Human acute leukemia cells actively transport and use BCAA. (A) The schema for the cellular metabolite quantification. (B) Cellular content of each BCAA in normal CD34⁺ HSPCs, AML cells, and ALL cells. (C) Representative fluorescence-activated cell sorting (FACS) data for the expression of BCAA transporters, including large neutral amino acid transporter 2 (LAT2), LAT3, and LAT4 in primary CD34⁺ AML (upper panels) and CD34⁺ ALL cells (lower panels). Gray and red lines represent isotype control and anti-LAT antibodies, respectively. (D) Quantification of LAT2, LAT3, and LAT4 proteins in normal and leukemic CD34⁺ cells using the mean fluorescent intensity (MFI) ratio between the target and the isotype control. (E) Quantification of serum BCAA concentration in HDs and patients with hematologic malignancies, including AML, ALL, non-Hodgkin lymphoma, and CML/myeloproliferative neoplasms chronic phase. Notably, patients with AML and patients with ALL had significantly decreased levels. ∗P < .05, ∗∗P < .01, ∗∗∗P < .001, panels B and D, mean ± standard error of the mean (SEM). Max, maximum; pt, patient.