RIPK4 and squamous cell carcinoma: Ripk4fl/fl;Pik3caH1047R mice not only developed multiple tumors within 3 months of age, but these tumors also progressed to invasive squamous cell carcinomas (SCCs) on their back skin and oral cavity, while Ripk4 wildtype or heterozygous littermate control mice expressing the Pik3caH1047R oncogene did not develop any tumors within a 1.5-year-long observation period (Figure 1B–C).