Human cancer cell lines growth inhibition by GT_n oligodeoxyribonucleotides recognizing single‐stranded DNA‐binding proteins

Abstract

Oligonucleotides can specifically target not only nucleic acids but also proteins. Some proteins recognizing oligonucleotides in a sequence-specific manner have been related to cancer transformation and progression. We have found that oligonucleotides composed by repeated and/or variable intervals of GT n with 1 р n р 7, are able to exert a specific and dose-dependent growth inhibition on human CCRF-CEM, CEM-VLB300, U937, Jurkat, H9 and HeLa tumor cell lines. In contrast, G→C, G→A, T→C and T→A base substituted control oligonucleotides do not significantly alter cellular growth. In all cell lines, a nuclear protein (molecular mass ϭ 45Ϯ7 kDa), which specifically recognizes GT n, was identified. Our hypothesis is that the formation of the GT n -protein complex in human cancer cell lines may be involved in the growth inhibition effect. In fact, we found that the reduction or lack of cytotoxic effects by GT n in phorbol 12-myristate 13-acetate-treated CCRF-CEM cells and in normal human lymphocytes is paralleled by the simultaneous reduction or lack of GT n -protein complex. Oligonucleotides specifically 'quenching' intracellular protein activities by forming oligonucleotide-protein complexes may be of potential interest in the treatment of human tumors.

Antiproliferative Activity of G-rich Oligonucleotides Correlates with Protein Binding

“…These include binding to cellular receptors (54,55), modulation of cytokine or growth factor activity (56 -60), inhibition of cell cycle progression (9), changes in cell adhesion (12), and binding to an uncharacterized 45-kDa protein (26).…”

“…Although this method may underestimate absolute cellular uptake of oligonucleotide due to the action of phosphomonoesterase in removing the 5Ј-label, it can provide useful information when comparing relative uptake (26,27). Fig.…”

Discovery and development of the G-rich oligonucleotide AS1411 as a novel treatment for cancer

“…In the early days of antisense research, several researchers noted [11-20] that the biological activities of certain oligonucleotides were not due to a true antisense effect, but rather were linked to the presence of contiguous guanines and the propensities of the oligonucleotides to form quadruplex structures containing G-quartets (Figure 2). Subsequently, a number of groups have described various quadruplex-forming and G-rich oligonucleotides that have biological activities that are not mediated by an antisense mechanism, but are most likely attributable to the protein-binding (aptameric) effects of these oligonucleotides [21-61]. While many of these observations were made by chance, aptamers generated using combinatorial methods such as SELEX (systematic evolution of ligands by exponential enrichment) frequently turned out to be capable of forming G-quadruplexes as well [62-74].…”

“…For some oligonucleotides, in vivo antiproliferative effects were also demonstrated in tumor-bearing mice [33,41,45,48,50-53]. For the most part, biologically active G-rich oligonucleotides have been shown to form G-quartet-containing structures, although the role of quadruplex formation is unclear for some [21-24,39,40]. In many cases, antiproliferative effects have been found to correlate with protein-binding properties [21-25,37,38,56], but specific targets have been identified for only a few.…”

“…For the most part, biologically active G-rich oligonucleotides have been shown to form G-quartet-containing structures, although the role of quadruplex formation is unclear for some [21-24,39,40]. In many cases, antiproliferative effects have been found to correlate with protein-binding properties [21-25,37,38,56], but specific targets have been identified for only a few. Proteins reported as direct targets for G-rich aptamer oligonucleotides with unexpected biological activity ( i.e.…”