Strain-specific differences in formation of apoptotic DNA ladders in MCF-7breast cancer cells

We tested the ability of seven MCF-7 strains to undergo DNA fragmentation, as measured by DNA laddering, following doxorubicin-induced apoptosis. Four strains were found to undergo DNA laddering while three were not. All stra ins were inhibited by doxorubicin, although sensitivity differed. Finally, we show by detection of sub-G1 DNA that doxorubicin induced the same: fold increase in apoptosis in MCF-7-ATCC, which did not ladder, and MCF-7-MG, wh ich did ladder. Therefore, detection of DNA ladders is not an accurate indi cator of apoptosis in MCF-7 cells as fragmentation of DNA appears to vary b etween strains. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.