SRIF-activated PTPs inhibit cell proliferation by dephosphorylating tyrosine kinase receptors and/or downstream effectors, such as platelet-derived growth factor receptor, as demonstrated in SST1-expressing pancreatic cancer–associated fibroblasts (Duluc et al., 2015), or by inducing cell cycle arrest via upregulation of p21 (cip1/Waf1) expression in SST1-transfected cells (Florio et al., 1999). The gene discussed is CDKN1A; the disease is familial pancreatic carcinoma.