Backbone modified TBA analogues endowed with antiproliferative activity

Background: Thrombin binding aptamer (TBA) is endowed with antiproliferative properties but its potential development is counteracted by concomitant anticoagulant activity. Methods: Five oligonucleotides (ODNs) based on TBA sequence (GGTTGGTGTGGTTGG) and containing L-residues or both L-residues and inversion of polarity sites have been investigated by NMR and CD techniques for their ability to form G-quadruplex structures. Furthermore, their anticoagulant (PT assay) and antiproliferative properties (MTT assay), and their resistance in fetal bovine serum have been tested. Results: CD and NMR data suggest that investigated ODNs are able to form right- and left-handed G-quadruplex structures. All ODNs do not retain anticoagulant activity characteristic of TBA but are endowed with a significant antiproliferative activity against two cancerous cell lines. Their resistance in biological environment after six days is variable, depending on ODN. Conclusions: A comparison between results and literature data suggests that antiproliferative activity of TBA analogues investigated could depends on two factors: a) biological pathways and targets different from those already identified or proposed for other antiproliferative G-quadruplex aptamers, and b) contribution of the guanine-based degradation products. General significance: Modified TBA analogues containing L-residues and inversion of polarity sites lose the anticoagulant activity but gain antiproliferative properties against two cancer cell lines.