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Epithelial-mesenchymal transition (EMT) has been associated with increased aggressiveness and acquisition of migratory properties providing tumor cells with the ability to invade into adjacent tissues. Downregulation of E-cadherin, a hallmark of EMT, is mediated by several transcription factors (EMT-TFs) that act also as EMT inducers, among them, Snail1 and the bHLH transcription factor E47. We previously described lysyl oxidase-like 2 (LOXL2), a member of the lysyl oxidase family, as a Snail1 regulator and EMT inducer. Here we show that LOXL2 is also an E47-interacting partner and functionally collaborates in the repression of E-cadherin promoter. Loss and gain of function analyses combined with in vivo studies in syngeneic breast cancer models demonstrate the participation of LOXL2 and E47 in tumor growth and their requirement for lung metastasis. Furthermore, LOXL2 and E47 contribute to early steps of metastatic colonization by cell and noncell autonomous functions regulating the recruitment of bone marrow progenitor cells to the lungs and by direct transcriptional regulation of fibronectin and cytokines TNFα, ANG-1 and GM-CSF. Moreover, fibronectin and GM-CSF proved to be necessary for LOXL2/E47-mediated modulation of tumor growth and lung metastasis., The work was supported by the Spanish Ministry of Science and Innovation (SAF2010–21143; Consolider 2007-CS00017); AICR (12–1057) and ISCIII (RETIC- RD12/0036/0007) to AC, and Comunidad de Madrid (S2010/BMD-2302) to AC and GMB. EPC and VS are founded from the AICR grant.

Cyclin D1 is frequently overexpressed in human neoplasias by gene rearrangement and amplification, but no mutations in the CCND1 gene have so far been reported. However, in vitro mutagenesis of CCND1 has shown that substitutions affecting threonine 286 residue produced cyclin D1 nuclear accumulation, by interfering with protein degradation and induced neoplastic transformation in murine fibroblasts. To test whether similar genetic changes may occur in vivo, we analysed a series of 60 endometrioid endometrial carcinomas (EECs) for cyclin D1 expression and gene amplification by immunohistochemistry and FISH, respectively. Two of 17 carcinomas showing cyclin D1 expression in more than 5% of neoplastic cells, but without gene amplification, were found to harbor single-base substitutions in CCND1 that changed proline 287 into threonine and serine, respectively. Both cases expressed cyclin D1 in more than 50% of neoplastic cells. Additionally, seven tumors with cyclin D1 overexpression of an independent series of 59 EECs were also analysed, and a 12-bp in-frame deletion that eliminated amino acids 289-292 was detected in one case with cylin D1 expression in more than 50% of neoplastic cells. In contrast, no mutations of the CCND1 gene were detected in a set of breast carcinomas with cyclin D1 overexpression without gene amplification. In summary, our data indicate that mutations of CCND1, which probably render the protein insensitive to degradation, represent a previously unreported mechanism of cyclin D1 overexpression in human tumors in vivo.

The activation of the APC/beta-catenin signalling pathway due to beta-catenin mutations has been implicated in the development of a subset of endometrial carcinomas (ECs). However, up to 25% of ECs have beta-catenin nuclear accumulation without evidence of beta-catenin mutations, suggesting alterations of other molecules that can modulate the Wnt pathway, such as APC, gamma-catenin, AXIN1 and AXIN2. We investigated the expression pattern of beta- and gamma-catenin in a group of 128 endometrial carcinomas, including 95 endometrioid endometrial carcinomas (EECs) and 33 non-endometrioid endometrial carcinomas (NEECs). In addition, we evaluated the presence of loss of heterozygosity and promoter hypermethylation of the APC gene and mutations in the APC, beta- and gamma-catenin, AXIN1, AXIN2, and RAS genes, and phospho-Akt expression. No APC mutations were detected but LOH at the APC locus was found in 24.3% of informative cases. APC promoter 1A hypermethylation was observed in 46.6% of ECs, and was associated with the endometrioid phenotype (P=0.034) and microsatellite instability (P=0.008). Neither LOH nor promoter hypermethylation of APC was associated with nuclear catenin expression. Nuclear beta-catenin expression was found in 31.2% of EECs and 3% of NEECs (P=0.002), and was significantly associated with beta-catenin gene exon 3 mutations (P0.0001). beta-catenin gene exon 3 mutations were associated with the endometrioid phenotype, and were detected in 14 (14.9%) EECs, but in none of the NEECs (P=0.02). gamma-catenin nuclear expression was found in 10 ECs; it was not associated with the histological type but was associated with more advanced stages (P=0.042). No mutations in gamma-catenin, AXIN1 and 2 genes were detected in this series. Neither RAS mutations nor phospho-Akt expression, which were found in 16 and 27.6% of the cases, respectively, were associated with beta-catenin nuclear expression. Our results demonstrated a high prevalence of alterations in molecules of the APC/beta-catenin pathway, but only mutations in beta-catenin gene are associated with aberrant nuclear localization of beta-catenin.

6 páginas, 3 figuras, 2 tablas., Snail is a zinc finger transcription factor that triggers the epithelial-mesenchymal transition (EMT) by directly repressing E-cadherin expression. Snail is required for mesoderm and neural crest formation during embryonic development and has recently been implicated in the EMT associated with tumour progression. In a series of human breast carcinomas, we have analysed the expression of Snail and that of molecules of the E-cadherin/catenin complexes. We have also correlated these data with the pathological features of the tumours. We show that Snail expression inversely correlates with the grade of differentiation of the tumours and that it is expressed in all the infiltrating ductal carcinomas (IDC) presenting lymph node metastases that were analysed. In addition, Snail is expressed in some dedifferentiated tumours with a negative nodal status. Considering that Snail is involved in the induction of the invasive and migratory phenotype in epithelial cells, these results indicate that it is also involved in the progression of breast ductal tumours, where it could additionally serve as a marker of the metastatic potential., This work was supported by the Spanish Ministries of Health (FIS-01/985) and Science and Technology (DGE-SIC PM98-0125) and the Comunidad Autónoma de Madrid (CAM 08.1/0044/2000) to MA Nieto and CAM 08.1/0024.1/1999 to A Cano.

Somatostatin receptors (sst1-5) are present in different types of tumors, where they inhibit key cellular processes such as proliferation and invasion. Although ssts are densely expressed in breast cancer, especially sst2, their role and therapeutic potential remain uncertain. Recently, we identified a new truncated sst5 variant, sst5TMD4, which is related to the abnormal response of certain pituitary tumors to treatment with somatostatin analogs. Here, we investigated the possible role of sst5TMD4 in breast cancer. This study revealed that sst5TMD4 is absent in normal mammary gland, but is abundant in a subset of poorly differentiated human breast tumors, where its expression correlated to that of sst2. Moreover, in the MCF-7 breast cancer model cell, sst5TMD4 expression increased malignancy features such as invasion and proliferation abilities (both in cell cultures and nude mice). This was likely mediated by sst5TMD4-induced increase in phosphorylated extracellular signal-regulated kinases 1 and 2 and p-Akt levels, and cyclin D3 and Arp2/3 complex expression, which also led to mesenchymal-like phenotype. Interestingly, sst5TMD4 interacts physically with sst2 and thereby alters its signaling, enabling disruption of sst2 inhibitory feedback and providing a plausible basis for our findings. These results suggest that sst5TMD4 could be involved in the pathophysiology of certain types of breast tumors., This work was supported by BIO-0139, CTS-01705, CTS-5051, BFU2004-03883, BFU2007-60180/BFI, BFU2008-01136-BFI, BFU2010-19300, FPU-AP20052473, FI06-00804, SAF2007-63075, SAF2007-63075/FMM07, SAF2010-201075, CD07/00246, RYC-2007-00186 and IPSEN. Ciber is an initiative of the Instituto de Salud Carlos III.

The epithelial-to-mesenchymal transition (EMT) is a crucial process in tumour progression providing tumour cells with the ability to escape from the primary tumour, to migrate to distant regions and to invade tissues. EMT requires a loss of cell-cell adhesion and apical-basal polarity, as well as the acquisition of a fibroblastoid motile phenotype. Several transcription factors have emerged in recent years that induce EMT, with important implications for tumour progression. However, their effects on cell polarity remain unclear. Here, we have re-examined the data available related to the effect of EMT related transcription factors on epithelial cell plasticity, focusing on their impact on cell polarity. Transcriptional and post-transcriptional regulatory mechanisms mediated by several inducers of EMT, in particular the ZEB and Snail factors, downregulate the expression and/or functional organization of core polarity complexes. We also summarize data on the expression of cell polarity genes in human tumours and analyse genetic interactions that highlight the existence of complex regulatory networks converging on the regulation of cell polarity by EMT inducers in human breast carcinomas. These recent observations provide new insights into the relationship between alterations in cell polarity components and EMT in cancer, opening new avenues for their potential use as therapeutic targets to prevent tumour progression. © 2008 Macmillan Publishers Limited All rights reserved., Our work is supported by grants from the Spanish Ministry of Education and Science (SAF2007-63051, NAN2004-09230-C04 and CONSOLIDER-INGENIO 2010 CSD2007-00017 to AC, and SAF2007-63075 to GMB), the EU (MRTN-CT-2004- 005428) to AC and from the Fundación Mutua Madrileña (2006) to GMB.GMB is a junior researcher contracted on the Ramon y Cajal program, 2004.

It has been recently shown that cannabinoids, the active components of marijuana and their derivatives, inhibit cell cycle progression of human breast cancer cells. Here we studied the mechanism of Delta(9)-tetrahydrocannabinol (THC) antiproliferative action in these cells, and show that it involves the modulation of JunD, a member of the AP-1 transcription factor family. THC activates JunD both by upregulating gene expression and by translocating the protein to the nuclear compartment, and these events are accompanied by a decrease in cell proliferation. Of interest, neither JunD activation nor proliferation inhibition was observed in human non-tumour mammary epithelial cells exposed to THC. We confirmed the importance of JunD in THC action by RNA interference and genetic ablation. Thus, in both JunD-silenced human breast cancer cells and JunD knockout mice-derived immortalized fibroblasts, the antiproliferative effect exerted by THC was significantly diminished. Gene array and siRNA experiments support that the cyclin-dependent kinase inhibitor p27 and the tumour suppressor gene testin are candidate JunD targets in cannabinoid action. In addition, our data suggest that the stress-regulated protein p8 participates in THC antiproliferative action in a JunD-independent manner. In summary, this is the first report showing not only that cannabinoids regulate JunD but, more generally, that JunD activation reduces the proliferation of cancer cells, which points to a new target to inhibit breast cancer progression.

Snai1 (Snail) and Snai2 (Slug), the two main members of Snail family factors, are important mediators of epithelial-mesenchymal transitions and involved in tumor progression. We recently reported that Snai1 plays a major role in tumor growth, invasion and metastasis, but the contribution of Snai2 to tumorigenesis is not yet well understood. To approach this question we have silenced Snai2 and/or Snai1 by stable RNA interference in two independent mouse skin carcinoma (HaCa4 and CarB) cell lines. We demonstrate that Snai2 knockdown has a milder effect, but collaborates with Snai1 silencing in reduction of tumor growth potential of either carcinoma cell line when injected into nude mice. Importantly, Snai1 or Snai2 silencing dramatically influences the metastatic ability of squamous carcinoma HaCa4 cells, inducing a strong reduction in liver and lung distant metastasis. However, only Snai1 knockdown has an effective action on invasiveness and fully abolishes tumor cell dissemination into the spleen. These results demonstrate that Snai1 and Snai2 collaborate on primary tumor growth and specifically contribute to site-specific metastasis of HaCa4 cells. These data also indicate that Snai1 is the major regulator of local invasion, supporting a hierarchical participation of both factors in the metastatic process. © 2008 Macmillan Publishers Limited All rights reserved., This work was supported by grants from the Spanish Ministry of Education and Science (SAF2004-00361; SAF2007-63051; NAN2004-09230-C04-02; Consolider-Ingenio CSD00C-2007-26102) and the EU (MRTN-CT-2004-005428).

Among microtubule-targeting agents, docetaxel has received recent interest owing to its good therapeutic index. Clinical trials have underlined its potential for the treatment of advanced breast cancer, although little is known about its molecular mode of action in this context. We characterized the molecular changes induced by docetaxel in two well-known human breast carcinoma cell lines. Two mechanisms of action according to drug concentration were suggested by a biphasic sensitivity curve, and were further validated by cell morphology, cell cycle and cell death changes. Two to four nanomolar docetaxel induced aberrant mitosis followed by late necrosis, and 100 nM docetaxel induced mitotic arrest followed by apoptosis. Passing through mitosis phase was a requirement for hypodiploidy to occur, as shown by functional studies in synchronized cells and by combining docetaxel with the proteasome inhibitor MG132. Transcriptional profiling showed differences according to cell line and docetaxel concentration, with cell cycle, cell death and structural genes commonly regulated in both cell lines. Although p53 targets were mainly induced with low concentration of drug in MCF7 cells, its relevance in the dual mechanism of docetaxel cytotoxicity was ruled out by using an isogenic shp53 cell line. Many of the genes shown in this study may contribute to the dual mechanism by which docetaxel inhibits the growth of breast cancer cells at different concentrations. These findings provide a basis for rationally enhancing docetaxel therapy, considering lower concentrations, and better drug combinations. © 2007 Nature Publishing Group All rights reserved., This work was supported by Ministerio de Educación y Ciencia, Grant Reference PTR1995-0753-OP and Ministerio de Ciencia y Tecnología SAF2001-0065 and SAF2004-08258-C02-01. GMB is junior investigator of the Ramón y Cajal Program 2004.