Determination of cyclin B mRNA and protein levels.

<p>MCF10A, MCF10A/OD, and MCF10A/Δp53 cells were incubated with 0–30 ng/ml SN38 for 24 hours. RNA was purified from cell lysates and relative levels of cyclin B mRNA were analyzed using RT-PCR followed by agarose gel electrophoresis. Cell lysates were also analyzed for expression of cyclin B and actin protein using SDS-PAGE followed by immunoblotting with cyclin B- or actin-specific antibodies.