G4 Matters—The Influence of G-Quadruplex Structural Elements on the Antiproliferative Properties of G-Rich Oligonucleotides

Abstract

G-quadruplexes (G4s) are non-canonical structures formed by guanine-rich sequences of DNA or RNA that have attracted increased attention as anticancer agents. This systematic study aimed to investigate the anticancer potential of five G4-forming, sequence-related DNA molecules in terms of their thermodynamic and structural properties, biostability and cellular uptake. The antiproliferative studies revealed that less thermodynamically stable G4s with three G-tetrads in the core and longer loops are more predisposed to effectively inhibit cancer cell growth. By contrast, highly structured G4s with an extended core containing four G-tetrads and longer loops are characterized by more efficient cellular uptake and improved biostability. Various analyses have indicated that the G4 structural elements are intrinsic to the biological activity of these molecules. Importantly, the structural requirements are different for efficient cancer cell line inhibition and favorable G4 cellular uptake. Thus, the ultimate antiproliferative potential of G4s is a net result of the specific balance among the structural features that are favorable for efficient uptake and those that increase the inhibitory activity of the studied molecules. Understanding the G4 structural features and their role in the biological activity of G-rich molecules might facilitate the development of novel, more potent G4-based therapeutics with unprecedented anticancer properties.

Evaluation of Gene Expression Knock‐Down by Chemically and Structurally Modified Gapmer Antisense Oligonucleotides

“…Comparing all the hairpin gapmers with the control gapmer, only in one case ( ON16 ), the β‐actin silencing level was worse. Increasing the efficiency of gapmers may be the result of greater stability of these oligonucleotides in the cell or such structured gapmers might better pass through cellular compartments [25] . Presumably, decreased effectiveness of ON16 in comparison to other hairpin forming gapmers is due to the highest thermodynamic stability of this structure among the group and thus lower ability to unfold process prior to interactions with mRNA target.…”

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

“…Remarkably, at 50 µM and after 72 h of treatment, INT-B resulted in a reduction of 90% of cell viability (Figure 6B-D). Recently, some authors have highlighted the influence of G-quadruplex structural elements on the antiproliferative properties of certain G-rich oligonucleotides [40]. In our case, it is interesting to note that in both cell lines, the most significant antiproliferative results were related to INT-B, the unique ODN characterized by an intact dimeric G-quadruplex structure, suggesting that both its typical folding in dimeric form and the presence of all thymidines in the sequence are pivotal features for this biological activity.…”

A Comprehensive Analysis of the Thrombin Binding Aptamer Containing Functionalized Pyrrolo-2’-deoxycytidines

“…Recently, the attention of many research groups has focused on the antiproliferative potential of guanosine-rich oligonucleotides. These molecules are usually G-quadruplexes that are able to interact specifically with proteins involved in the cell cycle, which could restrain cell proliferation [43][44][45]. What is more, it has also been demonstrated that some modified TBA variants with decreased anticoagulant properties are characterized by favorable antiproliferative activity [21,31].…”