CDKN1A and breast cancer: Ocy454 cells treated with CM from EO771 or MDA-231 breast cancer cells for nine days exhibited hallmarks of cellular senescence, including flattened and enlarged morphology (not shown), upregulation of the senescent markers p16Ink4a and p21Cip1 and the SASP-related factors Il6 and Mmp13 compared to control Ocy454 cells (Fig. 3a,d), high senescence-associated (SA)-β-Gal activity (Fig. 3b,e), and increased prevalence of SA-β-Gal+ cells (Fig. 3c,f).