RUNX1T1 and acute myeloid leukemia: Cells expressing Gr1 at intermediate levels (Gr1int) represent immature myeloid forms and were, as anticipated, present at a low frequency (approx. 10–20%) in the Mac1+Gr1+ myeloid cell population of control mice as well as in the un-transduced (AML-ETO−) cell population in mice transplanted with AML-ETO+ cells, while they are found at high frequency (approx. 60%) among AML-ETO transduced myeloid cells, consistent with an overall enlarged immature myeloid compartment (Figure 2A) and myeloproliferative phenotype [33].