Breast stromal fibroblasts from histologically normal surgical margins are pro‐carcinogenic

<jats:title>Abstract</jats:title><jats:p><jats:bold>There is evidence that normal breast stromal fibroblasts (<jats:styled-content style="fixed-case">NBFs</jats:styled-content>) suppress tumour growth, while cancer‐associated fibroblasts (<jats:styled-content style="fixed-case">CAFs</jats:styled-content>) promote tumourigenesis through functional interactions with tumour cells. Little is known about the biology and the carcinogenic potential of stromal fibroblasts present in histologically normal surgical margins (<jats:styled-content style="fixed-case">TCFs</jats:styled-content>). Therefore, we first undertook gene expression analysis on five <jats:styled-content style="fixed-case">CAF</jats:styled-content>/<jats:styled-content style="fixed-case">TCF</jats:styled-content> pairs from breast cancer patients and three <jats:styled-content style="fixed-case">NBF</jats:styled-content> samples (derived from mammoplasties). This comparative analysis revealed variation in gene expression between these three categories of cells, with a <jats:styled-content style="fixed-case">TCF</jats:styled-content>‐specific gene expression profile. This variability was higher in <jats:styled-content style="fixed-case">TCFs</jats:styled-content> than in their paired <jats:styled-content style="fixed-case">CAFs</jats:styled-content> and also <jats:styled-content style="fixed-case">NBFs</jats:styled-content>. Cytokine arrays show that <jats:styled-content style="fixed-case">TCFs</jats:styled-content> have a specific secretory cytokine profile. In addition, stromal fibroblasts from surgical margins expressed high levels of <jats:italic>α</jats:italic>‐<jats:styled-content style="fixed-case">SMA</jats:styled-content> and <jats:styled-content style="fixed-case">SDF</jats:styled-content>‐1 and exhibited higher migratory/invasiveness abilities. Indirect co‐culture showed that <jats:styled-content style="fixed-case">TCF</jats:styled-content> cells enhance the proliferation of non‐cancerous mammary epithelial cells and the epithelial‐to‐mesenchymal transition of breast cancer cells. Moreover, <jats:styled-content style="fixed-case">TCF</jats:styled-content> and <jats:styled-content style="fixed-case">CAF</jats:styled-content> cells increased the level of <jats:styled-content style="fixed-case">PCNA</jats:styled-content>, <jats:styled-content style="fixed-case">MMP</jats:styled-content>‐2 and the phosphorylated/activated form of Akt in normal breast luminal fibroblasts in a paracrine manner. Furthermore, <jats:styled-content style="fixed-case">TCFs</jats:styled-content> were able to promote the formation and growth of humanized orthotopic breast tumours in nude mice. Interestingly, these <jats:styled-content style="fixed-case">TCF</jats:styled-content> phenotypes and the extent of their effects were intermediate between those of <jats:styled-content style="fixed-case">NBFs</jats:styled-content> and <jats:styled-content style="fixed-case">CAFs</jats:styled-content>. Together, these results indicate that stromal fibroblasts located in non‐cancerous tissues exhibit a tumour‐promoting phenotype, indicating that their presence post‐surgery may play important roles in cancer recurrence. © 2013 The Authors. Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.</jats:bold></jats:p>