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P Accornero, Grugliasco, Italy
S Miretti, Dip. di Morfofisiologia Veterinaria, Università di Torino, Grugliasco, Italy
L Starvaggi Cucuzza, Grugliasco, Italy
E Martignani, Grugliasco, Italy
M Baratta, Grugliasco, Italy

Correspondence: Paolo Accornero, Email: paolo.accornero{at}unito.it

Abstract

The development of the mammary gland requires an integrated response to specific growth factors and steroid hormones. Hepatocyte Growth Factor (HGF) and its tyrosine kinase receptor, Met, are expressed and temporally regulated during mammary development and differentiation. Epidermal Growth Factor Receptor (EGFR) and its ligands have also been implicated in mammary gland growth and morphogenesis. Since both cytokines seem to exert a morphogenic program in this tissue, we have investigated the possible concerted action of Epidermal Growth Factor (EGF) and HGF on the HC11 cell line, a widely used model of non tumorigenic mammary cells. Western-blot analysis indicated that HC11 expressed Met and EGFR and showed ERK1/2 and AKT activation following HGF or EGF treatment. Analysis by real-time PCR and western-blot showed that, after a EGF but not HGF or Insulin-like Growth Factor-I treatment, HC11 mammary cells exhibited an increase in Met expression at both the mRNA and protein levels which was dependent on the AKT pathway. Simultaneous treatment with HGF and EGF increased proliferation, scatter and invasion as assessed by cell count, cell cycle, scatter and transwell assays. AKT inhibition did not influence the cooperation on proliferation or invasion after HGF + EGF treatment while ERK1/2 inhibition abolished Met/EGFR cooperation on proliferation. HGF + EGF treatment increased the duration of ERK1/2 and AKT activation compared to HGF or EGF alone. All these data indicate that a cross-talk between the EGF and the HGF pathways in mammary epithelial cells may modulate the development of the mammary gland.