Summary E-cadherin is a single-pass transmembrane protein that mediates homophilic cell-cell interactions. Tumour progression is often associated with the loss of E-cadherin function and the transition to a more motile and invasive phenotype. This requires the coordinated regulation of both E-cadherin-mediated cell-cell adhesions and integrin-mediated adhesions that contact the surrounding extracellular matrix (ECM). Regulation of both types of adhesion is dynamic as cells respond to external cues from the tumour microenvironment that regulate polarity, directional migration and invasion. Here, we review the mechanisms by which tumour cells control the crossregulation between dynamic E-cadherin-mediated cell-cell adhesions and integrin-mediated cell-matrix contacts, which govern the invasive and metastatic potential of tumours. In particular, we will discuss the role of the adhesion-linked kinases Src, focal adhesion kinase (FAK) and integrin-linked kinase (ILK), and the Rho family of GTPases. Key words: E-cadherin, Integrins, Cancer, Invasion Introduction Understanding the processes by which tumour cells invade and metastasise to distant sites (and how to target them), is one of the great challenges in cancer research, as metastatic spread is responsible for ,90% of cancer-related mortality. Tumour cell invasion and metastasis is a complex process that involves multiple steps, including local migration and invasion, dissemination of malignant tumour cells through the lymphatic or haematogenous systems, and the resulting growth or colonization of micrometastatic lesions and their development into macro-metastases. In common with other 'hallmarks' of cancer (Hanahan and Weinberg, 2011), understanding and inhibiting invasion and metastasis are complicated by the multiplicity of underlying mechanisms, the plasticity of cancer cell behaviour and the evolving nature of the microenvironment. One trait that underpins the ability of cancer cells to metastasise is their ability to change the way in which they interact with the surrounding ECM and with adjacent tumour and stromal cells. E-cadherin is a key mediator of cell-cell adhesions in epithelial tissues, and loss of E-cadherin can promote invasive and metastatic behaviour in many epithelial tumours (Birchmeier and Behrens, 1994). However, it is clear that tumour cells can invade with fully intact and functional cell-cell adhesions as collective groups of cells, and that a loosening of cell-cell contacts is sufficient to permit this collective migration and invasion. This requires coordination of cues from the surrounding tumour environment, to regulate both cell-cell and cell-ECM interactions. Here, we review the role of E-cadherin in tumour cell invasion and metastasis, with particular emphasis on the interplay between E-cadherin and cell-ECM interactions that are mediated by integrin matrix receptors. We discuss the key signalling intermediates that regulate this crosstalk, as well as recent work that supports a physical interaction between integrin-and E-cadherin-

SummaryFocal adhesion kinase (FAK) promotes anti-tumor immune evasion. Specifically, the kinase activity of nuclear-targeted FAK in squamous cell carcinoma (SCC) cells drives exhaustion of CD8+ T cells and recruitment of regulatory T cells (Tregs) in the tumor microenvironment by regulating chemokine/cytokine and ligand-receptor networks, including via transcription of Ccl5, which is crucial. These changes inhibit antigen-primed cytotoxic CD8+ T cell activity, permitting growth of FAK-expressing tumors. Mechanistically, nuclear FAK is associated with chromatin and exists in complex with transcription factors and their upstream regulators that control Ccl5 expression. Furthermore, FAK’s immuno-modulatory nuclear activities may be specific to cancerous squamous epithelial cells, as normal keratinocytes do not have nuclear FAK. Finally, we show that a small-molecule FAK kinase inhibitor, VS-4718, which is currently in clinical development, also drives depletion of Tregs and promotes a CD8+ T cell-mediated anti-tumor response. Therefore, FAK inhibitors may trigger immune-mediated tumor regression, providing previously unrecognized therapeutic opportunities.

A fundamental question in cell biology concerns how cells respond to their environment by polarizing after sensing directional cues. This requires the differential localization of protein complexes in cells, and it is important to identify and understand how these complexes function. Here we describe a novel "direction-sensing" pathway that links the integrin effector focal adhesion kinase (FAK), the molecular scaffold protein RACK1, and activity of one of its client proteins, PDE4D5, a cAMP-degrading phosphodiesterase. The complex is recruited to nascent adhesions and promotes cell polarity. We identify FAK FERM domain residues whose mutation impairs RACK1 binding. When re-expressed in cancer cells in which endogenous fak is deleted by Cre-lox-mediated recombination, the RACK1-binding-impaired FAK mutant protein does not support formation of nascent actin adhesion structures as cells spread. These cancer cells, like FAK-deficient cells, cannot undergo directional responses, including wound-induced polarization or chemotactic invasion into three-dimensional matrix gels. We show that RACK1 serves as the molecular bridge linking FAK to the recruitment of PDE4D5. FAK/RACK1/PDE4D5 is a novel 'direction-sensing' complex that acts to recruit specific components of the cAMP second-messenger system to nascent integrin adhesions and to the leading edge of polarizing cells.

Most cancer-related deaths are due to the development of metastatic disease, and several new molecularly targeted agents in clinical development have the potential to prevent disease progression. However, it remains difficult to assess the efficacy of antimetastatic agents in the clinical setting, and an increased understanding of how such agents work at different stages of the metastatic cascade is important in guiding their clinical use. We used optical window chambers combined with photobleaching, photoactivation, and photoswitching to quantitatively measure (a) tumor cell movement and proliferation by tracking small groups of cells in the context of the whole tumor, and (b) E-cadherin molecular dynamics in vivo following perturbation of integrin signaling by inhibiting focal adhesion kinase (FAK) and Src. We show that inhibition of Src and FAK suppresses E-cadherin-dependent collective cell movement in a complex three-dimensional tumor environment, and modulates cell-cell adhesion strength and endocytosis in vitro. This shows a novel role for integrin signaling in the regulation of E-cadherin internalization, which is linked to regulation of collective cancer cell movement. This work highlights the power of fluorescent, direct, in vivo imaging approaches in the preclinical evaluation of chemotherapeutic agents, and shows that inhibition of the Src/FAK signaling axis may provide a strategy to prevent tumor cell spread by deregulating E-cadherin-mediated cell-cell adhesions. Cancer Res; 70(22); 9413-22. ©2010 AACR.

The development of human malignancies can involve the aberrant regulation of intracellular signal transduction pathways that regulate cell-extracellular matrix interactions. Purpose: In the current study, we aimed to evaluate focal adhesion kinase (FAK) at both genetic and protein expression levels in head and neck squamous cell carcinomas (HNSCC) and to explore the prognostic significance of FAK. Experimental Design: A total of 211tissue specimens, including 147 primary tumors, 56 lymph node metastases, 3 benign hyperplasias, and 5 dysplasias, were analyzed using immunohistochemistry. The fak gene dosage was determined in 33 tumors. Correlations among DNA, protein, and clinicopathologic variables were analyzed. Results: FAK protein was overexpressed in HNSCCs compared with corresponding normal mucosa. High expression levels were found in 62% of the samples. Positive immunostaining was also detected in benign hyperplasias and preinvasive dysplastic lesions. All lymph node metastases examined showed FAK overexpression, with significant correlation with the expression in matched primary tumor. DNA copy number ratios for fak were higher in 39% of the tumors compared with normal mucosa. However, elevated FAK expression did not correlate with gains on DNA level, and not all cases with an amplification of the fak gene displayed protein overexpression. Similar data were obtained in five HNSCC-derived cell lines, in which FAK mRNA levels were precisely correlated with FAK protein levels. FAK protein overexpression in tumors correlated with nodal metastases. Conclusions: These findings suggest an involvement of FAK in the onset and progression of HNSCC and provide aninsight into a mechanism of FAK activation alternative to gene amplification.Head and neck squamous cell carcinoma (HNSCC) is one of the most common types of tumors worldwide. Despite recent advancements in diagnosis and treatment, the overall survival has undergone little improvement over the past few decades (1, 2). The major cause of the lethal progression of this type of cancer is the spreading of the malignant cells to regional lymph nodes, which represents a major prognostic indicator and serves as a guide for therapeutic strategies. Although many efforts have been devoted to better understand the molecular mechanisms involved in the progression of this type of cancer, accurate and reliable biomarkers that predict patients at highest risk for lymphatic metastases have yet to be defined.Loss of adhesion of the epithelial cells to the extracellular matrix is one of the fundamental pathways that promote tumor cell migration, invasion, and metastasis. A key factor involved in the control of cell-extracellular matrix interactions is the focal adhesion kinase (FAK), an intracellular tyrosine kinase protein that is localized to cellular focal contact sites (3). FAK is activated and tyrosine phosphorylated upon integrins clustering (4). Evidences also suggest that FAK is a key component of growth factor receptor signaling pathways, such as those activa...

Focal adhesion kinase (FAK) mediates tumor cell–intrinsic behaviors that promote tumor growth and metastasis. We previously showed that FAK also induces the expression of inflammatory genes that inhibit antitumor immunity in the microenvironment. Here, we identified a crucial, previously unknown role for the dual-function cytokine IL-33 in FAK-dependent immune evasion. In murine squamous cell carcinoma (SCC) cells, specifically nuclear FAK enhanced the expression of the genes encoding IL-33, the chemokine CCL5, and the soluble, secreted form of the IL-33 receptor sST2. The abundance of IL-33 and CCL5 was increased in FAK-positive SCC cells but not in normal keratinocytes. IL-33 associated with FAK in the nucleus, and the FAK–IL-33 complex interacted with a network of chromatin modifiers and transcriptional regulators, including TAF9, WDR82 and BRD4, which promote the activity of nuclear factor κB (NF-κB) and its induction of genes encoding chemokines, including CCL5. We did not detect secretion of IL-33 from FAK-positive SCC cells; thus, we propose that the increased production and secretion of sST2 likely sequesters IL-33 secreted by other cell types within the tumor environment, thus blocking its stimulatory effects on infiltrating host immune cells. Depleting FAK, IL-33, or sST2 from SCC cells before implantation induced tumor regression in syngeneic mice, except when CD8+ T cells were co-depleted. Our data provide mechanistic insight into how FAK controls the tumour immune environment, namely through a transcriptional regulatory network mediated by nuclear IL-33. Targeting this axis may boost antitumor immunity in patients.

The ability of tumor cells to invade and metastasize requires deregulation of interactions with adjacent cells and the extracellular matrix. A major challenge of cancer biology is to observe the dynamics of the proteins involved in this process in their functional and physiologic context. Here, for the first time, we have used photobleaching and photoactivation to compare the mobility of cell adhesion and plasma membrane probes in vitro and in tumors grown in mice (in vivo). We find differences between in vitro and in vivo recovery dynamics of two key molecules, the tumor suppressor E-cadherin and the membrane-targeting sequence of H-Ras. Our data show that E-cadherin dynamics are significantly faster in vivo compared with cultured cells, that the ratio of E-cadherin stabilized in cell-cell junctions is significantly higher in vivo, and that E-cadherin mobility correlates with cell migration. Moreover, quantitative imaging has allowed us to assess the effects of therapeutic intervention on E-cadherin dynamics using dasatinib, a clinically approved Src inhibitor, and show clear differences in the efficacy of drug treatment in vivo. Our results show for the first time the utility of photobleaching and photoactivation in the analysis of dynamic biomarkers in living animals. Furthermore, this work highlights critical differences in molecular dynamics in vitro and in vivo, which have important implications for the use of cultured disease models as surrogates for living tissue. [Cancer Res 2009;69(7):2714-9]

Focal adhesion kinase (FAK) is upregulated in several epithelial tumours and there has been considerable interest in developing small molecule kinase inhibitors of FAK. However, FAK also has important adaptor functions within the cell, integrating signals from both integrins and growth factors. To investigate the role of FAKs kinase domain, we generated fakdeficient squamous cell carcinoma (SCC) cell lines. Re-expression of a wild type or kinase dead FAK allowed us to delineate its kinase dependent functions. In addition, we used the novel FAK kinase inhibitor PF-562,271. The kinase activity of FAK was important for tumour cell migration and polarity but more striking was its requirement for the anchorage independent 3 dimensional (3D) proliferation of SCC cells and their growth as xenografts in mice. Inhibition of FAK activity and prevention of growth in 3D correlated with Src inhibition. We further identified a mechanism whereby FAK regulates proliferation in 3D via regulation of the kinase activity of Src. This was dependent on the kinase activity of FAK and its resulting phosphorylation on Y397 that provides a high affinity binding site for Src. These data support the further development of FAK kinase inhibitors as agents that have the potential to inhibit both tumour cell migration and proliferation.Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase found at focal adhesions, which are sites of integrin clustering at the cell-extracellular matrix interface, where it provides both signalling and scaffolding functions. It is involved in the dynamic regulation of these adhesion sites, a process that is critical for the control of cell migration. 1,2 FAK is also important for tumour cell invasion and metastasis, 3 where it is believed to integrate growth factor and integrin signals to promote both tumour cell migration and invasion. 2-4 FAK has also been linked to the protection of cells from suspension-induced apoptosis or anoikis 5-8 and introduction of inhibitory FAK constructs into tumour cells can lead to cell detachment and apoptosis. 9 FAK is therefore involved in a number of processes that can impact on the malignant phenotype, the importance of which is not fully understood. In support however, of a direct role for FAK in tumourigenesis we have shown, using targeted deletion of fak in mouse skin, the absolute requirement for FAK in malignant tumour formation. 10 More recently deletion of FAK has also been shown to be required for mammary tumour progression and the androgen-independent formation of neuroendocrine carcinoma in a prostate mouse model. [11][12][13][14][15] FAK is over-expressed in a number of human epithelial tumours [16][17][18] and FAK has therefore emerged as a potential target for cancer therapy 18-20 with a number of FAK kinase inhibitors being developed, one of which PF-562,271 is currently in clinical development. 21 There has been some debate surrounding the development of such agents as in addition to having kinase activity the adaptor function of FAK plays a key role in...