Clinical and functional significance of loss of caveolin-1 expression in breast cancer-associated fibroblasts

The Journal of Pathology, 04/09/2012

Simpkins SA et al. – Loss of stromal Cav-1 in breast cancer predicts poor outcome. At a functional level, Cav-1 deficient CAFs are capable of significantly increasing the invasive capacity of breast cancer cells.

Methods

  • Cav-1 stromal expression was immunohistochemically assessed in 358 breast cancers. Cav-1 expression in primary breast fibroblasts was analysed by western blot.
  • Modified Boyden chamber assays determined fibroblast ability to promote invasion of breast cancer cells.
  • The impact of siRNA-silencing of Cav-1 in fibroblasts was evaluated using invasion assays and 3D co-culture assays.

Results

  • Loss of Cav-1 expression in breast stroma was significantly associated with decreased breast cancer-specific and disease-free survival (p = 0.01).
  • Mean survival was 72 months (Cav-1+ group) versus 29.5 months (Cav-1- group).
  • Cav-1 expression was significantly decreased in CAFs compared to normal fibroblasts (p = 0.01) and was associated with increased invasion promoting capacity.
  • Cav-1 siRNA treated fibroblasts promoted significantly increased invasion of MDA-MB-468 and T47D breast cancer cells from 27% (control) to 67% (p = 0.006) and 37% to 56%, respectively (p = 0.01).
  • 3-dimensional co-cultures of MDA-MB-468 cells with myoepithelial cells led to formation of organised cohesive structures when cultured with conditioned media from fibroblasts but resulted in a disorganised appearance in the presence of conditioned media from Cav-1 siRNA-treated fibroblasts, accompanied by loss of E–cadherin expression in tumour cells.

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