Discovery of inner centromere protein-derived small peptides for cancer
imaging and treatment targeting survivin
ABSTRACT
Survivin belongs to the inhibitor of apoptosis protein family, which is
consistently overexpressed in most cancer cells but rarely expressed in
normal adult tissues. Therefore, the detection and inhibition of survivin
are regarded as attractive strategies for cancer-specific treatment. In
this study, we designed and synthesized 7-19 residues of inner centromere
protein (INCENP)-derived small peptides (INC peptides) as novel survivin-targeting
agents. The INC peptides showed binding affinity for the human survivin
protein (Kd = 91.4-255 nmol L−1); INC16-22, which contains residues 16-22
of INCENP, showed the highest affinity (91.4 nmol L−1). Confocal fluorescence
imaging showed consistent colocalization of FITC-INC16-22 and survivin
in cell lines. Nona-arginine-linked INC16-22 (r9-INC16-22) rendered INC16-22
cells penetrable and strongly inhibited cell growth of MIA PaCa-2 cells
(52% inhibition at 1.0 µmol L−1) and MDA-MB-231 cells (60% inhibition at
10 µmol L−1) as determined by MTT assays. The exposure of MIA PaCa-2 cells
to 40 µmol L−1 r9-INC16-22 apparently reduced the intracellular protein
expression levels of survivin. However, cleaved caspase-3 was significantly
increased in cells treated with r9-INC16-22, even at 10 µmol L−1, compared
to untreated cells. Flow cytometry revealed that r9-INC16-22 strongly induced
apoptosis in MIA PaCa-2 cells. These results indicate that the cytotoxic
effects of r9-INC16-22 could be mediated mainly through the disruption
of survivin-dependent antiapoptotic functions and partly because of the
direct degradation of the survivin protein. Our findings suggest that INC
peptides can act as useful scaffolds for novel cancer imaging and anticancer
agents.