SPHK1 is overexpressed in AML. (A) Microarray analysis of SPHK1 mRNA levels from FACS-purified HSCs (Lin⁻/CD34⁺/CD38⁻/CD90⁺/CD45RA⁻) and AML cells from various cytogenetic subgroups obtained from BloodSpot (median, 25 to 75 percentiles boxed, and 10 to 90 percentiles shown with bars).²²  Significance was assessed by Student t test (*P < .05; **P < .01; ***P < .001) for HSCs compared with all AML subtypes shown. (B) Normalized RNA-Seq reads (reads per kilobase per million mapped reads; RPKM) for SPHK1 from primary AML patient samples (n = 171) and normal bone marrow samples (n = 4) were obtained from TCGA and the Human Protein Atlas, respectively. Significance was assessed by Student t test (P < .05). (C) Primary AML blasts or normal bone marrow MNCs where lysed and subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis followed by western blot analysis of total SPHK1 and phospho-Ser225 SPHK1. Western blot results were quantified by laser densitometry and expressed as the ratio of SPHK1/ACTB.