Gene expression in ECoM-G clones, whose differentiation arrest is re-established by heterologous oncoproteins, reveals profiles unique to the second oncoprotein.

Northern blot analysis of gene expression was performed on RNA samples from 3 ECoM-G clones cultured in the presence (+E2) and absence (−E2) of estrogen for the indicated number of days. RNA was also harvested from clones whose differentiation arrest in the absence of estrogen was re-established by Hoxa9, wild-type E2a/Pbx1, Hoxb8, PML/RARα, PLZF/RARα, Nup98/HoxA9, and AML1/ETO. These stable populations demonstrated continued and indefinite proliferation in the absence of estrogen and were cultured in the absence of estrogen for at least 4 to 5 weeks prior to the harvest of RNA. The heterologous oncoproteins were all cloned into MSCV-based vectors and introduced into the ECoM-G cells by retroviral infection. RNA from NIH3T3 fibroblasts was used as a nonmyeloid control.