Loss of Kras promotes an early-onset ETP-like ALL in Nras^Q61R/+ mice. Six- to 7-week-old Mx1-cre (Con), Kras^−/− (K−/−), Nras^Q61R/+ (Q/+), Kras^+/−; Nras^Q61R/+ (K+/−; Q/+), and Kras^−/−; Nras^Q61R/+ (K−/−; Q/+) mice were treated with pI-pC as described in "Materials and methods." Moribund Q/+ or K−/−; Q/+ mice and age-matched control and K−/− mice were euthanized for analysis. (A) Experimental scheme and genotyping of Kras and Nras alleles in different groups of animals. (B) Kaplan-Meier survival curves were plotted against days after the first pI-pC injection. P values were determined using the log-rank test. (C) Disease incidence in K−/−, Q/+, K+/−; Q/+, and K−/−; Q/+ mice. χ² analysis was performed. (D) Quantification of thymus weight. T-cell malignancy is defined as thymus weight >150 mg (red dashed line). (E) Quantification of the number of Thy1.2⁺ Mac1⁺ thymocytes. (F) Quantification of the number of early T-cell precursors. DN, CD4⁻ CD8⁻ T cells; DN1, CD44⁺ CD25⁻ DN cells; DN2, CD44⁺ CD25⁺ DN cells. Data are plotted as mean + standard deviation (SD). P values were calculated with a 2-tailed Student t test. *P < .05; **P < .01; ***P < .001.