Tumor cell migration is inhibited by a novel therapeutic strategy antagonizing the alpha-7 receptor.

A 14mer peptide (T14) derived from the C-terminus of acetylcholinesterase (AChE) selectively activates metastatic breast cancer cells via the alpha-7 nicotinic receptor (α7 nAChR). This naturally occurring peptide is also present in brain, is elevated in Alzheimer's disease, and is antagonised by a cyclized variant (NBP-14). Here we investigated the effects of NBP-14 in six different cancer cell lines, primary leukemia B-cells and normal B-cells. All cells tested expressed α7 nAChR, intracellular and extracellular T14. However, NBP-14 showed low toxicity and weak anti-proliferative effects in the majority of the cell lines and was even less toxic in normal B-cells when compared to primary chronic lymphocytic leukemia cells (P < 0.001). Given the potential role of T14 peptide in metastasis, we next investigated the effects of NBP-14 on tumor cell migration, where it caused a dose-dependent reduction. The extent of NBP-14 inhibition positively correlated with the migration of the cells (r2 = 0.45; P = 0.06). Furthermore, NBP-14 preferentially inhibited the migration of primary leukemia cells when compared with normal B-cells (P = 0.0002); when the normal B-cell data was excluded, this correlation was strengthened (r2 = 0.80; P = 0.006). Importantly, the constitutive α7 nAChR expression positively correlated with intracellular T14 levels (r2 = 0.91; P = 0.0003) and inversely correlated with extracellular T14 levels in the cell culture supernatants (r2 = -0.79; P = 0.034). However, in the presence of NBP-14, α7 nAChR expression was reduced (P = 0.04) and the most migratory cells showed the largest reduction in expression. In conclusion, NBP-14-mediated antagonism of the α7 nAChR offers a novel therapeutic strategy with the potential to inhibit tumor cell migration.

(I) Pharmacological profiling of a novel modulator of the α7 nicotinic receptor: Blockade of a toxic acetylcholinesterase-derived peptide increased in Alzheimer brains.

The primary cause of Alzheimer's disease is unlikely to be the much studied markers amyloid beta or tau. Their widespread distribution throughout the brain does not account for the specific identity and deep subcortical location of the primarily vulnerable neurons. Moreover an unusual and intriguing feature of these neurons is that, despite their diverse transmitters, they all contain acetylcholinesterase. Here we show for the first time that (1) a peptide derived from acetylcholinesterase, with independent trophic functions that turn toxic in maturity, is significantly raised in the Alzheimer midbrain and cerebrospinal fluid; (2) a synthetic version of this peptide enhances calcium influx and eventual production of amyloid beta and tau phosphorylation via an allosteric site on the α7 nicotinic receptor; (3) a synthetic cyclic version of this peptide is neuroprotective against the toxicity not only of its linear counterpart but also of amyloid beta, thereby opening up the prospect of a novel therapeutic approach.

SUMO-1 conjugation blocks beta-amyloid-induced astrocyte reactivity.

Astrocyte reactivity is implicated in the neuronal loss underlying Alzheimer's disease. Curcumin has been shown to reduce astrocyte reactivity, though the exact pathways underlying these effects are incompletely understood. Here we investigated the role of the small ubiquitin-like modifier (SUMO) conjugation in mediating this effect of curcumin. In beta-amyloid (Aß)-treated astrocytes, morphological changes and increased glial fibrillary acidic protein (GFAP) confirmed reactivity, which was accompanied by c-jun N-terminal kinase activation. Moreover, the levels of SUMO-1 conjugated proteins, as well as the conjugating enzyme, Ubc9, were decreased, with concomitant treatment with curcumin preventing these effects. Increasing SUMOylation in astrocytes, by over-expression of constitutively active SUMO-1, but not its inactive mutant, abrogated Aß-induced increase in GFAP, suggesting astrocytes require SUMO-1 conjugation to remain non-reactive.