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Chronic activation of the Bruton’s tyrosine kinase (BTK)-mediated B-cell receptor (BCR) signaling is a hallmark of many B-cell lymphoid malignancies, including chronic lymphocytic leukemia (CLL) and diffuse large B-cell lymphoma (DLBCL). Ibrutinib, an FDA approved, orally administered BTK inhibitor, has demonstrated high response rates, however, complete responses are infrequent and acquired resistance to BTK inhibition can emerge. In this study, we generated ibrutinib-resistant (IB-R) cell lines by chronic exposure of CLL and activated B-cell (ABC)-DLBCL cells to ibrutinib in order to investigate the mechanism of acquired resistance to ibrutinib. IB-R cell lines demonstrated downregulation of FOXO3a and PTEN levels and activation of AKT, with their levels being low in the nuclei of resistant cells in comparison to the sensitive counterparts. Inhibition of PI3K and AKT using idelalisib and MK2206, respectively increased ibrutinib-induced apoptosis in IB-R cells by downregulation of pAKT473 and restoring FOXO3a levels, demonstrating the importance of these cell survival factors for ibrutinib-resistance. Notably, the exportin 1 inhibitor, selinexor synergized with ibrutinib in IB-R cells and restored nuclear abundance of FOXO3a and PTEN, suggesting that nuclear accumulation of FOXO3a and PTEN facilitates increase in ibrutinib-induced apoptosis in IB-R cells. These data demonstrate that reactivation of FOXO3a nuclear function enhances the efficacy of ibrutinib and overcomes acquired resistance to ibrutinib. Together, these findings reveal a novel mechanism that confers ibrutinib resistance via aberrant nuclear/cytoplasmic subcellular localization of FOXO3a and could be exploited by rational therapeutic combination regimens for effectively treating lymphoid malignancies.

PurposeThis prospective phase II, open label, study was designed to assess the efficacy and safety of D-CAG induction treatment for elderly patients with newly diagnosed AML.Experimental DesignAll patients in this study were treated with decitabine of 15 mg/m2 for 5 days and G-CSF for priming, in combination with cytarabine of 10-mg/m2 q12h for 7 days and aclarubicin of 10 mg/day for 4 days (D-CAG).ResultsAmong 85 evaluable patients, overall response rate (ORR) and complete remission (CR) were 82.4% and 64.7%, respectively, after 1 cycle of therapy. The ORR in patients aged <70 years was 83.0% and 81.6% in patients aged ≥70 years. There was a significantly longer median overall survival (OS) in patients with response (16 months) than in those without response (7 months, p< 0.0001). The OS for patients aged ≥70 years and 60-69 years was 10 months and 12 months, respectively (p=0.4994). The two-year OS probability was 19.2% and the twenty-month survival rate was 33.8%. Induction mortality of D-CAG treated elderly patients with AML is 4.4%.ConclusionD-CAG regimen was well tolerated and showed a promising clinic efficacy in elderly patients with AML (≥70 years).