Molecular inhibitors of the oncogenic property of AML1/ETO

Coordinator:		Prof. Dr. Manuel Grez
Institution:		Georg-Speyer-Haus Frankfurt
Homepage:		www.georg-speyer-haus.de/grps/

AML1/ETO is found in high molecular weight complexes (HMWC) of about 2 mDa, which are crucial for the block in myeloid differentiation observed in AML1/ETO transformed cells. Essential for HMWC formation is the nervy homology region 2 (NHR2) within ETO, an hydrophobic amino acid heptad repeat which forms a tetramer through hydrophobic and ionic/polar interactions and serves as interface for the association with members of the ETO protein family as well as for self-association. The deletion of the NHR2 domain fully abrogates the oncogenic properties of AML1/ETO arguing for a central role of the NHR2 oligomerization domain for leukemogenesis. In this project we aim to characterize the tetramer domain in more detail. We are particular interested in the different molecular forms of AML1/ETO: the monomer, the dimer and the tetramer and their leukemogenic properties. We further plan to develop and test small peptide inhibitors of AML1/ETO oligomerization as putative molecular drugs for the treatment of leukemias with t(8;21). We have already been able to derive a 128 amino acids long protein fragment (NC128), which upon expression in AML1/ETO transformed cells disrupted the stability of the AML1/ETO HMW complexes leading to AML1/ETO complexes of less than 2 mDa molecular weight. Furthermore, expression of NC128 restored transcription of AML1/ETO target genes and down regulated the expression of cell cycle regulatory genes, which are up-regulated in AML1/ETO–expressing cells. In line with these findings expression of NC128 reverted the differentiation block induced by AML1/ETO in myeloid cells. Moreover, NC128 acts synergistically with known inhibitors of histone deacetylase activity (VPA) to revert the AML1/ETO induced differentiation block. Also, in the presence of NC128 AML1/ETO transformed cells lose their progenitor cell characteristics, are arrested in cell cycle progression and undergo cell death. Finally, the immortalization effect of AML1/ETO on primary CD34+ cells was reverted in the presence of NC128. Therefore we propose the oligomerization domain of AML1/ETO as a valid target for a molecular intervention in t(8;21) leukemias.