Figure 8: Myc inhibition decreases the growth of patient-derived neurospheres in vitro and increases the survival of a xenograft mouse model.

(a) Patient-derived neurosphere cultures derived from a resected human glioblastoma were infected with a lentiviral vector harbouring a doxycycline-regulatable Omomyc expression cassette. Myc inhibition by Omomyc decreases the number of spheres after 2 weeks of doxycycline treatment in culture. The mean+s.e.m. is shown (n=6). P-values were calculated by a Student’s t-test. (b) Omomyc expression in disaggregated neurospheres decreases their self-renewal ability. Neurospheres were dissociated into a single-cell suspension and 500 cells per well were added to a 96-well plate. The number of spheres was counted after 2–4 weeks in the presence or absence of doxycycline. The mean+s.e.m. is shown (n=5). P-values were calculated by a Student’s t-test. (c) A Kaplan–Meier survival curve of mice inoculated with patient-derived neurospheres and treated with doxycycline to trigger Omomyc expression (n=6), or with sucrose as the control (n=6). P=0.04 by log-rank test. (d) Omomyc expression increases the number of aberrant nuclei in nestin-positive cells. At the time of euthanasia, brains of the orthotopically injected mice described in 8c were fixed, and sections stained for nestin. Typical images are shown (green: nestin, pink: Hoechst). (e) Quantification of the experiment described in 8d. Five sections taken from different parts of each brain were used to score the number of aberrant nestin-positive nuclei (indicated by arrowheads). Untreated mice n=4, treated with doxycycline n=5. P-values were calculated by a Student’s t-test.