Current Molecular Medicine - Volume 11, Issue 4, 2011

The Notch pathway is a highly conserved signaling pathway in multicellular eukaryotes essential in controlling spatial patterning, morphogenesis and homeostasis in embryonic and adult tissues. Notch proteins coordinate cell-cell communication through receptor-ligand interactions between adjacent cells. Notch signaling is frequently deregulated by oncogenic mutation or overexpression in many cancer types. Notch activity is controlled by three sequential cleavage steps leading to ectodomain shedding and transcriptional activation. Here we review the key regulatory steps in the activation of Notch, from receptor maturation to receptor activation (HIT) via a rate-limiting proteolytic cascade (RUN) in the context of species-specific differences.

The mammary gland is a highly regenerative organ that can undergo multiple cycles of proliferation, lactation and involution, a process controlled by stem cells. The last decade much progress has been made in the identification of signaling pathways that function in these stem cells to control self-renewal, lineage commitment and epithelial differentiation in the normal mammary gland. The same signaling pathways that control physiological mammary development and homeostasis are also often found deregulated in breast cancer. Here we provide an overview on the functional and molecular identification of mammary stem cells in the context of both normal breast development and breast cancer. We discuss the contribution of some key signaling pathways with an emphasis on Notch receptor signaling, a cell fate determination pathway often deregulated in breast cancer. A further understanding of the biological roles of the Notch pathway in mammary stem cell behavior and carcinogenesis might be relevant for the development of future therapies.

The discovery of new biomarkers is a rapidly advancing area in cancer biology. The challenge of biomarker development for broad clinical use requires the translation of lab-based knowledge into clinical practice. The Long Interspersed Nuclear Elements-1 (LINE-1s or L1 elements) are active members of an autonomous family of non-LTR retrotransposons and occupy nearly 17% of the human genome. There is strong experimental evidence that the global hypomethylation of genomic DNA in cancer cells results in the activation of L1s and their expression is detectable at genome, transcriptome and proteome levels in human cancer cells. Thus, human L1s constitute a potential marker for cancer cells. In this review we have attempted to scrutinize L1 expression profiles in clinical cancer studies by undertaking a comprehensive systematic analysis of papers published in the field so far with a view to providing a more complete picture of the detection methods used, improvements achieved and potential future directions. Ultimately, we will try to evaluate the potential of L1s as a molecular marker in cancer detection.

Worldwide obesity is a growing health problem, associated with increased risk of chronic disease. Understanding the molecular basis of adipogenesis and fat cell development in obesity is essential to identify new biomarkers and therapeutic targets for the development of anti-obesity drugs. microRNAs (miRNAs) appear to play regulatory roles in many biological processes associated with obesity, including adipocyte differentiation, insulin action and fat metabolism. Recent studies show miRNAs are dysregulated in obese adipose tissue. During adipogenesis miRNAs can accelerate or inhibit adipocyte differentiation and hence regulate fat cell development. In addition miRNAs may regulate adipogenic lineage commitment in multipotent stem cells and hence govern fat cell numbers. Recent findings suggest miR-519d may be associated with human obesity, but larger case-control studies are needed. Few miRNA targets have been experimentally validated in adipocytes but interestingly both miR-27 and miR-519d target PPAR family members, which are well established regulators of fat cell development. In this review recent advances in our understanding of the role of miRNAs in fat cell development and obesity are discussed. The potential of miRNA based therapeutics targeting obesity is highlighted as well as recommendations for future research which could lead to a breakthrough in the treatment of obesity.

WHIM syndrome is a dominantly inherited primary immunodeficiency disorder representing the first identified example of human disease caused by mutations in the gene encoding for the chemokine receptor CXCR4. Pathogenesis is mediated by CXCR4 hyperfunction, leading to increased responsiveness to its unique ligand CXCL12 (also known as SDF-1). The altered CXCR4/CXCL12 interaction likely impairs cellular homeostasis and trafficking, resulting in immunological dysfunctions. The acronym WHIM resumes the main features of the syndrome: Warts, Hypogammaglobulinemia, Infections and Myelokathexis, which is abnormal retention of mature neutrophils in the bone marrow. WHIM patients suffer from recurrent bacterial infections since childhood and manifest a specific susceptibility to HPV infections. Hematological findings include neutropenia, lymphopenia and hypogammaglobulinemia. Because of the rarity of the disease and the heterogeneity in clinical presentation, diagnosis is often delayed. In the majority of patients, the phenotype is incomplete at the onset and WHIM syndrome is not suspected. Early identification may improve clinical and therapeutic management. Symptomatic treatments include G-CSF, substitutive immunoglobulins and antibiotic prophylaxis. A new therapeutic strategy might include the potent inhibitor of CXCR4 function plerixafor (Mozobil), as an agent specifically targeting the molecular defect in order to attenuate the phenotypic manifestations of the syndrome.

Multiple Sclerosis is the most common non-traumatic disorder of the central nervous system and is generally regarded as an immune-mediated disorder that occurs in young adults. Since cerebrospinal fluid is in close contact with the extracellular surface of the brain, it is of great interest to examine possible biomarkers for multiple sclerosis. Proteomic studies of cerebrospinal fluid samples represent an important step towards a better understanding of the disease and may lead to the identification of clinically useful markers. Methodological advances in proteomics allowed the comparison of the protein content in different cerebrospinal fluid samples, using gel or liquid-based approaches coupled with mass spectrometry. In this paper, we discuss the advantages and limitations of the strategies employed and the potential biomarkers for multiple sclerosis identified so far using proteomics-based approaches.