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Fig. 3
Tumor induced by periodic or constitutive, but not transient activation of kRASG12V expression. In the latter system, one-time activation of kRASG12V expression was induced by transient cyclofen incubation or photo-activation of caged cyclofen at 1dpf (A). Periodic kRASG12V expression was achieved by 1 day incubation in 2 μM cyclofen every 5 days for a course of two months (E). (B–D) Transient induction of kRASG12V did not affect normal development (as shown by the histopathological staining) with no CFP expression in one-year old fish. (E–H) Tumors were observed (albeit rarely) in fish periodically treated with cyclofen. A representative one-year old fish displayed a clear tumor (E) revealed by histopathological staining (H). Interestingly, the cells in the tumor still expressed EosFP (F), but lost CFP expression (G). (I–L) Constitutive kRASG12V expression following light-activation of caged cyclofen induced tumor (I) in 5 month-old fish as revealed by both fluorescent markers (J,K) and H&E staining (L). Scale bar: B, D, F, H, L 200 μm; J, 1 cm.