NFKB1 and squamous cell carcinoma: The first pieces of evidence that NF-kB can function as a tumor suppressor came from studies of chemically-induced skin cancer, in which inhibition of NF-kB via IĸB-SR expression in keratinocytes enhanced the multiplicity of squamous cell carcinomas in response to 7,12-Dimethylbenz(a)anthracene (DMBA).