For example, RUNX2 is endogenously expressed in selected breast cancer cell lines as evidenced by detection of RUNX2 protein by western blot analysis in highly malignant MDA-MB-231 breast adenocarcinoma cells, but not in MCF7 breast adenocarcinoma cells that retain several characteristics of differentiated mammary epithelium (Figure 1A). The gene discussed is RUNX2; the disease is breast cancer.