For example, Wei and colleagues demonstrated that CAF release CXCL12 which in turn upregulates the expression of the nuclear matrix attachment region-binding protein SATB-1 in PC cells; through a reciprocal feedback loop between fibroblasts and tumor cells, SATB-1 is involved in maintenance of CAF features (i.e., α-SMA, fibroblast activation protein and CXCL12) and gemcitabine resistance [113]. The gene discussed is ACTA1; the disease is pachyonychia congenita.