SH2 domains are attractive targets for chemotherapeutic agents due to their involvement in the formation of
protein-
protein interactions critical to many signal transduction cascades. Little is known, however, about how synthetic SH2 domain
ligands would influence the growth properties of
tumor cells or with which intracellular
proteins they would interact due to their highly charged nature and enzymatic lability. In this study, a
prodrug delivery strategy was used to introduce an enzymatically stable,
phosphotyrosine peptidomimetic into
tumor cells. When tested in a human
tumor cell panel, the
prodrug exhibited a preference for inhibiting the growth of
leukemia and
lymphoma cells. In these cells, it was largely
cytostatic and induced endoreduplication and the appearance of midbodies. Proteomic analyses identified multiple targets that included mitotic centromere-associated
kinesin (MCAK). Molecular modeling studies suggested the
ATP-binding site on MCAK as the likely site of drug interaction. Consistent with this,
ATP inhibited the
drug-MCAK interaction and the
drug inhibited MCAK
ATPase activity. Accordingly, the effects of the
prodrug on the assembly of the mitotic spindle and alignment of chromosomes were consistent with the identification of MCAK as an important intracellular target.