Dose-Adjusted EPOCH Plus Inotuzumab Ozogamicin in Adults With Relapsed or Refractory B-Cell ALL: A Phase 1 Dose-Escalation Trial

Importance

Options for adults with relapsed or refractory B-cell acute lymphoblastic leukemia or lymphoma (B-ALL) are limited, and new approaches are needed. Inotuzumab ozogamicin (InO) has been combined with low-intensity chemotherapy, with modest improvements over historical controls, and dose-adjusted etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin (DA-EPOCH) treatment is safe and active for newly diagnosed ALL.

Objective

To assess the safety and clinical activity of DA-EPOCH and InO in adults with relapsed or refractory B-ALL.

Design, Setting, and Participants

This single-center, single-arm, nonrandomized, phase 1 dose-escalation trial included adults with relapsed or refractory CD22+ B-ALL and was conducted between September 2019 and November 2022. At least 5% blood or marrow blasts or measurable extramedullary disease (EMD) was required for enrollment.

Interventions

DA-EPOCH was given on days 1 to 5, while InO was given on day 8 and day 15 of a 28-day cycle. Three dose levels were studied using a bayesian optimal interval design.

Main Outcomes and Measures

The primary outcome was the maximum tolerated dose of InO when combined with DA-EPOCH, defined as the highest dose level that produced a rate of dose-limiting toxicity below 33%. Secondary objectives included response rates, survival estimates, and descriptions of toxic effects.

Results

A total of 24 participants were screened and enrolled (median age, 46 [range, 28-76] years; 15 [62%] male). The median number of lines of prior therapy was 3 (range, 1-12). Three of 11 participants (27%) treated at the highest dose level (InO, 0.6 mg/m2, on day 8 and day 15) experienced dose-limiting toxicity, making this the maximum tolerated dose. No deaths occurred during the study, and only 1 patient (4%; 95% CI, 0.1%-21%) developed sinusoidal obstructive syndrome after poststudy allograft. The morphologic complete response rate was 84% (95% CI, 60%-97%), 88% (95% CI, 62%-98%) of which was measurable residual disease negative by flow cytometry. Five of 6 participants with EMD experienced treatment response. The overall response rate was 83% (95% CI, 63%-95%). Median overall survival, duration of response, and event-free survival were 17.0 (95% CI, 8.4-not reached), 15.0 (95% CI, 6.7-not reached), and 9.6 (95% CI, 4.5-not reached) months, respectively.

Conclusions

In this study, adding InO to DA-EPOCH in adults with relapsed or refractory B-ALL was feasible, with high response rates and sinusoidal obstructive syndrome occurring rarely in a heavily pretreated population. Many patients were able to proceed to poststudy consolidative allogeneic hematopoietic cell transplant and/or chimeric antigen receptor T-cell therapy. Further investigation of this combination is warranted.

Trial Registration

ClinicalTrials.gov Identifier: NCT03991884.

Intensive Reinduction Chemotherapy Followed by Early Allogeneic Hematopoietic Cell Transplantation for Relapsed/Refractory High-Grade Myeloid Neoplasms

Outcomes for adults with relapsed/refractory (R/R) high-grade myeloid neoplasms remain poor, with allogeneic hematopoietic cell transplantation (HCT) the sole therapy likely to result in cure. We conducted the present study to determine the feasibility of early HCT-within 60 days of beginning reinduction chemotherapy-to see whether getting patients to HCT in an expeditious manner would expand the number of patients being offered this curative option. In this proof-of-principle feasibility study, we included adults age 18 to 75 years with R/R myeloid malignancies with ≥10% blood/marrow blasts at diagnosis who were eligible for a reduced-intensity HCT. Subjects received reinduction chemotherapy with cladribine, cytarabine, mitoxantrone, and filgrastim (CLAG-M) and proceeded to HCT with reduced-intensity conditioning (fludarabine/ melphalan). We enrolled 30 subjects, all of whom received CLAG-M reinduction, although only 9 underwent HCT within 60 days (<15, the predetermined threshold for feasibility "success"), with a median time to HCT of 48 days (range, 42 to 60 days). Eleven additional subjects received HCT beyond the target 60 days (off-study), with a median time to transplantation of 83 days (range, 53 to 367 days). Barriers to early HCT included infection, physician preference, lack of an HLA-matched donor, logistical delays, and disease progression, all of which may limit the real-world uptake of such early-to-transplantation protocols.

Discovery of U2AF1 neoantigens in myeloid neoplasms

BACKGROUND

Myelodysplastic syndromes (MDS) arise from somatic mutations acquired in hematopoietic stem and progenitor cells, causing cytopenias and predisposing to transformation into secondary acute myeloid leukemia (sAML). Recurrent mutations in spliceosome genes, including U2AF1, are attractive therapeutic targets as they are prevalent in MDS and sAML, arise early in neoplastic cells, and are generally absent from normal cells, including normal hematopoietic cells. MDS and sAML are susceptible to T cell-mediated killing, and thus engineered T-cell immunotherapies hold promise for their treatment. We hypothesized that targeting spliceosome mutation-derived neoantigens with transgenic T-cell receptor (TCR) T cells would selectively eradicate malignant cells in MDS and sAML.

METHODS

We identified candidate neoantigen epitopes from recurrent protein-coding mutations in the spliceosome genes SRSF2 and U2AF1 using a multistep in silico process. Candidate epitopes predicted to bind human leukocyte antigen (HLA) class I, be processed and presented from the parent protein, and not to be subject to tolerance then underwent in vitro immunogenicity screening. CD8+ T cells recognizing immunogenic neoantigen epitopes were evaluated in in vitro assays to assess functional avidity, confirm the predicted HLA restriction, the potential for recognition of similar peptides, and the ability to kill neoplastic cells in an antigen-specific manner. Neoantigen-specific TCR were sequenced, cloned into lentiviral vectors, and transduced into third-party T cells after knock-out of endogenous TCR, then tested in vitro for specificity and ability to kill neoplastic myeloid cells presenting the neoantigen. The efficacy of neoantigen-specific T cells was evaluated in vivo in a murine cell line-derived xenograft model.

RESULTS

We identified two neoantigens created from a recurrent mutation in U2AF1, isolated CD8+ T cells specific for the neoantigens, and demonstrated that transferring their TCR to third-party CD8+ T cells is feasible and confers specificity for the U2AF1 neoantigens. Finally, we showed that these neoantigen-specific TCR-T cells do not recognize normal hematopoietic cells but efficiently kill malignant myeloid cells bearing the specific U2AF1 mutation, including primary cells, in vitro and in vivo.

CONCLUSIONS

These data serve as proof-of-concept for developing precision medicine approaches that use neoantigen-directed T-cell receptor-transduced T cells to treat MDS and sAML.

Clinical Validation of FusionPlex RNA Sequencing and Its Utility in the Diagnosis and Classification of Hematologic Neoplasms

Recurrent gene rearrangements result in gene fusions that encode chimeric proteins, driving the pathogenesis of many hematologic neoplasms. The fifth edition World Health Organization classification and International Consensus Classification 2022 include an expanding list of entities defined by such gene rearrangements. Therefore, sensitive and rapid methods are needed to identify a broad range of gene fusions for precise diagnosis and prognostication. In this study, we validated the FusionPlex Pan-Heme panel analysis using anchored multiplex PCR/targeted RNA next-generation sequencing for routine clinical testing. Furthermore, we assessed its utility in detecting gene fusions in myeloid and lymphoid neoplasms. The validation cohort of 61 cases demonstrated good concordance between the FusionPlex Pan-Heme panel and other methods, including chromosome analysis, fluorescence in situ hybridization, RT-PCR, and Sanger sequencing, with an analytic sensitivity and specificity of 95% and 100%, respectively. In an independent cohort of 28 patients indicated for FusionPlex testing, gene fusions were detected in 21 patients. The FusionPlex Pan-Heme panel analysis reliably detected fusion partners and patient-specific fusion sequences, allowing accurate classification of hematologic neoplasms and the discovery of new fusion partners, contributing to a better understanding of the pathogenesis of the diseases.

Hyper-CVAD versus dose-adjusted EPOCH as initial treatment for adults with acute lymphoblastic leukemia

OBJECTIVES

We recently performed a single-arm phase II trial of DA-EPOCH in adults with acute lymphoblastic leukemia (ALL). We sought to compare these results to those with standard Hyper-CVAD.

METHODS

We created a retrospective matched cohort of patients who received Hyper-CVAD (n = 69) at our center and otherwise met eligibility criteria for the DA-EPOCH trial (n = 53).

RESULTS

Our outcomes support the use of Hyper-CVAD over DA-EPOCH in Ph- disease for both overall survival (OS; HR 0.18, p = .004) and event-free survival (EFS; HR 0.51, p = .06). In contrast, outcomes were similar in Ph+ disease (OS HR 0.97, p = .96; EFS HR 0.65, p = .21). Rates of morphologic remission and measurable residual-disease negativity were similar between the regimens. Hyper-CVAD was associated with significantly more febrile neutropenia (OR 1.9, p = .03) and a greater incidence of Grade 4 or 5 adverse events (20% vs. 6%). Average transfusions per cycle of both red blood cells (p < .001) and platelets (p < .001) were five-fold higher with Hyper-CVAD.

CONCLUSIONS

Our findings support continued use of Hyper-CVAD for Ph- ALL but suggest that DA-EPOCH may be a reasonable alternative for Ph+ ALL. These data also highlight a potential role for DA-EPOCH in resource-limited settings or when more intense therapy is not feasible.

Estimated Savings After Stopping Tyrosine Kinase Inhibitor Treatment Among Patients With Chronic Myeloid Leukemia

Importance

Patients with chronic myeloid leukemia (CML) who have a sustained deep molecular response using tyrosine kinase inhibitors (TKIs) can safely attempt to stop their use. As these medications are very costly, this change in treatment protocols may result in large savings.

Objective

To estimate future savings from attempting to stop TKI use among patients with CML who have deep molecular response.

Design, Setting, and Participants

A microsimulation model was developed for this decision analytical modeling study to estimate costs for US adults moving from using a TKI, to attempting discontinuation and then reinitiating TKI therapy, if clinically appropriate. Estimates were calculated for US patients who currently have CML and simulated newly diagnosed cohorts of patients over the next 30 years.

Exposure

Attempting to stop using a TKI.

Main Outcomes and Measures

Estimated savings after attempted discontinuation of TKI use.

Results

A simulated population of individuals with CML in 2018 and future populations were created using estimates from the SEER*Explorer website. The median age at diagnosis was 66 years for men and 65 years for women. Between 2022 and 2052, the savings associated with eligible patients attempting discontinuation of TKI therapy was estimated at more than $30 billion among those currently diagnosed and over $15 billion among those who will develop CML in the future, for a total savings of over $54 billion by 2052 for drug treatment and polymerase chain reaction testing. The estimate is conservative as it does not account for complications and other health care-associated costs for patients continuing TKI therapy.

Conclusions and Relevance

The findings of this decision analytical modeling study of patients with CML suggest that attempting discontinuation of TKI therapy could save over $54 billion during the next 30 years. Further education for patients and physicians is needed to safely increase the number of patients who can successfully attain treatment-free remission.

Phase 1/2 study of sorafenib added to cladribine, high-dose cytarabine, G-CSF, and mitoxantrone in untreated AML

The multikinase inhibitor sorafenib improves event-free survival (EFS) when used with 7 + 3 in adults with newly-diagnosed acute myeloid leukemia (AML), irrespective of the FLT3-mutation status. Here, we evaluated adding sorafenib to cladribine, high-dose cytarabine, granulocyte colony-stimulating factor, and mitoxantrone (CLAG-M) in a phase 1/2 trial of 81 adults aged ≤60 years with newly diagnosed AML. Forty-six patients were treated in phase 1 with escalating doses of sorafenib and mitoxantrone. No maximum tolerated dose was reached, and a regimen including mitoxantrone 18 mg/m2 per day and sorafenib 400 mg twice daily was declared the recommended phase 2 dose (RP2D). Among 41 patients treated at RP2D, a measurable residual disease-negative complete remission (MRD- CR) rate of 83% was obtained. Four-week mortality was 2%. One-year overall survival (OS) and EFS were 80% and 76%, without differences in MRD- CR rates, OS, or EFS between patients with or without FLT3-mutated disease. Comparing outcomes using CLAG-M/sorafenib with those of a matched cohort of 76 patients treated with CLAG-M alone, multivariable-adjusted survival estimates were improved for 41 patients receiving CLAG-M/sorafenib at RP2D (OS: hazard ratio,0.24 [95% confidence interval, 0.07-0.82]; P = .023; EFS: hazard ratio, 0.16 [95% confidence interval, 0.05-0.53]; P = .003). Benefit was limited to patients with intermediate-risk disease (univariate analysis: P = .01 for OS; P = .02 for EFS). These data suggest that CLAG-M/sorafenib is safe and improves OS and EFS relative to CLAG-M alone, with benefits primarily in patients with intermediate-risk disease. The trial was registered at www.clinicaltrials.gov as #NCT02728050.

Project Confirm: Accelerated Drug Approvals for Chronic Myeloid Leukemia

The FDA has an accelerated approval program for drugs that have been identified as promising treatments for serious conditions when the available data suggest that the benefits outweigh the foreseeable risks. All of the currently available treatment options for chronic myeloid leukemia (CML) initially went through the accelerated approval program. Here, a group of academic CML experts, patient panelists, and members from the FDA convened to discuss the utility of the accelerated approval program as it pertains to CML, and the utility of this program in future drug development in this disease. The results of that discussion are summarized here.

Phase II study of dose-adjusted EPOCH as initial therapy for adults with high-risk acute lymphoblastic leukemia

Treatments for adults with newly-diagnosed acute lymphoblastic leukemia (ALL) may be prohibitively toxic and/or resource-intense. To address this, we performed a phase II study of dose-adjusted etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin (DA-EPOCH). Imatinib or dasatinib was added for Ph + disease; rituximab was added when CD20+. Fifty-three patients were evaluable: 28 with Ph + disease, and 25 with Ph-. All patients had ≥1 high-risk clinical feature. Measurable residual disease-negativity by multiparameter flow cytometry within 4 cycles was achieved in 71% in patients with Ph + ALL and 64% in Ph - ALL. Median overall survival (OS) was 49 months, with a 2-year OS of 71%. Median relapse-free survival (RFS) in the 47 patients that attained morphologic remission was 24 months, with a 2-year RFS of 57%. Early mortality was 2%. In summary, DA-EPOCH yields deep and durable remissions in adults with ALL comparable to some resource-intense strategies but with a low rate of treatment-related death.

Phase 1/2 Trial of CLAG-M with Dose-Escalated Mitoxantrone in Combination with Fractionated-Dose Gemtuzumab Ozogamicin for Newly Diagnosed Acute Myeloid Leukemia and Other High-Grade Myeloid Neoplasms

Simple Summary

Several studies have demonstrated that gemtuzumab ozogamicin (GO) improves outcomes with intensive chemotherapy in some adults with acute myeloid leukemia (AML), but it has remained unclear which dosing schedule of GO is best. Here, we conducted a phase 1/2 study in 66 adults with newly diagnosed AML or other high-grade myeloid neoplasm, and found that a fractionated dosing schedule of GO (GO3) can be safely combined with cladribine, high-dose cytarabine, G-CSF, and dose-escalated mitoxantrone (CLAG-M). Fifty-two out of sixty (87%) patients treated with CLAG-M/GO3 achieved a complete remission (CR)/CR with incomplete hematologic recovery (CRi), 45/52 (87%) without flow cytometric measurable residual disease. Six- and twelve-month event-free survival were 73% and 58%; among favorable-risk patients, these estimates were 100% and 95%. Compared to 186 medically matched adults treated with CLAG-M alone, CLAG-M/GO3 was associated with better survival in patients with favorable-risk disease. These data indicate that CLAG-M/GO3 is safe and more efficacious than CLAG-M alone in favorable-risk AML/high-grade myeloid neoplasm.

Abstract

Gemtuzumab ozogamicin (GO) improves outcomes when added to intensive AML chemotherapy. A meta-analysis suggested the greatest benefit when combining fractionated doses of GO (GO3) with 7 + 3. To test whether GO3 can be safely used with high intensity chemotherapy, we conducted a phase 1/2 study of cladribine, high-dose cytarabine, G-CSF, and dose-escalated mitoxantrone (CLAG-M) in adults with newly diagnosed AML or other high-grade myeloid neoplasm (NCT03531918). Sixty-six patients with a median age of 65 (range: 19–80) years were enrolled. Cohorts of six and twelve patients were treated in phase 1 with one dose of GO or three doses of GO (GO3) at 3 mg/m² per dose. Since a maximum-tolerated dose was not reached, the recommended phase 2 dose (RP2D) was declared to be GO3. At RP2D, 52/60 (87%) patients achieved a complete remission (CR)/CR with incomplete hematologic recovery (CRi), 45/52 (87%) without flow cytometric measurable residual disease (MRD). Eight-week mortality was 0%. Six- and twelve-month event-free survival (EFS) were 73% and 58%; among favorable-risk patients, these estimates were 100% and 95%. Compared to 186 medically matched adults treated with CLAG-M alone, CLAG-M/GO3 was associated with better survival in patients with favorable-risk disease (EFS: p = 0.007; OS: p = 0.030). These data indicate that CLAG-M/GO3 is safe and leads to superior outcomes than CLAG-M alone in favorable-risk AML/high-grade myeloid neoplasm.

Patient- and physician-reported pain after tyrosine kinase inhibitor discontinuation among patients with chronic myeloid leukemia

For patients with optimally treated chronic myeloid leukemia (CML), discontinuation of tyrosine kinase inhibitor (TKI) therapy can lead to treatment-free remission. In previous trials, TKI discontinuation has been associated with increased musculoskeletal pain in some patients ("withdrawal syndrome"), based on physician-reported adverse events (AE). Patient-reported pain has not been described. The Life After Stopping TKI study was a 14-site prospective, non-randomized clinical trial of TKI discontinuation. We defined increased pain after discontinuation as: (i) a physician-reported pain AE, (ii) a 2-level increase in self-reported musculoskeletal pain (4-level single item), or (iii) initiation of a medication for pain. We plotted the trajectory of patient-reported pain over time using a piecewise mixed-effects ordinal logistic model. Within 3 months of discontinuation, 35 of 172 patients (20.3%) had a physician-reported pain AE, 22 of 172 (12.8%) had an increase in self-reported pain, and 18 of 154 (11.7%) initiated a pain medication. Agreement among these measures was limited; overall, 60 of 172 patients (34.9%) had increased pain. Three patients (1.7%) restarted a TKI because of pain. The modelpredicted trajectory showed an increase in pain in the first 3 months followed by a decrease, returning to baseline levels by 6 months and further decreasing after that. This trajectory was similar among patients who did and did not restart TKI, suggesting that resuming a TKI for withdrawal syndrome may be necessary for some, but other approaches to manage pain should be tried so that patients can remain in treatment-free remission when possible.

MS4A3 promotes differentiation in chronic myeloid leukemia by enhancing common β-chain cytokine receptor endocytosis

The chronic phase of chronic myeloid leukemia (CP-CML) is characterized by the excessive production of maturating myeloid cells. As CML stem/progenitor cells (LSPCs) are poised to cycle and differentiate, LSPCs must balance conservation and differentiation to avoid exhaustion, similar to normal hematopoiesis under stress. Since BCR-ABL1 tyrosine kinase inhibitors (TKIs) eliminate differentiating cells but spare BCR-ABL1-independent LSPCs, understanding the mechanisms that regulate LSPC differentiation may inform strategies to eliminate LSPCs. Upon performing a meta-analysis of published CML transcriptomes, we discovered that low expression of the MS4A3 transmembrane protein is a universal characteristic of LSPC quiescence, BCR-ABL1 independence, and transformation to blast phase (BP). Several mechanisms are involved in suppressing MS4A3, including aberrant methylation and a MECOM-C/EBPε axis. Contrary to previous reports, we find that MS4A3 does not function as a G1/S phase inhibitor but promotes endocytosis of common β-chain (βc) cytokine receptors upon GM-CSF/IL-3 stimulation, enhancing downstream signaling and cellular differentiation. This suggests that LSPCs downregulate MS4A3 to evade βc cytokine-induced differentiation and maintain a more primitive, TKI-insensitive state. Accordingly, knockdown (KD) or deletion of MS4A3/Ms4a3 promotes TKI resistance and survival of CML cells ex vivo and enhances leukemogenesis in vivo, while targeted delivery of exogenous MS4A3 protein promotes differentiation. These data support a model in which MS4A3 governs response to differentiating myeloid cytokines, providing a unifying mechanism for the differentiation block characteristic of CML quiescence and BP-CML. Promoting MS4A3 reexpression or delivery of ectopic MS4A3 may help eliminate LSPCs in vivo.

Patient-Reported Functional Outcomes in Patients with Chronic Myeloid Leukemia after Stopping Tyrosine Kinase Inhibitors

Treatment-free remission (TFR) is a goal for patients with chronic myeloid leukemia (CML). Functional outcomes after discontinuing Tyrosine Kinase Inhibitor (TKI) treatment have not been described. PROMIS patient-reported outcome measures (PROMs) of social, physical, cognitive, and sexual function were assessed over 36 months in 172 adult patients with chronic phase CML from 14 sites at baseline (on TKI) and after discontinuation. Linear mixed-effects models described the average trajectories for each PROM after discontinuation and in those who restarted TKI. Of 112 patients in TFR at 12 months, 103 (92.0%) had a ≥ 3-point improvement in social function, 80 (71.4%) in social isolation, 11 (9.8%) in satisfaction with sex life, 4 (3.6%) in physical function, and no patients had a ≥ 3-point improvement in cognitive function or interest in sexual activity. Patients' scores worsened after restarting TKI. This novel information on functional outcomes in TFR can help guide patient and clinician decision-making.

Assessment of Outcomes After Stopping Tyrosine Kinase Inhibitors Among Patients With Chronic Myeloid Leukemia: A Nonrandomized Clinical Trial

Importance

Tyrosine kinase inhibitors (TKIs) have been associated with improved survival of patients with chronic myeloid leukemia (CML) but are also associated with adverse effects, especially fatigue and diarrhea. Discontinuation of TKIs is safe and is associated with the successful achievement of treatment-free remission (TFR) for some patients.

Objective

To evaluate molecular recurrence (MRec) and patient-reported outcomes (PROs) after TKI discontinuation for US patients with CML.

Design, Setting, and Participants

The Life After Stopping TKIs (LAST) study was a prospective single-group nonrandomized clinical trial that enrolled 172 patients from 14 US academic medical centers from December 18, 2014, to December 12, 2016, with a minimum follow-up of 3 years. Participants were adults with chronic-phase CML whose disease was well controlled with imatinib, dasatinib, nilotinib, or bosutinib. Statistical analysis was performed from August 13, 2019, to March 23, 2020.

Intervention

Discontinuation of TKIs.

Main Outcomes and Measures

Molecular recurrence, defined as loss of major molecular response (BCR-ABL1 International Scale ratio >0.1%) by central laboratory testing, and PROs (Patient-Reported Outcomes Measurement Information System computerized adaptive tests) were monitored. Droplet digital polymerase chain reaction (ddPCR) was performed on samples with undetectable BCR-ABL1 by standard real-time quantitative polymerase chain reaction (RQ-PCR).

Results

Of 172 patients, 89 were women (51.7%), and the median age was 60 years (range, 21-86 years). Of 171 patients evaluable for molecular analysis, 112 (65.5%) stayed in major molecular response, and 104 (60.8%) achieved TFR. Undetectable BCR-ABL1 by either ddPCR or RQ-PCR at the time of TKI discontinuation (hazard ratio, 3.60; 95% CI, 1.99-6.50; P < .001) and at 3 months (hazard ratio, 5.86; 95% CI, 3.07-11.1; P < .001) was independently associated with MRec. Molecular recurrence for patients with detectable BCR-ABL1 by RQ-PCR was 50.0% (14 of 28), undetectable BCR-ABL1 by RQ-PCR but detectable by ddPCR was 64.3% (36 of 56), and undetectable BCR-ABL1 by both ddPCR and RQ-PCR was 10.3% (9 of 87) (P ≤ .001). Of the 112 patients in TFR at 12 months, 90 (80.4%) had a clinically meaningful improvement in fatigue, 39 (34.8%) had a clinically meaningful improvement in depression, 98 (87.5%) had a clinically meaningful improvement in diarrhea, 24 (21.4%) had a clinically meaningful improvement in sleep disturbance, and 5 (4.5%) had a clinically meaningful improvement in pain interference. Restarting a TKI resulted in worsening of PROs.

Conclusions and Relevance

In this study, TKI discontinuation was safe, and 60.8% of patients remained in TFR. Discontinuation of TKIs was associated with improvements in PROs. These findings should assist patients and physicians in their decision-making regarding discontinuation of TKIs. Detectable BCR-ABL1 by RQ-PCR or ddPCR at the time of TKI discontinuation was associated with higher risk of MRec; clinical application of this finding should be confirmed in other studies.

Trial Registration

ClinicalTrials.gov Identifier: NCT02269267.

First-generation vs second-generation tyrosine kinase inhibitors: which is best at diagnosis of chronic phase chronic myeloid leukemia?

In 2020, for the great majority of patients with chronic phase chronic myeloid leukemia (CML), life expectancy is unaffected by a diagnosis of CML because of the unparalleled efficacy of ABL-targeted tyrosine kinase inhibitors (TKIs) in halting disease progression. A wealth of choices exist for first-line treatment selection, including the first-generation TKI imatinib and the second-generation TKIs bosutinib, dasatinib, and nilotinib. How I select first-line therapy between first-generation and second-generation TKIs is discussed in the context of patient-specific CML disease risk, therapy-related risks, and treatment goals. Although rare, identifying patients with CML at higher risk for disease progression or resistance is important and influences first-line TKI selection. I review the impact of first-generation vs second-generation TKI selection on treatment response and outcomes; the ability to achieve, as well as the timing of, treatment-free remission; and the impact of specific TKIs on longer-term health.

Comprehensive Transcriptome Profiling of Cryptic CBFA2T3-GLIS2 Fusion-Positive AML Defines Novel Therapeutic Options: A COG and TARGET Pediatric AML Study

PURPOSE

A cryptic inv(16)(p13.3q24.3) encoding the CBFA2T3-GLIS2 fusion is associated with poor outcome in infants with acute megakaryocytic leukemia. We aimed to broaden our understanding of the pathogenesis of this fusion through transcriptome profiling.

EXPERIMENTAL DESIGN

Available RNA from children and young adults with de novo acute myeloid leukemia (AML; N = 1,049) underwent transcriptome sequencing (mRNA and miRNA). Transcriptome profiles for those with the CBFA2T3-GLIS2 fusion (N = 24) and without (N = 1,025) were contrasted to define fusion-specific miRNAs, genes, and pathways. Clinical annotations defined distinct fusion-associated disease characteristics and outcomes.

RESULTS

The CBFA2T3-GLIS2 fusion was restricted to infants <3 years old (P < 0.001), and the presence of this fusion was highly associated with adverse outcome (P < 0.001) across all morphologic classifications. Further, there was a striking paucity of recurrent cooperating mutations, and transduction of cord blood stem cells with this fusion was sufficient for malignant transformation. CBFA2T3-GLIS2 positive cases displayed marked upregulation of genes with cell membrane/extracellular matrix localization potential, including NCAM1 and GABRE. Additionally, miRNA profiling revealed significant overexpression of mature miR-224 and miR-452, which are intronic miRNAs transcribed from the GABRE locus. Gene-set enrichment identified dysregulated Hippo, TGFβ, and hedgehog signaling, as well as NCAM1 (CD56) interaction pathways. Therapeutic targeting of fusion-positive leukemic cells with CD56-directed antibody-drug conjugate caused significant cytotoxicity in leukemic blasts.

CONCLUSIONS

The CBFA2T3-GLIS2 fusion defines a highly refractory entity limited to infants that appears to be sufficient for malignant transformation. Transcriptome profiling elucidated several highly targetable genes and pathways, including the identification of CD56, providing a highly plausible target for therapeutic intervention.

The vascular bone marrow niche influences outcome in chronic myeloid leukemia via the E-selectin - SCL/TAL1 - CD44 axis

The endosteal bone marrow niche and vascular endothelial cells provide sanctuaries for leukemic cells. In murine chronic myeloid leukemia (CML) CD44 on leukemia cells and E-selectin on bone marrow endothelium are essential mediators for the engraftment of leukemic stem cells. We hypothesized that non-adhesion of CML-initiating cells to E-selectin on the bone marrow endothelium may lead to superior eradication of leukemic stem cells in CML after treatment with imatinib than imatinib alone. Indeed, here we show that treatment with the E-selectin inhibitor GMI-1271 in combination with imatinib prolongs survival of mice with CML via decreased contact time of leukemia cells with bone marrow endothelium. Non-adhesion of BCR-ABL1⁺ cells leads to an increase of cell cycle progression and an increase of expression of the hematopoietic transcription factor and proto-oncogene Scl/Tal1 in leukemia-initiating cells. We implicate SCL/TAL1 as an indirect phosphorylation target of BCR-ABL1 and as a negative transcriptional regulator of CD44 expression. We show that increased SCL/TAL1 expression is associated with improved outcome in human CML. These data demonstrate the BCR-ABL1-specific, cell-intrinsic pathways leading to altered interactions with the vascular niche via the modulation of adhesion molecules - which could be exploited therapeutically in the future.

The transcriptional regulator FUBP1 influences disease outcome in murine and human myeloid leukemia

The transcriptional regulator far upstream element binding protein 1 (FUBP1) acts as an oncoprotein in solid tumor entities and plays a role in the maintenance of hematopoietic stem cells. However, its potential function in leukemia is unknown. In murine models of chronic (CML) and acute myeloid leukemia (AML) induced by BCR-ABL1 and MLL-AF9, respectively, knockdown of Fubp1 resulted in prolonged survival, decreased numbers of CML progenitor cells, decreased cell cycle activity and increased apoptosis. Knockdown of FUBP1 in CML and AML cell lines recapitulated these findings and revealed enhanced DNA damage compared to leukemia cells expressing wild type FUBP1 levels. FUBP1 was more highly expressed in human CML compared to normal bone marrow cells and its expression correlated with disease progression. In AML, higher FUBP1 expression in patient leukemia cells was observed with a trend toward correlation with shorter overall survival. Treatment of mice with AML with irinotecan, known to inhibit topoisomerase I and FUBP1, significantly prolonged survival alone or in combination with cytarabine. In summary, our data suggest that FUBP1 acts as cell cycle regulator and apoptosis inhibitor in leukemia. We demonstrated that FUBP1 might play a role in DNA repair, and its inhibition may improve outcome in leukemia patients.

Glasdegib in combination with cytarabine and daunorubicin in patients with AML or high-risk MDS: Phase 2 study results

Glasdegib is a Hedgehog pathway inhibitor. This ongoing, open‐label, phase 2 study (NCT01546038) evaluated glasdegib plus cytarabine/daunorubicin in patients with untreated acute myeloid leukemia (AML) or high‐risk myelodysplastic syndromes (MDS). Patients received glasdegib 100 mg orally, once daily in continuous 28‐day cycles from day −3, with intravenous cytarabine 100 mg/m² on days 1‐7 and daunorubicin 60 mg/m² on days 1‐3. Patients in remission then received consolidation therapy (2‐4 cycles of cytarabine 1 g/m² twice daily on days 1, 3, 5 of each cycle), followed by maintenance glasdegib (maximum 6 cycles). Primary endpoint was complete remission (CR) in patients aged ≥55 years. Secondary endpoints included overall survival (OS), safety and outcome by mutational status. Patients had a median (range) age of 64.0 (27‐75) years, 60.0% were male, and 84.5% were white. In 69 evaluable patients, 46.4% (80% confidence interval [CI]: 38.7‐54.1) achieved investigator‐reported CR. Among patients ≥55 years old (n = 60), 40.0% (80% CI 31.9‐48.1) achieved CR. Among all 69 patients, median OS was 14.9 (80% CI 13.4‐19.3) months, with 12‐month survival probability 66.6% (80% CI 58.5‐73.4). The most common treatment‐related adverse events (≥50% patients) were diarrhea and nausea. There were no significant associations between mutational status (12 genes) and clinical response, suggesting potential benefit across diverse molecular profiles. Glasdegib plus cytarabine/daunorubicin was well tolerated and associated with clinical activity in patients with untreated AML or high‐risk MDS. A randomized phase 3 trial of glasdegib in combination with chemotherapy (7 + 3 schedule) is ongoing.

Design and rationale for the life after stopping tyrosine kinase inhibitors (LAST) study, a prospective, single-group longitudinal study in patients with chronic myeloid leukemia

BACKGROUND

Treatment of chronic myeloid leukemia with a tyrosine kinase inhibitor (TKI) offers significant improvements over previous treatments in terms of survival and toxicity yet nevertheless is associated with reduced health-related quality of life and very high cost. Several small studies from Europe and Australia suggested that discontinuing TKIs with regular monitoring was safe.

METHODS

The Life After Stopping TKIs (LAST) study is a large, U.S.-based study that aims to improve the evidence for clinical decision making regarding TKI discontinuation with monitoring in patients with chronic myeloid leukemia who have a deep molecular response to TKI therapy. The LAST study is a non-randomized, prospective, single-group longitudinal study of 173 patients. The co-primary objectives are to determine the proportion of patients who develop molecular recurrence (> 0.1% BCR-ABLIS) after discontinuing one of four TKIs (imatinib, dasatinib, nilotinib, or bosutinib) and to compare the patient-reported health status of patients before and after stopping TKIs. Outcomes are assessed at baseline and throughout the 36-month study follow-up period with a central laboratory used for blood samples. All samples with undetectable BCR-ABL are also examined using digital polymerase chain reaction, which is a more sensitive nanofluidic polymerase chain reaction system.

DISCUSSION

Because of their high cost and side effects, discontinuation of TKIs for patients with chronic myeloid leukemia who have a deep molecular response to TKI therapy is a promising approach to treatment. The LAST study is the largest U.S.-based TKI discontinuation study. It is the first to allow participation from patients on any of 4 first- and second-generation TKIs, includes a robust approach to measurement of clinical and patient-reported outcomes, and is using digital polymerase chain reaction to explore better prediction of safe discontinuation.

TRIAL REGISTRATION

This study was registered prospectively on October 21, 2014 and assigned trial number NCT02269267 .

Phase Ib Study of Glasdegib, a Hedgehog Pathway Inhibitor, in Combination with Standard Chemotherapy in Patients with AML or High-Risk MDS

Purpose: This open-label, multicenter, dose-finding, phase Ib study (NCT01546038) evaluated the safety, pharmacokinetics, pharmacodynamics, and clinical activity of the novel Hedgehog pathway Smoothened inhibitor glasdegib (PF-04449913) in patients (N = 52) with acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome (MDS).Experimental Design: Glasdegib 100 or 200 mg was administered orally, once daily in 28-day cycles, in combination with low-dose cytarabine (arm A) or decitabine (arm B) to newly diagnosed patients considered not suitable for standard induction chemotherapy, and in combination with cytarabine/daunorubicin (arm C) to fit patients. The study followed a standard 3+3 dose-escalation design. The primary endpoint was dose-limiting toxicity (DLT). Ten additional patients were enrolled in expansion cohorts of arms A (n = 23) and C (n = 22) to confirm the recommended phase II dose (RP2D).Results: No DLTs were observed in arms A and B; 1 DLT (grade 4 neuropathy) occurred in arm C. The most common treatment-related nonhematologic adverse events were mostly grades 1 and 2 in all arms. Muscle spasms, dysgeusia, and alopecia were generally mild. Overall, 16 patients (31%) achieved a complete remission (CR)/CR with incomplete blood count recovery. Note that 100 mg daily was selected as the RP2D for glasdegib in combination with standard chemotherapies in the absence of an estimated MTD in this setting.Conclusions: Treatment with glasdegib in combination with standard chemotherapy was generally well-tolerated and consistent with prior findings, warranting further evaluation of glasdegib-based combinations in patients with AML or high-risk MDS. Clin Cancer Res; 24(10); 2294-303. ©2018 AACR.

A machine learning approach to integrate big data for precision medicine in acute myeloid leukemia

Cancers that appear pathologically similar often respond differently to the same drug regimens. Methods to better match patients to drugs are in high demand. We demonstrate a promising approach to identify robust molecular markers for targeted treatment of acute myeloid leukemia (AML) by introducing: data from 30 AML patients including genome-wide gene expression profiles and in vitro sensitivity to 160 chemotherapy drugs, a computational method to identify reliable gene expression markers for drug sensitivity by incorporating multi-omic prior information relevant to each gene’s potential to drive cancer. We show that our method outperforms several state-of-the-art approaches in identifying molecular markers replicated in validation data and predicting drug sensitivity accurately. Finally, we identify SMARCA4 as a marker and driver of sensitivity to topoisomerase II inhibitors, mitoxantrone, and etoposide, in AML by showing that cell lines transduced to have high SMARCA4 expression reveal dramatically increased sensitivity to these agents.

Identification of markers of drug response is essential for precision therapy. Here the authors introduce an algorithm that uses prior information about each gene’s importance in AML to identify the most predictive gene-drug associations from transcriptome and drug response data from 30 AML samples.

miR-155 expression and correlation with clinical outcome in pediatric AML: A report from Children's Oncology Group

BACKGROUND

Aberrant expression of microRNA-155 (miR-155) has been implicated in acute myeloid leukemia (AML) and associated with clinical outcome.

PROCEDURE

We evaluated miR-155 expression in 198 children with normal karyotype AML (NK-AML) enrolled in Children's Oncology Group (COG) AML trial AAML0531 and correlated miR-155 expression levels with disease characteristics and clinical outcome. Patients were divided into quartiles (Q1-Q4) based on miR-155 expression level, and disease characteristics were then evaluated and correlated with miR-155 expression.

RESULTS

MiR-155 expression varied over 4-log10-fold range relative to its expression in normal marrow with a median expression level of 0.825 (range 0.043-25.630) for the entire study cohort. Increasing miR-155 expression was highly associated with the presence of FLT3/ITD mutations (P < 0.001) and high-risk disease (P < 0.001) and inversely associated with standard-risk (P = 0.008) and low-risk disease (P = 0.041). Patients with highest miR-155 expression had a complete remission (CR) rate of 46% compared with 82% in low expressers (P < 0.001) with a correspondingly lower event-free (EFS) and overall survival (OS) (P < 0.001 and P = 0.002, respectively). In a multivariate model that included molecular risk factors, high miR-155 expression remained a significant independent predictor of OS (P = 0.022) and EFS (0.019).

CONCLUSIONS

High miR-155 expression is an adverse prognostic factor in pediatric NK-AML patients. Specifically, high miR-155 expression not only correlates with FLT3/ITD mutation status and high-risk disease but it is also an independent predictor of worse EFS and OS.

CD98-Mediated Adhesive Signaling Enables the Establishment and Propagation of Acute Myelogenous Leukemia

Acute myelogenous leukemia (AML) is an aggressive disease associated with drug resistance and relapse. To improve therapeutic strategies, it is critical to better understand the mechanisms that underlie AML progression. Here we show that the integrin binding glycoprotein CD98 plays a central role in AML. CD98 promotes AML propagation and lethality by driving engagement of leukemia cells with their microenvironment and maintaining leukemic stem cells. Further, delivery of a humanized anti-CD98 antibody blocks growth of patient-derived AML, highlighting the importance of this pathway in human disease. These findings indicate that microenvironmental interactions are key regulators of AML and that disrupting these signals with targeted inhibitors such as CD98 antibodies may be a valuable therapeutic approach for adults and children with this disease.

Combined Population Dynamics and Entropy Modelling Supports Patient Stratification in Chronic Myeloid Leukemia

Modelling the parameters of multistep carcinogenesis is key for a better understanding of cancer progression, biomarker identification and the design of individualized therapies. Using chronic myeloid leukemia (CML) as a paradigm for hierarchical disease evolution we show that combined population dynamic modelling and CML patient biopsy genomic analysis enables patient stratification at unprecedented resolution. Linking CD34⁺ similarity as a disease progression marker to patient-derived gene expression entropy separated established CML progression stages and uncovered additional heterogeneity within disease stages. Importantly, our patient data informed model enables quantitative approximation of individual patients’ disease history within chronic phase (CP) and significantly separates “early” from “late” CP. Our findings provide a novel rationale for personalized and genome-informed disease progression risk assessment that is independent and complementary to conventional measures of CML disease burden and prognosis.

Tetraspanin 3 Is Required for the Development and Propagation of Acute Myelogenous Leukemia

Acute Myelogenous Leukemia (AML) is an aggressive cancer that strikes both adults and children and is frequently resistant to therapy. Thus, identifying signals needed for AML propagation is a critical step toward developing new approaches for treating this disease. Here, we show that Tetraspanin 3 is a target of the RNA binding protein Musashi 2, which plays a key role in AML. We generated Tspan3 knockout mice that were born without overt defects. However, Tspan3 deletion impaired leukemia stem cell self-renewal and disease propagation and markedly improved survival in mouse models of AML. Additionally, Tspan3 inhibition blocked growth of AML patient samples, suggesting that Tspan3 is also important in human disease. As part of the mechanism, we show that Tspan3 deficiency disabled responses to CXCL12/SDF-1 and led to defects in AML localization within the niche. These identify Tspan3 as an important regulator of aggressive leukemias and highlight a role for Tspan3 in oncogenesis.

Mesenchymal stromal cells derived from acute myeloid leukemia bone marrow exhibit aberrant cytogenetics and cytokine elaboration

Bone marrow-derived mesenchymal stromal cells (BM-MSCs) play a fundamental role in the BM microenvironment (BME) and abnormalities of these cells may contribute to acute myeloid leukemia (AML) pathogenesis. The aim of the study was to characterize the cytokine and gene expression profile, immunophenotype and cytogenetics of BM-MSCs from AML patients compared to normal BM-MSCs from healthy donors. AML BM-MSCs showed decreased monocyte chemoattractant protein-1 levels compared to normal BM-MSCs. AML BM-MSCs expressed similar β1 integrin, CD44, CD73, CD90 and E-cadherin compared to normal BM-MSCs. Cytogenetic analysis revealed chromosomal aberrations in AML BM-MSCs, some overlapping with and others distinct from their corresponding AML blasts. No significant difference in gene expression was detected between AML BM-MSCs compared to normal BM-MSCs; however, comparing the differences between AML and MSCs from AML patients with the differences between normal hematopoietic cells and normal MSCs by Ingenuity pathway analysis showed key distinctions of the AML setting: (1) upstream gene regulation by transforming growth factor beta 1, tumor necrosis factor, tissue transglutaminase 2, CCAAT/enhancer binding protein alpha and SWItch/Sucrose NonFermentable related, matrix associated, actin dependent regulator of chromatin, subfamily a, member 4; (2) integrin and interleukin 8 signaling as overrepresented canonical pathways; and (3) upregulation of transcription factors FBJ murine osteosarcoma viral oncogene homolog and v-myb avian myeloblastosis viral oncogene homolog. Thus, phenotypic abnormalities of AML BM-MSCs highlight a dysfunctional BME that may impact AML survival and proliferation.

Prognostic significance of NPM1 mutations in the absence of FLT3-internal tandem duplication in older patients with acute myeloid leukemia: a SWOG and UK National Cancer Research Institute/Medical Research Council report

PURPOSE

Younger patients with acute myeloid leukemia (AML) harboring NPM1 mutations without FLT3-internal tandem duplications (ITDs; NPM1-positive/FLT3-ITD-negative genotype) are classified as better risk; however, it remains uncertain whether this favorable classification can be applied to older patients with AML with this genotype. Therefore, we examined the impact of age on the prognostic significance of NPM1-positive/FLT3-ITD-negative status in older patients with AML.

PATIENTS AND METHODS

Patients with AML age ≥ 55 years treated with intensive chemotherapy as part of Southwest Oncology Group (SWOG) and UK National Cancer Research Institute/Medical Research Council (NCRI/MRC) trials were evaluated. A comprehensive analysis first examined 156 patients treated in SWOG trials. Validation analyses then examined 1,258 patients treated in MRC/NCRI trials. Univariable and multivariable analyses were used to determine the impact of age on the prognostic significance of NPM1 mutations, FLT3-ITDs, and the NPM1-positive/FLT3-ITD-negative genotype.

RESULTS

Patients with AML age 55 to 65 years with NPM1-positive/FLT3-ITD-negative genotype treated in SWOG trials had a significantly improved 2-year overall survival (OS) as compared with those without this genotype (70% v 32%; P < .001). Moreover, patients age 55 to 65 years with NPM1-positive/FLT3-ITD-negative genotype had a significantly improved 2-year OS as compared with those age > 65 years with this genotype (70% v 27%; P < .001); any potential survival benefit of this genotype in patients age > 65 years was marginal (27% v 16%; P = .33). In multivariable analysis, NPM1-positive/FLT3-ITD-negative genotype remained independently associated with an improved OS in patients age 55 to 65 years (P = .002) but not in those age > 65 years (P = .82). These results were confirmed in validation analyses examining the NCRI/MRC patients.

CONCLUSION

NPM1-positive/FLT3-ITD-negative genotype remains a relatively favorable prognostic factor for patients with AML age 55 to 65 years but not in those age > 65 years.

MicroRNA-150 expression induces myeloid differentiation of human acute leukemia cells and normal hematopoietic progenitors

In acute myeloid leukemia (AML) and blast crisis (BC) chronic myeloid leukemia (CML) normal differentiation is impaired. Differentiation of immature stem/progenitor cells is critical for normal blood cell function. MicroRNAs (miRNAs or miRs) are small non-coding RNAs that interfere with gene expression by degrading messenger RNAs (mRNAs) or blocking protein translation. Aberrant miRNA expression is a feature of leukemia and miRNAs also play a significant role in normal hematopoiesis and differentiation. We have identified miRNAs differentially expressed in AML and BC CML and identified a new role for miR-150 in myeloid differentiation. Expression of miR-150 is low or absent in BC CML and AML patient samples and cell lines. We have found that expression of miR-150 in AML cell lines, CD34+ progenitor cells from healthy individuals, and primary BC CML and AML patient samples at levels similar to miR-150 expression in normal bone marrow promotes myeloid differentiation of these cells. MYB is a direct target of miR-150, and we have identified that the observed phenotype is partially mediated by MYB. In AML cell lines, differentiation of miR-150 expressing cells occurs independently of retinoic acid receptor α (RARA) signaling. High-throughput gene expression profiling (GEP) studies of the AML cell lines HL60, PL21, and THP-1 suggest that activation of CEPBA, CEBPE, and cytokines associated with myeloid differentiation in miR-150 expressing cells as compared to control cells contributes to myeloid differentiation. These data suggest that miR-150 promotes myeloid differentiation, a previously uncharacterized role for this miRNA, and that absent or low miR-150 expression contributes to blocked myeloid differentiation in acute leukemia cells.

The prognostic significance of IRF8 transcripts in adult patients with acute myeloid leukemia

Interferon regulatory factor 8 (IRF8) is a transcription factor that plays a critical role in normal hematopoiesis, such that disruption of IRF8 activity promotes leukemogenesis. We and others have identified aberrant expression of IRF8 transcripts, including novel splice variants, in acute myeloid leukemia (AML), but studies have not investigated the prognostic significance of these transcripts. Therefore, we developed and optimized quantitative expression assays for both, the wild type, or the reference sequence (WT-IRF8) and novel splice variants (SV-IRF8). These assays were used to quantify IRF8 transcript levels in 194 adult patients with AML, and multivariate analyses investigated the prognostic significance of these expression levels. After adjusting for known prognostic factors, expression levels of WT- or SV-IRF8 transcripts were not significantly associated with complete responses or overall survival. However, increased expression of WT-IRF8 was associated with decreased relapse-free survival (RFS) in both univariate (P = 0.010) and multivariate (P = 0.019) analyses. Similarly, increased expression of SV-IRF8 was associated with a decreased RFS (univariate, P = 0.026 and multivariate, P = 0.021). These studies show for the first time that WT-IRF8 and SV-IRF8 are independent adverse prognostic factors for patients with AML. Additional studies are planned to examine the prognostic significance of IRF8 transcripts in other populations of AML patients.

Update on current monitoring recommendations in chronic myeloid leukemia: practical points for clinical practice

Excellent therapeutic options exist for the treatment of chronic-phase chronic myeloid leukemia (CML) patients. Therefore, managing CML patients has become a more common practice for many physicians. Most chronic-phase CML patients achieve durable cytogenetic and molecular responses on first-line tyrosine kinase inhibitor therapy. However, careful monitoring and assessment of adherence are essential for successful outcomes and to identify patients at risk for failing therapy. The European LeukemiaNet and National Comprehensive Cancer Network provide guidance and strategies for monitoring and managing patients treated with TKIs. These recommendations continue to evolve as approved treatment options expand to include second- and third-generation tyrosine kinase inhibitors. How measurements of response are defined and data supporting recent recommended changes to monitoring are reviewed here. These changes include increasing recognition of the importance of early response. The relevance of achieving deep molecular responses will also be addressed.

Abstract 146: MicroRNA-150 expression induces differentiation of myeloid leukemias

Blocked myeloid differentiation is a major feature of chronic myeloid leukemia (CML) disease progression and acute myeloid leukemia (AML). Normal myeloid differentiation is a tightly controlled process involving the coordinated action of specific transcription factors, which are dysregulated by chromosomal translocations, DNA mutations, epigenetic changes, and aberrant gene and microRNA (miRNA) expression in leukemias. Previously, we identified decreased miR-150 expression in CML and AML cell lines and primary cells when compared to normal bone marrow, and determined miR-150 expression is decreased in CML by the Bcr-Abl fusion protein. Furthermore, lentiviral expression of miR-150 in AML cell lines and primary CML patient samples induced myeloid differentiation as detected by CD11b expression, morphologic differentiation, and colony forming ability in methylcellulose, both in the absence and presence of the differentiating agents. In this study, we elucidated the targets responsible for miR-150 induced differentiation. Expression of the validated miR-150 target MYB, a transcription factor involved in blocking differentiation in progenitor cells, was only decreased in miR-150 expressing cells in the presence of differentiating agent all-trans retinoic acid (ATRA). Furthermore, lentiviral overexpression of MYB lacking miR-150 binding sites in the 3′-UTR partially decreased the CD11b expression in the presence and absence of ATRA in both control and miR-150 expressing HL60 cells. These results suggest additional miR-150 targets are involved in differentiation besides MYB. To identify additional miRNA-150 targets, we profiled changes in mRNAs associated with the RNA-induced silencing complex (RISC) using RNA-immunoprecipitation of Ago2 followed by microarray gene expression profiling in miR-150 versus control HL60 cells. Furthermore, although almost all functional investigations have focused on the mature strand, we have found that miR-150 and its partner star strand miR-150* are expressed at almost equal levels in normal myeloid hematopoietic cells, and are investigating the individual contributions of their separate targets in induction of differentiation. In conclusion, miR-150 expression promotes myeloid differentiation through targeting transcription factor MYB and additional targets, while downregulation of miR-150 in myeloid leukemias contributes to the block in differentiation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 146. doi:1538-7445.AM2012-146

Predicting relapse prior to transplantation in chronic myeloid leukemia by integrating expert knowledge and expression data

MOTIVATION

Selecting a small number of signature genes for accurate classification of samples is essential for the development of diagnostic tests. However, many genes are highly correlated in gene expression data, and hence, many possible sets of genes are potential classifiers. Because treatment outcomes are poor in advanced chronic myeloid leukemia (CML), we hypothesized that expression of classifiers of advanced phase CML when detected in early CML [chronic phase (CP) CML], correlates with subsequent poorer therapeutic outcome.

RESULTS

We developed a method that integrates gene expression data with expert knowledge and predicted functional relationships using iterative Bayesian model averaging. Applying our integrated method to CML, we identified small sets of signature genes that are highly predictive of disease phases and that are more robust and stable than using expression data alone. The accuracy of our algorithm was evaluated using cross-validation on the gene expression data. We then tested the hypothesis that gene sets associated with advanced phase CML would predict relapse after allogeneic transplantation in 176 independent CP CML cases. Our gene signatures of advanced phase CML are predictive of relapse even after adjustment for known risk factors associated with transplant outcomes.

The gamma catenin/CBP complex maintains survivin transcription in β-catenin deficient/depleted cancer cells

Previously, we demonstrated that survivin expression is CBP/β-catenin/TCF-dependent. Now, using NCI-H28 cells, which harbor a homozygous deletion of β-catenin, we demonstrate that survivin transcription can similarly be mediated by nuclear γ-catenin. ICG-001, a specific inhibitor of binding to the N-terminus of CBP, effectively attenuates survivin expression. We demonstrate that γ-catenin by binding to TCF family members and specifically recruiting the coactivator CBP drives survivin transcription particularly in β-catenin-deficient cells. We also examined the relative expression of γ-catenin and β-catenin in 90 cases of chronic myeloid leukemia (CML) in a published gene expression microarray data base. A statistically significant negative correlation between γ-catenin and β-catenin was found in AP/BC cases (-0.389, P = 0.006). Furthermore, in subsequent independent validation studies by qPCR in 28 CP and BC patients increased γ-catenin expression predominated in BC cases and was associated with concomitantly increased survivin expression. Gene expression was 3- and 6-fold greater in BC patients as compared to CP patients, for γ-catenin and survivin, respectively. Consistent with this observation, nuclear γ-catenin accumulation was evident in this population consistent with a potential transcriptional role. Combined treatment with imatinib mesylate (IM) and ICG-001 significantly inhibited colony formation in sorted CD34(+) CML progenitors (survivin(+)/γ-catenin(high)/β-catenin(low)) isolated from one BC and one AP patient resistant to IM. Therefore, we believe that the ability of ICG-001 to block both the CBP/γ-catenin interaction and the CBP/β-catenin interaction may have clinical significance in cancers in which γ-catenin plays a significant transcriptional role.

Regulation of myeloid leukaemia by the cell-fate determinant Musashi

Chronic myelogenous leukemia (CML) can progress from an indolent chronic phase to an aggressive blast crisis phase1 but the molecular basis of this transition remains poorly understood. Here we have used mouse models of CML2,3 to show that disease progression is regulated by the Musashi-Numb signaling axis4,5. Specifically, we find that chronic phase is marked by high and blast crisis phase by low levels of Numb expression, and that ectopic expression of Numb promotes differentiation and impairs advanced phase disease in vivo. As a possible explanation for the decreased levels of Numb in blast crisis, we show that NUP98-HOXA9, an oncogene associated with blast crisis CML6,7, can trigger expression of the RNA binding protein Musashi2 (Msi2) which in turn represses Numb. Importantly, loss of Msi2 restores Numb expression and significantly impairs the development and propagation of blast crisis CML in vitro and in vivo. Finally, we show that Msi2 expression is not only highly upregulated during human CML progression but is also an early indicator of poorer prognosis. These data show that the Musashi-Numb pathway can control the differentiation of CML cells, and raise the possibility that targeting this pathway may provide a new strategy for therapy of aggressive leukemias.

The effects of imatinib mesylate treatment before allogeneic transplantation for chronic myeloid leukemia

The impact of imatinib mesylate (IM) treatment for chronic myeloid leukemia (CML) on subsequent allogeneic transplantation is uncertain. To better understand this relationship, we retrospectively compared 145 patients with CML receiving IM for a minimum of 3 months before allogeneic hematopoietic cell transplantation (HCT) to 231 patients with CML who did not. IM treatment was associated with no increase in early hepatotoxicity or engraftment delay after HCT compared with the historical cohort. In addition, there was no statistically significant difference in the IM-treated cohort compared with the historical cohort with regard to overall survival, disease-free survival, relapse, and nonrelapse mortality. For chronic-phase (CP) patients, IM response prior to HCT was associated with post-HCT outcome. Patients who underwent transplantation in CP with a suboptimal response or a loss of response on IM had a statistically significant higher hazard of mortality when compared with CP patients who achieved a complete cytogenetic response (CCR) or major cytogenetic response (MCR) on IM (HR=5.31, 95% confidence interval [CI] 1.13-25.05, P=.03). These data indicate that pre-HCT IM is not associated with increased transplant-related morbidity (TRM) or poorer outcomes. However, patients with a suboptimal or loss of IM response before HCT do worse, suggesting a more aggressive disease course for these patients.

Randomized trial of allogeneic related bone marrow transplantation versus peripheral blood stem cell transplantation for chronic myeloid leukemia

Seventy-two chronic myeloid leukemia patients were enrolled as part of a larger randomized trial at 3 centers between March 1996 and July 2001 to undergo either HLA-matched related allogeneic bone marrow (BM) or filgrastim (granulocyte colony-stimulating factor)-mobilized peripheral blood stem cell (PBSC) transplantation. Forty patients received BM, and 32 patients received PBSCs. There was no statistically significant difference in the incidence of acute or chronic graft-versus-host disease (GVHD), overall survival, disease-free survival, or non-relapse-related mortality between patients receiving BM or PBSC transplants. The cumulative incidence of grade II to IV acute GVHD was 49% in BM and 55% in PBSC recipients ( P = .48). The cumulative incidence of clinical extensive chronic GVHD was 50% in BM and 59% in PBSC recipients ( P = .46). Among 62 chronic phase chronic myeloid leukemia patients, there was no significant difference in overall survival (87% versus 81%; P = .59), disease-free survival (80% versus 81%; P = .61), or non-relapse-related mortality (13% versus 19%; P = .60) by cell source (BM versus PBSCs). Among chronic phase patients, however, there was a trend toward a higher cumulative incidence of relapse at 3 years in BM recipients (7% versus 0%; P = .10) and a higher cumulative incidence of chronic GVHD in PBSC recipients (59% versus 40%; P = .11). The trend toward a higher relapse incidence in BM recipients persisted with a longer follow-up.

Monitoring bcr-abl by polymerase chain reaction in the treatment of chronic myeloid leukemia

The elucidation of the molecular biology of chronic myeloid leukemia (CML) has provided a paradigm for understanding leukemogenesis, targeted drug development, and disease monitoring at the molecular level. Minimal residual disease (MRD) monitoring by fluorescence in situ hybridization and polymerase chain reaction (PCR) has become an important tool in predicting relapse after allogeneic transplant, allowing for early intervention strategies such as donor lymphocyte infusion. MRD monitoring is important for assessment of disease status in patients who obtain a complete cytogenetic remission, and this approach is likely to play an important role in following patients to determine who will relapse on imatinib mesylate therapy. This review focuses primarily on MRD monitoring by PCR.