CDKN1A and breast cancer: For instance, in MDA-MB-231 human breast cancer cells, oleocanthal triggers G1/M arrest by downregulating the expression of CDK6 and cyclin D1 while upregulating p21 and p27 expression, and this is confirmed with mitosis suppression via reduction in proliferation marker (Ki-67) positive staining in the tumor tissue of the MDA-MB-231 xenograft model [39].