Pilot study of 5-azacytidine (5-AZA) and carboplatin (CBDCA) in patients with relapsed/refractory leukemia

The use of hypomethylating agents in the treatment of hematologic malignancies

Epigenetic alterations, such as DNA methylation and histone modifications, are abnormal in cancer cells, and the use of the hypomethylating agents 5-azacitidine and decitabine are important additions to our arsenal of active cancer drugs, especially for the treatment of the myelodysplastic syndromes and acute myeloid leukemia. Most effective are repeated cycles of the drugs given at doses much lower than originally tested. Typical overall response rates (complete responses + partial responses + hematologic improvement) for both drugs are in the range of 40 - 50%. These agents are generally very well tolerated, with myelosuppression being the major side effect. Postulated to work through hypomethylation of DNA causing induction of gene expression, the precise mechanism of action of these agents is not yet clear. Future studies are likely to combine these agents with other drugs like the histone deacetylase inhibitors that act in related pathways.

Perspectives of proteomics in acute myeloid leukemia

Acute myeloid leukemia (AML) is a frequent hematological malignancy. Despite enormous therapeutic efforts that range from various cytotoxic agents to allogeneic stem cell transplantation, overall survival of patients with AML remains unsatisfying. The poor survival rates are mainly due to therapy-related mortality, failure of induction chemotherapy and early relapses. Therefore, novel therapeutic agents that are more efficient and better tolerated are eagerly sought after. For existing therapeutic strategies, there is a lack of markers that are capable of reliably predicting prognosis or the therapeutic response prior to treatment. There is hope that elucidation of the AML-specific proteome will prompt the discovery of novel therapeutic targets and biomarkers in AML. Modern mass-spectrometry instrumentation has achieved excellent performance in terms of sensitivity, resolution and mass accuracy; however, so far, the contribution of proteomics to the care of patients with AML is virtually zero. This might be partly because mass spectrometry instrumentation and protein fractionation still lack true high-throughput capabilities with highest levels of reproducibility, thus hampering large-scale translational studies with clinical samples. Since mass-spectrometry instruments are very intricate devices, their successful operation will hinge on the willingness and ability of mass-spectrometry experts and clinical researchers to adopt new views, learn from each other and cooperate in order to ultimately benefit the patient suffering from AML. This review highlights some clinical problems circumventing the treatment of patients with AML. Furthermore, it provides a brief overview of the technical background of standard proteomics approaches and describes opportunities, challenges and pitfalls of proteomic studies with regards to AML.

A pharmacodynamic study of 5-azacytidine in the P39 cell line

OBJECTIVE

5-azacytidine (azacytidine), a DNA hypomethylating agent, was recently approved as the first therapeutic agent for the treatment of myelodysplastic syndromes. The present subcutaneous dosing schedule, 75 mg/m(2) for 7/28 days, is based on early clinical studies and may constitute a practical problem for patients. The present in vitro study aimed at evaluating the pharmacodynamics of azacytidine, thereby providing a rationale for clinical dose-finding studies.

METHODS

P39 cells were incubated with 0.1, 0.5, and 1 microM azacytidine daily for 24, 48, and 72 hours, followed by 48 hours in drug-free medium. The effects of azacytidine on cell growth, proliferation, apoptosis, cell cycle status, and promoter methylation of E-cadherin, ER, and HIC genes were studied.

RESULTS

Azacytidine decreased cell growth and proliferation, increased apoptosis, and affected cell cycle status in a dose-dependent manner. However, the exposure time, 24 to 72 hours, at doses between 0.5 and 1 microM, did not significantly affect any of these variables. Using first-order exponential pharmacokinetic model, we found that the effect of 1, 2, or 3 microM over 24 hours did not differ from that of 0.5 to 1 microM given over 48 to 72 hours. Induction of promoter hypomethylation was observed already after 24 hours of exposure with >or=0.5 microM azacytidine with no clear dose-effect relationship.

CONCLUSION

Our results indicate that optimal cellular effects of azacytidine might be achieved by shorter exposure times. The model provides information about the relation between azacytidine dose intensity and exposure time on malignant myeloid cells, which could serve as a rationale for further clinical development of practical, safe, and cost-effective dosing schedules.

Inhibitors of DNA methylation: beyond myelodysplastic syndromes

DNA methyltransferase (DNMT) inhibitors, azacitidine (Vidaza, Pharmion, Boulder, CO, USA) and decitabine (Dacogen; SuperGen Inc, Dublin, CA, USA, and MGI Pharma Inc, Bloomington, MN, USA), have had a significant impact on the treatment paradigm of myelodysplastic syndromes (MDSs), previously managed mainly by supportive care and hematopoietic-stem-cell transplantation. The positive clinical experience seen in MDS to date coupled with the persistent challenges faced in the treatment of other hematologic malignancies has served as the impetus for further exploration of the therapeutic value of DNMT inhibitors beyond MDS. In that respect, the majority of data for these agents are in the setting of acute myelogenous leukemia (AML). Experience with these agents in patients with refractory anemia with excess blasts in transformation (reclassified by the World Health Organization as AML) was also reported in the clinical trials submitted to the FDA for approval of azacitidine for MDS. Some use has also been described in chronic myelogenous leukemia and acute lymphocytic leukemia. Further studies are needed to clarify the appropriate dose and the number and duration of cycles in the treatment of leukemias, and to identify ideal candidates for therapy, explore the role of DNMT inhibitors in combination with other agents, especially histone deacetylase inhibitors, delineate differences between the commercially available agents, and establish the long-term safety of these agents. To this end, experience with DNMT inhibitors in hematologic malignancies other than MDS is reviewed in an effort to better understand the therapeutic potential of these agents and to define areas of future exploration in these settings.

Azacitidine; Erlotinib

The increasing complexity of cancer chemotherapy heightens the requirement that pharmacists be familiar with these highly toxic agents. This column will review various issues related to preparation, dispensing, and administration of cancer chemotherapy. It will also serve as a review of various agents, both commercially available and investigational, used to treat malignant diseases.

The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or reflecting the views of the US Department of the Army or the Department of Defense.

DNA methyltransferase inhibitors-state of the art

BACKGROUND

DNA methylation is the addition of a methyl group to the 5 position of cytosine. It is an epigenetic process with several effects, including chromatin structure modulation, transcriptional repression and the suppression of transposable elements. In malignancy, methylation patterns change, resulting in global hypomethylation with regional hypermethylation. This can lead to genetic instability and the repression of tumor suppressor genes.

DESIGN

A review of the DNA methyltransferase inhibitor literature was conducted.

RESULTS

DNA methylation inhibitors have demonstrated the ability to inhibit hypermethylation, restore suppressor gene expression and exert antitumor effects in in vitro and in vivo laboratory models. Four inhibitors, which are analogs of the nucleoside deoxycitidine, have been clinically tested: 5-azacytidine, 5-aza-2'-deoxycytidine, 1-beta-D-arabinofuranosyl-5-azacytosine and dihydro-5-azacytidine. The first two have demonstrated encouraging antileukemic activity but little activity in solid tumors, while the latter two are no longer under study due to lack of efficacy. A fifth agent, MG98, is an antisense oligodeoxynucleotide directed against the 3' untranslated region of the DNA methyltransferase-1 enzyme mRNA, and is now under phase II study.

CONCLUSIONS

While some positive clinical results with DNA methyltransferase inhibitors have been seen, a definitive clinical role for these agents will most likely require combination therapy, and good phase III studies are needed.

Continuous-infusion carboplatin in combination with idarubicin or mitoxantrone for high-risk acute myeloid leukemia: a randomised phase II study

Fifty-three patients of median age 66 years (39 patients > 60 yrs), including 5 with FAB unclassified or secondary acute myeloid leukemia (AML) at diagnosis, 14 with resistant AML, 19 in first and 15 in subsequent relapse, were treated with carboplatin (CBP), 200 mg/m2/day, as a continuous infusion, (days 3 to 7) with mitoxantrone (MIT) or idarubicin (IDA), (12 mg/m2/day) as an i.v. bolus, on days 1 to 3. Results were evaluated after one induction course. Overall, 15 patients (28% [95% confidence interval (CI), 17-42%], 8/28 with IDA and 7/25 with MIT) achieved complete remission (CR). There was no statistical difference between IDA and MIT arms. Fourty-nine percent (95% CI, 35-63%) had resistant disease (53% IDA versus 44% MIT respectively) and 23% (95% CI, 12-36%) died from toxicity (18% IDA versus 28% MIT). Median durations of neutrophils less than 0.5 x 10(9)/l and platelet counts less than 20 x 10(9)/l were 32 and 32 days respectively in the IDA arm and 31 and 26 days respectively in the MIT arm. Severe toxicity included infections (45%), diarrhea (21%), bleeding (9%), vomiting (7%), hyperbilirubinemia (6%), mucositis (4%) (no statistical difference was seen between both arms). Nephrotoxicity was observed in only one case in the IDA arm. Cardiac toxicity included reversible pulmonary oedema in one patient in the IDA arm. No severe ototoxicity was noted. CR patients received maintenance courses with 3 days of CBP and one day of IDA or MIT. Median survival was 2 months (range, 1-30+ months) and 2.5 months (range, 0.5-19.5 months), and median disease-free survival (DFS) 2 months (range, 1-30+ months) and 2.5 months (range, 1-14 months) in the IDA and MIT arms respectively. We conclude that CBP at a cumulative dosage of 1 g/m2 together with intercalating agents (IDA/MIT) has antileukemic efficacy in elderly patients.

Effects of 5-azacytidine and butyrate on differentiation and apoptosis of hepatic cancer cell lines

OBJECTIVE

To determine the cellular effects of 5-azacytidine (5-azaC) and sodium butyrate on two human liver cancers, HepG2 and Hep3B.

SUMMARY BACKGROUND DATA

Primary liver cancer is a significant health problem; treatment options are limited and prognosis is poor. Recent studies have focused on the role that programmed cell death (i.e., apoptosis) plays in both normal and neoplastic growth: certain genes can either suppress (e.g., Bcl-2, Bcl-xL) or promote (e.g., Bik, Bax, Bak) apoptosis. The identification of novel agents targeted to specific molecular pathways may be beneficial in the treatment of this disease.

METHODS

Human liver cancer cell lines HepG2 and Hep3B were treated with 5-azaC alone, butyrate alone, or 5-azaC and butyrate. Morphologic and proliferative changes were assessed by light microscopy and 5-bromo-2'-deoxyuridine staining; flow cytometry was used to determine cell cycle characteristics. Apoptosis was assessed by DNA laddering and the in situ apoptosis detection assay using the TdT-mediated dUTP nick end labeling method. In addition, total RNA and protein were analyzed by ribonuclease protection and Western blot, respectively, to assess changes in the expression of apoptosis-related genes.

RESULTS

Treatment with either 5-azaC or butyrate inhibited cell growth and induced apoptosis in both HepG2 and Hep3B cells; the combination of 5-azaC and butyrate was not more effective than either agent alone. 5-azaC alone resulted in a more differentiated-appearing morphology and G2 cell cycle arrest in both cell lines. Treatment with 5-azaC or butyrate affected the expression levels of proteins of the Bcl-2 family.

CONCLUSIONS

Both 5-azaC and butyrate induced apoptosis in the HepG2 and Hep3B liver cancer cells; 5-azaC treatment alone produced G2 arrest in both cell lines. Proteins of the Bcl-2 family may play a role in the cellular changes that occur with treatment, but further studies are required to define this potential role. Products of the apoptotic pathway may prove to be useful therapeutic targets in the treatment of hepatic cancers.