1 Title: Collagen architecture in pregnancy-induced protection from breast cancer Ori Maller 1,2 , Kirk C. Hansen 3 , Traci R. Lyons 1 , Irene Acerbi 4,5 , Valerie M. Weaver 4,5 , Rytis Prekeris 6 , Aik-Choon Tan 1 and Pepper Schedin 1,2, 6,7* 1 Division of Medical Oncology, School of Medicine, University of Colorado Anschutz Medical Campus, 12801 E 17 th Ave, Aurora, CO, USA 80045. 2 Program in Cancer Biology, University of Colorado Anschutz Medical Campus, MS8104, RC- 1S, 5117, 12801 E 17 th Ave, Aurora, CO, USA 80045. 3 Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Anschutz Medical Campus, 12801 E 17 th Ave, Aurora, CO, USA 80045 4 Department of Surgery and Center for Bioengineering and Tissue Regeneration, University of California, San Francisco, 513 Parnassus Ave, San Francisco, CA USA 94143. 5 Bay Area Physical Sciences–Oncology Center, University of California–Berkeley, Berkeley California, Stanley Hall 478, Berkeley, CA, USA 94720 6 Department of Cell and Developmental Biology; School of Medicine; University of Colorado Anschutz Medical Campus; 12801 E 17 th Ave, Aurora, CO, USA 80045 7 University of Colorado Cancer Center, Bldg 500, Suite 6004C, 13001 E 17 th Place, Aurora, CO, USA 80045. Running title: Collagen I in parity-induced protection Keywords: E-Cadherin, Collagen organization, Integrin Signaling, Tumor Suppressive ECM Corresponding Author: Pepper Schedin, PhD, Division of Medical Oncology, MS 8117, RC-1 S, 8401K, 12801 E. 17 th Avenue, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, Phone: 303-724-3873, Fax: 303-724-3889, Email: Pepper.Schedin@UCDenver.edu Reprint Request: Pepper Schedin, PhD, Division of Medical Oncology, MS 8117, RC-1 S, 8401K, 12801 E. 17 th Avenue, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 Conflict of interest: None Word count for text and figure legends: 8,416words Number of figures: 7 Abbreviations: 3D Cell Culture, Adamts1, AFM, BrdU, COMIRB, DCIS, DMSO, ECM, ERK1/2, FAK, FFTP, FN, H&E, IB, IFI, LC-MS/MS, LOX, MEK1/2, Mmp, MW, NF Collagen I, PBS, PyMT, SHG, Snai2, TIC, Timp, Vcam1, Vim, Zeb1 © 2013. Published by The Company of Biologists Ltd. Journal of Cell Science Accepted manuscript JCS Advance Online Article. Posted on 10 July 2013