Pharmacodynamic effects in patients treated with 6 hour infusion of the demethylating agent 5-aza-2 ' deoxycytidine (decitabine)

Brown, R. et al. (2005) Pharmacodynamic effects in patients treated with 6 hour infusion of the demethylating agent 5-aza-2 ' deoxycytidine (decitabine). In: AACR/NCI/EORTC International Conference on Molecular Targets and Cancer Therapeutics, Philadelphia, Pennsylvania, November 14-18, 2005, 9071S-9072S.

Abstract

The DNA methyltransferase inhibitor 5-aza-2'deoxycytidine (decitabine) induces DNA demethylation. Recent clinical studies of decitabine as a single agent have used protracted or multiple repeat infusions, with the aim of maximising the biological effect. However these will be challenging schedules to use in practice, especially in trials where decitabine is combined with other modalities. We have examined whether a 6hr infusion of decitabine induces pharmacodynamic effects in surrogate tissues and tumours of patients in the context of a Phase I trial of decitabine/carboplatin combination. 32 patients with a range of advanced solid malignancy were treated with escalating doses of decitabine administered as 6h infusion on day 1 and 1h infusion of carboplatin AUC5 or AUC6 on day 8 of 28 day cycle. Pharmacodynamic (PD) analyses included: 5-methyl-2deoxycytidine levels by HPLC, MAGE1A CpG-island methylation by methylation specific PCR (MSP), foetal haemoglobin (HbF) expression by Western analysis and caspase-dependent cleavage of cytokeratin-18 by ELISA. Decitabine administered as a 6h infusion caused a decrease in levels of 5-methyl-2-deoxycytidine in peripheral blood mononuclear cells (PBMC) maximal at day 10 after treatment and which subsequently reversed. Maximal mean decrease in levels of 5-methyl-2-deoxycytidine in peripheral blood mononuclear cell (PBMC) DNA are 33% (n=3), 37% (n=10) and 47% (n=4) respectively for 45mg/m2, 90mg/m2 and 135mg/m2 decitabine. There is a good correlation between peak plasma levels of decitabine and AAC (area above the curve) for demethylation in PBMC DNA (R=0.64, p=0.007, n=17). The MAGE1A CpG-island is bi-allelically methylated in most normal tissues. Patients treated with decitabine show an increase in levels of demethylated MAGE1A CpG-island after 8 days in PBMC and buccal cells. Demethylation is again maximal over days 8-12 and returns to initial levels by day 22. Pyrosequencing of bisulphite modified DNA showed demethylation of MAGE1A in 2/6 tumour biopsies taken at day 10-12 on cycle 1, but there was less demethylation than in PBMC. Ongoing studies are examining methylation in tumours in subsequent cycles of treatment. Levels in lymphocytes of HbF (foetal haemoglobin, which is epigenetically silenced in adult tissue) increase 8-12 days after treatment of patients with 90mg/m2 decitabine and have returned to approximate starting levels by day 15. In subsequent cycles of treatment there is apparent accumulation of HbF levels, suggesting that repeat treatment of patients with decitabine is more effective than a single treatment in inducing HbF expression. Cytokeratin-18 is cleaved by caspases specifically during apoptosis and is released from dying cells into plasma. An increase in the level of cleaved cytokeratin-18 in plasma of patients (n=17) is observed 8-12 days after decitabine treatment. A 6h infusion of decitabine induces demethylation in surrogate and tumour samples. Demethylation is associated with gene re-expressionand induction of a marker of apoptosis. The level of demethylation observed is equivalent to previous reports using more protracted infusion protocols.

• Item Type: Conference Proceedings
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Plumb, Dr Jane and Tang, Dr Adrian and Appleton, Ms Kim and Brown, Prof Robert and McCormick, Mrs Carol
• Authors: Brown, R., Appleton, K., Plumb, J.A., McCormick, C., Lee, C., Barrett, S., Tang, A., Schaetzlein, A., Kaye, S.B., Judson, I., and McKay, H.J.
• College/School: College of Medical Veterinary and Life Sciences > School of Health & Wellbeing > Mental Health and Wellbeing; College of Medical Veterinary and Life Sciences
• Journal Name: Clinical Cancer Research
• Journal Abbr.: Clin. Cancer Res.
• Publisher: American Association for Cancer Research
• ISSN: 1078-0432
• ISSN (Online): 1557-3265