Extracellular matrix composition determines the transcriptional response to epidermal growth factor receptor activation

The RIG-I-like receptor signaling pathway triggered by Staphylococcus aureus promotes breast cancer metastasis

Host microbes are increasingly recognized as key components in various types of cancer, although their exact impact remains unclear. This study investigated the functional significance of Staphylococcus aureus (S. aureus) in breast cancer tumorigenesis and progression. We found that S. aureus invasion resulted in a compromised DNA damage response process, as evidenced by the absence of G1-phase arrest and apoptosis in breast cells in the background of double strand breaks production and the activation of the ataxia-telangiectasia mutated (ATM)-p53 signaling pathway. The high-throughput mRNA sequencing, bioinformatics analysis and pharmacological studies revealed that S. aureus facilitates breast cell metastasis through the innate immune pathway, particularly in cancer cells. During metastasis, S. aureus initially induced the expression of RIG-I-like receptors (RIG-I in normal breast cells, RIG-I and MDA5 in breast cancer cells), which in turn activated NF-κB p65 expression. We further showed that NF-κB p65 activated the CCL5-CCR5 pathway, contributing to breast cell metastasis. Our study provides novel evidence that the innate immune system, triggered by bacterial infection, plays a role in bacterial-driven cancer metastasis.

Crosstalk between CAFs and tumour cells in head and neck cancer

Head and neck squamous cell carcinomas (HNSCCs) are amongst the most aggressive, complex, and heterogeneous malignancies. The standard of care treatments for HNC patients include surgery, radiotherapy, chemotherapy, or their combination. However, around 50% do not benefit while suffering severe toxic side effects, costing the individuals and society. Decades have been spent to improve HNSCC treatment outcomes with only limited success. Much of the research in HNSCC treatment has focused on understanding the genetics of the HNSCC malignant cells, but it has become clear that tumour microenvironment (TME) plays an important role in the progression as well as treatment response in HNSCC. Understanding the crosstalk between cancer cells and TME is crucial for inhibiting progression and treatment resistance. Cancer-associated fibroblasts (CAFs), the predominant component of stroma in HNSCC, serve as the primary source of extra-cellular matrix (ECM) and various pro-tumoral composites in TME. The activation of CAFs in HNSCC is primarily driven by cancer cell-secreted molecules, which in turn induce phenotypic changes, elevated secretive status, and altered ECM production profile. Concurrently, CAFs play a pivotal role in modulating the cell cycle, stemness, epithelial-mesenchymal transition (EMT), and resistance to targeted and chemoradiotherapy in HNSCC cells. This modulation occurs through interactions with secreted molecules or direct contact with the ECM or CAF. Co-culture and 3D models of tumour cells and other TME cell types allows to mimic the HNSCC tumour milieu and enable modulating tumour hypoxia and reprograming cancer stem cells (CSC). This review aims to provide an update on the development of HNSCC tumour models comprising CAFs to obtain better understanding of the interaction between CAFs and tumour cells, and for providing preclinical testing platforms of current and combination with emerging therapeutics.

Leucine-Rich Repeat in Polycystin-1 Suppresses Cystogenesis in a Zebrafish (Danio rerio) Model of Autosomal-Dominant Polycystic Kidney Disease

Mutations of PKD1 coding for polycystin-1 (PC1) account for most cases of autosomal-dominant polycystic kidney disease (ADPKD). The extracellular region of PC1 contains many evolutionarily conserved domains for ligand interactions. Among these are the leucine-rich repeats (LRRs) in the far N-terminus of PC1. Using zebrafish (Danio rerio) as an in vivo model system, we explored the role of LRRs in the function of PC1. Zebrafish expresses two human PKD1 paralogs, pkd1a and pkd1b. Knockdown of both genes in zebrafish by morpholino antisense oligonucleotides produced phenotypes of dorsal-axis curvature and pronephric cyst formation. We found that overexpression of LRRs suppressed both phenotypes in pkd1-morphant zebrafish. Purified recombinant LRR domain inhibited proliferation of HEK cells in culture and interacted with the heterotrimeric basement membrane protein laminin-511 (α5β1γ1) in vitro. Mutations of amino acid residues in LRRs structurally predicted to bind laminin-511 disrupted LRR-laminin interaction in vitro and neutralized the ability of LRRs to inhibit cell proliferation and cystogenesis. Our data support the hypothesis that the extracellular region of PC1 plays a role in modulating PC1 interaction with the extracellular matrix and contributes to cystogenesis of PC1 deficiency.

Lysophosphatidic acid suppresses apoptosis of high-grade serous ovarian cancer cells by inducing autophagy activity and promotes cell-cycle progression via EGFR-PI3K/Aurora-AThr288-geminin dual signaling pathways

Lysophosphatidic acid (LPA) and geminin are overexpressed in ovarian cancer, and increasing evidence supports their contribution to ovarian tumor development. Here, we reveal that geminin depletion induces autophagy suppression and enhances reactive oxygen species (ROS) production and apoptosis of high-grade serous ovarian cancer (HGSOC) cells. Bioinformatics analysis and pharmacological inhibition studies confirm that LPA activates geminin expression in the early S phase in HGSOC cells via the LPAR1/3/MMPs/EGFR/PI3K/mTOR pathway. Furthermore, LPA phosphorylates Aurora-A kinase on Thr288 through EGFR transactivation, and this event potentiates additional geminin stabilization. In turn, overexpressed and stabilized geminin regulates DNA replication, cell-cycle progression, and cell proliferation of HGSOC cells. Our data provide potential targets for enhancing the clinical benefit of HGSOC precision medicine.

Pancreatic Adenocarcinoma Therapeutics Targeting RTK and TGF Beta Receptor

Despite the improved overall survival rates in most cancers, pancreatic cancer remains one of the deadliest cancers in this decade. The rigid microenvironment, which majorly comprises cancer-associated fibroblasts (CAFs), plays an important role in the obstruction of pancreatic cancer therapy. To overcome this predicament, the signaling of receptor tyrosine kinases (RTKs) and TGF beta receptor (TGFβR) in both pancreatic cancer cell and supporting CAF should be considered as the therapeutic target. The activation of receptors has been reported to be aberrant to cell cycle regulation, and signal transduction pathways, such as growth-factor induced proliferation, and can also influence the apoptotic sensitivity of tumor cells. In this article, the regulation of RTKs/TGFβR between pancreatic ductal adenocarcinoma (PDAC) and CAFs, as well as the RTKs/TGFβR inhibitor-based clinical trials on pancreatic cancer are reviewed.

Source and Impact of the EGF Family of Ligands on Intestinal Stem Cells

Epidermal Growth Factor (EGF) has long been known for its role in promoting proliferation of intestinal epithelial cells. EGF is produced by epithelial niche cells at the base of crypts in vivo and is routinely added to the culture medium to support the growth of intestinal organoids ex vivo. The recent identification of diverse stromal cell populations that reside underneath intestinal crypts has enabled the characterization of key growth factor cues supplied by these cells. The nature of these signals and how they are delivered to drive intestinal epithelial development, daily homeostasis and tissue regeneration following injury are being investigated. It is clear that aside from EGF, other ligands of the family, including Neuregulin 1 (NRG1), have distinct roles in supporting the function of intestinal stem cells through the ErbB pathway.

Mimicking and surpassing the xenograft model with cancer-on-chip technology

Organs-on-chips are in vitro models in which human tissues are cultured in microfluidic compartments with a controlled, dynamic micro-environment. Specific organs-on-chips are being developed to mimic human tumors, but the validation of such 'cancer-on-chip' models for use in drug development is hampered by the complexity and variability of human tumors. An important step towards validation of cancer-on-chip technology could be to first mimic cancer xenograft models, which share multiple characteristics with human cancers but are significantly less complex. Here we review the relevant biological characteristics of a xenograft tumor and show that organ-on-chip technology is capable of mimicking many of these aspects. Actual comparisons between on-chip tumor growth and xenografts are promising but also demonstrate that further development and empirical validation is still needed. Validation of cancer-on-chip models to xenografts would not only represent an important milestone towards acceptance of cancer-on-chip technology, but could also improve drug discovery, personalized cancer medicine, and reduce animal testing.

Interplay between Cell-Surface Receptors and Extracellular Matrix in Skin

Skin consists of the epidermis and dermis, which are connected by a specialized basement membrane-the epidermal basement membrane. Both the epidermal basement membrane and the underlying interstitial extracellular matrix (ECM) created by dermal fibroblasts contain distinct network-forming macromolecules. These matrices play various roles in order to maintain skin homeostasis and integrity. Within this complex interplay of cells and matrices, cell surface receptors play essential roles not only for inside-out and outside-in signaling, but also for establishing mechanical and biochemical properties of skin. Already minor modulations of this multifactorial cross-talk can lead to severe and systemic diseases. In this review, major epidermal and dermal cell surface receptors will be addressed with respect to their interactions with matrix components as well as their roles in fibrotic, inflammatory or tumorigenic skin diseases.

Regulation of heterogeneous cancer-associated fibroblasts: the molecular pathology of activated signaling pathways

Accumulating evidence indicates that intratumoral heterogeneity contributes to the development of resistance to anticancer therapeutics. Fibroblasts, which are components of the paraneoplastic stroma, play a crucial role in the wound-healing process. Activated fibroblasts accumulate in the wound and are involved in many aspects of the tissue remodeling cascade that initiates the repair process and prevents further tissue damage. The pathophysiological roles of cancer-associated fibroblasts (CAFs) in the heterogeneous tumor microenvironment have attracted increasing interest. CAFs play crucial roles in tumor progression and the response to chemotherapy. Several cytokines and chemokines are involved in the conversion of normal fibroblasts into CAFs, and some of these form a feedback loop between cancer cells and CAFs. In addition, the physical force between tumor cells and CAFs promotes cooperative invasion or co-migration of both types of cells. Pro-inflammatory cytokines, such as leukemia inhibitory factor (LIF) and interleukin-6 (IL-6), are secreted by both cancer cells and CAFs, and mediate the epigenetic modification of CAFs. This enhances the pro-tumorigenic function of CAFs mediated by promoting actomyosin contractility and extracellular matrix remodeling to form the tracks used for collective cancer cell migration. The concept of intra-tumoral CAF heterogeneity refers to the presence of inflammatory CAFs with low levels of α-smooth muscle actin (α-SMA) and high levels of IL-6 expression, which are in striking contrast to transforming growth factor-β (TGF-β)-dependent myofibroblastic CAFs with high α-SMA expression levels. CAF populations that suppress tumor growth and progression through stroma-specific Hedgehog (Hh) activation have been detected in different murine tumor models including those of the bladder, colon, and pancreas. A new therapeutic strategy targeting CAFs is the "stromal switch," in which tumor-promoting CAFs are changed into tumor-retarding CAFs with attenuated stromal stiffness. Several molecular mechanisms that can be exploited to design personalized anticancer therapies targeting CAFs remain to be elucidated. Strategies aimed at targeting the tumor stroma as well as tumor cells themselves have attracted academic attention for their application in precision medicine. This novel review discusses the role of the activation of EGFR, Wnt/β-catenin, Hippo, TGF-β, and JAK/STAT cascades in CAFs in relation to the chemoresistance and invasive/metastatic behavior of cancer cells. For instance, although activated EGFR signaling contributes to collective cell migration in cooperation with CAFs, an activated Hippo pathway is responsible for stromal stiffness resulting in the collapse of neoplastic blood vessels. Therefore, identifying the signaling pathways that are activated under specific conditions is crucial for precision medicine.

A systems perspective of heterocellular signaling

Signal exchange between different cell types is essential for development and function of multicellular organisms, and its dysregulation is causal in many diseases. Unfortunately, most cell-signaling work has employed single cell types grown under conditions unrelated to their native context. Recent technical developments have started to provide the tools needed to follow signaling between multiple cell types, but gaps in the information they provide have limited their usefulness in building realistic models of heterocellular signaling. Currently, only targeted assays have the necessary sensitivity, selectivity, and spatial resolution to usefully probe heterocellular signaling processes, but these are best used to test specific, mechanistic models. Decades of systems biology research with monocultures has provided a solid foundation for building models of heterocellular signaling, but current models lack a realistic description of regulated proteolysis and the feedback processes triggered within and between cells. Identification and understanding of key regulatory processes in the extracellular environment and of recursive signaling patterns between cells will be essential to building predictive models of heterocellular systems.

A next generation sequencing based approach to identify extracellular vesicle mediated mRNA transfers between cells

Background

Exosomes and other extracellular vesicles (EVs) have emerged as an important mechanism of cell-to-cell communication. However, previous studies either did not fully resolve what genetic materials were shuttled by exosomes or only focused on a specific set of miRNAs and mRNAs. A more systematic method is required to identify the genetic materials that are potentially transferred during cell-to-cell communication through EVs in an unbiased manner.

Results

In this work, we present a novel next generation of sequencing (NGS) based approach to identify EV mediated mRNA exchanges between co-cultured adipocyte and macrophage cells. We performed molecular and genomic profiling and jointly considered data from RNA sequencing (RNA-seq) and genotyping to track the “sequence varying mRNAs” transferred between cells. We identified 8 mRNAs being transferred from macrophages to adipocytes and 21 mRNAs being transferred in the opposite direction. These mRNAs represented biological functions including extracellular matrix, cell adhesion, glycoprotein, and signal peptides.

Conclusions

Our study sheds new light on EV mediated RNA communications between adipocyte and macrophage cells, which may play a significant role in developing insulin resistance in diabetic patients. This work establishes a new method that is applicable to examining genetic material exchanges in many cellular systems and has the potential to be extended to in vivo studies as well.

Electronic supplementary material

The online version of this article (10.1186/s12864-017-4359-1) contains supplementary material, which is available to authorized users.

KCa1.1 channels regulate β1-integrin function and cell adhesion in rheumatoid arthritis fibroblast-like synoviocytes

Large-conductance calcium-activated potassium channel (KCa1.1; BK, Slo1, MaxiK, KCNMA1) is the predominant potassium channel expressed at the plasma membrane of rheumatoid arthritis fibroblast-like synoviocytes (RA-FLSs) isolated from the synovium of patients with RA. It is a critical regulator of RA-FLS migration and invasion and therefore represents an attractive target for the therapy of RA. However, the molecular mechanisms by which KCa1.1 regulates RA-FLS invasiveness have remained largely unknown. Here, we demonstrate that KCa1.1 regulates RA-FLS adhesion through controlling the plasma membrane expression and activation of β₁ integrins, but not α₄, α₅, or α₆ integrins. Blocking KCa1.1 disturbs calcium homeostasis, leading to the sustained phosphorylation of Akt and the recruitment of talin to β₁ integrins. Interestingly, the pore-forming α subunit of KCa1.1 coimmunoprecipitates with β₁ integrins, suggesting that this physical association underlies the functional interaction between these molecules. Together, these data outline a new signaling mechanism by which KCa1.1 regulates β₁-integrin function and therefore invasiveness of RA-FLSs.-Tanner, M. R., Pennington, M. W., Laragione, T., Gulko, P. S., Beeton, C. KCa1.1 channels regulate β₁-integrin function and cell adhesion in rheumatoid arthritis fibroblast-like synoviocytes.

The growth determinants and transport properties of tunneling nanotube networks between B lymphocytes

Tunneling nanotubes (TNTs) are long intercellular connecting structures providing a special transport route between two neighboring cells. To date TNTs have been reported in different cell types including immune cells such as T-, NK, dendritic cells, or macrophages. Here we report that mature, but not immature, B cells spontaneously form extensive TNT networks under conditions resembling the physiological environment. Live-cell fluorescence, structured illumination, and atomic force microscopic imaging provide new insights into the structure and dynamics of B cell TNTs. Importantly, the selective interaction of cell surface integrins with fibronectin or laminin extracellular matrix proteins proved to be essential for initiating TNT growth in B cells. These TNTs display diversity in length and thickness and contain not only F-actin, but their majority also contain microtubules, which were found, however, not essential for TNT formation. Furthermore, we demonstrate that Ca2+-dependent cortical actin dynamics exert a fundamental control over TNT growth-retraction equilibrium, suggesting that actin filaments form the TNT skeleton. Non-muscle myosin 2 motor activity was shown to provide a negative control limiting the uncontrolled outgrowth of membranous protrusions. Moreover, we also show that spontaneous growth of TNTs is either reduced or increased by B cell receptor- or LPS-mediated activation signals, respectively, thus supporting the critical role of cytoplasmic Ca2+ in regulation of TNT formation. Finally, we observed transport of various GM1/GM3+ vesicles, lysosomes, and mitochondria inside TNTs, as well as intercellular exchange of MHC-II and B7-2 (CD86) molecules which may represent novel pathways of intercellular communication and immunoregulation.

Elucidation of the CHO Super-Ome (CHO-SO) by Proteoinformatics

Chinese hamster ovary (CHO) cells are the preferred host cell line for manufacturing a variety of complex biotherapeutic drugs including monoclonal antibodies. We performed a proteomics and bioinformatics analysis on the spent medium from adherent CHO cells. Supernatant from CHO-K1 culture was collected and subjected to in-solution digestion followed by LC/LC-MS/MS analysis, which allowed the identification of 3281 different host cell proteins (HCPs). To functionally categorize them, we applied multiple bioinformatics tools to the proteins identified in our study including SignalP, TargetP, SecretomeP, TMHMM, WoLF PSORT, and Phobius. This analysis provided information on the presence of signal peptides, transmembrane domains, and cellular localization and showed that both secreted and intracellular proteins were constituents of the supernatant. Identified proteins were shown to be localized to the secretory pathway including ones playing roles in cell growth, proliferation, and folding as well as those involved in protein degradation and removal. After combining proteins predicted to be secreted or having a signal peptide, we identified 1015 proteins, which we termed as CHO supernatant-ome (CHO-SO), or superome. As a part of this effort, we created a publically accessible web-based tool called GO-CHO to functionally categorize proteins found in CHO-SO and identify enriched molecular functions, biological processes, and cellular components. We also used a tool to evaluate the immunogenicity potential of high-abundance HCPs. Among enriched functions were catalytic activity and structural constituents of the cytoskeleton. Various transport related biological processes, such as vesicle mediated transport, were found to be highly enriched. Extracellular space and vesicular exosome associated proteins were found to be the most enriched cellular components. The superome also contained proteins secreted from both classical and nonclassical secretory pathways. The work and database described in our study will enable the CHO community to rapidly identify high-abundance HCPs in their cultures and therefore help assess process and purification methods used in the production of biologic drugs.

Nanotopology potentiates growth hormone signalling and osteogenesis of mesenchymal stem cells

Custom engineered materials can influence the differentiation of human mesenchymal stem cells (MSCs) towards osteoblasts, chondrocytes and adipocytes, through the control of chemistry, stiffness and nanoscale topography. Here we demonstrate that polycaprolactone growth surfaces engineered with disordered (but controlled) 120 nm diameter dots (NSQ50), but not flat surfaces, promote osteogenic conversion of MSCs in the absence of other osteogenic stimuli. Differentiating MSCs on NSQ50 were found to express growth hormone receptors (GH) and stimulation with recombinant human GH (rhGH) further enhanced NSQ50-driven osteogenic conversion of MSCs. This increased osteogenesis coincided with an enhanced ability of GH to activate ERK MAP kinase on NSQ50, but not on flat topology. The importance of ERK for MSC differentiation was demonstrated by using the inhibitor of ERK activation, U0126, which completely suppressed osteogenesis of GH-stimulated MSCs on NSQ50. The ability of GH to activate ERK in MSCs may therefore be a central control mechanism underlying bone development and growth.

Cetuximab attenuates its cytotoxic and radiosensitizing potential by inducing fibronectin biosynthesis

Inherent and acquired resistance to targeted therapeutics continues to emerge as a major clinical obstacle. For example, resistance to EGF receptor targeting occurs commonly, more so than was expected, on the basis of preclinical work. Given emerging evidence that cancer cell-substrate interactions are important determinants of therapeutic sensitivity, we examined the impact of cell-fibronectin interactions on the efficacy of the EGF receptor antibody cetuximab, which is used widely for lung cancer treatment. Our results revealed the potential for cell-fibronectin interactions to induce radioresistance of human non-small cell lung cancer cells. Cell adhesion to fibronectin enhanced tumor cell radioresistance and attenuated the cytotoxic and radiosensitizing effects of cetuximab. Both in vitro and in vivo, we found that cetuximab treatment led to a remarkable induction of fibronectin biosynthesis. Mechanistic analyses revealed the induction was mediated by a p38-MAPK-ATF2 signaling pathway and that RNAi-mediated inhibition of fibronectin could elevate the cytotoxic and radiosensitizing potential of cetuximab. Taken together, our findings show how cell adhesion blunts cetuximab, which, by inducing fibronectin, generates a self-attenuating mechanism of drug resistance.

The molecular composition of the metastatic niche

In cancer, the microenvironment plays an important role of supporting the outgrowth of new tumors in distant organs i.e. the formation of metastasis. The interplay between cancer cells and the host stroma leads to generation of an active microenvironment termed a metastatic niche that effectively supports cancer progression and outgrowth of metastasis. The generation and development of the niche is intricately linked to cancer progression. Metastatic niches are highly dynamic interactions that can be forged by diverse mechanisms and continue to develop as the cancer progresses. The composition of the niche is increasingly being characterized and new niche components are being identified. The extracellular matrix (ECM), secreted enzymes, growth factors, cytokines and other molecules that carry information to cancer cells are essential parts of the metastatic niche. The sources of this molecular milieu are multiple cell types - local or recruited to the site of metastasis - and in some cases the cancer cells themselves. To understand metastatic progression it is essential to dissect the niche composition and identify the sources of niche components. With future analyses of the metastatic niche, significant opportunities can arise to identify novel targets for cancer therapy. Targeting the metastatic niche may be essential to treat and inhibit the progression of metastasis.

Dynamic regulation of the structure and functions of integrin adhesions

Integrin-mediated cell adhesions to the extracellular matrix (ECM) contribute to tissue morphogenesis and coherence and provide cells with vital environmental cues. These apparently static structures display remarkable plasticity and dynamic properties: they exist in multiple, interconvertible forms that are constantly remodeled in response to changes in ECM properties, cytoskeletal organization, cell migration, and signaling processes. Thus, integrin-mediated environmental sensing enables cells to adapt to chemical and physical properties of the surrounding matrix by modulating their proliferation, differentiation, and survival. This intriguing interplay between the apparently robust structure of matrix adhesions and their highly dynamic properties is the focus of this article.

Tetraspanin CD151 stimulates adhesion-dependent activation of Ras, Rac, and Cdc42 by facilitating molecular association between β1 integrins and small GTPases

Tetraspanin CD151 associates with laminin-binding α(3)β(1)/α(6)β(1) integrins in epithelial cells and regulates adhesion-dependent signaling events. We found here that CD151 plays a role in recruiting Ras, Rac1, and Cdc42, but not Rho, to the cell membrane region, leading to the formation of α(3)β(1)/α(6)β(1) integrin-CD151-GTPases complexes. Furthermore, cell adhesion to laminin enhanced CD151 association with β(1) integrin and, thereby, increased complex formation between the β(1) family of integrins and small GTPases, Ras, Rac1, and Cdc42. Adhesion receptor complex-associated small GTPases were activated by CD151-β(1) integrin complex-stimulating adhesion events, such as α(3)β(1)/α(6)β(1) integrin-activating cell-to-laminin adhesion and homophilic CD151 interaction-generating cell-to-cell adhesion. Additionally, FAK and Src appeared to participate in this adhesion-dependent activation of small GTPases. However, engagement of laminin-binding integrins in CD151-deficient cells or CD151-specific siRNA-transfected cells did not activate these GTPases to the level of cells expressing CD151. Small GTPases activated by engagement of CD151-β(1) integrin complexes contributed to CD151-induced cell motility and MMP-9 expression in human melanoma cells. Importantly, among the four tetraspanin proteins that associate with β(1) integrin, only CD151 exhibited the ability to facilitate complex formation between the β(1) family of integrins and small GTPases and stimulate β(1) integrin-dependent activation of small GTPases. These results suggest that CD151 links α(3)β(1)/α(6)β(1) integrins to Ras, Rac1, and Cdc42 by promoting the formation of multimolecular complexes in the membrane, which leads to the up-regulation of adhesion-dependent small GTPase activation.

Cell contact-dependent functional selectivity of β2-adrenergic receptor ligands in stimulating cAMP accumulation and extracellular signal-regulated kinase phosphorylation

Activation of β(2)-adrenegic receptor (β(2)-AR) leads to an increase in intracellular cAMP and activation of ERK. These two signals are activated by the interaction of the receptor with different transducer partners. We showed that the intrinsic activities of β(2)-AR ligands for stimulating cAMP production and ERK phosphorylation responses in HEK-293 cells were not correlated. The lack of correlation resulted mainly from the discrepancy between the intrinsic activities of two groups of ligands for these two responses: The first group consisted of clenbuterol, cimaterol, procaterol, and terbutaline which acted as full agonists for cAMP production but displayed very weak effect on ERK phosphorylation. The second group comprised adrenaline and noradrenaline which displayed higher intrinsic activity for the ERK phosphorylation than for the cAMP response. Thus, both groups behaved as functionally selective ligands. The functional selectivity of the first group was observable only in adherent cells when confluence was approximately 100%. When cell-cell contact was minimized either by decreasing the density of the adherent cells or by bringing the cells into suspension, the first group of ligands gained the ability to stimulate ERK phosphorylation without a change in their effect on cAMP production. In contrast, selectivity of the second group was independent of the adherence state of the cells. Our results show that the inherent "bias" of ligands in coupling a G protein-coupled receptor to different transducers may not always be revealed as functional selectivity when there is a "cross-talk" between the signaling pathways activated by the same receptor.

Cooperation between integrins and growth factor receptors in signaling and endocytosis

All multicellular animals express receptors for growth factors (GFs) and extracellular matrix (ECM) molecules. Integrin-type ECM receptors anchor cells to their surroundings and concomitantly activate intracellular signal transduction pathways. The same signaling mechanisms are regulated by GF receptors (GFRs). Recently, intensive research efforts have revealed novel mechanisms describing how the two receptor systems collaborate at many different levels. Integrins can directly bind to GFs and promote their activation. Adhesion receptors also organize signaling platforms and assist GFRs or even activate them via ligand-independent mechanisms. Furthermore, integrins can orchestrate endocytosis and recycling of GFRs. Here, we review the present knowledge about the interplay between integrins and GFRs and discuss recent ideas of how this collaboration may explain some previous controversies in integrin research.

Serum starvation: caveat emptor

Serum starvation is one of the most frequently performed procedures in molecular biology and there are literally thousands of research papers reporting its use. In fact, this method has become so ingrained in certain areas of research that reports often simply state that cells were serum starved without providing any factual details as to how the procedure was carried out. Even so, we quite obviously lack unequivocal terminology, standard protocols, and perhaps most surprisingly, a common conceptual basis when performing serum starvation. Such inconsistencies not only hinder interstudy comparability but can lead to opposing and inconsistent experimental results. Although it is frequently assumed that serum starvation reduces basal activity of cells, available experimental data do not entirely support this notion. To address this important issue, we studied primary human myotubes, rat L6 myotubes and human embryonic kidney (HEK)293 cells under different serum starvation conditions and followed time-dependent changes in important signaling pathways such as the extracellular signal-regulated kinase 1/2, the AMP-activated protein kinase, and the mammalian target of rapamycin. Serum starvation induced a swift and dynamic response, which displayed obvious qualitative and quantitative differences across different cell types and experimental conditions despite certain unifying features. There was no uniform reduction in basal signaling activity. Serum starvation clearly represents a major event that triggers a plethora of divergent responses and has therefore great potential to interfere with the experimental results and affect subsequent conclusions.

Clinical evidence to demonstrate that simultaneous growth of epithelial and fibroblast cells is essential for deep wound healing

OBJECTIVE

The aim of this study was to evaluate the chronic wound healing properties of tannin rich plant extracts.

METHODS

The cell growth stimulating potential of 128 procyanidin rich plant extracts was evaluated in in vitro cell culture models. For clinical trial, a 3% solution of two plant extracts having synergistic effect on cell growth was prepared in glycerol and honey. Placebo test product contained only glycerol and honey. 93 adult patients with one or more lower extremity deep wounds were divided at randomly in two groups. 41 patients in the placebo (AS-22) and 52 in the active treatment (AS-21) groups having respectively 49 and 69 wounds of a mean surface area of 56.70 and 52.03 cm(2), and volume of 57.22 and 52.15 cm(3), were treated by applying the test products topically for a period of 6-weeks.

RESULTS

A statistically significant difference was observed between the placebo and the AS-21 treated groups with respect to reduction in the wound surface area (33.37 vs 97.87%) and wound volume (29.45 vs 94.17%) after 6-weeks of treatment. Mean wound humidity and pain scores were also reduced.

CONCLUSION

Tannin rich plant extracts are highly interesting for the treatment of chronic wounds.

Characterization of endogenous calcium responses in neuronal cell lines

An increasing number of putative therapeutic targets have been identified in recent years for the treatment of neuronal pathophysiologies including pain, epilepsy, stroke and schizophrenia. Many of these targets signal through calcium (Ca(2+)), either by directly facilitating Ca(2+) influx through an ion channel, or through activation of G proteins that couple to intracellular Ca(2+) stores or voltage-gated Ca(2+) channels. Immortalized neuronal cell lines are widely used models to study neuropharmacology. However, systematic pharmacological characterization of the receptors and ion channels expressed in these cell lines is lacking. In this study, we systematically assessed endogenous Ca(2+) signaling in response to addition of agonists at potential therapeutic targets in a range of cell lines of neuronal origin (ND7/23, SH-SY5Y, 50B11, F11 and Neuro2A cells) as well as HEK293 cells, a cell line commonly used for over-expression of receptors and ion channels. This study revealed a remarkable diversity of endogenous Ca(2+) responses in these cell lines, with one or more cell lines responding to addition of trypsin, bradykinin, ATP, nicotine, acetylcholine, histamine and neurotensin. Subtype specificity of these responses was inferred from agonist potency and the effect of receptor subtype specific antagonist. Surprisingly, HEK293 and SH-SY5Y cells responded to the largest number of agonists with potential roles in neuronal signaling. These findings have implications for the heterologous expression of neuronal receptors and ion channels in these cell lines, and highlight the potential of neuron-derived cell lines for the study of a range of endogenously expressed receptors and ion channels that signal through Ca(2+).

Analysis of focal adhesions and cytoskeleton by custom microarray

Focal adhesions and the cell cytoskeleton (intermediate filaments, microfilaments, microtubules) are involved in mechanotransduction-both direct (transduction of mechanical forces to the nucleus) and indirect (transduction of chemical signaling cascades to the nucleus). Thus, observation of changes in focal adhesion and cytoskeletal organization can be invaluable in research such as drug treatments and medical material testing in vitro. Here we describe how to stain human fibroblasts for vinculin (located to focal adhesions), actin (microfilaments), tubulin (microtubules), and vimentin (intermediate filaments) and how to perform custom microarray experiments. Comparative analysis of the immunofluorescence and array data should allow the researcher to build up a global picture of changes to both direct and indirect mechanotransduction through the cytoskeleton from focal adhesions.

Transcriptional targets of hepatocyte growth factor signaling and Ki-ras oncogene activation in colorectal cancer

Both Ki-ras mutation and hepatocyte growth factor (HGF) receptor Met overexpression occur at high frequency in colon cancer. This study investigates the transcriptional changes induced by Ki-ras oncogene and HGF/Met signaling activation in colon cancer cell lines in vitro and in vivo. The model system used in these studies included the DLD-1 colon cancer cell line with a mutated Ki-ras allele, and the DKO-4 cell line generated from DLD-1, with its mutant Ki-ras allele inactivated by targeted disruption. These cell lines were transduced with cDNAs of full-length Met receptor. Microarray transcriptional profiling was conducted on cell lines stimulated with HGF, as well as on tumor xenograft tissues. Overlapping genes between in vitro and in vivo microarray data sets were selected as a subset of HGF/Met and Ki-ras oncogene-regulated targets. Using the Online Predicted Human Interaction Database, novel HGF/Met and Ki-ras regulated proteins with putative functional linkage were identified. Novel proteins identified included histone acetyltransferase 1, phosphoribosyl pyrophosphate synthetase 2, chaperonin containing TCP1, subunit 8, CSE1 chromosome segregation 1-like (yeast)/cellular apoptosis susceptibility (mammals), CCR4-NOT transcription complex, subunit 8, and cyclin H. Transcript levels for these Met-signaling targets were correlated with Met expression levels, and were significantly elevated in both primary and metastatic human colorectal cancer samples compared to normal colorectal mucosa. These genes represent novel Met and/or Ki-ras transcriptionally coregulated genes with a high degree of validation in human colorectal cancers.

Inhibition of the epidermal growth factor receptor increases expression of genes that stimulate inflammation, apoptosis, and cell attachment

The epidermal growth factor receptor (EGFR) is overexpressed in several types of human cancer, and inhibition of EGFR function is a promising strategy for cancer therapy. We used cDNA microarrays to examine alterations in gene expression after treatment of carcinoma cells with PD153035, a specific and reversible inhibitor of EGFR function. When human cervical carcinoma cells were grown on a collagen substrate in three-dimensional organotypic culture, untreated cells expressed high levels of EGFR RNA and invaded the underlying collagen. Blocking EGFR function decreased DNA synthesis and inhibited invasion in a dose-dependent manner. Microarray analyses identified 312 genes that were significantly increased or decreased in expression after EGFR inhibition. Many could be classified into one of four functional groups including genes that (a) stimulate inflammation and innate immunity, (b) promote cell attachment, (c) enhance apoptosis, and (d) inhibit cell cycle progression. PD153035 induced a dose-dependent activation of nuclear factor kappaB, a transcription factor that stimulates proinflammatory gene expression. Our results identify alterations in gene expression caused by EGFR inhibition and show that this response varies significantly in different cell lines.

Differentiation of a mouse submandibular gland-derived cell line (SCA) grown on matrigel

SCA-9 cell line was developed from an induced tumor of mouse submandibular gland. We have studied some of the phenotypic characteristics of SCA cells cultured on different matrices. On plastic surface, the cells grow as a monolayer; on matrigel, they form branching structures and tubes, a phenomenon termed branching morphogenesis. EGF and HGF promoted cellular growth and branching morphogenesis which was inhibited by anti-EGF antibodies. We have performed RT-PCR and real-time quantitative RT-PCR of cells grown on plastic surface or on matrigel. Grown on plastic, the cells express EGF and renin 2, but no or only trace amounts of NGF. Growth on matrigel for 24 h resulted in a transient 21-fold increase in EGF mRNA and a 3371-fold increase in renin 2 mRNA. There was no change in NGF mRNA level. SCA-9 cells express mRNAs for receptors for the EGF family of ligands. On plastic, mainly ErbB1 and ErbB2 are expressed. Culture on matrigel resulted in 11-fold increase in mRNA levels for ErbB1 and ErbB2, and a 221-fold and 85-fold increase in the mRNA levels for ErbB3 and ErbB4, respectively. Small interfering RNAs siErbB3 and siErbB4 inhibited the growth of the cells grown on plastic or matrigel. Significant growth inhibition was seen also with siErbB1+siErbB3 and siErbB2+siErbB3. siErbB1 and siErbB2 also inhibited branching morphogenesis. Since SCA cells express EGF and receptors for EGF, EGF acts an autocrine regulator in promoting growth and branching morphogenesis. We conclude that SCA cells provide a useful model to analyze the mechanism of branching morphogenesis and the role of matrix in regulating expression of phenotypic characteristics of cultured cells.

Identification of growth factor-regulated proteins using 2D electrophoresis and mass spectrometry

Proteomic technology has recently emerged as a powerful tool for detecting both qualitative and quantitative changes of proteins that occur upon activation of complex signaling pathways. In the present study, comparison of the protein profile of platelet-derived growth factor (PDGF), epidermal growth factor (EGF) and nerve growth factor (NGF)-stimulated and unstimulated cells with two-dimensional electrophoresis followed by mass spectrometric analysis led to the identification of a number of proteins, several of which had not been previously shown to be regulated by receptor-tyrosine kinases. Using subcellular fractionation, our approach was able to identify not only changes due to altered gene transcription, but also due to intracellular protein translocation or modification. One of the proteins that was identified among other PDGF-regulated molecules was prohibitin, a potential tumour suppressor previously implicated in cell cycle regulation and protection of mitochondrial proteins from degradation. Further analysis confirmed that mitochondria-associated prohibitin translocates to an insoluble perinuclear compartment. This study demonstrates the utility of proteomic strategies in identifying potential growth factor-regulated effectors.

Microarray profiles of human basal cell carcinoma: Insights into tumor growth and behavior

PURPOSE

Basal cell carcinoma (BCC) is the most common human neoplasm. Much interest lies in determining the genetic basis of BCC to explain the unique locally invasive phenotype and infrequent metastatic behavior of these skin tumors.

OBJECTIVE

We sought to examine a gene expression profile for BCC to elucidate new molecules responsible for its unique growth characteristics.

METHODS

We analyzed gene expression patterns of 50 BCC tumors using spotted cDNA microarrays of 1718 characterized human genes related to cancer and immunity. This is the largest and most comprehensive gene expression study ever performed for BCC. Nodular and sclerosing histological subtypes of BCC were examined and compared to normal control skin. After statistical filtering, 374 significantly dysregulated genes were sorted by hierarchical clustering to determine trends of gene expression and similarities between patient gene expression profiles.

RESULTS

A total of 165 upregulated genes and 115 downregulated genes were identified. These covered a range of categories, including extracellular matrix, cell junctions, motility, metastasis, oncogenes, tumor suppressors, DNA repair, cell cycle, immune regulation and angiogenesis. Clusters of genes were either commonly dysregulated across the 50 patient sample, or selectively affected in subsets of tumors. Histological subtypes were not distinguishable by hierarchical clustering. Many of the genes elucidated, including collagen type IV subunits and other novel candidates, possess functions related to extracellular matrix remodeling and metastasis.

CONCLUSION

These results suggest a gene profile which may explain the invasive growth yet rarely metastatic behavior of BCC. The genes identified may also be potential targets for therapeutics aimed at further controlling invasiveness and local destruction of BCC.

Proliferation of cerebellar neurons induced by astrocytes treated with thyroid hormone is mediated by a cooperation between cell contact and soluble factors and involves the epidermal growth factor-protein kinase a pathway

Cerebellar development is fully dependent on thyroid hormone (T3) levels. We have previously demonstrated a glia-mediated effect of T3 on cerebellar neurons. We have reported that cerebellar astrocytes treated with thyroid hormone secrete epidermal growth factor (EGF), which directly induces neuronal proliferation and, indirectly, by increasing synthesis of extracellular matrix proteins, induces neurite outgrowth in vitro. Here, by using a neuron-astrocyte coculture model, we investigated the involvement of cell contact on neuronal proliferation. Culturing of cerebellar neurons on T3-treated astrocyte carpets or conditioned medium derived from them (T3CM) yielded similar results, revealed by a 60% increase in cell population. However, the absolute number of neurons in coculture assays was greatly enhanced in comparison with that in CM assays (3.5-4-fold). Bromodeoxyuridine (BrdU) incorporation assays revealed that such an increase was due mainly to proliferation of precursors cells. BrdU incorporation was three times higher in cell carpet (31%) than in CM (13%). Treatment of astrocytes by T3 increased neuronal proliferation either by T3CM (2.5 times) or by contact with T3-treated astrocytes (1.5 times). Neuronal death was not affected by T3 treatment of astrocytes as revealed by either trypan blue viability assays or active caspase-3 labeling. Treatment of astrocytes by EGF mimicked T3 effects on neuronal proliferation. Addition of the EGF receptor tyrosine kinase inhibitor genistein and the protein kinase A (PKA) inhibitor KT5720 to cocultutres and T3CM completely reversed neuronal proliferation. Our results implicate EGF and the PKA pathway in the proliferation induced by T3-treated astrocytes. Furthermore, the fact that cocultures potentiate the effect of T3 on neuronal proliferation suggests that neuron-astrocyte contact may cooperate with astrocyte soluble factors to enhance neuronal population. Our data reveal an important role of astrocytes as mediators of T3-induced cerebellar development and partially elucidate the role of cell contact and soluble factors on this process.

Quantitatively distinct requirements for signaling-competent cell spreading on engineered versus natural adhesion ligands

To design synthetic microenvironments that elicit desired cell behaviors, we must better understand the molecular mechanisms by which cells interact with candidate biomaterials. Using cell lines with distinct alpha5beta1 integrin expression profiles, we demonstrate that this integrin mediates cell spreading on substrata coated with genetically engineered artificial extracellular matrix (aECM) proteins containing the RGD sequence (RGD-containing aECM protein [aRGD]) but lacking the PHSRN synergy site. Furthermore, aRGD-mediated adhesion stimulates an intracellular focal adhesion kinase (FAK) signal that is indicative of integrin tethering. Although both aRGD and the natural ECM protein fibronectin (FN) support alpha5beta1 integrin-mediated cell spreading, quantitative single-cell analysis revealed that aRGD-mediated spreading requires ten-fold greater threshold amount of integrin expression than FN-mediated spreading. Our analysis demonstrates that aRGD-based substrata mediate both biophysical (cell spreading) and biochemical (FAK signaling) events via the alpha5beta1 integrin, albeit with efficacy quantitatively distinct from that of natural ECM proteins that possess the full spectrum of adhesion and synergy domains.

Use of nanotopography to study mechanotransduction in fibroblasts--methods and perspectives

The environment around a cell during in vitro culture is unlikely to mimic those in vivo. Preliminary experiments with nanotopography have shown that nanoscale features can strongly influence cell morphology, adhesion, proliferation and gene regulation, but the mechanisms mediating this cell response remain unclear. In this perspective article, we attempt to illustrate that a possible mechanism is direct transmittal of forces encountered by cells during spreading to the nucleus via the cytoskeleton. We further try to illustrate that this 'self-induced' mechanotransduction may alter gene expression by changing interphase chromosome positioning. Whilst the observations described here to show how we think nanotopography can be developed as a tool to look at mechanotransduction are preliminary, we feel they indicate that topography may give cell biologists a non-invasive tool with which to investigate in vitro cellular mechanisms.

Microarray analysis of UVB-regulated genes in keratinocytes: downregulation of angiogenesis inhibitor thrombospondin-1

BACKGROUND

Ultraviolet (UV) B light is an environmental mutagen that induces changes in cutaneous gene expression leading to immune suppression and carcinogenesis. Keratinocytes are a primary target for UVB.

OBJECTIVE

To further delineate UVB-induced gene expression changes in keratinocytes.

METHODS

cDNA microarray technology was utilized to examine gene expression in normal human KC (NHKC) following 20 mJcm(-2) UVB irradiation. Data was confirmed by semi-quantitative RT-PCR.

RESULTS

Microarray analysis revealed 57 genes were upregulated, and 27 genes were downregulated, by at least two-fold following UVB. One downregulated gene was the endogenous angiogenesis inhibitor thrombospondin-1 (TSP-1). Semi-quantitative RT-PCR confirmed persistent downregulation of TSP-1 up to 18h following UVB. Microarray analysis also revealed upregulation of platelet-derived endothelial cell growth factor (PD-ECGF)--an angiogenesis activator.

CONCLUSION

Our results suggest a gene expression mechanism by which UVB induces an angiogenic switch in keratinocytes. This may represent an important early event promoting neovascularization and growth of cutaneous neoplasms.

Expression of the disintegrin metalloprotease, ADAM-10, in prostate cancer and its regulation by dihydrotestosterone, insulin-like growth factor I, and epidermal growth factor in the prostate cancer cell model LNCaP

PURPOSE

The disintegrin metalloprotease ADAM-10 is a multidomain metalloprotease that is potentially significant in tumor progression due to its extracellular matrix-degrading properties. Previously, ADAM-10 mRNA was detected in prostate cancer (PCa) cell lines; however, the presence of ADAM-10 protein and its cellular localization, regulation, and role have yet to be described. We hypothesized that ADAM-10 mRNA and protein may be regulated by growth factors such as 5alpha-dihydrotestosterone, insulin-like growth factor I, and epidermal growth factor, known modulators of PCa cell growth and invasion.

EXPERIMENTAL DESIGN

ADAM-10 expression was analyzed by in situ hybridization and immunohistochemistry in prostate tissues obtained from 23 patients with prostate disease. ADAM-10 regulation was assessed using quantitative reverse transcription-PCR and Western blot analysis in the PCa cell line LNCaP.

RESULTS

ADAM-10 expression was localized to the secretory cells of prostate glands, with additional basal cell expression in benign glands. ADAM-10 protein was predominantly membrane bound in benign glands but showed marked nuclear localization in cancer glands. By Western blot, the 100-kDa proform and the 60-kDa active form of ADAM-10 were synergistically up-regulated in LNCaP cells treated with insulin-like growth factor I plus 5alpha-dihydrotestosterone. Epidermal growth factor also up-regulated both ADAM-10 mRNA and protein.

CONCLUSIONS

This study describes for the first time the expression, regulation, and cellular localization of ADAM-10 protein in PCa. The regulation and membrane localization of ADAM-10 support our hypothesis that ADAM-10 has a role in extracellular matrix maintenance and cell invasion, although the potential role of nuclear ADAM-10 is not yet known.

Nucleus alignment and cell signaling in fibroblasts: response to a micro-grooved topography

Cellular response to scaffold materials is of great importance in cellular and tissue engineering, and it is perhaps the initial cell contact with the scaffold that determines development of new tissue. Material surface morphology has strong effects on cell cytoskeleton and morphology, and it is thought that cells may react to the topography of collagen and surrounding cells during tissue embryology. A poorly understood area is, however, gene-level responses to topography. Thus, this paper used microarray to probe for consistent gene changes in response to lithographically produced topography (12.5 x 2-microm grooves) with time. The results showed many initial gene changes and also down-regulation of gene response with time. Cell and nucleus morphology were also considered, with nuclear deformation linked to cell signaling.

Integrin alphavbeta3 binding to human alpha5-laminins facilitates FGF-2- and VEGF-induced proliferation of human ECV304 carcinoma cells

Human ECV304 cells respond reproducibly by tube formation to complex basement membrane matrices. Laminins are major glycoproteins of basement membranes. We therefore studied the ability of ECV304 cells to attach to defined laminin isoforms and to fibronectin, and identified the involved laminin receptors. The cells bound poorly to fibronectin, to some extent to laminin-1, whereas laminin-2/4 and -10/11 were strong adhesive substrates. Antibody perturbation assays showed that adhesion to laminin-1 was mediated by integrin alpha6beta1, and adhesion to laminin-2/4 by cooperative activity of integrins alpha3beta1 and alpha6beta1. Adhesion of ECV 304 cells to laminin-10/11 was mainly mediated by integrins alpha3beta1, with minor involvement of alpha6beta1/4 and alphavbeta3. Solid-phase binding assays confirmed that integrin alphavbeta3 binds human laminin-10/11 and -10, in an RGD-dependent fashion. Although integrin alphavbeta3 played a very minor role in cell adhesion to laminin-10/11, this interaction facilitated growth factor-induced proliferation of ECV304 cells. In response to FGF-2 or VEGF, the cells proliferated better when attached on laminin-10/11 than on laminin-1, -2/4, or gelatin. The proliferation induced by the joint application of laminin-10/11 and either one of the growth factors could be blocked by antibodies against integrin alphavbeta3. Fragments of several other basement membrane components are known to interact with alphavbeta3. The current data show that that integrin alphavbeta3 can bind intact alpha5-containing laminin trimers. Since the laminin alpha5 chain is broadly expressed in adult basement membranes, this interaction could be physiologically important. Our data suggest that this interaction is involved in the regulation of cellular responses to growth factors known to be involved in epithelial and endothelial development.

Alpha6beta1 integrin induces proteasome-mediated cleavage of erbB2 in breast cancer cells

ErbB2 and alpha6 integrin have been implicated in malignancy of breast cancer cells. Here we have determined the influence of alpha6beta1 integrin on erbB2 signaling in anchorage-independent growth, using MDA-MB435 breast cancer cells. Firstly, we transfected the cells with erbB2 cDNA, and isolated cells with high or low levels of alpha6beta1 integrin by cell sorting (alpha6H-ErbB and alpha6L-ErbB). We found that an erbB ligand, heregulin beta1, enhanced growth activity of alpha6L-ErbB cells, but not alpha6H-ErbB cells. Secondly, we established cells expressing a beta4 integrin deletion mutant (beta4-deltacyt), which selectively inhibited alpha6beta1 integrin expression and adhesion to laminin-1. Again, heregulin beta1 enhanced the growth of erbB2 cDNA-transfected beta4-deltacyt cells, but not mock cells. Western blot analysis revealed that heregulin beta1 stimulated phosphorylation of Akt and its downstream molecules, GSK3beta and p70S6kinase, and that the extent of phosphorylation was greater in ErbB2/beta4-deltacyt cells than ErbB2/mock cells. Furthermore, we found that the erbB2 cytoplasmic domain was truncated in ErbB2/mock cells, which was independent of ligand stimulation and adhesion, and was suppressed by proteasome inhibitors. These results suggest that alpha6beta1 integrin inhibits erbB2 signals by inducing proteasome-dependent proteolytic cleavage of the erbB2 cytoplasmic domain, and may thereby contribute to the regulation of tumor growth.

Undersulfation of proteoglycans and proteins alter C6 glioma cells proliferation, adhesion and extracellular matrix organization

Proteoglycans are considered to be important molecule in cell-microenvironment interactions. They are overexpressed in neoplastic cells modifying their growth and migration in hosts. In this work we verified that undersulfation of proteoglycans and other sulfated molecules, induced by sodium chlorate treatment, inhibited C6 glioma cells proliferation in a dose-dependent way. This effect was restored by the addition of exogenous heparin. We could not detect significant cell mortality in our culture condition. The treatment also impaired in a dose-dependent manner, C6 cell adhesion to extracellular matrix (ECM) proteins (collagen IV, laminin and fibronectin). In addition, sodium chlorate treatment altered C6 glioma cell morphology, from the fibroblast-like to a more rounded one. This effect was accompanied by increased synthesis of fibronectin and alterations in its extracellular network organization. However, we could not observe modifications on laminin organization and synthesis. The results suggest an important connection between sulfation degree with important tumor functions, such as proliferation and adhesion. We suggest that proteoglycans may modulate the glioma microenvironment network during tumor cell progression and invasion.

Regulation of monocyte gene expression by the extracellular matrix and its functional implications

By binding to extracellular matrix (ECM) proteins, integrins integrate signals from outside the cell and transmit them inwards, thereby providing cells with information about location and allowing them to respond to stimuli in a manner appropriate to their environment. This is particularly important for monocytes and macrophages, given their wide distribution throughout the body and the vital role they play in immune and inflammatory responses. Integrin-mediated interaction of monocytes with ECM is a potent regulator of gene expression and is strongly synergized by the presence of growth factors. This synergy between growth factors and integrins is also apparent in the overlap seen in their signaling pathways. Integrin-mediated interaction with ECM results in increased expression of numerous inflammatory and immune response genes, revealing an important role for ECM-integrin interaction in affecting monocyte function and thus impacting on the development of pathologies. This is of particular relevance in the context of immune and inflammatory responses, where integrin-mediated adhesive interactions with the ECM-rich peripheral tissues are central to the localization of both resident and infiltrating monocytes at inflammatory sites. Here, we will review the functional effects of integrin-ECM interactions on monocytes, with particular attention to the regulation of gene expression by ECM and its functional implications.

Cross signaling, cell specificity, and physiology

The literature on intracellular signal transduction presents a confusing picture: every regulatory factor appears to be regulated by all signal transduction cascades and to regulate all cell processes. This contrasts with the known exquisite specificity of action of extracellular signals in different cell types in vivo. The confusion of the in vitro literature is shown to arise from several causes: the inevitable artifacts inherent in reductionism, the arguments used to establish causal effect relationships, the use of less than adequate models (cell lines, transfections, acellular systems, etc.), and the implicit assumption that networks of regulations are universal whereas they are in fact cell and stage specific. Cell specificity results from the existence in any cell type of a unique set of proteins and their isoforms at each level of signal transduction cascades, from the space structure of their components, from their combinatorial logic at each level, from the presence of modulators of signal transduction proteins and of modulators of modulators, from the time structure of extracellular signals and of their transduction, and from quantitative differences of expression of similar sets of factors.

Preferential transformation of human neuronal cells by human adenoviruses and the origin of HEK 293 cells

The 293 cell line was derived by transformation of primary cultures of human embryonic kidney (HEK) cells with sheared adenovirus (Ad)5 DNA. A combination of immunostaining, immunoblot, and microarray analysis showed that 293 cells express the neurofilament (NF) subunits NF-L, NF-M, NF-H, and a-internexin as well as many other proteins typically found in neurons. Three other independently derived HEK lines, two transformed by Ad5 and one by Ad12, also expressed NFs, as did one human embryonic retinal cell line transformed with Ad5. Two rodent kidney lines transformed with Ad12 were also found to express NF proteins, although several rodent kidney cell lines transformed by Ad5 DNA and three HEK cell lines transformed by the SV40 early region did not express NFs. These results suggest that human Ads preferentially transform human neuronal lineage cells. We also demonstrate that the widely used HEK293 cells have an unexpected relationship to neurons, a finding that may require reinterpretation of many previous studies in which it was assumed that HEK293 cells resembled more typical kidney epithelial cells.

Increasing fibroblast response to materials using nanotopography: morphological and genetic measurements of cell response to 13-nm-high polymer demixed islands

It is becoming clear that cells can respond not only to micometric scale topography, but may also to nanometric scale topography. The production of reproducibly sized nanometric features has relied heavily on expensive and time-consuming methods of manufacture, such as electron beam lithography. Polymer demixing of polystyrene and polybromostyrene has been found to produce nanoscale islands of reproducible height, and the islands have been previously shown to effect cell spreading compared to planar surfaces. This study observes morphological, cytoskeletal, and molecular changes in fibroblast reaction to 13-nm-high islands. The methods employed include scanning electron microscopy, fluorescent microscopy, and 1718 gene microarray. The results show that the cells respond to the islands by broad gene up-regulation, notably in the areas of cell signaling, proliferation, cytoskeleton, and production of extracellular matrix proteins. Microscopical results provide confirmation of the microarray findings.

JunB/AP-1 and NF-kappa B-mediated induction of nitric oxide synthase by bovine type I collagen in serum-stimulated murine macrophages

Type I collagen comprises the majority of the total body collagens. In particular, bovine type I collagen is utilized for medical purposes and used widely in a variety of cell culture models as a fibrous component of extracellular matrix. This study was designed to explore the effects of type I collagen on the expression of inducible nitric oxide synthase (iNOS) in serum-stimulated Raw264.7 cells and to study the molecular mechanistic basis. Bovine, but not rat or murine, type I collagen increased NO production in serum-stimulated cells, which resulted from the induction of iNOS, as monitored by Northern and Western blot analyses. Bovine type I collagen in combination with serum activated JunB and JunB/AP-1 transcription complex, as evidenced by supershift and immunodepletion of the retarded AP-1 band with anti-JunB antibody. AP-1 complex was immunodepleted in part by anti-c-Jun or anti-JunD antibody. Extracellular signal-regulated kinase1/2 (ERK1/2), p38 kinase, and c-Jun N-terminal kinase (JNK) were all activated by bovine type I collagen in serum-stimulated cells. PD98059, but not SB203580 or JNK1(-) transfection, inhibited both ERK1/2 phosphorylation and JunB/AP-1 activation. Either PD98059 or MKK1(-) transfection suppressed the iNOS induction. The induction of iNOS accompanied activation of NF-kappa B with degradation of I-kappa B alpha. AP-1 and/or NF-kappa B decoy oligonucleotides and pyrrolidine dithiocarbamate suppressed the iNOS induction, which confirmed involvement of AP-1 and NF-kappa B as transcription factors. These results demonstrated that bovine type I collagen induces iNOS in serum-stimulated murine macrophages through JunB/AP-1 and NF-kappa B activation and that activation of ERK1/2 plays an essential role in JunB/AP-1 activation.

Update on HER-2 as a target for cancer therapy: intracellular signaling pathways of ErbB2/HER-2 and family members

ErbB (also termed HER) receptors are expressed in various tissues of epithelial, mesenchymal and neuronal origin, in which they are involved in the control of diverse biological processes such as proliferation, differentiation, migration and apoptosis. Furthermore, their deregulated expression has been implicated in many types of human cancers and is associated with poor clinical prognosis. Owing to the importance of ErbB proteins in both development and cellular transformation, a lot of attention has been drawn to the intracellular signals initiated by the engagement of this family of receptor tyrosine kinases. This review will focus on the membrane proximal events triggered by the ErbB receptor network and will address questions of how receptor heterodimerization may contribute to signal specification and diversification.