POU5F1 and breast carcinoma: In 2015, Tang et al. generated the novel SOX2-OCT4 reporter system designated the SOX2/OCT4 response element (SORE6-GFP) which they used to isolate breast cancer stem cells with self-renewal and tumor-initiating ability as well as drug resistance, paving the way to use this reporter system to identify gastric CSCs [50].