TP53 and breast cancer: By double labeling, first with SA-β-Gal to identify SC and then by antibodies that recognize biomarkers expressed in SC, we found that LGD1069 induced RARβ2, p21, p16 and pRB, but not p53 expression in MMTV-Neu mammary tumors, suggesting a p53 independent mechanisms of CS (Fig. 3).