FIGURE 1.

TMPyP4 induces the formation of G‐quadruplex in vivo and inhibits the ALT activity of osteosarcoma U2OS and SAOS‐2 cells. (A) Immunofluorescence (IF) and fluorescence in situ hybridization (FISH) were used to detect G‐quadruplex or telomeric G‐quadruplex in U2OS cells treated with 10 μmol L^–1 TMPyP4 or 5 μmol L^–1 cisplatin for 48 h. Antibodies against G‐quadruplex and cy3‐labelled telomeric probes were used to visualize the telomeres. Magnification: 400×. (B) and (C) Quantification of A. (D) C‐circle assay in drug‐treated U2OS and SAOS‐2 cells. Cells were treated with 10 μmol L^–1 TMPyP4 or 5 μmol L^–1 cisplatin for 48 h. Ethidium bromide staining (bottom) served as a control for equal loading. E, Quantification of D. (F) IF and FISH was used to detect the formation of ALT‐associated promyelocytic leukaemia (PML) bodies in U2OS cells. Cells were treated with TMPyP4 and cisplatin for 72 h. Antibodies against PML and cy3‐labelled telomeric probes were used to visualize PML bodies and telomeres, respectively. Arrows indicate colocalized foci. Magnification: 400×. (G) and (H) Quantification of F. For each group, 200 or more cells were examined, and values are the average ± SD of three independent experiments. The statistical significance was calculated using the unpaired Student's two‐tailed t test (*p < .05, **p < .01, ***p < .001)