Fig. 4.

Transformation of miR-21-null MEFs with or without p53. (A) A focus formation assay of MEFs transformed with Ras activation. Low passages of MEFs were transduced with a virus carrying H-ras^V12. Foci were stained after 21 days of growth. (B) Bar graphs of cell transformation from (A). (C) Cell proliferation of Trp53 ^−/− and Trp53 ^−/− miR-21 ^−/− MEFs transformed by Ras activation. (D) Apoptosis analysis of Trp53 ^−/− and Trp53 ^−/− miR-21 ^−/− MEFs transformed with Ras were treated with doxorubicin. Apoptotic cells were analyzed by TUNEL assay and counted by microscopy. **P < 0.01.