was repressed in the presence of lactose. A comparative analysis of global gene expression profiling using DNA arrays led to the identification of only one gene repressed by lactose, the putative glucose transporter gene glcP. The functionality of GlcP as glucose transporter was demonstrated by heterologous complementation of a glucose transport-deficient Escherichia coli strain. Additionally, GlcP exhibited the highest substrate specificity for glucose. Primer extension and real-time PCR analyses confirmed that expression of glcP was mediated by lactose. Hence, our data demonstrate that the presence of lactose in culture medium leads to the repression of glucose transport and transcriptional down-regulation of the glucose transporter gene glcP. This may reflect the highly adapted life-style of B. longum in the gastrointestinal tract of mammals.