Irum Khan

Nuclear FOXM1 drives chemoresistance in AML

CnB1fl/Δ or CnB1Δ/Δ leukemic cells (Figure 2c, d0). Dasatinib (10 mg/kg/day) was administered to the remaining recipients and three mice per group were killed 1, 2 or 6 days after the start of treatment to monitor tumor load. After 1 day of treatment, no significant decrease in tumor load was observed. In contrast, at day 2, no GFP+ leukemic cells were detected in the spleen and liver, while tumor load in BM was decreased with, however, no significant difference between mice injected with CnB1fl/Δ or CnB1Δ/Δ leukemic cells (Figure 2c, d2). After 6 days of treatment, leukemic cells were absent from the BM, spleen and liver of all recipients (Figure 2c, d6). Thus, in this in vivo setting, Cn-deficient cells did not show increased sensitivity to dasatinib treatment as compared to their Cn-proficient counterparts. In T-ALL, Cn impinges upon leukemic cell survival, proliferation and migration, and is critical to leukemia-propagating activity in mice. In contrast, Cn is dispensable for BCR-ABLinduced B-ALL maintenance and propagation as none of these traits are affected by genetic ablation of Cn function in distinct mouse models. Yet, the survival, proliferation and migratory activity of Cn-deficient B-ALL remain inhibited by CsA, and CsA still sensitized these cells to TKI cytotoxic effects. Cn is thus not the critical target of CsA cooperation with TKI. CsA activity relies upon its binding to at least six members of the cyclophilin family of peptidyl-prolyl isomerases (PPIases) and inhibits their prolyl cis/trans isomerization activity. Recent evidence shows that cis/trans isomerization of a number of proteins, including growth factor receptors, adaptors and transcription factors, functions as a molecular switch to regulate their activity. Deregulation of these pathways is likely instrumental in the emerging role of cyclophilins in cancer development and resistance to treatment. Identification of CsA-sensitive cyclophilin substrates or, possibly, recently described direct CsA protein targets involved in leukemic cell survival and proliferation, and relevant to sensitization to TKI responses, will provide new therapeutic options in Ph+ B-ALL treatment.

The rocky road to personalized medicine in acute myeloid leukaemia

Acute myeloid leukaemia (AML) is a malignant disorder of the myeloid blood lineage characterized by impaired differentiation and increased proliferation of hematopoietic precursor cells. Recent technological advances have led to an improved understanding of AML biology but also uncovered the enormous cytogenetic and molecular heterogeneity of the disease. Despite this heterogeneity, AML is mostly managed by a ‘one‐size‐fits‐all’ approach consisting of intensive, highly toxic induction and consolidation chemotherapy. These treatment protocols have remained largely unchanged for the past several decades and only lead to a cure in approximately 30–35% of cases. The advent of targeted therapies in chronic myeloid leukaemia and other malignancies has sparked hope to improve patient outcome in AML. However, the implementation of targeted agents in AML therapy has been unexpectedly cumbersome and remains a difficult task due to a variety of disease‐ and patient‐specific factors. In this review, we describe current standard and investigational therapeutic strategies with a focus on targeted agents and highlight potential tools that might facilitate the development of targeted therapies for this fatal disease. The classes of agents described in this review include constitutively activated signalling pathway inhibitors, surface receptor targets, epigenetic modifiers, drugs targeting the interaction of the hematopoietic progenitor cell with the stroma and drugs that target the apoptotic machinery. The clinical context and outcome with these agents will be examined to gain insight about their optimal utilization.

Honokiol is a FOXM1 antagonist

Honokiol is a natural product and an emerging drug for a wide variety of malignancies, including hematopoietic malignancies, sarcomas, and common epithelial tumors. The broad range of activity of honokiol against numerous malignancies with diverse genetic backgrounds suggests that honokiol is inhibiting an activity that is common to multiple malignancies. Oncogenic transcription factor FOXM1 is one of the most overexpressed oncoproteins in human cancer. Here we found that honokiol inhibits FOXM1-mediated transcription and FOXM1 protein expression. More importantly, we found that honokiol’s inhibitory effect on FOXM1 is a result of binding of honokiol to FOXM1. This binding is specific to honokiol, a dimerized allylphenol, and was not observed in compounds that either were monomeric allylphenols or un-substituted dihydroxy phenols. This indicates that both substitution and dimerization of allylphenols are required for physical interaction with FOXM1. We thus demonstrate a novel and specific mechanism for FOXM1 inhibition by honokiol, which partially may explain its anticancer activity in cancer cells.

A prospective study of intravenous pentamidine for PJP prophylaxis in adult patients undergoing intensive chemotherapy or hematopoietic stem cell transplant

Prophylaxis for Pneumocystis jirovecii pneumonia (PJP) is recommended for patients undergoing hematopoietic stem cell transplantation (HSCT) or intensive chemotherapy. Trimethoprim–sulfamethoxazole and inhaled pentamidine are used frequently, but are limited, by their tolerability and therefore compliance. Intravenous (IV) pentamidine is a potential alternative agent. Here we conducted the first prospective study of the safety and efficacy of IV pentamidine for PJP prophylaxis in adult patients undergoing HSCT or intensive chemotherapy (clinicaltrials.gov NCT02669706). Fifty patients requiring PJP prophylaxis were enrolled and received monthly IV pentamidine at 4 mg/kg (maximum 300 mg) while undergoing intensive chemotherapy or HSCT. Patients were followed for the occurrence of PJP pneumonia and for adverse events. Satisfaction was assessed using the Treatment Satisfaction Questionnaire for Medication (TSQM Version 1.4) survey. Seventeen (34%) patients experienced a grade 1 or 2 adverse event. There were no grade 3/4 events. The TSQM questionnaire indicated that the majority of patients were satisfied with the administration of IV pentamidine (n = 43, 86%, p  = 0.01). There were no cases of PJP during the 24 month follow-up period. Our study illustrates the safety, feasibility, and high degree of patient satisfaction when using IV pentamidine for PJP prophylaxis.

Haploidentical Peripheral Blood Stem Cell Transplantation Demonstrates Stable Engraftment in Adults with Sickle Cell Disease

Abstract We report on the screening and development of haploidentical hematopoietic stem cell transplantation (HSCT) for adult patients with clinically aggressive sickle cell disease (SCD) at our institution. Of 50 adult SCD patients referred for HSCT between January 2014 and March 2017, 20% were denied by insurance. Of 41 patients initially screened, 10% lacked an available haploidentical donor, 29% had elevated donor-specific antibodies (DSAs), and 34% declined to proceed to HSCT. All 10 patients who were transplanted received peripheral blood stem cells. The initial 2 were conditioned with alemtuzumab/total body irradiation (TBI) 3 Gy followed by post-transplant cyclophosphamide and failed to engraft. The next 8 patients received the regimen developed at Johns Hopkins University with TBI 3 Gy. Granulocyte colony-stimulating factor was administered from day +12 in those with HbS < 30%. All 8 patients engrafted with a median time to neutrophil >.5 × 109/L of 22 days (range, 18 to 23). One patient subsequently lost the graft, and 7 (87.5%) maintained >95% donor cell chimerism at 1-year post-HSCT. Two patients developed acute graft-versus-host disease (GVHD) of at least grade II. One had chronic GVHD and died >1 year after HSCT of unknown causes. With a median follow-up of 16 months (range, 11 to 29), 7 patients (87.5%) are alive. Our findings suggest that limited insurance coverage, high rate of DSAs, and patient declining HSCT may limit the availability of haploidentical HSCT in adult SCD patients. The modified Hopkins regimen used here demonstrates high engraftment and low morbidity rates and should be tested in larger, multicenter, prospective clinical trials.

Abstract 28: The novel role of FOXM1 in AML

Forkhead box M1 (FOXM1) is a transcription factor of the Forkhead family that induces the expression of genes involved in the execution of the mitotic program of normal cells, while it overexpressed in the majority of human cancer cells. In addition, FOXM1 regulatory network was a major predictor of adverse survival outcomes. We have previously shown that FOXM1 interacts with nucleophosmin (NPM) in cancer cells and NPM determines cellular localization of FOXM1. Mutations in NPM1 result in cytoplasmic relocalization of NPM (NPM1mut) and favorable outcome for the patients. We have also shown by immunofluorescence in the AML cell line OCI-AML3 and in AML primary samples with NPM1mut, FOXM1 and mutant NPM co-localize in the cytoplasm. Here we show the evidence that improved outcomes in the subset of NPM1mut AML may be partially explained by the cytoplasmic relocalization and consequent functional inactivation of FOXM1. First, we confirmed the colocalization of FOXM1 and NPMmut in cytoplasm of AML primary patient samples using Vectra imaging of AML diagnostic bone marrow biopsies. Strong cytoplasmic expression of FOXM1 was seen only in NPM1mut AML cells. We proceeded to test the role of FOXM1 in mediating chemoresistance in leukemia cell lines with nuclear FOXM1. Stable knockdown of FOXM1 in AML cell lines KG-1 with nuclear FOXM1/wild-type NPM resulted in increased sensitivity to the chemotherapeutic agent cytarabine. We overexpressed FOXM1 in the OCI-AML3 cell line with cytoplasmic localization of FOXM1 and confirmed overexpression of exogenous FOXM1 in the nuclear compartment by fractionation. Furthermore, we showed that nuclear overexpression of FOXM1 switches the sensitivity of these leukemia cell line to resistant phenotype. These data imply that suppressing of FOXM1 in AML could increase sensitivity to standard chemotherapy, while overexpression of FOXM1 increases chemoresistance of AML cells. Our data suggest that FOXM1 inhibitors may be useful for AML patients with FLT3 wild-type/NPM1 wild type with nuclear FOXM1. We used two compounds to target FOXM1 in AML: honokiol and ixazomib. Honokiol inhibits FOXM1-mediated transcription and FOXM1 protein expression and honokiol9s inhibitory effect on FOXM1 is a result of direct binding of honokiol to FOXM1. We found that that honokiol suppresses FOXM1 in AML cell lines and sensitizes AML cells with nuclear FOXM1 to cytorabine. We also tested novel proteasome inhibitor ixazomib (Takeda) as a potential FOXM1 inhibitor in AML. We found that similarly to several other proteasome inhibitors ixazomib inhibits transcriptional activity of FOXM1, FOXM1 mRNA, and FOXM1 protein expression in primary AML cells and in AML cell line. In addition, it shows potential synergy with AML9s most common drug cytarabine. Combination of cytarabine and ixazomib in AML KG1 cells led to strong apoptosis correlated with FOXM1 suppression. Since ixazomib is already approved for patients with multiple myeloma and it works as FOXM1 inhibitor in AML, we propose to test it as FOXM1 inhibitor in vivo. These results substantiate FOXM1 targeting to improve chemosensitivity for AML treatment. Our work is based on an intriguing premise that nuclear export of FOXM1 by mutant NPM1 in a subset of favorable risk AML is responsible for outcome. Furthermore, the idea that FOXM1 inactivation leads to favorable outcome gives rise to several strategies to develop FOXM1 inhibitors to increase the efficacy of chemotherapy in AML patients. Citation Format: Irum Khan, Marianna Halasi, Andrei L. Gartel. The novel role of FOXM1 in AML [abstract]. In: Proceedings of the Second AACR Conference on Hematologic Malignancies: Translating Discoveries to Novel Therapies; May 6-9, 2017; Boston, MA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(24_Suppl):Abstract nr 28.