PIN1 and cancer: We next tested the effects of increasing doses of KPT-6566 on an isogenic cell model constituted of (i) non-transformed MCF10A mammary epithelial cells, which express lower levels of PIN1 than cancer cell lines, and in which the enzyme is mainly inactivated due to S71 phosphorylation12, and (ii) H-RasV12-transformed MCF10AT1 cells28 which, instead, express high levels of active PIN1 (Fig. 2e, left).