KLF4 and head and neck squamous cell carcinoma: Conversely, KLF4 may also function as an oncogene, as it is overexpressed in human breast cancer 60, 61, oropharyngeal epidermoid carcinoma 62, skin squamous cell carcinomas 63, head and neck squamous cell carcinoma (HNSCC) 62, 64, related to an aggressive course 65.