SLC9A1 and breast cancer: To determine which of the two PPREs within the human NHE1 is the true PPARγ binding site, we transfected MCF-7 breast cancer cells with a full length NHE1 promoter construct (containing both PPRE1 and PPRE2) compared to a parallel set up transfected with a 5' deletion of the full length (only contains PPRE2) (Figure 5A).