title: The Autophagic Process Occurs in Human Bone Metastasis and Implicates Molecular Mechanisms Differently Affected by Rab5a in the Early and Late Stages.
abstract: Autophagy favours metastatic growth through fuelling energy and nutrients and resistance to anoikis, typical of disseminated-tumour cells. The autophagic process, mediated by a unique organelle, the autophagosome, which fuses with lysosomes, is divided into three steps. Several stages, especially early omegasome formation and isolation-membrane initiation, remain controversial; molecular mechanisms involve the small-GTPase Rab5a, which regulates vesicle traffic for autophagosome formation. We examined Rab5a involvement in the function of key members of ubiquitin-conjugation systems, Atg7 and LC3-lipidated, interacting with the scaffold-protein p62. Immunohistochemistry of Rab5a was performed in human specimens of bone metastasis and pair-matched breast carcinoma; the autophagic-molecular mechanisms affected by Rab5a were evaluated in human 1833 bone metastatic cells, derived from breast-carcinoma MDA-MB231 cells. To clarify the role of Rab5a, 1833 cells were transfected transiently with Rab5a-dominant negative, and/or stably with the short-hairpin RNA Atg7, were exposed to two inhibitors of autolysosome function, and LC3II and p62 expression was measured. We showed basal autophagy in bone-metastatic cells and the pivotal role of Rab5a together with Beclin 1 between the early stages, elongation of isolation membrane/closed autophagosome mediated by Atg7, and the late-degradative stages. This regulatory network might occur in bone-metastasis and in high-grade dysplastic lesions, preceding invasive-breast carcinoma and conferring phenotypic characteristics for dissemination.
authors.affiliation: Istituto Ortopedico Galeazzi, Scientific Institute for Research, Hospitalization and Health Care (IRCCS), Milano 20161, Italy. paola.maroni@grupposandonato.it.
authors.forename: Paola
authors.initials: P
authors.lastname: Maroni
authors.affiliation: Dipartimento di Scienze Biomediche per la Salute, Molecular Pathology Laboratory, Università degli Studi di Milano, Milano 20133, Italy. paola.bendinelli@unimi.it.
authors.forename: Paola
authors.initials: P
authors.lastname: Bendinelli
authors.affiliation: San Raffaele Scientific Institute, Division of Genetics and Cell Biology, Milano 20133, Italy. resnati.massimo@hsr.it.
authors.forename: Massimo
authors.initials: M
authors.lastname: Resnati
authors.affiliation: Dipartimento di Scienze Biomediche per la Salute, Molecular Pathology Laboratory, Università degli Studi di Milano, Milano 20133, Italy. emanuela.matteucci@unimi.it.
authors.forename: Emanuela
authors.initials: E
authors.lastname: Matteucci
authors.affiliation: San Raffaele Scientific Institute, Division of Genetics and Cell Biology, Milano 20133, Italy. milan.enrico@hsr.it.
authors.forename: Enrico
authors.initials: E
authors.lastname: Milan
authors.affiliation: Dipartimento di Scienze Biomediche per la Salute, Molecular Pathology Laboratory, Università degli Studi di Milano, Milano 20133, Italy. a.desiderio@unimi.it.
authors.forename: Maria Alfonsina
authors.initials: MA
authors.lastname: Desiderio
mesh_terms: D001343:Autophagy; D000071193:Autophagy-Related Protein 7 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D000071186:Beclin-1 / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D001859:Bone Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000556:secondary; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009367:Neoplasm Staging; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism; D020696:rab5 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C491997:BECN1 protein, human; D000071186:Beclin-1; C477012:MAP1LC3A protein, human; D008869:Microtubule-Associated Proteins; C118585:P62 protein, human; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; C427755:RAB5C protein, human; D020696:rab5 GTP-Binding Proteins; C509349:ATG7 protein, human; D000071193:Autophagy-Related Protein 7
keywords: Rab5a; autophagy; bone metastasis