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. Author manuscript; available in PMC: 2010 Apr 1.
Published in final edited form as: Mol Cancer Res. 2009 Apr;7(4):592–600. doi: 10.1158/1541-7786.MCR-08-0316

FIGURE 1.

FIGURE 1

Constitutive activation of STAT3 in ErbB2 overexpressing cells results in p21Cip1 transcriptional upregulation. A. left, schematic diagram of the 5’ promoter region of the p21 gene. White boxes represent STAT SIE location on promoter; black box represents mutated SIE. right, Luciferase activity of extracts prepared from 435.Vec and 435.ErbB2 cells transfected with the indicated p21Cip1 promoter reporter constructs. Bars indicate luciferase activity standardized to vector control for each construct. Error bars represent standard deviation (S.D.) B. Lysates from SKBR3, along with MDA-MB--435 and MDA-MB-231 breast cancer cells stably transfected with either control vector or wild-type ErbB2 were analyzed by Western blotting with the indicated antibodies. C. Nuclear extracts were collected from ErbB2 stable transfectants and vector control cells and SKBR3 cells for Electrophoretic Mobility Shift Assay (EMSA) analysis. Arrow indicates STAT protein:DNA complexes. Asterisk indicates addition of non-radiolabeled competitor probe. D. Chromatin Immunoprecipitation (ChIP assay) for SIE p21Cip1 promoter sequence using antibodies against histone and STAT3 in ErbB2 overexpressing cells. Histone and IgG immunoprecipitation served as positive and negative controls, respectively. Input represents 10% of the total.