ATP binding cassette C1 (ABCC1/MRP1)-mediated drug efflux contributes to disease progression in T-lineage acute lymphoblastic leukemia

Purpose: In acute lymphoblastic leukemia (ALL), multidrug resistance is often mediated by AT- Pase Binding Cassette (ABC) proteins, which principally involve ABCC1 (multidrug resistance protein 1, MRP1) and ABCB1 (multidrug resistance 1, MDR1). However, direct comparisons between the differential effects of ABCC1 and ABCB1 have been difficult, since identical cell lines with differential expression of these transporters have not been developed. Experimental Design: In this study, we developed and compared the biological profiles of Jurkat cell lines that selectively over-expressed ABCC1 and ABCB1. Vincristine (VCR) plays an important role in the treatment of T-lineage ALL (T-ALL), and is often the first drug given to newly-diagnosed patients. Because of its importance in treatment, we provide descalating, sub-lethal doses of VCR to Jurkat cells, and extended our observations to expression profiling of newly diagnosed patients with T-ALL. Results: We found that VCR-resistant cells over-expressed ABCC1 nearly 30-fold. The calcein AM assay confirmed that VCR-resistant cells actively extruded VCR, and that ABCC1-mediated drug resistance conferred a different spectrum of multidrug resistance than other T-ALL induction agents. siRNA experiments that blocked ABCC1 export confirmed that VCR resistance could be reversed in vitro. Analyses of T-lymphoblasts obtained from 100 newly diagnosed T-ALL patients treated on Children’s Oncology Group Phase III studies 9404 and AALL0434 that induction failure could be could be partially explained by the over-expression of ABCC1 and ABCB1. Conclusions: Taken together, these results suggest that over-expression of ABC transporters plays a contributing role in mediating treatment failure in T-ALL, and underscore the need to employ alternate treatment approaches in patients for whom induction failed or for those with relapsed disease.

How old is too old? In vivo engraftment of human peripheral blood stem cells cryopreserved for up to 18 years-implications for clinical transplantation and stability programs

BACKGROUND Peripheral blood stem cells(PBSC)are commonly cryopreserved awaiting clinical use for hematopoietic stem cell transplant.Long term cryopreservation is commonly defined as five years or longer,and limited data exists regarding how long PBSC can be cryopreserved and retain the ability to successfully engraft.Clinical programs,stem cell banks,and regulatory and accrediting agencies interested in product stability would benefit from such data.Thus,we assessed recovery and colony forming ability of PBSC following long-term cryopreservation as well as their ability to engraft in NOD/SCID/IL-2 Rγnull(NSG)mice.AIM To investigate the in vivo engraftment potential of long-term cryopreserved PBSC units.METHODS PBSC units which were collected and frozen using validated clinical protocols were obtained for research use from the Cellular Therapy Laboratory at Indiana University Health.These units were thawed in the Cellular Therapy Laboratory using clinical standards of practice,and the pre-freeze and post-thaw characteristics of the units were compared.Progenitor function was assessed using standard colony-forming assays.CD34-selected cells were transplanted into immunodeficient mice to assess stem cell function.RESULTS Ten PBSC units with mean of 17 years in cryopreservation(range 13.6-18.3 years)demonstrated a mean total cell recovery of 88%±12%(range 68%-110%)and post-thaw viability of 69%±17%(range 34%-86%).BFU-E growth was shown in 9 of 10 units and CFU-GM growth in 7 of 10 units post-thaw.Immunodeficient mice were transplanted with CD34-selected cells from four randomly chosen PBSC units.All mice demonstrated long-term engraftment at 12 wk with mean34%±24%human CD45+cells,and differentiation with presence of human CD19+,CD3+and CD33+cells.Harvested bone marrow from all mice demonstrated growth of erythroid and myeloid colonies.CONCLUSION We demonstrated engraftment of clinically-collected and thawed PBSC following cryopreservation up to 18 years in NSG mice,signifying likely successful clinical transplantation of PBSC following long-term cryopreservation.