title: CCL2-driven inflammation increases mammary gland stromal density and cancer susceptibility in a transgenic mouse model.
abstract: Macrophages play diverse roles in mammary gland development and breast cancer. CC-chemokine ligand 2 (CCL2) is an inflammatory cytokine that recruits macrophages to sites of injury. Although CCL2 has been detected in human and mouse mammary epithelium, its role in regulating mammary gland development and cancer risk has not been explored.
  
  
  
  Transgenic mice were generated wherein CCL2 is driven by the mammary epithelial cell-specific mouse mammary tumour virus 206 (MMTV) promoter. Estrous cycles were tracked in adult transgenic and non-transgenic FVB mice, and mammary glands collected at the four different stages of the cycle. Dissected mammary glands were assessed for cyclical morphological changes, proliferation and apoptosis of epithelium, macrophage abundance and collagen deposition, and mRNA encoding matrix remodelling enzymes. Another cohort of control and transgenic mice received carcinogen 7,12-Dimethylbenz(a)anthracene (DMBA) and tumour development was monitored weekly. CCL2 protein was also quantified in paired samples of human breast tissue with high and low mammographic density.
  
  
  
  Overexpression of CCL2 in the mammary epithelium resulted in an increased number of macrophages, increased density of stroma and collagen and elevated mRNA encoding matrix remodelling enzymes lysyl oxidase (LOX) and tissue inhibitor of matrix metalloproteinases (TIMP)3 compared to non-transgenic controls. Transgenic mice also exhibited increased susceptibility to development of DMBA-induced mammary tumours. In a paired sample cohort of human breast tissue, abundance of epithelial-cell-associated CCL2 was higher in breast tissue of high mammographic density compared to tissue of low mammographic density.
  
  
  
  Constitutive expression of CCL2 by the mouse mammary epithelium induces a state of low level chronic inflammation that increases stromal density and elevates cancer risk. We propose that CCL2-driven inflammation contributes to the increased risk of breast cancer observed in women with high mammographic density.
authors.affiliation: Discipline of Obstetrics and Gynaecology, School of Medicine, University of Adelaide, Adelaide, Australia.|The Robinson Research Institute, University of Adelaide, Adelaide, Australia.
authors.forename: Xuan
authors.initials: X
authors.lastname: Sun
authors.affiliation: Discipline of Obstetrics and Gynaecology, School of Medicine, University of Adelaide, Adelaide, Australia.|The Robinson Research Institute, University of Adelaide, Adelaide, Australia.|Discipline of Surgery, School of Medicine, The Queen Elizabeth Hospital, University of Adelaide, DX465702, 28 Woodville Rd, Woodville, 5011, Australia.
authors.forename: Danielle J
authors.initials: DJ
authors.lastname: Glynn
authors.affiliation: The Robinson Research Institute, University of Adelaide, Adelaide, Australia.|Discipline of Surgery, School of Medicine, The Queen Elizabeth Hospital, University of Adelaide, DX465702, 28 Woodville Rd, Woodville, 5011, Australia.
authors.forename: Leigh J
authors.initials: LJ
authors.lastname: Hodson
authors.affiliation: The University of Melbourne Department of Surgery, St Vincent's Hospital Melbourne, Fitzroy, Australia.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Huo
authors.affiliation: Metastasis Research Laboratory, Peter MacCallum Cancer Centre, Melbourne, Australia.|The Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Australia.
authors.forename: Kara
authors.initials: K
authors.lastname: Britt
authors.affiliation: The University of Melbourne Department of Surgery, St Vincent's Hospital Melbourne, Fitzroy, Australia.|Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology and Translational Research Institute, Queensland, Australia.
authors.forename: Erik W
authors.initials: EW
authors.lastname: Thompson
authors.affiliation: School of Veterinary Sciences, University of Adelaide, Roseworthy, SA, Australia.
authors.forename: Lucy
authors.initials: L
authors.lastname: Woolford
authors.affiliation: Discipline of Surgery, School of Medicine, The Queen Elizabeth Hospital, University of Adelaide, DX465702, 28 Woodville Rd, Woodville, 5011, Australia.
authors.forename: Andreas
authors.initials: A
authors.lastname: Evdokiou
authors.affiliation: MRC and University of Edinburgh Centre for Reproductive Health, Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK.
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Pollard
authors.affiliation: Discipline of Obstetrics and Gynaecology, School of Medicine, University of Adelaide, Adelaide, Australia.|The Robinson Research Institute, University of Adelaide, Adelaide, Australia.
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Robertson
authors.affiliation: The Robinson Research Institute, University of Adelaide, Adelaide, Australia. wendy.ingman@adelaide.edu.au.|Discipline of Surgery, School of Medicine, The Queen Elizabeth Hospital, University of Adelaide, DX465702, 28 Woodville Rd, Woodville, 5011, Australia. wendy.ingman@adelaide.edu.au.
authors.forename: Wendy V
authors.initials: WV
authors.lastname: Ingman
mesh_terms: D000818:Animals; D000071060:Breast Density; D001943:Breast Neoplasms / Q000209:etiology* / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D018932:Chemokine CCL2 / Q000235:genetics / Q000378:metabolism*; D002634:Chemotaxis, Leukocyte / Q000235:genetics / Q000276:immunology; D004195:Disease Models, Animal; D004198:Disease Susceptibility; D004848:Epithelium / Q000378:metabolism; D030762:Estrous Cycle; D005260:Female; D015870:Gene Expression; D006801:Humans; D007249:Inflammation / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D053208:Kaplan-Meier Estimate; D008264:Macrophages / Q000276:immunology / Q000378:metabolism; D042361:Mammary Glands, Human / Q000378:metabolism / Q000473:pathology; D008325:Mammary Neoplasms, Experimental; D051379:Mice; D008822:Mice, Transgenic; D011379:Prognosis; D012333:RNA, Messenger / Q000235:genetics; D017154:Stromal Cells / Q000378:metabolism* / Q000473:pathology
chemical_list: D018932:Chemokine CCL2; D012333:RNA, Messenger
keywords: Chemokine (C-C motif) ligand 2; Development; Macrophage; Mammary gland; Mammographic density; Mouse model