There is evidence that nicotine can induce the expression of SOX2 to enhance the self-renewal of CSCs in non-small cell lung adenocarcinoma (NSCLC), and OCT4 may act on this process [34].By inhibiting the expression of SOX2, the characteristics of CSC can be repressed, making breast cancer cells sensitive to tamoxifen [35]. Here, POU5F1 is linked to breast cancer.