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: Dept. Biochemistry and Molecular Biology I, School of Biology, Complutense University, Madrid, Spain (EPG, CA, MMC, SBB, EGT, MG, CS); Instituto de Investigación Hospital 12 de Octubre, Madrid, Spain (EPG, CA, SBB, CS); Biodonostia, San Sebastian, Spain and IKERBASQUE, Basque Foundation for Science, Bilbao, Spain (MMC); Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain (MVM, JFP); Centro de Investigación Biomédica en Red de Enfermedades Raras, Madrid, Spain (MVM, JFP); Instituto de Investigación Sanitaria Fundación Jiménez Díaz, Madrid, Spain (MVM, JFP); Department of Biochemistry and Molecular Biology, University of Barcelona, Barcelona, Spain (EM, EIC, PJM); Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas, Madrid, Spain (EM, EIC, PJM, MG); Institute of Biomedicine of the University of Barcelona, Barcelona, Spain (EM, EIC, PJM); Department of Gynecology and Obstetrics, University Hospital Schleswig-Holstein, Kiel, Germany (SH, AW, IA, MB, NA); Department of Animal Surgery and Medicine, School of Veterinary, Complutense University, Madrid, Spain (JMF); Instituto de Investigaciones Biomédicas Alberto Sols, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain (EMV, GMB, MQ); Institute of Pathology, University Hospital Schleswig-Holstein, Kiel, Germany (WK, CR); Institute of Pathology, University of Freiburg, Freiburg, Germany (PB); Department of Gynecology and Obstetrics, University of Freiburg, Freiburg, Germany (ES); Institute of Pathology and Neuropathology, University Hospital of Tübingen, Tübingen, Germany (AS); Spanish National Cancer Research Centre (CNIO), Madrid, Spain (JS, MPM, DM); Fundación MD Anderson Internacional, Madrid, Spain (GMB); Department of Organic Chemistry, School of Chemistry, Complutense University, Madrid, Spain (SOG, MA, HVV); School of Pharmacy, University of East A
Published: June 2015
AI Article Synopsis
Article Abstract
Background: 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.
Methods: 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.
Results: 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.
Conclusions: 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.
