Reviewer #1 (Public review): Replication stress-inducing ELF3 upregulation promotes BRCA1-deficient breast tumorigenesis in luminal progenitors

In this fundamental study, the authors describe ELF3 as a candidate driver of luminal progenitor transformation, such that its up-regulation during replicative stress conditions and in BRCA1 deficient cells may permit cell proliferation by suppressing genome instability.While the work is certainly of interest, the supporting data remain incomplete as luminal progenitor cells could not be isolated, which would be needed in order to definitively determine whether ELF3 is a driver of transformation in these cells.Overall this paper may offer insight into mechanisms by which BRCA1 deficiency fuels breast tumorigenesis.