Fig. 8. Transfected p21 is expressed in MDA-MB-231 cells and inhibits foci formation. A, MDA-MB-231 and MCF-7 cells were transfected with p21 or vector alone (pCDNA3.1), and lysates were collected, separated by SDS-PAGE, and immunoblotted for p21. B, MDA-MB-231 and MCF-7 cells were transfected with p21 or vector alone and then selected with neomycin for 3 weeks. The resulting foci were stained with 1% crystal violet and counted. Asterisks represent statistically significant differences due to p21 (P < 0.05).