PIN1 and breast cancer: Unlike other transcriptional factors, Notch1 specifically binds the distal BS1 element of PIN1 promoter and directly triggers PIN1 transcription, where Pin1 potentiates Notch1 cleavage by γ-secretase to increase Notch1 transcriptional activity, thereby generating a positive loop to upregulate Pin1 expression in human breast cancer (Takahashi et al., 2007; Rustighi et al., 2009, 2013).