Referee 1's Review:

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N.B. These are the comments made by the referee when reviewing an earlier version of this paper. Prior to publication, the manuscript has been revised in light of these comments and to address other editorial requirements.
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This manuscript describes studies on the potential functional role of canonical Wnt signaling in prostate ductal morphogenesis as well as cancer cell growth. A number of new observations are presented, although these are not always well-documented.

1) The authors make confusing and inconsistent statements concerning the relationship of basal cells to prostate epithelial progenitor cells. Presumably only a small fraction of basal cells correspond to stem cells, so it is difficult to draw any conclusions about stem/progenitor cells simply by examining the number of basal cells. Since the authors never examine any specific markers for stem/progenitor cells, the numerous references to effects of Wnt signaling on stem/progenitor and cancer stem cells in the text are overly speculative.

2) No information is provided on numbers of samples in the experiments presented. This is particularly apparent in Figs. 1, 2, 3, and 5. The effects of Wnt3a and Dkk1 on ductal morphogenesis are described in Fig. 1, but are not quantitated in any way.

3) The immunofluorescence data are generally poor in quality. The images in Fig. 3A-F are difficult to visualize, as the signal is barely detectable over background, while the data in Fig. 5A-L are presented at low resolution. In Fig. 5A-C, it appears that many beta-galactosidase positive cells are luminal, not basal, which should be noted in the text and figure legend. The axis labeling in Fig. 5N is confusing, since it implies that all/most p63-positive cells are beta-galactosidase positive, which does not appear to be the case.

4) No error bars or statistical analysis are shown in Figs. 3, 4, or 6.