Stromal fibroblasts in colorectal liver metastases originate from resident fibroblasts and generate an inflammatory microenvironment

Cancer-associated stromal fibroblasts (CAFs) are the main cellular constituents of reactive stroma in primary and metastatic cancer. We analyzed phenotypical characteristics of CAFs from human colorectal liver metastases (CLMs) and their role in inflammation and cancer progression. CAFs displayed a vimentin(+), alpha-smooth-muscle actin(+), and Thy-1(+) phenotype similar to resident portal-located liver fibroblasts (LFs). We demonstrated that CLMs are inflammatory sites showing stromal expression of interleukin-8 (IL-8), a chemokine related to invasion and angiogenesis. In vitro analyses revealed a striking induction of IL-8 expression in CAFs and LFs by tumor necrosis factor-alpha (TNF-alpha). The effect of TNF-alpha on CAFs is inhibited by the nuclear factor-kappaB inhibitor parthenolide. Conditioned medium of CAFs and LFs similarly stimulated the migration of DLD-1, Colo-678, HuH7 carcinoma cells, and human umbilical vein endothelial cells in vitro. Pretreatment of CAFs with TNF-alpha increased the chemotaxis of Colo-678 colon carcinoma cells by conditioned medium of CAFs; however, blockage of IL-8 activity showed no inhibitory effect. In conclusion, these data raise the possibility that the majority of CAFs in CLM originate from resident LFs. TNF-alpha-induced up-regulation of IL-8 via nuclear factor-kappaB in CAFs is an inflammatory pathway, potentially permissive for cancer invasion that may represent a novel therapeutic target.     

Clinical and functional significance of loss of caveolin-1 expression in breast cancer-associated fibroblasts

Loss of caveolin-1 (Cav-1) expression in breast cancer-associated fibroblasts (CAFs) is predictive of poor prognosis in breast cancer, but its function has not been established. Our study tested the hypotheses that loss of Cav-1 expression in breast fibroblasts was associated with poor prognosis in breast cancer, through promotion of breast cancer cell invasion. Cav-1 stromal expression was immunohistochemically assessed in 358 breast cancers. Cav-1 expression in primary breast fibroblasts was analysed by western blot. Modified Boyden chamber assays determined fibroblast ability to promote invasion of breast cancer cells. The impact of siRNA silencing of Cav-1 in fibroblasts was evaluated using invasion assays and 3D co-culture assays. Loss of Cav-1 expression in breast stroma was significantly associated with decreased breast cancer-specific and disease-free survival (p = 0.01). Mean survival was 72 months (Cav-1(+) group) versus 29.5 months (Cav-1(-) group). This was confirmed in multivariate analysis. Cav-1 expression was significantly decreased in CAFs compared to normal fibroblasts (p = 0.01) and was associated with increased invasion-promoting capacity. Cav-1 siRNA-treated fibroblasts promoted significantly increased invasion of MDA-MB-468 and T47D breast cancer cells from 27% (control) to 67% (p = 0.006) and from 37% to 56%, respectively (p = 0.01). 3D co-cultures of MDA-MB-468 cells with myoepithelial cells led to the formation of organized cohesive structures when cultured with conditioned media from fibroblasts but resulted in a disorganized appearance in the presence of conditioned media from Cav-1 siRNA-treated fibroblasts, accompanied by loss of E-cadherin expression in tumour cells. Our data confirm that loss of stromal Cav-1 in breast cancer predicts poor outcome. At a functional level, Cav-1-deficient CAFs are capable of significantly increasing the invasive capacity of breast cancer cells.     

Colorectal cancer cells activate adjacent fibroblasts resulting in FGF1/FGFR3 signaling and increased invasion

Cancer-associated fibroblasts expressing fibroblast activation protein (FAP) have been implicated in the invasive behavior of colorectal cancer. In this study, we use FAP expression as a marker of fibroblast activation and analyze the effect of activated fibroblasts on colorectal cancer migration and invasion in experimental cell studies. We also investigated the expression pattern of FAP in cancer-associated fibroblasts during transformation from benign to malignant colorectal tumors. In immunohistochemical analyses, FAP was expressed in fibroblasts in all colorectal cancer samples examined, whereas all normal colon, hyperplastic polyps, or adenoma samples were negative. In in vitro studies, conditioned medium from colon cancer cells, but not adenoma cells, activated fibroblasts by inducing FAP expression. These activated fibroblasts increased the migration and invasion of colon cancer cells in Boyden chamber experiments and in a three-dimensional cell culture model. We identify fibroblast growth factor 1/fibroblast growth factor receptor 3 (FGF1/FGFR-3) signaling as mediators leading to the increased migration and invasion. Activated fibroblasts increase their expression of FGF1, and by adding a fibroblast growth factor receptor inhibitor, as well as an FGF1-neutralizing antibody, we reduced the migration of colon cancer cells. Our findings provide evidence of a possible molecular mechanism involved in the cross talk between cancer cells and fibroblasts leading to cancer cell invasion.     

Cancer as a tissue: The significance of cancer‐stromal interactions in the development,morphogenesis and progression of human upper digestive tract cancer

We review the significance of cancer‐stromal interactions (CSIs) in the development, morphogenesis and progression of human gastric and esophageal cancer based on the data obtained from co‐culture experiments. Orthotopic fibroblasts in the gastric cancer stroma not only promoted their growth by cancer cells but were also responsible for the mobility, morphogenesis and epithelial‐to‐mesenchymal transition (EMT) of the cancer cells through CSI. Bone marrow‐derived mesenchymal stem cells could be part of the origin of cancer‐associated fibroblasts (CAFs) of the gastric cancer providing an advantageous microenvironment for the restoration of cancer stem cells with the induction of the EMT. Tumor‐associated macrophages (TAMs) may differentiate from bone marrow‐derived monocytes/macrophages within the tumor microenvironment of esophageal cancer and participate in the growth and the progression of esophageal squamous cell carcinomas (ESCCs). Macrophages infiltrated into the intraepithelial neoplastic lesions of the esophagus may function as a biological promoter by promoting the growth and motility of squamous epithelia. Tumor cells build up “cancer as a tissue” by taking advantage of the existing network of growth factors, cytokines and chemokines through the interactions of TAMs, CAFs and cancer cells themselves.     

MiR‐26b is down‐regulated in carcinoma‐associated fibroblasts from ER‐positive breast cancers leading to enhanced cell migration and invasion

Carcinoma‐associated fibroblasts (CAFs) influence the behaviour of cancer cells but the roles of microRNAs in this interaction are unknown. We report microRNAs that are differentially expressed between breast normal fibroblasts and CAFs of oestrogen receptor‐positive cancers, and explore the influences of one of these, miR‐26b, on breast cancer biology. We identified differentially expressed microRNAs by expression profiling of clinical samples and a tissue culture model: miR‐26b was the most highly deregulated microRNA. Using qPCR, miR‐26b was confirmed as down‐regulated in fibroblasts from 15 of 18 further breast cancers. Next, we examined whether manipulation of miR‐26b expression changed breast fibroblast behaviour. Reduced miR‐26b expression caused fibroblast migration and invasion to increase by up to three‐fold in scratch‐closure and trans‐well assays. Furthermore, in co‐culture with MCF7 breast cancer epithelial cells, fibroblasts with reduced miR‐26b expression enhanced both MCF7 migration in trans‐well assays and MCF7 invasion from three‐dimensional spheroids by up to five‐fold. Mass spectrometry was used to identify expression changes associated with the reduction of miR‐26b expression in fibroblasts. Pathway analyses of differentially expressed proteins revealed that glycolysis/TCA cycle and cytoskeletal regulation by Rho GTPases are downstream of miR‐26b. In addition, three novel miR‐26b targets were identified (TNKS1BP1, CPSF7, COL12A1) and the expression of each in cancer stroma was shown to be significantly associated with breast cancer recurrence. MiR‐26b in breast CAFs is a potent regulator of cancer behaviour in oestrogen receptor‐positive cancers, and we have identified key genes and molecular pathways that act downstream of miR‐26b in CAFs. © 2013 The Authors. Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.     

Messenger RNA for two type IV collagenases is located in stromal cells in human colon cancer.

The gene expression of two type IV collagen-degrading enzymes (72-kd and 92-kd type IV collagenases) was investigated in human colon adenocarcinomas by in situ hybridization. In all cases (18 out of 18), messenger RNA for the 72-kd type IV collagenase was present and located in numerous fibroblasts in the stroma surrounding the invasive cancer tissue. In normal-appearing colonic mucosa distant from the cancer tissue, either no expression or only very weak expression of this enzyme was detected. Also the 92-kd type IV collagenase was found in all samples investigated (10 out of 10), exclusively expressed by tissue macrophages. A very strong hybridization signal for messenger RNA for the 92-kd enzyme was found in a subpopulation of tissue macrophages surrounding invading malignant epithelium. In normal-appearing colon tissue, a markedly weaker hybridization signal was observed in macrophages contained in Peyer's patches. No hybridization signals for either of the two type IV collagenases were detected in cancer cells. Together with previous findings on expression of components of the plasminogen activation system, these results indicate that several nonepithelial cell types in the tumor stroma are involved in production of factors involved in extracellular proteolysis during colon cancer invasion.     

Effects of the fibroblast activation protein on the invasion and migration of gastric cancer

Objective

Cancer-associated fibroblasts (CAFs) are one of the most important components of tumor microenvironment. CAFs are believed to play an important role in tumor invasion and metastasis. Recently, fibroblast activation protein (FAP), a type II integral membrane glycoprotein belonging to the serine protease family, has emerged as a specific marker of CAFs. FAP was overexpressed in stromal fibroblasts of solid malignancies, however, the role of FAP on the process of invasion and metastasis of gastric carcinomas is still unknown.

Methods

Expression of FAP level was detected by immunohistochemistry in 60 gastric cancer surgical specimens (28 with omentum metastasis and 32 without), 20 normal human gastric tissues and omentum of 10 non-neoplastic gastric diseases. Fibroblasts were isolated from patient's tissues in the distal normal zones and tumor zones respectively, which were correspondingly designated as normal zone fibroblasts (NFs) and cancer-associated fibroblasts (CAFs). To explore the effects of FAP on NFs or CAFs, fibroblasts were co-cultured with human gastric cancer cell line MGC-803 cells. The ability of invasion and migration of MGC-803 cells was evaluated after transfecting FAP siRNA into CAFs of gastric carcinomas.

Results

We investigated the level of expression of FAP in surgical specimens, and found overexpressed in CAFs and non-expressed in NFs. Expression of FAP level in CAFs is significantly associated with Lauren classification, the degree of differentiation, depth of tumor invasion and TNM stage, but it is not correlated to age and gender in gastric carcinoma patients. There was positive correlation between the FAP level with metastasis to the omentum (p < 0.05, R² = 0.2736, p < 0.05, R² = 0.1479). In addition, the invasion and migration abilities of MGC-803 cells were significantly increased when cells were co-cultured with CAFs. On the other hand, invasion and migration abilities were significantly decreased by 46.9 and 50.3%, respectively, after knocking down FAP in CAFs. Further, NFs did not have appreciable effect on the invasion and migration of MGC-803 cells.

Conclusions

Our findings showed that FAP was overexpressed in CAFs of gastric carcinomas, and siRNA-mediated knock down of FAP significantly suppressed invasion and migration of MGC-803 cells. FAP may be an important regulator in the invasion and migration of gastric cancer and may provide a novel therapeutic target in gastric carcinomas.     

Concordant podoplanin expression in cancer-associated fibroblasts and tumor cells is an adverse prognostic factor in esophageal squamous cell carcinoma

There is growing evidence that cancer-associated fibroblasts (CAFs) interact with tumor cells and play important roles in tumor progression and invasion. Podoplanin is a type-1 transmembrane glycoprotein expressed in a variety of normal human tissues, including lymphatic endothelium. Tumor cell expression of podoplanin correlates with nodal metastasis and poor prognosis in squamous cell carcinoma (SCC) of oral cavity and esophagus. Recently, podoplanin-positive CAFs have been shown to exert adverse or beneficial prognostic effect on different cancer types. However, the significance of podoplanin-positive CAFs in esophageal SCC has not been investigated. This is the first study to investigate podoplanin expression in CAFs and tumor cells by immunohistochemistry in 59 cases of surgically resected esophageal SCC. We found significant association of podoplanin expression between CAFs and tumor cells (P = 0.031). Although the abundance of podoplanin-positive CAFs per se had no prognostic effect, concordant podoplanin expression in CAFs and tumor cells (both high or both low) was strongly associated with short survival (P = 0.00088). Multivariate analysis showed that concordant podoplanin expression was the strongest independent adverse prognostic factor (hazard ratio: 3.62; 95% confidence interval: 1.69-7.77; P = 0.00094). Our data suggest that interaction between podoplanin-positive CAFs and tumor cells is important in tumor biology of esophageal SCC.     

Podoplanin expression by cancer-associated fibroblasts predicts poor outcome in invasive ductal breast carcinoma

Pula B, Jethon A, Piotrowska A, Gomulkiewicz A, Owczarek T, Calik J, Wojnar A, Witkiewicz W, Rys J, Ugorski M, Dziegiel P & Podhorska‐Okolow M
(2011) Histopathology  59, 1249–1260
Podoplanin expression by cancer‐associated fibroblasts predicts poor outcome in invasive ductal breast carcinoma Aims: It has recently been shown that podoplanin, a mucin‐type glycoprotein, is expressed by cancer cells and cancer‐associated fibroblasts (CAFs), and promotes cancer cell migration and invasiveness. The biological role of podoplanin expression in tumour stroma of invasive ductal carcinoma of the breast (IDC) has not been determined. Methods and results: Podoplanin expression was analysed in 117 cases of IDC and 27 cases of fibrocystic change, as well as in breast cancer cell lines, with the use of immunohistochemistry and real‐time polymerase chain reaction. In 82.1% of analysed tumours, podoplanin was found only in CAFs. Only two of 117 IDC cases (1.7%) were characterized by expression of this glycoprotein in cancer cells. None of the fibrocystic changes or stroma surrounding normal ducts showed podoplanin expression. Podoplanin‐positive CAFs correlated with tumour size (P = 0.0125), grade of malignancy (P = 0.0058), lymph node metastasis (P = 0.0149), lymphovascular invasion (LVI) (P = 0.0486) and Ki67 expression in cancer cells (P = 0.0128). High‐level podoplanin expression (>50% of positive stroma) in the tumour stroma was significantly associated with a negative oestrogen status (P = 0.0201). Univariate, but not multivariate, analysis showed that podoplanin expression by CAFs was associated with poor patient outcome (P = 0.0202). Conclusions: Our results suggest that podoplanin expression by CAFs could be an unfavourable prognostic marker for IDC.     

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.     

Leading malignant cells initiate collective epithelial cell invasion in a three-dimensional heterotypic tumor spheroid model

Solid tumors consist of genetically and phenotypically diverse subpopulations of cancer cells with unique capacities for growth, differentiation, and invasion. While the molecular and microenvironmental bases for heterogeneity are increasingly appreciated, the outcomes of such intratumor heterogeneity, particularly in the context of tumor invasion and metastasis, remain poorly understood. To study heterotypic cell–cell interactions and elucidate the biological consequences of intratumor heterogeneity, we developed a tissue-engineered multicellular spheroid (MCS) co-culture model that recapitulates the cellular diversity and fully three-dimensional cell–cell and cell–matrix interactions that characterize human carcinomas. We found that “invasion-competent” malignant cells induced the collective invasion of otherwise “invasion-incompetent” epithelial cells, and that these two cell types consistently exhibited distinct leader and follower roles during invasion. Analysis of extracellular matrix (ECM) microarchitecture revealed that malignant cell invasion was accompanied by extensive ECM remodeling including matrix alignment and proteolytic track-making. Inhibition of cell contractility- and proteolysis-mediated matrix reorganization prevented leader-follower behavior and malignant cell-induced epithelial cell invasion. These results indicate that heterogeneous subpopulations within a tumor may possess specialized roles during tumor progression and suggest that complex interactions among the various subpopulations of cancer cells within a tumor may regulate critical aspects of tumor biology and affect clinical outcome.     

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.     

Stromal reaction in cancer tissue: Pathophysiologic significance of the expression of matrix-degrading enzymes in relation to matrix turnover and immune/inflammatory reactions

Cancers are characterized by invasive growth and distant metastasis. Cancer cells not only destroy the pre-existing extracellular matrix, but cancer invasion per se usually induces new matrix formation by activation of stromal cells; that is, desmoplastic reaction. This process includes both matrix production and degradation; that Is, the remodeling process. The similarity between desmoplastic reactions in cancer stroma and the wound healing process has already been pointed out, and it has been well documented that matrix-degrading processes are actively involved In the wound healing process. A recent study revealed that most matrix-degrading enzymes, generally considered to be one of the main mechanisms of cancer invasion and metastasis, are originated from stromal cells. Based on these preconditions, the present review postulates that the abundant expression of matrix-degrading enzymes by fibroblasts, coupled with the abundant expression of type I procollagen, is involved in the matrix remodeling processes occurring in cancer stroma; that is, the mechanism similar to the wound healing process. Next, macrophages distributed along the invasive margin are known to express matrix-degrading enzymes/factors. Data from past studies of colon carcinoma indicate that the tissue expression of matrix metalloproteinase-9 and urokinase-type plas-mlnogen activator receptor Is inversely associated with simultaneous liver metastasis and infiltrating growth pattern. Previous clinicopathologic data have indicated that immune/Inflammatory cells are one of the factors for a favorable prognosis. This suggests that the expression of matrix-degrading enzymes/factors by these host cells may be involved in host immune/inflammatory reactions, and that the net function of these cells can be defensive towards the host. Data from past studies of colon carcinoma on the expression of the intercellular adhesion molecule-1 suggest that the interaction between macrophages, lymphocytes, and the phenotypes of venules distributed along the Invasive margin, further support the pro-inflammatory milieu there. Therefore, the matrix degradation process in cancer tissue is multifunctional: besides the Involvement in cancer invasion and metastasis, the matrix degradation process is also involved in the tissue remodeling process and in the immune/inflammatory reaction occurring in the stroma.     

EphA2-mediated mesenchymal–amoeboid transition induced by endothelial progenitor cells enhances metastatic spread due to cancer-associated fibroblasts

Tumor progression is deeply influenced by epigenetic changes induced by tumor stroma. Cancer-associated fibroblasts (CAFs) have been reported to promote epithelial–mesenchymal transition in cancer cells, thereby enhancing their aggressiveness and stem-like properties. As CAFs are able to recruit endothelial progenitor cells (EPCs) to tumor site, we aim to investigate their interplay for prostate carcinoma progression. Both prostate CAFs and cancer cells actively recruit EPCs, known to affect tumor progression through increased vasculogenesis. EPCs synergize with CAFs to further promote epigenetic plasticity of cancer cells, through a mesenchymal-to-amoeboid transition. Indeed, after fibroblasts have engaged epithelial–mesenchymal transition in cancer cells, a further shift towards amoeboid motility is promoted by EPCs through contact-mediated triggering of the bidirectional ephrinA1/EphA2 signaling. The activation of ephrinA1 reverse pathway enhances EPC-induced neo-vascularization, thus promoting tumor growth, while EphA2 forward signaling elicits mesenchymal–amoeboid transition in cancer cells, favoring their adhesion to endothelium, transendothelial migration, and lung metastatic colonization. We therefore underscore that the metastatic advantage given by tumor microenvironment embraces different motility strategies and propose EphA2-targeted tools as useful adjuvants in anti-metastatic treatments.     

成纤维细胞与结肠癌细胞相互作用促进细胞外基质金属蛋白酶诱导因子的表达

目的研究成纤维细胞与结肠癌细胞相互作用对二者表达细胞外基质金属蛋白酶诱导因子（EMMPRIN）的影响,初步探讨肿瘤-基质相互作用在结肠癌侵袭转移中的作用。方法结肠癌SW480细胞与HELF成纤维细胞以RPMI1640培养液分别共培养0、12、24、48h,通过RT-PCR和免疫细胞化学方法检测SW480和HELF细胞中EMMPRIN的表达。结果共培养组SW480细胞EMMPRINmRNA和蛋白的表达均明显升高,HELF细胞本来不表达EMMPRIN,与SW480细胞共培养12、24、48h后检测到EMMPRIN表达,且随时间延长而表达增加。结论成纤维细胞与结肠癌细胞相互作用上调SW480细胞EMMPRIN的表达,并诱导HELF细胞表达EMMPRIN,有可能在结肠癌侵袭转移中发挥重要作用。     

Cancer‐associated fibroblasts predict poor outcome and promote periostin‐dependent invasion in oesophageal adenocarcinoma

Interactions between cancer cells and cancer‐associated fibroblasts (CAFs) play an important role in tumour development and progression. In this study we investigated the functional role of CAFs in oesophageal adenocarcinoma (EAC). We used immunochemistry to analyse a cohort of 183 EAC patients for CAF markers related to disease mortality. We characterized CAFs and normal oesophageal fibroblasts (NOFs) using western blotting, immunofluorescence and gel contraction. Transwell assays, 3D organotypic culture and xenograft models were used to examine the effects on EAC cell function and to dissect molecular mechanisms regulating invasion. Most EACs (93%) contained CAFs with a myofibroblastic (α‐SMA‐positive) phenotype, which correlated significantly with poor survival [p = 0.016; HR 7. 1 (1.7–29.4)]. Primary CAFs isolated from EACs have a contractile, myofibroblastic phenotype and promote EAC cell invasion in vitro (Transwell assays, p ≤ 0.05; organotypic culture, p < 0.001) and in vivo (p ≤ 0.05). In vitro, this pro‐invasive effect is modulated through the matricellular protein periostin. Periostin is secreted by CAFs and acts as a ligand for EAC cell integrins αvβ3 and αvβ5, promoting activation of the PI3kinase–Akt pathway. In patient samples, periostin expression at the tumour cell–stromal interface correlates with poor overall and disease‐free survival. Our study highlights the importance of the tumour stroma in EAC progression. Paracrine interaction between CAF‐secreted periostin and EAC‐expressed integrins results in PI3 kinase–Akt activation and increased tumour cell invasion. Most EACs contain a myofibroblastic CAF‐rich stroma; this may explain the aggressive, highly infiltrative nature of the disease, and suggests that stromal targeting may produce therapeutic benefit in EAC patients. © 2014 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.