Disruption of Stat3 reveals a critical role in both the initiation and the promotion stages of epithelial carcinogenesis
J. Clin. Invest. Keith Syson Chan, et al. 114:720 doi:10.1172/JCI21032 [Go to this article.]

Figure 2
Analysis of cell cycle regulatory proteins in Stat3-deficient mice following treatment with TPA. (A–D) Groups of mice (n = 3) were treated with a single application of 6.8 nmol TPA and sacrificed at various times thereafter, as indicated. BrdU was injected 30 minutes prior to sacrifice. (A) Percentage of BrdU-positive epidermal basal cells in control (solid line) and Stat3-deficient (broken line) mice. (B) Immunohistochemical analysis of p-Stat3 localization in skin sections from Stat3-deficient mice (–/–) and control littermates (+/+) with (lower panels) or without (upper panels) TPA treatment. Positive staining for tyrosine-phosphorylated Stat3 in the nuclei of epidermal keratinocytes is shown by brown staining. Arrows, positive signals found in dermal cells such as fibroblasts and macrophages. Scale bar: 50 μm. (C) Western blot analyses of Stat3 and tyrosine-phosphorylated Stat3 protein levels in relation to levels of cyclin D1, cyclin E, and c-Myc at different time points in control and Stat3-deficient mouse epidermis following TPA treatment. (D) Semiquantitative analysis of the mRNA levels of cyclin D1 and c-Myc without treatment and 4 hours after TPA treatment. (E) Western blot analysis of Erk1/2 and phosphorylated Erk1/2 levels at different time points following TPA treatment in epidermis of control and Stat3-deficient mice.