Aberrant type I and type III collagen gene expression in human breast cancer in vivo

A novel 3D in vitro metastasis model elucidates differential invasive strategies during and after breaching basement membrane

Invasive breast cancer and other tumors of epithelial origin must breach a layer of basement membrane (BM) that surrounds the primary tumor before invading into the adjacent extracellular matrix. To analyze invasive strategies of breast cancer cells during BM breaching and subsequent invasion into a collagen I-rich extracellular matrix (ECM), we developed a physiologically relevant 3D in vitro model that recreates the architecture of a solid tumor with an intact, degradable, cell-assembled BM layer embedded in a collagen I environment. Using this model we demonstrate that while the BM layer fully prevents dissemination of non-malignant cells, cancer cells are capable of breaching it and invading into the surrounding collagen, indicating that the developed system recreates a hallmark of invasive disease. We demonstrate that cancer cells exhibiting individual invasion in collagen matrices preferentially adopt a specific mode of collective invasion when transmigrating a cell-assembled BM that is not observed in any other tested fibrillar, non-fibrillar, or composite ECM. Matrix-degrading enzymes are found to be crucial during BM breaching but not during subsequent invasion in the collagen matrix. It is further shown that multicellular transmigration of the BM is less susceptible to pharmacological MMP inhibition than multicellular invasion in composite collagen/basement membrane extract matrices. The newly developed in vitro model of metastasis allows 3D cancer cell invasion to be studied not only as a function of a particular tumor's genetics but also as a function of its heterogeneous environment and the different stages of invasion. As such, this model is a valuable new tool with which to dissect basic mechanisms of invasion and metastasis and develop new therapeutic approaches in a physiologically relevant, yet inexpensive and highly tunable, in vitro setting.

A three-dimensional spheroidal cancer model based on PEG-fibrinogen hydrogel microspheres

Three-dimensional (3D) in vitro cancer models offer an attractive approach towards the investigation of tumorigenic phenomena and other cancer studies by providing dimensional context and higher degree of physiological relevance than that offered by conventional two-dimensional (2D) models. The multicellular tumor spheroid model, formed by cell aggregation, is considered to be the "gold standard" for 3D cancer models, due to its ease and simplicity of use. Although better than 2D models, tumor spheroids are unable to replicate key features of the native tumor microenvironment, particularly due to a lack of surrounding extracellular matrix components and heterogeneity in shape, size and aggregate forming tendencies. In order to address this issue, we have developed a 3D "tumor microsphere" model, formed by a dual-photoinitiator, aqueous-oil emulsion technique, for the encapsulation of cancer cells within PEG-fibrinogen hydrogel microspheres and for subsequent long-term 3D culture. In comparison to self-aggregated tumor spheroids, the tumor microspheres displayed a higher degree of size and shape homogeneity throughout long-term culture. In sharp contrast to cells in tumor spheroids, cells within tumor microspheres demonstrated significant loss in apico-basal polarity and cellular architecture, cellular and nuclear atypia, increased disorganization, elevated nuclear cytoplasmic ratio and nuclear volume density and reduction in cell-cell junction length, all of which are hallmarks of malignant transformation and tumorigenic progression. Additionally, the tumor microsphere model was extended for the 3D encapsulation and maintenance of a wide range of other cancer cell (metastatic and non-metastatic) types. Taken together, our results reinforce the importance of incorporating a biomimetic matrix in the cellular microenvironment of 3D tumor models and the influential effects of the matrix on the tumorigenic morphology of 3D cultured cells. The tumor microsphere system established in this study has the potential to be used in future investigations of 3D cancer cell-cell and cell-ECM interactions and in drug-testing applications.

Regulation of LOXL2 and SERPINH1 by antitumor microRNA-29a in lung cancer with idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive lung disease that is refractory to treatment and carries a high mortality rate. IPF is frequently associated with lung cancer. Identification of molecular targets involved in both diseases may elucidate novel molecular mechanisms contributing to their pathology. Recent studies of microRNA (miRNA) expression signatures showed that microRNA-29a (miR-29a) was downregulated in IPF and lung cancer. The aim of this study was to investigate the functional significance of miR-29a in lung cancer cells (A549 and EBC-1) and lung fibroblasts (MRC-5) and to identify molecular targets modulated by miR-29a in these cells. We confirmed the downregulation of miR-29a in clinical specimens of IPF and lung cancer. Restoration of miR-29a suppressed cancer cell aggressiveness and fibroblast migration. A combination of gene expression data and in silico analysis showed that a total of 24 genes were putative targets of miR-29a. Among them, lysyl oxidase-like 2 (LOXL2) and serpin peptidase inhibitor clade H, member 1 (SERPINH1) were direct targets of miR-29a by luciferase reporter assays. The functions of LOXL2 and SERPINH1 contribute significantly to collagen biosynthesis. Overexpression of LOXL2 and SERPINH1 was observed in clinical specimens of lung cancer and fibrotic lesions. Downregulation of miR-29a caused overexpression of LOXL2 and SERPINH1 in lung cancer and IPF, suggesting that these genes are involved in the pathogenesis of these two diseases.

Analysis of different components in the peritumoral tissue microenvironment of colorectal cancer: A potential prospect in tumorigenesis

The present study aimed to observe the varying expression of biomarkers in the microenvironment adjacent to colorectal cancer lesions to provide additional insight into the functions of microenvironment components in carcinogenesis and present a novel or improved indicator for early diagnosis of cancer. A total of 144 human samples from three different locations in 48 patients were collected, these locations were 10, 5 and 2 cm from the colorectal cancer lesion, respectively. The biomarkers analyzed included E‑cadherin, cytokeratin 18 (CK18), hyaluronidase‑1 (Hyal‑1), collagen type I (Col‑I), Crumbs3 (CRB3), vimentin, proteinase activated receptor 3 (PAR‑3), α‑smooth muscle actin (α‑SMA), cyclin D1 (CD1) and cluster of differentiation (CD)133. In addition, crypt architecture was observed. Related functional analysis of proteins was performed using hierarchical index cluster analysis. More severe destroyed crypt architecture closer to the cancer lesions was observed compared with the 10 cm sites, with certain crypts degraded entirely. Expression levels of E‑cadherin, CK18, CRB3 and PAR‑3 were lower in 2 cm sites compared with the 10 cm sites (all P<0.001), while the expression levels of the other biomarkers in the 2 cm sites were increased compared with 10 cm sites (all P<0.0001). Notably, the expression of CK18 in 2 cm sites was higher than in the 5 cm site (P<0.0001), which was different from the expression of E‑cadherin, CRB3 and PAR‑3. The expression levels of Hyal‑1 and Col‑I at the 2 cm sites were lower than that of the 5 cm sites (P>0.05 and P=0.0001, respectively), while the expression of vimentin, α‑SMA, CD1 and CD133 were not. Hyal‑1 and Col‑I may be independently important in cancer initiation in the tumor microenvironment. The results of the present study suggest that the biomarkers in the tissue microenvironment are associated with early tumorigenesis and may contribute to the development of carcinomas. These observations may be useful for early diagnosis of colorectal cancer.

Regulation of Epithelial-to-Mesenchymal Transition Using Biomimetic Fibrous Scaffolds

Epithelial-to-mesenchymal transition (EMT) is a well-studied biological process that takes place during embryogenesis, carcinogenesis, and tissue fibrosis. During EMT, the polarized epithelial cells with a cuboidal architecture adopt an elongated fibroblast-like morphology. This process is accompanied by the expression of many EMT-specific molecular markers. Although the molecular mechanism leading to EMT has been well-established, the effects of matrix topography and microstructure have not been clearly elucidated. Synthetic scaffolds mimicking the meshlike structure of the basement membrane with an average fiber diameter of 0.5 and 5 μm were produced via the electrospinning of poly(ε-caprolactone) (PCL) and were used to test the significance of fiber diameter on EMT. Cell-adhesive peptide motifs were conjugated to the fiber surface to facilitate cell attachment. Madin-Darby Canine Kidney (MDCK) cells grown on these substrates showed distinct phenotypes. On 0.5 μm substrates, cells grew as compact colonies with an epithelial phenotype. On 5 μm scaffolds, cells were more individually dispersed and appeared more fibroblastic. Upon the addition of hepatocyte growth factor (HGF), an EMT inducer, cells grown on the 0.5 μm scaffold underwent pronounced scattering, as evidenced by the alteration of cell morphology, localization of focal adhesion complex, weakening of cell-cell adhesion, and up-regulation of mesenchymal markers. In contrast, HGF did not induce a pronounced scattering of MDCK cells cultured on the 5.0 μm scaffold. Collectively, our results show that the alteration of the fiber diameter of proteins found in the basement membrane may create enough disturbances in epithelial organization and scattering that might have important implications in disease progression.

Stromal androgen receptor regulates the composition of the microenvironment to influence prostate cancer outcome

Androgen receptor (AR) signaling in stromal cells is important in prostate cancer, yet the mechanisms underpinning stromal AR contribution to disease development and progression remain unclear. Using patient-matched benign and malignant prostate samples, we show a significant association between low AR levels in cancer associated stroma and increased prostate cancer-related death at one, three and five years post-diganosis, and in tissue recombination models with primary prostate cancer cells that low stromal AR decreases castration-induced apoptosis. AR-regulation was found to be different in primary human fibroblasts isolated from adjacent to cancerous and non-cancerous prostate epithelia, and to represent altered activation of myofibroblast pathways involved in cell cycle, adhesion, migration, and the extracellular matrix (ECM). Without AR signaling, the fibroblast-derived ECM loses the capacity to promote attachment of both myofibroblasts and cancer cells, is less able to prevent cell-matrix disruption, and is less likely to impede cancer cell invasion. AR signaling in prostate cancer stroma appears therefore to alter patient outcome by maintaining an ECM microenvironment inhibitory to cancer cell invasion. This paper provides comprehensive insight into AR signaling in the non-epithelial prostate microenvironment, and a resource from which the prognostic and therapeutic implications of stromal AR levels can be further explored.

Syndecan-1-Induced ECM Fiber Alignment Requires Integrin αvβ3 and Syndecan-1 Ectodomain and Heparan Sulfate Chains

Expression of the cell surface proteoglycan syndecan-1 (Sdc1) is frequently induced in stromal fibroblasts of invasive breast carcinomas. We have recently identified a correlation between stromal Sdc1 expression and extracellular matrix (ECM) fiber alignment, both in vitro and in vivo. ECMs derived from Sdc1-positive human mammary fibroblasts (HMF) showed an aligned fiber architecture, which contrasted markedly with the more random fiber arrangement in the ECM produced by Sdc1-negative HMFs. We further demonstrated that aligned fiber architecture promotes the directional migration and invasion of breast carcinoma cells. To decipher the molecular mechanisms governing the formation of an aligned, invasion-permissive ECM, a series of Sdc1 mutants was introduced into HMF. We found that both the ectodomain and heparan sulfate chains of Sdc1 were required for full activity of Sdc1 in regulating ECM alignment, while transmembrane and cytoplasmic domains were dispensable. Sdc1 regulates the activities of several integrins via its ectodomain. Integrins are key players in the assembly of fibronectin-rich ECM. In addition, integrins are capable of regulating cell morphology and cell shape and orientation may affect ECM architecture. Therefore, we investigated the role of integrins in Sdc1-mediated ECM fiber alignment. Sdc1-overexpressing HMF gained an enhanced spindle-shaped morphology when cultured in an overconfluent state under conditions permissive for ECM production, which was partially reversed by siRNA-mediated silencing of β3 integrin expression. Moreover, suppression of αvβ3 integrin activity by a function-blocking antibody or β3 knockdown largely abolished the aligned ECM fiber architecture and consequently the invasion-permissive properties of the ECM induced by Sdc1. The results suggest that Sdc1 may modulate fibronectin fibrillogenesis and/or alter cell morphology during ECM production through αvβ3 integrin, thereby mediating ECM fiber alignment. Understanding the mechanisms governing ECM organization may lead to the development of novel stroma-targeted therapy for breast cancer, aiming at converting an invasion-permissive to an invasion-restrictive microenvironment.

Proteolytic and non-proteolytic regulation of collective cell invasion: tuning by ECM density and organization

Cancer cells manoeuvre through extracellular matrices (ECMs) using different invasion modes, including single cell and collective cell invasion. These modes rely on MMP-driven ECM proteolysis to make space for cells to move. How cancer-associated alterations in ECM influence the mode of invasion remains unclear. Further, the sensitivity of the two invasion modes to MMP dynamics remains unexplored. In this paper, we address these open questions using a multiscale hybrid computational model combining ECM density-dependent MMP secretion, MMP diffusion, ECM degradation by MMP and active cell motility. Our results demonstrate that in randomly aligned matrices, collective cell invasion is more efficient than single cell invasion. Although increase in MMP secretion rate enhances invasiveness independent of cell-cell adhesion, sustenance of collective invasion in dense matrices requires high MMP secretion rates. However, matrix alignment can sustain both single cell and collective cell invasion even without ECM proteolysis. Similar to our in-silico observations, increase in ECM density and MMP inhibition reduced migration of MCF-7 cells embedded in sandwich gels. Together, our results indicate that apart from cell intrinsic factors (i.e., high cell-cell adhesion and MMP secretion rates), ECM density and organization represent two important extrinsic parameters that govern collective cell invasion and invasion plasticity.

The extracellular matrix in breast cancer

The extracellular matrix (ECM) is increasingly recognized as an important regulator in breast cancer. ECM in breast cancer development features numerous changes in composition and organization when compared to the mammary gland under homeostasis. Matrix proteins that are induced in breast cancer include fibrillar collagens, fibronectin, specific laminins and proteoglycans as well as matricellular proteins. Growing evidence suggests that many of these induced ECM proteins play a major functional role in breast cancer progression and metastasis. A number of the induced ECM proteins have moreover been shown to be essential components of metastatic niches, promoting stem/progenitor signaling pathways and metastatic growth. ECM remodeling enzymes are also markedly increased, leading to major changes in the matrix structure and biomechanical properties. Importantly, several ECM components and ECM remodeling enzymes are specifically induced in breast cancer or during tissue regeneration while healthy tissues under homeostasis express exceedingly low levels. This may indicate that ECM and ECM-associated functions may represent promising drug targets against breast cancer, providing important specificity that could be utilized when developing therapies.

Fibroblast-Mediated Collagen Remodeling Within the Tumor Microenvironment Facilitates Progression of Thyroid Cancers Driven by BrafV600E and Pten Loss

Contributions of the tumor microenvironment (TME) to progression in thyroid cancer are largely unexplored and may illuminate a basis for understanding rarer aggressive cases of this disease. In this study, we investigated the relationship between the TME and thyroid cancer progression in a mouse model where thyroid-specific expression of oncogenic BRAF and loss of Pten (Braf(V600E)/Pten(-/-)/TPO-Cre) leads to papillary thyroid cancers (PTC) that rapidly progress to poorly differentiated thyroid cancer (PDTC). We found that fibroblasts were recruited to the TME of Braf(V600E)/Pten(-/-)/TPO-Cre thyroid tumors. Conditioned media from cell lines established from these tumors, but not tumors driven by mutant H-ras, induced fibroblast migration and proliferation in vitro Notably, the extracellular matrix of Braf(V600E)/Pten(-/-)/TPO-Cre tumors was enriched with stromal-derived fibrillar collagen, compared with wild-type or Hras-driven tumors. Further, type I collagen enhanced the motility of Braf(V600E)/Pten(-/-)/TPO-Cre tumor cells in vitro In clinical specimens, we found COL1A1 and LOX to be upregulated in PTC and expressed at highest levels in PDTC and anaplastic thyroid cancer. Additionally, increased expression levels of COL1A1 and LOX were associated with decreased survival in thyroid cancer patients. Overall, our results identified fibroblast recruitment and remodeling of the extracellular matrix as pivotal features of the TME in promoting thyroid cancer progression, illuminating candidate therapeutic targets and biomarkers in advanced forms of this malignancy. Cancer Res; 76(7); 1804-13. ©2016 AACR.

Tumor-suppressive microRNA-29 family inhibits cancer cell migration and invasion directly targeting LOXL2 in lung squamous cell carcinoma

Lung cancer remains the most frequent cause of cancer-related death in developed countries. A recent molecular-targeted strategy has contributed to improvement of the remarkable effect of adenocarcinoma of the lung. However, such treatment has not been developed for squamous cell carcinoma (SCC) of the disease. Our recent studies of microRNA (miRNA) expression signatures of human cancers showed that the microRNA-29 family (miR‑29a, miR‑29b and miR‑29c) significantly reduced cancer tissues compared to normal tissues. These findings suggest that miR‑29s act as tumor-suppressors by targeting several oncogenic genes. The aim of the study was to investigate the functional significance of miR‑29s in lung SCC and to identify miR‑29s modulating molecular targets in lung SCC cells. Restoration of all mature members of the miR‑29s inhibited cancer cell migration and invasion. Gene expression data combined in silico analysis and luciferase reporter assays demonstrated that the lysyl oxidase-like 2 (LOXL2) gene was a direct regulator of tumor‑suppressive miR‑29s. Moreover, overexpressed LOXL2 was confirmed in lung SCC clinical specimens, and silencing of LOXL2 inhibited cancer cell migration and invasion in lung SCC cell lines. Our present data suggested that loss of tumor-suppressive miR‑29s enhanced cancer cell invasion in lung SCC through direct regulation of oncogenic LOXL2. Elucidation of the novel lung SCC molecular pathways and targets regulated by tumor-suppressive miR‑29s will provide new insights into the potential mechanisms of oncogenesis and metastasis of the disease.

Identification of tumour-reactive lymphatic endothelial cells capable of inducing progression of gastric cancer

Background:

Tumour cells and stromal cells interact in the tumour microenvironment; moreover, stromal cells can acquire abnormalities that contribute to tumour progression. However, interactions between lymphatic endothelial cells (LECs) and tumour cells are largely unexamined. In this study, we aimed to determine whether tumour-specific LECs inhabit the tumour microenvironment and examine their influence on this microenvironment.

Methods:

We isolated normal LECs (NLECs) from a non-metastatic lymph node and tumour-associated LECs (TLECs) from cancerous lymph nodes. We examined proliferative and migratory potency, growth factor production, and gene expression of each type of LEC. Moreover, we developed a co-culture system to investigate the interactions between gastric cancer cells and LECs.

Results:

When compared with NLEC, TLECs had an abnormal shape, high proliferative and migratory abilities, and elevated expression of genes associated with inflammation, cell growth, and cell migration. NLECs co-cultured with gastric cancer cells from the OCUM12 cell line acquired TLEC-like phenotypes. Also, OCUM12 cells co-cultured with TLECs expressed high levels of genes responsible for metastasis.

Conclusions:

Our results demonstrated that LECs interacted with tumour cells and obtained abnormal phenotypes that could have important roles in tumour progression.

Progress toward overcoming hypoxia-induced resistance to solid tumor therapy

Hypoxic tumors are associated with poor clinical outcome for multiple types of human cancer. This may be due, in part, to hypoxic cancer cells being resistant to anticancer therapy, including radiation therapy, chemotherapy, and targeted therapy. Hypoxia inducible factor 1, a major regulator of cellular response to hypoxia, regulates the expression of genes that are involved in multiple aspects of cancer biology, including cell survival, proliferation, metabolism, invasion, and angiogenesis. Here, we review multiple pathways regulated by hypoxia/hypoxia inducible factor 1 in cancer cells and discuss the latest advancements in overcoming hypoxia-mediated tumor resistance.

Dense fibrillar collagen is a potent inducer of invadopodia via a specific signaling network

High-density fibrillar collagen matrix induces invadopodia formation in both fibroblasts and carcinoma cell lines through a kindlin2-dependent mechanism that drives local ECM remodeling.

Cell interactions with the extracellular matrix (ECM) can regulate multiple cellular activities and the matrix itself in dynamic, bidirectional processes. One such process is local proteolytic modification of the ECM. Invadopodia of tumor cells are actin-rich proteolytic protrusions that locally degrade matrix molecules and mediate invasion. We report that a novel high-density fibrillar collagen (HDFC) matrix is a potent inducer of invadopodia, both in carcinoma cell lines and in primary human fibroblasts. In carcinoma cells, HDFC matrix induced formation of invadopodia via a specific integrin signaling pathway that did not require growth factors or even altered gene and protein expression. In contrast, phosphoproteomics identified major changes in a complex phosphosignaling network with kindlin2 serine phosphorylation as a key regulatory element. This kindlin2-dependent signal transduction network was required for efficient induction of invadopodia on dense fibrillar collagen and for local degradation of collagen. This novel phosphosignaling mechanism regulates cell surface invadopodia via kindlin2 for local proteolytic remodeling of the ECM.

Type III Collagen Directs Stromal Organization and Limits Metastasis in a Murine Model of Breast Cancer

Breast cancer metastasis is the leading cause of cancer-related deaths in women worldwide. Collagen in the tumor microenvironment plays a crucial role in regulating tumor progression. We have shown that type III collagen (Col3), a component of tumor stroma, regulates myofibroblast differentiation and scar formation after cutaneous injury. During the course of these wound-healing studies, we noted that tumors developed at a higher frequency in Col3(+/-) mice compared to wild-type littermate controls. We, therefore, examined the effect of Col3 deficiency on tumor behavior, using the murine mammary carcinoma cell line 4T1. Notably, tumor volume and pulmonary metastatic burden after orthotopic injection of 4T1 cells were increased in Col3(+/-) mice compared to Col3(+/+) littermates. By using murine (4T1) and human (MDA-MB-231) breast cancer cells grown in Col3-poor and Col3-enriched microenvironments in vitro, we found that several major events of the metastatic process were suppressed by Col3, including adhesion, invasion, and migration. In addition, Col3 deficiency increased proliferation and decreased apoptosis of 4T1 cells both in vitro and in primary tumors in vivo. Mechanistically, Col3 suppresses the procarcinogenic microenvironment by regulating stromal organization, including density and alignment of fibrillar collagen and myofibroblasts. We propose that Col3 plays an important role in the tumor microenvironment by suppressing metastasis-promoting characteristics of the tumor-associated stroma.

Tumor mechanics and metabolic dysfunction

Desmosplasia is a characteristic of most solid tumors and leads to fibrosis through abnormal extracellular matrix (ECM) deposition, remodeling, and posttranslational modifications. The resulting stiff tumor stroma not only compromises vascular integrity to induce hypoxia and impede drug delivery, but also promotes aggressiveness by potentiating the activity of key growth, invasion, and survival pathways. Intriguingly, many of the protumorigenic signaling pathways that are mechanically activated by ECM stiffness also promote glucose uptake and aerobic glycolysis, and an altered metabolism is a recognized hallmark of cancer. Indeed, emerging evidence suggests that metabolic alterations and an abnormal ECM may cooperatively drive cancer cell aggression and treatment resistance. Accordingly, improved methods to monitor tissue mechanics and metabolism promise to improve diagnostics and treatments to ameliorate ECM stiffening and elevated mechanosignaling may improve patient outcome. Here we discuss the interplay between ECM mechanics and metabolism in tumor biology and suggest that monitoring these processes and targeting their regulatory pathways may improve diagnostics, therapy, and the prevention of malignant transformation.

Microenvironmental regulation of therapeutic response in cancer

The tumor microenvironment (TME) not only plays a pivotal role during cancer progression and metastasis but also has profound effects on therapeutic efficacy. In the case of microenvironment-mediated resistance this can involve an intrinsic response, including the co-option of pre-existing structural elements and signaling networks, or an acquired response of the tumor stroma following the therapeutic insult. Alternatively, in other contexts, the TME has a multifaceted ability to enhance therapeutic efficacy. This review examines recent advances in our understanding of the contribution of the TME during cancer therapy and discusses key concepts that may be amenable to therapeutic intervention.

Lessons from patient-derived xenografts for better in vitro modeling of human cancer

The development of novel cancer therapeutics is often plagued by discrepancies between drug efficacies obtained in preclinical studies and outcomes of clinical trials. The inconsistencies can be attributed to a lack of clinical relevance of the cancer models used for drug testing. While commonly used in vitro culture systems are advantageous for addressing specific experimental questions, they are often gross, fidelity-lacking simplifications that largely ignore the heterogeneity of cancers as well as the complexity of the tumor microenvironment. Factors such as tumor architecture, interactions among cancer cells and between cancer and stromal cells, and an acidic tumor microenvironment are critical characteristics observed in patient-derived cancer xenograft models and in the clinic. By mimicking these crucial in vivo characteristics through use of 3D cultures, co-culture systems and acidic culture conditions, an in vitro cancer model/microenvironment that is more physiologically relevant may be engineered to produce results more readily applicable to the clinic.

Association of the G473A polymorphism and expression of lysyl oxidase with breast cancer risk and survival in European women: a hospital-based case-control study

Background

Lysyl oxidase (LOX) is an extracellular enzyme essential for the covalent crosslinking of extracellular matrix proteins and may also have additional functions. LOX expression can be both up- and downregulated in cancer and is associated both with tumour suppression and metastasis progression. The G473A polymorphism (rs1800449) results in the Arg158Gln amino acid substitution in the LOX propeptide, compromises its tumour suppressive activity, and was associated with an increased breast cancer risk in a Chinese Han population. In the first hospital-based case-control study in European women, we aimed at investigating the association of LOX expression and the G473A polymorphism with breast cancer risk and survival in unselected and estrogen receptor (ER) negative patients.

Methodology/Principal Findings

The G473A polymorphism was genotyped in 386 breast cancer patients and 243 female controls. Moreover, LOX mRNA expression was quantified in the tumors of 105 patients by qRT-PCR. We found that the minor A-allele of this polymorphism is associated with a later age at breast cancer onset, a trend towards a decreased disease-free and metastasis-free survival, but not with an increased breast cancer risk. LOX mRNA expression was significantly elevated in tumours of patients older than 55 years, postmenopausal patients, estrogen receptor positive tumours, and p53 negative tumours, but was unaffected by G473A genotype in tumours and breast cancer cell lines. High LOX expression was associated with a poor disease-free and metastasis-free survival in ER negative but not ER positive patients. LOX expression was an independent prognostic parameter in multivariate analysis, whereas G473A genotype was not. A small, distinct subgroup of the ER negative patients was identified which exhibited a considerably elevated LOX expression and a very poor disease-free (p = 0.001) and metastasis-free survival (p = 0.0003).

Conclusions/Significance

This newly identified ER negative/LOX high subgroup may be a suitable collective for future individualized breast cancer diagnosis and therapy.

Illuminating breast cancer invasion: diverse roles for cell-cell interactions

Metastasis begins when tumors invade into surrounding tissues. In breast cancer, the study of cell interactions has provided fundamental insights into this complex process. Powerful intravital and 3D organoid culture systems have emerged that enable biologists to model the complexity of cell interactions during cancer invasion in real-time. Recent studies utilizing these techniques reveal distinct mechanisms through which multiple cancer cell and stromal cell subpopulations interact, including paracrine signaling, direct cell-cell adhesion, and remodeling of the extracellular matrix. Three cell interaction mechanisms have emerged to explain how breast tumors become invasive: epithelial-mesenchymal transition, collective invasion, and the macrophage-tumor cell feedback loop. Future work is needed to distinguish whether these mechanisms are mutually exclusive or whether they cooperate to drive metastasis.

Serum biomarkers reflecting specific tumor tissue remodeling processes are valuable diagnostic tools for lung cancer

Extracellular matrix (ECM) proteins, such as collagen type I and elastin, and intermediate filament (IMF) proteins, such as vimentin are modified and dysregulated as part of the malignant changes leading to disruption of tissue homeostasis. Noninvasive biomarkers that reflect such changes may have a great potential for cancer. Levels of matrix metalloproteinase (MMP) generated fragments of type I collagen (C1M), of elastin (ELM), and of citrullinated vimentin (VICM) were measured in serum from patients with lung cancer (n = 40), gastrointestinal cancer (n = 25), prostate cancer (n = 14), malignant melanoma (n = 7), chronic obstructive pulmonary disease (COPD) (n = 13), and idiopathic pulmonary fibrosis (IPF) (n = 10), as well as in age-matched controls (n = 33). The area under the receiver operating characteristics (AUROC) was calculated and a diagnostic decision tree generated from specific cutoff values. C1M and VICM were significantly elevated in lung cancer patients as compared with healthy controls (AUROC = 0.98, P < 0.0001) and other cancers (AUROC = 0.83 P < 0.0001). A trend was detected when comparing lung cancer with COPD+IPF. No difference could be seen for ELM. Interestingly, C1M and VICM were able to identify patients with lung cancer with a positive predictive value of 0.9 and an odds ratio of 40 (95% CI = 8.7–186, P < 0.0001). Biomarkers specifically reflecting degradation of collagen type I and citrullinated vimentin are applicable for lung cancer patients. Our data indicate that biomarkers reflecting ECM and IMF protein dysregulation are highly applicable in the lung cancer setting. We speculate that these markers may aid in diagnosing and characterizing patients with lung cancer.

Tumour-stroma crosstalk in the development of squamous cell carcinoma

Squamous cell carcinoma (SCC) represents one of the most frequently diagnosed tumours and contributes significant mortality worldwide. Recent deep sequencing of cancer genomes has identified common mutations in SCC arising across different tissues highlighting perturbation of squamous differentiation as a key event. At the same time significant data have been accumulating to show that common tumour-stroma interactions capable of driving disease progression are also evident when comparing SCC arising in different tissues. We and others have shown altered matrix composition surrounding SCC can promote tumour development. This review focuses on some of the emerging data with particular emphasis on SCC of head and neck and skin with discussion on the potential tumour suppressive properties of a normal microenvironment. Such data indicate that regardless of the extent and type of somatic mutation it is in fact the tumour context that defines metastatic progression.

Hypoxia and the extracellular matrix: drivers of tumour metastasis

Of the deaths attributed to cancer, 90% are due to metastasis, and treatments that prevent or cure metastasis remain elusive. Emerging data indicate that hypoxia and the extracellular matrix (ECM) might have crucial roles in metastasis. During tumour evolution, changes in the composition and the overall content of the ECM reflect both its biophysical and biological properties and these strongly influence tumour and stromal cell properties, such as proliferation and motility. Originally thought of as independent contributors to metastatic spread, recent studies have established a direct link between hypoxia and the composition and the organization of the ECM, which suggests a new model in which multiple microenvironmental signals might converge to synergistically influence metastatic outcome.

The effect of fibrillar matrix architecture on tumor cell invasion of physically challenging environments

Local invasion by and dissemination of cancer cells from a primary tumor are key initial steps of metastasis, the most lethal aspect of cancer. To study these processes in vitro, the invasion of cells from multicellular breast cancer aggregates embedded in three-dimensional (3D) extracellular matrix culture systems was studied. This work showed that in 3D fibrillar environments composed of collagen I, pore size--not the viscoelastic properties of the matrix--was the biophysical characteristic controlling breast cancer cell invasion efficiency. Furthermore, it was shown that fibrillar matrix architecture is a crucial factor that allows for efficient 3D invasion. In a 3D non-fibrillar environment composed of basement membrane extract (BME), invasion efficiency was greatly diminished, the mesenchymal individual mode of 3D invasion was abolished, and establishment of cell polarity and protrusions was compromised. These effects were seen even though the BME matrix has invasion permissive viscoelasticity and suitable adhesion ligands. The altered and limited invasive behavior observed in BME was rescued through introduction of fibrillar collagen into the non-fibrillar matrix. The biophysical cues of fibrillar collagen facilitated efficient invasion of sterically disadvantageous environments through assisting cell polarization and formation of stable cell protrusions. Finally, we suggest the composite matrices employed in this study consisting of fibrillar collagen I and BME in either a liquid-like or gelled state are suitable for a wide range of 3D cell studies, as these matrices combine fibrillar features that require cells to deploy integrin-dependent mechanotransduction machinery and a tunable non-fibrillar component that may require cells to adopt alternative migratory modes.

Modulation of tumor cell stiffness and migration by type IV collagen through direct activation of integrin signaling pathway

Excessive collagen deposition plays a critical role in tumor progression and metastasis. To understand how type IV collagen affects mechanical stiffness and migration, low-collagen-IV-expressing transfectants of B16F10, U118MG, and Huh7 (denoted shCol cells) were established by the lentiviral-mediated delivery of small interfering RNA against type IV-α1 collagen (Col4A1). Although having similar growth rates, shCol cells showed a flatter morphology compared to that of the corresponding controls. Notably, knocking down the Col4A1 gene conferred the cells with higher levels of elasticity and lower motility. Exposure to blocking antibodies against human β1 integrin or α2β1 integrin or the pharmacological inhibition of Src and ERK activity by PP1 and U0126, respectively, effectively reduced cell motility and raised cell stiffness. Reduced Src and ERK activities in shCol cells indicate the involvement of a collagen IV/integrin signaling pathway. The forced expression of β1 integrin significantly stimulated Src and ERK phosphorylation, reduced cell stiffness, and accelerated cell motility. In an experimental metastasis assay using C57BL/6 mice, B16F10 shCol cells formed significantly fewer and smaller lung nodules, confirming the contribution of collagen to metastasis. In summary, the integrin signaling pathway activated in a tumor environment with collagen deposition is responsible for low cell elasticity and high metastatic ability.

Extracellular matrix macromolecules: potential tools and targets in cancer gene therapy

Tumour cells create their own microenvironment where they closely interact with a variety of soluble and non-soluble molecules, different cells and numerous other components within the extracellular matrix (ECM). Interaction between tumour cells and the ECM is bidirectional leading to either progression or inhibition of tumourigenesis. Therefore, development of novel therapies targeted primarily to tumour microenvironment (TME) is highly rational. Here, we give a short overview of different macromolecules of the ECM and introduce mechanisms whereby they contribute to tumourigenesis within the TME. Furthermore, we present examples of individual ECM macromolecules as regulators of cell behaviour during tumourigenesis. Finally, we focus on novel strategies of using ECM macromolecules as tools or targets in cancer gene therapy in the future.

Integrated extracellular matrix signaling in mammary gland development and breast cancer progression

Extracellular matrix (ECM), a major component of the cellular microenvironment, plays critical roles in normal tissue morphogenesis and disease progression. Binding of ECM to membrane receptor proteins, such as integrin, discoidin domain receptors, and dystroglycan, elicits biochemical and biomechanical signals that control cellular architecture and gene expression. These ECM signals cooperate with growth factors and hormones to regulate cell migration, differentiation, and transformation. ECM signaling is tightly regulated during normal mammary gland development. Deposition and alignment of fibrillar collagens direct migration and invasion of mammary epithelial cells during branching morphogenesis. Basement membrane proteins are required for polarized acinar morphogenesis and milk protein expression. Deregulation of ECM proteins in the long run is sufficient to promote breast cancer development and progression. Recent studies demonstrate that the integrated biophysical and biochemical signals from ECM and soluble factors are crucial for normal mammary gland development as well as breast cancer progression.

Insidious changes in stromal matrix fuel cancer progression

Reciprocal interactions between tumor and stromal cells propel cancer progression and metastasis. A complete understanding of the complex contributions of the tumor stroma to cancer progression necessitates a careful examination of the extracellular matrix (ECM), which is largely synthesized and modulated by cancer-associated fibroblasts. This structurally supportive meshwork serves as a signaling scaffold for a myriad of biologic processes and responses favoring tumor progression. The ECM is a repository for growth factors and cytokines that promote tumor growth, proliferation, and metastasis through diverse interactions with soluble and insoluble ECM components. Growth factors activated by proteases are involved in the initiation of cell signaling pathways essential to invasion and survival. Various transmembrane proteins produced by the cancer stroma bind the collagen and fibronectin-rich matrix to induce proliferation, adhesion, and migration of cancer cells, as well as protease activation. Integrins are critical liaisons between tumor cells and the surrounding stroma, and with their mechano-sensing ability, induce cell signaling pathways associated with contractility and migration. Proteoglycans also bind and interact with various matrix proteins in the tumor microenvironment to promote cancer progression. Together, these components function to mediate cross-talk between tumor cells and fibroblasts ultimately to promote tumor survival and metastasis. These stromal factors, which may be expressed differentially according to cancer stage, have prognostic utility and potential. This review examines changes in the ECM of cancer-associated fibroblasts induced through carcinogenesis, and the impact of these changes on cancer progression. The implication is that cancer progression, even in epithelial cancers, may be based in large part on changes in signaling from cancer-associated stromal cells. These changes may provide early prognostic indicators to further stratify patients during treatment or alter the timing of their follow-up visits and observations.

Procollagen assays in cancer

The synthesis rates of fibrillar collagens can be assessed in blood by measuring propeptides set free from corresponding procollagens before fiber formation. Type I collagen is the major component of the organic matrix of bone, but it is also found in other connective tissues. The serum concentration of the amino-terminal propeptide of type I procollagen, PINP, functions as a measure of type I collagen synthesis during normal bone turnover, but it is also released from bone metastases that involve an osteoblastic component. Type III collagen is a major constituent of soft tissues and the corresponding amino-terminal propeptide, PIIINP, reflects collagen synthesis. Circulating PIIINP tends to be affected by malignomas that grow in the peritoneal cavity or affect bone marrow. Many studies on procollagen markers in cancer have been cross-sectional or demonstrated treatment effects in patient groups. Markers that originate from bone turnover have wide reference intervals, but low biologic variability in individuals. Thus, they appear better suited for monitoring versus diagnostic purposes. There is still definite need for research on the use of procollagen markers in the followup of individual patients undergoing cancer treatment or being monitored after such treatment.

EFFECTS OF POLYMERIC NANOPARTICLE SURFACE PROPERTIES ON INTERACTION WITH BRAIN TUMOR ENVIRONMENT

Current chemotherapy treatments are limited by poor drug solubility, rapid drug clearance and systemic side effects. Additionally, drug penetration into solid tumors is limited by physical diffusion barriers [e.g., extracellular matrix (ECM)]. Nanoparticle (NP) blood circulation half-life, biodistribution and ability to cross extracellular and cellular barriers will be dictated by NP composition, size, shape and surface functionality. Here, we investigated the effect of surface charge of poly(lactide)-poly(ethylene glycol) NPs on mediating cellular interaction. Polymeric NPs of equal sizes were used that had two different surface functionalities: negatively charged carboxyl (COOH) and neutral charged methoxy (OCH3). Cellular uptake studies showed significantly higher uptake in human brain cancer cells compared to noncancerous human brain cells, and negatively charged COOH NPs were uptaken more than neutral OCH3 NPs in 2D culture. NPs were also able to load and control the release of paclitaxel (PTX) over 19 days. Toxicity studies in U-87 glioblastoma cells showed that PTX-loaded NPs were effective drug delivery vehicles. Effect of surface charge on NP interaction with the ECM was investigated using collagen in a 3D cellular uptake model, as collagen content varies with the type of cancer and the stage of the disease compared to normal tissues. Results demonstrated that NPs can effectively diffuse across an ECM barrier and into cells, but NP mobility is dictated by surface charge. In vivo biodistribution of OCH3 NPs in intracranial tumor xenografts showed that NPs more easily accumulated in tumors with less collagen. These results indicate that a robust understanding of NP interaction with various tumor environments can lead to more effective patient-tailored therapies.

Camel milk inhibits inflammatory angiogenesis via downregulation of proangiogenic and proinflammatory cytokines in mice

Camel milk has traditionally been used to treat cancer, but this practice awaits scientific scrutiny, in particular its role in tumor angiogenesis, the key step involved in tumor growth and metastasis. We aimed to investigate the effects of camel milk on key components of inflammatory angiogenesis in sponge implant angiogenesis model. Polyester-polyurethane sponges, used as a framework for fibrovascular tissue growth, were implanted in Swiss albino mice and camel milk (25, 50 and 100 mg/kg/day) was administered for 14 days through installed cannula. The implants collected at day 14 post-implantation were processed for the assessment of hemoglobin (Hb), myeloperoxidase (MPO), N-acetylglucosaminidase (NAG), and collagen, which were used as indices for angiogenesis, neutrophil, and macrophage accumulation and extracellular matrix deposition, respectively. Relevant inflammatory, angiogenic, and fibrogenic cytokines were also determined. Camel milk treatment attenuated the main components of the fibrovascular tissue, wet weight, vascularization (Hb content), macrophage recruitment (NAG activity), collagen deposition and the levels of vascular endothelial growth factor (VEGF), interleukin (IL)-1β, IL-6, IL-17, tumor necrosis factor-α, and transforming growth factor-β. A regulatory function of camel milk on multiple parameters of the main components of inflammatory angiogenesis has been revealed, giving insight into the potential therapeutic benefit underlying the anti-cancer actions of camel milk.

Nanooncology: the future of cancer diagnosis and therapy

In recent years, there has been an unprecedented expansion in the field of nanomedicine with the development of new nanoparticles for the diagnosis and treatment of cancer. Nanoparticles have unique biological properties given their small size and large surface area-to-volume ratio, which allows them to bind, absorb, and carry compounds such as small molecule drugs, DNA, RNA, proteins, and probes with high efficiency. Their tunable size, shape, and surface characteristics also enable them to have high stability, high carrier capacity, the ability to incorporate both hydrophilic and hydrophobic substances and compatibility with different administration routes, thereby making them highly attractive in many aspects of oncology. This review article will discuss how nanoparticles are able to function as carriers for chemotherapeutic drugs to increase their therapeutic index; how they can function as therapeutic agents in photodynamic, gene, and thermal therapy; and how nanoparticles can be used as molecular imaging agents to detect and monitor cancer progression.

Discoipyrroles A-D: isolation, structure determination, and synthesis of potent migration inhibitors from Bacillus hunanensis

Discoidin domain receptor 2 (DDR2) is a receptor tyrosine kinase involved in a variety of cellular response pathways, including regulation of cell growth, proliferation, and motility. Using a newly developed platform to identify the signaling pathway/molecular target of natural products, we identified a family of alkaloid natural products, discoipyrroles A-D (1-4), from Bacillus hunanensis that inhibit the DDR2 signaling pathway. The structure of 1-4, determined by detailed two-dimensional (2D) NMR methods and confirmed by X-ray crystallographic analysis has an unusual 3H-benzo[d]pyrrolo][1,3]oxazine-3,5-dione core. Discoipyrroles A-D potently inhibit DDR2 dependent migration of BR5 fibroblasts and show selective cytotoxicity to DDR2 mutant lung cancer cell lines (IC50 120-400 nM). Examination of the biosynthesis has led to the conclusion that the discoipyrroles are formed through a nonenzymatic process, leading to a one-pot total synthesis of 1.

Strategies to increase drug penetration in solid tumors

Despite significant improvement in modalities for treatment of cancer that led to a longer survival period, the death rate of patients with solid tumors has not changed during the last decades. Emerging studies have identified several physical barriers that limit the therapeutic efficacy of cancer therapeutic agents such as monoclonal antibodies, chemotherapeutic agents, anti-tumor immune cells, and gene therapeutics. Most solid tumors are of epithelial origin and, although malignant cells are de-differentiated, they maintain intercellular junctions, a key feature of epithelial cells, both in the primary tumor as well as in metastatic lesions. Furthermore, nests of malignant epithelial tumor cells are shielded by layers of extracellular matrix (ECM) proteins (e.g., collagen, elastin, fibronectin, laminin) whereby tumor vasculature rarely penetrates into the tumor nests. In this chapter, we will review potential strategies to modulate the ECM and epithelial junctions to enhance the intratumoral diffusion and/or to remove physical masking of target receptors on malignant cells. We will focus on peptides that bind to the junction protein desmoglein 2 and trigger intracellular signaling, resulting in the transient opening of intercellular junctions. Intravenous injection of these junction openers increased the efficacy and safety of therapies with monoclonal antibodies, chemotherapeutics, and T cells in mouse tumor models and was safe in non-human primates. Furthermore, we will summarize approaches to transiently degrade ECM proteins or downregulate their expression. Among these approaches is the intratumoral expression of relaxin or decorin after adenovirus- or stem cell-mediated gene transfer. We will provide examples that relaxin-based approaches increase the anti-tumor efficacy of oncolytic viruses, monoclonal antibodies, and T cells.

Modeling the mechanics of cancer: effect of changes in cellular and extra-cellular mechanical properties

Malignant transformation, though primarily driven by genetic mutations in cells, is also accompanied by specific changes in cellular and extra-cellular mechanical properties such as stiffness and adhesivity. As the transformed cells grow into tumors, they interact with their surroundings via physical contacts and the application of forces. These forces can lead to changes in the mechanical regulation of cell fate based on the mechanical properties of the cells and their surrounding environment. A comprehensive understanding of cancer progression requires the study of how specific changes in mechanical properties influences collective cell behavior during tumor growth and metastasis. Here we review some key results from computational models describing the effect of changes in cellular and extra-cellular mechanical properties and identify mechanistic pathways for cancer progression that can be targeted for the prediction, treatment, and prevention of cancer.

The collagen receptor discoidin domain receptor 2 stabilizes SNAIL1 to facilitate breast cancer metastasis

Increased stromal collagen deposition in human breast tumours correlates with metastases. We show that activation of the collagen I receptor DDR2 (discoidin domain receptor 2) regulates SNAIL1 stability by stimulating ERK2 activity, in a Src-dependent manner. Activated ERK2 directly phosphorylates SNAIL1, leading to SNAIL1 nuclear accumulation, reduced ubiquitylation and increased protein half-life. DDR2-mediated stabilization of SNAIL1 promotes breast cancer cell invasion and migration in vitro, and metastasis in vivo. DDR2 expression was observed in most human invasive ductal breast carcinomas studied, and was associated with nuclear SNAIL1 and absence of E-cadherin expression. We propose that DDR2 maintains SNAIL1 level and activity in tumour cells that have undergone epithelial-mesenchymal transition (EMT), thereby facilitating continued tumour cell invasion through collagen-I-rich extracellular matrices by sustaining the EMT phenotype. As such, DDR2 could be an RTK (receptor tyrosine kinase) target for the treatment of breast cancer metastasis.

Microcalcifications in breast cancer: Lessons from physiological mineralization

Mammographic mammary microcalcifications are routinely used for the early detection of breast cancer, however the mechanisms by which they form remain unclear. Two species of mammary microcalcifications have been identified; calcium oxalate and hydroxyapatite. Calcium oxalate is mostly associated with benign lesions of the breast, whereas hydroxyapatite is associated with both benign and malignant tumors. The way in which hydroxyapatite forms within mammary tissue remains largely unexplored, however lessons can be learned from the process of physiological mineralization. Normal physiological mineralization by osteoblasts results in hydroxyapatite deposition in bone. This review brings together existing knowledge from the field of physiological mineralization and juxtaposes it with our current understanding of the genesis of mammary microcalcifications. As an increasing number of breast cancers are being detected in their non-palpable stage through mammographic microcalcifications, it is important that future studies investigate the underlying mechanisms of their formation in order to fully understand the significance of this unique early marker of breast cancer.

Strychnine inhibits inflammatory angiogenesis in mice via down regulation of VEGF, TNF-α and TGF-β

Strychnine is known to possess anti-inflammatory and antitumour activity, but its roles in tumour angiogenesis, the key step involved in tumour growth and metastasis, and the involved molecular mechanism are still unknown. We aimed to investigate the effects of strychnine on key components of inflammatory angiogenesis in the murine cannulated sponge implant angiogenesis model. Polyester-polyurethane sponges, used as a framework for fibrovascular tissue growth, were implanted in Swiss albino mice and strychnine (0.25, and 0.5 mg/kg/day) was given through installed cannulas for 9 days. The implants collected at day 9 postimplantation were processed for the assessment of haemoglobin (Hb), myeloperoxidase (MPO), N-acetylglucosaminidase (NAG) and collagen used as indexes for angiogenesis, neutrophil and macrophage accumulation and extracellular matrix deposition, respectively. Relevant inflammatory, angiogenic and fibrogenic cytokines were also determined. Strychnine treatment attenuated the main components of the fibrovascular tissue, wet weight, vascularization (Hb content), macrophage recruitment (NAG activity), collagen deposition and the levels of vascular endothelial growth factor (VEGF), tumour necrosis factor (TNF)-α and transforming growth factor (TGF-β). A regulatory function of strychnine on multiple parameters of main components of inflammatory angiogenesis has been revealed giving insight into the potential therapeutic underlying the actions of strychnine.

Biomarkers of epithelial-mesenchymal transition in squamous cell carcinoma

An understanding of the process by which tumor cells destroy the basement membrane of the surface epithelium, invade, and metastasize is essential to the development of novel treatment of head and neck squamous cell carcinoma (HNSCC). In recent years, there has been increased interest in the role of epithelial-mesenchymal transition (EMT) in invasion. EMT is a process that describes the development of motile, mesenchymal-like cells from non-motile parent epithelial cells. There are 3 known types of EMT that mediate development, wound healing, and carcinogenesis. This review summarizes studies of known EMT biomarkers in the context of HNSCC progression. The biomarkers discussed come from a wide range of proteins, including cell-surface proteins (E-cadherin, N-cadherin, and Integrins), cytoskeletal proteins (α-Smooth Muscle Actin, Vimentin, and β-catenin), extracellular matrix proteins (Collagens, Fibronectin, and Laminin), and transcription factors (SNAIL1, SNAIL2, TWIST, and LEF-1). Overall, the findings of these studies suggest that EMT mediates HNSCC progression. The mechanistic role of the EMT markers that have been associated with HNSCC should be more clearly defined if new anti-HNSCC therapies to block EMT progression are to be developed.

Cancer-associated-fibroblasts and tumour cells: a diabolic liaison driving cancer progression

Several recent papers have now provided compelling experimental evidence that the progression of tumours towards a malignant phenotype does not depend exclusively on the cell-autonomous properties of cancer cells themselves but is also deeply influenced by tumour stroma reactivity, thereby undergoing a strict environmental control. Tumour microenvironmental elements include structural components such as the extracellular matrix or hypoxia as well as stromal cells, either resident cells or recruited from circulating precursors, as macrophages and other inflammatory cells, endothelial cells and cancer-associated fibroblasts (CAFs). All these elements synergistically play a specific role in cancer progression. This review summarizes our current knowledge on the role of CAFs in tumour progression, with a particular focus on the biunivocal interplay between CAFs and cancer cells leading to the activation of the epithelial-mesenchymal transition programme and the achievement of stem cell traits, as well as to the metabolic reprogramming of both stromal and cancer cells. Recent advances on the role of CAFs in the preparation of metastatic niche, as well as the controversial origin of CAFs, are discussed in light of the new emerging therapeutic implications of targeting CAFs.

Osteomimicry of mammary adenocarcinoma cells in vitro; increased expression of bone matrix proteins and proliferation within a 3D collagen environment

Bone is the most common site of metastasis for breast cancer, however the reasons for this remain unclear. We hypothesise that under certain conditions mammary cells possess osteomimetic capabilities that may allow them to adapt to, and flourish within, the bone microenvironment. Mammary cells are known to calcify within breast tissue and we have recently reported a novel in vitro model of mammary mineralization using murine mammary adenocarcinoma 4T1 cells. In this study, the osteomimetic properties of the mammary adenocarcinoma cell line and the conditions required to induce mineralization were characterized extensively. It was found that exogenous organic phosphate and inorganic phosphate induce mineralization in a dose dependent manner in 4T1 cells. Ascorbic acid and dexamethasone alone have no effect. 4T1 cells also show enhanced mineralization in response to bone morphogenetic protein 2 in the presence of phosphate supplemented media. The expression of several bone matrix proteins were monitored throughout the process of mineralization and increased expression of collagen type 1 and bone sialoprotein were detected, as determined by real-time RT-PCR. In addition, we have shown for the first time that 3D collagen glycosaminoglycan scaffolds, bioengineered to represent the bone microenvironment, are capable of supporting the growth and mineralization of 4T1 adenocarcinoma cells. These 3D scaffolds represent a novel model system for the study of mammary mineralization and bone metastasis. This work demonstrates that mammary cells are capable of osteomimicry, which may ultimately contribute to their ability to preferentially metastasize to, survive within and colonize the bone microenvironment.

The rationale for targeting the LOX family in cancer

The therapeutic targeting of extracellular proteins is becoming hugely attractive in light of evidence implicating the tumour microenvironment as pivotal in all aspects of tumour initiation and progression. Members of the lysyl oxidase (LOX) family of proteins are secreted by tumours and are the subject of much effort to understand their roles in cancer. In this Review we discuss the roles of members of this family in the remodelling of the tumour microenvironment and their paradoxical roles in tumorigenesis and metastasis. We also discuss how targeting this family of proteins might lead to a new avenue of cancer therapeutics.

The extracellular matrix: a dynamic niche in cancer progression

The local microenvironment, or niche, of a cancer cell plays important roles in cancer development. A major component of the niche is the extracellular matrix (ECM), a complex network of macromolecules with distinctive physical, biochemical, and biomechanical properties. Although tightly controlled during embryonic development and organ homeostasis, the ECM is commonly deregulated and becomes disorganized in diseases such as cancer. Abnormal ECM affects cancer progression by directly promoting cellular transformation and metastasis. Importantly, however, ECM anomalies also deregulate behavior of stromal cells, facilitate tumor-associated angiogenesis and inflammation, and thus lead to generation of a tumorigenic microenvironment. Understanding how ECM composition and topography are maintained and how their deregulation influences cancer progression may help develop new therapeutic interventions by targeting the tumor niche.

Multistage nanoparticles for improved delivery into tumor tissue

The enhanced permeability and retention (EPR) effect has been a key rationale for the development of nanoscale carriers to solid tumors. As a consequence of EPR, nanotherapeutics are expected to improve drug and detection probe delivery, have less adverse effects than conventional chemotherapy, and thus result in improved detection and treatment of tumors. Physiological barriers posed by the abnormal tumor microenvironment, however, can hinder the homogeneous delivery of nanomedicine in amounts sufficient to eradicate cancer. To effectively enhance the therapeutic outcome of cancer patients by nanotherapeutics, we have to find ways to overcome these barriers. One possibility is to exploit the abnormal tumor microenvironment for selective and improved delivery of therapeutic agents to tumors. Recently, we proposed a multistage nanoparticle delivery system as a potential means to enable uniform delivery throughout the tumor and improve the efficacy of anticancer therapy. Here, we describe the synthesis of a novel multistage nanoparticle formulation that shrinks in size once it enters the tumor interstitial space to optimize the delivery to tumors as well as within tumors. Finally, we provide detailed experimental methods for the characterization of such nanoparticles.

MT1-MMP protects breast carcinoma cells against type I collagen-induced apoptosis

As invading breast carcinoma cells breach their underlying basement membrane, they become confronted with a dense three-dimensional reactive stroma dominated by type I collagen. To develop metastatic capabilities, invading tumor cells must acquire the capacity to negotiate this novel microenvironment. Collagen influences the fate of epithelial cells by inducing apoptosis. However, the mechanisms used by invading tumor cells to evade collagen-induced apoptosis remain to be defined. We demonstrate that membrane type-1 matrix metalloproteinase (MT1-MMP/MMP-14) confers breast cancer cells with the ability to escape apoptosis when embedded in a collagen gel and after orthotopic implantation in vivo. In the absence of MMP-14-dependent proteolysis, type I collagen triggers apoptosis by inducing the expression of the pro-apoptotic Bcl-2-interacting killer in luminal-like breast cancer cells. These findings reveal a new mechanism whereby MMP-14 activity promotes tumor progression by circumventing apoptosis.