Antiproliferative Effects of the Aptamer d(GGGT)4 and Its Analogues with an Abasic-Site Mimic Loop on Different Cancer Cells

Abstract

In this paper, we study the T30923 antiproliferative potential and the contribution of its loop residues in six different human cancer cell lines by preparing five T30923 variants using the single residue replacement approach of loop thymidine with an abasic site mimic (S). G-rich oligonucleotides (GRO) show interesting anticancer properties because of their capability to adopt G-quadruplex structures (G4s), such as the G4 HIV-1 integrase inhibitor T30923. Considering the multi-targeted effects of G4-aptamers and the limited number of cancer cell lines tested, particularly for T30923, it should be important to find a suitable tumor line, in addition to considering that the effects also strictly depend on G4s. CD, NMR and non-denaturating polyacrylamide gel electrophoresis data clearly show that all modified ODNs closely resemble the dimeric structure of parallel G4s’ parent aptamer, keeping the resistance in biological environments substantially unchanged, as shown by nuclease stability assay. The antiproliferative effects of T30923 and its variants are tried in vitro by MTT assays, showing interesting cytotoxic activity, depending on time and dose, for all G4s, especially in MDA-MB-231 cells with a reduction in cell viability approximately up to 30%. Among all derivatives, QS12 results are the most promising, showing more pronounced cytotoxic effects both in MDA-MB-231 and Hela cells, with a decrease in cell viability from 70% to 60%. In summary, the single loop residue S substitution approach may be useful for designing antiproliferative G4s, considering that most of them, characterized by single residue loops, may be able to bind different targets in several cancer cell pathways. Generally, this approach could be of benefit by revealing some minimal functional structures, stimulating further studies aimed at the development of novel anticancer drugs.

Properties and Potential Antiproliferative Activity of Thrombin-Binding Aptamer (TBA) Derivatives with One or Two Additional G-Tetrads

“…Concerning TBAG3, it should be noted that it folds in a parallel G4-structure with three G-tetrads and three propeller loops, which is very similar to that adopted by other antiproliferative G-quadruplexes [ 25 , 26 ]. It is well known that TBA is highly susceptible to nucleases being degraded in a few hours [ 27 ], as also reported by us ( Figure S3 ) [ 27 ]. Outcomes concerning the nuclease stability assay have indicated that all TBA derivatives significantly degrade in 72 h in serum, except TBAG4, which preserves its structure up to 72 h. It is interesting to note that there is a rough correlation between the degradability order (TBA < TBAG3 < TBAG41S ≤ TBAG4GS) and the antiproliferative activities in MDAMB 231 cells at 72 h (TBA < TBAG3 < TBAG4GS ≤ TBAG41S).…”

GQIcombi application to subdue glioma via differentiation therapy

“…Aptamers, synthetic oligonucleotides, can be antiproliferative agents with benefits including size, flexibility, rapid production, stability, and low immunogenicity ( 20 ). Cytostatic G-quadruplex (GQ) oligonucleotides have been effective on glioma cell cultures ( 21 ), showing promise in this context ( 22 , 23 ).…”

DataSheet_1.pdf

“…Aptamers, synthetic oligonucleotides, can be antiproliferative agents with benefits including size, flexibility, rapid production, stability, and low immunogenicity (20). Cytostatic G-quadruplex (GQ) oligonucleotides have been effective on glioma cell cultures (21), showing promise in this context (22,23).…”