Efficacy of RNA polymerase II inhibitors in targeting dormant leukaemia cells

BMC Clinical Pharmacology

Nigel Russell²  Claire Seedhouse²  Nicholas Boddy²  Abigail Whittall²  Francis Burrows³  Monica Pallis¹ 

[1] Academic Haematology, Clinical Sciences Building, Nottingham University Hospitals City Campus, Nottingham NG5 1PB, UK;University of Nottingham, Nottingham, UK;Tragara Pharmaceuticals, San Diego, USA

关键词: RNA polymerase II inhibitors;    Dormancy;    Leukemia;   

Others  :  860581
DOI  :  10.1186/2050-6511-14-32

 received in 2013-02-21, accepted in 2013-06-05,  发布年份 2013

【 摘 要 】

Background

Dormant cells are characterised by low RNA synthesis. In contrast, cancer cells can be addicted to high RNA synthesis, including synthesis of survival molecules. We hypothesised that dormant cancer cells, already low in RNA, might be sensitive to apoptosis induced by RNA Polymerase II (RP2) inhibitors that further reduce RNA synthesis.

Methods

We cultured leukaemia cells continuously in vitro in the presence of an mTOR inhibitor to model dormancy. Apoptosis, damage, RNA content and reducing capacity were evaluated. We treated dormancy-enriched cells for 48 hours with the nucleoside analogues ara-C, 5-azacytidine and clofarabine, the topoisomerase targeting agents daunorubicin, etoposide and irinotecan and three multikinase inhibitors with activity against RP2 - flavopiridol, roscovitine and TG02, and we measured growth inhibition and apoptosis. We describe use of the parameter 2 × IC₅₀ to measure residual cell targeting. RNA synthesis was measured with 5-ethynyl uridine. Drug-induced apoptosis was measured flow cytometrically in primary cells from patients with acute myeloid leukaemia using a CD34/CD71/annexinV gating strategy to identify dormant apoptotic cells.

Results

Culture of the KG1a cell line continuously in the presence of an mTOR inhibitor induced features of dormancy including low RNA content, low metabolism and low basal ROS formation in the absence of a DNA damage response or apoptosis. All agents were more effective against the unmanipulated than the dormancy-enriched cells, emphasising the chemoresistant nature of dormant cells. However, the percentage of cell reduction by RP2 inhibitors at 2 × IC₅₀ was significantly greater than that of other agents. RP2 inhibitors strongly inhibited RNA synthesis compared with other drugs. We also showed that RP2 inhibitors induce apoptosis in proliferating and dormancy-enriched KG1a cells and in the CD71^neg CD34^pos subset of primary acute myeloid leukaemia cells.

Conclusion

We suggest that RP2 inhibitors may be a useful class of agent for targeting dormant leukaemia cells.

【 授权许可】

   
2013 Pallis et al.; licensee BioMed Central Ltd.

【 图 表 】

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