Cyclin E accumulates during squamous differentiation and when overexpressed in proliferative keratinocytes it promotes replication stress, DNA damage, mitotic defects and polyploidy.9, 20, 22, 23 To study this response in carcinoma cells we overexpressed a GFP form of Cyclin E in cells originated from a human facial BCC (BCCP;24Supplementary Figure 1a) or from a human facial well-differentiated SCC (SCC12F;25Supplementary Figure 1a). The gene discussed is CCNE1; the disease is skin basal cell carcinoma.