Targeted therapies in myelodysplastic syndromes: ASH 2003 review

Bone marrow niches in myeloid neoplasms

Pathological phenotypes of myeloid neoplasms are closely related to genetic/chromosomal abnormalities of neoplastic cells whereas the bone marrow microenvironment, including stromal elements and hematopoietic stem cell niche cells, have a great influence on the differentiation/proliferation of both hematopoietic and neoplastic cells. The pathology of myeloid neoplasms might be generated through the interaction of hematopoietic (stem) cells and stromal cells. The present study aims to provide the morphological/functional aspects of the bone marrow environment in myeloid neoplasms. Among the myeloid neoplasms, myelodysplastic syndromes (MDS) exhibit significant and complex interactions between neoplastic cells and stromal cells. Hematopoietic cells in MDS are greatly influenced by macrophages/niche cells via several signaling pathways. As such, the pathological significance of cell proliferation, cell apoptosis, and anti‐apoptosis signals in the bone marrow of myeloid neoplasms, especially MDS bone marrow, will be discussed.

Immunotoxicity and biodistribution analysis of arsenic trioxide in C57Bl/6 mice following a 2-week inhalation exposure

In these studies the immunotoxicity of arsenic trioxide (ATO, As(2)O(3)) was evaluated in mice following 14 days of inhalation exposures (nose only, 3 h per day) at concentrations of 50 microg/m(3) and 1 mg/m(3). A biodistribution analysis performed immediately after inhalation exposures revealed highest levels of arsenic in the kidneys, bladder, liver, and lung. Spleen cell levels were comparable to those found in the blood, with the highest concentration of arsenic detected in the spleen being 150 microg/g tissue following the 1 mg/m(3) exposures. No spleen cell cytotoxicity was observed at either of the two exposure levels. There were no changes in spleen cell surface marker expression for B cells, T cells, macrophages, and natural killer (NK) cells. There were also no changes detected in the B cell (LPS-stimulated) and T cell (Con A-stimulated) proliferative responses of spleen cells, and no changes were found in the NK-mediated lysis of Yac-1 target cells. The primary T-dependent antibody response was, however, found to be highly susceptible to ATO suppression. Both the 50 microg/m(3) and 1 mg/m(3) exposures produced greater than 70% suppression of the humoral immune response to sheep red blood cells. Thus, the primary finding of this study is that the T-dependent humoral immune response is extremely sensitive to suppression by ATO and assessment of humoral immune responses should be considered in evaluating the health effects of arsenic containing agents.

Tumour necrosis factor-induced gene expression in human marrow stroma: clues to the pathophysiology of MDS?

Aberrant regulation of the tumour necrosis factor alpha gene (TNF) and stroma-derived signals are involved in the pathophysiology of myelodysplasia. Therefore, KG1a, a myeloid leukaemia cell line, was exposed to Tnf in the absence or presence of either HS-5 or HS-27a cells, two human stroma cell lines. While KG1a cells were resistant to Tnf-induced apoptosis in the absence of stroma cells, Tnf-promoted apoptosis of KG1a cells in co-culture experiments with stroma cells. To investigate the Tnf-induced signals from the stroma cells, we examined expression changes in HS-5 and HS-27a cells after Tnf exposure. DNA microarray studies found both discordant and concordant Tnf-induced expression responses in the two stroma cell lines. Tnf promoted an increased mRNA expression of pro-inflammatory cytokines [e.g. interleukin (IL)6, IL8 and IL32]. At the same time, Tnf decreased the mRNA expression of anti-apoptotic genes (e.g. BCL2L1) and increased the mRNA expression of pro-apoptotic genes (e.g. BID). Overall, the results suggested that Tnf induced a complex set of pro-inflammatory and pro-apoptotic signals in stroma cells that promote apoptosis in malignant myeloid clones. Additional studies will be required to determine which of these signals are critical for the induction of apoptosis in the malignant clones. Those insights, in turn, may point the way to novel therapeutic approaches.

Effect of cA2 Anti–Tumor Necrosis Factor-α Antibody Therapy on Hematopoiesis of Patients with Myelodysplastic Syndromes

PURPOSE

Tumor necrosis factor alpha (TNF-alpha) plays a prominent role in the pathophysiology of myelodysplastic syndromes (MDS). The aim of this study was to explore the biological and immunoregulatory effect of the treatment with the anti-tumor necrosis factor-alpha monoclonal antibody cA2 on bone marrow (BM) progenitor/precursor and stromal cells and lymphocyte subsets, as well as the clinical response in MDS patients.

EXPERIMENTAL DESIGN

Ten low-intermediate risk MDS patients received i.v. cA2 (3 mg/kg) at weeks 0, 2, 6, and 12. The number, survival, and clonogenic potential of BM progenitor/precursor cells, the hematopoiesis-supporting capacity of BM stromal cells, and the lymphocyte activation status were investigated in the patients at baseline and following treatment using flow cytometry, clonogenic assays, and long-term BM cultures (LTBMC). Clinical response was evaluated according to standardized criteria.

RESULTS

cA2 administration reduced the proportion of apoptotic and Fas+ cells in the CD34+ cell compartment (P = 0.0215 and P = 0.0344, respectively) and increased the clonogenic potential of BM mononuclear and CD34+ cells (P = 0.0399 and P = 0.0304, respectively) compared with baseline. The antibody reduced tumor necrosis factor-alpha levels in LTBMC supernatants (P = 0.0043) and significantly improved the hematopoiesis-supporting capacity of LTBMC adherent cells. The proportion of activated peripheral blood and BM T-lymphocytes decreased significantly after treatment, suggesting an immunomodulatory effect of cA2. Two patients displayed minor hematologic responses whereas the remaining patients displayed stable disease with no disease progression.

CONCLUSIONS

The encouraging biological insights from cA2 administration may be useful in conducting further clinical trials using cA2 for selected MDS patients, particularly those with evidence of immune-mediated inhibition of hematopoiesis.

Optimizing therapy with methylation inhibitors in myelodysplastic syndromes: dose, duration, and patient selection

Azacitidine (Vidaza, Pharmion Corp., Boulder, CO, USA) and decitabine (Dacogentrade mark, SuperGen, Inc., Dublin, CA, USA, and MGI Pharma, Inc., Bloomington, MN, USA) are DNA methyltransferase (DNMT) inhibitors that have clinical activity in patients with myelodysplastic syndromes. Mechanism-based laboratory studies suggest that clinical optimization of therapy with DNMT inhibitors needs to include optimizing intracellular drug uptake and maximizing drug exposure over time while still using lower doses to avoid cytotoxicity. Clinical studies suggest that increased dose intensity and multiple cycles of administration substantially increase response rates. Other strategies for optimizing the efficacy of DNMT inhibitor therapy also include identification of patients that are best qualified for treatment, and defining in vivo mechanisms of patient responses. In the future, combination strategies to increase gene reactivation and to take advantage of increased expression of target genes may be critical for achieving optimal results.

5-azacytidine and decitabine monotherapies of myelodysplastic disorders

OBJECTIVE

To review and differentiate the pharmacology, toxicology, pharmacokinetics, and results of major clinical trials of 5-azacytidine (5-AzaC) and 5-aza-2'-deoxycytidine (decitabine) therapy of myelodysplastic disorders.

DATA SOURCES

A PubMed/MEDLINE search was conducted (1966-October 2004) using the following terms: DNA methylation, myelodysplastic disorders, 5-azacytidine, and 5-aza-2'-deoxycytidine (decitabine). Additional data sources included bibliographies from identified articles and manufacturer information.

STUDY SELECTION AND DATA EXTRACTION

Clinical trials for the treatment of various malignancies by hypomethylating agents were selected from data sources. All published, major clinical trials evaluating 5-AzaC or decitabine in myelodysplastic disorders and transformed myeloid leukemia treatment were included.

DATA SYNTHESIS

Myelodysplastic disorders are a group of bone marrow stem cell hyperplasias and dysplasias that result in ineffective hematopoiesis. Myelodysplastic disorders and transformed leukemia have poor prognosis and minimal response to chemotherapy. DNA hypomethylating agents have been shown to improve overall response rates (increased neutrophil, leukocyte, and platelet counts), time to leukemic progression, and quality of life compared with supportive therapy. The incidence of the most common adverse effects (nausea, vomiting, myelosuppression) can be reduced by low-dose, continuous, or extended-interval infusion.

CONCLUSIONS

Since appropriate dosing schedules of decitabine are being investigated, comparison of the clinical effectiveness of 5-AzaC and decitabine would be premature at this time. DNA hypomethylating agents show promise as monotherapies of myelodysplastic disorders and transformed leukemia and may be useful as a component of combination chemotherapy of various malignancies.

Cell cycle arrest and apoptotic cell death in cultured human gastric carcinoma cells mediated by arsenic trioxide

AIM: To investigate the effect of arsenic trioxide on human gastric cancer cell line MKN45 with respect to both cytotoxicity and induction of apoptosis in vitro.

METHODS: MKN45 cells were treated with arsenic trioxide (As₂O₃) at the concentration of 1, 5, and 10 µmol/L, respectively, for three successive days. Cell growth and proliferation were observed by cell counting and trypan blue exclusion. Cytotoxicity of As₂O₃ was determined by MTT assay. Morphologic changes were studied with light microscopy. Flow cytometry was used to assay cell DNA distribution and apoptotic cells were confirmed with terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) and DNA electrophoresis.

RESULTS: The growth of MKN45 cells was significantly inhibited by As₂O₃ which was confirmed by colony-forming assay. After 7 d of culture with various concentrations of As₂O₃, colony-forming capacity of MKN45 cells decreased with As₂O₃ increment in comparison with that of control group. The inhibitory rate of colony-formation was 38.5%, 99.1%, and 99.5% when the concentration of As₂O₃ was 1, 5, and 10 μmol/L in culture medium, respectively. The cell number of a single colony in drug treatment groups was less than that of control group. The cell-killing rate of As₂O₃ to MKN45 cells was both dose- and time-dependent with an IC₅₀ of (11.05±0.25) µmol/L. After incubation in 10 μmol/L As₂O₃ for 24 h, the cell-killing rate was 27.1%, and it was close to 50% after 48 h. The results showed that As₂O₃ induced time- and dose-dependent apoptosis in MKN45 cells, blocked at G2/M phase. The apoptotic peak (sub-G1 phase) appeared and cell apoptotic rate in MKN45 cells was 18.3-32.5% after treatment by 10 μmol/L As₂O₃ for 48 h. The percentage of G2/M cell of the experimental groups was 2.0-5.0 times than that of the control group. Gel electrophoresis of DNA from cells treated with each concentration of As₂O₃ for 48 h revealed a “ladder” pattern, indicating preferential DNA degradation at the internucleosomal, linker DNA sections. TUNEL also demonstrated strand breaks in DNA of MKN45 cells treated with As₂O₃, while control cells showed negative labeling.

CONCLUSION: As₂O₃ can induce apoptosis of human gastric carcinoma cells MKN45, which is the basis of its effectiveness. It shows great potential in the treatment of gastric carcinoma.

Low-dose interleukin-11 in patients with bone marrow failure: update of the M. D. Anderson Cancer Center experience

BACKGROUND

Recombinant interleukin (IL)-11 is a thrombopoietic growth factor. The purpose of this study was to assess the toxicity, safety and efficacy of low-dose recombinant IL-11 in patients with bone marrow failure (BMF).

PATIENTS AND METHODS

Patients with BMF due to myelodysplastic syndromes (MDS), graft failure, chemotherapy or aplastic anemia (AA) were treated. Patients were required to have a platelet count of <20 x 10(9)/l, or a platelet count of <50 x 10(9)/l with an absolute neutrophil count <1 x 10(9)/l, or a hemoglobin value <10 g/dl. Treatment consisted of daily IL-11 at a dose of 10 mug/kg subcutaneously followed by a 2-week rest period. Two induction courses were given. Responders could receive maintenance therapy.

RESULTS

Thirty-three patients (MDS, n=14; AA, n=16; prolonged thrombocytopenia following stem cell transplantation or chemotherapy, n=3) were evaluable. Their median age was 58 years (range 5-85). Three patients (9%) had poor risk cytogenetics. Nine patients (27%) responded to IL-11 (six MDS, three AA). Of these, three patients treated with IL-11 alone (n=1) or IL-11 together with other growth factors (n=2) showed multilineage recovery. The median time to response was 0.9 months (range 0.3-11). Factors associated with higher response rates in univariate analysis were age >50 years (P=0.008), diagnosis of MDS versus AA (P=0.025) and creatinine level >1 mg/dl (P=0.0004). The median response duration was 3 months (range 1.4-34.5+). Amongst responders, the median increment in platelet count was 111 x 10(9)/l (range 43-165). The most common side-effects were grade 1-2 lower extremity edema, conjunctival injections and fatigue. Grade 3 toxicities included arrhythmia (n=1) and transient ischemic attack (n=1). Ten patients (30%) had no side-effects.

CONCLUSIONS

Low-dose IL-11 has activity in patients with BMF and is generally well tolerated.