The ISR dampens human HSPC mTOR signaling. Representative immunoblots (A-B) and quantitative protein analysis (C-E) of human CD34⁺ cells after 24-hour drug treatment, equal protein loaded. (F) Gene expression analysis of CHOP in human CD34⁺ cells after 24-hour drug treatment. (G) Schematic of GW4869-driven ISR activation upstream of mTOR inhibition. Representative flow cytometric plots (H) and quantitative analysis (I) of PE-MitoSOX fluorescence intensity after human CD34⁺ cell GW4869 and/or SKQ1 treatment. Representative immunoblots (J) and quantitative analysis (K) of phospho-eIF2α levels in human CD34⁺ cells following GW4869 and 100 nM SKQ1 treatment, equal protein loaded. (L) Gene expression analysis of CHOP levels in treated human CD34+ cells. (M) Colony formation assay after 24-hour drug treatment. (N) Timeline of ISR sensitization experiments. (O) Relative gene expression in human CD34⁺ cells after GW4869 priming and CCT020312 (CCT) treatment. (P) Representative immunoblot and (Q) quantitative analysis of phospho-mTOR (Ser2448) levels in GW4869-primed CD34⁺ cells after CCT treatment. ∗P < .05; ∗∗P < .01; ∗∗∗P < .001. Refer to supplemental Figure 7.