To determine whether Plexin-B1 contributes to prostate cancer progression in vivo, we tested the effect on tumor growth and metastasis of manipulating Plexin-B1 expression in two different transgenic mouse models of prostate cancer which recapitulate these common genetic alterations and which also metastasize: PbCre+Ptenfl/flKrasG12V (ref. 42; hereafter abbreviated to Ptenfl/flKrasG12V) and PbCre+Ptenfl/flp53fl/fl (ref. 43; hereafter abbreviated to Ptenfl/flp53fl/fl). Here, PLXNB1 is linked to Familial prostate cancer.