CNS engraftment was seen in 18/23 pre-B ALL samples (78%). A consistent pattern of engraftment was observed with plaques of disease in the leptomeninges, relative sparing of the ventricles and complete absence of parenchymal infiltration. This implies ALL transit across the blood-CSF barrier rather than the blood-brain barrier – an important distinction, as leucocytes utilise distinct physiological trafficking mechanisms to cross these two barriers. To examine the frequency of cells with CNS-engrafting potential, intra-femoral transfer of 10 to 10,000 cells was performed. CNS engraftment was seen with as few as 10 initial cells. In addition, the ability to engraft the CNS was not restricted to any particular immunophenotypic compartment and was seen in CD19+CD10high, CD19+CD10low, CD19+CD20low, CD19+CD20high, CD19+CD34high, CD19+CD34low fractions. These data suggest that CNS engraftment potential is present at high-frequency in the bulk leukaemic population at diagnosis. To examine candidate trafficking molecules governing CNS entry, we investigated chemokine receptor expression on pre-B ALL blasts using quantitative PCR and flow cytometry. The chemokine receptors CXCR3, CXCR4 and CXCR7 were expressed by pre-B ALL but were not up-regulated in cells retrieved from the CNS compared to the bone marrow (BM).
In conclusion, in xenograft models of pre-B ALL, CNS engrafting potential is present at high frequency in patient diagnostic BM specimens and does not appear to be restricted to sub-clonal compartments. These findings have important implications for the design of risk-adapted CNS therapy. Firstly, our studies indicate that CNS entry is a common property of leukaemic blasts and therefore the current dogma of CNS-directed therapy for all patients appears to have a rational scientific basis. Secondly, it is unlikely that chemokine receptor expression profiling will be a useful biomarker for CNS disease in pre-B ALL. Finally, identifying factors that facilitate long-term survival of cells in the CNS (which may also enhance long-term survival in the bone marrow) may be a better therapeutic strategy than attempts to block cell entry.
|Number of pages||1|
|Publication status||Published - 5 Dec 2013|
|Event||American Society of Hematology (ASH) 55th Annual Meeting - New Orleans, United States|
Duration: 7 Dec 2013 → 10 Dec 2013
Conference number: 55th
- central nervous system
- lymphoblastic leukaemia