Unraveling stem cell and progenitor subsets in autologous grafts according to methods of mobilization: implications for prediction of hematopoietic recovery.

BACKGROUND AIMS: In the autologous setting, granulocyte colony-stimulating factor (G-CSF) (G), or, when failing, G plus plerixafor (G+P), are common regimens for mobilization of stem cells into peripheral blood. To delineate mobilization effects on graft composition and hematopoietic recovery, we compared contents of stem cells and progenitor cells in products of G+P- and G patients. Paired samples of G+P patients and prior insufficient G mobilization were available for analyses. METHODS: Subset analyses of grafts were performed by flow cytometry and myeloid colony-forming assay. In search of new markers to ascertain graft quality, we determined the fractions of aldehyde dehydrogenase bright (ALDH(br)) cells. RESULTS: G grafts contained higher percentages of CD34+ cells, CD34+CD38- cells, and committed progenitors (CD34+CD38+) compared with G+P grafts. A detailed characterization of the mobilized CD34+ cell subset showed higher percentages of CD38- among the CD34+ cells of the G+P group (P = 0.032). In contrast, the CD34+ cell subset in G grafts was characterized by a higher percentage of ALDH(br) cells (P < 0.0001). Studying engraftment and day +100 graft function the G and G+P transplanted patients were comparable with respect to neutrophils, whereas in platelets they differed. In the prediction of engraftment and hematopoietic recovery, the dose of infused ALDH(br) cells correlated best to both platelet (r = 0.565, P = 0.002) and neutrophil reconstitution (r = 0.366, P = 0.06). CONCLUSIONS: Besides showing dissimilar distributions of CD34+CD38- cells and progenitors in G and G+P grafts, this study further designated ALDH(br) as a promising marker in determination and prediction of graft quality and hematopoietic recovery.

Influence of methylene tetrahydrofolate reductase polymorphisms and coadministration of antimetabolites on toxicity after high dose methotrexate.

BACKGROUND AND OBJECTIVE: Through interruption of maintenance treatment with 6-mercaptopurine (6MP), toxicity after high-dose methotrexate (HDMTX) may compromise the efficiency of the treatment of children with acute lymphocytic leukaemia (ALL). We investigated the influence of polymorphisms in the methylene tetrahydrofolate reductase (MTHFR) gene and coadministration of antimetabolites on post-HDMTX toxicity. METHODS: Toxicity was retrospectively analysed after 656 HDMTX courses administered to 88 paediatric ALL patients at a single treatment centre. RESULTS: High-dose methotrexate with high-intensity co-treatment (6MP 75 mg/m(2)/d + MTX 20 mg/m(2)/wk) was found associated with increased odds of haematological toxicity (OR's: 3.47-7.88; P's: <0.001), hepatic toxicity (OR = 6.91; P < 0.001), hospitalization with fever (OR = 2.2; P = 0.004) and interruption maintenance treatment (OR = 15.9; P < 0.001) compared to HDMTX with low-intensity co-treatment (6MP 25 mg/m(2)/d). Addition of cytarabine to the low-intensity co-treatment increased the odds of neutropenia (OR = 3.51; P = 0.002), thrombocytopenia (OR = 6.56; P < 0.001), hepatic toxicity (OR = 3.84; P = 0.012) and interruption of maintenance treatment (OR = 4.25; P = 0.002). Alterations in 6MP dose were associated with significant changes in toxicity. Dose reduction reduced the odds of haematological toxicity (OR's: 0.22-0.34; P's: <0.001-0.020), while dose increase increased the odds of haematological toxicity (OR's: 2.72-7.42; P's: 0.006-0.027), fever (OR = 2.65; P = 0.037) and interruption of maintenance treatment (OR = 3.04; P = 0.032). No convincing associations were found between the MTHFR C677T or A1298C polymorphisms and toxicity. CONCLUSION: Our findings demonstrate that toxicity after HDMTX is influenced by coadministrated antimetabolites, and modifiable by alterations in 6MP dose. Prevention of toxicity related withdrawals through 6MP dose reduction could be a way of increasing total dose intensity.

Platelet characteristics in patients with essential thrombocytosis.

BACKGROUND: Essential thrombocytosis (ET) is a myeloproliferative disorder characterized by an increased platelet count. ET is associated with an increased risk of thrombosis, and procoagulant features of the disease may include an increased number of reactive reticulated platelets and an increased aggregation potential. We aimed to explore the association between platelet count, platelet turnover, and platelet aggregation in patients with ET. METHODS: We included 24 ET patients who discontinued antiplatelet therapy prior to blood sampling. Reticulated platelets were assessed as immature platelet count (IPC) and immature platelet fraction by automated flow cytometry (Sysmex XE-5000). Platelet aggregation was investigated by impedance aggregometry (Multiplate® Analyzer) and aggregation potential by flow cytometry (NAVIOS). RESULTS: Our results showed that ET patients had increased IPC compared to healthy individuals (median 12.3 vs. median 6.9, P < 0.0001). Furthermore, a positive correlation between platelet count and impedance aggregation was demonstrated using arachidonic acid (r = 0.48, P = 0.02), thrombin-receptor-activating-peptide (r = 0.46, P = 0.03) and adenosine diphosphate (r = 0.56, P = 0.007) as agonists. Finally, an increased aggregation potential was demonstrated in ET patients compared to healthy individuals. CONCLUSIONS: The study showed that ET patients compared to healthy individuals have an increased amount of reticulated platelets and increased aggregation potential. These findings might in part explain the increased thromboembolic risk in patients with ET. © 2018 International Clinical Cytometry Society.