Similar to parental normal Type 1 HBECs [21,22,24] and immortal R2d [16] cells, as well as human breast carcinoma cells such as MCF-7, the R2N1d cells expressed Oct-4 and luminal epithelial cells markers, cytokeratin 18 and 19 (Figure 1C). The gene discussed is POU5F1; the disease is breast carcinoma.