l-Glutamate and its receptors (GluRs) play a key role in excitatory neurotransmission within the mammalian central nervous system (CNS). Impaired regulation of GluRs has also been implicated in various neurological disorders. GluRs are classified into two major groups: ionotropic GluRs (iGluRs), which are ligand-gated ion channels, and metabotropic GluRs (mGluRs), which are coupled to heterotrimeric guanosine nucleotide binding proteins (G-proteins). Positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging of GluRs could provide a novel view of CNS function and of a range of brain disorders, potentially leading to the development of new drug therapies. Although no satisfactory imaging agents have yet been developed for iGluRs, several PET ligands for mGluRs have been successfully employed in clinical studies. This paper reviews current progress towards the development of PET and SPECT probes for GluRs.

Prion diseases are fatal neurodegenerative diseases characterised by deposition of amyloid plaques containing abnormal prion protein aggregates (PrPSc). This study aimed to evaluate the potential of radioiodinated flavonoid derivatives for single photon emission computed tomography (SPECT) imaging of PrPSc. In vitro binding assays using recombinant mouse PrP (rMoPrP) aggregates revealed that the 4-dimethylamino-substituted styrylchromone derivative (SC-NMe2) had higher in vitro binding affinity (Kd = 24.5 nM) and capacity (Bmax = 36.3 pmol/nmol protein) than three other flavonoid derivatives (flavone, chalcone, and aurone). Fluorescent imaging using brain sections from mouse-adapted bovine spongiform encephalopathy (mBSE)-infected mice demonstrated that SC-NMe2 clearly labelled PrPSc-positive prion deposits in the mice brain. Two methoxy SC derivatives, SC-OMe and SC-(OMe)2, also showed high binding affinity for rMoPrP aggregates with Ki values of 20.8 and 26.6 nM, respectively. In vitro fluorescence and autoradiography experiments demonstrated high accumulation of [125I]SC-OMe and [125I]SC-(OMe)2 in prion deposit-rich regions of the mBSE-infected mouse brain. SPECT/computed tomography (CT) imaging and ex vivo autoradiography demonstrated that [123I]SC-OMe showed consistent brain distribution with the presence of PrPSc deposits in the mBSE-infected mice brain. In conclusion, [123I]SC-OMe appears a promising SPECT radioligand for monitoring prion deposit levels in the living brain.

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 (K d = 91.4-255 nmol L −1 ); INC 16-22 , which contains residues 16-22 of INCENP, showed the highest affinity (91.4 nmol L −1 ). Confocal fluorescence imaging showed consistent colocalization of FITC-INC 16-22 and survivin in cell lines. Nona-arginine-linked INC 16-22 (r9-INC 16-22 ) rendered INC 16-22 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-INC 16-22 apparently reduced the intracellular protein expression levels of survivin. However, cleaved caspase-3 was significantly increased in cells treated with r9-INC 16-22 , even at 10 µmol L −1 , compared to untreated cells. Flow cytometry revealed that r9-INC 16-22 strongly induced apoptosis in MIA PaCa-2 cells. These results indicate that the cytotoxic effects of r9-INC 16-22 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. K E Y W O R D S anticancer, apoptosis, cancer imaging, peptide, survivin 1 | INTRODUC TI ON Survivin, the smallest protein (16.5 kDa) among the inhibitor of apoptosis protein (IAP) family, is one of the most cancer-specific proteins 1,2 ; it is highly overexpressed in most cancers, but barely detected in the majority of normal cells. 3-6 Survivin is involved in at least 2 essential cellular processes, inhibition of apoptosis and regulation of the cell cycle. 5 Furthermore, it participates in another antiapoptotic effect by S U PP O RTI N G I N FO R M ATI O N Additional supporting information may be found online in the Supporting Information section. How to cite this article: Fuchigami T, Ishikawa N, Nozaki I, et al. Discovery of inner centromere protein-derived small peptides for cancer imaging and treatment targeting survivin.

We report here the development of radioiodinated styrylchromone derivatives with alkoxy groups as single photon emission computed tomography (SPECT) imaging probes for cerebral amyloid-β (Aβ) plaques. Among the derivatives, the methoxy derivative 14 and the dimethoxy derivative 15 displayed relatively high affinity for the Aβ(1-42) aggregates with K(i) values of 22 and 46 nM, respectively. Fluorescent imaging demonstrated that 14 and 15 clearly labeled thioflavin-S positive Aβ plaques in the brain sections of Tg2576 transgenic mice. In the in vivo studies, [(125)I]14 and [(125)I]15 showed high initial brain uptake expressed as the percentage of the injected dose per gram (2.25% and 2.49% ID/g at 2 min, respectively) with favorable clearance (0.12% and 0.20% ID/g at 180 min, respectively) from the brain tissue of normal mice. Furthermore, in vitro autoradiography confirmed that [(125)I]15 binds thioflavin-S positive regions in Tg2576 mouse brain sections. The derivative 15 may be a potential scaffold for the development of in vivo imaging probes targeting Aβ plaques in the brain. In particular, further structural modifications are required to improve the compounds binding affinity for Aβ.

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