Abstract
Constitutively activated AKT kinase is a common feature of T-cell acute lymphoblastic leukemia (T-ALL). Here, we report that the novel AKT inhibitor (2S)-1-(1H-indol-3-yl)-3-[5-(3-methyl-2H-indazol-5-yl)pyridin-3-yl]oxypropan2-amine (A443654) leads to rapid cell death of T-ALL lines and patient samples. Treatment of CEM, Jurkat, and MOLT-4 cells with nanomolar doses of the inhibitor led to AKT phosphorylation accompanied by dephosphorylation and activation of the downstream target, glycogen synthase kinase-3β. Effects were time- and dose-dependent, resulting in apoptotic cell death. Treatment of Jurkat cells with A443654 resulted in activation of caspase-2, -3, -6, -8, and -9. Apoptotic cell death was mostly dependent on caspase-2 activation, as demonstrated by preincubation with a selective pharmacological inhibitor. It is remarkable that A443654 was highly effective against the drug-resistant cell line CEM-VBL100, which expresses 170-kDa P-glycoprotein. Moreover, A443654 synergized with the DNA-damaging agent etoposide in both drug-sensitive and drug-resistant cell lines when coadministered [combination index (CI) = 0.39] or when pretreated with etoposide followed by A443654 (CI = 0.689). The efficacy of A443654 was confirmed using blasts from six patients with T-ALL, all of whom displayed low levels of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and constitutive phosphorylation of Akt on Ser473. At 1 μM, the inhibitor was able to induce apoptotic cell death of T-ALL blast cells, as indicated by flow cytometric analysis of samples immunostained for active (cleaved) caspase-3. Because activated AKT is seen in a large percentage of patients with T-ALL, A443654, either alone or in combination with existing drugs, may be a useful therapy for primary and drug-resistant T-ALL.
- The American Society for Pharmacology and Experimental Therapeutics
MolPharm articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|