CDK4 and infectious otitis media: Immunostaining-positive cells of β-catenin (green; Figure 1A), Sox9 (red; Figure 1B), Ki67 (green; Figure 1C), cyclin D1 (red; Figure 1D), or CDK4 (green; Figure 1E) were observed in the micro-neoplastic lesions of the AOM/DSS mice using DAPI nuclear staining (blue).