salinomycin and Leukemia--Promyelocytic--Acute

All-trans retinoic acid (ATRA) is only effective in acute promyelocytic leukemia (APL), but not in other subtype of acute myeloid leukemia (AML). Salinomycin targets tumor cells rather than non-tumorigenic cells, and WNT/β-catenin pathway inhibition is one of the mechanisms of its anti-tumor activity. There is a crosstalk between RA and WNT/β-catenin pathway. Here, we investigate the effect of the combination of salinomycin and ATRA (S+RA) in non-APL AML cells.. Apoptosis was evaluated by cell viability and Annexin-V assay. Cell differentiation was analyzed by CD11c expression and morphology. To explore the underlying mechanisms, Western blot analysis and mitochondrial transmembrane potentials (ΔΨm) were used.. S+RA induced differentiation and apoptosis in AML cell lines and AML primary cells. S+RA inhibited the β-catenin signal pathway as determined by the decreased protein levels of β-catenin, the low-density lipoprotein receptor-related proteins 6 (LRP6), and its downstream proteins such as survivin, c-Myc, caspase-3/7, cdc25A and cyclinD1 and reduced phosphorylation level of GSK3β S9. S+RA also increased the protein levels of CCAAT/enhancer-binding proteins (C/EBPs) and PU.1 and collapsed Δψm. The above molecular and cellular changes induced by S+RA were inhibited by β-catenin specific activator and promoted by β-catenin specific inhibitor.. S+RA induced differentiation by β-catenin-inhibition-mediated up-regulation of C/EBPs and PU.1 and suppression of c-Myc. S+RA triggered apoptosis through β-catenin-inhibition-regulated ΔΨm collapse and caspase-3/7 activation. Taken together, our findings may provide novel therapeutic strategies for AML patients by targeting the WNT/β-catenin pathway.

Topics: Apoptosis; beta Catenin; Caspase 3; Cell Differentiation; Cell Line, Tumor; Humans; Leukemia, Myeloid, Acute; Leukemia, Promyelocytic, Acute; Tretinoin; Wnt Signaling Pathway

At present, acute promyelocytic leukemia (APL) is the most curable form of acute myeloid leukemia and can be treated using all-trans retinoic acid and arsenic trioxide. However, the current treatment of APL is associated with some issues such as drug toxicity, resistance and relapse. Therefore, other strategies are necessary for APL treatment. In the present study, we investigated the effects of salinomycin (SAL) on APL cell lines NB4 and HL-60 and determined its possible mechanisms. We observed that SAL inhibited cell proliferation, as determined by performing Cell Counting Kit-8 (CCK-8) assay, promoted cell apoptosis, as determined based on morphological changes, and increased Annexin V/propidium iodide (PI)-positive apoptotic cell percentage. Treatment with SAL increased Bax/Bcl-2 and cytochrome c expression and activated caspase-3 and -9, thus leading to poly(ADP-ribose) polymerase (PARP) cleavage and resulting in cell apoptosis. These results revealed that SAL induced cell apoptosis through activation of the intrinsic apoptosis pathway. The present study is the first to show that SAL induced the differentiation of APL cells, as determined based on mature morphological changes, increased NBT-positive cell and CD11b-positive cell percentages and increased CD11b and C/EBPβ levels. Furthermore, SAL decreased the expression of β-catenin and its targets cyclin D1 and C-myc. Results of immunofluorescence analysis revealed that SAL markedly decreased the β-catenin level in both the nucleus and cytoplasm. Combination treatment with SAL and IWR-1, an inhibitor of Wnt signaling, synergistically triggered SAL-induced differentiation of APL cells. These findings demonstrated that SAL effectively inhibited cell proliferation accompanied by induction of apoptosis and promotion of cell differentiation by inhibiting Wnt/β-catenin signaling. Collectively, these data revealed that SAL is a potential drug for treatment of APL.

Topics: Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Arsenic Trioxide; Arsenicals; Cell Differentiation; Cell Line, Tumor; Drug Resistance, Neoplasm; Drug Synergism; Humans; Imides; Leukemia, Promyelocytic, Acute; Oxides; Pyrans; Quinolines; Tretinoin; Wnt Signaling Pathway