Intracellular targets for a phosphotyrosine peptidomimetic include the mitotic kinesin, MCAK

Abstract

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.

Prodrugs of Phosphonates and Phosphates: Crossing the Membrane Barrier

“…The compounds exhibit low micromolar growth inhibition in Jurkat T cells, and undergo spontaneous hydrolysis with half-lives of approximately 30 minutes. The same masking groups have been applied in phosphonate 100 as a suspected SH2 domain blocker through inhibition of mitotic centromere-associated kinesin protein function in a panel of cell lines [225]. The compound inhibited cell growth but surprisingly the growth inhibition was not restricted to Src-dependent cells.…”

MCAK Inhibitors Induce Aneuploidy in Triple-Negative Breast Cancer Models

“…While MCAK has been examined as a putative prognostic marker for multiple cancers [ 36 ], there has been little effort focused on developing tools to probe MCAK function or that could be developed into clinical effectors. A prodrug was identified and shown to target MCAK and induce spindle defects consistent with MCAK inhibition, but this compound was non-specific and bound to multiple targets in addition to MCAK [ 82 ]. The small molecule DHTP was identified as a non-competitive inhibitor of Kinesin-13, which inhibited the ATPase activity of the Kinesin-13s, MCAK and Kif2A, with a three-to-four-fold increase in specificity for MCAK over Kif2A [ 83 ].…”

MCAK Inhibitors Induce Aneuploidy in Triple Negative Breast Cancer Models

“…While MCAK has been examined as a putative prognostic marker for multiple cancers [36], there has been little effort focused on developing tools to probe MCAK function or that could be developed into clinical effectors. A prodrug was identified and shown to target MCAK and induce spindle defects consistent with MCAK inhibition, but this compound was non-specific and bound to multiple targets in addition to MCAK [82]. The small molecule DHTP was identified as a non-competitive inhibitor of Kinesin-13, which inhibited the ATPase activity of the Kinesin-13s, MCAK and Kif2A with a three-to-fourfold increase in specificity for MCAK over Kif2A [83].…”