Late-stage T-ALL cells counterselect against loss of Dicer1 function. (A) Kaplan-Meier survival plot of secondary RAG2γc^−/− recipients from 3 pooled independent experiments. Depicted are 3 experimental groups: (1) RAG2γc^−/− injected with p-I:C only, RAG2γc^−/− + p-I:C; (2) RAG2γc^−/− transplanted with late-stage T-ALL cells (Dicer1^lox/lox) and injected with p-I:C, Dicer1^lox/lox + p-I:C; and (3) RAG2γc^−/− transplanted with late-stage T-ALL cells (Dicer1^{lox/lox Mx1-Cre}) and injected with p-I:C, Dicer1^{lox/lox Mx1-Cre} + p-I:C . The dashed line indicates MST: red = 15 days, green = 43 days. P-I:C and arrows indicate p-I:C injections. (B) T-ALL progression measured by the percentage of NGFR⁺ cells in total PBLs. P-I:C and arrows indicate p-I:C injections. (C) Dicer1 deletion PCR. Shown are the results on DNA samples of representative tumor cells prior to transplantation into RAG2γc^−/− recipients (“input”, Dicer1^lox/lox and Dicer1^{lox/lox Mx1-Cre}; left panel), PBLs and splenocytes of corresponding representative secondary recipient animals after transplantation (“secondary recipients”; middle and right panels) 23 to 43 days p.tr. (D) Bar graph depicts the absolute cell numbers of splenocytes isolated from late-stage secondary T-ALL recipient animals.