RUNX1 and neoplasm: Certain pre-B tumor cell lines expressed Lhx2 [67], but we did not observe B cell tumors in iB-μMT mice, indicating that simultaneous expression of Lhx2 with Hoxa9 and Runx1 starting from an early stage of hematopoietic development prior to definitive HSC occurrence leads to no obvious tumorigenic effect.