Requirement for myeloid growth factors in the differentiation of acute promyelocytic leukaemia

A phase II study of azacitidine in combination with granulocyte-macrophage colony-stimulating factor as maintenance treatment, after allogeneic blood or marrow transplantation in patients with poor-risk acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS)

Relapse is the most common cause of treatment failure following allogeneic blood or marrow transplantation (alloBMT) for AML or MDS. Post-transplant maintenance therapies may prevent relapse. We conducted a phase II trial combining azacitidine (AZA) with GM-CSF in non-relapsed, post-transplant patients with AML or MDS. Patients received escalating doses of AZA to a maximum of 75 mg/m2 for 5 days per cycle for up to 12 cycles. GM-CSF was given on days 1-10 of each cycle. Eighteen patients were treated following non-myeloablative (17) and myeloablative (1) alloBMT for AML (61.1%), MDS (27.7%), or therapy-related myeloid neoplasm (11.1%). The majority of patients (72%) received their graft from an HLA-haploidentical donor. The treatment was well-tolerated with rare grade 3-4 hematologic toxicities. One patient suffered an exacerbation of GVHD. The 24-month relapse-free and overall survivals were 47 and 57%, respectively, with a median of 18.6 and 29 months.

Treatment of acute promyelocytic leukemia in older patients: recommendations of an International Society of Geriatric Oncology (SIOG) task force

Approximately one third of patients diagnosed with acute promyelocytic leukemia (APL) are above the age of sixty. It is important to ensure older adults receive optimal diagnosis and management since this subtype of acute myeloid leukemia - given appropriate treatment - is highly curable with lower risk of adverse events compared to other types of leukemia. Historically, older age has been a risk factor for early death and poorer overall survival. However, prospects have changed with the introduction of all-trans retinoic acid (ATRA) and arsenic trioxide (ATO). APL is curable in the majority of patients regardless of age, and the threshold of fitness that makes ATRA/ATO therapy possible is likely to be lower than for cytotoxic chemotherapy. APL frequently presents as a medical emergency and rapid diagnosis and intervention - typically involving referral to a specialist centre - is a major determinant of outcome. After diagnosis, management of APL in older adults presents particular challenges. Geriatric assessment, including evaluation of frailty, comorbidities and polypharmacy can assist in providing optimal supportive care for older adults during remission induction and may help individualize therapy in the post-remission phase. Here, we review the available evidence, highlighting areas of consensus, gaps in evidence and opportunities for research to enhance diagnosis, management and survivorship for older patients.

Gut Microbiota Species Can Provoke both Inflammatory and Tolerogenic Immune Responses in Human Dendritic Cells Mediated by Retinoic Acid Receptor Alpha Ligation

Dendritic cells are considered as the main coordinators of both mucosal and systemic immune responses, thus playing a determining role in shaping the outcome of effector cell responses. However, it is still uncovered how primary human monocyte-derived DC (moDC) populations drive the polarization of helper T (Th) cells in the presence of commensal bacteria harboring unique immunomodulatory properties. Furthermore, the individual members of the gut microbiota have the potential to modulate the outcome of immune responses and shape the immunogenicity of differentiating moDCs via the activation of retinoic acid receptor alpha (RARα). Here, we report that moDCs are able to mediate robust Th1 and Th17 responses upon stimulation by Escherichia coli Schaedler or Morganella morganii, while the probiotic Bacillus subtilis strain limits this effect. Moreover, physiological concentrations of all-trans retinoic acid (ATRA) are able to re-program the differentiation of moDCs resulting in altered gene expression profiles of the master transcription factors RARα and interferon regulatory factor 4, and concomitantly regulate the cell surface expression levels of CD1 proteins and also the mucosa-associated CD103 integrin to different directions. It was also demonstrated that the ATRA-conditioned moDCs exhibited enhanced pro-inflammatory cytokine secretion while reduced their co-stimulatory and antigen-presenting capacity thus reducing Th1 and presenting undetectable Th17 type responses against the tested microbiota strains. Importantly, these regulatory circuits could be prevented by the selective inhibition of RARα functionality. These results altogether demonstrate that selected commensal bacterial strains are able to drive strong effector immune responses by moDCs, while in the presence of ATRA, they support the development of both tolerogenic and inflammatory moDC in a RARα-dependent manner.

Differentiation therapy in poor risk myeloid malignancies: Results of companion phase II studies

Pre-clinical data in non-M3 AML supports the use of differentiation therapy, but clinical activity has been limited. Myeloid growth factors can enhance anti-leukemic activity of differentiating agents in vitro. We conducted companion phase II trials investigating sargramostim (GM-CSF) 125μg/m(2)/day plus 1) bexarotene (BEX) 300mg/m(2)/day or 2) entinostat (ENT) 4-8mg/m(2)/week in patients with MDS or relapsed/refractory AML. Primary endpoints were response after at least two treatment cycles and toxicity. 26 patients enrolled on the BEX trial had a median of 2 prior treatments and 24 enrolled on the ENT trial had a median of 1. Of 13 response-evaluable patients treated with BEX, the best response noted was hematologic improvement in neutrophils (HI-N) seen in 4 (31%) patients; none achieved complete (CR) or partial remission (PR). Of 10 treated with ENT, there was 1 (10%) partial remission (PR) and 2 (20%) with HI-N. The secondary endpoint responses of HI-N with each combination were accompanied by a numerical increase in ANC (BEX: 524 to 931 cells/mm(3), p=0.096; ENT: 578 to 1 137 cells/mm(3), p=0.15) without increasing marrow blasts. Shared grade 3-4 non-hematologic toxicities included febrile neutropenia, bone pain, fatigue, and dyspnea. GM-CSF plus either BEX or ENT are well tolerated in resistant and refractory MDS and AML and showed modest clinical and biologic activity, most commonly HI-N.

Unlocking the potential of retinoic acid in anticancer therapy

All-trans-retinoic acid (ATRA) is a physiologically active metabolite of vitamin A. Its antitumour activities have been extensively studied in a variety of model systems and clinical trials; however, to date the only malignancy responsive to ATRA treatment is acute promyelocytic leukaemia (APL) where it induces complete remission in the majority of cases when administered in combination with light chemotherapy and/or arsenic trioxide. After decades of studies, the efficacy of ATRA to treat other acute myeloid leukaemia (AML) subtypes and solid tumours remains poor. Recent studies directed to improve ATRA responsiveness in non-APL AML seem to indicate that the lack of effective ATRA response in these tumours may be primarily due to aberrant epigenetics, which negatively affect ATRA-regulated gene expression and its antileukaemic activity. Epigenetic reprogramming could potentially restore therapeutic effects of ATRA in all AML subtypes. This review discusses the current progresses in the understanding how ATRA can be utilised in the therapy of non-APL AML and other cancers.

Prostaglandin E2 induces growth inhibition, apoptosis and differentiation in T and B cell-derived acute lymphoblastic leukemia cell lines (CCRF-CEM and Nalm-6)

Despite advances in the treatment of ALL, in most patients long-term survival rates remain unsatisfactory. The objective of the present study was to investigate the anti-cancer effects of Prostaglandin E2 (PGE2) in two different ALL cell lines (CCRF-CEM (T-ALL) and Nalm-6 (B-ALL)). The anti-leukemic effects of PGE2 were also compared with two epigenetic compounds (trichostatin A and 5-aza-2'-deoxycytidine). MTT assay was used to assess growth inhibition by anti-cancer drugs in these cells. All three compounds were shown to induce apoptosis in both ALL cell lines using flow cytometry and Western blotting. To evaluate the differentiation induction by these agents, the expressions of CD19 and CD38 markers on Nalm-6 cell line and CD7 marker on CCRF-CEM cell line were assayed. Surprisingly, the flow cytometric analysis showed a significant increase in CD markers expression in response to PGE2 treatments. We, for the first time, provide evidences that PGE2 has anti-leukemic effects and induces differentiation at micromolar ranges in both T- and B-cell derived ALL cell lines. Since T-ALL cells are insensitive to current chemotherapies, these findings may help the designing of new protocols for T-ALL differentiation therapy in the future.

Differentiation therapy in poor risk myeloid malignancies: Results of a dose finding study of the combination bryostatin-1 and GM-CSF

PURPOSE

Pharmacologic differentiating agents have had relatively limited clinical success outside of the use of ATRA in acute promyelocytic leukemia and DNA methyltransferase inhibitors in myelodysplastic syndromes. The differentiating effects of such agents can be enhanced in combination with lineage-specific growth factors. We developed a dose finding trial to assess toxicity, differentiating activity, and clinical impact of the combination of bryostatin-1 and GM-CSF.

EXPERIMENTAL DESIGN

Patients with poor risk myeloid malignancies were eligible to enroll in a dose finding study of continuous infusion bryostatin-1 combined with a fixed dose of daily GM-CSF. Toxicities were graded per NCI CTC version 2.0 and pharmacokinetic and correlative study samples were obtained to assess the combination's clinical and biologic differentiating effects.

RESULTS

Thirty-two patients were treated with the combination therapy and the dose determined to be most suitable for study in a larger trial was continuous infusion broystatin-1 at 16μg/m(2) for 14 days and subcutaneous GM-CSF at 125μg/m(2) daily for 14 days every 28 days. Arthralgias and myalgias limited further dose escalation. Clinically, the combination impacted differentiation with improvement of absolute neutrophil counts (p=0.0001) in the majority of patients. Interestingly, there were two objective clinical responses, including a CR after a single cycle. Both the bryostatin-1 plasma concentrations and the correlative studies supported biologic activity of the combination at the doses where clinical responses were observed.

CONCLUSIONS

Combining growth factors with pharmacologic differentiating agents may increase their clinical effectiveness and further studies should focus on such combinations.

Differentiation therapy of leukemia: 3 decades of development

A characteristic feature of leukemia cells is a blockade of differentiation at a distinct stage in cellular maturation. In the 1970s and 1980s, studies demonstrating the capabilities of certain chemicals to induce differentiation of hematopoietic cell lines fostered the concept of treating leukemia by forcing malignant cells to undergo terminal differentiation instead of killing them through cytotoxicity. The first promising reports on this notion prompted a review article on this subject by us 25 years ago. In this review, we revisit this interesting field of study and report the progress achieved in the course of nearly 3 decades. The best proof of principle for differentiation therapy has been the treatment of acute promyelocytic leukemia with all-trans retinoic acid. Attempts to emulate this success with other nuclear hormone ligands such as vitamin D compounds and PPARgamma agonists or different classes of substances such as hematopoietic cytokines or compounds affecting the epigenetic landscape have not been successful on a broad scale. However, a multitude of studies demonstrating partial progress and improvements and, finally, the new powerful possibilities of forward and reverse engineering of differentiation pathways by manipulation of transcription factors support the continued enthusiasm for differentiation therapy of leukemia in the future.

Myeloablative allogeneic bone marrow transplant using T cell depleted allografts followed by post-transplant GM-CSF in high-risk myelodysplastic syndromes

Allogeneic blood and marrow transplantation (alloBMT) remains the only curative treatment for patients with myelodysplastic syndromes (MDS), but its application has been limited by the older age range of patients with this disease. T cell depletion decreases transplant-related toxicity related to graft-versus-host disease (GVHD), but does not improve overall survival because of increased risk for relapse and graft failure. Myeloid growth factors have been used to speed engraftment following alloBMT, but data suggest that they may also have anti-tumor properties. We treated 43 patients (median age 56) with MDS/AML with high-risk features using a myeloablative T cell depleted alloBMT followed by prolonged systemic GM-CSF. The current event-free survival at 1 and 3 years was 47% and 34%, respectively with a median follow-up of 22.8 months in surviving patients. The toxicities compared favorably with those seen using reduced intensity conditioning regimens and included grade III/IV GVHD (10%), graft failure (9%), and cumulative treatment-related mortality (28%). The cumulative incidence of relapse remained high at 38%; however, 3/10 patients receiving donor lymphocyte infusions achieved durable complete remissions. These results suggest that it is possible to maintain treatment intensity while minimizing toxicity in older, high-risk MDS patients.

Induction of acute lymphocytic leukemia differentiation by maintenance therapy

Despite extensive study in many malignancies, maintenance therapy has clinically benefited only two diseases: acute lymphocytic leukemia (ALL) and acute promyelocytic leukemia (APL). ALL maintenance therapy utilizes low-dose 6-mercaptopurine (6MP) and methotrexate (MTX), while maintenance in APL primarily consists of all-trans-retinoic acid (ATRA). 6MP and MTX as used in ALL are also now usually added to maintenance ATRA for APL, based on data suggesting an improved disease-free survival. Although the mechanism of action of MTX and 6MP as maintenance is unknown, low-dose cytotoxic agents are potent inducers of differentiation in vitro. Thus, we studied whether maintenance therapy in ALL, like ATRA in APL, may be inducing terminal differentiation of ALL progenitors. The APL cell line NB4, the ALL cell lines REH and RS4;11, and patients' ALL blasts were incubated with ATRA, 6MP, and MTX in vitro. All three drugs inhibited the clonogenic growth of the APL and ALL cell lines without inducing immediate apoptosis, but associated with induction of phenotypic differentiation. The three drugs similarly upregulated lymphoid antigen expression, while decreasing CD34 expression, on patients' ALL blasts. These data suggest that induction of leukemia progenitor differentiation plays an important role in the mechanism of action of maintenance therapy in ALL.

Tyrosine phosphorylation modulates binding preference to cyclin-dependent kinases and subcellular localization of p27Kip1 in the acute promyelocytic leukemia cell line NB4

We have investigated the role of tyrosine phosphorylation of the cyclin-dependent kinase (cdk) inhibitor p27Kip1 using the acute promyelocytic leukemia cell line NB4 together with granulocyte colony-stimulating factor (G-CSF). Short-term G-CSF stimulation resulted in a rapid tyrosine dephosphorylation of p27Kip1 accompanied by a change in its binding preferences to cdks. On G-CSF stimulation, p27Kip1 dissociated from cdk4 and associated with cdk2. Binding assays with recombinant p27Kip1 confirmed that tyrosine-phosphorylated p27Kip1 preferentially bound to cdk4, whereas unphosphorylated protein preferentially associated with cdk2. In addition, studies with p27Kip1 point mutations revealed a decisive role of Tyr88 and Tyr89 in binding to cdk4. Furthermore, phosphorylation of Tyr88 and Tyr89 was accompanied by strong nuclear translocation of p27Kip1. Taken together, this report provides the first evidence that tyrosine phosphorylation of p27Kip1 plays a crucial role in binding to cdks and its subcellular localization. Moreover, both effects are mediated by application of G-CSF.

Effects of imatinib and interferon on primitive chronic myeloid leukaemia progenitors

Imatinib has impressive activity against chronic myeloid leukaemia (CML), but does not appear to completely eradicate the disease. Although responses to interferon-alpha (IFN) are slower and less dramatic than those to imatinib, they can be durable even after discontinuation of the drug. Unlike imatinib, the specific mechanisms responsible for IFN's clinical activity in CML are unknown. We found that IFN induced a G1 cell cycle arrest, as well as terminal differentiation, of the CML cell line KT-1 and CML CD34+ cells from clinical specimens. Myeloid growth factors augmented the antileukaemic activity of IFN, and neutralising antibodies directed against myeloid growth factors inhibited IFN's antileukaemic activity. We next directly compared the effects of imatinib and IFN against differentiated and primitive CML progenitors from newly-diagnosed patients. Although less active against CML granulocyte-macrophage colony forming units than imatinib, IFN was significantly more toxic to primitive CML progenitors responsible for the maintenance of long-term cultures. Imatinib and IFN appear to have divergent effects on CML progenitors at different stages of maturation, with imatinib more active against differentiated CML progenitors and IFN more active against primitive CML progenitors. The different target cells for these agents may explain the disparities in the kinetics and durability of their clinical responses. At least part of the clinical effect of IFN in CML appears to result from its ability to differentiate primitive CML progenitors.

Early mitochondrial alterations in ATRA-induced cell death

All-trans retinoic acid (ATRA) induces differentiation and subsequent apoptosis in a variety of cell lines. Using the myeloid cell line P39, we show that ATRA disturbs mitochondrial functional activity long before any detectable signs of apoptosis occur. These early changes include diminished mitochondrial oxygen consumption, decreased calcium uptake by mitochondria and as a result, a lower mitochondrial matrix calcium concentration. Granulocyte colony-stimulating factor (G-CSF) increases mitochondrial respiration and calcium accumulation capacity and subsequently blocks ATRA-induced apoptosis. Nifedipine, a plasma membrane calcium channel blocker, inhibits apoptosis-related changes, such as the loss of the mitochondrial membrane potential and activation of caspases. Thus, the properties of ATRA and G-CSF to modulate mitochondrial respiration and intracellular calcium control are novel findings, which give insight into their precise molecular mode of action.