title: Suppression of oncogenic properties of c-Myc by LKB1-controlled epithelial organization.
abstract: Cellular organization into epithelial architecture maintains structural integrity and homeostasis by suppressing cell proliferation and apoptosis. However, it is unclear whether the epithelial organization is sufficient to block induction of cell-autonomous cell cycle progression and apoptotic sensitivity by activated oncogenes. We show that chronic activation of oncogenic c-Myc, starting in the developing 3D organotypic mammary acinar structures, results in hyperproliferation and transformed acinar morphology. Surprisingly, acute c-Myc activation in mature quiescent acini with established epithelial architecture fails to reinitiate the cell cycle or transform these structures. c-Myc does reinitiate the cell cycle in quiescent, but structurally unorganized, acini, which demonstrates that proper epithelial architecture is needed for the proliferation blockade. The capability of c-Myc to reinitiate the cell cycle in acinar structures is also restored by the loss of LKB1, a human homologue of the cell polarity protein PAR4. The epithelial architecture also restrains the apoptotic activity of c-Myc, but coactivation of c-Myc and a complementary TNF-related apoptosis-inducing ligand death receptor pathway can induce a strong Bim and Bid-mediated apoptotic response in the established acini. The results together expose surprising proliferation and apoptosis resistance of organized epithelial structures and identify a role for the polarity regulator LKB1 in the development of c-Myc-resistant cell organization.
authors.affiliation: Cancer Cell Circuitry Laboratory, Institute of Biomedicine/Biochemistry and Genome-Scale Biology Program, Biomedicum Helsinki, University of Helsinki, Room B231a, PO Box 63, Haartmaninkatu 8, 00014, Helsinki, Finland.
authors.forename: Johanna I
authors.initials: JI
authors.lastname: Partanen
authors.forename: Anni I
authors.initials: AI
authors.lastname: Nieminen
authors.forename: Tomi P
authors.initials: TP
authors.lastname: Mäkelä
authors.forename: Juha
authors.initials: J
authors.lastname: Klefstrom
mesh_terms: D000091162:AMP-Activated Protein Kinase Kinases; D017209:Apoptosis / Q000235:genetics / Q000502:physiology; D001943:Breast Neoplasms / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D005260:Female; D006801:Humans; D042361:Mammary Glands, Human / Q000166:cytology / Q000378:metabolism; D009924:Organ Culture Techniques; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D053218:Receptors, Death Domain / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism
chemical_list: D016271:Proto-Oncogene Proteins c-myc; D053218:Receptors, Death Domain; D053221:TNF-Related Apoptosis-Inducing Ligand; D017346:Protein Serine-Threonine Kinases; C109790:STK11 protein, human; D000091162:AMP-Activated Protein Kinase Kinases