Pharmacological activation of cannabinoid receptors elicits antitumoral responses in different cancer models. However, the biological role of these receptors in tumor physio-pathology is still unknown. We analyzed CB₂ cannabinoid receptor protein expression in two series of 166 and 483 breast tumor samples operated in the University Hospitals of Kiel, Tübingen, and Freiburg between 1997 and 2010 and CB₂ mRNA expression in previously published DNA microarray datasets. The role of CB₂ in oncogenesis was studied by generating a mouse line that expresses the human V-Erb-B2 Avian Erythroblastic Leukemia Viral Oncogene Homolog 2 (HER2) rat ortholog (neu) and lacks CB₂ and by a variety of biochemical and cell biology approaches in human breast cancer cells in culture and in vivo, upon modulation of CB₂ expression by si/shRNAs and overexpression plasmids. CB₂-HER2 molecular interaction was studied by colocalization, coimmunoprecipitation, and proximity ligation assays. Statistical tests were two-sided. We show an association between elevated CB₂ expression in HER2+ breast tumors and poor patient prognosis (decreased overall survival, hazard ratio [HR] = 0.29, 95% confidence interval [CI] = 0.09 to 0.71, P = .009) and higher probability to suffer local recurrence (HR = 0.09, 95% CI = 0.049 to 0.54, P = .003) and to develop distant metastases (HR = 0.33, 95% CI = 0.13 to 0.75, P = .009). We also demonstrate that genetic inactivation of CB₂ impairs tumor generation and progression in MMTV-neu mice. Moreover, we show that HER2 upregulates CB₂ expression by activating the transcription factor ELK1 via the ERK cascade and that an increased CB₂ expression activates the HER2 pro-oncogenic signaling at the level of the tyrosine kinase c-SRC. Finally, we show HER2 and CB₂ form heteromers in cancer cells. Our findings reveal an unprecedented role of CB₂ as a pivotal regulator of HER2 pro-oncogenic signaling in breast cancer, and they suggest that CB₂ may be a biomarker with prognostic value in these tumors.

Introduction: The Fas/FasL system plays a significant role in tumorigenesis. Research has shown that its impairment in cancer cells may lead to apoptosis resistance and contribute to tumor progress...

FADD was initially described as an adaptor molecule for death receptor-mediated apoptosis, but subsequently it has been implicated in nonapoptotic cellular processes such as proliferation and cell cycle control. During the last decade, FADD has been shown to play a pivotal role in most of the signalosome complexes, such as the necroptosome and the inflammasome. Interestingly, various mechanisms involved in regulating FADD functions have been identified, essentially posttranslational modifications and secretion. All these aspects have been thoroughly addressed in previous reviews. However, FADD implication in cancer is complex, due to pleiotropic effects. It has been reported either as anti- or protumorigenic, depending on the cell type. Regulation of FADD expression in cancer is a complex issue since both overexpression and downregulation have been reported, but the mechanisms underlying such alterations have not been fully unveiled. Posttranslational modifications also constitute a relevant mechanism controlling FADD levels and functions in tumor cells. In this review, we aim to provide detailed, updated information on alterations leading to changes in FADD expression and function in cancer. The participation of FADD in various biological processes is recapitulated, with a mention of interesting novel functions recently proposed for FADD, such as regulation of gene expression and control of metabolic pathways. Finally, we gather all the available evidence regarding the clinical implications of FADD alterations in cancer, especially as it has been proposed as a potential biomarker with prognostic value.

Fusions transcripts have been proven to be strong drivers for neoplasia-associated mutations, although their incidence in T-cell lymphoblastic lymphoma needs to be determined yet. Using RNA-Seq we have selected 55 fusion transcripts identified by at least two of three detection methods in the same tumour. We confirmed the existence of 24 predicted novel fusions that had not been described in cancer or normal tissues yet, indicating the accuracy of the prediction. Of note, one of them involves the proto oncogene TAL1. Other confirmed fusions could explain the overexpression of driver genes such as COMMD3-BMI1, LMO1 or JAK3. Five fusions found exclusively in tumour samples could be considered pathogenic (NFYG-TAL1, RIC3-TCRBC2, SLC35A3-HIAT1, PICALM MLLT10 and MLLT10-PICALM). However, other fusions detected simultaneously in normal and tumour samples (JAK3-INSL3, KANSL1-ARL17A/B and TFG-ADGRG7) could be germ-line fusions genes involved in tumour-maintaining tasks. Notably, some fusions were confirmed in more tumour samples than predicted, indicating that the detection methods underestimated the real number of existing fusions. Our results highlight the potential of RNA-Seq to identify new cryptic fusions, which could be drivers or tumour-maintaining passenger genes. Such novel findings shed light on the searching for new T-LBL biomarkers in these haematological disorders.

Cryptic deletions at chromosome 6q are common cytogenetic abnormalities in T-cell lymphoblastic leukemia/lymphoma (T-LBL), but the target genes have not been formally identified. Our results build on detection of specific chromosomal losses in a mouse model of γ-radiation-induced T-LBLs and provide interesting clues for new putative susceptibility genes in a region orthologous to human 6q15–6q16.3. Among these, Epha7 emerges as a bona fide candidate tumor suppressor gene because it is inactivated in practically all the T-LBLs analyzed (100% in mouse and 95.23% in human). We provide evidence showing that Epha7 downregulation may occur, at least in part, by loss of heterozygosity (19.35% in mouse and 12.5% in human) or promoter hypermethylation (51.61% in mouse and 43.75% in human) or a combination of both mechanisms (12.90% in mouse and 6.25% in human). These results indicate that EPHA7 might be considered a new tumor suppressor gene for 6q deletions in T-LBLs. Notably, this gene is located in 6q16.1 proximal to GRIK2 and CASP8AP2 , other candidate genes identified in this region. Thus, del6q seems to be a complex region where inactivation of multiple genes may cooperatively contribute to the onset of T-cell lymphomas.

Endoglin is a membrane glycoprotein that acts as a coreceptor for transforming growth factor-β. 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-β1 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. [Cancer Res 2007;67(21):10268–77]