Quantitative analysis of three-dimensional human mammary epithelial tissue architecture reveals a role for tenascin-C in regulating c-met function

The cJUN NH2-terminal kinase (JNK) signaling pathway promotes genome stability and prevents tumor initiation

Breast cancer is the most commonly diagnosed malignancy in women. Analysis of breast cancer genomic DNA indicates frequent loss-of-function mutations in components of the cJUN NH₂-terminal kinase (JNK) signaling pathway. Since JNK signaling can promote cell proliferation by activating the AP1 transcription factor, this apparent association of reduced JNK signaling with tumor development was unexpected. We examined the effect of JNK deficiency in the murine breast epithelium. Loss of JNK signaling caused genomic instability and the development of breast cancer. Moreover, JNK deficiency caused widespread early neoplasia and rapid tumor formation in a murine model of breast cancer. This tumor suppressive function was not mediated by a role of JNK in the growth of established tumors, but by a requirement of JNK to prevent tumor initiation. Together, these data identify JNK pathway defects as ‘driver’ mutations that promote genome instability and tumor initiation.

As cells in our body grow and divide, their DNA can experience changes or damage. Most of these ‘mutations’ are harmless, or quickly fixed by the body. Yet, sometimes a mutation can trigger a chain of genetic events that drives the cells to multiply uncontrollably, which leads to tumors. Identifying these ‘driver mutations’ is complex, but key to understanding how cancers start and can be fought.

Breast cancer is the most common type of cancer diagnosed in women worldwide. Large studies have focused on sequencing the DNA of cancerous breast cells to try to identify the mutations that started the cancer. Results show that, in these cells, a biological mechanism called the JNK signaling pathway is often inactivated because mutations affect the molecules that take part in this process. Like a chain reaction, the proteins of the JNK pathway act on each other until the last one, called JNK, gets switched on. This protein then goes on to participate in a number of cellular processes such as DNA repair. Is it possible that mutations in this pathway actually drive cancer, and if so, how?

Girnius et al. addressed these questions by inactivating the JNK pathway in the breast cells of mice. Over the next year and a half, the JNK-deficient animals were more likely to get breast cancer than normal mice. Further experiments showed that, in breast cells, the JNK protein prevented tumors from appearing. However, once the tumors were present, it was less effective at stopping them from growing. The DNA of the breast cancer cells with no JNK protein also contained more genetic changes and mistakes. This suggests that the JNK signaling pathway helps to keep the genetic information ‘healthy’. This may be because, normally, the JNK protein activates processes that fix DNA mutations. Taken together, the results presented by Girnius et al. show that genetic changes which inactivate the JNK pathway can drive the development of breast cancer.

Certain anti-cancer drugs kill cancerous cells by damaging their DNA. Breast tumor cells with inactive JNK pathways are less able to repair their genetic information, and so these drugs could potentially work well on them. Future experiments will be needed to test this hypothesis.

Progressive polarity loss and luminal collapse disrupt tissue organization in carcinoma

Epithelial cancers (carcinoma) account for 80%-90% of all cancers. The development of carcinoma is associated with disrupted epithelial organization and solid ductal structures. The mechanisms underlying the morphological development of carcinoma are poorly understood, but it is thought that loss of cell polarity is an early event. Here we report the characterization of the development of human breast lesions leading to carcinoma. We identified a unique mechanism that generates solid ducts in carcinoma through progressive loss of polarity and collapse of the luminal architecture. This program initiates with asymmetric divisions of polarized cells that generate a stratified epithelium containing both polarized and depolarized cells. Stratified regions form cords that penetrate into the lumen, subdividing it into polarized secondary lumina. The secondary lumina then collapse with a concomitant decrease in RhoA and myosin II activity at the apical membrane and ultimately lose apical-basal polarity. By restoring RhoA activity in mice, ducts maintained lumen and cell polarity. Notably, disrupted tissue architecture through luminal collapse was reversible, and ducts with a lumen were re-established after oncogene suppression in vivo. This reveals a novel and common mechanism that contributes to carcinoma development by progressively disrupting cell and tissue organization.

Tenascin-C: Exploitation and collateral damage in cancer management

Despite an increasing knowledge about the causes of cancer, this disease is difficult to cure and still causes far too high a death rate. Based on advances in our understanding of disease pathogenesis, novel treatment concepts, including targeting the tumor microenvironment, have been developed and are being combined with established treatment regimens such as surgical removal and radiotherapy. Yet it is obvious that we need additional strategies to prevent tumor relapse and metastasis. Given its exceptional high expression in most cancers with low abundance in normal tissues, tenascin-C appears an ideal candidate for tumor treatment. Here, we will summarize the current applications of targeting tenascin-C as a treatment for different tumors, and highlight the potential of this therapeutic approach.

3-D Tissue Modelling and Virtual Pathology as New Approaches to Study Ductal Carcinoma In Situ

Widespread screening mammography programmes mean that ductal carcinoma in situ (DCIS), a pre-invasive breast lesion, is now more frequently diagnosed. However, not all diagnosed DCIS lesions progress to invasive breast cancer, which presents a dilemma for clinicians. As such, there is much interest in studying DCIS in the laboratory, in order to help understand more about its biology and determine the characteristics of those that progress to invasion. Greater knowledge would lead to targeted and better DCIS treatment. Here, we outline some of the models available to study DCIS, with a particular focus on animal-free systems.

Breast cancer cell behaviors on staged tumorigenesis-mimicking matrices derived from tumor cells at various malignant stages

Extracellular matrix (ECM) has been focused to understand tumor progression in addition to the genetic mutation of cancer cells. Here, we prepared "staged tumorigenesis-mimicking matrices" which mimic in vivo ECM in tumor tissue at each malignant stage to understand the roles of ECM in tumor progression. Breast tumor cells, MDA-MB-231 (invasive), MCF-7 (non-invasive), and MCF-10A (benign) cells, were cultured to form their own ECM beneath the cells and formed ECM was prepared as staged tumorigenesis-mimicking matrices by decellularization treatment. Cells showed weak attachment on the matrices derived from MDA-MB-231 cancer cells. The proliferations of MDA-MB-231 and MCF-7 was promoted on the matrices derived from MDA-MB-231 cancer cells whereas MCF-10A cell proliferation was not promoted. MCF-10A cell proliferation was promoted on the matrices derived from MCF-10A cells. Chemoresistance of MDA-MB-231 cells against 5-fluorouracil increased on only matrices derived from MDA-MB-231 cells. Our results showed that the cells showed different behaviors on staged tumorigenesis-mimicking matrices according to the malignancy of cell sources for ECM preparation. Therefore, staged tumorigenesis-mimicking matrices might be a useful in vitro ECM models to investigate the roles of ECM in tumor progression.

Rat mammary extracellular matrix composition and response to ibuprofen treatment during postpartum involution by differential GeLC-MS/MS analysis

Breast cancer patients diagnosed within five years following pregnancy have increased metastasis and decreased survival. A hallmark of postpartum biology that may contribute to this poor prognosis is mammary gland involution, involving massive epithelial cell death and dramatic stromal remodeling. Previous studies show pro-tumorigenic properties of extracellular matrix (ECM) isolated from rodent mammary glands undergoing postpartum involution. More recent work demonstrates systemic ibuprofen treatment during involution decreases its tumor-promotional nature. Utilizing a proteomics approach, we identified relative differences in the composition of mammary ECM isolated from nulliparous rats and those undergoing postpartum involution, with and without ibuprofen treatment. GeLC-MS/MS experiments resulted in 20327 peptide identifications that mapped to 884 proteins with a <0.02% false discovery rate. Label-free quantification yielded several ECM differences between nulliparous and involuting glands related to collagen-fiber organization, cell motility and attachment, and cytokine regulation. Increases in known pro-tumorigenic ECM proteins osteopontin, tenascin-C, and laminin-α1 and pro-inflammatory proteins STAT3 and CD68 further identify candidate mediators of breast cancer progression specific to the involution window. With postpartum ibuprofen treatment, decreases in tenascin-C and three laminin chains were revealed. Our data suggest novel ECM mediators of breast cancer progression and demonstrate a protective influence of ibuprofen on mammary ECM composition.

How do tenascins influence the birth and life of a malignant cell?

Tenascins are large glycoproteins found in embryonic and adult extracellular matrices. Of the four family members, two have been shown to be overexpressed in the microenvironment of solid tumours: tenascin-C and tenascin-W. The regular presence of these proteins in tumours suggests a role in tumourigenesis, which has been investigated intensively for tenascin-C and recently for tenascin-W as well. In this review, we follow a malignant cell starting from its birth through its potential metastatic journey and describe how tenascin-C and tenascin-W contribute to these successive steps of tumourigenesis. We consider the importance of the mechanical aspect in tenascin signalling. Furthermore, we discuss studies describing tenascin-C as an important component of stem cell niches and present examples reporting its role in cancer therapy resistance.

The role of cancer-associated myofibroblasts in intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma is typically characterized by a dense desmoplastic stroma, of which cancer-associated myofibroblasts (which express α-smooth muscle actin), are a major cellular component. These stromal myofibroblasts have a crucial role in accelerating the progression of intrahepatic cholangiocarcinoma and in promoting resistance to therapy through interactive autocrine and paracrine signaling pathways that promote malignant cell proliferation, migration, invasiveness, apoptosis resistance and/or epithelial-mesenchymal transition. These changes correlate with aggressive tumor behavior. Hypoxic desmoplasia and aberrant Hedgehog signaling between stromal myofibroblastic cells and cholangiocarcinoma cells are also critical modulators of intrahepatic cholangiocarcinoma progression and therapy resistance. A novel strategy has been developed to achieve improved therapeutic outcomes in patients with advanced intrahepatic cholangiocarcinoma, based on targeting of multiple interactive pathways between cancer-associated myofibroblasts and intrahepatic cholangiocarcinoma cells that are associated with disease progression and poor survival. Unique organotypic cell culture and orthotopic rat models of cholangiocarcinoma progression are well suited to the rapid preclinical testing of this potentially paradigm-shifting strategy.

The role of cancer-associated myofibroblasts in intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma is typically characterized by a dense desmoplastic stroma, of which cancer-associated myofibroblasts (which express α-smooth muscle actin), are a major cellular component. These stromal myofibroblasts have a crucial role in accelerating the progression of intrahepatic cholangiocarcinoma and in promoting resistance to therapy through interactive autocrine and paracrine signaling pathways that promote malignant cell proliferation, migration, invasiveness, apoptosis resistance and/or epithelial-mesenchymal transition. These changes correlate with aggressive tumor behavior. Hypoxic desmoplasia and aberrant Hedgehog signaling between stromal myofibroblastic cells and cholangiocarcinoma cells are also critical modulators of intrahepatic cholangiocarcinoma progression and therapy resistance. A novel strategy has been developed to achieve improved therapeutic outcomes in patients with advanced intrahepatic cholangiocarcinoma, based on targeting of multiple interactive pathways between cancer-associated myofibroblasts and intrahepatic cholangiocarcinoma cells that are associated with disease progression and poor survival. Unique organotypic cell culture and orthotopic rat models of cholangiocarcinoma progression are well suited to the rapid preclinical testing of this potentially paradigm-shifting strategy.

Advances in tenascin-C biology

Tenascin-C is an extracellular matrix glycoprotein that is specifically and transiently expressed upon tissue injury. Upon tissue damage, tenascin-C plays a multitude of different roles that mediate both inflammatory and fibrotic processes to enable effective tissue repair. In the last decade, emerging evidence has demonstrated a vital role for tenascin-C in cardiac and arterial injury, tumor angiogenesis and metastasis, as well as in modulating stem cell behavior. Here we highlight the molecular mechanisms by which tenascin-C mediates these effects and discuss the implications of mis-regulated tenascin-C expression in driving disease pathology.

Cancer-associated fibroblasts in intrahepatic cholangiocarcinoma

PURPOSE OF REVIEW

The aim of this brief review is to provide an up-to-date view of the role played by α-smooth muscle actin-positive cancer-associated fibroblastic cells in promoting intrahepatic cholangiocarcinoma progression.

RECENT FINDINGS

An increase in α-smooth muscle actin-positive cancer-associated fibroblastic cells in the stroma of intrahepatic cholangiocarcinoma has recently been demonstrated to accelerate cholangiocarcinoma progression. However, our understanding of the evolving cellular and molecular interactions between these stromal cells and cholangiocarcinoma cells in relation to promoting intrahepatic cholangiocarcinoma progression is only just beginning to be elucidated. Imbalances in multifactorial growth factor/cytokine signaling, activation of Hedgehog-GLI signaling and of proteases involved in extracellular matrix remodeling, and matricellular protein-protein and protein-cholangiocarcinoma cell interactions, as well as hypoxia, all appear to factor into the complex and dynamic interactive mechanisms through which cancer-associated fibroblastic cells crosstalk with cholangiocarcinoma cells to promote intrahepatic cholangiocarcinoma progression. Novel three-dimensional organotypic co-culture models are being developed to facilitate relevant studies of cancer-associated fibroblastic cell/cholangiocarcinoma cell interactions that may more accurately mimic physiologically pertinent features of the tumor.

SUMMARY

Increasing our understanding of critical interactive pathways by which cancer-associated fibroblastic cells crosstalk with cholangiocarcinoma cells to promote tumor progression can lead to the development of novel multitargeting strategies for intrahepatic cholangiocarcinoma therapy.

Tenascin-C triggers fibrin accumulation by downregulation of tissue plasminogen activator

We explored novel functions of tenascin-C by comparing mouse embryonic fibroblasts (MEFs) proficient or deficient in tenascin-C expression. Transcript profiling analysis identified tissue plasminogen activator (tPA) as the most consistently over-expressed gene in all tenascin-C deficient MEFs. This was confirmed by real-time PCR as well as by protein expression analysis. In agreement with these observations, tenascin-C deficient MEFs had an increased capacity to digest fibrin in situ. Consistently, tenascin-C expression in vivo was found to correlate with fibrin deposition in several diseases associated with tenascin-C overexpression such as fibrosis, asthma and cancer. In conclusion, the present study suggests a new role of tenascin-C as a regulator of the fibrinolytic system.

Expression of tenascin-C and its isoforms in the breast

Tenascin-C (TNC) is an extracellular matrix glycoprotein which is frequently up-regulated in a variety of pathological conditions including chronic inflammation and cancer. TNC has been implicated in the modulation of cell migration, proliferation, invasion and angiogenesis. Multiple isoforms of TNC can be generated through the alternative splicing of nine exons located in the fibronectin type III region of the molecule. The profile of isoforms expressed differs between cancers and normal breast, with the fully truncated TNC isoform being predominant in normal and benign tissues and higher molecular weight isoforms induced predominantly in cancer. The addition of extra domains within the fibronectin type III repeat domain greatly affects TNC function with multiple exon combinations available for splicing. Exons 14 and 16 are considered to be tumour-associated and have been shown to affect breast cell line invasion and growth in vitro to a greater extent than the full-length TNC isoform. This mini review will provide a summary of the literature to date regarding the expression of TNC isoforms in the breast and also discuss more recent developments in the field regarding exon AD1.

Microsomal prostaglandin e2 synthase-1 modulates the response to vascular injury

BACKGROUND

Microsomal (m) prostaglandin (PG) E₂ synthase (S)-1 catalyzes the formation of PGE₂ from PGH₂, a cyclooxygenase product that is derived from arachidonic acid. Previous studies in mice suggest that targeting mPGES-1 may be less likely to cause hypertension or thrombosis than cyclooxygenase-2-selective inhibition or deletion in vivo. Indeed, deletion of mPGES-1 retards atherogenesis and angiotensin II-induced aortic aneurysm formation. The role of mPGES-1 in the response to vascular injury is unknown.

METHODS AND RESULTS

Mice were subjected to wire injury of the femoral artery. Both neointimal area and vascular stenosis were significantly reduced 4 weeks after injury in mPGES-1 knockout mice compared with wild-type controls (65.6 ± 5.7 versus 37.7 ± 5.1 × 10³ pixel area and 70.5 ± 13.4% versus 47.7 ± 17.4%, respectively; P < 0.01). Induction of tenascin-C, a proproliferative and promigratory extracellular matrix protein, after injury was attenuated in the knockouts. Consistent with in vivo rediversion of PG biosynthesis, mPGES-1-deleted vascular smooth muscle cells generated less PGE₂ but more PGI₂ and expressed reduced tenascin-C compared with wild-type cells. Both suppression of PGE₂ and augmentation of PGI₂ attenuate tenascin-C expression and vascular smooth muscle cell proliferation and migration in vitro.

CONCLUSIONS

Deletion of mPGES-1 in mice attenuates neointimal hyperplasia after vascular injury, in part by regulating tenascin-C expression. This raises for consideration the therapeutic potential of mPGES-1 inhibitors as adjuvant therapy for percutaneous coronary intervention.