P-cadherin signals through the laminin receptor α6β4 integrin to induce stem cell and invasive properties in basal-like breast cancer cells

Impact of brain organoid-derived sEVs on metastatic adaptation and invasion of breast carcinoma cells through a microphysiological system

Brain metastases are common in triple-negative breast cancer (TNBC), suggesting a complex process of cancer spread. The mechanisms enabling TNBC cell adaptation and proliferation in the brain remain unclear. Small extracellular vesicles (sEVs) play a crucial role in communication between breast carcinoma cells and the brain. However, the lack of relevant models hinders understanding of sEV-mediated communication. The present study assesses the impact of brain organoid-derived sEVs (BO-sEVs) on various behaviours of the MDA-MB-231 cell line, chosen as a representative of TNBC in a 3D microfluidic model. Our results demonstrate that 150-200 nm sEVs expressing CD63, CD9, and CD81 from brain organoid media decrease MDA-MB-231 cell proliferation, enhance their wound-healing capacity, alter their morphology into more mesenchymal mode, and increase their stemness. BO-sEVs led to heightened PD-L1, CD49f, and vimentin levels of expression in MDA-MB-231 cells, suggesting an amplified immunosuppressive, stem-like, and mesenchymal phenotype. Furthermore, these sEVs also induced the expression of neural markers such as GFAP in carcinoma cells. The cytokine antibody profiling array also showed that BO-sEVs enhanced the secretion of MCP-1, IL-6, and IL-8 by MDA-MB-231 cells. Moreover, sEVs significantly enhance the migration and invasion of carcinoma cells toward brain organoids in a 3D organoid-on-a-chip system. Our findings emphasize the potential significance of metastatic site-derived sEVs as pivotal mediators in carcinoma progression and adaptation to the brain microenvironment, thereby unveiling novel therapeutic avenues.

A crucial stem cell plasticity regulation pathway: identification of key elements using the NCCIT human embryonic carcinoma cell line

Upon removal of stemness factors, a small subpopulation of embryonic stem cells (ESCs) spontaneously extrudes the t-SNARE protein syntaxin-4, which upregulates the cell adhesion molecule P-cadherin and induces the onset of epithelial-mesenchymal transition (EMT)-like behaviors with loss of stemness in each cell. In this study, we identified a series of molecular elements responsible for this phenomenon using several small-molecule inhibitors and the human embryonic carcinoma cell line, NCCIT. We found that the syntaxin-4-triggered morphological changes and a decrease in stemness signatures were independently induced by the activation of Rho-associated kinase (ROCK) and the abrogation of PI3K/Akt signaling. We also found that the extracellular expression of syntaxin-4 inactivated focal adhesion kinase (FAK) in association with the augmented expression of P-cadherin, and comparable controls of either of these downstream elements of syntaxin-4 accelerated both ROCK-induced F-actin stress fiber formation and P13K/Akt-suppressed loss of stemness signatures. Cells expressing P-cadherin inactivated FAK but FAK inhibition did not affect P-cadherin expression, demonstrating a causal relationship between P-cadherin and FAK in the event of syntaxin-4 induction. These results reveal a novel signaling axis in stem cells and shed new light on the crucial elements for stem cell plasticity and the maintenance of stemness.

Anoikis resistance--protagonists of breast cancer cells survive and metastasize after ECM detachment

Breast cancer exhibits the highest global incidence among all tumor types. Regardless of the type of breast cancer, metastasis is a crucial cause of poor prognosis. Anoikis, a form of apoptosis initiated by cell detachment from the native environment, is an outside-in process commencing with the disruption of cytosolic connectors such as integrin-ECM and cadherin-cell. This disruption subsequently leads to intracellular cytoskeletal and signaling pathway alterations, ultimately activating caspases and initiating programmed cell death. Development of an anoikis-resistant phenotype is a critical initial step in tumor metastasis. Breast cancer employs a series of stromal alterations to suppress anoikis in cancer cells. Comprehensive investigation of anoikis resistance mechanisms can inform strategies for preventing and regressing metastatic breast cancer. The present review first outlines the physiological mechanisms of anoikis, elucidating the alterations in signaling pathways, cytoskeleton, and protein targets that transpire from the outside in upon adhesion loss in normal breast cells. The specific anoikis resistance mechanisms induced by pathological changes in various spatial structures during breast cancer development are also discussed. Additionally, the genetic loci of targets altered in the development of anoikis resistance in breast cancer, are summarized. Finally, the micro-RNAs and targeted drugs reported in the literature concerning anoikis are compiled, with keratocin being the most functionally comprehensive. Video Abstract.

Polo-like kinase 4 (Plk4) potentiates anoikis-resistance of p53KO mammary epithelial cells by inducing a hybrid EMT phenotype

Polo-like kinase 4 (Plk4), the major regulator of centriole biogenesis, has emerged as a putative therapeutic target in cancer due to its abnormal expression in human carcinomas, leading to centrosome number deregulation, mitotic defects and chromosomal instability. Moreover, Plk4 deregulation promotes tumor growth and metastasis in mouse models and is significantly associated with poor patient prognosis. Here, we further investigate the role of Plk4 in carcinogenesis and show that its overexpression significantly potentiates resistance to cell death by anoikis of nontumorigenic p53 knock-out (p53KO) mammary epithelial cells. Importantly, this effect is independent of Plk4's role in centrosome biogenesis, suggesting that this kinase has additional cellular functions. Interestingly, the Plk4-induced anoikis resistance is associated with the induction of a stable hybrid epithelial-mesenchymal phenotype and is partially dependent on P-cadherin upregulation. Furthermore, we found that the conditioned media of Plk4-induced p53KO mammary epithelial cells also induces anoikis resistance of breast cancer cells in a paracrine way, being also partially dependent on soluble P-cadherin secretion. Our work shows, for the first time, that high expression levels of Plk4 induce anoikis resistance of both mammary epithelial cells with p53KO background, as well as of breast cancer cells exposed to their secretome, which is partially mediated through P-cadherin upregulation. These results reinforce the idea that Plk4, independently of its role in centrosome biogenesis, functions as an oncogene, by impacting the tumor microenvironment to promote malignancy.

Activation of an actin signaling pathway in pre-malignant mammary epithelial cells by P-cadherin is essential for transformation

Alterations in the expression or function of cell adhesion molecules have been implicated in all steps of tumor progression. Among those, P-cadherin is highly enriched in basal-like breast carcinomas, playing a central role in cancer cell self-renewal, collective cell migration and invasion. To establish a clinically relevant platform for functional exploration of P-cadherin effectors in vivo, we generated a humanized P-cadherin Drosophila model. We report that actin nucleators, Mrtf and Srf, are main P-cadherin effectors in fly. We validated these findings in a human mammary epithelial cell line with conditional activation of the SRC oncogene. We show that, prior to promoting malignant phenotypes, SRC induces a transient increase in P-cadherin expression, which correlates with MRTF-A accumulation, its nuclear translocation and the upregulation of SRF target genes. Moreover, knocking down P-cadherin, or preventing F-actin polymerization, impairs SRF transcriptional activity. Furthermore, blocking MRTF-A nuclear translocation hampers proliferation, self-renewal and invasion. Thus, in addition to sustaining malignant phenotypes, P-cadherin can also play a major role in the early stages of breast carcinogenesis by promoting a transient boost of MRTF-A-SRF signaling through actin regulation.

A Cdh3-β-catenin-laminin signaling axis in a subset of breast tumor leader cells control leader cell polarization and directional collective migration

Carcinoma dissemination can occur when heterogeneous tumor and tumor-stromal cell clusters migrate together via collective migration. Cells at the front lead and direct collective migration, yet how these leader cells form and direct migration are not fully appreciated. From live videos of primary mouse and human breast tumor organoids in a 3D microfluidic system mimicking native breast tumor microenvironment, we developed 3D computational models, which hypothesize that leader cells need to generate high protrusive forces and overcome extracellular matrix (ECM) resistance at the leading edge. From single-cell sequencing analyses, we find that leader cells are heterogeneous and identify and isolate a keratin 14- and cadherin-3-positive subpopulation sufficient to lead collective migration. Cdh3 controls leader cell protrusion dynamics through local production of laminin, which is required for integrin/focal adhesion function. Our findings highlight how a subset of leader cells interact with the microenvironment to direct collective migration.

P-Cadherin Regulates Intestinal Epithelial Cell Migration and Mucosal Repair, but Is Dispensable for Colitis Associated Colon Cancer

Recurrent chronic mucosal inflammation, a characteristic of inflammatory bowel diseases (IBD), perturbs the intestinal epithelial homeostasis resulting in formation of mucosal wounds and, in most severe cases, leads to colitis-associated colon cancer (CAC). The altered structure of epithelial cell-cell adhesions is a hallmark of intestinal inflammation contributing to epithelial injury, repair, and tumorigenesis. P-cadherin is an important adhesion protein, poorly expressed in normal intestinal epithelial cells (IEC) but upregulated in inflamed and injured mucosa. The goal of this study was to investigate the roles of P-cadherin in regulating intestinal inflammation and CAC. P-cadherin expression was markedly induced in the colonic epithelium of human IBD patients and CAC tissues. The roles of P-cadherin were investigated in P-cadherin null mice using dextran sulfate sodium (DSS)-induced colitis and an azoxymethane (AOM)/DSS induced CAC. Although P-cadherin knockout did not affect the severity of acute DSS colitis, P-cadherin null mice exhibited faster recovery after colitis. No significant differences in the number of colonic tumors were observed in P-cadherin null and control mice. Consistently, the CRISPR/Cas9-mediated knockout of P-cadherin in human IEC accelerated epithelial wound healing without affecting cell proliferation. The accelerated migration of P-cadherin depleted IEC was driven by activation of Src kinases, Rac1 GTPase and myosin II motors and was accompanied by transcriptional reprogramming of the cells. Our findings highlight P-cadherin as a negative regulator of IEC motility in vitro and mucosal repair in vivo. In contrast, this protein is dispensable for IEC proliferation and CAC development.

Breast Cancer Stem Cell Membrane Biomarkers: Therapy Targeting and Clinical Implications

Breast cancer is the most common malignancy affecting women worldwide. Importantly, there have been significant improvements in prevention, early diagnosis, and treatment options, which resulted in a significant decrease in breast cancer mortality rates. Nevertheless, the high rates of incidence combined with therapy resistance result in cancer relapse and metastasis, which still contributes to unacceptably high mortality of breast cancer patients. In this context, a small subpopulation of highly tumourigenic cancer cells within the tumour bulk, commonly designated as breast cancer stem cells (BCSCs), have been suggested as key elements in therapy resistance, which are responsible for breast cancer relapses and distant metastasis. Thus, improvements in BCSC-targeting therapies are crucial to tackling the metastatic progression and might allow therapy resistance to be overcome. However, the design of effective and specific BCSC-targeting therapies has been challenging since there is a lack of specific biomarkers for BCSCs, and the most common clinical approaches are designed for commonly altered BCSCs signalling pathways. Therefore, the search for a new class of BCSC biomarkers, such as the expression of membrane proteins with cancer stem cell potential, is an area of clinical relevance, once membrane proteins are accessible on the cell surface and easily recognized by specific antibodies. Here, we discuss the significance of BCSC membrane biomarkers as potential prognostic and therapeutic targets, reviewing the CSC-targeting therapies under clinical trials for breast cancer.

The Anti-Endometriotic Effect of Cyperi Rhizoma Extract, Inhibiting Cell Adhesion and the Expression of Pain-Related Factors through Akt and NF-kB Pathways

Rhizomes of Cyperus rotundus have been widely used as a traditional medicine in Asia for the treatment of gynecological diseases. However, there is no scientific evidence demonstrating the effect of C. rotundus rhizomes on endometriosis, which is characterized by the adhesion of endometrial tissues outside the uterus, resulting in chronic and severe pelvic pain. The aim of this study was to investigate the effects of Cyperi rhizoma extract (CRE) on cell adhesion and the expression of pain-related factors (neurotrophins) in endometriotic cells, and to elucidate the underlying molecular mechanisms. CRE inhibited the adhesion of human endometriotic 12Z cells to peritoneal mesothelial Met5A cells using by adhesion assays. The mRNA expression of adhesion molecules [P-cadherin and matrix metalloproteinase (MMP)-2] was downregulated by CRE treatment. In addition, CRE significantly inhibited the mRNA expression of neurotrophins (BDNF, NGF, NT-3 and NT-4/5) in 12Z cells. Moreover, Akt overexpression markedly neutralized the inhibition of cell adhesion by CRE and expression of neurotrophins in 12Z cells. Furthermore, it was found that CRE suppressed NF-kB activation through the Akt pathway. These data suggest that CRE exerts anti-endometriotic activities by the inhibition of cell adhesion and neurotrophin expression, through the negative regulation of the Akt and NF-kB pathways in endometriotic cells.

Cadherin‐3 is a novel oncogenic biomarker with prognostic value in glioblastoma

Glioblastoma (GBM) is the most common and malignant primary brain tumor in adults. The prognosis of patients is very poor, with a median overall survival of ~ 15 months after diagnosis. Cadherin‐3 (also known as P‐cadherin), a cell–cell adhesion molecule encoded by the CDH3 gene, is deregulated in several cancer types, but its relevance in GBM is unknown. In this study, we investigated the functional roles, the associated molecular signatures, and the prognostic value of CDH3/P‐cadherin in this highly malignant brain tumor. CDH3/P‐cadherin mRNA and protein levels were evaluated in human glioma samples. Knockdown and overexpression models of P‐cadherin in GBM were used to evaluate its functional role in vitro and in vivo. CDH3‐associated gene signatures were identified by enrichment analyses and correlations. The impact of CDH3 in the survival of GBM patients was assessed in independent cohorts using both univariable and multivariable models. We found that P‐cadherin protein is expressed in a subset of gliomas, with an increased percentage of positive samples in grade IV tumors. Concordantly, CDH3 mRNA levels in glioma samples from The Cancer Genome Atlas (TCGA) database are increased in high‐grade gliomas. P‐cadherin displays oncogenic functions in multiple knockdown and overexpression GBM cell models by affecting cell viability, cell cycle, cell invasion, migration, and neurosphere formation capacity. Genes that were positively correlated with CDH3 are enriched for oncogenic pathways commonly activated in GBM. In vivo, GBM cells expressing high levels of P‐cadherin generate larger subcutaneous tumors and cause shorter survival of mice in an orthotopic intracranial model. Concomitantly, high CDH3 expression is predictive of shorter overall survival of GBM patients in independent cohorts. Together, our results show that CDH3/P‐cadherin expression is associated with aggressiveness features of GBM and poor patient prognosis, suggesting that it may be a novel therapeutic target for this deadly brain tumor.

Cancer-Cell-Derived IgG and Its Potential Role in Tumor Development

Human immunoglobulin G (IgG) is the primary component of the human serum antibody fraction, representing about 75% of the immunoglobulins and 10-20% of the total circulating plasma proteins. Generally, IgG sequences are highly conserved, yet the four subclasses, IgG1, IgG2, IgG3, and IgG4, differ in their physiological effector functions by binding to different IgG-Fc receptors (FcγR). Thus, despite a similarity of about 90% on the amino acid level, each subclass possesses a unique manner of antigen binding and immune complex formation. Triggering FcγR-expressing cells results in a wide range of responses, including phagocytosis, antibody-dependent cell-mediated cytotoxicity, and complement activation. Textbook knowledge implies that only B lymphocytes are capable of producing antibodies, which recognize specific antigenic structures derived from pathogens and infected endogenous or tumorigenic cells. Here, we review recent discoveries, including our own observations, about misplaced IgG expression in tumor cells. Various studies described the presence of IgG in tumor cells using immunohistology and established correlations between high antibody levels and promotion of cancer cell proliferation, invasion, and poor clinical prognosis for the respective tumor patients. Furthermore, blocking tumor-cell-derived IgG inhibited tumor cells. Tumor-cell-derived IgG might impede antigen-dependent cellular cytotoxicity by binding antigens while, at the same time, lacking the capacity for complement activation. These findings recommend tumor-cell-derived IgG as a potential therapeutic target. The observed uniqueness of Ig heavy chains expressed by tumor cells, using PCR with V(D)J rearrangement specific primers, suggests that this specific part of IgG may additionally play a role as a potential tumor marker and, thus, also qualify for the neoantigen category.

Cadherin Expression and EMT: A Focus on Gliomas

Cadherins are calcium-binding proteins with a pivotal role in cell adhesion and tissue homeostasis. The cadherin-dependent mechanisms of cell adhesion and migration are exploited by cancer cells, contributing to tumor invasiveness and dissemination. In particular, cadherin switch is a hallmark of epithelial to mesenchymal transition, a complex development process vastly described in the progression of most epithelial cancers. This is characterized by drastic changes in cell polarity, adhesion, and motility, which lead from an E-cadherin positive differentiated epithelial state into a dedifferentiated mesenchymal-like state, prone to metastization and defined by N-cadherin expression. Although vastly explored in epithelial cancers, how these mechanisms contribute to the pathogenesis of other non-epithelial tumor types is poorly understood. Herein, the current knowledge on cadherin expression in normal development in parallel to tumor pathogenesis is reviewed, focusing on epithelial to mesenchymal transition. Emphasis is taken in the unascertained cadherin expression in CNS tumors, particularly in gliomas, where the potential contribution of an epithelial-to-mesenchymal-like process to glioma genesis and how this may be associated with changes in cadherin expression is discussed.

Niche Laminin and IGF-1 Additively Coordinate the Maintenance of Oct-4 Through CD49f/IGF-1R-Hif-2α Feedforward Loop in Mouse Germline Stem Cells

The mechanism on how extracellular matrix (ECM) cooperates with niche growth factors and oxygen tension to regulate the self-renewal of embryonic germline stem cells (GSCs) still remains unclear. Lacking of an appropriate in vitro cell model dramatically hinders the progress. Herein, using a serum-free culture system, we demonstrated that ECM laminin cooperated with hypoxia and insulin-like growth factor 1 receptor (IGF-1R) to additively maintain AP activity and Oct-4 expression of AP⁺GSCs. We found the laminin receptor CD49f expression in d2 testicular GSCs that were surrounded by laminin. Laminin and hypoxia significantly increased the GSC stemness-related genes, including Hif-2α, Oct-4, IGF-1R, and CD49f. Cotreatment of IGF-1 and laminin additively increased the expression of IGF-IR, CD49f, Hif-2α, and Oct-4. Conversely, silencing IGF-1R and/or CD49f decreased the expression of Hif-2α and Oct-4. The underlying mechanism involved CD49f/IGF1R-(PI3K/AKT)-Hif-2α signaling loop, which in turn maintains Oct-4 expression, symmetric self-renewal, and cell migration. These findings reveal the additive niche laminin/IGF-IR network during early GSC development.

Behind Brain Metastases Formation: Cellular and Molecular Alterations and Blood-Brain Barrier Disruption

Breast cancer (BC) brain metastases is a life-threatening condition to which accounts the poor understanding of BC cells' (BCCs) extravasation into the brain, precluding the development of preventive strategies. Thus, we aimed to unravel the players involved in the interaction between BCCs and blood-brain barrier (BBB) endothelial cells underlying BBB alterations and the transendothelial migration of malignant cells. We used brain microvascular endothelial cells (BMECs) as a BBB in vitro model, under conditions mimicking shear stress to improve in vivo-like BBB features. Mixed cultures were performed by the addition of fluorescently labelled BCCs to distinguish individual cell populations. BCC-BMEC interaction compromised BBB integrity, as revealed by junctional proteins (β-catenin and zonula occludens-1) disruption and caveolae (caveolin-1) increase, reflecting paracellular and transcellular hyperpermeability, respectively. Both BMECs and BCCs presented alterations in the expression pattern of connexin 43, suggesting the involvement of the gap junction protein. Myosin light chain kinase and phosphorylated myosin light chain were upregulated, revealing the involvement of the endothelial cytoskeleton in the extravasation process. β4-Integrin and focal adhesion kinase were colocalised in malignant cells, reflecting molecular interaction. Moreover, BCCs exhibited invadopodia, attesting migratory properties. Collectively, hub players involved in BC brain metastases formation were unveiled, disclosing possible therapeutic targets for metastases prevention.

PCA062, a P-cadherin Targeting Antibody-Drug Conjugate, Displays Potent Antitumor Activity Against P-cadherin-expressing Malignancies

The cell surface glycoprotein P-cadherin is highly expressed in a number of malignancies, including those arising in the epithelium of the bladder, breast, esophagus, lung, and upper aerodigestive system. PCA062 is a P-cadherin specific antibody-drug conjugate that utilizes the clinically validated SMCC-DM1 linker payload to mediate potent cytotoxicity in cell lines expressing high levels of P-cadherin in vitro, while displaying no specific activity in P-cadherin-negative cell lines. High cell surface P-cadherin is necessary, but not sufficient, to mediate PCA062 cytotoxicity. In vivo, PCA062 demonstrated high serum stability and a potent ability to induce mitotic arrest. In addition, PCA062 was efficacious in clinically relevant models of P-cadherin-expressing cancers, including breast, esophageal, and head and neck. Preclinical non-human primate toxicology studies demonstrated a favorable safety profile that supports clinical development. Genome-wide CRISPR screens reveal that expression of the multidrug-resistant gene ABCC1 and the lysosomal transporter SLC46A3 differentially impact tumor cell sensitivity to PCA062. The preclinical data presented here suggest that PCA062 may have clinical value for treating patients with multiple cancer types including basal-like breast cancer.

Cytokeratin 5 determines maturation of the mammary myoepithelium

At invasion, transformed mammary epithelial cells expand into the stroma through a disrupted myoepithelial (ME) cell layer and basement membrane (BM). The intact ME cell layer has thus been suggested to act as a barrier against invasion. Here, we investigate the mechanisms behind the disruption of ME cell layer. We show that the expression of basal/ME proteins CK5, CK14, and α-SMA altered along increasing grade of malignancy, and their loss affected the maintenance of organotypic 3D mammary architecture. Furthermore, our data suggests that loss of CK5 prior to invasive stage causes decreased levels of Zinc finger protein SNAI2 (SLUG), a key regulator of the mammary epithelial cell lineage determination. Consequently, a differentiation bias toward luminal epithelial cell type was detected with loss of mature, α-SMA-expressing ME cells and reduced deposition of basement membrane protein laminin-5. Therefore, our data discloses the central role of CK5 in mammary epithelial differentiation and maintenance of normal ME layer.

The Unique Biology behind the Early Onset of Breast Cancer

Breast cancer commonly affects women of older age; however, in developing countries, up to 20% of breast cancer cases present in young women (younger than 40 years as defined by oncology literature). Breast cancer in young women is often defined to be aggressive in nature, usually of high histological grade at the time of diagnosis and negative for endocrine receptors with poor overall survival rate. Several researchers have attributed this aggressive nature to a hidden unique biology. However, findings in this aspect remain controversial. Thus, in this article, we aimed to review published work addressing somatic mutations, chromosome copy number variants, single nucleotide polymorphisms, differential gene expression, microRNAs and gene methylation profile of early-onset breast cancer, as well as its altered pathways resulting from those aberrations. Distinct biology behind early-onset of breast cancer was clear among estrogen receptor-positive and sporadic cases. However, further research is needed to determine and validate specific novel markers, which may help in customizing therapy for this group of patients.

The Chick Chorioallantoic Membrane Model: A New In Vivo Tool to Evaluate Breast Cancer Stem Cell Activity

The high plasticity of cancer stem-like cells (CSCs) allows them to differentiate and proliferate, specifically when xenotransplanted subcutaneously into immunocompromised mice. CSCs are highly tumorigenic, even when inoculated in small numbers. Thus, in vivo limiting dilution assays (LDA) in mice are the current gold standard method to evaluate CSC enrichment and activity. The chick embryo chorioallantoic membrane (CAM) is a low cost, naturally immune-incompetent and reproducible model widely used to evaluate the spontaneous growth of human tumor cells. Here, we established a CAM-LDA assay able to rapidly reproduce tumor specificities—in particular, the ability of the small population of CSCs to form tumors. We used a panel of organotropic metastatic breast cancer cells, which show an enrichment in a stem cell gene signature, enhanced CD44⁺/CD24^−/low cell surface expression and increased mammosphere-forming efficiency (MFE). The size of CAM-xenografted tumors correlate with the number of inoculated cancer cells, following mice xenograft growth pattern. CAM and mice tumors are histologically comparable, displaying both breast CSC markers CD44 and CD49f. Therefore, we propose a new tool for studying CSC prevalence and function—the chick CAM-LDA—a model with easy handling, accessibility, rapid growth and the absence of ethical and regulatory constraints.

BR-BCSC Signature: The Cancer Stem Cell Profile Enriched in Brain Metastases that Predicts a Worse Prognosis in Lymph Node-Positive Breast Cancer

Brain metastases remain an unmet clinical need in breast oncology, being frequently found in HER2-overexpressing and triple-negative carcinomas. These tumors were reported to be highly cancer stem-like cell-enriched, suggesting that brain metastases probably arise by the seeding of cancer cells with stem features. Accordingly, we found that brain-tropic breast cancer cells show increased stem cell activity and tumorigenic capacity in the chick embryo choriallantoic membrane when compared to the parental cell line. These observations were supported by a significant increase in their stem cell frequency and by the enrichment for the breast cancer stem cell (BCSC) phenotype CD44⁺CD24^−/low. Based on this data, the expression of BCSC markers (CD44, CD49f, P-cadherin, EpCAM, and ALDH1) was determined and found to be significantly enriched in breast cancer brain metastases when compared to primary tumors. Therefore, a brain (BR)-BCSC signature was defined (3–5 BCSC markers), which showed to be associated with decreased brain metastases-free and overall survival. Interestingly, this signature significantly predicted a worse prognosis in lymph node-positive patients, acting as an independent prognostic factor. Thus, an enrichment of a BCSC signature was found in brain metastases, which can be used as a new prognostic factor in clinically challenging breast cancer patients.

P-cadherin induces anoikis-resistance of matrix-detached breast cancer cells by promoting pentose phosphate pathway and decreasing oxidative stress

Successful metastatic spreading relies on cancer cells with stem-like properties, glycolytic metabolism and increased antioxidant protection, allowing them to escape anoikis and to survive in circulation. The expression of P-cadherin, a poor prognostic factor in breast cancer, is associated with hypoxic, glycolytic and acidosis biomarkers. In agreement, P-cadherin-enriched breast cancer cell populations presents a glycolytic and an acid-resistance phenotype. Our aim was to evaluate whether P-cadherin expression controls the glycolytic and oxidative phosphorylation fluxes of matrix-detached breast cancer cells, acting as an antioxidant and enhancing their survival in anchorage-independent conditions. By using matrix-detached breast cancer cells, we concluded that P-cadherin increases glucose-6-phosphate dehydrogenase expression, up-regulating the carbon flux through the pentose phosphate pathway, while inhibiting pyruvate oxidation to acetyl-coA via pyruvate dehydrogenase kinase-4 (PDK-4) activation. Accordingly, P-cadherin expression conferred increased sensitivity to dichloroacetate (DCA), a PDK inhibitor. P-cadherin expression also regulates oxidative stress in matrix-detached breast cancer cells, through the control of antioxidant systems, such as catalase and superoxide dismutases (SOD)1 and 2, providing these cells with an increased resistance to doxorubicin-induced anoikis. Importantly, this association was validated in primary invasive breast carcinomas, where an enrichment of SOD2 was found in P-cadherin-overexpressing breast carcinomas. In conclusion, we propose that P-cadherin up-regulates carbon flux through the pentose phosphate pathway and decreases oxidative stress in matrix-detached breast cancer cells. These metabolic remodeling and antioxidant roles of P-cadherin can promote the survival of breast cancer cells in circulation and in metastatic sites, being a possible player in breast cancer therapeutic resistance to pro-oxidant-based interventions.

Whole transcriptome analysis of bovine mammary progenitor cells by P-Cadherin enrichment as a marker in the mammary cell hierarchy

Adult bovine mammary stem cells possess the ability to regenerate in vivo clonal outgrowths that mimic functional alveoli. Commonly available techniques that involve immunophenotype-based cell sorting yield cell fractions that are moderately enriched, far from being highly purified. Primary bovine mammary epithelial cells segregated in four different populations according to the expression of P-Cadherin and CD49f. Sorted cells from each fraction were tested for the presence of lineage-restricted progenitors and stem cells. Only cells from the CD49f^high/P-Cadherin^neg subpopulation were able to give rise to both luminal- and myoepithelial-restricted colonies in vitro and generate organized outgrowths in vivo, which are hallmarks of stem cell activity. After whole transcriptome analysis, we found gene clusters to be differentially enriched that relate to cell-to-cell communication, metabolic processes, proliferation, migration and morphogenesis. When we analyzed only the genes that were differentially expressed in the stem cell enriched fraction, clusters of downregulated genes were related to proliferation, while among the upregulated expression, cluster of genes related to cell adhesion, migration and cytoskeleton organization were observed. Our results show that P-Cadherin separates mammary subpopulations differentially in progenitor cells or mammary stem cells. Further we provide a comprehensive observation of the gene expression differences among these cell populations which reinforces the assumption that bovine mammary stem cells are typically quiescent.

BIK drives an aggressive breast cancer phenotype through sublethal apoptosis and predicts poor prognosis of ER-positive breast cancer

Apoptosis is fundamental to normal animal development and is the target for many anticancer therapies. Recent studies have explored the consequences of "failed apoptosis" where the apoptotic program is initiated but does not go to completion and does not cause cell death. Nevertheless, this failed apoptosis induces DNA double-strand breaks generating mutations that facilitate tumorigenesis. Whether failed apoptosis is relevant to clinical disease is unknown. BCL-2 interacting killer (BIK) is a stress-induced BH3-only protein that stimulates apoptosis in response to hormone and growth factor deprivation, hypoxia, and genomic stress. It was unclear whether BIK promotes or suppresses tumor survival within the context of breast cancer. We investigated this and show that BIK induces failed apoptosis with limited caspase activation and genomic damage in the absence of extensive cell death. Surviving cells acquire aggressive phenotypes characterized by enrichment of cancer stem-like cells, increased motility and increased clonogenic survival. Furthermore, by examining six independent cohorts of patients (total n = 969), we discovered that high BIK mRNA and protein levels predicted clinical relapse of Estrogen receptor (ER)-positive cancers, which account for almost 70% of all breast cancers diagnosed but had no predictive value for hormone receptor-negative (triple-negative) patients. Thus, this study identifies BIK as a biomarker for tumor recurrence of ER-positive patients and provides a potential mechanism whereby failed apoptosis contributes to cancer aggression.

The Crosstalk Between Cell Adhesion and Cancer Metabolism

Cancer cells preferentially use aerobic glycolysis over mitochondria oxidative phosphorylation for energy production, and this metabolic reprogramming is currently recognized as a hallmark of cancer. Oncogenic signaling frequently converges with this metabolic shift, increasing cancer cells' ability to produce building blocks and energy, as well as to maintain redox homeostasis. Alterations in cell-cell and cell-extracellular matrix (ECM) adhesion promote cancer cell invasion, intravasation, anchorage-independent survival in circulation, and extravasation, as well as homing in a distant organ. Importantly, during this multi-step metastatic process, cells need to induce metabolic rewiring, in order to produce the energy needed, as well as to impair oxidative stress. Although the individual implications of adhesion molecules and metabolic reprogramming in cancer have been widely explored over the years, the crosstalk between cell adhesion molecular machinery and metabolic pathways is far from being clearly understood, in both normal and cancer contexts. This review summarizes our understanding about the influence of cell-cell and cell-matrix adhesion in the metabolic behavior of cancer cells, with a special focus concerning the role of classical cadherins, such as Epithelial (E)-cadherin and Placental (P)-cadherin.

Heterogeneity and Plasticity of Breast Cancer Stem Cells

In the last 20 years, the conventional view of breast cancer as a homogeneous collection of highly proliferating malignant cells was totally replaced by a model of increased complexity, which points out that breast carcinomas are tissues composed of multiple populations of transformed cells. A large diversity of host cells and structural components of the extracellular matrix constitute the mammary tumour microenvironment, which supports its growth and progression, where individual cancer cells evolve with cumulative phenotypic and genetic heterogeneity. Moreover, contributing to this heterogeneity, it has been demonstrated that breast cancers can exhibit a hierarchical organization composed of tumour cells displaying divergent lineage biomarkers and where, at the apex of this hierarchy, some neoplastic cells are able to self-renew and to aberrantly differentiate. Breast cancer stem cells (BCSCs), as they were entitled, not only drive tumourigenesis, but also mediate metastasis and contribute to therapy resistance.Recently, adding more complexity to the system, it has been demonstrated that BCSCs maintain high levels of plasticity, being able to change between mesenchymal-like and epithelial-like states in a process regulated by the tumour microenvironment. These stem cell state transitions play a fundamental role in the process of tumour metastasis, as well as in the resistance to putative therapeutic strategies to target these cells. In this chapter, it will be mainly discussed the emerging knowledge regarding the contribution of BCSCs to tumour heterogeneity, their plasticity, and the role that this plasticity can play in the establishment of distant metastasis. A major focus will also be given to potential clinical implications of these discoveries in breast cancer recurrence and to possible BCSC targeted therapeutics by the use of specific biomarkers.

Perturbing the Dynamics and Organization of Cell Membrane Components: A New Paradigm for Cancer-Targeted Therapies

Cancer is a multi-process disease where different mechanisms exist in parallel to ensure cell survival and constant adaptation to the extracellular environment. To adapt rapidly, cancer cells re-arrange their plasma membranes to sustain proliferation, avoid apoptosis and resist anticancer drugs. In this review, we discuss novel approaches based on the modifications and manipulations that new classes of molecules can exert in the plasma membrane lateral organization and order of cancer cells, affecting growth factor signaling, invasiveness, and drug resistance. Furthermore, we present azurin, an anticancer protein from bacterial origin, as a new approach in the development of therapeutic strategies that target the cell membrane to improve the existing standard therapies.

SRC inhibition prevents P-cadherin mediated signaling and function in basal-like breast cancer cells

BACKGROUND

Basal-like breast cancer (BLBC) is a poor prognosis subgroup of triple-negative carcinomas that still lack specific target therapies and accurate biomarkers for treatment selection. P-cadherin is frequently overexpressed in these tumors, promoting cell invasion, stem cell activity and tumorigenesis by the activation of Src-Family kinase (SRC) signaling. Therefore, our aim was to evaluate if the treatment of BLBC cells with dasatinib, the FDA approved SRC inhibitor, would impact on P-cadherin induced tumor aggressive behavior.

METHODS

P-cadherin and SRC expression was evaluated in a series of invasive Breast Cancer and contingency tables and chi-square tests were performed. Cell-cell adhesion measurements were performed by Atomic Force Microscopy, where frequency histograms and Gaussian curves were applied. 2D and 3D cell migration and invasion, proteases secretion and self-renew potential were evaluated in vitro. Student's t-tests were used to determine statistically significant differences. The cadherin/catenin complex interactions were evaluated by in situ proximity-ligation assay, and statistically significant results were determined by using Mann-Whitney test with a Bonferroni correction. In vivo xenograft mouse models were used to evaluate the impact of dasatinib on tumor growth and survival. ANOVA test was used to evaluate the differences in tumor size, considering a confidence interval of 95%. Survival curves were estimated by the Kaplan-Meier's method, using the log-rank test to assess significant differences for mice overall survival.

RESULTS

Our data demonstrated that P-cadherin overexpression is significantly associated with SRC activation in breast cancer cells, which was also validated in a large series of primary tumor samples. SRC activity suppression with dasatinib significantly prevented the in vitro functional effects of P-cadherin overexpressing cells, as well as their in vivo tumorigenic and metastatic ability, by increasing mice overall survival. Mechanistically, SRC inhibition affects P-cadherin downstream signaling, rescues the E-cadherin/p120-catenin complex to the cell membrane, recovering cell-cell adhesion function.

CONCLUSIONS

In conclusion our findings show that targeting P-cadherin/SRC signaling and functional activity may open novel therapeutic opportunities for highly aggressive and poor prognostic basal-like breast cancer.

Lung squamous cell carcinoma cells express non-canonically glycosylated IgG that activates integrin-FAK signaling

It is increasingly recognized that many human carcinomas express immunoglobulin (Ig) molecules that are distinct from B-cell-derived Ig and play important roles in cancer initiation, progression, and metastasis. However, the molecular mechanisms underlying the functions of cancer-derived Ig remain elusive. Here, we report that lung squamous cell carcinoma (LSCC) cells frequently express high levels of cancer IgG (CIgG) that is specifically recognized by a monoclonal antibody RP215. RP215 recognizes CIgG via a novel epitope that involves an N-glycan modification at a non-consensus site within the C_H1 domain. We demonstrate that RP215 recognized CIgG (RP215-CIgG) promotes survival, migration and in vivo growth of LSCC cells, and these oncogenic activities are strongly inhibited by RP215. Mechanistically, RP215-CIgG executes its oncogenic function through interacting with the integrin α6β4 complex and activating the FAK and Src pathways. Notably, the CIgG-integrin-FAK signaling depends on the N-glycan epitope, which is inhibited by RP215. Together, our studies identified a novel CIgG molecule that activates the oncogenic integrin-FAK signaling in LSCC cells. In addition, the activity of CIgG is inhibited by RP215, providing an attractive target for antibody-based therapy of LSCC.

Slug/Pcad pathway controls epithelial cell dynamics in mammary gland and breast carcinoma

Mammary gland morphogenesis results from the coordination of proliferation, cohort migration, apoptosis and stem/progenitor cell dynamics. We showed earlier that the transcription repressor Slug is involved in these functions during mammary tubulogenesis. Slug is expressed by a subpopulation of basal epithelial cells, co-expressed with P-cadherin (Pcad). Slug-knockout mammary glands showed excessive branching, similarly to Pcad-knockout. Here, we found that Slug unexpectedly binds and activates Pcad promoter through E-boxes, inducing Pcad expression. We determined that Pcad can mediate several functions of Slug: Pcad promoted clonal mammosphere growth, basal epithelial differentiation, cell-cell dissociation and cell migration, rescuing Slug depletion. Pcad also promoted cell migration in isolated cells, in association with Src activation, focal adhesion reorganization and cell polarization. Pcad, similarly to Slug, was required for in vitro 3D tubulogenesis. Therefore, Pcad appears to be responsible for epithelial-mesenchymal transition-linked plasticity in mammary epithelial cells. In addition, we found that genes from the Slug/Pcad pathway components were co-expressed and specifically correlated in human breast carcinomas subtypes, carrying pathophysiological significance.

P-cadherin: a useful biomarker for axillary-based breast cancer decisions in the clinical practice

Axillary lymph node metastases represent the most powerful breast cancer prognostic factor, dictating disease staging and clinical therapeutic decisions. Nonetheless, breast cancer patients with positive lymph nodes still exhibit a heterogeneous behavior regarding disease progression. Stem-like subpopulations of cancer cells show high migratory and metastatic capacity, thus we hypothesize that breast cancer stem cell markers evaluation in metastasized lymph nodes could provide a more accurate prediction of patient's prognosis. Therefore, the expression profile of P-cadherin, CD44, and CD49f, which have been already associated to stem cell properties in breast cancer, has been evaluated by immunohistochemistry in a series of 135 primary tumors and matched axillary lymph node metastases from 135 breast cancer patients. Taking in consideration the expression of the stem cell markers only in axillary nodes, P-cadherin was the only biomarker significantly associated with poor disease-free and overall patient's survival. Moreover, although a concordant expression between primary tumors and matched lymph nodes has been found in the majority of the cases, a small but significant percentage displayed divergent expression (18.2-26.2%). Remarkably, although CD44 and CD49f changes between primary tumors and lymph node metastasis did not impact survival, the cases that were positive for P-cadherin in lymph node metastases being negative in the primary tumor, presented the worst disease-free and overall survival of the whole series. Accordingly, negative cases for this marker in the lymph nodes with positive expression in the matched breast carcinoma demonstrated a better prognosis, which overlapped with tumors that were negative in both sites. P-cadherin and CD49f gain of expression was mainly found in triple-negative carcinomas. Our results indicate for the first time that the evaluation of P-cadherin expression in lymph node metastases is an important predictor of disease outcome, being a putative valuable marker for axillary-based breast cancer decisions in the clinical practice.

Prognostic value of stromal tumour infiltrating lymphocytes and programmed cell death-ligand 1 expression in breast cancer

AIM

The present work aims to evaluate the presence of stromal tumour-infiltrating lymphocytes (TILs) and programmed cell death-ligand 1 (PDL1) expression in breast carcinomas and their correlation with available clinicopathological features.

METHODS

Two independent series of invasive breast cancer (IBC), one including ductal carcinoma in situ (DCIS) pair-matched cases, were selected, and quantification of TILs was accomplished in each case. Immunohistochemistry was also performed to evaluate the expression of PDL1.

RESULTS

In both cohorts evaluated, increased stromal TILs and PDL1 expression were present in about 10% of IBCs, being significantly associated with each other and both with grade 3 and triple-negative subtype. We observed a similar distribution of stromal TILs and PDL1 expression between DCIS and IBC. Finally, we observed that increased stromal TILs and PDL1 expression were significantly associated with cancer stem cell (CSC) markers, basal cell markers and vimentin expression. Interestingly, in IBC cases with vimentin expression, increased stromal TILs, as well as decreased PDL1 expression, disclosed a better clinical outcome, independently of the main classical BC prognostic factors.

CONCLUSIONS

We have confirmed the association of stromal TILs and PDL1 expression with aggressive forms of BC and that both are already found in in situ stages. We also showed that stromal TILs and PDL1 expression are associated with clinical outcome in cases enriched for a mesenchymal immunophenotype. We describe for the first time a close relationship between CSC markers and PDL1 expression.

Membrane translocation of t-SNARE protein syntaxin-4 abrogates ground-state pluripotency in mouse embryonic stem cells

Embryonic stem (ES) and induced pluripotent stem (iPS) cells are attractive tools for regenerative medicine therapies. However, aberrant cell populations that display flattened morphology and lose ground-state pluripotency often appear spontaneously, unless glycogen synthase kinase 3β (GSK3β) and mitogen-activated protein kinase kinase (MEK1/2) are inactivated. Here, we show that membrane translocation of the t-SNARE protein syntaxin-4 possibly is involved in this phenomenon. We found that mouse ES cells cultured without GSK3β/MEK1/2 inhibitors (2i) spontaneously extrude syntaxin-4 at the cell surface and that artificial expression of cell surface syntaxin-4 induces appreciable morphological changes and mesodermal differentiation through dephosphorylation of Akt. Transcriptome analyses revealed several candidate elements responsible for this, specifically, an E-to P-cadherin switch and a marked downregulation of Zscan4 proteins, which are DNA-binding proteins essential for ES cell pluripotency. Embryonic carcinoma cell lines F9 and P19CL6, which maintain undifferentiated states independently of Zscan4 proteins, exhibited similar cellular behaviors upon stimulation with cell surface syntaxin-4. The functional ablation of E-cadherin and overexpression of P-cadherin reproduced syntaxin-4-induced cell morphology, demonstrating that the E- to P-cadherin switch executes morphological signals from cell surface syntaxin-4. Thus, spontaneous membrane translocation of syntaxin-4 emerged as a critical element for maintenance of the stem-cell niche.

Atomic force microscopy and graph analysis to study the P-cadherin/SFK mechanotransduction signalling in breast cancer cells

Physical forces mediated by cell-cell adhesion molecules, as cadherins, play a crucial role in preserving normal tissue architecture. Accordingly, altered cadherins' expression has been documented as a common event during cancer progression. However, in most studies, no data exist linking pro-tumorigenic signaling and variations in the mechanical balance mediated by adhesive forces. In breast cancer, P-cadherin overexpression increases in vivo tumorigenic ability, as well as in vitro cell invasion, by activating Src family kinase (SFK) signalling. However, it is not known how P-cadherin and SFK activation impact cell-cell biomechanical properties. In the present work, using atomic force microscopy (AFM) images, cell stiffness and cell-cell adhesion measurements, and undirected graph analysis based on microscopic images, we have demonstrated that P-cadherin overexpression promotes significant alterations in cell's morphology, by decreasing cellular height and increasing its area. It also affects biomechanical properties, by decreasing cell-cell adhesion and cell stiffness. Furthermore, cellular network analysis showed alterations in intercellular organization, which is associated with cell-cell adhesion dysfunction, destabilization of an E-cadherin/p120ctn membrane complex and increased cell invasion. Remarkably, inhibition of SFK signaling, using dasatinib, reverted the pathogenic P-cadherin induced effects by increasing cell's height, cell-cell adhesion and cell stiffness, and generating more compact epithelial aggregates, as quantified by intercellular network analysis. In conclusion, P-cadherin/SFK signalling induces topological, morphological and biomechanical cell-cell alterations, which are associated with more invasive breast cancer cells. These effects could be further reverted by dasatinib treatment, demonstrating the applicability of AFM and cell network diagrams for measuring the epithelial biomechanical properties and structural organization.

Penfluridol Represses Integrin Expression in Breast Cancer through Induction of Reactive Oxygen Species and Downregulation of Sp Transcription Factors

It was recently demonstrated the penfluridol inhibited breast tumor growth and metastasis and this was associated with downregulation of α6- and β4-integrins. In this study, we observed the penfluridol induced reactive oxygen species (ROS) and this was the primary mechanism of action. Penfluridol-mediated growth inhibition, induction of apoptosis, and inhibition of breast cancer cell migration was attenuated after cotreatment with glutathione. Penfluridol also downregulated Sp transcription factors Sp1, Sp3, and Sp4 through epigenetic downregulation of cMyc and cMyc-regulated miRNAs (miR27a and miR20a/miR17) and induction of the miR-regulated Sp transcriptional repressors ZBTB10 and ZBTB4. α6- and β4-integrins as well as α5- and β1-integrins are Sp-regulated genes that are also coregulated by the orphan nuclear receptor NR4A1 and these integrins can be targeted by agents such as penfluridol that suppress Sp1, Sp3, and Sp4 and also by NR4A1 antagonists. Mol Cancer Ther; 16(1); 205-16. ©2016 AACR.

Pancreatic cancer stem cell markers and exosomes - the incentive push

Pancreatic cancer (PaCa) has the highest death rate and incidence is increasing. Poor prognosis is due to late diagnosis and early metastatic spread, which is ascribed to a minor population of so called cancer stem cells (CSC) within the mass of the primary tumor. CSC are defined by biological features, which they share with adult stem cells like longevity, rare cell division, the capacity for self renewal, differentiation, drug resistance and the requirement for a niche. CSC can also be identified by sets of markers, which for pancreatic CSC (Pa-CSC) include CD44v6, c-Met, Tspan8, alpha6beta4, CXCR4, CD133, EpCAM and claudin7. The functional relevance of CSC markers is still disputed. We hypothesize that Pa-CSC markers play a decisive role in tumor progression. This is fostered by the location in glycolipid-enriched membrane domains, which function as signaling platform and support connectivity of the individual Pa-CSC markers. Outside-in signaling supports apoptosis resistance, stem cell gene expression and tumor suppressor gene repression as well as miRNA transcription and silencing. Pa-CSC markers also contribute to motility and invasiveness. By ligand binding host cells are triggered towards creating a milieu supporting Pa-CSC maintenance. Furthermore, CSC markers contribute to the generation, loading and delivery of exosomes, whereby CSC gain the capacity for a cell-cell contact independent crosstalk with the host and neighboring non-CSC. This allows Pa-CSC exosomes (TEX) to reprogram neighboring non-CSC towards epithelial mesenchymal transition and to stimulate host cells towards preparing a niche for metastasizing tumor cells. Finally, TEX communicate with the matrix to support tumor cell motility, invasion and homing. We will discuss the possibility that CSC markers are the initial trigger for these processes and what is the special contribution of CSC-TEX.

Elevated integrin α6β4 expression is associated with venous invasion and decreased overall survival in non-small cell lung cancer

Lung cancer carries a poor prognosis and is the most common cause of cancer-related death worldwide. The integrin α6β4, a laminin receptor, promotes carcinoma progression in part by cooperating with various growth factor receptors to facilitate invasion and metastasis. In carcinoma cells with mutant TP53, the integrin α6β4 promotes cell survival. TP53 mutations and integrin α6β4 overexpression co-occur in many aggressive malignancies. Because of the high frequency of TP53 mutations in lung squamous cell carcinoma (SCC), we sought to investigate the association of integrin β4 expression with clinicopathologic features and survival in non-small cell lung cancer (NSCLC). We constructed a lung cancer tissue microarray and stained sections for integrin β4 subunit expression using immunohistochemistry. We found that integrin β4 expression is elevated in SCC compared with adenocarcinoma (P<.0001), which was confirmed in external gene expression data sets (P<.0001). We also determined that integrin β4 overexpression associates with the presence of venous invasion (P=.0048) and with reduced overall patient survival (hazard ratio, 1.46; 95% confidence interval, 1.01-2.09; P=.0422). Elevated integrin β4 expression was also shown to associate with reduced overall survival in lung cancer gene expression data sets (hazard ratio, 1.49; 95% confidence interval, 1.31-1.69; P<.0001). Using cBioPortal, we generated a network map demonstrating the 50 most highly altered genes neighboring ITGB4 in SCC, which included laminins, collagens, CD151, genes in the EGFR and PI3K pathways, and other known signaling partners. In conclusion, we demonstrate that integrin β4 is overexpressed in NSCLC where it is an adverse prognostic marker.

What Kind of Signaling Maintains Pluripotency and Viability in Human-Induced Pluripotent Stem Cells Cultured on Laminin-511 with Serum-Free Medium?

Xeno-free medium contains no animal-derived components, but is composed of minimal growth factors and is serum free; the medium may be supplemented with insulin, transferrin, and selenium (ITS medium). Serum-free and xeno-free culture of human-induced pluripotent stem cells (hiPSCs) uses a variety of components based on ITS medium and Dulbecco's modified Eagle's medium/Ham's nutrient mixture F12 (DMEM/F12) that contain high levels of iron salt and glucose. Culture of hiPSCs also requires scaffolding materials, such as extracellular matrix, collagen, fibronectin, laminin, proteoglycan, and vitronectin. The scaffolding component laminin-511, which is composed of α5, β1, and γ1 chains, binds to α3β1, α6β1, and α6β4 integrins on the cell membrane to induce activation of the PI3K/AKT- and Ras/MAPK-dependent signaling pathways. In hiPSCs, the interaction of laminin-511/α6β1 integrin with the cell–cell adhesion molecule E-cadherin confers protection against apoptosis through the Ras homolog gene family member A (RhoA)/Rho kinase (ROCK) signaling pathway (the major pathways for cell death) and the proto-oncogene tyrosine-protein kinase Fyn (Fyn)-RhoA-ROCK signaling pathway. The expression levels of α6β1 integrin and E-cadherin on cell membranes are controlled through the activation of insulin receptor/insulin, FGF receptor/FGF2, or activin-like kinase 5 (ALK5)-dependent TGF-β signaling. A combination of growth factors, medium constituents, cell membrane-located E-cadherin, and α6β1 integrin-induced signaling is required for pluripotent cell proliferation and for optimal cell survival on a laminin-511 scaffold. In this review, we discuss and explore the influence of growth factors on the cadherin and integrin signaling pathways in serum-free and xeno-free cultures of hiPSCs during the preparation of products for regenerative medicinal therapies. In addition, we suggest the optimum serum-free medium components for use with laminin-511, a new scaffold for hiPSC culture.

Estrogen Enhances the Cell Viability and Motility of Breast Cancer Cells through the ERα-ΔNp63-Integrin β4 Signaling Pathway

Estrogen induces ERα-positive breast cancer aggressiveness via the promotion of cell proliferation and survival, the epithelial-mesenchymal transition, and stem-like properties. Integrin β4 signaling has been implicated in estrogen/ERα-induced tumorigenicity and anti-apoptosis; however, this signaling cascade poorly understood. ΔNp63, an N-terminally truncated isoform of the p63 transcription factor, functions as a transcription factor of integrinβ4 and therefore regulates cellular adhesion and survival. Therefore, the aim of the present study was to investigate the estrogen-induced interaction between ERα, ΔNp63 and integrin β4 in breast cancer cells. In ERα-positive MCF-7 cells, estrogen activated ERα transcription, which induced ΔNp63 expression. And ΔNp63 subsequently induced integrin β4 expression, which resulted in AKT phosphorylation and enhanced cell viability and motility. Conversely, there was no inductive effect of estrogen on ΔNp63-integrinβ4-AKT signaling or on cell viability and motility in ERα-negative MDA-MB-231 cells. ΔNp63 knockdown abolishes these estrogen-induced effects and reduces cell viability and motility in MCF-7 cells. Nevertheless, ΔNp63 knockdown also inhibited cell migration in MDA-MB-231 cells through reducing integrin β4 expression and AKT phosphorylation. In conclusion, estrogen enhances ERα-positive breast cancer cell viability and motility through activating the ERα-ΔNp63-integrin β4 signaling pathway to induce AKT phosphorylated activation. Those findings should be useful to elucidate the crosstalk between estrogen/ER signaling and ΔNp63 signaling and provide novel insights into the effects of estrogen on breast cancer progression.

P-cadherin and the journey to cancer metastasis

P-cadherin is a classical cell-to-cell adhesion molecule with a homeostatic function in several normal tissues. However, its behaviour in the malignant setting is notably dependent on the cellular context. In some tumour models, such as melanoma and oral squamous cell carcinoma, P-cadherin acts as a tumour suppressor, since its absence is associated with a more aggressive cancer cell phenotype; nevertheless, the overexpression of this molecule is linked to significant tumour promoting effects in the breast, ovarian, prostate, endometrial, skin, gastric, pancreas and colon neoplasms. Herein, we review the role of P-cadherin in cancer cell invasion, as well as in loco-regional and distant metastatic dissemination. We focus in P-cadherin signalling pathways that are activated to induce invasion and metastasis, as well as cancer stem cell properties. The signalling network downstream of P-cadherin is notably dependent on the cellular and tissue context and includes the activation of integrin molecules, receptor tyrosine kinases, small molecule GTPases, EMT transcription factors, and crosstalk with other cadherin family members. As new oncogenic molecular pathways mediated by P-cadherin are uncovered, putative therapeutic options can be tested, which will allow for the targeting of invasion or metastatic disease, depending on the tumour model.

The potential of Beclin 1 as a therapeutic target for the treatment of breast cancer

INTRODUCTION

Beclin 1 plays a crucial role in autophagy via the Beclin 1 interactome, and is involved in various biological processes such as protein sorting, chemokinesis, and cell death. Via these biologic functions, Beclin 1 contributes to both tumor suppression and tumor progression.

AREAS COVERED

Beclin 1 plays a key biologic function on cell homeostasis and affects tumorigenesis. In this review, detailing up-to-date knowledge on the tumorigenic role of Beclin 1, its implication in breast cancer, and its utility as a breast cancer-specific drug target is discussed.

EXPERT OPINION

Because Beclin 1 is expressed in breast cancer cells, Beclin 1 could be a unique, effective drug target for the prevention and treatment of breast cancer. However, the expression of Beclin 1 varies according to cancer molecular subtypes, and Beclin 1 is involved in both breast cancer suppression and tumor progression; therefore, the decision of using a Beclin 1 inducer or inhibitor should be made based on breast cancer stage and subtype.

β1 and β4 integrins: from breast development to clinical practice

Following a highly dynamic and complex dialogue between the epithelium and the surrounding microenvironment, the mammary gland develops into a branching structure during puberty, buds during pregnancy, forms intricate polar acini during lactation and, once the babies are weaned, remodels and involutes. At every stage of menstrual and pregnancy cycles, interactions between the cells and the extracellular matrix (ECM) and homotypic and heterotypic cell–cell interactions give rise to the architecture and function of the gland at that junction. These orchestrated programs would not be possible without the important role of the ECM receptors, integrins being the prime examples. The ECM–integrin axis regulates many crucial cellular functions including survival, migration and quiescence; the imbalance in any of these processes could contribute to oncogenesis. In this review we spotlight the involvement of two prominent integrin subunits, β1 and β4 integrins, in cross-talk with tyrosine kinase receptors, and we discuss the roles of these integrin subunits in the biology of normal breast differentiation and as potential prognostic and therapeutic targets in breast cancer.

Convergence of eicosanoid and integrin biology: 12-lipoxygenase seeks a partner

Background

Integrins and enzymes of the eicosanoid pathway are both well-established contributors to cancer. However, this is the first report of the interdependence of the two signaling systems. In a screen for proteins that interacted with, and thereby potentially regulated, the human platelet-type 12-lipoxygenase (12-LOX, ALOX12), we identified the integrin β4 (ITGB4).

Methods

Using a cultured mammalian cell model, we have demonstrated that ITGB4 stimulation leads to recruitment of 12-LOX from the cytosol to the membrane where it physically interacts with the integrin to become enzymatically active to produce 12(S)-HETE, a known bioactive lipid metabolite that regulates numerous cancer phenotypes.

Results

The net effect of the interaction was the prevention of cell death in response to starvation. Additionally, regulation of β4-mediated, EGF-stimulated invasion was shown to be dependent on 12-LOX, and downstream Erk signaling in response to ITGB4 activation also required 12-LOX.

Conclusions

This is the first report of an enzyme of the eicosanoid pathway being recruited to and regulated by activated β4 integrin. Integrin β4 has recently been shown to induce expansion of prostate tumor progenitors and there is a strong correlation between stage/grade of prostate cancer and 12-LOX expression. The 12-LOX enzymatic product, 12(S)-HETE, regulates angiogenesis and cell migration in many cancer types. Therefore, disruption of integrin β4-12LOX interaction could reduce the pro-inflammatory oncogenic activity of 12-LOX. This report on the consequences of 12-LOX and ITGB4 interaction sets a precedent for the linkage of integrin and eicosanoid biology through direct protein-protein association.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0382-5) contains supplementary material, which is available to authorized users.

P-Cadherin Linking Breast Cancer Stem Cells and Invasion: A Promising Marker to Identify an "Intermediate/Metastable" EMT State

Epithelial–mesenchymal transition (also known as EMT) is a fundamental mechanism occurring during embryonic development and tissue differentiation, being also crucial for cancer progression. Actually, the EMT program contributes to the dissemination of cancer cells from solid tumors and to the formation of micro-metastasis that subsequently develop into clinically detectable metastases. Besides being a process that is defined by the progressive loss of epithelial cell characteristics and the acquisition of mesenchymal features, EMT has also been implicated in therapy resistance, immune escape, and maintenance of cancer stem cell properties, such as self-renewal capacity. However, the majority of the studies usually neglect the progressive alterations occurring during intermediate EMT states, which imply a range of phenotypic cellular heterogeneity that can potentially generate more metastable and plastic tumor cells. In fact, few studies have tried to identify these transitory states, partly due to the current lack of a detailed understanding of EMT, as well as of reliable readouts for its progression. Herein, a brief review of evidences is presented, showing that P-cadherin expression, which has been already identified as a breast cancer stem cell marker and invasive promoter, is probably able to identify an intermediate EMT state associated with a metastable phenotype. This hypothesis is based on our own work, as well as on the results described by others, which suggest the use of P-cadherin as a promising EMT marker, clearly functioning as an important clinical prognostic factor and putative therapeutic target in breast carcinogenesis.

Aberrant P-cadherin expression is associated to aggressive feline mammary carcinomas

BACKGROUND

Cadherins are calcium-dependent cell-to-cell adhesion glycoproteins playing a critical role in the formation and maintenance of normal tissue architecture. In normal mammary gland, E-cadherin is expressed by luminal epithelial cells, while P-cadherin is restricted to myoepithelial cells. Changes in the expression of classical E- and P-cadherins have been observed in mammary lesions and related to mammary carcinogenesis. P-cadherin and E-cadherin expressions were studied in a series of feline normal mammary glands, hyperplastic/dysplastic lesions, benign and malignant tumours by immunohistochemistry and double-label immunofluorescence.

RESULTS

In normal tissue and in the majority of hyperplastic/dysplastic lesions and benign tumours, P-cadherin was restricted to myoepithelial cells, while 80% of the malignant tumours expressed P-cadherin in luminal epithelial cells. P-cadherin expression was significantly related to high histological grade of carcinomas (p <0.0001), tumour necrosis (p = 0.001), infiltrative growth (p = 0.0051), and presence of neoplastic emboli (p = 0.0401). Moreover, P-cadherin positive carcinomas had an eightfold likelihood of developing neoplastic emboli than negative tumours. Cadherins expression profile in high grade and in infiltrative tumours was similar, the majority expressing P-cadherin, regardless of E-cadherin expression status. The two cadherins were found to be co-expressed in carcinomas with aberrant P-cadherin expression and preserved E-cadherin.

CONCLUSIONS

The results demonstrate a relationship between P-cadherin expression and aggressive biological behaviour of feline mammary carcinomas, suggesting that P-cadherin may be considered an indicator of poor prognosis in this animal species. Moreover, it indicates that, in queens, the aberrant expression of P-cadherin is a better marker of mammary carcinomas aggressive behaviour than the reduction of E-cadherin expression. Further investigation with follow-up studies in feline species should be conducted in order to evaluate the prognostic value of P-cadherin expression in E-cadherin positive carcinomas.