Background: G-quadruplex (G4s) are non-canonical nucleic acid structures, which destabilization in telomeric DNA can promote telomerase activity, leading to DNA damage and enhanced proliferative activity. Cigarette smoke (CS) is a well-known risk factor for lung cancer, affecting both innate and adaptive lung immune cells, including macrophages. However, the effect of CS on G4s has not yet been explored.

Aims: To investigate the potential correlation between CS and G4s levels in a vitro model of macrophages through RHPS4, a high specificity telomeric G4 molecule, that showed G4 stabilizing properties.

Methods: RHPS4 antiproliferative activity and IC50 were assessed in PMA-differentiated THP-1 cells using MTT assay. G4s structures in CS-exposed macrophages were detected using high-affinity BG4 antibody and nuclear G4s signal were analyzed using Fiji software. Moreover, we are currently investigating the ability of CS to induce 8-oxoguanine levels and telomeric localization of G4s by rt-PCR and FISH staining.

Results: RHPS4 treatment showed antiproliferative activity in a dose-dependent manner, with an IC50 of 30,91 nM. CS significantly reduced the nuclei G4 foci compared to the control group (p<0.0001), indicating its ability to destabilize G4s, whereas both 100nM and 1uM RHPS4 treatment showed the capacity of restoring the G4s stability (p<0.0001 respectively).

Conclusions: Our results provide new insights into the innate immune mechanisms by which CS promotes tumorigenesis. Ongoing evaluations on the correlation between CS and telomerase activity could pave the way for future studies focused on G4s as a novel promising target for lung cancer treatment.

Ref: PMID 28225080