Roles of sphingosine 1-phosphate on tumorigenesis

Sphingosine 1-phosphate (S1P) is a bioactive sphingolipid with a variety of biological activities.It is generated from the conversion of ceramide to sphingosine by ceramidase and the subsequent conversion of sphingosine to S1P,which is catalyzed by sphingosine kinases.Through increasing its intracellular levels by sphingolipid metabolism and binding to its cell surface receptors,S1P regulates several physiological and pathological processes,including cell proliferation,migration,angiogenesis and autophagy.These processes are responsible for tumor growth,metastasis and invasion and promote tumor survival.Since ceramide and S1P have distinct functions in regulating in cell fate decision,the balance between the ceramide/sphingosine/S1P rheostat becomes a potent therapeutic target for cancer cells.Herein,we summarize our current understanding of S1P signaling on tumorigenesis and its potential as a target for cancer therapy.     

Beyond tumorigenesis： cancer stem cells in metastasis

The importance of cancer stem cells （CSCs） in tumor-initiation has been firmly established in leukemia and recently reported for a variety of solid tumors. However, the role of CSCs in multistage cancer progression, particularly with respect to metastasis, has not been well-defined. Cancer metastasis requires the seeding and successful colonization of specialized CSCs at distant organs. The biology of normal stem cells and CSCs share remarkable similarities and may have important implications when applied to the study of cancer metastasis. Furthermore, overlapping sets of molecules and pathways have recently been identified to regulate both stem cell migration and cancer metastasis. These molecules constitute a complex network of cellular interactions that facilitate both the initiation of the pre-metastasis niche by the primary tumor and the formation of a nurturing organ microenvironment for migrating CSCs. In this review, we surveyed the recent advances in this dynamic field and propose a unified model of cancer progression in which CSCs assume a central role in both tumorigenesis and metastasis. Better understanding of CSCs as a fundamental component of the metastatic cascade will lead to novel therapeutic strategies against metastatic cancer.     

Regulation of gene expression,growth,and cell survival by IL—4：Contribution of multiple signaling pathways

Interleukin-4 is a cytokine produced by activated T cells,mast cells,and basophils that elicits many important biological responses[1](see Tab 1).These responses range from the regulation of helper T cell differentiation[2] and the production of IgE[3] to the regulation of the adhesive properties of endothelial cells via VCAM-1[4],In keeping with these diverse biological effects,high-affinity binding sites for IL-4(Kd 20 to 300pM) have been detected on many hematopoietic and non-hematopoietic cell types at levels ranging from 50 to 5000 sites per cell[5].This review will focus on the discrete signal transduction pathways activated by the IL-4 recxeptor and the coordination of these individual pathways in the regulation of a final biological outcome.     

Cancer stem cell plasticity and tumor hierarchy

The origins of the complex process of intratumoral heterogeneity have been highly debated and different cellular mechanisms have been hypothesized to account for the diversity within a tumor. The clonal evolution and cancer stem cell(CSC) models have been proposed as drivers of this heterogeneity. However, the concept of cancer stem cell plasticity and bidirectional conversion between stem and non-stem cells has added additional complexity to these highly studied paradigms and may help explain the tumor heterogeneity observed in solid tumors. The process of cancer stem cell plasticity in which cancer cel s harbor the dynamic ability of shifting from a non-CSC state to a CSC state and vice versa may be modulated by specific microenvironmental signals and cellular interactions arising in the tumor niche. In addition to promoting CSC plasticity, these interactions may contribute to the cellular transformation of tumor cells and affect response to chemotherapeutic and radiation treatments by providing CSCs protection from these agents. Herein, we review the literature in support of this dynamic CSC state, discuss the effectors of plasticity, and examine their role in the development and treatment of cancer.     

Down-regulation of GPR137 expression inhibits proliferation of colon cancer cells

G protein-coupled receptors （GPRs） are highly related to oncogenesis and cancer metastasis. G protein-coupled re- ceptor 137 （GPR137） was initially reported as a novel orphan GPR about 10 years ago. Some orphan GPRs have been implicated in human cancers. The aim of this study is to investigate the role of GPR137 in human colon cancer. Expression levels of GRP137 were analyzed in different colon cancer cell lines by quantitative polymerase chain re- action and western blot analysis. Lentivirus-mediated short hairpin RNA was specifically designed to knock down GPR137 expression in colon cancer cells. Cell viability was measured by methylthiazoletetrazolium and colony forma- tion assays. In addition, cell cycle characteristic was investi- gated by flow cytometry. GRP137 expression was observed in aH seven colon cancer cell lines at different levels. The mRNA and protein levels of GPR137 were down-regulated in both HCTll6 and RKO cells after lentivirus infection. Lentivirus-mediated silencing of GPR137 reduced the proliferation rate and colonies numbers. Knockdown of GPR137 in both cell lines led to cell cycle arrest in the G0/G1 phase. These results indicated that GPR137 plays an important role in colon cancer cell proliferation. A better understanding of GPR137＇s effects on signal transduction pathways in colon cancer cells may provide insights into the novel gene therapy of colon cancer.     

Biomolecular Surfaces for the Capture and Reprogramming of Circulating Tumor Cells

Circulating Tumor Cells(CTC)have the potential to be used clinically as a diagnostic tool and a treatment tool in the fieldof oncology.As a diagnostic tool,CTC may be used to indicate the presence of a tumor before it is large enough to cause noticeablesymptoms.As a treatment tool,CTC isolated from patients may be used to test the efficacy of chemotherapy options topersonalize patient treatment.One way for tumors to spread is through metastasis via the circulatory system.CTC are able toexploit the natural leukocyte recruitment process that is initially mediated by rolling on transient selectin bonds.Our capturedevices take advantage of this naturally occurring recruitment step to isolate CTC from whole blood by flowing samples throughselectin and antibody-coated microtubes.Whole blood was spiked with a known concentration of labeled cancer cells and thenperfused through pre-coated microtubes.Microtubes were then rinsed to remove unbound cells and the number of labeled cellscaptured on the lumen was assessed.CTC were successfully captured from whole blood at a clinically relevant level on the orderof 10 cells per mL.Combination tubes with selectin and antibody coated surface exhibited higher capture rate than tubes coatedwith selectin alone or antibody alone.Additionally,CTC capture was demonstrated with the KG 1 a hematopoietic cell line andthe DU 145 epithelial cell line.Thus,the in vivo process of selectin-mediated CTC recruitment to distant vessel walls can be usedin vitro to target CTC to a tube lumen.The biomolecular coatings can also be used to capture CTC of hematopoietic andepithelial tumor origin and is demonstrated to sensitivities down to the order of 10 CTC per mL.In a related study aimed at reducing the blood borne metastatic cancer load,we have shown that cells captured to a surfacecan be neutralized by a receptor-mediated biochemical signal.In the proposed method we have shown that using a combinedselectin and TRAIL(TNF Related Apoptosis Inducing Ligand or Apo 2L)functionalized surface we are abl     

Effects of extracellular matrix components on the growth and differentiation of cultured rat hepatocytes

Summary Some effects of culturing adult rat hepatocytes on each of four different substrates—laminin (LN), collagen type I (C-I), collagen type IV (C-IV), and fibronectin (FN)—have been investigated under defined conditions. No differential effect on the attachment of the cells to the various substrates was noted; however, the spreading of hepatocytes shortly after initial plating was most strikingly enhanced by FN, whereas LN exhibited little or no such enhancement. The two collagen substrates enhanced the spreading of hepatocytes more than did LN, but less than FN. The different substrates had no differential effect on the induction of tyrosine aminotransferase by dexamethasone and glucagon for at least the first 10 d in culture. The longevity of the hepatocytes was not changed significantly by any of the substrates, at least through the 14th d of culture. During the culture periods the hepatocytes at high cell density were maintained as confluent monolayers, regardless of the substrate on which they had been cultured. After 14 d of culture, γ-glutamyltranspeptidase activity was highest in cells cultured on C-IV, and lowest in those on FN. DNA synthesis in cultured hepatocytes at a low cell density was highest in cells cultured on FN, with decreasing levels of this parameter in cells cultured on C-IV, C-I, and LN, respectively. These results demonstrate that specific components of the extracellular matrix modulate both differentiated functions and the replication of hepatocytes cultured in serum-free medium. This work was supported in part by grants (CA-07175, CA-09135, CA-22484) from the National Cancer Institute, Bethesda MD. N. Sawada was supported by a Cancer Research Campaign Grant D (U.K.) from the International Union Against Cancer.     

The effect of various substrates on cell attachment and differentiation of 3T3-F442A preadipocytes

The influence of extracellular matrix (Matrigel), collagen, and polylysine substrates on cell attachment and differentiation in 3T3-F442A preadipocytes was investigated. In comparison to an uncoated-polystyrene substrate, a concentrated Matrigel substrate (100 microg/cm2) markedly increased intracellular lipid level by about 30%, whereas a lower density Matrigel (10 microg/cm2) accelerated the differentiation rate but did not increase the amount of lipid 21 days after addition of adipogenic factors. Preadipocytes on the collagen surface differentiated less extensively than cells on the polystyrene. Polylysine did not effectively support attachment for either differentiated or undifferentiated cells. These results suggest that Matrigel provides the most suitable environment for both cell adhesion and differentiation for 3T3-F442A cells. This is in contrast to a previous report that extracellular matrix (from corneal endothelial cells) was detrimental to differentiation of 3T3-F442A cells.     

The alpha 1/beta 1 and alpha 6/beta 1 integrin heterodimers mediate cell attachment to distinct sites on laminin

This study was undertaken to determine the roles of individual alpha/beta 1 integrin heterodimers in promoting cellular interactions with the different attachment-promoting domains of laminin (LN). To do this, antibodies to the integrin beta 1 subunit or to specific integrin alpha subunits were tested for effects on cell attachment to LN, to elastase fragments E1-4 and E1, derived from the short arms and core of LN's cruciform structure, and to fragment E8 derived from the long arm of this structure. The human JAR choriocarcinoma cells used in this study attached to LN and to fragments E1 and E8. Attachment to E1-4 required a much higher substrate coating concentration, suggesting that it is a poor substrate for JAR cell attachment. The ability of cells to attach to different LN domains suggested the presence of more than one LN receptor. These multiple LN receptors were shown to be beta 1 integrin heterodimers because antibodies to the integrin beta 1 subunit inhibited attachment of JAR cells to LN and its three fragments. To identify the individual integrin alpha/beta 1 heterodimers that mediate interactions with these LN domains, mAbs specific for individual beta 1 heterodimers in human cells were used to study JAR cell interactions with LN and its fragments. An anti-alpha 6/beta 1-specific mAb, GoH3, virtually eliminated cell attachment to E8 and partially inhibited attachment to E1 and intact LN. Thus the major alpha 6/beta 1 attachment domain is present in fragment E8. An alpha 1/beta 1-specific mAb (S2G3) strongly inhibited cell attachment to collagen IV and partially inhibited JAR attachment to LN fragment E1. Thus, the alpha 1/beta 1 heterodimer is a dual receptor for collagen IV and LN, interacting with LN at a site in fragment E1. In combination, the anti-alpha 1- and anti-alpha 6-specific antibodies completely inhibited JAR cell attachment to LN and fragment E1. Thus, the alpha 1/beta 1 and alpha 6/beta 1 integrin heterodimers each function as LN receptors and act together to mediate the interactions of human JAR choriocarcinoma cells with LN.     

Inhibition of Endothelial Cell Differentiation on a Glycosylated Reconstituted Basement Membrane Complex

The vascular basement membrane is involved in the regulation of endothelial cell differentiation. The accumulation of advanced glycosylation endproducts (AGEs) has been demonstrated on these basement membranes in patients with diabetes. We examined the effect of AGEs on endothelial cell behavior on reconstituted basement membrane, Matrigel. Human umbilical vein-derived endothelial cells (HUVECs) stopped proliferating and differentiated into capillary-like tube-shaped structures on Matrigel. Laminin antibody partially blocked this process. HUVECs cultured on glycosylated Matrigel, however, proliferated and formed a monolayer without tube formation. The inclusion of aminoguanidine, an inhibitor of AGE formation, during the glycosylation of Matrigel restored HUVEC differentiation. Although the laminin adsorbed onto the plastic culture wells promoted HUVEC attachment and spreading, glycosylated laminin reduced HUVEC attachment by 50% and abolished cellular spreading. These effects were restored by aminoguanidine. HUVEC attachment to glycosylated laminin was further reduced by AGE-modified albumin, poly I, acetylated low-density lipoprotein, or maleylated albumin, ligands for a scavenger receptor. Coating the culture dishes with the laminin peptides RGD, YIGSR, and SIKVAV supported the attachment of HUVECs that was unaffected by glycosylation. Results suggest that AGE accumulation on the basement membranes inhibits endothelial cell differentiation by impairing the normal interactions of endothelial cell receptors with their specific matrix ligands. This process may be involved in diabetic angiopathy.     

Oncostatin M induces cell detachment and enhances the metastatic capacity of T-47D human breast carcinoma cells

Oncostatin M (OSM), an IL-6 family cytokine, has previously been shown to increase migration of several breast cancer cell lines in vitro. Our studies report additional effects of OSM treatment on the human breast carcinoma cell line T-47D. OSM treatment alters T-47D cell morphology from a normal epithelial phenotype to a mesenchymal-like phenotype that is associated with cell detachment from substratum. These effects are also seen with H3922 human breast cancer cells. OSM treatment of T-47D cells for 5-8 days leads to a three-fold increase in cell detachment. OSM-induced detachment of T-47D cells is blocked by the protein kinase inhibitors UO126 and bisindolylmaleimide, indicating a role for MAP kinases and protein kinase C in OSM signaling events that regulate cell detachment. T-47D cells induced to detach by OSM have a reduced capacity to re-adhere to laminin in comparison to other extracellular matrix components. Detached multi-cell aggregates of T-47D cells are viable, whereas detached single cells appear apoptotic. In addition, OSM treatment induces the secretion of the lysosomal proteases cathepsins D and L from T-47D cells, which have been implicated in invasion and metastasis. Importantly, OSM-treated T-47D cells show a 250% increase in invasive capacity as measured by the Matrigel invasion chamber assay. Collectively, these data demonstrate that OSM induces a motile/invasive phenotype in T-47D cells in vitro, and suggest that OSM may enhance metastasis in vivo. Our results suggest that OSM itself may be a valid therapeutic target.     

Improved attachment and spreading in primary cell cultures of the eastern oyster, Crassostrea virginica

At present, establishment of a cell line from bivalve molluscs has been unsuccessful, and in vitro work is limited to primary cell cultures. We sought to improve attachment and spreading of cells of the eastern oyster, Crassostrea virginica, to aid primary cultures and to assist development of a bivalve cell line. Our objectives were to examine the effects of substrate on ventricle cell viability, attachment, and spreading by testing of collagen I, collagen IV, fibronectin, laminin, poly-D-lysine, and two types of uncoated tissue culture plates (Falcon and Corning). Experiments were conducted by incubating cells with the various substrates for 24 h and 5 d. An assay with a tetrazolium compound (MTS) was used to estimate cell numbers based on metabolic activity. Although differences in MTS assay values for substrate effect on cell viability were detected at 24 h and at 5 d (P > 0.0001), these were attributed to variations in metabolic activity due to different levels of attachment and spreading among treatments. Differences among treatments were detected in attachment and spreading at 24 h and 5 d (for all, P > 0.0001). At 24 h, poly-D-lysine induced the highest levels of attachment and spreading; no other factor performed better than the uncoated Falcon substrate, and collagen I performed most poorly. At 5 d, poly-D-lysine and the uncoated Corning substrate induced significantly higher levels of attachment and spreading than did the uncoated Falcons substrate, and collagen I performed most poorly. From these results, poly-D-lysine best promoted cell attachment and spreading. Fibronectin (at 24 h) and laminin (at 5 d) warrant further study. Along with improvements in medium composition, future work should involve screening of other attachment factors and combinations of factors, including those of bivalve origin.     

Laminin-6 is activated by proteolytic processing and regulates cellular adhesion and migration differently from laminin-5

Laminin-6 (LN6) and laminin-5 (LN5), which share the common integrin-binding domain in the laminin alpha3 chain, are thought to cooperatively regulate cellular functions, but the former has poorly been characterized. Human fibrosarcoma HT1080 cells expressing an exogenous alpha3 chain were found to secrete LN6 with the full-length alpha3 chain and a smaller amount of its processed form lacking the carboxyl-terminal G4-5 domain, besides mature LN5 without G4-5 (mat-LN5). We prepared the unprocessed LN6 and mat-LN5, as well as LN6 mutants without G4-5 (LN6DeltaG4-5) or G5 (LN6DeltaG5). These laminins supported attachment of HT1080 cells and human keratinocytes (HaCaT) through integrins alpha(3)beta(1) and/or alpha(6)beta(1). LN6DeltaG4-5, LN6DeltaG5, and mat-LN5 promoted rapid cell spreading, whereas LN6 did hardly. A purified G4-5 fragment of the laminin alpha3 chain supported cell attachment through interaction with heparan sulfate proteoglycans and promoted cell spreading in combination with mat-LN5 or LN6DeltaG4-5. These results imply that the G4-5 domain within the LN6 molecule suppresses cell adhesion, while the released G4-5 promotes it. The presence of G5 rather than the heparin-binding domain G4 was responsible for the impaired cell spreading activity of LN6. However, the unprocessed LN6 promoted cell spreading in the presence of mat-LN5. Unlike mat-LN5, both LN6DeltaG4-5 and LN6 did weakly or did not stimulate cell motility. These findings demonstrate that LN6 and LN5 have distinct biological activities, but they may cooperatively support cell adhesion. The proteolytic processing of the alpha3 chain seems to regulate the physiological functions of LN6.     

Complexity of the tensegrity structure for dynamic energy and force distribution of cytoskeleton during cell spreading

Cytoskeleton plays important roles in intracellular force equilibrium and extracellular force transmission from/to attaching substrate through focal adhesions (FAs). Numerical simulations of intracellular force distribution to describe dynamic cell behaviors are still limited. The tensegrity structure comprises tension-supporting cables and compression-supporting struts that represent the actin filament and microtubule respectively, and has many features consistent with living cells. To simulate the dynamics of intracellular force distribution and total stored energy during cell spreading, the present study employed different complexities of the tensegrity structures by using octahedron tensegrity (OT) and cuboctahedron tensegrity (COT). The spreading was simulated by assigning specific connection nodes for radial displacement and attachment to substrate to form FAs. The traction force on each FA was estimated by summarizing the force carried in sounding cytoskeletal elements. The OT structure consisted of 24 cables and 6 struts and had limitations soon after the beginning of spreading by declining energy stored in struts indicating the abolishment of compression in microtubules. The COT structure, double the amount of cables and struts than the OT structure, provided sufficient spreading area and expressed similar features with documented cell behaviors. The traction force pointed inward on peripheral FAs in the spread out COT structure. The complex structure in COT provided further investigation of various FA number during different spreading stages. Before the middle phase of spreading (half of maximum spreading area), cell attachment with 8 FAs obtained minimized cytoskeletal energy. The maximum number of 12 FAs in the COT structure was required to achieve further spreading. The stored energy in actin filaments increased as cells spread out, while the energy stored in microtubules increased at initial spreading, peaked in middle phase, and then declined as cells reached maximum spreading. The dynamic flows of energy in struts imply that microtubules contribute to structure stabilization.     

Cell adhesion and invasion inhibitory effect of an ovarian cancer targeting peptide selected via phage display in vivo

Organ-specific metastasis is of great importance since most of the cancer deaths are caused by spread of the primary cancer to distant sites. Therefore, targeted anti-metastases therapies are needed to prevent cancer cells from metastasizing to different organs. The phage clone pc3-1 displaying peptide WSGPGVWGASVK selected by phage display had been identified which have high binding efficiency and remarkable cell specificity to SK-OV-3 cells. In the present work, the effects of selected cell-binding phage and cognate peptide on the cell adhesion and invasion of targeted cells were investigated. Results showed that the adhesive ability of SK-OV-3 to extracellular matrix was inhibited by pc3-1 and peptide WSGPGVWGASVK, and pc3-1 blocked SK-OV-3 cells attachment more effective than the cognate peptide. The peptide WSGPGVWGASVK suppressed the cell number of SK-OV-3 that attached to HUVECs monolayer up to 24% and could block the spreading of the attaching cells. Forthermore, the cognate peptide could inhibit the invasion of SK-OV-3 significantly. The number of invaded SK-OV-3 cells and invaded SK-OV-3-activated HUVECs pretreated with peptide WSGPGVWGASVK was decreased by 24.3% and 36.6%, respectively. All these results suggested that peptide WSGPGVWGASVK might possess anti-metastasis against SK-OV-3 cells.     

Reduced viability of human vascular endothelial cells cultured on Matrigel™

Optimal vascular homeostasis requires efficient control of both proliferation and elimination of vascular endothelial cells. Programmed cell death, or apoptosis, is the main mechanism controlling cell elimination, and it is an essential component of vascular formation. Human vascular endothelial cells die in vitro, if prevented from obligatory survival factors like growth factors or attachment and cell spreading, but very little is known about the mechanisms controlling endothelial cell elimination. Signaling from the extracellular matrix affects the behavior and functions of human umbilical vein endothelial cells (HUVECs), and we have recently demonstrated the beneficial effects of plating on the reconstituted extracellular matrix Matrigel™, on the inducible nitric oxide production of freshly isolated HUVECs. In this work we observed that cultured HUVECs formed typical capillary-like structures on Matrigel, but unexpectedly, after 24–48 hours their viability was gradually lost. Viability was measured with an assay based on mitochondrial reduction of reagent XTT. No decrease in viability was seen in freshly isolated HUVECs or in cultured fibroblasts during this time. It is known that cells often turn into apoptosis if they receive conflicting information from their surroundings, and apparently signaling from Matrigel to HUVECs, while at their in vitro proliferating phenotype, resulted in launching of the apoptotic machinery. Thus, proliferating and differentiated phenotypes of endothelial cells seemed to have different sensitivity to signals that induce apoptosis. J. Cell. Physiol. 176:92–98, 1998. © 1998 Wiley-Liss, Inc.