Submitted June 26, 2006
Accepted September 2, 2006
Characterisation of a progenitor cell population in childhood T cell Acute Lymphoblastic Leukaemia
Charlotte V Cox, Hannah M Martin, Pamela R Kearns, Paul Virgo, Roger S Evely, and Allison Blair*
Bristol Institute for Transfusion Sciences, University of Bristol, Bristol, UK
Dept of Cellular & Molecular Medicine, University of Bristol, Bristol, UK
Dept of Immunology, North Bristol NHS Trust, Bristol, UK
Bristol Haematology & Oncology Centre, Bristol, UK
* Corresponding author; email: allison.blair{at}nbs.nhs.uk.
A significant proportion of children with T-ALL continue to fail therapy, consequently characterisation of the cells that proliferate to maintain the disease should provide valuable information on the most relevant therapeutic targets. We have used in vitro suspension culture (SC) and nonobese diabetic/severe combined immune deficient (NOD/SCID) mouse assays to phenotypically characterise and purify T-ALL progenitor cells. Cells from 13 paediatric cases were maintained in vitro for at least 4 weeks and expanded in 8 cases. To characterise the progenitors, cells were sorted for expression of CD34 and CD4 or CD7 and the subfractions evaluated in vitro and in vivo. The majority of cells capable of long-term proliferation in vitro were derived from the CD34+/CD4- and CD34+/CD7- subfractions. Moreover, the CD34+/CD4- or CD7- cells were the only subfractions capable of NOD/SCID engraftment. These T-ALL cells successfully repopulated secondary and tertiary recipients with equivalent levels of engraftment, demonstrating self-renewal ability. The immunophenotype and genotype of the original leukaemia cells were preserved with serial passage in the NOD/SCIDs. These data demonstrate the long-term repopulating ability of the CD34+/CD4- and CD34+/CD7- subfractions in T-ALL and suggest that a cell with a more primitive phenotype was the target for leukaemic transformation in these cases.
