Breast Cancer Antiestrogen Resistance 3 (BCAR3) promotes tumor growth and progression in triple-negative breast cancer.

Triple-Negative Breast Cancers (TNBCs) constitute roughly 10-20% of breast cancers and are associated with poor clinical outcomes. Previous work from our laboratory and others has determined that the cytoplasmic adaptor protein Breast Cancer Antiestrogen Resistance 3 (BCAR3) is an important promoter of cell motility and invasion of breast cancer cells. In this study, we use both in vivo and in vitro approaches to extend our understanding of BCAR3 function in TNBC. We show that BCAR3 is upregulated in ductal carcinoma in situ (DCIS) and invasive carcinomas compared to normal mammary tissue, and that survival of TNBC patients whose tumors contained elevated BCAR3 mRNA is reduced relative to individuals whose tumors had less BCAR3 mRNA. Using mouse orthotopic tumor models, we further show that BCAR3 is required for efficient TNBC tumor growth. Analysis of publicly available RNA expression databases revealed that MET receptor signaling is strongly correlated with BCAR3 mRNA expression. A functional role for BCAR3-MET coupling is supported by data showing that both proteins participate in a single pathway to control proliferation and migration of TNBC cells. Interestingly, the mechanism through which this functional interaction operates appears to differ in different genetic backgrounds of TNBC, stemming in one case from potential differences in the strength of downstream signaling by the MET receptor and in another from BCAR3-dependent activation of an autocrine loop involving the production of HGF mRNA. Together, these data open the possibility for new approaches to personalized therapy for individuals with TNBCs.

Non-redundant functions of FAK and Pyk2 in intestinal epithelial repair.

Adhesion signaling between epithelial cells and the extracellular matrix plays a critical role in maintaining tissue homeostasis and the response to tissue damage. Focal adhesion kinase (FAK) and its close relative Pyk2 are non-receptor tyrosine kinases that mediate adhesion signaling to promote cell proliferation, motility and survival. FAK has also been shown to act as a mechanosensor by modulating cell proliferation in response to changes in tissue compliance. We previously showed that mice lacking FAK in the intestinal epithelium are phenotypically normal under homeostatic conditions but hypersensitive to experimental colitis induced by dextran sulfate sodium (DSS). Here we report that Pyk2-deficient mice are also phenotypically normal under homeostatic conditions and are similarly hypersensitive to DSS-induced colitis. These data indicate that normal intestinal development and homeostatic maintenance can occur in the presence of either FAK or Pyk2, but that both kinases are necessary for epithelial repair following injury. In contrast, mice lacking both FAK and Pyk2 develop spontaneous colitis with 100% penetrance by 4 weeks of age. Normal colonic phenotype and function are restored upon treatment of the double knockout mice with antibiotics, implicating commensal bacteria or bacterial products in the etiology of the spontaneous colitis exhibited by these mice.

Focal adhesion kinase (FAK) deficiency in mononuclear phagocytes alters murine breast tumor progression.

While it has long been recognized that mononuclear phagocytes play a significant role in determining breast tumor progression, the molecular factors that contribute to these events are not fully understood. In this report, we sought to determine whether focal adhesion kinase (FAK) expression in this cell population influences primary breast tumor initiation and growth. Using the MMTV-polyoma middle T (PyVmT) murine model of spontaneous breast cancer, we found that FAK expression in mononuclear phagocytes accelerates tumor initiation/progression during the early stages of PyVmT tumor growth but subsequently restricts tumor growth once the tumors have transitioned to malignancy. Mononuclear phagocytes accumulated at the site of developing tumors in a FAK-independent manner. However, once in the tumor, our data suggest that FAK expression is upregulated in the tumor-associated myeloid cells, and its activity in this population of cells may influence the immune landscape of the tumor by supporting the recruitment and/or survival of NK cells. Together, these data support a model in which FAK expression in the mononuclear phagocyte compartment positively regulates the early steps of tumor progression but subsequently functions to restrict tumor growth as the tumors transition to invasive carcinoma.

The nonreceptor protein tyrosine kinase Pyk2 promotes the turnover of monocytes at steady state.

Monocytes are short-lived myeloid cells that perform functions essential for tissue homeostasis and disease resolution. However, the cellular mechanisms controlling the maintenance and turnover of monocyte populations are largely undefined. Proline-rich tyrosine kinase 2 (Pyk2) is a nonreceptor tyrosine kinase that regulates numerous immune cell functions, but its role in monocytes is currently unknown. In this study, we sought to characterize the expression and function of Pyk2 in lineage-committed monocyte populations. Here, we report that Pyk2 protein expression is increased in the Ly6C- monocyte population. Using a Pyk2 knockout mouse model (Pyk2-/-), we show that Pyk2 regulates the relative proportion of monocyte subsets normally represented in the bone marrow (BM) at steady state. In support of this conclusion, a similar phenotype was observed in the peripheral blood and spleen. Data from reciprocal BM chimera experiments indicate that the alterations in monocyte populations exhibited by Pyk2-/- mice are due to factors intrinsic to the monocytes. Lineage-tracing of monocyte populations suggests that Pyk2 promotes apoptosis in BM monocytes, thereby acting as an important homeostatic regulator of turnover in these short-lived, innate immune cells.

Functional significance of mononuclear phagocyte populations generated through adult hematopoiesis.

Tissue homeostasis requires a complete repertoire of functional macrophages in peripheral tissues. Recent evidence indicates that many resident tissue macrophages are seeded during embryonic development and persist through adulthood as a consequence of localized proliferation. Mononuclear phagocytes are also produced during adult hematopoiesis; these cells are then recruited to sites throughout the body, where they function in tissue repair and remodeling, resolution of inflammation, maintenance of homeostasis, and disease progression. The focus of this review is on mononuclear phagocytes that comprise the nonresident monocyte/macrophage populations in the body. Key features of monocyte differentiation are presented, focusing primarily on the developmental hierarchy that is established through this process, the markers used to identify discrete cell populations, and novel, functional attributes of these cells. These features are then explored in the context of the tumor microenvironment, where mononuclear phagocytes exhibit extensive plasticity in phenotype and function.

Activation of focal adhesion kinase by Salmonella suppresses autophagy via an Akt/mTOR signaling pathway and promotes bacterial survival in macrophages.

Autophagy has emerged as an important antimicrobial host defense mechanism that not only orchestrates the systemic immune response, but also functions in a cell autonomous manner to directly eliminate invading pathogens. Pathogenic bacteria such as Salmonella have evolved adaptations to protect themselves from autophagic elimination. Here we show that signaling through the non-receptor tyrosine kinase focal adhesion kinase (FAK) is actively manipulated by the Salmonella SPI-2 system in macrophages to promote intracellular survival. In wild-type macrophages, FAK is recruited to the surface of the Salmonella-containing vacuole (SCV), leading to amplified signaling through the Akt-mTOR axis and inhibition of the autophagic response. In FAK-deficient macrophages, Akt/mTOR signaling is attenuated and autophagic capture of intracellular bacteria is enhanced, resulting in reduced bacterial survival. We further demonstrate that enhanced autophagy in FAK(-/-) macrophages requires the activity of Atg5 and ULK1 in a process that is distinct from LC3-assisted phagocytosis (LAP). In vivo, selective knockout of FAK in macrophages resulted in more rapid clearance of bacteria from tissues after oral infection with S. typhimurium. Clearance was correlated with reduced infiltration of inflammatory cell types into infected tissues and reduced tissue damage. Together, these data demonstrate that FAK is specifically targeted by S. typhimurium as a novel means of suppressing autophagy in macrophages, thereby enhancing their intracellular survival.

Expression of a phosphorylated substrate domain of p130Cas promotes PyMT-induced c-Src-dependent murine breast cancer progression.

Elevated expression of p130Cas (Crk-associated substrate)/BCAR1 (breast cancer antiestrogen resistance 1) in human breast tumors is a marker of poor prognosis and poor overall survival. p130Cas is a downstream target of the tyrosine kinase c-Src. Signaling mediated by p130Cas through its phosphorylated substrate domain (SD) and interaction with effector molecules directly promotes tumor progression. We previously developed a constitutively phosphorylated p130Cas SD molecule, Src*/SD (formerly referred to as Src*/CasSD), which acts as decoy molecule and attenuates the transformed phenotype in v-crk-transformed murine fibroblasts and human breast cancer cells. To test the function of this molecule in vivo, we established mouse mammary tumor virus (MMTV)-long terminal repeat-Src*/SD transgenic mice in which mammary gland development and tumor formation were analyzed. Transgenic expression of the Src*/SD molecule under the MMTV-long terminal repeat promoter did not interfere with normal mammary gland development or induce tumors in mice observed for up to 11 months. To evaluate the effects of the Src*/SD molecule on tumor development in vivo, we utilized the MMTV-polyoma middle T-antigen (PyMT) murine breast cancer model that depends on c-Src. PyMT mice crossed with Src*/SD mice displayed accelerated tumor formation. The earlier onset of tumors can be explained by the interaction of the Src* domain with PyMT and targeting the fused phosphorylated SD to the membrane. At membrane compartments, it might integrate membrane-associated active signaling complexes leading to increased proliferation measured by phospho-Histone H3 staining. Although these results were unexpected, they emphasize the importance of preventing the membrane association of Src*/SD when employed as decoy molecule.

Breast cancer antiestrogen resistance 3 (BCAR3) promotes cell motility by regulating actin cytoskeletal and adhesion remodeling in invasive breast cancer cells.

Metastatic breast cancer is incurable. In order to improve patient survival, it is critical to develop a better understanding of the molecular mechanisms that regulate metastasis and the underlying process of cell motility. Here, we focus on the role of the adaptor molecule Breast Cancer Antiestrogen Resistance 3 (BCAR3) in cellular processes that contribute to cell motility, including protrusion, adhesion remodeling, and contractility. Previous work from our group showed that elevated BCAR3 protein levels enhance cell migration, while depletion of BCAR3 reduces the migratory and invasive capacities of breast cancer cells. In the current study, we show that BCAR3 is necessary for membrane protrusiveness, Rac1 activity, and adhesion disassembly in invasive breast cancer cells. We further demonstrate that, in the absence of BCAR3, RhoA-dependent signaling pathways appear to predominate, as evidenced by an increase in RhoA activity, ROCK-mediated phosphorylation of myosin light chain II, and large ROCK/mDia1-dependent focal adhesions. Taken together, these data establish that BCAR3 functions as a positive regulator of cytoskeletal remodeling and adhesion turnover in invasive breast cancer cells through its ability to influence the balance between Rac1 and RhoA signaling. Considering that BCAR3 protein levels are elevated in advanced breast cancer cell lines and enhance breast cancer cell motility, we propose that BCAR3 functions in the transition to advanced disease by triggering intracellular signaling events that are essential to the metastatic process.

Cas and NEDD9 Contribute to Tumor Progression through Dynamic Regulation of the Cytoskeleton.

The Cas family proteins, p130(Cas) (Cas) and NEDD9, are adaptor molecules that regulate cytoskeletal dynamics to promote multiple cellular processes, including migration, invasion, proliferation, and survival. Because these functions are also critical for tumor initiation, growth, and metastasis, Cas and NEDD9 are well positioned to contribute to these oncogenic processes. Indeed, mouse models of cancer show that these proteins function during multiple stages of disease progression. Furthermore, in many human cancers, high expression of Cas and NEDD9 is associated with advanced stage disease and is predictive of poor outcome. This review explores the contribution of Cas and NEDD9 during cellular transformation and neoplastic growth, tumor progression, metastasis, and the development of therapeutic resistance. Given these roles, Cas and NEDD9 may prove to be viable candidates for use as biomarkers and therapeutic targets.

Regulation of osteoclast structure and function by FAK family kinases.

Osteoclasts are highly specialized cells that resorb bone and contribute to bone remodeling. Diseases such as osteoporosis and osteolytic bone metastasis occur when osteoclast-mediated bone resorption takes place in the absence of concurrent bone synthesis. Considerable effort has been placed on identifying molecules that regulate the bone resorption activity of osteoclasts. To this end, we investigated unique and overlapping functions of members of the FAK family (FAK and Pyk2) in osteoclast functions. With the use of a conditional knockout mouse model, in which FAK is selectively targeted for deletion in osteoclast precursors (FAK(Δmyeloid)), we found that loss of FAK resulted in reduced bone resorption by osteoclasts in vitro, coincident with impaired signaling through the CSF-1R. However, bone architecture appeared normal in FAK(Δmyeloid) mice, suggesting that Pyk2 might functionally compensate for reduced FAK levels in vivo. This was supported by data showing that podosome adhesion structures, which are essential for bone degradation, were significantly more impaired in osteoclasts when FAK and Pyk2 were reduced than when either molecule was depleted individually. We conclude that FAK contributes to cytokine signaling and bone resorption in osteoclasts and partially compensates for the absence of Pyk2 to maintain proper adhesion structures in these cells.

FAK regulates intestinal epithelial cell survival and proliferation during mucosal wound healing.

BACKGROUND: Following damage to the intestinal epithelium, restoration of epithelial barrier integrity is triggered by a robust proliferative response. In other tissues, focal adhesion kinase (FAK) regulates many of the cellular processes that are critical for epithelial homeostasis and restitution, including cell migration, proliferation and survival. However, few studies to date have determined how FAK contributes to mucosal wound healing in vivo. METHODOLOGY AND PRINCIPAL FINDINGS: To examine the role of FAK in intestinal epithelial homeostasis and during injury, we generated intestinal epithelium (IE)-specific conditional FAK knockout mice. Colitis was induced with dextran-sulfate-sodium (DSS) and intestinal tissues were analyzed by immunohistochemistry and immunoblotting. While intestinal development occurred normally in mice lacking FAK, FAK-deficient animals were profoundly susceptible to colitis. The loss of epithelial FAK resulted in elevated p53 expression and an increased sensitivity to apoptosis, coincident with a failure to upregulate epithelial cell proliferation. FAK has been reported to function as a mechanosensor, inducing cyclin D1 expression and promoting cell cycle progression under conditions in which tissue/matrix stiffness is increased. Collagen deposition, a hallmark of inflammatory injury resulting in increased tissue rigidity, was observed in control and FAK knockout mice during colitis. Despite this fibrotic response, the colonic epithelium in FAK-deficient mice exhibited significantly reduced cyclin D1 expression, suggesting that proliferation is uncoupled from fibrosis in the absence of FAK. In support of this hypothesis, proliferation of Caco-2 cells increased proportionally with matrix stiffness in vitro only under conditions of normal FAK expression; FAK depleted cells exhibited reduced proliferation concomitant with attenuated cyclin D1 expression. CONCLUSIONS: In the colon, FAK functions as a regulator of epithelial cell survival and proliferation under conditions of mucosal injury and a mechanosensor of tissue compliance, inducing repair-driven proliferation in the colonic epithelium through upregulation of cyclin D1.

Inhibition of focal adhesion kinase by PF-562,271 inhibits the growth and metastasis of pancreatic cancer concomitant with altering the tumor microenvironment.

Current therapies for pancreatic ductal adenocarcinoma (PDA) target individual tumor cells. Focal adhesion kinase (FAK) is activated in PDA, and levels are inversely associated with survival. We investigated the effects of PF-562,271 (a small-molecule inhibitor of FAK/PYK2) on (i) in vitro migration, invasion, and proliferation; (ii) tumor proliferation, invasion, and metastasis in a murine model; and (iii) stromal cell composition in the PDA microenvironment. Migration assays were conducted to assess tumor and stromal cell migration in response to cellular factors, collagen, and the effects of PF-562,271. An orthotopic murine model was used to assess the effects of PF-562,271 on tumor growth, invasion, and metastasis. Proliferation assays measured PF-562,271 effects on in vitro growth. Immunohistochemistry was used to examine the effects of FAK inhibition on the cellular composition of the tumor microenvironment. FAK and PYK2 were activated and expressed in patient-derived PDA tumors, stromal components, and human PDA cell lines. PF-562,271 blocked phosphorylation of FAK (phospho-FAK or Y397) in a dose-dependent manner. PF-562,271 inhibited migration of tumor cells, cancer-associated fibroblasts, and macrophages. Treatment of mice with PF-562,271 resulted in reduced tumor growth, invasion, and metastases. PF-562,271 had no effect on tumor necrosis, angiogenesis, or apoptosis, but it did decrease tumor cell proliferation and resulted in fewer tumor-associated macrophages and fibroblasts than control or gemcitabine. These data support a role for FAK in PDA and suggest that inhibitors of FAK may contribute to efficacious treatment of patients with PDA.

Macrophage motility requires distinct α5ß1/FAK and α4ß1/paxillin signaling events.

Macrophages function as key inflammatory mediators at sites of infection and tissue damage. Integrin and growth factor receptors facilitate recruitment of monocytes/macrophages to sites of inflammation in response to numerous extracellular stimuli. We have shown recently that FAK plays a role in regulating macrophage chemotaxis and invasion. As FAK is an established downstream mediator of integrin signaling, we sought to define the molecular circuitry involving FAK and the predominant ß1 integrin heterodimers expressed in these cells-α4ß1 and α5ß1. We show that α4ß1 and α5ß1 integrins are required for efficient haptotactic and chemotactic invasion and that stimulation of these integrin receptors leads to the adoption of distinct morphologies associated with motility. FAK is required downstream of α5ß1 for haptotaxis toward FN and chemotaxis toward M-CSF-1 and downstream of α4ß1 for the adoption of a polarized phenotype. The scaffolding molecule paxillin functions independently of FAK to promote chemotaxis downstream of α4ß1. These studies expand our understanding of ß1 integrin signaling networks that regulate motility and invasion in macrophages and thus, provide important new insights into mechanisms by which macrophages perform their diverse functions.

BCAR3 regulates Src/p130 Cas association, Src kinase activity, and breast cancer adhesion signaling.

The nonreceptor protein-tyrosine kinase c-Src is frequently overexpressed and/or activated in a variety of cancers, including those of the breast. Several heterologous binding partners of c-Src have been shown to regulate its catalytic activity by relieving intramolecular autoinhibitory interactions. One such protein, p130(Cas) (Cas), is expressed at high levels in both breast cancer cell lines and breast tumors, providing a potential mechanism for c-Src activation in breast cancers. The Cas-binding protein BCAR3 (breast cancer antiestrogen resistance-3) is expressed at high levels in invasive breast cancer cell lines, and this molecule has previously been shown to coordinate with Cas to increase c-Src activity in COS-1 cells. In this study, we show for the first time using gain- and loss-of-function approaches that BCAR3 regulates c-Src activity in the endogenous setting of breast cancer cells. We further show that BCAR3 regulates the interaction between Cas and c-Src, both qualitatively as well as quantitatively. Finally, we present evidence that the coordinated activity of these proteins contributes to breast cancer cell adhesion signaling and spreading. Based on these data, we propose that the c-Src/Cas/BCAR3 signaling axis is a prominent regulator of c-Src activity, which in turn controls cell behaviors that lead to aggressive and invasive breast tumor phenotypes.

Alpha5beta1-integrin controls ebolavirus entry by regulating endosomal cathepsins.

Integrins are involved in the binding and internalization of both enveloped and nonenveloped viruses. By using 3 distinct cell systems-CHO cells lacking expression of alpha(5)beta(1)-integrin, HeLa cells treated with siRNA to alpha(5)-integrin, and mouse beta(1)-integrin knockout fibroblasts, we show that alpha(5)beta(1)-integrin is required for efficient infection by pseudovirions bearing the ebolavirus glycoprotein (GP). These integrins are necessary for viral entry but not for binding or internalization. Given the need for endosomal cathepsins B and L (CatB and CatL) to prime GPs for fusion, we investigated the status of CatB and CatL in integrin-positive and integrin-negative cell lines. Alpha(5)beta(1)-Integrin-deficient cells lacked the double-chain (DC) forms of CatB and CatL, and this correlated with decreased CatL activity in integrin-negative CHO cells. These data indicate that alpha(5)beta(1)-integrin-negative cells may be refractory to infection by GP pseudovirions because they lack the necessary priming machinery (the double-chain forms of CatB and CatL). In support of this model, we show that GP pseudovirions that have been preprimed in vitro to generate the 19-kDa form of GP overcome the requirement for alpha(5)beta(1)-integrin for infection. These results provide further support for the requirement for endosomal cathepsins for ebolavirus infection, identify the DC forms of these cathepsins as previously unrecognized factors that contribute to cell tropism of this virus, and reveal a previously undescribed role for integrins during viral entry as regulators of endosomal cathepsins, which are required to prime the entry proteins of ebolavirus and other pathogenic viruses.

A novel association between p130Cas and resistance to the chemotherapeutic drug adriamycin in human breast cancer cells.

Resistance to chemotherapy remains a major obstacle for the treatment of breast cancer. Understanding the molecular mechanism(s) of resistance is crucial for the development of new effective therapies to treat this disease. This study examines the putative role of p130(Cas) (Cas) in resistance to the cytotoxic agent Adriamycin. High expression of Cas in primary breast tumors is associated with the failure to respond to the antiestrogen tamoxifen and poor prognosis, highlighting the potential clinical importance of this molecule. Here, we show a novel association between Cas and resistance to Adriamycin. We show that Cas overexpression renders MCF-7 breast cancer cells less sensitive to the growth inhibitory and proapoptotic effects of Adriamycin. The catalytic activity of the nonreceptor tyrosine kinase c-Src, but not the epidermal growth factor receptor, is critical for Cas-mediated protection from Adriamycin-induced death. The phosphorylation of Akt and extracellular signal-regulated kinase 1/2 (ERK1/2) is elevated in Cas-overexpressing cells treated with Adriamycin, whereas expression of the proapoptotic protein Bak is decreased. Conversely, Cas depletion in the more resistant T47D and MDA-MB-231 cell lines increases sensitivity to Adriamycin. Based on these data, we propose that Cas activates growth and survival pathways regulated by c-Src, Akt, and ERK1/2 that lead to the inhibition of mitochondrial-mediated apoptosis in the presence of Adriamycin. Because Cas is frequently expressed at high levels in breast cancers, these findings raise the possibility of resensitizing Cas-overexpressing tumors to chemotherapy through perturbation of Cas signaling pathways.

Cell adhesion promotes Ebola virus envelope glycoprotein-mediated binding and infection.

Ebola virus infects a wide variety of adherent cell types, while nonadherent cells are found to be refractory. To explore this correlation, we compared the ability of pairs of related adherent and nonadherent cells to bind a recombinant Ebola virus receptor binding domain (EboV RBD) and to be infected with Ebola virus glycoprotein (GP)-pseudotyped particles. Both human 293F and THP-1 cells can be propagated as adherent or nonadherent cultures, and in both cases adherent cells were found to be significantly more susceptible to both EboV RBD binding and GP-pseudotyped virus infection than their nonadherent counterparts. Furthermore, with 293F cells the acquisition of EboV RBD binding paralleled cell spreading and did not require new mRNA or protein synthesis.

Regulation of lamellipodial persistence, adhesion turnover, and motility in macrophages by focal adhesion kinase.

Macrophages are a key component of the innate immune system. In this study, we investigate how focal adhesion kinase (FAK) and the related kinase Pyk2 integrate adhesion signaling and growth factor receptor signaling to regulate diverse macrophage functions. Primary bone marrow macrophages isolated from mice in which FAK is conditionally deleted from cells of the myeloid lineage exhibited elevated protrusive activity, altered adhesion dynamics, impaired chemotaxis, elevated basal Rac1 activity, and a marked inability to form stable lamellipodia necessary for directional locomotion. The contribution of FAK to macrophage function in vitro was substantiated in vivo by the finding that recruitment of monocytes to sites of inflammation was impaired in the absence of FAK. Decreased Pyk2 expression in primary macrophages also resulted in a diminution of invasive capacity. However, the combined loss of FAK and Pyk2 had no greater effect than the loss of either molecule alone, indicating that both kinases function within the same pathway to promote invasion.

Breast cancer antiestrogen resistance-3 expression regulates breast cancer cell migration through promotion of p130Cas membrane localization and membrane ruffling.

Antiestrogens such as tamoxifen are widely used in the clinic to treat estrogen receptor-positive breast tumors. Resistance to tamoxifen can occur either de novo or develop over time in a large proportion of these tumors. Additionally, resistance is associated with enhanced motility and invasiveness in vitro. One molecule that has been implicated in tamoxifen resistance, breast cancer antiestrogen resistance-3 (BCAR3), has also been shown to regulate migration of fibroblasts. In this study, we investigated the role of BCAR3 in breast cancer cell migration and invasion. We found that BCAR3 was highly expressed in multiple breast cancer cell lines, where it associated with another protein, p130(Cas) (also known as breast cancer antiestrogen resistance-1; BCAR1), that plays a role in both tamoxifen resistance and cell motility. In cells with relatively low migratory potential, BCAR3 overexpression resulted in enhanced migration and colocalization with p130(Cas) at the cell membrane. Conversely, BCAR3 depletion from more aggressive breast cancer cell lines inhibited migration and invasion. This coincided with a relocalization of p130(Cas) away from the cell membrane and an attenuated response to epidermal growth factor stimulation that was characterized by a loss of membrane ruffles, decreased migration toward EGF, and disruption of p130(Cas)/Crk complexes. Based on these data, we propose that the spatial and temporal regulation of BCAR3/p130(Cas) interactions within the cell is important for controlling breast cancer cell motility.

Pathways to tamoxifen resistance.

Therapies that target the synthesis of estrogen or the function of estrogen receptor(s) have been developed to treat breast cancer. While these approaches have proven to be beneficial to a large number of patients, both de novo and acquired resistance to these drugs is a significant problem. Recent advances in our understanding of the molecular mechanisms that contribute to resistance have provided a means to begin to predict patient responses to these drugs and develop rational approaches for combining therapeutic agents to circumvent or desensitize the resistant phenotype. Here, we review common mechanisms of antiestrogen resistance and discuss the implications for prediction of response and design of effective combinatorial treatments.