GPT and breast carcinoma: To test these constructs for cell type specificity, we used HepG2 (hepatocyte carcinoma), 293T (embryonic kidney), and HCT116 (colorectal carcinoma) cells; the only construct that influenced transcription from the IGFBP5 promoter in these non-breast cells was PRE2DEL-ALT/ALT in 293T cells and with an effect size that was an order of magnitude lower (FC = 1.9, p = 0.002; Figure S4) compared to the breast cancer cell lines (FC > 40; Figure 2).