Three-dimensional extracellular matrix culture models of EGFR signalling and drug response

Optimisation of Conditions for the Formation of Spheroids of Head and Neck Squamous Cell Carcinoma Cell Lines for Use as Animal Alternatives

The use of in vitro 3-D cell culture models in cancer research has yielded substantial gains in knowledge on various aspects of tumour biology. Such cell culture models could be useful in the study of head and neck squamous cell carcinoma (HNSCC), where mimicking intratumoral and intertumoral heterogeneity is especially challenging. Our research aims to establish 3-D spheroid models for HNSCC that reproduce in vitro the connections between tumour cells and the surrounding microenvironment. The aims of this study were to determine the optimal conditions for the culture and use of spheroids from HNSCC cell lines and optimal timepoint for using the spheroids obtained, to evaluate the effects of coculture with tumour-specific fibroblasts on spheroid formation, and to investigate spheroid responses to cisplatin treatment. Four HNSCC cell lines (UMSCC-11A, UMSCC-11B, UMSCC-22B and UD-SCC-01) were seeded in flat or round bottom well ultra-low attachment spheroid plates, and spheroid formation was evaluated. The HNSCC cell lines were then cocultured with stromal cells of the tumour microenvironment, producing an accelerated formation of dense spheroids. The viability of cells within the spheroids was assessed during cell culture by using a fluorescent dye. Our results suggest that: three out of the four cell lines tested could form usable spheroids with acceptable viability; the addition of stromal cells did not improve the number of viable cells; and the use of round bottom well plates supported the formation of a single spheroid, whereas flat bottom well plates led to the formation of multiple spheroids of different sizes.

In vitro models as tools for screening treatment options of head and neck cancer

Various in vitro models using primary and established 2- and 3-dimensional cultures, multicellular tumor spheroids, standardized tumor slice cultures, tumor organoids, and microfluidic systems obtained from tumor lesions/biopsies of head and neck cancer (HNC) have been employed for exploring and monitoring treatment options. All of these in vitro models are to a different degree able to capture the diversity of tumors, recapitulate the disease genetically, histologically, and functionally and retain their tumorigenic potential upon xenotransplantation. The models were used for the characterization of the malignant features of the tumors and for in vitro screens of drugs approved for the treatment of HNC, including chemotherapy and radiotherapy as well as recently developed targeted therapies and immunotherapies, or for novel treatments not yet licensed for these tumor entities. The implementation of the best suitable model will enlarge our knowledge of the oncogenic properties of HNC, expand the drug repertoire and help to develop individually tailored treatment strategies resulting in the translation of these findings into the clinic. This review summarizes the different approaches using preclinical in vitro systems with their advantages and disadvantages and their implementation as preclinical platforms to predict disease course, evaluate biomarkers and test therapy efficacy.

Hot or cold: Bioengineering immune contextures into in vitro patient-derived tumor models

In the past decade, immune checkpoint inhibitors (ICI) have proven to be tremendously effective for a subset of cancer patients. However, it is difficult to predict the response of individual patients and efforts are now directed at understanding the mechanisms of ICI resistance. Current models of patient tumors poorly recapitulate the immune contexture, which describe immune parameters that are associated with patient survival. In this Review, we discuss parameters that influence the induction of different immune contextures found within tumors and how engineering strategies may be leveraged to recapitulate these contextures to develop the next generation of immune-competent patient-derived in vitro models.

Precision Medicine Gains Momentum: Novel 3D Models and Stem Cell-Based Approaches in Head and Neck Cancer

Despite the current progress in the development of new concepts of precision medicine for head and neck squamous cell carcinoma (HNSCC), in particular targeted therapies and immune checkpoint inhibition (CPI), overall survival rates have not improved during the last decades. This is, on the one hand, caused by the fact that a significant number of patients presents with late stage disease at the time of diagnosis, on the other hand HNSCC frequently develop therapeutic resistance. Distinct intratumoral and intertumoral heterogeneity is one of the strongest features in HNSCC and has hindered both the identification of specific biomarkers and the establishment of targeted therapies for this disease so far. To date, there is a paucity of reliable preclinical models, particularly those that can predict responses to immune CPI, as these models require an intact tumor microenvironment (TME). The "ideal" preclinical cancer model is supposed to take both the TME as well as tumor heterogeneity into account. Although HNSCC patients are frequently studied in clinical trials, there is a lack of reliable prognostic biomarkers allowing a better stratification of individuals who might benefit from new concepts of targeted or immunotherapeutic strategies. Emerging evidence indicates that cancer stem cells (CSCs) are highly tumorigenic. Through the process of stemness, epithelial cells acquire an invasive phenotype contributing to metastasis and recurrence. Specific markers for CSC such as CD133 and CD44 expression and ALDH activity help to identify CSC in HNSCC. For the majority of patients, allocation of treatment regimens is simply based on histological diagnosis and on tumor location and disease staging (clinical risk assessments) rather than on specific or individual tumor biology. Hence there is an urgent need for tools to stratify HNSCC patients and pave the way for personalized therapeutic options. This work reviews the current literature on novel approaches in implementing three-dimensional (3D) HNSCC in vitro and in vivo tumor models in the clinical daily routine. Stem-cell based assays will be particularly discussed. Those models are highly anticipated to serve as a preclinical prediction platform for the evaluation of stable biomarkers and for therapeutic efficacy testing.

Morphological and molecular characteristics of spheroid formation in HT-29 and Caco-2 colorectal cancer cell lines

Background

Relapse and metastasis in colorectal cancer (CRC) are often attributed to cancer stem-like cells (CSCs), as small sub-population of tumor cells with ability of drug resistance. Accordingly, development of appropriate models to investigate CSCs biology and establishment of effective therapeutic strategies is warranted. Hence, we aimed to assess the capability of two widely used and important colorectal cancer cell lines, HT-29 and Caco-2, in generating spheroids and their detailed morphological and molecular characteristics.

Methods

CRC spheroids were developed using hanging drop and forced floating in serum-free and non-attachment conditions and their morphological features were evaluated by scanning electron microscopy (SEM). Then, the potential of CSCs enrichment in spheroids was compared to their adherent counterparts by analysis of serial sphere formation capacity, real-time PCR of key stemness genes (KLF4, OCT4, SOX2, NANOG, C-MYC) and the expression of potential CRC-CSCs surface markers (CD166, CD44, and CD133) by flow cytometry. Finally, the expression level of some EMT-related (Vimentin, SNAIL1, TWIST1, N-cadherin, E-cadherin, ZEB1) and multi-drug resistant (ABCB1, ABCC1, ABCG2) genes was evaluated.

Results

Although with different morphological features, both cell lines were formed CSCs-enriched spheroids, indicated by ability to serial sphere formation, significant up-regulation of stemness genes, SOX2, C-MYC, NANOG and OCT4 in HT-29 and SOX2, C-MYC and KLF4 in Caco-2 spheroids (p-value < 0.05) and increased expression of CRC-CSC markers compared to parental cells (p-value < 0.05). Additionally, HT-29 spheroids exhibited a significant higher expression of both ABCB1 and ABCG2 (p-value = 0.02). The significant up-regulation of promoting EMT genes, ZEB1, TWIST1, E-cadherin and SNAIL1 in HT-29 spheroids (p-value = 0.03), SNAIL1 and Vimentin in Caco-2 spheroids (p-value < 0.05) and N-cadherin down-regulation in both spheroids were observed.

Conclusion

Enrichment of CSC-related features in HT-29 and Caco-2 (for the first time without applying special scaffold/biochemical) spheroids, suggests spheroid culture as robust, reproducible, simple and cost-effective model to imitate the complexity of in vivo tumors including self-renewal, drug resistance and invasion for in vitro research of CRC-CSCs.

Modeling Epidermal Growth Factor Inhibitor-mediated Enhancement of Photodynamic Therapy Efficacy Using 3D Mesothelioma Cell Culture

We have demonstrated that lung-sparing surgery with intraoperative photodynamic therapy (PDT) achieves remarkably extended survival for patients with malignant pleural mesothelioma (MPM). Nevertheless, most patients treated using this approach experience local recurrence, so it is essential to identify ways to enhance tumor response. We previously reported that PDT transiently activates EGFR/STAT3 in lung and ovarian cancer cells and inhibiting EGFR via erlotinib can increase PDT sensitivity. Additionally, we have seen higher EGFR expression associating with worse outcomes after Photofrin-mediated PDT for MPM, and the extensive desmoplastic reaction associated with MPM influences tumor phenotype and therapeutic response. Since extracellular matrix (ECM) proteins accrued during stroma development can alter EGF signaling within tumors, we have characterized novel 3D models of MPM to determine their response to erlotinib combined with Photofrin-PDT. Our MPM cell lines formed a range of acinar phenotypes when grown on ECM gels, recapitulating the locally invasive phenotype of MPM in pleura and endothoracic fascia. Using these models, we confirmed that EGFR inhibition increases PDT cytotoxicity. Together with emerging evidence that EGFR inhibition may improve survival of lung cancer patients through immunologic and direct cell killing mechanisms, these results suggest erlotinib-enhanced PDT may significantly improve outcomes for MPM patients.

Systematic analysis of tumour cell-extracellular matrix adhesion identifies independent prognostic factors in breast cancer

Tumour cell-extracellular matrix (ECM) interactions are fundamental for discrete steps in breast cancer progression. In particular, cancer cell adhesion to ECM proteins present in the microenvironment is critical for accelerating tumour growth and facilitating metastatic spread. To assess the utility of tumour cell-ECM adhesion as a means for discovering prognostic factors in breast cancer survival, here we perform a systematic phenotypic screen and characterise the adhesion properties of a panel of human HER2 amplified breast cancer cell lines across six ECM proteins commonly deregulated in breast cancer. We determine a gene expression signature that defines a subset of cell lines displaying impaired adhesion to laminin. Cells with impaired laminin adhesion showed an enrichment in genes associated with cell motility and molecular pathways linked to cytokine signalling and inflammation. Evaluation of this gene set in the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) cohort of 1,964 patients identifies the F12 and STC2 genes as independent prognostic factors for overall survival in breast cancer. Our study demonstrates the potential of in vitro cell adhesion screens as a novel approach for identifying prognostic factors for disease outcome.

The role of ADAM17 in tumorigenesis and progression of breast cancer

A disintegrin and metalloproteinase (ADAM) family members are known to process the target membrane-bound molecules through the quick induction of their protease activities under interaction with other molecules, which have diverse roles in tissue morphogenesis and pathophysiological remodeling. Among these, ADAM17 is a membrane-bound protease that sheds the extracellular domain of various receptors or its ligands from the cell membrane and subsequently activates downstream signaling transduction pathways. Importantly, breast cancer remains a mainspring of cancer-induced death in women, and numerous regulatory pathways have been implicated in the formation of breast cancer. Substantial evidence has demonstrated that an obvious increased in ADAM17 cell surface expression has been discovered in breast cancer and was shown to be associated with mammary tumorigenesis, invasiveness, and drug resistance. Over the last decades, it has received more than its share of attention that ADAM17 plays a potential role in breast cancer, including cell proliferation, invasion, angiogenesis, apoptosis, and trastuzumab resistance. In our review, we discuss the mechanisms through which ADAM17 acts on breast cancer tumorigenesis and progression. Thus, this will provide further impetus for exploiting ADAM17 as a new target for breast cancer treatment.

Drug Discovery Approaches Utilizing Three-Dimensional Cell Culture

Historically, two-dimensional (2D) cell culture has been the preferred method of producing disease models in vitro. Recently, there has been a move away from 2D culture in favor of generating three-dimensional (3D) multicellular structures, which are thought to be more representative of the in vivo environment. This transition has brought with it an influx of technologies capable of producing these structures in various ways. However, it is becoming evident that many of these technologies do not perform well in automated in vitro drug discovery units. We believe that this is a result of their incompatibility with high-throughput screening (HTS). In this study, we review a number of technologies, which are currently available for producing in vitro 3D disease models. We assess their amenability with high-content screening and HTS and highlight our own work in attempting to address many of the practical problems that are hampering the successful deployment of 3D cell systems in mainstream research.

Overexpression of miR‑145 in U87 cells reduces glioma cell malignant phenotype and promotes survival after in vivo implantation

In the present study, we sought to elucidate the effect of miR‑145 on glioma cell progression and its mechanisms of action. We examined the effects of miR‑145 on proliferation and invasion of U87 glioma cells and on capillary tube formation. Our data show that restoration of miR‑145 in U87 glioma cells significantly reduced their in vitro proliferation, invasion and angiogenesis. However, decreased miR‑145 expression promoted U87 glioma cell proliferation, invasion and angiogenesis, and reduced-expression of miR‑145 increased ADAM17 and EGFR expression in U87 cells. Overexpression of miR‑145 reduced ADAM17 and EGFR expression. VEGF secretion and VEGF expression were decreased by increased miR‑145 expression in U87 cells and were reversed by miR‑145 downregulation in vitro. Nude mice with intracerebral implantation of U87 overexpressing miR‑145 cells exhibited significantly reduced tumor growth and promoted survival compared with control groups. Taken together, these results suggest a role for miR‑145 as a tumor suppressor which inhibits glioma cell proliferation, invasion and angiogenesis in vitro and reduces glioma growth in vivo.

Modeling human carcinomas: physiologically relevant 3D models to improve anti-cancer drug development

Anti-cancer drug development is inefficient, mostly due to lack of efficacy in human patients. The high fail rate is partly due to the lack of predictive models or the inadequate use of existing preclinical test systems. However, progress has been made and preclinical models were improved or newly developed, which all account for basic features of solid cancers, three-dimensionality and heterotypic cell interaction. Here we give an overview of available in vivo and in vitro models of cancer, which meet the criteria of being 3D and mirroring human tumor-stroma interactions. We only focus on drug response models without touching models for pharmacokinetic and dynamic, toxicity or delivery aspects.

TACE-dependent TGFα shedding drives triple-negative breast cancer cell invasion

The epidermal growth factor receptor (EGFR) is frequently expressed in triple-negative breast cancer (TNBC) and is a marker of poor prognosis in this patient population. Because activating mutations in this kinase are very rare events in breast cancer, we screened breast tumor gene expression profiles to examine the distribution of EGFR ligand expression. Of the six known EGFR ligands, transforming growth factor alpha (TGFα) was expressed more highly in triple-negative breast tumors than in tumors of other subtypes. TGFα is synthesized as a transmembrane precursor requiring tumor necrosis factor alpha converting enzyme (TACE)/ADAM17-dependent proteolytic release to activate its receptor. In our study, we show that an inhibitor of this proteolytic release blocks invasion, migration and colony formation by several TNBC cell lines. Each of the effects of the drug was reversed upon expression of a soluble TGFα mutant that does not require TACE activity, implicating this growth factor as a key metalloproteinase substrate for these phenotypes. Together, these data demonstrate that TACE-dependent TGFα shedding is a key process driving EGFR activation and subsequent proliferation and invasion in TNBC cell lines.

Gallic acid: molecular rival of cancer

Gallic acid, a predominant polyphenol, has been shown to inhibit carcinogenesis in animal models and in vitro cancerous cell lines. The inhibitory effect of gallic acid on cancer cell growth is mediated via the modulation of genes which encodes for cell cycle, metastasis, angiogenesis and apoptosis. Gallic acid inhibits activation of NF-κB and Akt signaling pathways along with the activity of COX, ribonucleotide reductase and GSH. Moreover, gallic acid activates ATM kinase signaling pathways to prevent the processes of carcinogenesis. The data so far available, both from in vivo and in vitro studies, indicate that this dietary polyphenol could be promising agent in the field of cancer chemoprevention.

Impact of the 3D microenvironment on phenotype, gene expression, and EGFR inhibition of colorectal cancer cell lines

Three-dimensional (3D) tumor cell cultures grown in laminin-rich-extracellular matrix (lrECM) are considered to reflect human tumors more realistic as compared to cells grown as monolayer on plastic. Here, we systematically investigated the impact of ECM on phenotype, gene expression, EGFR signaling pathway, and on EGFR inhibition in commonly used colorectal cancer (CRC) cell lines. LrECM on-top (3D) culture assays were performed with the CRC cell lines SW-480, HT-29, DLD-1, LOVO, CACO-2, COLO-205 and COLO-206F. Morphology of lrECM cultivated CRC cell lines was determined by phase contrast and confocal laser scanning fluorescence microscopy. Proliferation of cells was examined by MTT assay, invasive capacity of the cell lines was assayed using Matrigel-coated Boyden chambers, and migratory activity was determined employing the Fence assay. Differential gene expression was analyzed at the transcriptional level by the Agilent array platform. EGFR was inhibited by using the specific small molecule inhibitor AG1478. A specific spheroid growth pattern was observed for all investigated CRC cell lines. DLD-1, HT-29 and SW-480 and CACO-2 exhibited a clear solid tumor cell formation, while LOVO, COLO-205 and COLO-206F were characterized by forming grape-like structures. Although the occurrence of a spheroid morphology did not correlate with an altered migratory, invasive, or proliferative capacity of CRC cell lines, gene expression was clearly altered in cells grown on lrECM as compared to 2D cultures. Interestingly, in KRAS wild-type cell lines, inhibition of EGFR was less effective in lrECM (3D) cultures as compared to 2D cell cultures. Thus, comparing both 2D and 3D cell culture models, our data support the influence of the ECM on cancer growth. Compared to conventional 2D cell culture, the lrECM (3D) cell culture model offers the opportunity to investigate permanent CRC cell lines under more physiological conditions, i.e. in the context of molecular therapeutic targets and their pharmacological inhibition.

EGFR/JIP-4/JNK2 signaling attenuates cetuximab-mediated radiosensitization of squamous cell carcinoma cells

EGF receptor (EGFR) promotes tumor growth as well as radio- and chemoresistance in various human malignancies including squamous cell carcinomas (SCC). In addition to deactivation of prosurvival signaling, cetuximab-mediated EGFR targeting might concomitantly induce self-attenuating signaling bypasses. Identification of such bypass mechanisms is key to improve the efficacy of targeted approaches. Here, we show great similarity of EGFR signaling and radiation survival in cetuximab-treated SCC cells grown in a more physiologic three-dimensional extracellular matrix and as tumor xenografts in contrast to conventional monolayer cell cultures. Using phosphoproteome arrays, we observed strong induction of JNK2 phosphorylation potentially resulting from cetuximab-inhibited EGFR through c-jun-NH(2)-kinase (JNK)-interacting protein-4 (JIP-4), which was identified using an immunoprecipitation-mass spectrometric approach. Inhibition of this signaling bypass by JIP-4 or JNK2 knockdown or pharmacologic JNK2 inhibition enhanced cetuximab efficacy and tumor cell radiosensitivity. Our findings add new facets to EGFR signaling and indicate signaling bypass possibilities of cancer cells to improve their survival on cetuximab treatment. By deactivation of cetuximab-self-attenuating JNK2-dependent signaling, the cytotoxicity, and radiosensitizing potential of cetuximab can be augmented.

ADAM17 promotes glioma cell malignant phenotype

A disintegrin and metalloproteinase-17 (ADAM17) is involved in proteolytic ectodomain shedding of several membrane-bound growth factors and cytokines. The expression and activity of ADAM17 increase under some pathological conditions such as stroke and cancer. ADAM17 promotes neural progenitor cell migration and contributes to neurogenesis after stroke and breast cancer growth and invasion. In the present study, we sought to elucidate whether ADAM17 contributes to glioma progression. To this end, we examined the role of ADAM17 in the proliferation, invasion, and tube formation of U87 human glioma cells in vitro and tumor growth in vivo. Stable transfection of the U87 cell line with either a plasmid for over-expression of human ADAM17, or a siRNA to ADAM17 was employed in this study to establish high- or low-ADAM17 expression in glioma cells, respectively. For study of mechanism, the ADAM17 inhibitor TAPI-2 and the PI3K-AKT inhibitor LY294002 were used to counteract high-ADAM17 expression and the activated PI3K-AKT pathway, respectively. Proliferation of glioma cells were tested by thiazolyl blue tetrazolium bromide (MTT) assay, bromodeoxyuridine incorporation assay, growth curve, and sulforhodamine B assay. Matrigel invasion assays were used to assess the ability of U87 cells to penetrate the extracellular matrix (ECM). A Matrigel tube formation assay was performed to test capillary tube formation ability. EGFR-PI3K-Akt pathway activation in U87 cells under different ADAM17 expression levels were tested by Western blot. Our data show that ADAM17 promotes the U87 malignant phenotype by increased proliferation, invasion, angiogenesis, and in vivo tumor growth. Tumor growth in nude mice was significantly inhibited by ADAM17 inhibitor and A17-shRNA in vivo transfection. TGF-α, VEGF secretion, and VEGF expression was increased by ADAM17 and counteracted by ADAM17 siRNA, TAPI-2, and LY294002 in U87 cells. ADAM17 activated, whereas ADAM17 siRNA, TAPI-2, and LY294002 deactivated the EGFR-PI3K-AKT signal pathway, which correlated with U87 cell malignant phenotype changes. This study suggests ADAM17 contributes to glioma progression through activation of the EGFR-PI3K-AKT signal pathway.

Lung cancer cell lines: Useless artifacts or invaluable tools for medical science?

Multiple cell lines (estimated at 300-400) have been established from human small cell (SCLC) and non-small cell lung cancers (NSCLC). These cell lines have been widely dispersed to and used by the scientific community worldwide, with over 8000 citations resulting from their study. However, there remains considerable skepticism on the part of the scientific community as to the validity of research resulting from their use. These questions center around the genomic instability of cultured cells, lack of differentiation of cultured cells and absence of stromal-vascular-inflammatory cell compartments. In this report we discuss the advantages and disadvantages of the use of cell lines, address the issues of instability and lack of differentiation. Perhaps the most important finding is that every important, recurrent genetic and epigenetic change including gene mutations, deletions, amplifications, translocations and methylation-induced gene silencing found in tumors has been identified in cell lines and vice versa. These "driver mutations" represented in cell lines offer opportunities for biological characterization and application to translational research. Another potential shortcoming of cell lines is the difficulty of studying multistage pathogenesis in vitro. To overcome this problem, we have developed cultures from central and peripheral airways that serve as models for the multistage pathogenesis of tumors arising in these two very different compartments. Finally the issue of cell line contamination must be addressed and safeguarded against. A full understanding of the advantages and shortcomings of cell lines is required for the investigator to derive the maximum benefit from their use.

ADAM17 promotes breast cancer cell malignant phenotype through EGFR-PI3K-AKT activation

A disintegrin and metalloproteinase-17 (ADAM17) is involved in proteolytic ectodomain shedding of several membrane-bound growth factors and cytokines. The expression and activity of ADAM17 increase under some pathological conditions such as stroke and glioma. ADAM17 promotes neural progenitor cell migration and contributes to stroke-induced neurogenesis after stroke and brain tumor growth and invasion. In the present study, we sought to elucidate whether ADAM17 contributes to breast cancer progression and its mechanisms. To this end, we examined the role of ADAM17 in the proliferation, invasion and tube formation of MDA-MB-231 breast cancer cells in vitro. Stable transfection of the MDA-MB-231 cell line with either a plasmid for overexpression of human ADAM17, or a siRNA to ADAM17 was employed in this study to establish high or low ADAM17 expression in breast cancer cells, respectively. For study of mechanism, the ADAM17 inhibitor TAPI-2 and the PI3K-AKT inhibitor LY294002 were used to counteract high ADAM17 expression or the activated PI3K-AKT pathway. Proliferation of MDA-MB-231 breast cancer cells were tested by MTT, Bromodeoxyuridine incorporation assay, growth curve and sulforhodamine B assay. Matrigel invasion assays were used to assess the ability of MDA-MB-231 cells to penetrate the Extra Cellular Matrix. A Matrigel tube formation assay was performed to test capillary tube formation ability. EGFR-PI3K-Akt pathway activation in MDA-MB-231 cells under different ADAM17 expression levels were tested by western blot and ELISA. Our data show that ADAM17 promotes the MDA-MB-231 malignant phenotype by increased proliferation, invasion and angiogenesis. TGFalpha, VEGF secretion and VEGF expression was increasing by ADAM17 and counteracted by ADAM17 siRNA, TAPI-2 and LY294002 in MDA-MB-231 cells. ADAM17 activated, whereas ADAM17 siRNA, TAPI-2 and LY294002 deactivated the EGFR-PI3K-AKT signal pathway, which correlated with MDA-MB-231 cell malignant phenotype changes. This study suggests ADAM17 contributes to breast cancer progression through activation of the EGFR-PI3K-AKT signal pathway.

Factors controlling matrix turnover in health and disease

The impact of changes in matrix turnover on disease processes is gradually becoming more widely understood and appreciated. Similarly, the importance of interactions between the cellular and acellular components of any given tissue is finally being realized. An unhealthy cell does not make a healthy matrix; likewise an unhealthy matrix often leads to the demise of the cells within it, or at the very least to major changes in cell phenotype. We can therefore no longer investigate these two components in isolation, because the matrix so often contributes to cellular signalling pathways, and these in turn can lead to changes in matrix turnover. This is a long way from the traditional view of the role of the extracellular matrix, or 'ground substance', in filling the spaces between the cells and providing physical support for them. Just over 100 delegates assembled at Sheffield Hallam University for the Joint BSMB (British Society for Matrix Biology)/Biochemical Society Focused Meeting on Matrix Turnover: Mechanisms and Common Denominators on 2-3 April 2007. The stated aim of the meeting was to aid and encourage interactions between scientists working in various areas of matrix biology, and to this end there were sessions on intervertebral disc, turnover in the CNS (central nervous system), fibroses and tumour-stroma interactions, as well as a session covering general topics. The involvement of both the BSMB and Biochemical Society membership increased the potential for interactions between scientists and hopefully increased the value of the meeting for all the delegates. This issue of Biochemical Society Transactions contains papers written by those who gave oral presentations at the meeting. I think it is fair to conclude from their talks and the papers presented here that the 'common denominators' involved in matrix turnover include cytokine and growth factor signalling pathways that control the rates of matrix synthesis and breakdown, and which, in many disease processes, lead to an uncoupling of synthesis and breakdown and thereby the loss of homoeostasis. Evidently, the make-up of the matrix surrounding cells profoundly affects cell phenotype and behaviour through various signalling pathways. Numerous environmental stimuli may trigger these events, and a host of genes are undoubtedly involved in generating predisposing genotypes. Such factors appear to be common to many diseases involving matrix turnover.

Tackling EGFR signaling with TACE antagonists: a rational target for metalloprotease inhibitors in cancer

TNF-alpha converting enzyme (TACE/ADAM17) is a transmembrane metalloprotease that plays a key role in the cleavage and mobilization of receptor ligands that are initially synthesized as membrane-tethered precursors. For many years, attention has focused on the role of TACE-dependent TNF-alpha cleavage in arthritis and, more recently, it has become apparent that TACE also plays an important role in regulating epidermal growth factor receptor activity in several tumor types. This review presents the background to these findings and a rationale for the continued development of TACE inhibitors for the treatment of epidermal growth factor receptor-dependent epithelial tumors.