NG2 impairs the inhibition of the antiapoptotic PI3K/AKT/mTOR pathway in response to DX in MLLr B-ALL cells resulting in GC resistance. (A) Schematic representation of the GCR intracellular effects on the PI3K/AKT/mTOR pathway and the chemical inhibitors used to block the PI3K pathway (indicated in red color). (B-C) Immunoblots depicting the phosphorylation status of PI3K downstream members in both NG2^WT and NG2^KO SEM cells (B), as well as in NG2^POS and NG2^NEG MLLr B-ALL patient blasts in response to DX (C). (D) Immunoblots showing the levels of BCL2 family proteins in NG2^WT and NG2^KO SEM cells in response to DX are shown. Total protein levels are also shown. (E-G) Sensitization effect in response to DX of the indicated PI3K/AKT/mTOR pathway inhibitors at the indicated concentrations in NG2^WT and NG2^KO SEM cells. Right panels show area under the curve (AUC) for each viability curve. (H,I) Sensitization effect of MK-2206 (H) and rapamycin (I) in MLLr B-ALL blasts. (J) The MEK inhibitor PD98059 was used as a control for the absence of sensitization to DX. (K) Immunoblots showing the effect of PI3K/AKT/mTOR inhibitors alone or in combination with DX on BCL2 family proteins in NG2^WT MLL-AF4⁺ SEM cells. ∗P < .05, ∗∗P < .01, ∗∗∗∗P < .0001, unpaired Student t test. Ns, not significant.