Submitted March 4, 2008
Accepted August 24, 2008
Stratification of paediatric ALL by in vitro cellular responses to DNA double strand breaks provides insight into the molecular mechanisms underlying clinical response
Eliot Marston, Victoria Weston, Jennifer Jesson, Esther Maina, Carmel McConville, Angelo Agathanggelou, Anna Skowronska, Katie Mapp, Katrin Sameith, Judith E Powell, Sarah Lawson, Pamela Kearns, Francesco Falciani, Malcolm Taylor, and Tatjana Stankovic*
CRUK Institute for Cancer Studies, Birmingham University, Birmingham, United Kingdom
Department of Haematology, Birmingham Children's Hospital, Birmingham, United Kingdom
Institute for Child Health, University of Birmingham, Birmingham, United Kingdom
School of Biosciences and Institute for Biomedical Research, University of Birmingham, Birmingham, United Kingdom
Department of Epidemiology and Public Health, University of Birmingham, Birmingham, United Kingdom
* Corresponding author; email: t.stankovic{at}bham.ac.uk.
The molecular basis of different outcomes in paediatric ALL remains poorly understood. We addressed the clinical significance and mechanisms behind in vitro cellular responses to ionising radiation (IR)-induced DNA double strand breaks in 74 paediatric ALL patients. We found an apoptosis-resistant response in 36% of patients characterised by failure to cleave caspases 3, 7, 9 and PARP1 by 24h hours after IR and an apoptosis-sensitive response with the cleavage of the same substrates in the remaining 64% of leukaemias. Resistance to IR in vitro was associated with poor early blast clearance at day 7 or 15 and persistent minimal residual disease (MRD) at day 28 of induction treatment.
Global gene expression profiling revealed abnormal up-regulation of multiple pro-survival pathways in response to IR in apoptosis-resistant leukaemias and differential post-transcriptional activation of the PI3-Akt pathway was observed in representative resistant cases. Importantly, pharmacological inhibition of selected pro-survival pathways sensitised apoptosis-resistant ALL cells to IR in vitro.
We suggest that abnormal pro-survival responses to DNA damage provide one of the mechanisms of primary resistance in ALL and that they should be considered as therapeutic targets in children with aggressive disease.
