Clonal RbloxP/LoxP mouse prostatic epithelial cells (MPECs) undergo multilineage differentiation in vivo. MPECs were isolated from RbloxP/LoxP animals as previously described [27]. The parental population was subjected to limiting dilution as described for WFU3 MPECs, and clones were grafted with rat urogenital mesenchyme in nude mice. (A): Histology of two independent clones shows luminal structures. (B): Immunodetection of p63 and AR shows a defined basal layer (arrows) and a defined luminal layer (arrowheads). (C): In vitro, the parental cells expressed luminal (CK8 and AR) and basal (CK14 and p63) markers. Insets show 4,6-diamidino-2-phenylindole stain. Original magnification, ×60. Abbreviations: AR, androgen receptor; CK, cytokeratin; um, micrometer.