MST312 targets ALDH+ cells in vivo and reduces their telomere length. A and B: FACS analysis and quantification of dissociated tumors confirms, along with the immunhistochemical results, a decrease in ALDH+ cells in vivo after treatment with MST312. C: Quantification of telomeric length in ALDH+ cells present in tumors from treated and untreated mice. A significant reduction is found in mice administered with the antitelomeric therapy (p < 0.05). ALDH negative cells from the tumor bulk could not be accurately quantified due to massive necrosis. D: Representative FICTION image using probes for telomeres (red), immunofluorescence for ALDH (green), and nuclear staining (DAPI, in blue). Images show a lower intensity for telomeres in MST312-treated mice. The "M" labeled cell represents a murine fibroblast excluded from the analysis (small nuclei and longer telomeres).