While Sag+/+ control mice developed a very limited number of skin tumors only in two out of seven mice, Sag−/‐ mice developed a much greater number of tumors in 4 out of 5 mice (Figure 1A, top and middle panels, and Figure S1A), indicating that Sag deletion promoted the development of skin tumors in this two‐stage chemical carcinogenesis model. This evidence concerns the gene SAG and skin neoplasm.