Exemplary results of the immunocytochemical BrdU co-staining in different GB-derived cell cultures.

(A,B) An early passage of cells cultured under the classical monolayer conditions after a 7-day incubation with BrdU. In both cases two populations of cells are detectable: (A) BrdU(+)/EGFR(−)/GFAP(−) and BrdU(−)/EGFR(+)/GFAP(+); (B) BrdU(+)/TP53(−)/GFAP(−) and BrdU(−)/TP53(+)/GFAP(+); (C) An early passage of cells cultured under serum-free conditions after 5-day incubation with BrdU, TP53(+)/GFAP(+) tumor cells are negative for BrdU; (D) A spheroid from the 2nd transfer after a 7-day incubation with BrdU, the majority of cells are BrdU-positive; (E) The cells which invaded radially from the spheroid core (2nd transfer) after a 48-hour incubation with BrdU. The majority of EGFR(+)/GFAP(+) cells incorporated BrdU; (F) The cells which invaded from spherical core after 2 months of culturing. Less than 10% of cells incorporated BrdU (10 days of incubation).