Breast cancer subpopulations selected for high Rad6B promoter activity display elevated β-catenin levels and activity, which is suppressed by LRP6 inhibition. (A) Fluorescence/phase contrast images of MDA-MB-231 cells stably transfected with Rad6B promoter-ZsGreen1 reporter vector. (B) FACS analysis of MDA-MB-231 cells transfected with promoterless (a) or Rad6B promoter-ZsGreen1 (b) vector. Panel c, FACS profile of R6B-Zshigh cells transfected with mutant LRP6Δ173. Insets in b represent fluorescence images of sorted subpopulations with low (Zs low) and high (Zs high) green fluorescence. (C) Rad6B mRNA expression relative to GAPDH in the indicated cells determined by semi-quantitative RT-PCR. (D) Steady-state levels of indicated proteins in the cytosols of indicated MDA-MB-231 subpopulations. (E) Relative Rad6B promoter activity in MDA-MB-231 cells transfected with Rad6B promoter-luciferase and pRLTK. (F) Relative pTOP/Flash or pFOP/Flash reporter activities in MDA-MB-231 cells. The data shown in E and F are averages (± S.E.M) of three separate experiments performed in duplicate.