Cancer initiating cells or cancer stem cells in the gastrointestinal tract and liver

It has been suggested that cancer stem cells population within the solid tumor with indefinite proliferation potential drives the growth and metastasis of cancer. In literature, these malignant stem cells also named Cancer initiating cells. Cancer stem cells exhibit low rate of division and proliferation in their niche that help them to avoid chemotherapy and radiation. Epithelial cancers are believed to originate from transformation of tissue stem cells. Bone marrow-derived cells, which are frequently recruited to sites of tissue injury and inflammation, might also represent a potential source of malignancy in the gastrointestinal tract. Pancreatic cancer is one of most common cause of cancer-related death. Pancreatic cancer stem cells have been characterized recently through serial transplantation of human pancreatic cancer cells. The phenotype of Pancreatic cancer stem cells has been defined as CD24(+)CD44(+)CD326 (ESA)(+). CD133 antigen has been also suggested as a potential marker for cancer stem cell in gastrointestinal tract but recently there is also debate in this regard. More recently, other cancer stem cells in gastrointestinal tract, such as colon cancer stem cells, liver cancer stem cells, have been also characterized in their phenotype. These advances clearly will bring the new strategy in cancer treatment and control in the gastrointestinal tract. In this review, the author will discuss the current status and progress about cancer stem cell research in gastrointestinal tract and liver.     

Bioengineering approaches to mature induced pluripotent stem cell-derived atrial cardiomyocytes to model atrial fibrillation

Induced pluripotent stem cells (iPSCs) serve as a robust platform to model several human arrhythmia syndromes including atrial fibrillation (AF). However, the structural, molecular, functional, and electrophysiological parameters of patient-specific iPSC-derived atrial cardiomyocytes (iPSC-aCMs) do not fully recapitulate the mature phenotype of their human adult counterparts. The use of physiologically inspired microenvironmental cues, such as postnatal factors, metabolic conditioning, extracellular matrix (ECM) modulation, electrical and mechanical stimulation, co-culture with non-parenchymal cells, and 3D culture techniques can help mimic natural atrial development and induce a more mature adult phenotype in iPSC-aCMs. Such advances will not only elucidate the underlying pathophysiological mechanisms of AF, but also identify and assess novel mechanism-based therapies towards supporting a more ‘personalized’ (i.e. patient-specific) approach to pharmacologic therapy of AF.     

Hypoxia,partial EMT and collective migration: Emerging culprits in metastasis

Epithelial-mesenchymal transition (EMT) is a cellular biological process involved in migration of primary cancer cells to secondary sites facilitating metastasis. Besides, EMT also confers properties such as stemness, drug resistance and immune evasion which can aid a successful colonization at the distant site. EMT is not a binary process; recent evidence suggests that cells in partial EMT or hybrid E/M phenotype(s) can have enhanced stemness and drug resistance as compared to those undergoing a complete EMT. Moreover, partial EMT enables collective migration of cells as clusters of circulating tumor cells or emboli, further endorsing that cells in hybrid E/M phenotypes may be the ‘fittest’ for metastasis. Here, we review mechanisms and implications of hybrid E/M phenotypes, including their reported association with hypoxia. Hypoxia-driven activation of HIF-1α can drive EMT. In addition, cyclic hypoxia, as compared to acute or chronic hypoxia, shows the highest levels of active HIF-1α and can augment cancer aggressiveness to a greater extent, including enriching for a partial EMT phenotype. We also discuss how metastasis is influenced by hypoxia, partial EMT and collective cell migration, and call for a better understanding of interconnections among these mechanisms. We discuss the known regulators of hypoxia, hybrid EMT and collective cell migration and highlight the gaps which needs to be filled for connecting these three axes which will increase our understanding of dynamics of metastasis and help control it more effectively.     

Impact of the non-cellular tumor microenvironment on metastasis: potential therapeutic and imaging opportunities

Evidence is accumulating that the malignant phenotype of a given tumor is dependent not only on the intrinsic characteristics of tumor cells, but also on the cooperative interactions of non-neoplastic cells, soluble secreted factors and the non-cellular solid-state ECM network that comprise the tumor microenvironment. Given the ability of the tumor microenvironment to regulate the cellular phenotype, recent efforts have focused on understanding the molecular mechanisms by which cells sense, assimilate, interpret, and ultimately respond to their immediate surroundings. Exciting new studies are beginning to unravel the complex interactions between the numerous cell types and regulatory factors within the tumor microenvironment that function cooperatively to control tumor cell invasion and metastasis. Here, we will focus on studies concerning a common theme, which is the central importance of the non-cellular solid-state compartment as a master regulator of the malignant phenotype. We will highlight the non-cellular solid-state compartment as a relatively untapped source of therapeutic and imaging targets and how cellular interactions with these targets may regulate tumor metastasis.     

Surface markers on the T cells that regulate cytotoxic T-cell responses I. The Ly phenotype of suppressor T cells changes as a function of time, and is distinct from that of helper or cytotoxic T cells

Regulatory T cells can be obtained from primary mixed lymphocyte cultures of CBA spleen cells responding to BALB/c stimulators. At day 3 of culture, T cells are generated which can either help or suppress the generation of cytotoxic T cells in a second primary MLC culture. The regulatory activity observed depends on the conditions employed in the assay system allowing independent assay of different functional cell types which coexist in the cultures. Both the helper activity and the suppressor activity are mediated by differentiated antigen-specific T cells whose function is radioresistant. The Ly phenotype of these regulatory cells was tested. At day 3 of the first-step culture, the phenotype of the helper cells is Ly 1.1+ Ly 2.1-, whereas the inhibitory cells are Ly 1.1 Ly 2.1+. At day 5 of M LC culture, suppressor activity and helper activity are also observed. However, at this point, a suppressor cell which is Ly 1.1-Ly 2.1+ represents the major inhibitory activity. It is not clear whether this change in suppressor cell phenotype as a function of time in culture represents one differentiation pathway or cells derived from two different precursor cells. The Ly phenotype of helper or cytotoxic T cells did not change as a function of time in culture. In day 5 first-step cells, the cytotoxic cells were typed as Ly 1.1+ 2.1+, whereas the inhibitory cells present in aliquots of the same treated cell population expressed the Ly 1.1- Ly 2.1 phenotype. Taken together, these observations show that the antigen-specific suppressor cells and helper cells which regulate the generation of cytotoxicity, and the cytotoxic cells themselves represent physically distinct subclasses of T cells.     

Characterization of a murine gene homologous to the bovine CaCC chloride channel

The bovine CaCC protein is a putative Ca2+-dependent Cl- channel of airway epithelial cells. Therefore, CaCC proteins could contribute to transepithelial Cl- transport and accordingly modify the phenotype of cystic fibrosis (CF) patients. We have identified a murine EST containing a full-length cDNA coding for a 902-amino-acid protein highly homologous to bovine CaCC. The murine gene (mCaCC) maps to chromosome 3 at the H2-H3 band and is expressed, as indicated by Northern blot analysis, in mouse skin and kidney but not in brain, heart, lung or testis. RT-PCR indicates a low expression in tracheal epithelial cells. Heterologous expression of mCaCC in Xenopus oocytes elicits membrane currents that are anion-selective and inhibited by DIDS and by niflumic acid, a blocker of the endogenous chloride current in oocytes. The identification of genes belonging to the CaCC family will help to evaluate their role as ion channels or channel regulators and their actual contribution to epithelial chloride transport.     

T-B collaboration in the in vitro anti-Sm autoantibody response of MRL/Mp-lpr/lpr mice

Spontaneous production of autoantibodies to the Sm nuclear Ag is highly specific for SLE and the SLE-prone MRL mouse strains. Our previous studies have demonstrated that in vitro anti-Sm production in MRL/1pr mice requires the presence of T cells. In the present investigation, these T cells were found to express the L3T4+/Lyt-2- phenotype, unlike the aberrant L3T4-/Lyt-2-"double negative" 1pr T cells, and to utilize the L3T4 determinant in generating help for the anti-Sm response. The generation of anti-Sm did not require the presence of Sm-specific Th cells, as help could also be provided by T cells activated to an irrelevant Ag, or by nonspecific factors such as IL-2. There was no evidence for suppressor cell regulation of anti-Sm, even in animals negative for this specificity. These studies indicate that ongoing production of anti-Sm in MRL/1pr mice is dependent on the presence of T cells with a normal mature surface phenotype, and that these cells act in part through the elaboration of lymphokines. They further show that the anti-Sm status of individual MRL/1pr mice is not due to the action of suppressor cells. Because T cells appear to act primarily in a permissive fashion for the anti-Sm response, it is likely that events underlying the initial generation of Sm-specific B cell precursors are critical in determining whether an individual animal develops the Sm serologic specificity. Once these cells have arisen, clonal expansion of Sm-specific B cells may proceed in the presence of activated T cells or some of their products.     

Convergent mechanisms in pluripotent stem cells and cancer: Implications for stem cell engineering

Stem cells and cancer cells share certain characteristics, including the capacity to self-renew, differentiatie, and undergo epithelial-to-mesenchymal transition (EMT). The mechanisms underlying tumorigenesis retain similarities with processes in normal stem cell development. Comprehensive analysis and comparison of cancer cell and stem cell development will advance the study of cancer progression, enabling development of effective strategies for cancer treatment. In this review article, we first examine the convergence of outcome, cellular communication, and signaling pathways active in pluripotent stem cells and cancer cells. Next, we detail how stem cell engineering is able to mimic in vivo microenvironments. These efforts can help better identify stem cell-cancer cell interactions, elucidated dysregulated pluripotent signaling pathways occurring in cancer, revealed new factors that restrict tumorigenesis and metastasis potential, and reprogrammed cancer cells to a less aggressive phenotype. The potential of stem cell engineering to enhance cancer research is tremendous and may lead to alternative therapeutic options for aggressive cancers.     

Growth of cancer cell lines under stem cell-like conditions has the potential to unveil therapeutic targets

Malignant tumors comprise a small proportion of cancer-initiating cells (CIC), capable of sustaining tumor formation and growth. CIC are the main potential target for anticancer therapy. However, the identification of molecular therapeutic targets in CIC isolated from primary tumors is an extremely difficult task. Here, we show that after years of passaging under differentiating conditions, glioblastoma, mammary carcinoma, and melanoma cell lines contained a fraction of cells capable of forming spheroids upon in vitro growth under stem cell-like conditions. We found an increased expression of surface markers associated with the stem cell phenotype and of oncogenes in cell lines and clones cultured as spheroids vs. adherent cultures. Also, spheroid-forming cells displayed increased tumorigenicity and an altered pattern of chemosensitivity. Interestingly, also from single retrovirally marked clones, it was possible to isolate cells able to grow as spheroids and associated with increased tumorigenicity. Our findings indicate that short-term selection and propagation of CIC as spheroid cultures from established cancer cell lines, coupled with gene expression profiling, represents a suitable tool to study and therapeutically target CIC: the notion of which genes have been down-regulated during growth under differentiating conditions will help find CIC-associated therapeutic targets.     

DNA methylation: a promising landscape for immune system-related diseases

During hematopoiesis, a unique hematopoietic stem cell (HSC) from the bone marrow gives rise to a subset of mature blood cells that directs all the immune responses. Recent studies have shown that this well-defined, hierarchical process is regulated in part by epigenetic mechanisms. Changes in the DNA methylation profile have a critical role in the division of these stem cells into the myeloid and lymphoid lineages and in the establishment of a specific phenotype and functionality in each terminally differentiated cell type. In this review, we describe how the DNA methylation patterns are modified during hematopoietic differentiation and what their role is in cell plasticity and immune function. An in-depth knowledge of these epigenetic mechanisms will help clarify how cell type-specific gene programs are established, and how they can be leveraged in the development of novel strategies for treating immune system-related pathologies.     

Senescent cells at the crossroads of aging,disease, and tissue homeostasis

Originally identified as an outcome of continuous culture of primary cells, cellular senescence has moved beyond the culture dish and is now a bona fide driver of aging and disease in animal models, and growing links to human disease. This cellular stress response consists of a stable proliferative arrest coupled to multiple phenotypic changes. Perhaps the most important of these is the senescence-associated secretory phenotype, or senescence-associated secretory phenotype —a complex and variable collection of secreted molecules release by senescent cells with a number of potent biological activities. Senescent cells appear in multiple age-associated conditions in humans and mice, and interventions that eliminate these cells can prevent or even reverse multiple diseases in mouse models. Here, we review salient aspects of senescent cells in the context of human disease and homeostasis. Senescent cells increase in abundance during several diseases that associated with premature aging. Conversely, senescent cells have a key role in beneficial processes such as development and wound healing, and thus can help maintain tissue homeostasis. Finally, we speculate on mechanisms by which deleterious aspects of senescent cells might be targeted while retaining homeostatic aspects in order to improve age-related outcomes.     

Biochemical, Genetic, and Metabolic Adaptations of Tumor Cells That Express the Typical Multidrug-Resistance Phenotype. Reversion by New Therapies

Among the genetic and metabolic alterations that cancer cells undergo, several allow their survival under extreme environmental conditions. The resulting aberrant metabolism is compatible with tumor progression at the expenses of high energy needs, especially for maintaining high division rates. When treated with chemotherapeutic drugs many cancer cells take advantage of their ability to develop a resistance phenotype, as part of an adaptative mechanism. Two main actors of this multidrug phenotype (MDR) are represented by the P-glycoprotein and by the more recently discovered multidrug-resistance associated protein (MRP), two membrane proteins of the ABC superfamily of transporters that can extrude chemotherapeutic drugs under an ATP-dependent mechanism. We will briefly review the major metabolic aberrations that several cancers develop, followed by the molecular, genetic, structural, and functional aspects related mainly to P-glycoprotein, with a concern for the regulation of mdr gene expression. We will point out the role that membrane cholesterol may play in the MDR phenotype, relate this phenotype to bioenergetic considerations, and review the ways of modulating it by the use of new therapeutic approaches.     

Lentiviral-Mediated RNAi Knockdown of Cbfa1 Gene Inhibits Endochondral Ossification of Antler Stem Cells in Micromass Culture

Articular cartilage (AC) lacks ability to repair defects due to its avascular nature as healing process relies on cells being brought in by blood vessels. Multiple approaches have been taken to facilitate cartilage repair in clinics, to date there is no effective treatment available that can restores the AC lesion to a normally functioning level over extended periods. In this regard, antler cartilage is unique in being richly vascularised and hence can effectively repair and regenerate. Interestingly, antler stem cells, from which the vascularised cartilage is derived, can form avascular cartilage when taken away from their original niche, suggesting that the vascular or avascular state of antler cartilage is controlled by extrinsic factors. Understanding the mechanisms underlying this phenotype switch may help us to devise a way to trigger the effective intrinsic repair of AC. However, adoption of antler cartilage model for AC repair requires the demonstration that the cartilage specific signalling pathways also prevail in antler chondrogenesis. To achieve this, in the present study we silenced expression of Cbfa1, a key factor regulatingendochondral ossification, using RNAi, and showed that expression of the downstream genes type I collagen and osteocalcin were suppressed which, in turn, inhibited endochondral ossification process taking place in the antler stem cell-formed nodules. Therefore, we provided further evidence at molecular level that antler could be developed as novel model for the study of AC repair. The eventual identification of the extrinsic factors dictating the phenotype switch between the vascular and avascular state of antler cartilage will open up a new avenue for the cure of osteoarthritis.     

Th1 and Th2 CD4+ T cells provide help for B cell clonal expansion and antibody synthesis in a similar manner in vivo

The relative ability of Th1 and Th2 T cells to help B cells remains controversial as do the mechanisms by which both T cell subsets provide help in vivo. Whether this help affects the clonal expansion and/or differentiation of B cells has been difficult to assess due to the low frequency of Ag-specific T and B lymphocytes. We have employed a novel technique to directly monitor the clonal expansion of Ag-specific T and B lymphocytes in vivo. OVA-specific TCR transgenic T lymphocytes were polarized toward a Th1 or Th2 phenotype in vitro. These cells were then transferred into syngeneic recipients, along with B cell receptor transgenic hen egg lysozyme-specific B lymphocytes. Our results indicate that Th1 and Th2 cells support B cell responses to a similar extent in vivo and that they achieve this in the same manner by migrating into B cell follicles to promote CD154-dependent B cell clonal expansion and Ab production.     

Kinetic analyses as a critical parameter in defining the side population (SP) phenotype

The side population (SP) phenotype has been reported as a method to identify hematopoietic stem cells in the bone marrow based upon differential staining with the fluorescent dye, Hoechst 33342. This technique has drawn great interest in the stem cell community, as it may provide a simple approach to the enrichment of progenitor cells from a variety of normal and malignant tissues. The frequency of these cells and their performance in functional assays has varied considerably within the literature. To investigate mechanisms that may contribute to the SP phenotype, we measured the fluorescence emission of Hoechst-stained bone marrow cells as a function of both time and dye concentration using a custom flow cytometer and data acquisition software. These measurements demonstrate that all nucleated cells within the bone marrow undergo an identical staining pattern at varying rates, even under conditions previously reported to abrogate the SP. Therefore, the SP phenotype is not unique to stem cells, but rather represents a transient feature of marrow cells exposed to Hoechst 33342 for varying amounts of time. We propose that heterogeneity of SP-defined populations may be a consequence of the rate at which differing cell populations accumulate Hoechst 33342. Further, we suggest that dye uptake kinetics will likely be an important factor for optimal use of Hoechst 33342 in isolating stem cells.     

Reprogramming cell fates: reconciling rarity with robustness

The stunning possibility of “reprogramming” differentiated somatic cells to express a pluripotent stem cell phenotype (iPS, induced pluripotent stem cell) and the “ground state” character of pluripotency reveal fundamental features of cell fate regulation that lie beyond existing paradigms. The rarity of reprogramming events appears to contradict the robustness with which the unfathomably complex phenotype of stem cells can reliably be generated. This apparent paradox, however, is naturally explained by the rugged “epigenetic landscape” with valleys representing “preprogrammed” attractor states that emerge from the dynamical constraints of the gene regulatory network. This article provides a pedagogical primer to the fundamental principles of gene regulatory networks as integrated dynamic systems and reviews recent insights in gene expression noise and fate determination, thereby offering a formal framework that may help us to understand why cell fate reprogramming events are inherently rare and yet so robust.     

Mesenchymal stromal cells from human perinatal tissues: From biology to cell therapy

Cell-based regenerative medicine is of growing interest in biomedical research. The role of stem cells in this context is under intense scrutiny and may help to define principles of organ regeneration and develop innovative therapeutics for organ failure. Utilizing stem and progenitor cells for organ replacement has been conducted for many years when performing hematopoietic stem cell transplantation. Since the first successful transplantation of umbilical cord blood to treat hematological malignancies, non-hematopoietic stem and progenitor cell populations have recently been identified within umbilical cord blood and other perinatal and fetal tissues. A cell population entitled mesenchymal stromal cells (MSCs) emerged as one of the most intensely studied as it subsumes a variety of capacities: MSCs can differentiate into various subtypes of the mesodermal lineage, they secrete a large array of trophic factors suitable of recruiting endogenous repair processes and they are immunomodulatory.Focusing on perinatal tissues to isolate MSCs, we will discuss some of the challenges associated with these cell types concentrating on concepts of isolation and expansion, the comparison with cells derived from other tissue sources, regarding phenotype and differentiation capacity and finally their therapeutic potential.     

G6PD-MutDB: a mutation and phenotype database of glucose-6-phosphate (G6PD) deficiency

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common hereditary enzymatic disorder of red blood cells in humans due to mutations in the G6PD gene. The G6PD enzyme catalyzes the first step in the pentose phosphate pathway to protect cells against oxidative stress. Mutations in the G6PD gene will cause functional variants with various biochemical and clinical phenotypes. So far, about 160 mutations along with more than 400 biochemical variants have been described. G6PD-MutDB is a disease-specific resource of G6PD deficiency, collecting and integrating G6PD mutations with biochemical and clinical phenotypes. Data of G6PD deficiency is manually extracted from published papers, focusing primarily on variants with identified mutation and well-described quantitative phenotypes. G6PD-MutDB implements an approach, CNSHA predictor, to help identify a potential chronic non-spherocytic hemolytic anemia (CNSHA) phenotype of an unknown mutation. G6PD-MutDB is believed to facilitate analysis of relationship between molecular mutation and functional phenotype of G6PD deficiency owing to convenient data resource and useful tools. This database is available from http://202.120.189.88/mutdb.