Tumors are unique organs defined by abnormal signaling and context

In silico ascription of gene expression differences to tumor and stromal cells in a model to study impact on breast cancer outcome

Breast tumors consist of several different tissue components. Despite the heterogeneity, most gene expression analyses have traditionally been performed without prior microdissection of the tissue sample. Thus, the gene expression profiles obtained reflect the mRNA contribution from the various tissue components. We utilized histopathological estimations of area fractions of tumor and stromal tissue components in 198 fresh-frozen breast tumor tissue samples for a cell type-associated gene expression analysis associated with distant metastasis. Sets of differentially expressed gene-probes were identified in tumors from patients who developed distant metastasis compared with those who did not, by weighing the contribution from each tumor with the relative content of stromal and tumor epithelial cells in their individual tumor specimen. The analyses were performed under various assumptions of mRNA transcription level from tumor epithelial cells compared with stromal cells. A set of 30 differentially expressed gene-probes was ascribed solely to carcinoma cells. Furthermore, two sets of 38 and five differentially expressed gene-probes were mostly associated to tumor epithelial and stromal cells, respectively. Finally, a set of 26 differentially expressed gene-probes was identified independently of cell type focus. The differentially expressed genes were validated in independent gene expression data from a set of laser capture microdissected invasive ductal carcinomas. We present a method for identifying and ascribing differentially expressed genes to tumor epithelial and/or stromal cells, by utilizing pathologic information and weighted t-statistics. Although a transcriptional contribution from the stromal cell fraction is detectable in microarray experiments performed on bulk tumor, the gene expression differences between the distant metastasis and no distant metastasis group were mostly ascribed to the tumor epithelial cells of the primary breast tumors. However, the gene PIP5K2A was found significantly elevated in stroma cells in distant metastasis group, compared to stroma in no distant metastasis group. These findings were confirmed in gene expression data from the representative compartments from microdissected breast tissue. The method described was also found to be robust to different histopathological procedures.

Metastasis: tumor cells becoming MENAcing

During breast cancer metastasis cells emigrate from the primary tumor to the bloodstream, and this carries them to distant sites where they infiltrate and sometimes form metastases within target organs. These cells must penetrate the dense extracellular matrix comprising the basement membrane of the mammary duct/acinus and migrate toward blood and lymphatic vessels, processes that mammary tumor cells execute primarily using epidermal growth factor (EGF)-dependent protrusive and migratory activity. Here, we focus on how the actin regulatory protein Mena affects EGF-elicited movement, invasion and metastasis. Recent findings indicate that, in invasive migratory tumor cells, Mena isoforms that endow heightened sensitivity to EGF and increased protrusive and migratory abilities are upregulated, whereas other isoforms are selectively downregulated. This change in Mena isoform expression enables tumor cells to invade in response to otherwise benign EGF stimulus levels and could offer an opportunity to identify metastatic risk in patients.

Tumor engineering: the other face of tissue engineering

Advances in tissue engineering have been accomplished for years by employing biomimetic strategies to provide cells with aspects of their original microenvironment necessary to reconstitute a unit of both form and function for a given tissue. We believe that the most critical hallmark of cancer is loss of integration of architecture and function; thus, it stands to reason that similar strategies could be employed to understand tumor biology. In this commentary, we discuss work contributed by Fischbach-Teschl and colleagues to this special issue of Tissue Engineering in the context of 'tumor engineering', that is, the construction of complex cell culture models that recapitulate aspects of the in vivo tumor microenvironment to study the dynamics of tumor development, progression, and therapy on multiple scales. We provide examples of fundamental questions that could be answered by developing such models, and encourage the continued collaboration between physical scientists and life scientists not only for regenerative purposes, but also to unravel the complexity that is the tumor microenvironment.

Cellular mechanisms regulating epithelial morphogenesis and cancer invasion

The cellular mechanisms driving mammalian epithelial morphogenesis are of significant fundamental and practical interest. Historically, these processes have been difficult to study directly, owing to the opacity and relative inaccessibility of mammalian tissues. Recent experimental advances in timelapse imaging and in 3D organotypic culture have enabled direct observation of epithelial morphogenesis. In the mammary gland, branching morphogenesis is observed to proceed through a novel form of collective epithelial migration. The active unit of morphogenesis is a multilayered epithelium with reduced apico-basal polarity, within which cells rearranged vigorously. From within this multilayered state, new ducts initiate and elongate into the matrix without leading cellular extensions or dedicated leaders. We discuss the implications of these findings on our understanding of epithelial morphogenesis in other organs and in cancer progression.

Molecular anatomy of breast cancer stroma and its prognostic value in estrogen receptor-positive and -negative cancers

PURPOSE

The purpose of this study was to identify genes enriched in breast cancer stroma, assess the stromal gene expression differences between estrogen receptor (ER) -positive and -negative cancers, and separately determine their prognostic value in these two subtypes of breast cancers.

METHODS

We compared gene expression profiles of pairs of fine-needle (stroma-poor) and core-needle (stroma-rich) biopsies from 37 cancers to identify stroma-associated genes. We defined stromal metagenes and tested their prognostic values in 684 node-negative patients who received no systemic adjuvant therapy and 259 tamoxifen-treated patients.

RESULTS

We identified 293 probe sets overexpressed in core biopsies; these included five highly coexpressed gene clusters (metagenes) corresponding to immune functions and extracellular matrix components. These genes showed quantitative and qualitative differences between ER-positive and ER-negative cancers. A B-cell/plasma cell metagene showed strong prognostic value in ER-positive highly proliferative cancers, a lesser prognostic value in ER-negative cancers, and no prognostic value in ER-positive cancers with low proliferation. The hazard ratio for distant relapse in the lowest compared with the highest tertile of the pooled prognostic data set was 4.29 (95% CI, 2.04 to 9.01; P = .001) in ER-positive cancers and 3.34 (95% CI, 1.60 to 6.97; P = .001) in ER-negative cancers. This remained significant in multivariate analysis including routine variables and other genomic prognostic scores. As a result of quantitative differences in this metagene between ER-positive and ER-negative cancers, different thresholds apply in the two subgroups. Other stromal metagenes had inconsistent prognostic value.

CONCLUSION

Among ER-negative and ER-positive highly proliferative cancers, a subset of tumors with high expression of a B-cell/plasma cell metagene carries a favorable prognosis.

Breast carcinoma-associated fibroblasts rarely contain p53 mutations or chromosomal aberrations

It has become increasingly clear that the cells within the tumor microenvironment play a critical role in cancer growth and metastasis. Studies in experimental models suggest that carcinoma-associated fibroblasts (CAF) differ from normal fibroblasts and are capable of promoting cancer progression through a variety of mechanisms. At present, a definitive view is lacking on whether genomic abnormalities are present and whether they might underlie the observed phenotypic differences. This study reports the molecular analysis of the largest series of breast CAFs reported to date, with an array comparative genomic hybridization-based DNA copy number analysis of cultured CAFs derived from 25 freshly resected human breast cancers. We found DNA copy number changes consisting of the whole arm of chromosomes 6p and 9p plus interstitial 4q loss in only one sample. No abnormalities were observed in non-tumor-associated fibroblast counterparts. Karyotyping of the same CAF revealed further chromosomal abnormalities, which included clonal loss of chromosomes, chromosomal duplications, and less frequent chromosomal rearrangements. These abnormalities were not associated with alterations in the global gene expression profile of this particular CAF, relative to its non-tumor-associated fibroblast counterpart. Moreover, this particular patient's CAF also displayed the only p53 mutation in the cohort, the first time such a mutation has been reported in freshly cultured human CAFs. These findings argue that the procancerous effects of CAFs are unlikely to be due to DNA copy number-type genomic abnormalities in the CAFs themselves. As such, breast CAFs should be mainly regarded as genomically stable cellular constituents that exist within complex cancer microenvironments.

Drosophila as a novel therapeutic discovery tool for thyroid cancer

BACKGROUND

Multiple endocrine neoplasia type II (MEN2) is a rare but aggressive cancer for which no effective treatment currently exists. A Drosophila model was developed to identify novel genetic modifier loci of oncogenic RET, as well as to provide a whole animal system to rapidly identify compounds that suppressed RET-dependent MEN2. ZD6474 (Vandetanib), currently in phase III trials, suppressed tumorigenesis in MEN2 model flies, demonstrating for the first time the effectiveness of a Drosophila-based whole animal model for identifying therapeutically useful compounds.

SUMMARY

Clinical data suggest that drug mono-therapy for MEN2 and other cancers typically yield only moderate benefits as patients develop drug resistance and suffer from drug-induced pathway feedback. Combinations of drugs that target different nodes of the oncogenic pathway are an effective way to prevent resistance as well as feedback. Identifying the optimal drug-dose combinations for therapy poses a significant challenge in existing mouse models. Fly models offer a means to quickly and effectively identify drug combinations that are well tolerated and potently suppress the MEN2 phenotype. This approach may also identify differences in therapeutic responses between the two subtypes of MEN2--MEN2A and MEN2B--providing additional therapeutic insights.

CONCLUSIONS

Fly models have proven useful for identifying known drugs as well as novel compounds that, as single agents or in combinations, effectively suppress the MEN2 syndrome. These findings validate the use of fly models for both drug discovery as well as identification of useful drug combinations. In the future, rapid pairing of new genomic information with increasingly complex fly models will aid us in efforts to further tailor drug treatments toward personalized medicine.

The role of the microenvironment in mammary gland development and cancer

The mammary gland is composed of a diverse array of cell types that form intricate interaction networks essential for its normal development and physiologic function. Abnormalities in these interactions play an important role throughout different stages of tumorigenesis. Branching ducts and alveoli are lined by an inner layer of secretory luminal epithelial cells that produce milk during lactation and are surrounded by contractile myoepithelial cells and basement membrane. The surrounding stroma comprised of extracellular matrix and various cell types including fibroblasts, endothelial cells, and infiltrating leukocytes not only provides a scaffold for the organ, but also regulates mammary epithelial cell function via paracrine, physical, and hormonal interactions. With rare exceptions breast tumors initiate in the epithelial compartment and in their initial phases are confined to the ducts but this barrier brakes down with invasive progression because of a combination of signals emitted by tumor epithelial and various stromal cells. In this article, we overview the importance of cellular interactions and microenvironmental signals in mammary gland development and cancer.

Extracellular matrix proteins and tumor angiogenesis

Tumor development is a complex process that relies on interaction and communication between a number of cellular compartments. Much of the mass of a solid tumor is comprised of the stroma which is richly invested with extracellular matrix. Within this matrix are a host of matricellular proteins that regulate the expression and function of a myriad of proteins that regulate tumorigenic processes. One of the processes that is vital to tumor growth and progression is angiogenesis, or the formation of new blood vessels from preexisting vasculature. Within the extracellular matrix are structural proteins, a host of proteases, and resident pro- and antiangiogenic factors that control tumor angiogenesis in a tightly regulated fashion. This paper discusses the role that the extracellular matrix and ECM proteins play in the regulation of tumor angiogenesis.

A structure-guided approach to creating covalent FGFR inhibitors

The fibroblast growth factor receptor tyrosine kinases (FGFR1, 2, 3, and 4) represent promising therapeutic targets in a number of cancers. We have developed the first potent and selective irreversible inhibitor of FGFR1, 2, 3, and 4, which we named FIIN-1 that forms a covalent bond with cysteine 486 located in the P loop of the FGFR1 ATP binding site. We demonstrated that the inhibitor potently inhibits Tel-FGFR1-transformed Ba/F3 cells (EC(50) = 14 nM) as well as numerous FGFR-dependent cancer cell lines. A biotin-derivatized version of the inhibitor, FIIN-1-biotin, was shown to covalently label FGFR1 at Cys486. FIIN-1 is a useful probe of FGFR-dependent cellular phenomena and may provide a starting point of the development of therapeutically relevant irreversible inhibitors of wild-type and drug-resistant forms of FGFR kinases.

Identification of EpCAM as a molecular target of prostate cancer stroma

To delineate the molecular changes that occur in the tumor microenvironment, we previously performed global transcript analysis of human prostate cancer specimens using tissue microdissection and expression microarrays. Epithelial and stromal compartments were individually studied in both tumor and normal fields. Tumor-associated stroma showed a distinctly different expression pattern compared with normal stroma, having 44 differentially expressed transcripts, the majority of which were up-regulated. In the present study, one of the up-regulated transcripts, epithelial cell adhesion activating molecule, was further evaluated at the protein level in 20 prostate cancer cases using immunohistochemistry and a histomathematical analysis strategy. The epithelial cell adhesion activating molecule showed a 76-fold expression increase in the tumor-associated stroma, as compared with matched normal stroma. Moreover, Gleason 4 or 5 tumor stroma was increased 170-fold relative to matched normal stroma, whereas the Gleason 3 tumor area showed only a 36-fold increase, indicating a positive correlation with Gleason tumor grade. Since the stromal compartment may be particularly accessible to vascular-delivered agents, epithelial cell adhesion activating molecule could become a valuable molecular target for imaging or treatment of prostate cancer.

Heparin regulates colon cancer cell growth through p38 mitogen-activated protein kinase signalling

OBJECTIVES

Heparin acts as an extracellular stimulus capable of activating major cell signalling pathways. Thus, we examined the putative mechanisms utilized by heparin to stimulate HT29, SW1116 and HCT116 colon cancer cell growth.

MATERIALS AND METHODS

Possible participation of the mitogen-activated protein kinase (MAPK) cascade on heparin-induced HT29, SW1116 and HCT116 colon cancer cell growth was evaluated using specific MAPK cascade inhibitors, Western blot analysis, real-time quantitative PCR and FACS apoptosis analysis.

RESULTS

Treatment with a highly specific p38 kinase inhibitor, SB203580, significantly (50-70%) inhibited heparin-induced colon cancer cell growth, demonstrating that p38 MAPK signalling is involved in their heparin-induced proliferative response. This was shown to be correlated with increased (up to 3-fold) phosphorylation of 181/182 threonine/tyrosine residues on p38 MAP kinase. Furthermore, heparin inhibited cyclin-dependent kinase inhibitor p21(WAF1/CIP1) and p53 tumour suppressor gene and protein expression up to 2-fold or 1.8-fold, respectively, and stimulated cyclin D1 expression up to 1.8-fold, in these cell lines through a p38-mediated mechanism. On the other hand, treatment with heparin did not appear to affect HT29, SW1116 and HCT116 cell levels of apoptosis.

CONCLUSIONS

This study demonstrates that an extracellular glycosaminoglycan, heparin, finely modulates expression of genes crucial to cell cycle regulation through specific activation of p38 MAP kinase to stimulate colon cancer cell growth.

Upregulated expression of periostin by hypoxia in non-small-cell lung cancer cells promotes cell survival via the Akt/PKB pathway

Periostin is a secreted protein and has been shown to be frequently overexpressed in various types of human cancers. We have previously reported that periostin potently promotes metastatic growth of colon cancer by augmenting cell survival. However, little is known about the functions of periostin in non-small-cell lung cancer. Here, we revealed that increased expression of periostin in non-small-cell lung cancer A549 cells was one kind of cellular responses to the stress of chemical-mimic hypoxia, and this effect could be regulated by hypoxia inducible growth factors, such as TGF-alpha and bFGF. We further demonstrated that RTK/PI3-K pathway activated by TGF-alpha and bFGF was evoked in upregulating the expression of periostin, and then periostin promoted the survival of A549 cells under hypoxic microenvironment via activation of Akt/PKB pathway. Therefore, periostin and the pathway that it involved might provide a target for lung cancer treatment.

Differential effects of serine proteases on the migration of normal and tumor cells: implications for tumor microenvironment

The supporting role of proteases in tumor progression and invasion is well known; however, the use of proteases as therapeutic agents has also been demonstrated. In this article, the authors report on the differential effects of exogenous serine proteases on the motility of tumor and normal cells. The treatment of normal and tumor cells with a single dose of pancreatic serine proteases, trypsin (TR) and chymotrypsin (CH), leads to a concentration-dependent response by cells, first accelerating and then slowing mobility. Tumor cells are 10 to 20 times more sensitive to exogenous TR/CH, suggesting that a single dose of proteases may cause discordant movements of normal and tumor cells within the tumor environment. The inhibitory effects of TR on cell motility are contradicted by thrombin (TH), particularly in the regulation of normal cells' migration. The purpose of this investigation was to ascertain the role of protease-activated receptors (PARs) in terms of normal and tumor cell motility. Duplicate treatments with proteases resulted in diminished mobility of both normal and tumor cells. Repeated application of TR and TH in 1-hour treatment intervals initially desensitizes cell surface PARs. However, cell surface PARs reappear regardless of subsequent protease treatments in both normal and tumor cells. The resensitization process is retarded in tumor cells when compared with normal cells. This is evidenced by lower expression of PARs as well as by their relocalization at the tumor cell surfaces. Under these conditions, normal cells remain responsive to exogenous proteases in terms of cell motility. Exogenous proteases do not modulate motility of repeatedly stimulated tumor cells, and consequently, the migration of tumor cells appears disconnected from the PAR signaling pathways. The use of activating peptides in lieu of the cognate proteases for a given PAR system indicated that proteases may act through additional targets not regulated by PAR signaling. We hypothesize that the divergent migration patterns of normal and tumor cells due to exposure to proteases is in part mediated by PARs. Thus, treatment with exogenous proteases may cause rearrangement of the tumor and stromal cells within the tumor microenvironment. Such topographical effects may lead to the inhibition of tumor progression and metastasis development.

The novel protein PTPIP51 is expressed in human keratinocyte carcinomas and their surrounding stroma

Background: The novel protein PTPIP51 (SwissProt accession code Q96SD6) is known to interact with two non-transmembrane protein-tyrosine phosphatases, PTP1B and TCPTP in vitro. Overexpression of the full-length protein induces apoptosis in HeLa and HEK293T cells (Lv et al. 2006). PTPIP51 shows a tissue-specific expression pattern and is associated with cellular differentiation and apoptosis in some mammalian tissues, especially in human follicular and interfollicular epidermis. PTPIP51 protein is expressed in all suprabasal layers of normal epidermis, whereas the basal layer contains PTPIP51 mRNA only but lacks the protein. Objectives: The expression of PTPIP51 was investigated in keratinocyte carcinomas, that is human basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs) as well as Bowen's disease (BD) and keratoacanthomas (KAs) on a transcriptional (mRNA) and translational (immunohistochemical) level. Methods: Formalin-fixed, paraffin-embedded sections of BCCs, SCCs, KAs and BD, respectively, were analysed by RT-PCR, as well as immunohistochemistry and subsequent fluorescence microscopy. PTPIP51-positive cells of the tumour and the surrounding stroma were identified on the basis of specific morphological features by means of H & E staining. To obtain further information about a putative function of PTPIP51, a possible association of PTPIP51 with apoptotic cells, as well as an assumed negative correlation with proliferating cells was investigated by means of an in-situ TUNEL assay and Ki67/MIB-1 antigen staining, respectively. Co-immunostainings with PTPIP51 were performed for the following antigens: TCPTP, PTP1B and β-catenin. Results: PTPIP51-expression was detected in BCCs and SCCs of the skin, as well as in KAs and BD. Both types of keratinocyte carcinoma revealed a specific localization pattern of PTPIP51 in malignant keratinocytes. Whereas PTPIP51 -positive cells of BCC were found to form two cluster types with a different subcellular localization of the protein, i.e. cytoplasmic and nuclear or predominantly membranous, investigation of SCC revealed a meshwork-like appearance of PTPIP51-positive malignant keratinocytes, created by a mainly membranous localization. BD and KA resembled the findings of PTPIP51-expression in SCC. Furthermore, we observed a partial co-localization of PTP1B and PTPIP51 in BCC. SCC and BCC showed a co-expression and partial co-localization of PTPIP51 with β-catenin. Some PTPIP51-positive cells were found to undergo apoptosis. PTPIP51 was also expressed in cells comprising the surrounding stromal microenvironment. This was particularly noticed for endothelial cells lining peritumoural vessels as well as for infiltrating cells of both, the innate and the adaptive immune system. Conclusions: The results showed a distinct mainly membranous expression pattern of PTPIP51 in BCCs and SCCs. Since PTPIP51 was also detected in the peritumoural tissue, the protein may play a crucial role in keratinocyte tumour development.

Inhibition of cyclooxygenase-2 suppresses the invasiveness of oral squamous cell carcinoma cell lines via down-regulation of matrix metalloproteinase-2 production and activation

Increased cyclooxygenase (COX-2) expression in tumors is known to be correlated with tumor invasion, angiogenesis, resistance to apoptosis, and suppression of host immunity. We previously reported that the invasiveness of human oral squamous cell carcinoma (OSCC) cell lines NA and HSC-4 was suppressed by treatment with either NS-398, a selective COX-2 inhibitor, or COX-2 antisense oligonucleotide (AS). In the present study, to explore the effects of COX-2 inhibition on the interaction between cancer cells and fibroblasts, we examined the effects of these anti-COX-2 reagents on the expression of matrix metalloproteinases (MMPs) in fibroblast cell lines WI-38 and MRC-5. Western blotting and enzyme-linked immunosorbent assay revealed that NS-398 and COX-2 AS down-regulated the expression and secretion of MMP-2 and the tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) in human fibroblast cell lines. Furthermore, invasion activity of OSCC cells was down-regulated by the addition of culture supernatant from fibroblasts treated with anti-COX-2 reagents in a Matrigel invasion assay. These results suggest that selective COX-2 inhibition suppresses the invasion activity of OSCC cells via down-regulation of an MMP-2-activating mechanism involving TIMP-2 and production of the MMP-2 protein by an interaction between cancer cells and stromal fibroblasts. Genetic or pharmacological inhibition of COX-2 may therefore be a beneficial strategy in the treatment of OSCC.

Control of tumourigenesis by the Scribble/Dlg/Lgl polarity module

The neoplastic tumour suppressors, Scribble, Dlg and Lgl, originally discovered in the vinegar fly Drosophila melanogaster, are currently being actively studied for their potential role in mammalian tumourigenesis. In Drosophila, these tumour suppressors function in a common genetic pathway to regulate apicobasal cell polarity and also play important roles in the control of cell proliferation, survival, differentiation and in cell migration/invasion. The precise mechanism by which Scribble, Dlg and Lgl function is not clear; however, they have been implicated in the regulation of signalling pathways, vesicle trafficking and in the Myosin II-actin cytoskeleton. We review the evidence for the involvement of Scribble, Dlg, and Lgl in cancer, and how the various functions ascribed to these tumour suppressors in Drosophila and mammalian systems may impact on the process of tumourigenesis.

Cancer cells suppress p53 in adjacent fibroblasts

The p53 tumor suppressor serves as a crucial barrier against cancer development. In tumor cells and their progenitors, p53 suppresses cancer in a cell-autonomous manner. However, p53 also possesses non-cell-autonomous activities. For example, p53 of stromal fibroblasts can modulate the spectrum of proteins secreted by these cells, rendering their microenvironment less supportive of the survival and spread of adjacent tumor cells. We now report that epithelial tumor cells can suppress p53 induction in neighboring fibroblasts, an effect reproducible by tumor cell-conditioned medium. The ability to suppress fibroblast p53 activation is acquired by epithelial cells in the course of neoplastic transformation. Specifically, stable transduction of immortalized epithelial cells by mutant H-Ras and p53-specific short inhibitory RNA endows them with the ability to quench fibroblast p53 induction. Importantly, human cancer-associated fibroblasts are more susceptible to this suppression than normal fibroblasts. These findings underscore a mechanism whereby epithelial cancer cells may overcome the non-cell-autonomous tumor suppressor function of p53 in stromal fibroblasts.

Keratinocyte expression of MMP3 enhances differentiation and prevents tumor establishment

Matrix metalloproteinase (MMP)-3 is induced by multiple cell types in the skin during processes involved in both normal and pathological tissue remodeling. We previously demonstrated that MMP3-null animals have an increased sensitivity to the development of squamous cell carcinoma, suggesting that overall, MMP3 has a protective role in squamous cell carcinoma. However, not all cellular responses affected by a loss of MMP3 are tumor-protective, and tumor expression of MMP3 is co-incident with an invasive tumor phenotype. Transgenic mice were generated with MMP3 targeted to keratinocytes to examine the biological role of tumor-produced MMP3. Overexpression of MMP3 reduced tumor multiplicity in response to chemically induced squamous cell carcinoma. Vascular density was increased with MMP3 overexpression; however, other cellular processes, including tumor growth and leukocyte infiltration, were unaffected. In accordance with the change in tumor multiplicity, SP-1 murine papilloma cell lines that were generated to stably express MMP3 lost the capacity to establish palpable tumors following orthotopic injection into immunocompromised mice. Analysis of epidermal biopsies taken at 1 to 2 weeks postinjection revealed that these MMP3-expressing Sp-1 lines had reduced levels of proliferation and pronounced differentiation. These same cells demonstrated an increased ability to differentiate in vitro, an effect that was inhibited by broad-spectrum MMP and selective MMP3 inhibition. These studies suggest that keratinocyte expression of MMP3 promotes cellular differentiation, impeding tumor establishment during tumorigenesis.

Three-dimensional context regulation of metastasis

Tumor progression ensues within a three-dimensional microenvironment that consists of cellular and non-cellular components. The extracellular matrix (ECM) and hypoxia are two non-cellular components that potently influence metastasis. ECM remodeling and collagen cross-linking stiffen the tissue stroma to promote transformation, tumor growth, motility and invasion, enhance cancer cell survival, enable metastatic dissemination, and facilitate the establishment of tumor cells at distant sites. Matrix degradation can additionally promote malignant progression and metastasis. Tumor hypoxia is functionally linked to altered stromal-epithelial interactions. Hypoxia additionally induces the expression of pro-migratory, survival and invasion genes, and up-regulates expression of ECM components and modifying enzymes, to enhance tumor progression and metastasis. Synergistic interactions between matrix remodeling and tumor hypoxia influence common mechanisms that maximize tumor progression and cooperate to drive metastasis. Thus, clarifying the molecular pathways by which ECM remodeling and tumor hypoxia intersect to promote tumor progression should identify novel therapeutic targets.

Beyond the oncogene paradigm: understanding complexity in cancerogenesis

In the past decades, an enormous amount of precious information has been collected about molecular and genetic characteristics of cancer. This knowledge is mainly based on a reductionistic approach, meanwhile cancer is widely recognized to be a 'system biology disease'. The behavior of complex physiological processes cannot be understood simply by knowing how the parts work in isolation. There is not solely a matter how to integrate all available knowledge in such a way that we can still deal with complexity, but we must be aware that a deeply transformation of the currently accepted oncologic paradigm is urgently needed. We have to think in terms of biological networks: understanding of complex functions may in fact be impossible without taking into consideration influences (rules and constraints) outside of the genome. Systems Biology involves connecting experimental unsupervised multivariate data to mathematical and computational approach than can simulate biologic systems for hypothesis testing or that can account for what it is not known from high-throughput data sets. Metabolomics could establish the requested link between genotype and phenotype, providing informations that ensure an integrated understanding of pathogenic mechanisms and metabolic phenotypes and provide a screening tool for new targeted drug.

Extracellular matrix signature identifies breast cancer subgroups with different clinical outcome

Prediction of the clinical outcome of breast cancer is multi-faceted and challenging. There is growing evidence that the complexity of the tumour micro-environment, consisting of several cell types and a complex mixture of proteins, plays an important role in development, progression, and response to therapy. In the current study, we investigated whether invasive breast tumours can be classified on the basis of the expression of extracellular matrix (ECM) components and whether such classification is representative of different clinical outcomes. We first examined the matrix composition of 28 primary breast carcinomas by morphology and gene expression profiling using 22K oligonucleotide Agilent microarrays. Hierarchical clustering of the gene expression profile of 278 ECM-related genes derived from the literature divided the tumours into four main groups (ECM1-4). A set of selected differentially expressed genes was validated by immunohistochemistry. The robustness of the ECM classification was confirmed by studying the four ECM groups in a previously published gene expression data set of 114 early-stage primary breast carcinomas profiled using cDNA arrays. Univariate survival analysis showed significant differences in clinical outcome among the various ECM subclasses. One set of tumours, designated ECM4, had a favourable outcome and was defined by the overexpression of a set of protease inhibitors belonging to the serpin family, while tumours with an ECM1 signature had a poorer prognosis and showed high expression of integrins and metallopeptidases, and low expression of several laminin chains. Furthermore, we identified three surrogate markers of ECM1 tumours: MARCO, PUNC, and SPARC, whose expression levels were associated with breast cancer survival and risk of recurrence. Our findings suggest that primary breast tumours can be classified based upon ECM composition and that this classification provides relevant information on the biology of breast carcinomas, further supporting the hypothesis that clinical outcome is strongly related to stromal characteristics.

Microenvironmental regulation of cancer development

Numerous studies have demonstrated that the tumor microenvironment not only responds to and supports carcinogenesis, but also actively contributes to tumor initiation, progression, and metastasis. During tumor progression all cells composing the tumor undergo phenotypic and epigenetic changes. Paracrine signaling between epithelial and stromal cells is important for the regulation of the proliferation, invasive, angiogenic, and metastatic behavior of cancer cells. Better understanding the molecular mechanisms by which stromal cells exert these effects may open up new venues for cancer therapeutic and preventative interventions.

The functional interplay between EGFR overexpression, hTERT activation, and p53 mutation in esophageal epithelial cells with activation of stromal fibroblasts induces tumor development, invasion, and differentiation

Esophageal cancer is a prototypic squamous cell cancer that carries a poor prognosis, primarily due to presentation at advanced stages. We used human esophageal epithelial cells as a platform to recapitulate esophageal squamous cell cancer, thereby providing insights into the molecular pathogenesis of squamous cell cancers in general. This was achieved through the retroviral-mediated transduction into normal, primary human esophageal epithelial cells of epidermal growth factor receptor (EGFR), the catalytic subunit of human telomerase (hTERT), and p53(R175H), genes that are frequently altered in human esophageal squamous cell cancer. These cells demonstrated increased migration and invasion when compared with control cells. When these genetically altered cells were placed within the in vivo-like context of an organotypic three-dimensional (3D) culture system, the cells formed a high-grade dysplastic epithelium with malignant cells invading into the stromal extracellular matrix (ECM). The invasive phenotype was in part modulated by the activation of matrix metalloproteinase-9 (MMP-9). Using pharmacological and genetic approaches to decrease MMP-9, invasion into the underlying ECM could be suppressed partially. In addition, tumor differentiation was influenced by the type of fibroblasts within the stromal ECM. To that end, fetal esophageal fibroblasts fostered a microenvironment conducive to poorly differentiated invading tumor cells, whereas fetal skin fibroblasts supported a well-differentiated tumor as illustrated by keratin "pearl" formation, a hallmark feature of well-differentiated squamous cell cancers. When inducible AKT was introduced into fetal skin esophageal fibroblasts, a more invasive, less-differentiated esophageal cancer phenotype was achieved. Invasion into the stromal ECM was attenuated by genetic knockdown of AKT1 as well as AKT2. Taken together, alterations in key oncogenes and tumor suppressor genes in esophageal epithelial cells, the composition and activation of fibroblasts, and the components of the ECM conspire to regulate the physical and biological properties of the stroma.

Direct visualization of macrophage-assisted tumor cell intravasation in mammary tumors

Although the presence of macrophages in tumors has been correlated with poor prognosis, until now there was no direct observation of how macrophages are involved in hematogenous metastasis. In this study, we use multiphoton microscopy to show, for the first time, that tumor cell intravasation occurs in association with perivascular macrophages in mammary tumors. Furthermore, we show that perivascular macrophages of the mammary tumor are associated with tumor cell intravasation in the absence of local angiogenesis. These results show that the interaction between macrophages and tumor cells lying in close proximity defines a microenvironment that is directly involved in the intravasation of cancer cells in mammary tumors.

The involvement of IL-1 in tumorigenesis, tumor invasiveness, metastasis and tumor-host interactions

Interleukin-1 (IL-1) includes a family of closely related genes; the two major agonistic proteins, IL-1alpha and IL-1beta, are pleiotropic and affect mainly inflammation, immunity and hemopoiesis. The IL-1Ra antagonist is a physiological inhibitor of pre-formed IL-1. Recombinant IL-1alpha and IL-1beta bind to the same receptors and induce the same biological functions. As such, the IL-1 molecules have been considered identical in normal homeostasis and in disease. However, the IL-1 molecules differ in their compartmentalization within the producing cell or the microenvironment. Thus, IL-1beta is solely active in its secreted form, whereas IL-1alpha is mainly active in cell-associated forms (intracellular precursor and membrane-bound IL-1alpha) and only rarely as a secreted cytokine, as it is secreted only in a limited manner. IL-1 is abundant at tumor sites, where it may affect the process of carcinogenesis, tumor growth and invasiveness and also the patterns of tumor-host interactions. Here, we review the effects of microenvironment- and tumor cell-derived IL-1 on malignant processes in experimental tumor models and in cancer patients. We propose that membrane-associated IL-1alpha expressed on malignant cells stimulates anti-tumor immunity, while secretable IL-1beta, derived from the microenvironment or the malignant cells, activates inflammation that promotes invasiveness and also induces tumor-mediated suppression. Inhibition of the function of IL-1 by the IL-1Ra, reduces tumor invasiveness and alleviates tumor-mediated suppression, pointing to its feasibility in cancer therapy. Differential manipulation of IL-1alpha and IL-1beta in malignant cells or in the tumor's microenvironment can open new avenues for using IL-1 in cancer therapy.

The chemokine growth-regulated oncogene 1 (Gro-1) links RAS signaling to the senescence of stromal fibroblasts and ovarian tumorigenesis

Epithelial-stromal interactions play a critical role in tumor initiation and progression; cancer-associated stroma, but not normal stroma, is known to be tumor-promoting. However, the molecular signal used by epithelial cancer cells to reprogram normal stroma to a tumorigenic stroma is not known. Here, we present evidence to suggest that the chemokine growth-regulated oncogene 1 (Gro-1) may be one such signaling molecule. We showed that the expression of Gro-1 is activated by RAS and is vital for cell survival and the malignant transformation of ovarian epithelial cells. Surprisingly, we found that Gro-1 is a potent inducer of senescence in stromal fibroblasts and that this effect depends on functional p53. Senescent fibroblasts induced by Gro-1 can promote tumor growth whereas abrogation of senescence through immortalization results in loss of such tumor promoting activity. We also demonstrated that stromal fibroblasts adjacent to epithelial cancer cells are senescent in human ovarian cancer specimens and in heterografts from RAS-transformed human ovarian epithelial cells and ovarian cancer cells. Moreover, Gro-1 was expressed at significantly higher amounts in ovarian cancer than in normal tissues and was higher in serum samples from women with ovarian cancer than in serum from women without ovarian cancer. These findings provide strong evidence that RAS-induced Gro-1 can reprogram the stromal microenvironment through the induction of senescence of fibroblasts and thus can promote tumorigenesis. Therefore, Gro-1 may be a therapeutic target as well as a diagnostic marker in ovarian cancer.

The fibroblastic coconspirator in cancer progression

A remarkable change has occurred in the thinking about epithelial-derived cancer in recent years: From almost entirely focusing on oncogenes and tumor suppressor genes has come the realization that the tumor microenvironment is a coconspirator in the carcinogenic process. Many types of stromal cells, including fibroblasts, adipocytes, macrophages, mast cells, and cells of the vascular system, are crucial contributors to epithelial carcinogenesis. Here, we focus on the fibroblast's role in cancer progression and the molecules involved in the communications between the fibroblasts and the cancer cells, including fibroblast secreted protein 1 (FSP-1 or S100A4), transforming growth factor beta (TGF-beta), the chemokine CXCL-12 (stromal derived factor 1 alpha, SDF-1alpha), type I collagen, and matrix metalloproteinase 13 (MMP-13).

S100A8 and S100A9 in inflammation and cancer

Calprotectin (S100A8/A9), a heterodimer of the two calcium-binding proteins S100A8 and S100A9, was originally discovered as immunogenic protein expressed and secreted by neutrophils. Subsequently, it has emerged as important pro-inflammatory mediator in acute and chronic inflammation. More recently, increased S100A8 and S100A9 levels were also detected in various human cancers, presenting abundant expression in neoplastic tumor cells as well as infiltrating immune cells. Although, many possible functions have been proposed for S100A8/A9, its biological role still remains to be defined. Altogether, its expression and potential cytokine-like function in inflammation and in cancer suggests that S100A8/A9 may play a key role in inflammation-associated cancer.

Role of PSF-TFE3 oncoprotein in the development of papillary renal cell carcinomas

A subset of papillary renal cell carcinomas (RCC) is characterized by the expression of a TFE3 fusion protein, where the fusion partner can be any of the several proteins identified so far such as PSF (PTB associated splicing factor), NonO, PRCC, CLTC and ASPL. These proteins result from chromosomal translocations involving the TFE3 gene located on the X chromosome. Our present study documents the central role of PSF-TFE3 in oncogenic transformation. We show that the inhibition of PSF-TFE3 expression through siRNA or shRNA leads to impaired growth, proliferation, invasion potential and long-term survival of UOK-145 papillary renal carcinoma-derived cells, which endogenously express PSF-TFE3. The oncogenic potential of PSF-TFE3 became evident by stable expression of PSF-TFE3 in NIH-3T3 mouse fibroblast cells, which leads to the acquisition of anchorage-independent growth as revealed by soft agar assay. In addition, the expression of PSF-TFE3 in normal renal proximal tubular epithelial cells from where such tumors originate leads to dedifferentiation and loss of some key functional proteins, which may reflect an initial step in the multistep process of tumor development. This suggests that the expression of PSF-TFE3 in renal epithelial cells plays an important role in the initiation and maintenance of oncogenic phenotype in papillary RCC.

Collagen-based co-culture for invasive study on cancer cells-fibroblasts interaction

The roles of tumor stroma in carcinogenesis are still unclear. This study was aimed at designing an in vitro model for investigating the effects of stromal fibroblasts in the invasive growth of squamous cell carcinoma. Using two cancer cell lines, we performed three-dimensional co-culture with dermal equivalents to evaluate the effects of fibroblasts in cancer invasion. In vitro models for cellular interaction study were designed as follows: a collagen gel-based direct co-culture model (C-Dr) and a collagen gel-based indirect co-culture model (C-In). The invasive growth was found only in the dermal equivalents with fibroblasts. MMP-2 activity could be induced by direct contact between cancer cells and stromal fibroblasts. Cathepsin D was also highly expressed when co-cultured with cancer cells and fibroblasts. The present study demonstrated that the presence of fibroblasts is essential in cancer invasion and that collagen gel-based co-culture models might be useful for invasive study.

Cyclophilin A is overexpressed in human pancreatic cancer cells and stimulates cell proliferation through CD147

BACKGROUND

Although overexpression of cyclophilin A (CypA) is associated with several types of cancer, its role in pancreatic cancer has not been studied. In this study the expression of CypA and its receptor CD147 on pancreatic cancer was determined as well as the effect of exogenous CypA on pancreatic cancer cell proliferation.

METHODS

The expression of CypA and CD147 in human pancreatic cancer cell lines and tissues was determined with real-time reverse transcriptase polymerase chain reaction (RT-PCR), Western blot, and immunostaining. Cell proliferation in response to CypA was performed by [3H]thymidine incorporation assay. Phosphorylation of MAPK and cytokine secretion profiles in pancreatic cancer cells were determined by using the Bio-Plex phosphoprotein assay and cytokine assay.

RESULTS

Pancreatic cancer cell lines expressed significantly higher levels of CypA and CD147 than normal human pancreatic ductal epithelium (HPDE) cells. Expression of CypA and CD147 was also substantially higher in human pancreatic adenocarcinoma tissues than those in normal pancreatic tissues. Addition of exogenous CypA significantly stimulated pancreatic cancer cell proliferation in a dose-dependent manner and this effect was effectively blocked by pretreatment with anti-CD147 antibody. In addition, CypA activated ERK1/2 and p38 MAPK signaling pathways and increased the secretion of 2 key cytokines IL-5 and IL-17 in Panc-1 cells.

CONCLUSIONS

The expression of CypA and CD147 was significantly increased in both pancreatic cancer cell lines and tissues. Exogenous CypA promotes pancreatic cancer cell growth, which may be mediated through the interaction with CD147 and the activation of ERK1/2 and p38 MAPKs.

Immunoprofile of reactive salivary myoepithelial cells in intraductal areas of carcinoma ex-pleomorphic adenoma

The myoepithelial cell (MC) is a component of various secretory glands, including salivary glands. Besides its function, a tumor suppressor and a tumor facilitating functions have been attributed to this cell. We investigated the immunoprofile of benign MC in intraductal areas of carcinoma ex-pleomorphic adenoma (CXPA), comparing them with the MC in duct-like areas of pleomorphic adenoma, origin of the malignant tumor. Antibodies against myoepithelial markers-CK14, alpha-SMA, calponin, P63, CD10, and D2-40-plus laminin and maspin was applied in four selected cases of intracapsular and minimal invasive CXPA with only luminal differentiation presenting areas of intraductal carcinoma. The immunohistochemical reactions of all the antibodies showed stronger staining in benign MC surrounding the malignant epithelial cells than in benign MC in duct-like areas of pleomorphic adenoma, thus revealing that in the malignization process the benign MC become differentiated and produce important proteins related to the tumor suppressor function.

Pleiotropic effects of FGFR1 on cell proliferation, survival, and migration in a 3D mammary epithelial cell model

Members of the fibroblast growth factor (FGF) family and the FGF receptors (FGFRs) have been implicated in mediating various aspects of mammary gland development and transformation. To elucidate the molecular mechanisms of FGFR1 action in a context that mimics polarized epithelial cells, we have developed an in vitro three-dimensional HC11 mouse mammary epithelial cell culture model expressing a drug-inducible FGFR1 (iFGFR1). Using this conditional model, iFGFR1 activation in these growth-arrested and polarized mammary acini initially led to reinitiation of cell proliferation, increased survival of luminal cells, and loss of cell polarity, resulting in the disruption of acinar structures characterized by the absence of an empty lumen. iFGFR1 activation also resulted in a gain of invasive properties and the induction of matrix metalloproteinase 3 (MMP-3), causing the cleavage of E-cadherin and increased expression of smooth muscle actin and vimentin. The addition of a pan MMP inhibitor abolished these phenotypes but did not prevent the effects of iFGFR1 on cell proliferation or survival.

MUC1 Mediates Transendothelial Migration in vitro by Ligating Endothelial Cell ICAM-1

MUC1 is a transmembrane glycoprotein expressed by normal breast epithelium and virtually all breast cancers. MUC1 is normally restricted to the apical surface of epithelia and loss of this polarized distribution in breast carcinomas is associated with lymph node metastasis. Our previous work found that MUC1 can bind intercellular adhesion molecule-1 (ICAM-1), mediating adhesion of breast cancer cells to a simulated blood vessel wall, and also triggering a calcium-based signal in the MUC1-bearing cells. It is possible that the depolarized membrane distribution of MUC1 in breast carcinomas may facilitate interactions with stromal/endothelial ICAM-1 leading to adhesion and subsequent migration through the vessel wall. In the current study, we provide evidence that ICAM-1 can influence the migration of cells that express endogenous or transfected MUC1. Migration across a gelatin-coated Transwell membrane could be increased in a step-wise manner by the sequential addition of ICAM-1-expressing cells (endothelial cells and fibroblasts), and ICAM-1-inducing inflammatory cytokines (tumour necrosis factor-alpha and interleukin-1 beta). Antibodies against MUC1 or ICAM-1, but not a control antibody, could abrogate migratory increases. Cells that did not express MUC1 were unresponsive to ICAM-1. Our current findings build on our earlier work, by suggesting that the end result of the MUC1/ICAM-1-mediated cell-cell adhesion and calcium-based signal is migration. This has implications for the exit of circulating tumour cells from the vasculature, as well as tumour cell migration through fibroblast-containing stroma underlying the endothelial wall.

Do myoepithelial cells hold the key for breast tumor progression?

Mammary myoepithelial cells have been a neglected facet of breast cancer biology, largely ignored since they have been considered to be less important for tumorigenesis than luminal epithelial cells from which most of breast carcinomas are thought to arise. In recent years as our knowledge of stem cell biology and the cellular microenvironment has been increasing, myoepithelial cells are slowly starting to gain more attention. Emerging data raise the hypothesis whether myoepithelial cells play a key role in breast tumor progression by regulating the in situ to invasive carcinoma transition and that myoepithelial cells are part of the mammary stem cell niche. Paracrine interactions between myoepithelial and luminal epithelial cells are known to be important for regulation of cell cycle progression, establishing epithelial cell polarity, and inhibiting cell migration and invasion. Based on these functions, normal mammary myoepithelial cells have been called "natural tumor suppressors." However, during tumor progression myoepithelial cells seem to loose these properties, and eventually this cell population diminishes as tumors become invasive. Better understanding of myoepithelial cell function and their role in tumor progression may lead to their exploitation for cancer therapeutic and preventative measures.

Soluble mediators of inflammation during tumor development

Tissues maintain homeostasis by monitoring and responding to varied physical interactions between cells and their microenvironment. In situations where acute tissue damage occurs, such as wounding, pathogenic assault, or toxic exposure, regulatory circuits that monitor tissue homeostasis are rapidly engaged to initiate tissue repair by regulating cell polarity, proliferation and death, matrix metabolism, inflammation, and vascular and lymphatic function. The critical feature of regulating these acute responses is the innate ability to discriminate between homeostatic versus damaged tissue states and engage or disengage regulatory machinery as appropriate; thus, a major distinction between acute versus chronic disease is the altered ability to appropriately activate and?or inactivate reparative regulatory programs. Since cancer is a chronic disease characterized by altered cell polarity, enhanced cell survival, inflammation, increased matrix metabolism, and enhanced vascular and lymphatic function, considerable attention is now focused on understanding the cellular and molecular mechanisms regulating these responsive pathways. Since chemoattractant cytokines are important mediators of leukocyte recruitment following acute tissue stress, and demonstrate altered characteristics of expression and activation in chronically inflamed tissue, they have been implicated as key regulators of inflammation and angiogenesis during cancer development. This chapter focuses on the clinical and experimental data implicating proinflammatory cytokines and chemokines as important potentiators of carcinogenesis.

Harnessing host immune responses to preneoplasia: promise and challenges

Preneoplastic lesions are more common than clinical cancer and define a population at increased risk for the development of malignancy. Recent studies suggest that the immune system has the capacity to recognize these lesions, and enrichment of preneoplasia-specific immune effectors can be detected in the tumor bed of some preneoplastic lesions such as monoclonal gammopathies. Here, I discuss the promise and challenges of harnessing the immune response against preneoplasia. Approaches to boost the natural host response to these lesions may have a major impact on reducing net cancer burden.

TGF-beta and the Smad signaling pathway support transcriptomic reprogramming during epithelial-mesenchymal cell transition

Epithelial-mesenchymal transition (EMT) contributes to normal tissue patterning and carcinoma invasiveness. We show that transforming growth factor (TGF)-beta/activin members, but not bone morphogenetic protein (BMP) members, can induce EMT in normal human and mouse epithelial cells. EMT correlates with the ability of these ligands to induce growth arrest. Ectopic expression of all type I receptors of the TGF-beta superfamily establishes that TGF-beta but not BMP pathways can elicit EMT. Ectopic Smad2 or Smad3 together with Smad4 enhanced, whereas dominant-negative forms of Smad2, Smad3, or Smad4, and wild-type inhibitory Smad7, blocked TGF-beta-induced EMT. Transcriptomic analysis of EMT kinetics identified novel TGF-beta target genes with ligand-specific responses. Using a TGF-beta type I receptor that cannot activate Smads nor induce EMT, we found that Smad signaling is critical for regulation of all tested gene targets during EMT. One such gene, Id2, whose expression is repressed by TGF-beta1 but induced by BMP-7 is critical for regulation of at least one important myoepithelial marker, alpha-smooth muscle actin, during EMT. Thus, based on ligand-specific responsiveness and evolutionary conservation of the gene expression patterns, we begin deciphering a genetic network downstream of TGF-beta and predict functional links to the control of cell proliferation and EMT.

Chemokine receptor CXCR4-β1 integrin axis mediates tumorigenesis of osteosarcoma HOS cells

It is known that β1 integrins mediate the migratory response of cells to chemokine stimulation. Also, both β1 integrins and chemokines have roles in tumor development. In the present study, the β1 integrin-chemokine axis is assessed using human osteosarcoma (HOS) transfectant cells expressing the CXCR4 receptor for chemokine SDF-1 (CXCL12). We first identified in vitro the specific β1 integrins that mediated the migratory response to SDF-1 stimulation. Results showed that on collagen type I and laminin, the chemotactic response to SDF-1 was predominantly mediated by α2β1 integrin. On fibronectin, SDF-1-stimulated chemotaxis involved both α4β1 and α5β1 integrins. A comparison of the transfectant clones expressing CXCR4 at low, intermediate, and high levels and the control transfectant revealed that the transfectant clones migratory response in vitro and their ability to form tumors in vivo was related to their levels of CXCR4 expression. In addition, treatment by injection with mAbs to CXCR4, integrin α2β1, or integrin α5β1 effectively inhibited the growth of HOS-CXCR4 transfectant cells in vivo. Therefore, our results show that the β1 integrins that mediated the migratory response were also functionally linked to the enhanced tumor growth of CXCR4-expressing HOS transfectant cells.Key words: integrins, chemokines, chemotaxis, osteosarcoma, tumorigenesis.

Microdissection and SAGE as a combined tool to reveal gene expression in ductal carcinoma in situ of the breast

The interplay between cancer cells and the normal surrounding tissue is believed to influence the biological behavior of the tumor. However, the presence of multiple cell types within the prelevated tumor specimen may attenuate changes that occur specifically in the malignant cells within their microenvironment. To study gene expression of the malignant cells in situ, we used a new microdissection method to separate ductal carcinoma in situ (DCIS) cells from the surrounding stroma, immunological infiltrates, and endothelial cells. We applied an adapted microSAGE protocol, without total mRNA amplification, to study their gene expression profile. Three thousand two hundred one different transcripts were identified in a total of 29 534 observed tags. Of these unique tags, 88.3% matched known GenBank sequences and 11.7% represented unknown transcripts. As compared to a total DCIS SAGE library, microdissection combined with SAGE revealed additional genes expressed only in normal surrounding, probably stromal, cells and not or significantly less in DCIS tumor cells. This study demonstrates that microdissection can be combined with SAGE as a tool to study transcriptomes. This approach provides important new information on differential gene expression both in tumor cells and normal surrounding tissue. Several of the observed differences indeed disappear when the total tumor mass is analyzed.

Latent effects of fibronectin, alpha5beta1 integrin, alphaVbeta5 integrin and the cytoskeleton regulate pancreatic carcinoma cell IL-8 secretion

Interactions between tumour cells and the microenvironment are increasingly recognised to have an influence on cancer progression. In pancreatic carcinoma, a highly desmoplastic stroma with abnormal extracellular matrix (ECM) protein and interleukin-8 (IL-8) expression is seen. To investigate whether the ECM may further contribute to abnormalities in the microenvironment by influencing IL-8 secretion, we cultured the Mia PaCa2 pancreatic carcinoma cell line on fibronectin. This resulted in a dose-dependent increase in IL-8 secretion, which was RGD dependent and accompanied by cell spreading and proliferation. The role of spreading was assessed by disruption of the cytoskeleton with cytochalasin D, resulting in a large increase in IL-8 secretion, which was reduced from 31- to 24-fold by fibronectin. This remarkable response was associated with inhibition of spreading and proliferation and represents a novel cytoskeletal function. To investigate whether it could be accounted for by the loss of integrin-mediated signalling, the expressed α5β1, αVβ5 and α3β1 integrins were inhibited. α5β1 inhibition prevented spreading and proliferation but produced a much smaller rise in IL-8 secretion than cytochalasin D. αVβ5 inhibition alone had only minor effects but when inhibited in combination with α5β1 completely abolished the response to fibronectin. These results reveal latent stimulatory effects of the αVβ5 integrin on IL-8 secretion and suggest that integrin crosstalk may limit the induction of IL-8 secretion by fibronectin. However, the magnitude of IL-8 secretion induced by cytochalasin cannot be accounted for by integrin signalling and may reflect the influence of another signalling pathway or a novel, intrinsic cytoskeletal function.

The tension mounts: mechanics meets morphogenesis and malignancy

The tissue microenvironment regulates mammary gland development and tissue homeostasis through soluble, insoluble and cellular cues that operate within the three dimensional architecture of the gland. Disruption of these critical cues and loss of tissue architecture characterize breast tumors. The developing and lactating mammary gland are also subject to a plethora of tensional forces that shape the morphology of the gland and orchestrate its functionally differentiated state. Moreover, malignant transformation of the breast is associated with dramatic changes in gland tension that include elevated compression forces, high tensional resistance stresses and increased extracellular matrix stiffness. Chronically increased mammary gland tension may influence tumor growth, perturb tissue morphogenesis, facilitate tumor invasion, and alter tumor survival and treatment responsiveness. Because mammary tissue differentiation is compromised by high mechanical force and transformed cells exhibit altered mechanoresponsiveness, malignant transformation of the breast may be functionally linked to perturbed tensional-homeostasis. Accordingly, it will be important to define the role of tensional force in mammary gland development and tumorigenesis. Additionally, it will be critical to identify the key molecular elements regulating tensional-homeostasis of the mammary gland and thereafter to characterize their associated mechanotransduction pathways.

Computational Approach to Systems Biology: From Fraction to Integration and Beyond

Systems biology is an approach to understanding the workings of whole biological systems. The various methods used for systems analyses range from experimental to computational. In this paper, we describe basic concepts of systems biology, modeling challenges that arise from the massively parallel interaction among components in biological systems, and what lies beyond integration of modular knowledge.

NF-kappaB functions as a tumour promoter in inflammation-associated cancer

The causes of sporadic human cancer are seldom recognized, but it is estimated that carcinogen exposure and chronic inflammation are two important underlying conditions for tumour development, the latter accounting for approximately 20% of human cancer. Whereas the causal relationship between carcinogen exposure and cancer has been intensely investigated, the molecular and cellular mechanisms linking chronic inflammation to tumorigenesis remain largely unresolved. We proposed that activation of the nuclear factor kappaB (NF-kappaB), a hallmark of inflammatory responses that is frequently detected in tumours, may constitute a missing link between inflammation and cancer. To test this hypothesis, we studied the Mdr2-knockout mouse strain, which spontaneously develops cholestatic hepatitis followed by hepatocellular carcinoma, a prototype of inflammation-associated cancer. We monitored hepatitis and cancer progression in Mdr2-knockout mice, and here we show that the inflammatory process triggers hepatocyte NF-kappaB through upregulation of tumour-necrosis factor-alpha (TNFalpha) in adjacent endothelial and inflammatory cells. Switching off NF-kappaB in mice from birth to seven months of age, using a hepatocyte-specific inducible IkappaB-super-repressor transgene, had no effect on the course of hepatitis, nor did it affect early phases of hepatocyte transformation. By contrast, suppressing NF-kappaB inhibition through anti-TNFalpha treatment or induction of IkappaB-super-repressor in later stages of tumour development resulted in apoptosis of transformed hepatocytes and failure to progress to hepatocellular carcinoma. Our studies thus indicate that NF-kappaB is essential for promoting inflammation-associated cancer, and is therefore a potential target for cancer prevention in chronic inflammatory diseases.