Background: DNA G-quadruplex (G4) structures represent potential anti-cancer targets. In this study, we compared the effect of two G4-targeting compounds, C066-3108 and the gold standard BRACO-19.
Methods: In breast and prostate cancer cells, cytotoxicity induced by both molecules was measured by a sulforhodamine B assay. In breast cancer cells, cycle, apoptosis, the formation of G4 structures, calreticulin and high mobility group box 1 (HMGB1), as well as T cell activation, were analyzed by flow cytometry and adenosine triphosphate (ATP) by luminescence.
Results: Both ligands inhibited cell survival and induced DNA damage. In MCF-7 cells, G4 ligands increased the subG0/G1 phase of the cell cycle inducing apoptosis and reduced intracellular ATP. In untreated MCF-7 cells, we observed a slight presence of G4 structures associated with the G2/M phase. In MDA-MB231 cells, G4 ligands decreased the G1 and enhanced the G2/M phase. We observed a decrease of intracellular ATP, calreticulin cell surface exposure and an increase of HMGB1, accompanied by T cell activation. Both compounds induced G4 structure formation in the subG0/G1 phase.
Conclusions: Our data report similar effects for both compounds and the first evidence that G4 ligands induce the release of danger signals associated with immunogenic cell death and induction of T cell activation.
Keywords: G-quadruplex; T cell activation; breast cancer; immunogenic cell death markers.