Exploring New Potential Anticancer Activities of the G-Quadruplexes Formed by [(GTG2T(G3T)3] and Its Derivatives with an Abasic Site Replacing Single Thymidine

Abstract

In this paper, we report our investigations on five T30175 analogues, prepared by replacing sequence thymidines with abasic sites (S) one at a time, in comparison to their natural counterpart in order to evaluate their antiproliferative potential and the involvement of the residues not belonging to the central core of stacked guanosines in biological activity. The collected NMR (Nuclear Magnetic Resonance), CD (Circular Dichroism), and PAGE (Polyacrylamide Gel Electrophoresis) data strongly suggest that all of them adopt G-quadruplex (G4) structures strictly similar to that of the parent aptamer with the ability to fold into a dimeric structure composed of two identical G-quadruplexes, each characterized by parallel strands, three all-anti-G-tetrads and four one-thymidine loops (one bulge and three propeller loops). Furthermore, their antiproliferative (MTT assay) and anti-motility (wound healing assay) properties against lung and colorectal cancer cells were tested. Although all of the oligodeoxynucleotides (ODNs) investigated here exhibited anti-proliferative activity, the unmodified T30175 aptamer showed the greatest effect on cell growth, suggesting that both its characteristic folding in dimeric form and its presence in the sequence of all thymidines are crucial elements for antiproliferative activity. This straightforward approach is suitable for understanding the critical requirements of the G-quadruplex structures that affect antiproliferative potential and suggests its application as a starting point to facilitate the reasonable development of G-quadruplexes with improved anticancer properties.

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

“…In their paper, Bates et al described the physical and biological properties of a collection of 12 G4 oligonucleotides, whose structures have formerly been described in depth, and among them T30695 has been proven to possess an intermediate antiproliferative activity on HeLa cervical carcinoma cells that was not very different between NaCl and KCl buffers [ 2 ]. Similar G-rich oligonucleotides, namely EAD [T 2 (TG 3 ) 4 ] [ 27 ], ODN S13 [(TG 3 ) 3 G 3 ] [ 28 ], and recently the covalent bi-modular version of the sequence [G 3 (TG 3 ) 3 ] [ 29 ] and T30175 [GTG 2 (TG 3 ) 3 T] [ 30 ] have been shown to have interesting antiproliferative properties against different cancer cell lines. The G4-aptamer T30923 was also tested for its capability to inhibit Stat3, whose activation has been proven to have an effect on multiple cell fate decisions including proliferation, apoptosis, and differentiation in human cancer cells [ 24 ].…”

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

“…Although all TBA derivatives show an antiproliferative activity to the same extent, the most interesting data concern the results obtained from MDAMB 231 cells, which indicate a noteworthy activity for TBA, TBAG3, TBAG4, and TBAG4GS, revealing a reduction in cell viability percentage in the range 20–45%. 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 ].…”

Changes in physicochemical and anticancer properties modulated by chemically modified sugar moieties within sequence-related G-quadruplex structures

“…Nuclease stability assay can offer information about the inherent enzymatic stability of oligonucleotides providing valuable instructions for the G-quadruplex design [ 9 , 11 , 39 ]. The investigations of stability of all studied G-quadruplex variants were performed by CD spectroscopy in RPMI medium supplemented with 10% FBS and the degradation tendency was analyzed at time 0 and after 24h of incubation at 37°C.…”