NANOG and breast cancer: 6-gingerol inhibited tumor sphere formation in breast cancer, through (i) the down-regulation of Nanog, Oct-3/4, Sox-2, (ii) the up-regulation of p53 and Bax proteins, (iii) the down-regulation of Bcl-2 anti-apoptotic proteins, and (iv) the inhibition of STAT3 [215].