title: BRCA1 haploinsufficiency cell-autonomously activates RANKL expression and generates denosumab-responsive breast cancer-initiating cells.
abstract: Denosumab, a monoclonal antibody to the receptor activator of nuclear factor-κB ligand (RANKL), might be a novel preventative therapy for BRCA1-mutation carriers at high risk of developing breast cancer. Beyond its well-recognized bone-targeted activity impeding osteoclastogenesis, denosumab has been proposed to interfere with the cross-talk between RANKL-producing sensor cells and cancer-initiating RANK+ responder cells that reside within premalignant tissues of BRCA1-mutation carriers. We herein tested the alternative but not mutually exclusive hypothesis that BRCA1 deficiency might cell-autonomously activate RANKL expression to generate cellular states with cancer stem cell (CSC)-like properties. Using isogenic pairs of normal-like human breast epithelial cells in which the inactivation of a single BRCA1 allele results in genomic instability, we assessed the impact of BRCA1 haploinsufficiency on the expression status of RANK and RANKL. RANK expression remained unaltered but RANKL was dramatically up-regulated in BRCA1mut/+ haploinsufficient cells relative to isogenic BRCA1+/+ parental cells. Neutralizing RANKL with denosumab significantly abrogated the ability of BRCA1 haploinsufficient cells to survive and proliferate as floating microtumors or "mammospheres" under non-adherent/non-differentiating conditions, an accepted surrogate of the relative proportion and survival of CSCs. Intriguingly, CSC-like states driven by epithelial-to-mesenchymal transition or HER2 overexpression traits responded to some extent to denosumab. We propose that breast epithelium-specific mono-allelic inactivation of BRCA1 might suffice to cell-autonomously generate RANKL-addicted, denosumab-responsive CSC-like states. The convergent addiction to a hyperactive RANKL/RANK axis of CSC-like states from genetically diverse breast cancer subtypes might inaugurate a new era of cancer prevention and treatment based on denosumab as a CSC-targeted agent.
authors.affiliation: Program Against Cancer Therapeutic Resistance (ProCURE), Metabolism and Cancer Group, Catalan Institute of Oncology, Girona, Catalonia, Spain.|Molecular Oncology Group, Girona Biomedical Research Institute (IDIBGI), Girona, Spain.
authors.forename: Elisabet
authors.initials: E
authors.lastname: Cuyàs
authors.affiliation: Program Against Cancer Therapeutic Resistance (ProCURE), Metabolism and Cancer Group, Catalan Institute of Oncology, Girona, Catalonia, Spain.|Molecular Oncology Group, Girona Biomedical Research Institute (IDIBGI), Girona, Spain.
authors.forename: Bruna
authors.initials: B
authors.lastname: Corominas-Faja
authors.affiliation: Neuroimmunology and Multiple Sclerosis Unit, Dr. Josep Trueta University Hospital, Girona Biomedical Research Institute (IDIBGI), Girona, Spain.
authors.forename: María Muñoz-San
authors.initials: MM
authors.lastname: Martín
authors.affiliation: Molecular Oncology Group, Girona Biomedical Research Institute (IDIBGI), Girona, Spain.|Unit of Clinical Research, Catalan Institute of Oncology, Girona, Catalonia, Spain.
authors.forename: Begoña
authors.initials: B
authors.lastname: Martin-Castillo
authors.affiliation: Mayo Clinic, Department of Laboratory Medicine and Pathology, Division of Experimental Pathology, Rochester, MN, USA.|Mayo Clinic Cancer Center, Rochester, MN, USA.
authors.forename: Ruth
authors.initials: R
authors.lastname: Lupu
authors.affiliation: Deparment of Medical Oncology, Catalan Institute of Oncology, Girona, Catalonia, Spain.|Department of Medical Sciences, Medical School, University of Girona, Girona, Spain.
authors.forename: Joan
authors.initials: J
authors.lastname: Brunet
authors.affiliation: Deparment of Medical Oncology, Catalan Institute of Oncology, Girona, Catalonia, Spain.|Department of Medical Sciences, Medical School, University of Girona, Girona, Spain.
authors.forename: Joaquim
authors.initials: J
authors.lastname: Bosch-Barrera
authors.affiliation: Program Against Cancer Therapeutic Resistance (ProCURE), Metabolism and Cancer Group, Catalan Institute of Oncology, Girona, Catalonia, Spain.|Molecular Oncology Group, Girona Biomedical Research Institute (IDIBGI), Girona, Spain.
authors.forename: Javier A
authors.initials: JA
authors.lastname: Menendez
mesh_terms: D019313:BRCA1 Protein / Q000235:genetics*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D000069448:Denosumab / Q000494:pharmacology*; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D057895:Haploinsufficiency; D006801:Humans; D061986:MCF-7 Cells; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000378:metabolism*; D053245:RANK Ligand / Q000378:metabolism*; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D019313:BRCA1 Protein; C492913:BRCA1 protein, human; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; C505686:TNFRSF11A protein, human; C505688:TNFSF11 protein, human; D000069448:Denosumab
keywords: BRCA1; RANK; RANKL; cancer stem cells; denosumab