12th World Cancer Conference
University of Illinois College of Medicine Rockford, USA
Title: Mechanism of Action of G-quadruplex forming oligonucleotide homologous to the telomere overhang in melanoma
Biography: Neelu Puri
T-oligo, a guanine-rich oligonucleotide (GRO) homologous to the 3’-telomeric overhang of telomeres, elicits potent DNA-damage responses (DDRs) in cancer cells. However, the detailed molecular mechanism of action of T-oligo in cancer cells is largely unknown. Recent studies suggest that GROs can form G-quadruplexes (G4) which are stabilized by the hydrogen-bonding of guanine residues. This study aims to examine the G4-forming capabilities of T-oligo in vitro and comparative analysis of anti-proliferative activities of single-stranded (SS) and G4-T-oligo with investigating the molecular mechanism of T-oligo-induced DDRs in melanoma cells. G4-formation by T-oligo was confirmed using non-denaturing PAGE and NMR. Immunofluorescence study conducted with an anti-G-quadruplex antibody (BG4) showed 88.4% co-localization of T-oligo and BG4 in the nuclei of melanoma cells confirming the ability of T-oligo to form G-quadruplex inside the cells. While G4-T-oligo was found more stable in nuclease degradation assay by DNase I, it has decreased anti-proliferative effects then SS-T-oligo. However, G4-T-oligo has similar cellular uptake as SS-T-oligo. Further, two shelterin complex proteins TRF2 and POT1 were found to be upregulated by T-oligo suggesting TRF2 and POT1 mediated telomere overhang dissociation. Activity of JNK was also upregulated by T-oligo. SP600125 (JNK inhibitor), inhibited T-oligo-mediated JNK-phosphorylation and partially reversed the anti-proliferative activity of T-oligo in melanoma cells. T-oligo also inhibited mRNA expression of hTERT, a catalytic subunit of telomerase. In conclusion, these studies demonstrate that T-oligo can form G-quadruplex and the anti-proliferative mechanism of T-oligo may be mediated through POT1 and TRF2 as well as via JNK-activation inducing hTERT-inhibition in melanoma cells.