Drug resistance is one of the most important obstacles in effective
cancer therapy triggered through various mechanisms. One of these mechanisms is caused by the upregulation of
Inhibitor of Apoptosis Proteins (IAPs). IAPs, inhibit apoptosis through direct and/or indirect
caspase inhibition, which themselves are antagonized by an endogenous
protein called Second Mitochondrial-derived Activator of
Caspases, Smac/Diablo, mediated by the presence of a tetrapeptide IAP binding motif at its N-terminus. Accordingly, Smac-based
peptides are under intense investigation as anti-
cancer drugs and have reached Phase 2 clinical trials, although, Smac based
peptides or mimetics alone have not been effective as anti-
cancer agents. On the other hand,
KLA peptide has shown major toxicity against
cancer cells through the induction of apoptosis. Consequently, we designed an anti-
cancer chimera by fusing an octa-
peptide from the N-terminus of mature Smac
protein to a modified proapoptotic
KLA peptide (KLAKLCKKLAKLCK) to be called Smac-KLA. This chimera, therefore, possesses both proapoptotic and anti-IAP activities. In addition, we dimerized this chimera via intermolecular
disulfide bonds in order to enhance their cellular permeability. Both the Smac-KLA monomeric and dimeric
peptides exhibited cytotoxic activity against both MCF-7 and MDA-MB231
breast cancer cell lines at low micromolar concentrations. Importantly, the dimerization of the chimeras enhanced their potency 2-4- fold due to higher cellular uptake.