Effects of knocking out SLFN11 in AML cells and in response to AraC treatment in vivo. (A) Schematic illustration of the AML xenograft mouse model and therapeutic regimen. Briefly, mice were injected SQ with U937-Cas9 or U937-SLFN11 KO cells (single clones). On day 8, mice from each tumor genotypic group were randomized by tumor volume and body weight into 2 treatment groups: VC (PBS) or AraC and daily treatments by intraperitoneal (IP) injection were given on days 9 to 18. Tumor volumes were measured 3 times per week until the study end point. Two independent in vivo studies were performed. (B-C) Tumor volumes (mean ± SEM) are shown for (B) PBS-treated or (C) AraC-treated mice implanted with either U937-Cas9 or U937-SLFN11 KO cells until the first tumor for either cohort reached 2000 mm³ (n = 8 for the PBS-treated groups and U937-Cas9 AraC-treated group and n = 9 for the U937-SLFN11 KO AraC-treated group). Mixed effects regression models were used to compare tumor growth between the groups. Tumor volume was the outcome variable, and log(volume + 1) transformation was used to stabilize the variance and satisfy the normality assumption. Day, group, and their interaction were included as fixed effects were fitted, and the within animal correlation between repeated tumor measurements over time was accounted for using a first-order autoregressive covariance structure (AR(1)). P value from the day × group interaction is reported. (D) Kaplan-Meier survival curves for the 4 treatment/genotypic groups (data compiled from the 2 in vivo studies, n = 12 for the PBS-treated and U937-Cas9 AraC-treated groups and n = 13 for the U937-SLFN11 KO AraC-treated group). Survival curves were compared using the log-rank test, and P values were adjusted for 4 pairwise comparisons (denoted in the figure) using the method of Holm-Sidak. ∗P < .05; ∗∗P < .01; ∗∗∗P < .001. NS, not significant; S.Q, subcutaneous.