In their search for fundamental molecular mechanisms, which regulate proliferation/differentiation in primary human keratinocytes, intact epidermis and squamous cell carcinoma, Kolev et al. [73] identified EGFR as a key negative regulator of Notch 1 gene expression through transcriptional suppression of p53 by the EGFR effector c-Jun. Here, JUN is linked to squamous cell carcinoma.