Human myeloid cells promote survival of patient T-ALL cells in vitro, and an elevated macrophage gene signature in patients is associated with worse prognosis. (A) Quantification of viable primary patient T-ALL cells cultured for 6 or 7 days in the presence or absence of monocytes from healthy donor PBMCs or the indicated monocyte-derived myeloid cells. T-ALL viability was assessed by flow cytometry. Data are compiled from 2 to 4 independent experiments using 4 to 6 distinct patient-derived leukemias. Each circle represents the average of 2 or 3 technical replicates. (B) Longitudinal event-free survival is plotted for pediatric T-ALL patients stratified into 2 groups based on their enrichment scores for macrophage or monocyte gene signatures, as indicated. Patient data were analyzed from published datasets from 264 T-ALL patients from the TARGET ALL Phase 2 trial.⁵²  (C) Plot depicts the correlation between log-transformed Csf1 expression values and macrophage enrichment scores in patient samples. The red and dotted lines represent the best-fit line and 95% confidence bands, respectively. Circles represent each patient sample. (D) pIGF1R levels were quantified by flow cytometry in patient T-ALL cells cultured for 3 or 4 days in the presence or absence of PBMC-derived monocytes or the indicated monocyte-derived myeloid cells. Data are normalized to levels in T-ALL cells cultured alone (red line). Bars represent means + SEM from 3 to 5 independent experiments using 3 to 6 distinct color-coded patient-derived T-ALL samples. Circles represent the average of 2 technical replicate wells. (E) Quantification of viable patient T-ALL cells cultured alone or with M-CSF–derived macrophages in the presence of 10 µM AG-1024 (an IGF1R inhibitor) or DMSO. Results were normalized to DMSO-treated cultures in each experiment (red line). Bars represent means + SEM from 3 independent experiments using 4 of the distinct color-coded patient T-ALL samples used for cocultures with M-CSF–derived macrophages in (D). Circles represent the average of 2 technical replicate wells. *P < .05, paired Student t test (A), log-rank test (B), simple linear regression analyses (C), 1-sample Student t test (D), repeated measures 1-way ANOVA with the Bonferroni correction (E). ns, not significant.