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Proliferation and differentiation in the human breast during pregnancy

Authors

  • R. Suzuki,

    Corresponding author
    1. Ludwig Institute for Cancer Research (LICR)/
      University College London (UCL) Schoold of Medicine
      Breast Cancer Research Laboratory, Department of Surgery
      Charles Bell House, 67–73 Riding House Street
      London, W1W 7EJ UK
      Ludwig Institute for Cancer Research (LICR)/
      University College London (UCL) Schoold of Medicine
      Breast Cancer Research Laboratory, Department of Surgery
      Charles Bell House, 67–73 Riding House Street
      London, W1W 7EJ UK
      Tel: + 44 207 679 9055, Fax: + 44 207 679 9508
      e-mail: r.suzuki@ucl.ac.uk
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  • A.J. Atherton,

    1. Ludwig Institute for Cancer Research (LICR)/
      University College London (UCL) Schoold of Medicine
      Breast Cancer Research Laboratory, Department of Surgery
      Charles Bell House, 67–73 Riding House Street
      London, W1W 7EJ UK
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  • M.J. O’Hare,

    1. Ludwig Institute for Cancer Research (LICR)/
      University College London (UCL) Schoold of Medicine
      Breast Cancer Research Laboratory, Department of Surgery
      Charles Bell House, 67–73 Riding House Street
      London, W1W 7EJ UK
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  • A. Entwistle,

    1. Ludwig Institute for Cancer Research (LICR)/
      Royal Free and University College School of Medicine Branch
      Courtauld Building
      91 Riding House Street
      London, W1W 7BS UK
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  • S.R. Lakhani,

    1. Department of Histopathology
      Royal Free and University College Medical School
      Rockefeller Building
      University Street
      London, WC1E 6JJ UK
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  • C. Clarke

    1. Ludwig Institute for Cancer Research (LICR)/
      University College London (UCL) Schoold of Medicine
      Breast Cancer Research Laboratory, Department of Surgery
      Charles Bell House, 67–73 Riding House Street
      London, W1W 7EJ UK
    Search for more papers by this author

Ludwig Institute for Cancer Research (LICR)/
University College London (UCL) Schoold of Medicine
Breast Cancer Research Laboratory, Department of Surgery
Charles Bell House, 67–73 Riding House Street
London, W1W 7EJ UK
Tel: + 44 207 679 9055, Fax: + 44 207 679 9508
e-mail: r.suzuki@ucl.ac.uk

Abstract

Abstract Using multiple immunofluorescence labelling on human breast tissues obtained and freshly frozen at the 12th, 15th, and 18th weeks of pregnancy, we have shown that markers of mammary functional differentiation, milk proteins (β-casein and κ-casein), are synthesised by actively cycling (Ki67 positive) as well as non-cycling (Ki67 negative) cells. These results demonstrate that functional differentiation/maturation does not coincide with loss of proliferative potential in human mammary luminal epithelial cells. In addition, we have examined expression patterns of integrin subunits (α1, α2, α3, α6, β1, and β4) and extracellular matrix components (laminin, fibronectin, collagen I, and collagen IV), since they have been shown to exert influences on mammary differentiation and morphogenesis in vitro. Compared to human breast tissues obtained from non-pregnant women, a decrease in α2 labelling on luminal epithelial cells was observed, particularly in expanding acini that showed abundant Ki67 positivity. The expression patterns of other integrin subunits, however, did not change, indicating that the expression patterns of most integrins existing prior to pregnancy are sufficient to support the morphological and functional development associated with milk protein synthesis.

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