RUNX2 and neoplasm: However, comparative analyses of a recently established Runx2-conditional knockout mouse line (Runx2-flox) [66] with Runx1- and Runx3-flox lines showed that Runx2 plays a smaller role as a tumor-promoting factor in p53-deficient OS and T-cell lymphoma than do Runx3 and Runx1, respectively [32,53].