Figure 3.
SPHK1 mediates chemotherapeutic resistance in AML. (A) Primary AML blasts where treated with subcytotoxic concentrations of MP-A08 (●), cytarabine (▪), or a combination of both (▲), and cell survival was quantified at 24 to 48 hours by annexin V staining. Synergism was assessed by the Chou-Talalay combination index (CI) using CalcuSyn software, where CI values <1 indicate synergism, or the fractional product method, where values <−0.1 indicate synergism (AML1 = −0.18, AML9 = −0.13, AML6 = −0.27). (B) FACS-purified primary human CD34+/CD38−/CD123+ LSPCs were treated with subcytotoxic concentrations of MP-A08, cytarabine, or a combination of both for 48 hours, and cell survival was determined by annexin V staining. (C) MV4-11 cells were transduced with a doxycycline-inducible lentiviral vector to overexpress FLAG-tagged SPHK1. Twenty-four hours after induction, cells were treated with increasing doses of MP-A08 for 48 hours, and cell survival was determined by annexin V staining. Results are mean ± range. (D) Immunoblot analysis of whole cell lysates with anti-FLAG confirmed doxycycline-inducible expression.