Eduardo Pérez-Gómez

Lysyl Oxidase-Like 2 as a New Poor Prognosis Marker of Squamous Cell Carcinomas

Lysyl oxidase-like 2 (Loxl2) interacts with and stabilizes Snai1 transcription factor, promoting epithelial-mesenchymal transition. Either Loxl2 or Snai1 knock-down blocks tumor growth and induces differentiation, but the specific role of each factor in tumor progression is still unknown. Comparison of the gene expression profiles of the squamous cell carcinoma cell line HaCa4 after knocking-down Loxl2 or Snai1 revealed that a subset of epidermal differentiation genes was specifically up-regulated in Loxl2-silenced cells. In agreement, although both Loxl2- and Snai1-knockdown cells showed reduced in vivo invasion, only Loxl2-silenced cells exhibited a skin-like epidermal differentiation program. In addition, we show that expression of Loxl2 and Snai1 correlates with malignant progression in a two-stage mouse skin carcinogenesis model. Furthermore, we found that increased expression of both LOXL2 and SNAI1 correlates with local recurrence in a cohort of 256 human laryngeal squamous cell carcinomas. We describe for the first time that high levels of LOXL2 are associated with decreased overall and disease-free survival in laryngeal squamous cell carcinomas, lung squamous cell carcinoma, and lymph node-negative (N(0)) breast adenocarcinomas. Altogether, our results show that LOXL2 can be used as a new poor prognosis indicator in human squamous cell carcinomas promoting malignant transformation by both SNAI1-dependent and SNAI1-independent pathways.

The orphan G protein-coupled receptor GPR55 promotes cancer cell proliferation via ERK

GPR55 is an orphan G protein-coupled receptor that may be engaged by some lipid ligands such as lysophosphatidylinositol and cannabinoid-type compounds. Very little is known about its expression pattern and physio-pathological relevance, and its pharmacology and signaling are still rather controversial. Here we analyzed the expression and function of GPR55 in cancer cells. Our data show that GPR55 expression in human tumors from different origins correlates with their aggressiveness. Moreover, GPR55 promotes cancer cell proliferation, both in cell cultures and in xenografted mice, through the overactivation of the extracellular signal-regulated kinase cascade. These findings reveal the importance of GPR55 in human cancer, and suggest that it could constitute a new biomarker and therapeutic target in oncology.

Cannabinoids reduce ErbB2-driven breast cancer progression through Akt inhibition

BackgroundErbB2-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.ResultsOur results show that both Δ9-tetrahydrocannabinol, the most abundant and potent cannabinoid in marijuana, and JWH-133, a non-psychotropic CB2 receptor-selective agonist, reduce tumor growth, tumor number, and the amount/severity of lung metastases in MMTV-neu mice. Histological analyses of the tumors revealed that cannabinoids inhibit cancer cell proliferation, induce cancer cell apoptosis, and impair tumor angiogenesis. Cannabinoid antitumoral action relies, at least partially, on the inhibition of the pro-tumorigenic Akt pathway. We also found that 91% of ErbB2-positive tumors express the non-psychotropic cannabinoid receptor CB2.ConclusionsTaken together, these results provide a strong preclinical evidence for the use of cannabinoid-based therapies for the management of ErbB2-positive breast cancer.

Characterization of murine S-endoglin isoform and its effects on tumor development

Endoglin is a transmembrane glycoprotein that acts as an auxiliary receptor for transforming growth factor-β (TGF-β) and modulates cellular responses to this pleiotropic cytokine. Endoglin is strongly expressed in endothelial cells, where it appears to exert a crucial role in vascular development and angiogenesis. Two endoglin isoforms (L and S), differing in their cytoplasmic domains, have been previously characterized in human tissues. We now demonstrate the existence of similar L- and S-endoglin variants in murine tissues with 47 and 35 amino acids, respectively, in their cytoplasmic tail. RT–PCR analysis showed that L is the predominant endoglin isoform expressed in mouse tissues, although S-endoglin mRNA is significantly expressed in liver and lung, as well as in endothelial cell lines. Furthermore, a protein of size equivalent to recombinant S-endoglin expressed in mammalian cells was detected in mouse endothelial cells by Western blot analysis. L- and S-endoglin isoforms can form disulfide-linked heterodimers, as demonstrated by cotransfection of L- and S-endoglin constructs. To address the role of S-endoglin in vivo, an S-Eng+ transgenic mouse model that targets S-endoglin expression to the endothelium was generated. The lethal phenotype of endoglin-null (Eng−/−) mice was not rescued by breeding S-Eng+ transgenic mice into the endoglin-null background. S-Eng+ mice exhibited reduced tumor growth and neovascularization after transplantation of Lewis lung carcinoma cells. In addition, S-Eng+ mice showed a drastic inhibition of benign papilloma formation when subjected to two-stage chemical skin carcinogenesis. These results point to S-endoglin as an antiangiogenic molecule, in contrast to L-endoglin which is proangiogenic.

The role of the TGF-β coreceptor endoglin in cancer

Endoglin (CD105) is an auxiliary membrane receptor of transforming growth factor beta (TGF-β) that interacts with type I and type II TGF-β receptors and modulates TGF-β signaling. Endoglin is overexpressed in the tumor-associated vascular endothelium, where it modulates angiogenesis. This feature makes endoglin a promising target for antiangiogenic cancer therapy. In addition, recent studies on human and experimental models of carcinogenesis point to an important tumor cell–autonomous role of endoglin by regulating proliferation, migration, invasion, and metastasis. These studies suggest that endoglin behaves as a suppressor of malignancy in experimental and human epithelial carcinogenesis, although it can also promote metastasis in other types of cancer. In this review, we evaluate the implication of endoglin in tumor development underlying studies developed in our laboratories in recent years.

S-Endoglin Expression Is Induced in Senescent Endothelial Cells and Contributes to Vascular Pathology

Senescence of endothelial cells (ECs) may contribute to age-associated cardiovascular diseases, including atherosclerosis and hypertension. The functional and gene expression changes associated with cellular senescence are poorly understood. Here, we have analyzed the expression, during EC senescence, of 2 different isoforms (L, long; S, short) of endoglin, an auxiliary transforming growth factor (TGF)-&bgr; receptor involved in vascular remodeling and angiogenesis. As evidenced by RT-PCR, the S/L ratio of endoglin isoforms was increased during senescence of human ECs in vitro, as well as during aging of mice in vascularized tissues. Next, the effect of S-endoglin protein on the TGF-&bgr; receptor complex was studied. As revealed by coimmunoprecipitation assays, S-endoglin was able to interact with both TGF-&bgr; type I receptors, ALK5 and ALK1, although the interaction with ALK5 was stronger than with ALK1. S-endoglin conferred a lower proliferation rate to ECs and behaved differently from L-endoglin in relation to TGF-&bgr;–responsive reporters with ALK1 or ALK5 specificities, mimicking the behavior of the endothelial senescence markers Id1 and plasminogen activator inhibitor-1. In situ hybridization studies demonstrated the expression of S-endoglin in the endothelium from human arteries. Transgenic mice overexpressing S-endoglin in ECs showed hypertension, decreased hypertensive response to NO inhibition, decreased vasodilatory response to TGF-&bgr;1 administration, and decreased endothelial nitric oxide synthase expression in lungs and kidneys, supporting the involvement of S-endoglin in the NO-dependent vascular homeostasis. Taken together, these results suggest that S-endoglin is induced during endothelial senescence and may contribute to age-dependent vascular pathology.

The orphan receptor GPR55 drives skin carcinogenesis and is upregulated in human squamous cell carcinomas

G protein-coupled receptors (GPCRs) control crucial physiological processes and their dysfunction contributes to various human diseases, including cancer. The orphan GPCR GPR55 was identified and cloned more than a decade ago, but very little is known about its physio-pathological relevance. It has been recently shown that GPR55 controls the behavior of human cancer cell lines in culture and xenografts. However, the assessment of the actual role of this receptor in malignant transformation in vivo is hampered by the lack of studies on its functional impact in clinically-relevant models of cancer. Here we demonstrate that GPR55 drives mouse skin tumor development. Thus, GPR55-deficient mice were more resistant to DMBA/TPA-induced papilloma and carcinoma formation than their wild-type littermates. GPR55 exerted this pro-tumor effect primarily by conferring a proliferative advantage on cancer cells. In addition, GPR55 enhanced skin cancer cell anchorage-independent growth, invasiveness and tumorigenicity in vivo, suggesting that it promotes not only tumor development but also tumor aggressiveness. Finally, we observed that GPR55 is upregulated in human skin tumors and other human squamous cell carcinomas compared with the corresponding healthy tissues. Altogether, these findings reveal the pivotal importance of GPR55 in skin tumor development, and suggest that this receptor may be used as a new biomarker and therapeutic target in squamous cell carcinomas.

Cannabinoids: a new hope for breast cancer therapy?

Breast cancer is a very common disease that affects approximately 1 in 10 women at some point in their lives. Importantly, breast cancer cannot be considered a single disease as it is characterized by distinct pathological and molecular subtypes that are treated with different therapies and have diverse clinical outcomes. Although some highly successful treatments have been developed, certain breast tumors are resistant to conventional therapies and a considerable number of them relapse. Therefore, new strategies are urgently needed, and the challenge for the future will most likely be the development of individualized therapies that specifically target each patients tumor. Experimental evidence accumulated during the last decade supports that cannabinoids, the active components of Cannabis sativa and their derivatives, possess anticancer activity. Thus, these compounds exert anti-proliferative, pro-apoptotic, anti-migratory and anti-invasive actions in a wide spectrum of cancer cells in culture. Moreover, tumor growth, angiogenesis and metastasis are hampered by cannabinoids in xenograft-based and genetically-engineered mouse models of cancer. This review summarizes our current knowledge on the anti-tumor potential of cannabinoids in breast cancer, which suggests that cannabinoid-based medicines may be useful for the treatment of most breast tumor subtypes.

Expression of the TGF- β coreceptor endoglin in epidermal keratinocytes and its dual role in multistage mouse skin carcinogenesis

Endoglin is an integral membrane glycoprotein primarily expressed in the vascular endothelium, but also found on macrophages and stromal cells. It binds several members of the transforming growth factor (TGF)-β family of growth factors and modulates TGF-β1-dependent cellular responses. However, it lacks cytoplasmic signaling motifs and is considered as an auxiliary receptor for TGF-β. We show here that endoglin is expressed in mouse and human epidermis and in skin appendages, such as hair follicles and sweat glands, as determined by immunohistochemistry. In normal interfollicular epidermis, endoglin was restricted to basal keratinocytes and absent in differentiating cells of suprabasal layers. Follicular expression of endoglin was high in hair bulb keratinocytes, but decreased in parts distal from the bulb. To address the role of endoglin in skin carcinogenesis in vivo, Endoglin heterozygous mice were subjected to long-term chemical carcinogenesis treatment. Reduction in endoglin had a dual effect during multistage carcinogenesis, by inhibiting the early appearance of benign papillomas, but increasing malignant progression to highly undifferentiated carcinomas. Our results are strikingly similar to those previously reported for transgenic mice overexpressing TGF-β1 in the epidermis. These data suggest that endoglin might attenuate TGF-β1 signaling in normal epidermis and interfere with progression of skin carcinogenesis.

A Role for Endoglin as a Suppressor of Malignancy during Mouse Skin Carcinogenesis

Endoglin is a membrane glycoprotein that acts as a coreceptor for transforming growth factor-beta. We and others have previously suggested a function of endoglin as a tumor suppressor in epithelial cancer. Here, we study the expression of endoglin during chemical mouse skin carcinogenesis. We find that shedding of membrane endoglin, allowing the secretion of a soluble endoglin form, is a late event associated with progression from squamous to spindle cell carcinomas. Knockdown of endoglin in transformed keratinocytes activates the Smad2/3 signaling pathway resulting in cell growth arrest, delayed tumor latencies, and a squamous to spindle phenotypic conversion. Forced expression of the long endoglin isoform in spindle carcinoma cells blocks transforming growth factor-beta1 stimulation of Smad2/3 signaling and prevents tumor formation. In contrast, expression of the short endoglin isoform has no effect on spindle cell growth in vitro or in vivo. Our results show that endoglin behaves as a suppressor of malignancy during the late stages of carcinogenesis. Therefore, disruption of membrane endoglin emerges as a crucial event for progression to spindle cell carcinomas.