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. Author manuscript; available in PMC: 2021 Aug 12.
Published in final edited form as: Nat Genet. 2020 Oct 26;52(11):1139–1143. doi: 10.1038/s41588-020-00727-5

Fig. 1 ∣. The permanence of the initiated state.

Fig. 1 ∣

a, Standard initiation-promotion model. Mice are treated once with a carcinogen (usually DMBA) at 8 weeks of age and 1 week later with twice-weekly treatment with a promoting agent (usually TPA). Treatment with either DMBA alone (top row) or TPA alone (second row) does not give rise to tumor development during a follow-up period of 1 year. However, DMBA followed by TPA induces benign tumors (papillomas) in 1–2 months, some of which progress to carcinomas after 5–12 months. b, Delayed-promotion model. Treatment with the carcinogen is followed a delay of 6–18 months before the start of promoter treatment. Benign tumors appear 1–2 months after starting TPA, and carcinomas develop after 5–12 months. The overall tumor yield decreases slightly after longer delay periods20-22.