title: Autophagy Protects from Trastuzumab-Induced Cytotoxicity in HER2 Overexpressing Breast Tumor Spheroids.
abstract: Multicellular tumor spheroids represent a 3D in vitro model that mimics solid tumor essential properties including assembly and development of extracellular matrix and nutrient, oxygen and proliferation gradients. In the present study, we analyze the impact of 3D spatial organization of HER2-overexpressing breast cancer cells on the response to Trastuzumab. We cultured human mammary adenocarcinoma cell lines as spheroids with the hanging drop method and we observed a gradient of proliferating, quiescent, hypoxic, apoptotic and autophagic cells towards the inner core. This 3D organization decreased Trastuzumab sensitivity of HER2 over-expressing cells compared to monolayer cell cultures. We did not observe apoptosis induced by Trastuzumab but found cell arrest in G0/G1 phase. Moreover, the treatment downregulated the basal apoptosis only found in tumor spheroids, by eliciting protective autophagy. We were able to increase sensitivity to Trastuzumab by autophagy inhibition, thus exposing the interaction between apoptosis and autophagy. We confirmed this result by developing a resistant cell line that was more sensitive to autophagy inhibition than the parental BT474 cells. In summary, the development of Trastuzumab resistance relies on the balance between death and survival mechanisms, characteristic of 3D cell organization. We propose the use of spheroids to further improve the understanding of Trastuzumab antitumor activity and overcome resistance.
authors.affiliation: Research Area, Institute of Oncology 'Ángel H. Roffo', University of Buenos Aires, Buenos Aires, Argentina.
authors.forename: Cristina E
authors.initials: CE
authors.lastname: Rodríguez
authors.affiliation: Industrial Biotechnology Research and Development Center, National Institute of Industrial Technology, Buenos Aires, Argentina.
authors.forename: Sara I
authors.initials: SI
authors.lastname: Reidel
authors.affiliation: Research Area, Institute of Oncology 'Ángel H. Roffo', University of Buenos Aires, Buenos Aires, Argentina.
authors.forename: Elisa D
authors.initials: ED
authors.lastname: Bal de Kier Joffé
authors.affiliation: Research Area, Institute of Oncology 'Ángel H. Roffo', University of Buenos Aires, Buenos Aires, Argentina.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Jasnis
authors.affiliation: Research Area, Institute of Oncology 'Ángel H. Roffo', University of Buenos Aires, Buenos Aires, Argentina; Industrial Biotechnology Research and Development Center, National Institute of Industrial Technology, Buenos Aires, Argentina.
authors.forename: Gabriel L
authors.initials: GL
authors.lastname: Fiszman
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000633:toxicity; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D001343:Autophagy / Q000187:drug effects* / Q000235:genetics; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism*; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D005260:Female; D015870:Gene Expression; D006801:Humans; D010641:Phenotype; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D018874:Spheroids, Cellular; D000068878:Trastuzumab / Q000494:pharmacology* / Q000633:toxicity; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab