POU1F1 and breast cancer: Using breast cancer cell lines with different levels of Pit-1 (MCF-7, MCF-7/Pit-1, MDA-MB-231, and MDA-MB-231/shPit-1), which therefore had different sensitivity to DNA-damage agents (see Figure 1E), MTT assays were performed to evaluate cell proliferation after treatment with 3-Epi, cisplatin, and both together.