Enhanced G-Quadruplex Stability and Anticancer Activity of N2-Aryl Deoxyguanosine-Modified T40214 Oligonucleotides Targeting STAT3 in Prostate Cancer.

Signal transducer and activator of transcription 3 (Stat3) is a key molecular target in many cancers due to its role in tumor cell proliferation and survival. T40214, a G-quadruplex (G4) forming oligonucleotide, targets the Stat3 dimer and inhibits its DNA binding activity. In this study, we introduced N2-furfuryl and N2-cinnamyl deoxyguanosine modifications at the G-tetrad positions in T40214 to assess their structural and antitumor effects in prostate cancer cells. A single N2-furfuryl/cinnamyl modification preserved the stable parallel G4 conformation. Incorporating either of these modifications into the top G-quartet (TF15 and TC15) significantly enhanced thermal stability. Molecular dynamics simulation studies revealed that the aryl moieties were well accommodated at the 5'-ends without disrupting the interaction with Stat3. It is also evident that H-bonding and π-π stacking interactions induced due to the presence of the aryl moieties contributed to the improved thermal stabilities for TF15 and TC15, respectively. Gel mobility assays confirmed that all aryl-modified T40214 G4s form stable 5'-5' dimers, similar to native T40214. TF15 and TC15 derivatives exhibited potent antiproliferative activity (IC50 = 0.37-0.39 μM) and effectively induced apoptosis while suppressing the Stat3-mediated gene expressions in DU145 cells. Overall, these findings demonstrate the potential of these aryl modifications in T40214 as a promising Stat3-targeting therapeutic approach for prostate cancers.