Alterations in the cadherin-catenin adhesion complexes are involved in tumor initiation, progression and metastasis. However, the functional implication of distinct cadherin types in breast cancer biology is still poorly understood.

The human ghrelin gene, which encodes the ghrelin and obestatin peptides, contains 5 exons (Ex), with Ex1-Ex4 encoding a 117 amino-acid (aa) preproprotein that is known to be processed to yield a 28-aa (ghrelin) and/or a 23-aa (obestatin) mature peptides, which possess biological activities in multiple tissues. However, the ghrelin gene also encodes additional peptides through alternative splicing or post-translational modifications. Indeed, we previously identified a spliced mRNA ghrelin variant in mouse (In2-ghrelin-variant), which is regulated in a tissue-dependent manner by metabolic status and may thus be of biological relevance. Here, we have characterized a new human ghrelin variant that contains Ex0-1, intron (In) 1, and Ex2 and lacks Ex3-4. This human In1-ghrelin variant would encode a new prepropeptide that conserves the first 12aa of native-ghrelin (including the Ser3-potential octanoylation site) but has a different C-terminal tail. Expression of In1-variant was detected in 22 human tissues and its levels were positively correlated with those of ghrelin-O-acyltransferase (GOAT; p = 0.0001) but not with native-ghrelin expression, suggesting that In1-ghrelin could be a primary substrate for GOAT in human tissues. Interestingly, levels of In1-ghrelin variant expression in breast cancer samples were 8-times higher than those of normal mammary tissue, and showed a strong correlation in breast tumors with GOAT (p = 0.0001), ghrelin receptor-type 1b (GHSR1b; p = 0.049) and cyclin-D3 (a cell-cycle inducer/proliferation marker; p = 0.009), but not with native-ghrelin or GHSR1a expression. Interestingly, In1-ghrelin variant overexpression increased basal proliferation of MDA-MB-231 breast cancer cells. Taken together, our results provide evidence that In1-ghrelin is a novel element of the ghrelin family with a potential pathophysiological role in breast cancer.

Squamous cell lung cancer (SCC) and adenocarcinoma are the most common histological subtypes of non-small cell lung cancer (NSCLC), and have been traditionally managed in the clinic as a single entity. Increasing evidence, however, illustrates the biological diversity of these two histological subgroups of lung cancer, and supports the need to improve our understanding of the molecular basis beyond the different phenotypes if we aim to develop more specific and individualized targeted therapy. The purpose of this study was to identify microRNA (miRNA)-dependent transcriptional regulation differences between SCC and adenocarcinoma histological lung cancer subtypes. In this work, paired miRNA (667 miRNAs by TaqMan Low Density Arrays (TLDA)) and mRNA profiling (Whole Genome 44 K array G112A, Agilent) was performed in tumor samples of 44 NSCLC patients. Nine miRNAs and 56 mRNAs were found to be differentially expressed in SCC versus adenocarcinoma samples. Eleven of these 56 mRNA were predicted as targets of the miRNAs identified to be differently expressed in these two histological conditions. Of them, 6 miRNAs (miR-149, miR-205, miR-375, miR-378, miR-422a and miR-708) and 9 target genes (CEACAM6, CGN, CLDN3, ABCC3, MLPH, ACSL5, TMEM45B, MUC1) were validated by quantitative PCR in an independent cohort of 41 lung cancer patients. Furthermore, the inverse correlation between mRNAs and microRNAs expression was also validated. These results suggest miRNA-dependent transcriptional regulation differences play an important role in determining key hallmarks of NSCLC, and may provide new biomarkers for personalized treatment strategies.

Epithelial-to-Mesenchymal Transition (EMT) is a key process contributing to the aggressiveness of cancer cells. EMT is triggered by activation of different transcription factors collectively known as EMT-TFs. Different cellular cues and cell signalling networks activate EMT at transcriptional and posttranscriptional level in different biological and pathological situations. Among them, overexpression of LOXL2 (lysyl oxidase-like 2) induces EMT independent of its catalytic activity. Remarkably, perinuclear/cytoplasmic accumulation of LOXL2 is a poor prognosis marker of squamous cell carcinomas and is associated to basal breast cancer metastasis by mechanisms no yet fully understood. Here, we report that overexpression of LOXL2 promotes its accumulation in the Endoplasmic Reticulum where it interacts with HSPA5 leading to activation of the IRE1-XBP1 signalling pathway of the ER-stress response. LOXL2-dependent IRE1-XBP1 activation induces the expression of several EMT-TFs: SNAI1, SNAI2, ZEB2 and TCF3 that are direct transcriptional targets of XBP1. Remarkably, inhibition of IRE1 blocks LOXL2-dependent upregulation of EMT-TFs thus hindering EMT induction.

Malignant melanoma is a highly aggressive tumor causing most skin cancer-related deaths. Understanding the fundamental mechanisms responsible for melanoma progression and therapeutic evasion is still an unmet need for melanoma patients. Progression of skin melanoma and its dissemination to local or distant organs relies on phenotypic plasticity of melanoma cells, orchestrated by EMT-TFs and microphthalmia-associated TF (MITF). Recently, melanoma phenotypic switching has been proposed to uphold context-dependent intermediate cell states benefitting malignancy. LOXL3 (lysyl oxidase-like 3) promotes EMT and has a key role in human melanoma cell survival and maintenance of genomic integrity. To further understand the role of Loxl3 in melanoma, we generated a conditional Loxl3-knockout (KO) melanoma mouse model in the context of BrafV600E-activating mutation and Pten loss. Melanocyte-Loxl3 deletion increased melanoma latency, decreased tumor growth, and reduced lymph node metastatic dissemination. Complementary in vitro and in vivo studies in mouse melanoma cells confirmed Loxl3's contribution to melanoma progression and metastasis, in part by modulating phenotypic switching through Snail1 and Prrx1 EMT-TFs. Importantly, a novel LOXL3-SNAIL1-PRRX1 axis was identified in human melanoma, plausibly relevant to melanoma cellular plasticity. These data reinforced the value of LOXL3 as a therapeutic target in melanoma.

Gasdermin B (GSDMB) over-expression promotes poor prognosis and aggressive behavior in HER2 breast cancer by increasing resistance to therapy. Decoding the molecular mechanism of GSDMB-mediated drug resistance is crucial to identify novel effective targeted treatments for HER2/GSDMB aggressive tumors.

The induction of pluripotency by enforced expression of different sets of genes in somatic cells has been achieved with reprogramming technologies first described by Yamanaka's group. Methodologies for generating induced pluripotent stem cells are as varied as the combinations of genes used. It has previously been reported that the adenoviral E1a gene can induce the expression of two of the Yamanaka factors (c-Myc and Oct-4) and epigenetic changes. Here, we demonstrate that the E1a-12S over-expression is sufficient to induce pluripotent-like characteristics closely to epiblast stem cells in mouse embryonic fibroblasts through the activation of the pluripotency gene regulatory network. These findings provide not only empirical evidence that the expression of one single factor is sufficient for partial reprogramming but also a potential mechanistic explanation for how viral infection could lead to neoplasia if they are surrounded by the appropriate environment or the right medium, as happens with the tumorogenic niche.

E12/E47 proteins (encoded by E2A gene) are members of the class I basic helix-loop-helix (bHLH) transcription factors (also known as E proteins). E47 has been described as repressor of E-cadherin and inducer of epithelial-mesenchymal transition (EMT). We reported previously that EMT mediated by E47 in MDCK cells occurs with a concomitant overexpression of Id1 and Id3 proteins. Id proteins belong to class V of HLH factors that lack the basic domain; they dimerise with E proteins and prevent their DNA interaction, thus, acting as dominant negative of E proteins. Here, we show that E47 interacts with Id1 in E47 overexpressing MDCK cells that underwent a full EMT as well as in mesenchymal breast carcinoma and melanoma cell lines. By conducting chromatin immunoprecipitation assays we demonstrate that E47 binds directly to the endogenous E-cadherin promoter of mesenchymal MDCK-E47 cells in a complex devoid of Id1. Importantly, our data suggest that both E47 and Id1 are required to maintain the mesenchymal phenotype of MDCK-E47 cells. These data support the collaboration between E47 and Id1 in the maintenance of EMT by mechanisms independent of the dominant negative action of Id1 on E47 binding to E-cadherin promoter. Finally, the analysis of several N0 breast tumour series indicates that the expression of E47 and ID1 is significantly associated with the basal-like phenotype supporting the biological significance of the present findings.

The orphan G protein-coupled receptor GPR55 has been directly or indirectly related to basic alterations that drive malignant growth: uncontrolled cancer cell proliferation, sustained angiogenesis, and cancer cell adhesion and migration. However, little is known about the involvement of this receptor in metastasis. Here, we show that elevated GPR55 expression in human tumors is associated with the aggressive basal/triple-negative breast cancer population, higher probability to develop metastases, and therefore poor patient prognosis. Activation of GPR55 by its proposed endogenous ligand lysophosphatidylinositol confers pro-invasive features on breast cancer cells both in vitro and in vivo. Specifically, this effect is elicited by coupling to Gq/11 heterotrimeric proteins and the subsequent activation, through ERK, of the transcription factor ETV4/PEA3. Together, these data show that GPR55 promotes breast cancer metastasis, and supports the notion that this orphan receptor may constitute a new therapeutic target and potential biomarker in the highly aggressive triple-negative subtype.

Cancer stem cells (CSC) are considered responsible for tumor initiation, therapeutic resistance, and metastasis. A comprehensive knowledge of the mechanisms governing the acquisition and maintenance of cancer stemness is crucial for the development of new therapeutic approaches in oncology. E2A basic helix-loop-helix (bHLH) transcription factors are associated with epithelial-mesenchymal transition (EMT) and tumor progression, but knowledge of their functional contributions to cancer biology is still limited. Using a combination of in vivo and in vitro analyses in a novel PyMT-E2A conditional knockout mouse model and derived primary tumor cell lines, we report here an essential role of E2A in stemness, metastasis, and therapeutic resistance in breast cancer. Targeted deletion of E2A in the mammary gland impaired tumor-initiating ability and dedifferentiation potential and severely compromised metastatic competence of PyMT-driven mammary tumors. Mechanistic studies in PyMT-derived cell lines indicated that E2A actions are mediated by the upregulation of Snai1 transcription. Importantly, high E2A and SNAIL1 expression occurred in aggressive human basal-like breast carcinomas, highlighting the relevance of the E2A-Snail1 axis in metastatic breast cancer. In addition, E2A factors contributed to the maintenance of genomic integrity and resistance to PARP inhibitors in PyMT and human triple-negative breast cancer cells. Collectively, these results support the potential for E2A transcription factors as novel targets worthy of translational consideration in breast cancer. SIGNIFICANCE: These findings identify key functions of E2A factors in breast cancer cell stemness, metastasis, and drug resistance, supporting a therapeutic vulnerability to targeting E2A proteins in breast cancer.

Analyzing different tumor regions by next generation sequencing allows the assessment of intratumor genetic heterogeneity (ITGH), a phenomenon that has been studied widely in some tumor types but has been less well explored in endometrial carcinoma (EC). In this study, we sought to characterize the spatial and temporal heterogeneity of 9 different ECs using whole-exome sequencing, and by performing targeted sequencing validation of the 42 primary tumor regions and 30 metastatic samples analyzed. In addition, copy number alterations of serous carcinomas were assessed by comparative genomic hybridization arrays. From the somatic mutations, identified by whole-exome sequencing, 532 were validated by targeted sequencing. Based on these data, the phylogenetic tree reconstructed for each case allowed us to establish the tumors' evolution and correlate this to tumor progression, prognosis, and the presence of recurrent disease. Moreover, we studied the genetic landscape of an ambiguous EC and the molecular profile obtained was used to guide the selection of a potential personalized therapy for this patient, which was subsequently validated by preclinical testing in patient-derived xenograft models. Overall, our study reveals the impact of analyzing different tumor regions to decipher the ITGH in ECs, which could help make the best treatment decision.

The incidence and mortality of endometrial cancer (EC) have risen in recent years, hence more precise management is needed. Therefore, we combined different types of liquid biopsies to better characterize the genetic landscape of EC in a non-invasive and dynamic manner. Uterine aspirates (UAs) from 60 patients with EC were obtained during surgery and analyzed by next-generation sequencing (NGS). Blood samples, collected at surgery, were used for cell-free DNA (cfDNA) and circulating tumor cell (CTC) analyses. Finally, personalized therapies were tested in patient-derived xenografts (PDXs) generated from the UAs. NGS analyses revealed the presence of genetic alterations in 93% of the tumors. Circulating tumor DNA (ctDNA) was present in 41.2% of cases, mainly in patients with high-risk tumors, thus indicating a clear association with a more aggressive disease. Accordingly, the results obtained during the post-surgery follow-up indicated the presence of ctDNA in three patients with progressive disease. Moreover, 38.9% of patients were positive for CTCs at surgery. Finally, the efficacy of targeted therapies based on the UA-specific mutational landscape was demonstrated in PDX models. Our study indicates the potential clinical applicability of a personalized strategy based on a combination of different liquid biopsies to characterize and monitor tumor evolution, and to identify targeted therapies.

Tumor-derived extracellular vesicles (EVs) are secreted in large amounts into biological fluids of cancer patients. The analysis of EVs cargoes has been associated with patient´s outcome and response to therapy. However, current technologies for EVs isolation are tedious and low cost-efficient for routine clinical implementation. To explore the clinical value of circulating EVs analysis we attempted a proof-of-concept in endometrial cancer (EC) with ExoGAG, an easy to use and highly efficient new technology to enrich EVs. Technical performance was first evaluated using EVs secreted by Hec1A cells. Then, the clinical value of this strategy was questioned by analyzing the levels of two well-known tissue biomarkers in EC, L1 cell adhesion molecule (L1CAM) and Annexin A2 (ANXA2), in EVs purified from plasma in a cohort of 41 EC patients and 20 healthy controls. The results demonstrated the specific content of ANXA2 in the purified EVs fraction, with an accurate sensitivity and specificity for EC diagnosis. Importantly, high ANXA2 levels in circulating EVs were associated with high risk of recurrence and non-endometrioid histology suggesting a potential value as a prognostic biomarker in EC. These results also confirmed ExoGAG technology as a robust technique for the clinical implementation of circulating EVs analyses.

Gene therapy has long been proposed for cancer treatment. However, the use of therapeutic nucleic acids presents several limitations such as enzymatic degradation, rapid clearance, and poor cellular uptake and efficiency. In this work we propose the use of putrescine, a precursor for higher polyamine biosynthesis for the preparation of cationic nanosystems for cancer gene therapy. We have formulated and characterized putrescine-sphingomyelin nanosystems (PSN) and studied their endocytic pathway and intracellular trafficking in cancer cells. After loading a plasmid DNA (pDNA) encoding the apoptotic Fas Ligand (FasL), we proved their therapeutic activity by measuring the cell death rate after treatment of MDA-MB-231 cells. We have also used xenografted zebrafish embryos as a first in vivo approach to demonstrate the efficacy of the proposed PSN-pDNA formulation in a more complex model. Finally, intratumoral and intraperitoneal administration to mice-bearing MDA-MB-231 xenografts resulted in a significant decrease in tumour cell growth, highlighting the potential of the developed gene therapy nanoformulation for the treatment of triple negative breast cancer.

ErbB2-positive breast cancer is characterized by highly aggressive phenotypes and reduced responsiveness to standard therapies. Although specific ErbB2-targeted therapies have been designed, only a small percentage of patients respond to these treatments and most of them eventually relapse. The existence of this population of particularly aggressive and non-responding or relapsing patients urges the search for novel therapies. The purpose of this study was to determine whether cannabinoids might constitute a new therapeutic tool for the treatment of ErbB2-positive breast tumors. We analyzed their antitumor potential in a well established and clinically relevant model of ErbB2-driven metastatic breast cancer: the MMTV-neu mouse. We also analyzed the expression of cannabinoid targets in a series of 87 human breast tumors.

Basal-like breast carcinoma is characterized by the expression of basal/myoepithelial markers, undifferentiated phenotype, highly aggressive behaviour and frequent triple negative status (ESR-, PR-, Her2neu-). We have previously shown that epithelial-mesenchymal transition (EMT) occurs in basal-like breast tumours and identified Lysyl-oxidase-like 2 (LOXL2) as an EMT player and poor prognosis marker in squamous cell carcinomas. We now show that LOXL2 mRNA is overexpressed in basal-like human breast carcinomas. Breast carcinoma cell lines with basal-like phenotype show a specific cytoplasmic/perinuclear LOXL2 expression, and this subcellular distribution is significantly associated with distant metastatic incidence in basal-like breast carcinomas. LOXL2 silencing in basal-like carcinoma cells induces a mesenchymal-epithelial transition (MET) associated with a decrease of tumourigenicity and suppression of metastatic potential. Mechanistic studies indicate that LOXL2 maintains the mesenchymal phenotype of basal-like carcinoma cells by a novel mechanism involving transcriptional downregulation of Lgl2 and claudin1 and disorganization of cell polarity and tight junction complexes. Therefore, intracellular LOXL2 is a new candidate marker of basal-like carcinomas and a target to block metastatic dissemination of this aggressive breast tumour subtype.

Snail, a family of transcriptional repressors implicated in cell movement, has been correlated with tumour invasion. The Plasminogen Activation (PA) system, including urokinase plasminogen activator (uPA), its receptor and its inhibitor, plasminogen activator inhibitor type 1(PAI-1), also plays a key role in cancer invasion and metastasis, either through proteolytic degradation or by non-proteolytic modulation of cell adhesion and migration. Thus, Snail and the PA system are both over-expressed in cancer and influence this process. In this study we aimed to determine if the activity of SNAI1 (a member of the Snail family) is correlated with expression of the PA system components and how this correlation can influence tumoural cell migration.

In early stages of metastasis malignant cells must acquire phenotypic changes to enhance their migratory behavior and their ability to breach the matrix surrounding tumors and blood vessel walls. Epigenetic regulation of gene expression allows the acquisition of these features that, once tumoral cells have escape from the primary tumor, can be reverted. Here we report that the expression of the Polycomb epigenetic repressor Ring1B is enhanced in tumoral cells that invade the stroma in human ductal breast carcinoma and its expression is coincident with that of Fak in these tumors. Ring1B knockdown in breast cancer cell lines revealed that Ring1B is required to sustain Fak expression in basal conditions as well as in Tgfβ-treated cells. Functionally, endogenous Ring1B is required for cell migration and invasion in vitro and for in vivo invasion of the mammary fat pad by tumoral cells. Finally we identify p63 as a target of Ring1B to regulate Fak expression: Ring1B depletion results in enhanced p63 expression, which in turns represses Fak expression. Importantly, Fak downregulation upon Ring1B depletion is dependent on p63 expression. Our findings provide new insights in the biology of the breast carcinoma and open new avenues for breast cancer prognosis and therapy.

Gasdermin B (GSDMB) belongs to the Gasdermin protein family that comprises four members (GSDMA-D). Gasdermin B expression has been detected in some tumor types such as hepatocarcinomas, gastric and cervix cancers; and its over-expression has been related to tumor progression. At least four splicing isoforms of GSDMB have been identified, which may play differential roles in cancer. However, the implication of GSDMB in carcinogenesis and tumor progression is not well understood. Here, we uncover for the first time the functional implication of GSDMB in breast cancer. Our data shows that high levels of GSDMB expression is correlated with reduced survival and increased metastasis in breast cancer patients included in an expression dataset (>1,000 cases). We demonstrate that GSDMB is upregulated in breast carcinomas compared to normal breast tissue, being the isoform 2 (GSDMB-2) the most differentially expressed. In order to evaluate the functional role of GSDMB in breast cancer two GSDMB isoforms were studied (GSDMB-1 and GSDMB-2). The overexpression of both isoforms in the MCF7 breast carcinoma cell line promotes cell motility and invasion, while its silencing in HCC1954 breast carcinoma cells decreases the migratory and invasive phenotype. Importantly, we demonstrate that both isoforms have a differential role on the activation of Rac-1 and Cdc-42 Rho-GTPases. Moreover, our data support that GSMDB-2 induces a pro-tumorigenic and pro-metastatic behavior in mouse xenograft models as compared to GSDMB-1. Finally, we observed that although both GSDMB isoforms interact in vitro with the chaperone Hsp90, only the GSDMB-2 isoform relies on this chaperone for its stability. Taken together, our results provide for the first time evidences that GSDMB-2 induces invasion, tumor progression and metastasis in MCF7 cells and that GSDMB can be considered as a new potential prognostic marker in breast cancer.

Epithelial to mesenchymal transition (EMT) induces cell plasticity and promotes metastasis. The multifunctional oncoprotein Y-box binding protein-1 (YB-1) and the pleiotropic cytokine interleukin 6 (IL-6) have both been implicated in tumor cell metastasis and EMT, but via distinct pathways. Here, we show that direct interplay between YB-1 and IL-6 regulates breast cancer metastasis. Overexpression of YB-1 in breast cancer cell lines induced IL-6 production while stimulation with IL-6 increased YB-1 expression and YB-1 phosphorylation. Either approach was sufficient to induce EMT features, including increased cell migration and invasion. Silencing of YB-1 partially reverted the EMT and blocked the effect of IL-6 while inhibition of IL-6 signaling blocked the phenotype induced by YB-1 overexpression, demonstrating a clear YB-1/IL-6 interdependence. Our findings describe a novel signaling network in which YB-1 regulates IL-6, and vice versa, creating a positive feed-forward loop driving EMT-like metastatic features during breast cancer progression. Identification of signaling partners or pathways underlying this co-dependence may uncover novel therapeutic opportunities.