CDKN1A and breast cancer: Moreover, the antitumor effects of berberine and berberine derivatives in human HER-2/neu overexpressing breast cancer cells are mediated not only by apoptotic cell death but also by increased expression of p53, p21, p16, and PAI-1 mRNAs, thus suggesting that the mechanism of action of berberine may also include the induction of CS [237].