Figure 1.

Genotoxic stress induces the emergence of a cell population that resembles CSCs. (a) Flow cytometry analysis of RPMI 8226 cells 7 days after X-irradiation (0–6 Gy) and 2 days after doxorubicin treatment (0–50 nM) are presented on the left (P=0.014) and on the right (P=0.0011), respectively. (b) QRT-PCR analysis of BCL6 and PAX5 gene expressions of CD138-sorted RPMI 8226 cells and RPMI 8226 cells 7 days after X-irradiation (6 Gy) and 2 days after doxorubicin treatment (50 nM); the untreated main population served as reference. (c) RPMI 8226 cells were seeded in methylcellulose 7 days after X-ray treatment (6 Gy) or control (0 Gy) and the number of colonies was quantified after the first, second and third replating. (d) At 7 days after X-ray treatment, 10⁴ irradiated (6 Gy) or control (0 Gy) RPMI 8226 cells were injected subcutaneously into five nude mice per series. The graphic illustrates the number of mice bearing tumors 12 weeks post-injection. Tumors were stained with hematoxylin or labeled with anti-CD138 antibody. Images were taken at × 40 magnification. Data are means±S.D. from at least three independent experiments; *P<0.05; a.u., arbitrary unit