POSTN and breast cancer: These activated CAFs express several known pro‐metastatic secreted factors including angiopoietin‐like‐4 (ANGPTL‐4) (Padua et al., 2008), connective tissue growth factor (CTGF) (Kang et al., 2003), tenascin C (TNC) (Oskarsson et al., 2011) – functionally described in breast cancer – and periostin (POSTN), a promoter of metastatic growth in colon cancer that increases cell survival via the AKT pathway (Bao et al., 2004).