Epigenetic modifiers: basic understanding and clinical development

Direct and transgenerational impact on Daphnia magna of chemicals with a known effect on DNA methylation

The purpose of this study is to investigate (1) the induction of epigenetic effects in the crustacean Daphnia magna using DNA methylation as an epigenetic mark and (2) the potential stable transfer of such an epigenetic effect to non-exposed subsequent generations. Daphnids were exposed to chemical substances known to affect DNA methylation in mammals: vinclozolin, 5-azacytidine, 2'-deoxy-5-azacytidine, genistein and biochanin A. Effects on overall DNA cytosine methylation, body length and reproduction were evaluated in 21day experiments. Using a multi-generational experimental design these endpoints were also evaluated in the F(1) and F(2) generation of both exposed and non-exposed offspring from F(0) daphnids exposed to 5-azacytidine, genistein or vinclozolin. A reduction in DNA methylation was consistently observed in daphnids exposed to vinclozolin and 5-azacytidine. Only in organisms exposed to 5-azacytidine was this effect transferred to the two subsequent non-exposed generations. A concurrent reduction in body length at day 7 was observed in these treatments. For the first time, exposure to environmental chemicals was shown to affect DNA methylation in the parental generation of D. magna. We also demonstrated a transgenerational alteration in an epigenetic system in D. magna, which indicates the possibility of transgenerational inheritance of environment-induced epigenetic changes in non-exposed subsequent generations.

Clinical studies of histone deacetylase inhibitors

Over the last 5 years, a plethora of histone deacetylase inhibitors (HDACi) have been evaluated in clinical trials. These drugs have in common the ability to hyperacetylate both histone and nonhistone targets, resulting in a variety of effects on cancer cells, their microenvironment, and immune responses. To date, responses with single agent HDACi have been predominantly observed in advanced hematologic malignancies including T-cell lymphoma, Hodgkin lymphoma, and myeloid malignancies. Therefore, in this review we focus upon hematologic malignancies. Generally HDACi are well tolerated with the most common acute toxicities being fatigue, gastrointestinal, and transient cytopenias. Of note, few patients have been treated for prolonged periods of time and little is known about long-term toxicities. The use of the biomarker of histone hyperacetylation has been useful as a guide to target specificity, but generally does not predict for response and the search for more clinically relevant biomarkers must continue.

Phase I study of decitabine in combination with vorinostat in patients with advanced solid tumors and non-Hodgkin's lymphomas

PURPOSE: This phase I study evaluated the safety, tolerability, pharmacokinetics and preliminary efficacy of the combination of decitabine with vorinostat. PATIENTS AND METHODS: Patients with advanced solid tumors or non-Hodgkin's lymphomas were eligible. Sequential and concurrent schedules were studied. RESULTS: Forty-three patients were studied in 9 different dose levels (6 sequential and 3 concurrent). The maximum tolerated dose (MTD) on the sequential schedule was decitabine 10 mg/m(2)/day on days 1-5 and vorinostat 200 mg three times a day on days 6-12. The MTD on the concurrent schedule was decitabine 10 mg/m(2)/day on days 1-5 with vorinostat 200 mg twice a day on days 3-9. However, the sequential schedule of decitabine 10 mg/m(2)/day on days 1-5 and vorinostat 200 mg twice a day on days 6-12 was more deliverable than both MTDs with fewer delays on repeated dosing and it represents the recommended phase II (RP2D) dose of this combination. Dose-limiting toxicities during the first cycle consisted of myelosuppression, constitutional and gastrointestinal symptoms and occurred in 12/42 (29%) patients evaluable for toxicity. The most common ≥ grade 3 adverse events were neutropenia (49% of patients), thrombocytopenia (16%), fatigue (16%), lymphopenia (14%), and febrile neutropenia (7%). Disease stabilization for ≥ 4 cycles was observed in 11/38 (29%) evaluable patients. CONCLUSION: The combination of decitabine with vorinostat is tolerable on both concurrent schedules in previously treated patients with advanced solid tumors or non-Hodgkin's lymphomas. The sequential schedule was easier to deliver. The combination showed activity with prolonged disease stabilization in different tumor types.