Moreover, MMTV-Runx2 failed to promote tumorigenesis in MMTV-PyMT and MMTV-ErbB2 models (not shown), which have been molecularly compared to luminal (ER+) breast cancers (Herschkowitz et al., 2007), again highlighting its role in subtype-specific disease. This evidence concerns the gene RUNX2 and breast cancer.