SIRT1 sensitized ALL cells to panobinostat through activation of the mitochondrial apoptosis pathway. (A) Western blot analysis of SIRT1 expression in Nalm6 and REH transduced with CON, SIRT1 sgRNA (sgSIRT1), or OE vectors. (B-C) The MTT assay was performed to detect relative sensitivity of CON, SIRT1 sgRNA (sgSIRT1), and OE cells in Nalm6 (B) and REH (C); cells were incubated with the indicated concentration of panobinostat for 3 days. (D) Annexin V staining of apoptosis cells after panobinostat treatment in Nalm6 transduced with CON, SIRT1 sgRNA (sgSIRT1), or OE vectors. (E) Quantitative reverse transcriptase-PCR analysis of PMAIP1 expression in Nalm6 transduced with CON, SIRT1 sgRNA (sgSIRT1), or OE vectors with or without panobinostat treatment. (F) Western blot analysis of PMAIP1 and cleaved PARP expression with actin B as an internal control in Nalm6 transduced with CON, SIRT1 sgRNA (sgSIRT1), or OE vectors with or without panobinostat treatment. (G) Schematic outline of this study. SIRT1 sensitized ALL cells to panobinostat through activation of the PMAIP1-mediated mitochondrial apoptosis pathway. Data represent mean ± SD (n = 3). r, Pearson correlation coefficient.