Figure 2

PTK6 expression is induced in pre-tumorigenic MMTV-ERBB2 mammary glands and promotes STAT3 activation and proliferation. (a) PTK6 was not expressed in wild-type mouse mammary glands in the mature animals, regardless of the developmental states of the glands (left panel, normal virgin mammary gland; right panel, lactating mammary gland). The brown signal in the center of the glands does not include the epithelial cells and represents background. (b) PTK6 expression is induced by ectopic ERBB2. ERBB2 and PTK6 are coexpressed in epithelial cells of a 5-month-old MMTV-ERBB2 PTK6 transgenic mouse. (c) Proliferation is impaired in MMTV-ERBB2-positive mammary glands following disruption of Ptk6. Proliferation in pre-tumorigenic mammary gland epithelial cells was examined by Ki-67 staining. Each panel represents a different animal. (d) Proliferation in mammary gland epithelial cells was quantified by normalizing Ki-67-positive epithelial cells to the total number of epithelial cells. Each group contains five animals, and five different random views were counted per animal. The difference in percent of Ki67-positive cells in B2;Ptk6^+/+ (28.5%) and B2;Ptk6^−/− (2.8%) is statistically significant (*P<0.001). (e) Active PTK6 (P-Y342) and active phospho-STAT3 (PY705) can be detected in the same areas in the B2;Ptk6^+/+ mammary glands. In contrast, active phospho-STAT3 was not detectable in B2;Ptk6^−/−animals. The size bars represent 50 μm