Functional DNA repair system analysis in haematopoietic progenitor cells using host cell reactivation

Deficiencies in individual DNA repair systems are involved in both de novo and therapy-related acute myeloid leukaemia (t-AML), as indicated by genetic markers involving nucleotide excision repair (NER gene polymorphisms), double-strand-break (DSB) or mismatch repair (microsatellite instability (MSI)). We modified a host cell reactivation (HCR) assay for functional DNA repair system analysis of living primary haematopoietic cells; 2 x 10(5) normal peripheral blood lymphocytes (PBLs) and cord blood CD34+ progenitor cells were cryopreserved, thawed and transfected with 75 250 ng luciferase reporter plasmid (pCMVLuc) using DEAE-dextran (0.1 mg/mL) in a transfection volume of 250 mu L. We obtained luciferase activities of similar to 300-fold above background in CD34+ progenitor cells and similar to 2000-fold in PBLs, thus rendering these cells applicable for DNA repair analysis. We then evaluated the NER (UV-irradiated pCMVLuc) and DSB repair capacity (linearized pCMVLuc) of normal lymphocytes and several leukaemic cell lineages. Kasumi-1 and HL-60 AML cells exhibited a reduced NER capacity compared to normal GM03715 lymphocytes, PBLs and CD34+ progenitor cells (6.2 +/- 0.9 %, 6.5 +/- 0.9% vs. 12.3 +/- 1.8 %, 13.5 +/- 0.7% and 13.5 +/- 2.0 %, respectively). Kasumi-1 AML cells exhibited a reduced DSB repair capacity compared to AG10107 and GM03715 normal lymphocytes as well as CEM acute T-cell lymphoblastic leukaemia cells (6.4 +/- 0.8% vs. 10.8 +/- 0.7 %, 27.3 +/- 1.1% and 20.5 +/- 1.6 %, respectively). The modified HCR assay can be used for functional DNA repair analysis in living cells of patients with pre- and post-leukaemic conditions as well as in leukaemic blasts to elucidate the role of DNA repair in de novo and t-AML leukaemogenesis and to determine the individual susceptibility to t-AML prior to chemotherapy.