Fig. 4. IFN- induces increased p21 transcription in MCF-7 cells but not in MDA-MB-231 cells. RNA from MCF-7 and MDA-MB-231 cells treated with and without 10 ng/ml IFN- was collected, and p21 mRNA expression was detected by RNase protection assay. RNA from A431 cells treated with and without 30 ng/ml EGF was included as a positive control. Hybridization to labeled probe representing 36B4 was used as a loading control. p21 message was quantitated, and values for p21 divided by 36B4 are depicted as a bar graph. Data shown are representative of three independent experiments.