Figure 7.

Apoptotic priming of spheroids increases with elevated Bim expression. (a) Spheroids grown from M28, VAMT, REN and SARC cell lines were treated with R8-Noxa^BH3 (50 μM), ABT-737 (1 μM), bortezomib (25 nM) or their combination for 24 h. Whereas R8-Noxa^BH3 alone failed to induce apoptosis in M28 spheroids, ABT-737 alone induced apoptosis in the spheroids generated from all four cell lines. Nevertheless, when given with bortezomib, either R8-Noxa^BH3 or ABT-737 was effective in increasing apoptosis of spheroids. (^*P<0.05 compared with untreated spheroids, ^**P<0.05 compared with bortezomib alone, n=3). (b) Immunoblot analysis of Bim expression in M28, REN, SARC and VAMT monolayers and spheroids with densitometry shown for Bim, standardized for α-tubulin expression. Immunoblot and densitometry values are representative of three separate experiments. In all four cell lines, spheroids expressed increased Bim levels. Compared with monolayers, spheroids of M28 displayed a 1.9-fold increase in Bim levels whereas spheroids of REN, SARC and VAMT showed a 4.5-, 3.2- and 4.0-fold, increase, respectively