ErbB2, but not ErbB1, reinitiates proliferation and induces luminal repopulation in epithelial acini

Abstract

Both ErbB1 and ErbB2 are overexpressed or amplified in breast tumours. To examine the effects of activating ErbB receptors in a context that mimics polarized epithelial cells in vivo, we activated ErbB1 and ErbB2 homodimers in preformed, growth-arrested mammary acini cultured in threedimensional basement membrane gels. Activation of ErbB2, but not that of ErbB1, led to a reinitiation of cell proliferation and altered the properties of mammary acinar structures. These altered structures share several properties with early-stage tumours, including a loss of proliferative suppression, an absence of lumen, retention of the basement membrane and a lack of invasive properties. ErbB2 activation also disrupted tight junctions and the cell polarity of polarized epithelia, whereas ErbB1 activation did not have any effect. Our results indicate that ErbB receptors differ in their ability to induce early stages of mammary carcinogenesis in vitro and this three-dimensional model system can reveal biological activities of oncogenes that cannot be examined in vitro in standard transformation assays.The mammary epithelium of an adult breast is organized into ducts and lobules. The ducts end in a highly branched structure referred to as the terminal ductal lobular unit (TDLU). A TDLU is comprised of multiple individual units referred to as mammary acini. Each acinus has a central lumen, a single layer of polarized luminal epithelial cells surrounded by myoepithelial cells, and a basement membrane.We have previously shown that human mammary epithelial cells (MECs) form acini-like structures containing a single layer of polarized, growth-arrested cells when grown within a matrix rich in laminin and collagen IV (Matrigel, derived from the Englebreth-Holm Swarm (EHS) tumour) 1,2 . The epithelial cells within acini in vivo and in culture have an apico-basal distribution of polarity markers such as ZO-1, E-cadherin and α 6 β 4 integrins. They also deposit collagen IV and secrete sialomucin in their basal and apical surfaces, respectively 1,2 , indicating that the acinar structures formed in culture closely mimic the acini in an adult breast.Early stages of breast cancer (hyperplasia and ductal carcinoma in situ (DCIS)) are characterized by an increased proliferation of epithelial cells, a loss of acinar organization and § Correspondence and requests for materials should be addressed to J.S.B. joan_brugge@hms.harvard.edu. † Present addresses: Cold Spring Harbor Laboratories, Cold Spring Harbor, New York 11724, USA (S.K.M.); Department of Basic Medical Sciences, Purdue University, West Lafayette, Indiana 47907, USA (S.L.)Supplementary information is available on Nature Cell Biology's website (http://cellbio.nature.com) or as paper copy from the London editorial office of Nature Cell Biology. NIH Public Access Author ManuscriptNat Cell Biol. Author manuscript; available in PMC 2010 October 11. filling of the luminal space 3 . However, a lack of acinar organization and the acquisition of invasive behaviour are later events involved...

Cellular ITAM-containing proteins are oncoproteins in nonhematopoietic cells

“…These structures faithfully recapitulate, in vitro, the acinar architecture of mammary epithelium in vivo, including apical-basal polarization of luminal epithelial cells surrounding a hollow lumen (reviewed in Jacks and Weinberg, 2002). This experimental model has proven useful for dissecting the molecular processes associated with oncogene-induced transformation of MECs, including that induced by activated ErbB2 (Muthuswamy et al, 2001) and altered integrin expression (Weaver et al, 1997;Zahir et al, 2003).…”

Neuregulin activates erbB2-dependent src/FAK signaling and cytoskeletal remodeling in isolated adult rat cardiac myocytes

“…FAK is a substrate of Src, and both FAK and Src are activated in cancer cells overexpressing erbB2 or stimulated with erbB ligand [13,14]. Furthermore, p130 CAS is a FAK-interacting protein, and is frequently hyper-phosphorylated in erbB2 overexpressing or Src transformed cells [15,16].…”

Oncogenic transformation of normal breast epithelial cells co-cultured with cancer cells

“…This cell model exhibits cancerous properties and clinical characteristics of breast cancer [16,17]. To test our hypothesis, we mixed MCF10A and MCF10A.NeuT or control MCF10A.pBabe cells at a 1:1 ratio.…”

“…However, activation of ErbB2 in epithelial cells disrupts normal structure of acini morphogenesis by protecting luminal cells from apoptosis and disrupting apical polarity [16], which is a character of early stages of breast cancer (hyperplasia and ductal carcinoma in situ (DCIS)) [18]. Several genes that are required for the development and maintenance of epithelial polarity have been identified including hDlg1 that plays an important role in controlling cell polarization during oriented migration of epithelial cells [19].…”

“…We showed that MCF10A cells became cancerous following co-culture with MCF10A.NeuT cells. It had been established that ErbB2 continuous expression can initiate the early stages of mammary carcinogenesis [16]. C2 and C3 cells displayed common features such as lose of epithelial cell characteristics including loss of apical-basal polarity that resulted in abnormally structured acini.…”