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1.  Dormancy in solid Tumors: Implications for Prostate Cancer 
Cancer metastasis reviews  2013;32(0):10.1007/s10555-013-9422-z.
In cancer dormancy, residual tumor cells persist in a patient with no apparent clinical symptoms, only to potentially become clinically relevant at a later date. In prostate cancer (PCa), the primary tumor is often removed and many patients experience a prolonged period (>5 years) with no evidence of disease before recurrence. These characteristics make PCa an excellent candidate for the study of tumor cell dormancy. However, the mechanisms that constitute PCa dormancy have not been clearly defined. Additionally, the definition of tumor cell dormancy varies in the literature. Therefore, we have separated tumor cell dormancy in this review into three categories: (A) Micrometastatic dormancy - A group of tumor cells that cannot increase in number due to a restrictive proliferation/apoptosis equilibrium. (B) Angiogenic dormancy- A Group of tumor cells that cannot expand beyond the formation of a micrometastasis due to a lack of angiogenic potential. (C) Conditional dormancy- An individual cell or a very small number of cells that cannot proliferate without the appropriate cues from the microenvironment, but do not require angiogenesis to do so. This review aims to identify currently known markers, mechanisms and models of tumor dormancy, in particular as they relate to PCa, and highlight current opportunities for advancement in our understanding of clinical cancer dormancy.
doi:10.1007/s10555-013-9422-z
PMCID: PMC3796576  PMID: 23612741
Dormancy; disseminated tumor cells; prostate cancer; metastasis
2.  Aneuploidy and chromosomal instability: a vicious cycle driving cellular evolution and cancer genome chaos 
Cancer metastasis reviews  2013;32(0):10.1007/s10555-013-9436-6.
Aneuploidy and chromosomal instability frequently co-exist, and aneuploidy is recognized as a direct outcome of chromosomal instability. However, chromosomal instability is widely viewed as a consequence of mutations in genes involved in DNA replication, chromosome segregation and cell cycle checkpoints. Telomere attrition and presence of extra centrosomes have also been recognized as causative for errors in genomic transmission. Here, we examine recent studies suggesting that aneuploidy itself can be responsible for the procreation of chromosomal instability. Evidence from both yeast and mammalian experimental models suggest that changes in chromosome copy number can cause changes in dosage of the products of many genes located on aneuploid chromosomes. These effects on gene expression can alter the balanced stoichiometry of various protein complexes, causing perturbations of their functions. Therefore, phenotypic consequences of aneuploidy will include chromosomal instability if the balanced stoichiometry of protein machineries responsible for accurate chromosome segregation is affected enough to perturb the function. The degree of chromosomal instability will depend on specific karyotypic changes, which may be due to dosage imbalances of specific genes or lack of scaling between chromosome segregation load and the capacity of the mitotic system. We propose that the relationship between aneuploidy and chromosomal instability can be envisioned as a “vicious cycle”, where aneuploidy potentiates chromosomal instability leading to further karyotype diversity in the affected population.
doi:10.1007/s10555-013-9436-6
PMCID: PMC3825812  PMID: 23709119
3.  Exosomes in Cancer Development, Metastasis and Drug Resistance: A Comprehensive Review 
Cancer metastasis reviews  2013;32(0):10.1007/s10555-013-9441-9.
Trafficking of biological material across membranes is an evolutionary conserved mechanism and is part of any normal cell homeostasis. Such transport is comprised of active, passive, export through microparticles and vesicular transport (exosomes) that collectively maintain proper compartmentalization of important micro and macromolecules. In pathological states, such as cancer, aberrant activity of export machinery results in expulsion of a number of key proteins and microRNAs resulting in their misexpression. Exosome mediated expulsion of intracellular drugs could be another barrier in the proper action of most of the commonly used therapeutics, targeted agents and their intracellular metabolites. Over the last decade, a number of studies have revealed that exosomes cross-talk and/or influence major tumor related pathways such as hypoxia driven EMT, cancer stemness, angiogenesis and metastasis involving many cell types within the tumor microenvironment. Emerging evidence suggest that exosome secreted proteins can also propel fibroblast growth, resulting in Desmoplastic reaction (DR); a major barrier in effective cancer drug delivery. This comprehensive review highlights the advancements in the understanding of the biology of exosomes secretions and the consequence on cancer drug resistance. We propose that the successful combination of cancer treatments to tackle exosome mediated drug resistance requires an interdisciplinary understanding of these cellular exclusion mechanisms, and how secreted biomolecules are involved in cellular cross-talk within the tumor microenvironment.
doi:10.1007/s10555-013-9441-9
PMCID: PMC3843988  PMID: 23709120
Exosomes; Export Mechanisms; Cancer Drug Resistance; microRNAs
4.  Do mutator mutations fuel tumorigenesis? 
Cancer metastasis reviews  2013;32(0):353-361.
The mutator phenotype hypothesis proposes that the mutation rate of normal cells is insufficient to account for the large number of mutations found in human cancers. Consequently, human tumors exhibit an elevated mutation rate that increases the likelihood of a tumor acquiring advantageous mutations. The hypothesis predicts that tumors are composed of cells harboring hundreds of thousands of mutations, as opposed to a small number of specific driver mutations, and that malignant cells within a tumor therefore constitute a highly heterogeneous population. As a result, drugs targeting specific mutated driver genes or even pathways of mutated driver genes will have only limited anticancer potential. In addition, because the tumor is composed of such a diverse cell population, tumor cells harboring drug-resistant mutations will exist prior to the administration of any chemotherapeutic agent. We present recent evidence in support of the mutator phenotype hypothesis, major arguments against this concept, and discuss the clinical consequences of tumor evolution fueled by an elevated mutation rate. We also consider the therapeutic possibility of altering the rate of mutation accumulation. Most significantly, we contend that there is a need to fundamentally reconsider current approaches to personalized cancer therapy. We propose that targeting cellular pathways that alter the rate of mutation accumulation in tumors will ultimately prove more effective than attempting to identify and target mutant driver genes or driver pathways.
doi:10.1007/s10555-013-9426-8
PMCID: PMC3987827  PMID: 23592419
Mutator phenotype; Mutation; Heterogeneity; Cancer genome sequencing; Tumor evolution
5.  Chemokines in tumor angiogenesis and metastasis 
Cancer metastasis reviews  2007;26(0):453-467.
Chemokines are a large group of low molecular weight cytokines that are known to selectively attract and activate different cell types. Although the primary function of chemokines is well recognized as leukocyte attractants, recent evidences indicate that they also play a role in number of tumor-related processes, such as growth, angiogenesis and metastasis. Chemokines activate cells through cell surface seven trans-membranes, G-protein-coupled receptors (GPCR). The role played by chemokines and their receptors in tumor pathophysiology is complex as some chemokines favor tumor growth and metastasis, while others may enhance anti-tumor immunity. These diverse functions of chemokines establish them as key mediators between the tumor cells and their microenvironment and play critical role in tumor progression and metastasis. In this review, we present some of the recent advances in chemokine research with special emphasis on its role in tumor angiogenesis and metastasis.
doi:10.1007/s10555-007-9068-9
PMCID: PMC4237067  PMID: 17828470
Chemokines; Tumor growth; Angiogenesis; Metastasis; Tumor microenvironment
6.  The role of epithelial plasticity in prostate cancer dissemination and treatment resistance 
Cancer metastasis reviews  2014;33(0):441-468.
Nearly 30,000 men die annually in the USA of prostate cancer, nearly uniformly from metastatic dissemination. Despite recent advances in hormonal, immunologic, bone-targeted, and cytotoxic chemotherapies, treatment resistance and further dissemination are inevitable in men with metastatic disease. Emerging data suggests that the phenomenon of epithelial plasticity, encompassing both reversible mesenchymal transitions and acquisition of stemness traits, may underlie this lethal biology of dissemination and treatment resistance. Understanding the molecular underpinnings of this cellular plasticity from preclinical models of prostate cancer and from biomarker studies of human metastatic prostate cancer has provided clues to novel therapeutic approaches that may delay or prevent metastatic disease and lethality over time. This review will discuss the preclinical and clinical evidence for epithelial plasticity in this rapidly changing field and relate this to clinical phenotype and resistance in prostate cancer while suggesting novel therapeutic approaches.
doi:10.1007/s10555-013-9483-z
PMCID: PMC4230790  PMID: 24414193
Epithelial plasticity; Prostate cancer; Metastasis; Epithelial–mesenchymal transition; Dissemination; Stem cell
7.  Microenvironmental acidosis in carcinogenesis and metastases: new strategies in prevention and therapy 
Cancer Metastasis Reviews  2014;33(4):1095-1108.
Much effort is currently devoted to developing patient-specific cancer therapy based on molecular characterization of tumors. In particular, this approach seeks to identify driver mutations that can be blocked through small molecular inhibitors. However, this approach is limited by extensive intratumoral genetic heterogeneity, and, not surprisingly, even dramatic initial responses are typically of limited duration as resistant tumor clones rapidly emerge and proliferate. We propose an alternative approach based on observations that while tumor evolution produces genetic divergence, it is also associated with striking phenotypic convergence that loosely correspond to the well-known cancer “hallmarks”. These convergent properties can be described as driver phenotypes and may be more consistently and robustly expressed than genetic targets. To this purpose, it is necessary to identify strategies that are critical for cancer progression and metastases, and it is likely that these driver phenotypes will be closely related to cancer “hallmarks”. It appears that an antiacidic approach, by targetting a driver phenotype in tumors, may be thought as a future strategy against tumors in either preventing the occurrence of cancer or treating tumor patients with multiple aims, including the improvement of efficacy of existing therapies, possibly reducing their systemic side effects, and controlling tumor growth, progression, and metastasis. This may be achieved with existing molecules such as proton pump inhibitors (PPIs) and buffers such as sodium bicarbonate, citrate, or TRIS.
doi:10.1007/s10555-014-9531-3
PMCID: PMC4244550  PMID: 25376898
Acidity; Cancer; Microenvironment; pH gradient; Proton export mechanisms; Proton pump inhibitors
8.  Towards an understanding of the structure and function of MTA1 
Cancer Metastasis Reviews  2014;33(4):857-867.
Gene expression is controlled through the recruitment of large coregulator complexes to specific gene loci to regulate chromatin structure by modifying epigenetic marks on DNA and histones. Metastasis-associated protein 1 (MTA1) is an essential component of the nucleosome remodelling and deacetylase (NuRD) complex that acts as a scaffold protein to assemble enzymatic activity and nucleosome targeting proteins. MTA1 consists of four characterised domains, a number of interaction motifs, and regions that are predicted to be intrinsically disordered. The ELM2-SANT domain is one of the best-characterised regions of MTA1, which recruits histone deacetylase 1 (HDAC1) and activates the enzyme in the presence of inositol phosphate. MTA1 is highly upregulated in several types of aggressive tumours and is therefore a possible target for cancer therapy. In this review, we summarise the structure and function of the four domains of MTA1 and discuss the possible functions of less well-characterised regions of the protein.
doi:10.1007/s10555-014-9513-5
PMCID: PMC4244562  PMID: 25352341
Metastasis associated protein 1; Corepressor complexes; Chromatin; Inositol phosphate; Transcriptional regulation
9.  MTA1—a stress response protein: a master regulator of gene expression and cancer cell behavior 
Cancer Metastasis Reviews  2014;33(4):1001-1009.
Gene mutation’s role in initiating carcinogenesis has been controversial, but it is consensually accepted that both carcinogenesis and cancer metastasis are gene-regulated processes. MTA1, a metastasis-associated protein, has been extensively researched, especially regarding its role in cancer metastasis. In this review, I try to elucidate MTA1’s role in both carcinogenesis and metastasis from a different angle. I propose that MTA1 is a stress response protein that is upregulated in various stress-related situations such as heat shock, hypoxia, and ironic radiation. Cancer cells are mostly living in a stressful environment of hypoxia, lack of nutrition, and immune reaction attacks. To cope with all these stresses, MTA1 expression is upregulated, plays a role of master regulator of gene expression, and helps cancer cells to survive and migrate out of their original dwelling.
doi:10.1007/s10555-014-9525-1
PMCID: PMC4244563  PMID: 25332145
MTA1; Stress protein; Carcinogenesis; Metastasis; Hypoxia; Immune stress; Epithelial stem cell misplacement; Apoptosis
10.  Why anti-Bcl-2 clinical trials fail: a solution 
Cancer metastasis reviews  2014;33(1):285-294.
The alteration in expression of B cell lymphoma-2 (Bcl-2) family of protein members in cancer is involved mainly in the regulation of apoptosis. Bcl-2 family proteins are currently used as major targets in the development of methods to improve treatment outcomes for cancer patients that underwent clinical trials. Although many agents have been developed for targeting Bcl-2 in the past decade, some previous attempts to target Bcl-2 have not resulted in beneficial clinical outcome for reasons unknown. Here, we propose that this was due in part for not considering the cellular level of a different antiapoptotic protein, i.e., galectin-3 (Gal-3). Gal-3 is a member of the β-galactoside binding protein family and a multifunctional oncogenic protein which regulates cell growth, cell adhesion, cell proliferation, angiogenesis, and apoptosis. Gal-3 is the sole protein that contains the NWGR anti-death motif of the Bcl-2 family and inhibits cell apoptosis induced by chemotherapeutic agents through phosphorylation, translocation and regulation of survival signaling pathways. It is now established that Gal-3 is a candidate target protein to suppress antiapoptotic activity and anticancer drug resistance. In this review, we describe the role and relevance of Gal-3 and Bcl-2 protein family in the regulation of apoptosis and propose a novel combination therapy modality. Combination therapy that targets Gal-3 could be essential for improvement of the efficacy of Bcl-2 targeting therapy in cancers and should be studied in future clinical trials. Otherwise, not considering Gal-3 cellular level could lead to trial failure.
doi:10.1007/s10555-013-9450-8
PMCID: PMC4058422  PMID: 24338002
Apoptosis; Bcl-2; Galectin-3; Therapy
11.  Platelets and cancer: a casual or causal relationship: revisited 
Cancer metastasis reviews  2014;33(1):231-269.
Human platelets arise as subcellular fragments of megakaryocytes in bone marrow. The physiologic demand, presence of disease such as cancer, or drug effects can regulate the production circulating platelets. Platelet biology is essential to hemostasis, vascular integrity, angiogenesis, inflammation, innate immunity, wound healing, and cancer biology. The most critical biological platelet response is serving as “First Responders” during the wounding process. The exposure of extracellular matrix proteins and intracellular components occurs after wounding. Numerous platelet receptors recognize matrix proteins that trigger platelet activation, adhesion, aggregation, and stabilization. Once activated, platelets change shape and degranulate to release growth factors and bioactive lipids into the blood stream. This cyclic process recruits and aggregates platelets along with thrombogenesis. This process facilitates wound closure or can recognize circulating pathologic bodies. Cancer cell entry into the blood stream triggers platelet-mediated recognition and is amplified by cell surface receptors, cellular products, extracellular factors, and immune cells. In some cases, these interactions suppress immune recognition and elimination of cancer cells or promote arrest at the endothelium, or entrapment in the microvasculature, and survival. This supports survival and spread of cancer cells and the establishment of secondary lesions to serve as important targets for prevention and therapy.
doi:10.1007/s10555-014-9498-0
PMCID: PMC4186918  PMID: 24696047
Platelet; TCIPA; Metastasis; Thrombosis; Extravasation; CTC
12.  The thromboxane synthase and receptor signaling pathway in cancer: an emerging paradigm in cancer progression and metastasis 
Cancer metastasis reviews  2011;30(0):397-408.
Thromboxane A2 (TXA2) is a biologically active metabolite of arachidonic acid formed by the action of the terminal synthase, thromboxane A2 synthase (TXA2S), on prostaglandin endoperoxide (PGH2). TXA2 is responsible for multiple biological processes through its cell surface receptor, the T-prostanoid (TP) receptor. Thromboxane A2 synthase and TP are the two necessary components for the functioning of this potent bioactive lipid. Thromboxane A2 is widely implicated in a range of cardiovascular diseases, owing to its acute and chronic effects in promoting platelet aggregation, vasoconstriction, and proliferation. In recent years, additional functional roles for both TXA2S and TP in cancer progression have been indicated. Increased cyclooxygenase (COX)-2 expression has been described in a variety of human cancers, which has focused attention on TXA2 as a downstream metabolite of the COX-2-derived PGH2. Several studies suggest potential involvement of TXA2S and TP in tumor progression, especially tumor cell proliferation, migration, and invasion that are key steps in cancer progression. In addition, the regulation of neovascularization by TP has been identified as a potent source of control during oncogenesis. There have been several recent reviews of TXA2S and TP but thus far none have discussed its role in cancer progression and metastasis in depth. This review will focus on some of the more recent findings and advances with a significant emphasis on understanding the functional role of TXA2S and TP in cancer progression and metastasis.
doi:10.1007/s10555-011-9297-9
PMCID: PMC4175445  PMID: 22037941
Thromboxane synthase; Thromboxane receptor; Cyclooxygenase; Cancer progression; Metastasis; Angiogenesis; Cell migration; Apoptosis
13.  Bone marrow fat: linking adipocyte-induced inflammation with skeletal metastases 
Cancer metastasis reviews  2014;33(0):527-543.
Adipocytes are important but underappreciated components of bone marrow microenvironment, and their numbers greatly increase with age, obesity, and associated metabolic pathologies. Age and obesity are also significant risk factors for development of metastatic prostate cancer. Adipocytes are metabolically active cells that secrete adipokines, growth factors, and inflammatory mediators; influence behavior and function of neighboring cells; and have a potential to disturb local milleu and dysregulate normal bone homeostasis. Increased marrow adiposity has been linked to bone marrow inflammation and osteoporosis of the bone, but its effects on growth and progression of prostate tumors that have metastasized to the skeleton are currently not known. This review focuses on fat-bone relationship in a context of normal bone homeostasis and metastatic tumor growth in bone. We discuss effects of marrow fat cells on bone metabolism, hematopoiesis, and inflammation. Special attention is given to CCL2- and COX-2-driven pathways and their potential as therapeutic targets for bone metastatic disease.
doi:10.1007/s10555-013-9484-y
PMCID: PMC4154371  PMID: 24398857
Prostate cancer; Bone metastasis; Adipocytes; Inflammation; COX-2; CCL2
14.  Bone-targeting agents in prostate cancer 
Cancer metastasis reviews  2014;33(0):619-628.
Bone metastases are present in the vast majority of men with advanced prostate cancer, representing the main cause for morbidity and mortality. Recurrent or metastatic disease is managed initially with androgen deprivation but the majority of the patients eventually will progress to castration-resistant prostate cancer, with patients developing bone metastases in most of the cases. Survival and growth of the metastatic prostate cancer cells is dependent on a complex microenvironment (onco-niche) that includes the osteoblasts, the osteoclasts, the endothelium, and the stroma. This review summarizes agents that target the pathways involved in this complex interaction between prostate cancer and bone micro-environment and aim to transform lethal metastatic prostate cancer into a chronic disease.
doi:10.1007/s10555-013-9480-2
PMCID: PMC4087085  PMID: 24398856
Bone-targeting agents; Prostate cancer; Bone metastases
15.  Growth factor and signaling pathways and their relevance to prostate cancer therapeutics 
Cancer metastasis reviews  2014;33(0):581-594.
Treatments that target the androgen axis represent an effective strategy for patients with advanced prostate cancer, but the disease remains incurable and new therapeutic approaches are necessary. Significant advances have recently occurred in our understanding of the growth factor and signaling pathways that are active in prostate cancer. In conjunction with this, many new targeted therapies with sound pre-clinical rationale have entered clinical development and are being tested in men with castration-resistant prostate cancer. Some of the most relevant pathways currently being exploited for therapeutic gain are HGF/c-Met signaling, the PI3K/AKT/mTOR pathway, Hedgehog signaling, the endothelin axis, Src kinase signaling, the IGF pathway, and angiogenesis. Here, we summarize the biological basis for the use of selected targeted agents and the results from available clinical trials of these drugs in men with prostate cancer.
doi:10.1007/s10555-013-9475-z
PMCID: PMC4090293  PMID: 24402967
Prostate cancer; Angiogenesis; mTOR; c-Met; Hedgehog pathway; Insulin-like growth factor pathway
16.  Insulin-like growth factor receptor-1 (IGF-IR) as a target for prostate cancer therapy 
Cancer metastasis reviews  2014;33(0):607-617.
Prostate cancer is the most commonly diagnosed cancer in men and is the second leading cause of cancer-related deaths in men each year. Androgen-deprivation therapy is and has been the gold standard of care for advanced or metastatic prostate cancer for decades. While this treatment strategy initially shows benefit, eventually tumors recur as castration-resistant prostate cancer (CRPC) for which there are limited treatment options with only modest survival benefit. Upregulation of the insulin-like growth factor receptor type I (IGF-IR) signaling axis has been shown to drive the survival of prostate cancer cells in many studies. As many IGF-IR blockades have been developed, few have been tested pre-clinically and even fewer have entered clinical trials for prostate cancer therapy. In this review, we will update the most recent pre-clinical and clinical studies of IGF-IR therapy for prostate cancer. We will also discuss the challenges for IGF-IR targeted therapies to achieve clinical benefit for prostate cancer.
doi:10.1007/s10555-013-9482-0
PMCID: PMC4096322  PMID: 24414227
IGF-IR; Prostate Cancer; Metastasis; Mechanisms; Therapy
17.  The genetic/metabolic transformation concept of carcinogenesis 
Cancer metastasis reviews  2012;31(0):123-130.
The carcinogenesis process is poorly understood and subject to varying concepts and views. A rejuvenated interest has arisen regarding the role of altered cellular intermediary metabolism in the development and progression of cancer. As a result, differing views of the implications of altered metabolism in the development of cancer exist. None of the concepts recognize and incorporate the principles of cell metabolism to cell activity, which are applicable to all cells including the carcinogenesis process. This presentation incorporates a novel concept of carcinogenesis that includes a “genetic/metabolic” transformation that encompasses these principles of cell metabolism to cell activity. The intermediary metabolism transformation is essential to provide the bioenergetic/ synthetic, growth/proliferation, and migration/invasive events of malignancy. The concept invokes an “oncogenetic transformation” for the development of neoplastic cells from their precursor normal cells; and a required “genetic/metabolic” transformation for facilitation of the development of the neoplastic cells to malignant cells with the manifestation of the malignant process. Such a concept reveals stages and events of carcinogenesis that provide approaches for the identification of biomarkers and for development of therapeutic agents. The presentation discusses the contemporary application of genetics and proteomics to altered cellular metabolism in cancer; and underscores the importance of proper integration of genetics and proteomics with biochemical and metabolic studies, and the consequences of inappropriate studies.
doi:10.1007/s10555-011-9334-8
PMCID: PMC4107361  PMID: 22109079
Carcinogenesis; Genetic/metabolic transformation; Tumor metabolism; Metabolic malignant transformation
18.  Regulation of the metastatic cell phenotype by sialylated glycans 
Cancer metastasis reviews  2012;31(0):501-518.
Tumor cells exhibit striking changes in cell surface glycosylation as a consequence of dysregulated glycosyltransferases and glycosidases. In particular, an increase in the expression of certain sialylated glycans is a prominent feature of many transformed cells. Altered sialylation has long been associated with metastatic cell behaviors including invasion and enhanced cell survival; however, there is limited information regarding the molecular details of how distinct sialylated structures or sialylated carrier proteins regulate cell signaling to control responses such as adhesion/migration or resistance to specific apoptotic pathways. The goal of this review is to highlight selected examples of sialylated glycans for which there is some knowledge of molecular mechanisms linking aberrant sialylation to critical processes involved in metastasis.
doi:10.1007/s10555-012-9359-7
PMCID: PMC4079276  PMID: 22699311
Sialylation; Metastatic cell phenotype; Sialylated glycoproteins; Invasion
19.  Genomics screens for metastasis genes 
Cancer metastasis reviews  2012;31(0):419-428.
Metastasis is responsible for most cancer mortality. The process of metastasis is complex, requiring the coordinated expression and fine regulation of many genes in multiple pathways in both the tumor and host tissues. Identification and characterization of the genetic programs that regulate metastasis is critical to understanding the metastatic process and discovering molecular targets for the prevention and treatment of metastasis. Genomic approaches and functional genomic analyses can systemically discover metastasis genes. In this review, we summarize the genetic tools and methods that have been used to identify and characterize the genes that play critical roles in metastasis.
doi:10.1007/s10555-012-9362-z
PMCID: PMC4071451  PMID: 22684367
Metastasis; Genomic screen; Functional genomics; Next-generation sequencing
20.  The role of MAP kinases and MAP kinase phosphatase-1 in resistance to breast cancer treatment 
Cancer metastasis reviews  2010;29(1):143-149.
Chemotherapy resistance is an important problem often encountered during the course of breast cancer treatment. In order to design rational and efficacious therapies, the molecular mechanisms used by cells to develop resistance must be investigated. One mechanism employed by cancer cells is to alter cell signaling. This review examines the role of mitogen-activated protein kinases (MAPKs) and their endogenous negative regulators, mitogen-activated protein kinase phosphatases (MKPs), in chemotherapy resistance in breast cancer. MAPK signaling is activated in response to both growth factors and cellular stress. MKPs dephosphorylate MAPKs and are part of the dual-specificity family of phosphatases. MAPKs have been shown to be involved in resistance to tamoxifen, and MKPs have been linked to resistance to treatment with doxorubicin, mechlorethamine, paclitaxel, proteasome inhibitors, and oxidative-stress-induced cell death in breast cancer. The role of MKPs in tamoxifen resistance and the elucidation of the mechanisms involved with resistance to standard chemotherapy agents need to be investigated further. Growing evidence suggests that modulating MKP-1 activity could be a viable option to make breast cancer chemotherapy more effective.
doi:10.1007/s10555-010-9208-5
PMCID: PMC4063276  PMID: 20111893
MKP-1; MAP kinase; Breast cancer; Endocrine therapy; Chemotherapy; Resistance
21.  Animal Models of Leukemia: Any closer to the real thing? 
Cancer metastasis reviews  2013;32(0):63-76.
Animal models have been invaluable in the efforts to better understand and ultimately treat patients suffering from leukemia. While important insights have been gleaned from these models, limitations must be acknowledged. In this review, we will highlight the various animal models of leukemia and describe their contributions to the improved understanding and treatment of these cancers.
doi:10.1007/s10555-012-9405-5
PMCID: PMC3568447  PMID: 23081702
22.  Animal Models of Colorectal Cancer 
Cancer metastasis reviews  2013;32(0):39-61.
Colorectal cancer is a heterogeneous disease that afflicts a large number of people in the United States. The use of animal models has the potential to increase our understanding of carcinogenesis, tumor biology, and the impact of specific molecular events on colon biology. In addition, animal models with features of specific human colorectal cancers can be used to test strategies for cancer prevention and treatment. In this review we provide an overview of the mechanisms driving human cancer, we discuss the approaches one can take to model colon cancer in animals, and we describe a number of specific animal models that have been developed for the study of colon cancer. We believe that there are many valuable animal models to study various aspects of human colorectal cancer. However, opportunities for improving upon these models exist.
doi:10.1007/s10555-012-9404-6
PMCID: PMC3572245  PMID: 23076650
sporadic; heritable; chemically-induced; genetically modified mice
23.  Heading off with the herd: How cancer cells might maneuver supernumerary centrosomes for directional migration 
Cancer metastasis reviews  2013;32(0):269-287.
The complicity of centrosomes in carcinogenesis is unmistakable. Mounting evidence clearly implicates a robust correlation between centrosome amplification (CA) and malignant transformation in diverse tissue types. Furthermore, CA has been suggested as a marker of cancer aggressiveness, in particular the invasive phenotype, in breast and prostate cancers. One means by which CA promotes malignancy is through induction of transient spindle multipolarity during mitosis, which predisposes the cell to karyotypic changes arising from low-grade chromosome mis-segregation. It is well recognized that during cell migration in interphase, centrosome-mediated nucleation of a radial microtubule array is crucial for establishing a polarized Golgi apparatus, without which directionality is precluded. The question of how cancer cells maneuver their supernumerary centrosomes to achieve directionality during cell migration is virtually uncharted territory. Given CA is a hallmark of cancers and has been correlated with cancer aggressiveness, malignant cells are presumably competent in managing their centrosome surfeit during directional migration, although the cellular logistics of this process remain unexplored. Thus, another key angle worth pondering is whether an overabundance of centrosomes confers some advantage on cancer cells in terms of their migratory and invasive capabilities. Recent studies have uncovered a remarkable strategy that cancer cells employ to deal with the problem of excess centrosomes and ensure bipolar mitoses, viz., centrosome clustering. This review aims to change the narrative by exploring how an increased centrosome complement may, via aneuploidy-independent modulation of the microtubule cytoskeleton, enhance directional migration and invasion of malignant cells. We postulate that CA imbues cancer cells with cytoskeletal advantages that enhance cell polarization, Golgi-dependent vesicular trafficking, stromal invasion and other aspects of metastatic progression. We also propose that centrosome declustering may represent a novel, cancer cell-specific anti-metastatic strategy, as cancer cells may rely on centrosome clustering during migration as they do in mitosis. Elucidation of these details offers an exciting avenue for future research, as does investigating how CA may promote metastasis through enhanced directional migration.
doi:10.1007/s10555-012-9413-5
PMCID: PMC3581755  PMID: 23114845
24.  Modeling prostate cancer in mice: Something old, something new, something premalignant, something metastatic 
Cancer metastasis reviews  2013;32(0):109-122.
More than 15 years ago the first generation of genetically-engineered mouse (GEM) models of prostate cancer was introduced. These transgenic models utilized prostate-specific promoters to express SV40 oncogenes specifically in prostate epithelium. Since the description of these initial models, there have been a plethora of GEM models of prostate cancer, representing various perturbations of oncogenes or tumor suppressors, either alone or in combination. This review describes these GEM models, focusing on their relevance for human prostate cancer and highlighting their strengths and limitations, as well as opportunities for the future.
doi:10.1007/s10555-012-9409-1
PMCID: PMC3584242  PMID: 23114843
25.  What underlies the diversity of brain tumors? 
Cancer metastasis reviews  2013;32(0):5-24.
Glioma and medulloblastoma represent the most commonly occurring malignant brain tumors in adults and in children respectively. Recent genomic and transcriptional approaches present a complex group of diseases, and delineate a number of molecular subgroups within tumors that share a common histopathology. Differences in cells of origin, regional niches, developmental timing and genetic events all contribute to this heterogeneity. In an attempt to recapitulate the diversity of brain tumors, an increasing array of genetically engineered mouse models (GEMMs) has been developed. These models often utilize promoters and genetic drivers from normal brain development, and can provide insight into specific cells from which these tumors originate. GEMMs show promise in both developmental biology and developmental therapeutics. This review describes numerous murine brain tumor models in the context of normal brain development, and the potential for these animals to impact brain tumor research.
doi:10.1007/s10555-012-9407-3
PMCID: PMC3586981  PMID: 23085857
development; medulloblastoma; glioma; murine model; transgene

Results 1-25 (108)