Very large common fragile site genes and their potential role in cancer development

Common fragile sites (CFSs) are large chromosomal regions that are hot-spots for alterations especially within cancer cells. The three most frequently expressed CFS regions (FRA3B, FRA16D and FRA6E) contain genes that span extremely large genomic regions (FHIT, WWOX and PARK2, respectively), and these genes were found to function as important tumor suppressors. Many other CFS regions contain extremely large genes that are also targets of alterations in multiple cancers, but none have yet been demonstrated to function as tumor suppressors. The loss of expression of just FHIT or WWOX has been found to be associated with a worse overall clinical outcome. Studies in different cancers have revealed that some cancers have decreased expression of multiple large CFS genes. This loss of expression could have a profound phenotypic effect on these cells. In this review, we will summarize the known large common fragile site genes and discuss their potential relationship to cancer development.     

Kallikrein-related peptidases

Kallikrein 1 (KLK1), a key component of the kallikrein-kinin system, originates from a locus on the long arm of chromosome 19 that contains several related serine endopeptidases. The biological role of these kallikrein-related peptidases is not clear, but emerging evidence suggests that they might be important in several physiological systems, e.g., in male reproduction, skin homeostasis, tooth enamel formation and neural development and plasticity. The kallikrein locus has undergone some major evolutionary events. Most spectacular are relatively recent duplications of KLK1 that have created 13 and 9 functional genes that are unique to the mouse and the rat, respectively. Human paralogs are KLK2 and KLK3: the latter encoding the cancer biomarker prostate-specific antigen. In this review on kallikrein-related peptidases, the focus is on their evolution, their role in skin homeostasis and semen liquefaction, and their utility as cancer biomarkers.     

Non-B DNA structure-induced genetic instability and evolution

Repetitive DNA motifs are abundant in the genomes of various species and have the capacity to adopt non-canonical (i.e., non-B) DNA structures. Several non-B DNA structures, including cruciforms, slipped structures, triplexes, G-quadruplexes, and Z-DNA, have been shown to cause mutations, such as deletions, expansions, and translocations in both prokaryotes and eukaryotes. Their distributions in genomes are not random and often co-localize with sites of chromosomal breakage associated with genetic diseases. Current genome-wide sequence analyses suggest that the genomic instabilities induced by non-B DNA structure-forming sequences not only result in predisposition to disease, but also contribute to rapid evolutionary changes, particularly in genes associated with development and regulatory functions. In this review, we describe the occurrence of non-B DNA-forming sequences in various species, the classes of genes enriched in non-B DNA-forming sequences, and recent mechanistic studies on DNA structure-induced genomic instability to highlight their importance in genomes.     

Leukotrienes: Mediators that have been typecast as villains

As befalls many mediators that act upon the human stage, leukotrienes have become identified with their most powerful roles as villains of the immune system. They are well known for their leading roles in allergic diseases, including asthma. They also have gained recognition for their dramatic role as promoters of inflammation. As new roles for these lipid messengers are sought, it is becoming apparent that the leukotrienes have been typecast as bad guys of the immune system. As examples, their more recent roles have been in atherosclerosis, pulmonary fibrosis and cancer. However, upon further evaluation, we can begin to see their versatility. Thus, leukotrienes stimulate innate immunity against pathogens. In addition, they promote the expression of mediators, receptors and other molecules that are important for immune defense. In these lesser known roles, they lead the fight against bacterial, fungal and viral infection. This review is intended to shed light on the leukotrienes, where they come from and what we really know about them.     

New developments in the biological functions of lysophospholipids

Lysophospholipids have long been recognized as membrane phospholipid metabolites, but only recently has their role as intercellular signaling molecules been appreciated. Two of the best-studied lysophospholipids, LPA and S1P, signal through cognate G-protein-coupled receptors to activate many well-known intracellular signaling pathways, leading to a variety of biologically important cell responses. Lysophospholipids and their receptors have been found in a wide range of tissues and cell types, indicating their importance in many physiological processes, including reproduction, vascular development, cancer and nervous system function. This article will focus on the most recent findings regarding the biological functions of lysophospholipids in mammalian systems, specifically as they relate to health and disease. Received 5 April 2006; received after revision 22 June 2006; accepted 9 August 2006     

Genetic studies of diseases

Genomic alterations lead to cancer complexity and form a major hurdle for comprehensive understanding of the molecular mechanisms underlying oncogenesis. In this review, we describe recent advances in studying cancer-associated genes from a systems biology point of view. The integration of known cancer genes onto protein and signaling networks reveals the characteristics of cancer genes within networks. This approach shows that cancer genes often function as network hub proteins which are involved in many cellular processes and form focal nodes in information exchange between many signaling pathways. Literature mining allows constructing gene-gene networks, in which new cancer genes can be identified. The gene expression profiles of cancer cells are used for reconstructing gene regulatory networks. By doing so, genes which are involved in the regulation of cancer progression can be picked up from these networks, after which their functions can be further confirmed in the laboratory.     

Breast cancer stem cell: the roles and therapeutic implications

Breast cancers have been increasingly recognized as malignancies displaying frequent inter- and intra-tumor heterogeneity. This heterogeneity is represented by diverse subtypes and complexity within tumors, and impinges on response to therapy, metastasis, and prognosis. Cancer stem cells (CSCs), a subpopulation of cancer cells endowed with self-renewal and differentiation capacity, have been suggested to contribute to tumor heterogeneity. The CSC concept posits a hierarchical organization of tumors, at the apex of which are stem cells that drive tumor initiation, progression, and recurrence. In breast cancer, CSCs have been proposed to contribute to malignant progression, suggesting that targeting breast cancer stem cells (BCSCs) may improve treatment efficacy. Currently, several markers have been reported to identify BCSCs. However, there is objective variability with respect to the frequency and phenotype of BCSCs among different breast cancer cell lines and patients, and the regulatory mechanisms of BCSCs remain unclear. In this review, we summarize current literature about the diversity of BCSC markers, the roles of BCSCs in tumor development, and the regulatory mechanisms of BCSCs. We also highlight the most recent advances in BCSC targeting therapies and the challenges in translating the knowledge into clinical practice.     

Genes involved in breast cancer metastasis to bone

Metastasis to bone occurs frequently in advanced breast cancer and is accompanied by debilitating skeletal complications. Current treatments are palliative and new therapies that specifically prevent the spread of breast cancer to bone are urgently required. While our understanding of interactions between breast cancer cells and bone cells has greatly improved, we still know little about the molecular determinants that regulate specific homing of breast cancer cells to the bone. In this review, we focus on genes that have been implicated in migration and adhesion of breast cancer cells to bone, as well as genes that promote tumor cell proliferation in the bone microenvironment. In addition, the review discusses new technologies, including better animal models, that will further assist with the identification of the molecular determinants of bone metastasis and will guide the development of new therapies. Received 25 January 2002; received after revision 27 March 2002; accepted 5 April 2002 RID="*" ID="*"Corresponding author.     

DNA damage repair and transcription

Silencing of DNA repair genes plays a critical role in the development of the cancer because these genes, functioning normally, would prevent the accumulation of mutations leading to carcinogenesis. Epigenetic gene silencing is an alternative mechanism to genetic gene aberration, inactivating those genes in cancer. DNA methylation and histone modification are the major factors for epigenetic regulation of gene expression. Here, we describe recent advances in understanding of epigenetic silencing of DNA repair genes and their epigenetic mechanisms involving DNA methylation and histone modification.     

The causes of Charcot-Marie-Tooth disease

Charcot-Marie-Tooth (CMT) disease serves as the summary term for the most frequent forms of inherited peripheral neuropathies that affect motor and sensory nerves. In the last 12 years, 14 genes have been identified that cause different CMT subforms. The genes found initially are predominantly responsible for demyelinating and dysmyelinating neuropathies. Genes affected in axonal and rare forms of CMT have only recently been identified. In this review, we will focus on the currently known genes that are associated with CMT syndromes with regards to their genetics and function.Received 5 April 2003; received after revision 20 May 2003; accepted 23 May 2003     

Chromosome instability and deregulated proliferation: an unavoidable duo

The concept that aneuploidy is a characteristic of malignant cells has long been known; however, the idea that aneuploidy is an active contributor to tumorigenesis, as opposed to being an associated phenotype, is more recent in its evolution. At the same time, we are seeing the emergence of novel roles for tumor suppressor genes and oncogenes in genome stability. These include the adenomatous polyposis coli gene (APC), p53, the retinoblastoma susceptibility gene (RB1), and Ras. Originally, many of these genes were thought to be tumor suppressive or oncogenic solely because of their role in proliferative control. Because of the frequency with which they are disrupted in cancer, chromosome instability caused by their dysfunction may be more central to tumorigenesis than previously thought. Therefore, this review will highlight how the proper function of cell cycle regulatory genes contributes to the maintenance of genome stability, and how their mutation in cancer obligatorily connects proliferation and chromosome instability.     

SLC26A4基因突变与耳聋

耳聋是最常见感觉障碍之一,与遗传关系密切.SLC26A4基因作为第二位的耳聋基因,与Pendred综合征(PS)和非综合征性聋DFNB4密切相关.SLC26A4基因突变主要与PS及DFNB4共同表现出的前庭水管扩大(EVA)相关,且不同种族及地区EVA患者该基因的突变频率及热点突变大不相同.SLC26A4基因的表现型与突变的类型关系不大,而是与等位基因数目相关.但目前SLC26A4基因突变的研究仍不完善.本文主要综述了近年来耳聋及SLC26A4基因的研究进展.