BACKGROUND:Neutropenia is common after kidney transplantation and is associated with an increased incidence of infections. Drug toxicities are the main causes of posttransplant neutropenia (PTN), mainly related to immunosuppressive drugs as mycophenolic acid (MPA) and anti-infectious agents, but some PTN remain unexplained.METHODS:Between January 2012 and January 2013, cultures of autologous granulocytic progenitors from bone marrow aspirate were performed in two patients with unexplained severe neutropenia.RESULTS:Both patients' serum inhibited granulocytic differentiation while granulocytic differentiation was normal with the control serum. Similar inhibition of differentiation of granulocytic progenitors from a control marrow was observed with the patients' serum as compared with the control serum. Moreover, in both cases intravenous immunoglobulins allowed full neutrophil count recovery. Other usual etiologies of acquired neutropenia including systemic drug toxicity, infection, and autoimmune disease were excluded. As frequently observed in adult immune neutropenia, granulocyte autoantibodies were absent in both cases. Owing to biological and clinical results, we concluded that an autoimmune mechanism was responsible for neutropenia. The levels of MPA, which is known to interact with tacrolimus, were not measured in our patients. However, the persistence of neutropenia more than 70 days after withdrawal of MPA did not support this hypothesis.CONCLUSION:Autoimmune neutropenia should be considered in kidney transplant recipients in case of persistent unexplained neutropenia as it allows effective treatment and avoids the withdrawal of important immunosuppressive and anti-infectious treatments.

Clonal analysis of erythroid progenitors suggests that pegylated interferon α-2a treatment targets JAK2 V617F clones without affecting TET2 mutant cells

The JAK2 617V>F mutation is frequent in polycythemia vera (PV) and essential thrombocythemia (ET). Using quantitative polymerase chain reaction (PCR), we found that high levels of JAK2 617V>F in PV correlate with increased granulocytes and high levels of hemoglobin and endogenous erythroid colony formation. We detected normal progenitors and those that were heterozygous or homozygous for the mutation by genotyping ET and PV clonal immature and committed progenitors. In PV patients, we distinguished homozygous profiles with normal, heterozygous, and homozygous progenitors from heterozygous profiles with only heterozygous and normal progenitors. PV patients with a heterozygous profile had more mutated, committed progenitors than did other PV and ET patients, suggesting a selective amplification of mutated cells in the early phases of hematopoiesis. We demonstrated that mutated erythroid progenitors were more sensitive to erythropoietin than normal progenitors, and that most homozygous erythroid progenitors were erythropoietin independent. Moreover, we observed a greater in vitro erythroid amplification and a selective advantage in vivo for mutated cells in late stages of hematopoiesis. These results suggest that, for PV, erythrocytosis can occur through two mechanisms: terminal erythroid amplification triggered by JAK2 617V>F homozygosity, and a 2-step process including the upstream amplification of heterozygous cells that may involve additional molecular events.

Purpose: Patients with adult acute myeloid leukemia (AML) with intermediate cytogenetics remain a heterogeneous group with highly variable individual prognoses. New molecular markers could help to refine cytogenetic stratification. Experimental Design: We assessed P-glycoprotein (Pgp) activity and Flt3 internal tandem duplication (ITD+) because of their known prognostic value and because they might lead to targeted therapy. We did a multivariate analysis on 171 patients with adult AML treated in the European Organization for Research and Treatment of Cancer protocols. Results: ITD+ and high Pgp activity (Pgp+) were found in 26 of 171 (15%) and 55 of 171 (32%) of all patients, respectively. ITD and Pgp activities were negative in 94 of 171 (55%, Pgp−ITD− group), mutually exclusive in 73 of 171 (43%, Pgp−ITD+ and Pgp+ITD− groups), and only 4 of 171 (2%, Pgp+ITD+ group) patients were positive for both. In multivariate analyses, Pgp+ITD+ (P < 0.0001) and age (P = 0.0022) were independent prognostic factors for the achievement of complete remission (CR). Overall survival (OS), CR achievement (P < 0.0001), WHO performance status (P = 0.0007), and Pgp+ITD+ status (P = 0.0014) were also independent prognostic factors. In 95 patients with intermediate cytogenetics, the CR rates of ITD+ patients were 40% versus 62% for ITD− (P = 0.099) and 41% versus 67% (P = 0.014) for Pgp+ versus Pgp− patients. In the Pgp−ITD− group (41 of 95), CR rates were 70% versus 44% for others (P = 0.012), OS achieved 48% versus 16% (P < 0.0001) and disease-free survival was 56% versus 27% (P = 0.024), respectively. Furthermore, the OS curves of the intermediate cytogenetics-Pgp−ITD− group were not significantly different from the favorable cytogenetic group. Conclusion: Flt3/ITD and Pgp activity are independent and additive prognostic factors which provide a powerful risk classification that can be routinely used to stratify the treatment of patients with intermediate cytogenetic AML. ITD+ and Pgp+ patients should be considered for targeted therapy.

Adult acute myeloid leukemia (AML) with intermediate cytogenetic remains a very heterogeneous group of patients with highly variable individual prognosis. Emerging data suggest that some molecular markers could help to refine cytogenetic stratification. Here we focused on ABCB1 (MDR1/Pgp) ATP-binding cassette transporter activity and fms-like tyrosine kinase mutations (Flt3/ITD) because their individual prognosis value is well demonstrated and because they may lead to targeted therapy. Therefore we assessed Pgp activity using JC-1 probe and Flt3 exon 14 mutational status by standard PCR and realised a multivariate analysis in 171 adult AML patients treated in the EORTC protocols. Flt3/ITD (ITD+) and high Pgp activity (Pgp+) were found in 26/171 (15%) and 55/171 (32%) of the patients, respectively. The repartition was remarkable in that, as defined with our criteria, both were negative in 94/171 (55%, Pgp-ITD- group) or mutually exclusive in 73/171 (43%, Pgp-ITD+ and Pgp+ITD- groups) and only 4/171 (2%, Pgp+ITD+ group) were positive for both. In univariate analysis complete remission (CR) rates for ITD+ were 38% vs 61% for ITD- patients (p=0.034) and 47% vs 62% (p=0.06) for Pgp+ vs Pgp- patients. Individually, both parameters were strong predicators for overall survival (OS) (p=0,02) but not for disease free survival. In multivariate analysis Pgp+ITD+ (p<0.0001) and age (p=0.0022) were independent prognostic factors for CR achievement. For OS, CR achievement (p<0.0001), WHO performance status (p=0.0007) and Pgp+ITD+ (p=0.0014) were also independent prognostic factors. In 98 patients with intermediate cytogenetic CR rates for ITD+ were 40% vs 62% for ITD- patients (p=0.099) and 41% vs 67% (p=0.014) for Pgp+ vs Pgp- patients. In the Pgp-ITD- group (47/98 patients), CR rate was 70% vs 44% for others (p= 0.012). The 4 years OS achieved 48% vs 16% (p<0.0001) and DFS was 56% versus 27% (p=0.024). Furthermore, OS curves of the intermediate cytogenetic-Pgp-ITD- group were not significantly different from the favorable cytogenetic group. In conclusion Flt3-ITD and P-gp activity are independent and additive prognostic factors, which provide a powerful risk classification that can be used to stratify the treatment of intermediate cytogenetic AML patients.

The diagnosis of polycythemia vera (PV) is currently based on clinical and biological criteria defined either by the World Health Organization (WHO) or the Polycythemia Vera Study Group (PVSG).1, 2 Both of these classifications use clinical and biological markers organized in major and minor criteria, allowing to diagnose a PV when a define combination of major and minor criteria is present. Recently, a somatic point mutation of the tyrosine kinase JAK2 (JAK2 V617F) has been described in about 80% of PV patients as well as 30% of essential thrombocythemia (ET) and 50% of idiopathic myelofibrosis (IMF)3, 4, 5, 6 and several in vitro and in vivo experiments demonstrated that this mutation of JAK2 was the molecular event at the origin of PV.3 It was therefore tempting to use the detection of JAK2V617F as a diagnostic test for erythrocytosis. Such an attitude supposes the development of other techniques than sequencing, as this latter is time consuming and not always feasible in hematology laboratories. We thus compared sequencing with two techniques of real-time PCR-based mutation detection (one using the LightCycler® instrument, the other the Taqman® ABI Prism 7500), for the efficiency to detect the JAK2 V617F mutation in 119 samples from patients with suspicion of myeloproliferative disorder (MPD). The three techniques were equivalent in all samples but one, where sequencing failed to detect the mutation revealed by both LightCycler® and Taqman® technologies. To evaluate the sensitivity of these techniques, we tested serial dilutions of the homozygously mutated HEL cell line DNA in the nonmutated TF-1 cell line DNA, and serial dilutions of the genomic DNA from a patient homozygous for the JAK2 V617F mutation in normal DNA. Sequencing failed to detect the mutated allele under 5% of HEL cell line DNA diluted in TF-1 cell line DNA, and under 10% of the homozygously mutated patient's DNA diluted in normal DNA. The sensitivity of LightCycler® and Taqman® techniques were equivalent, slightly higher than sequencing, reaching 0.5–1% of HEL cell line DNA diluted in TF-1 cell line DNA (Figure 1), and 2–4% of a homozygously mutated patient's DNA diluted in normal DNA.

Polycythemia vera (PV) is a myeloproliferative disorder arising in a multipotent hematopoietic stem cell. The pathogenesis of PV remains poorly understood; however, the biologic hallmark of this disease is the presence of erythropoietin (Epo)-independent colony formation (endogenous erythroid colony [EEC]) and cytokine hypersensitivity. We have developed a simple liquid culture from CD34+ cells to study PV erythroid differentiation. PV erythroid differentiation was characterized in this culture system by two types of abnormalities: 1) an increased proliferation of progenitors in response to cytokines, associated with strict cytokine dependency for preventing apoptosis; and 2) Epo-independent terminal erythroid differentiation in the presence of stem cell factor and interleukin-3 as evidenced by the acquisition of glycophorin A. The level of Epo-independent terminal differentiation correlates in PV patients with the number of EEC. Epo-independent terminal differentiation as well as normal Epo-induced differentiation were repressed by inhibitors of JAK2 (AG490), PI3K (LY294002), and the Src family kinases (PP2). In contrast, an inhibitor of the ERK/MAP kinase pathway (PD98059) had no effect on Epo-independent terminal differentiation. These signaling abnormalities were not mediated by a decreased expression or activity of the membrane tyrosine phosphatase CD45, which dephosphorylates JAK2 and Src family kinases. This study demonstrates that early steps of PV erythroid differentiation are strictly cytokine dependent. In contrast, late erythroid differentiation is an Epo-independent phenomenon that is mediated by signaling pathways identical to those in Epo-induced differentiation.

BACKGROUNDWithin a period of three years, we identified 13 patients in whom pure red-cell aplasia developed during treatment with recombinant human erythropoietin (epoetin). We investigated whether there was an immunologic basis for the anemia in these patients.METHODSSerum samples from the 13 patients with pure red-cell aplasia were tested for neutralizing antibodies that could inhibit erythroid-colony formation by normal bone marrow cells in vitro. The presence of antierythropoietin antibodies was identified by means of binding assays with the use of radiolabeled intact, deglycosylated, or denatured epoetin.RESULTSSerum from all 13 patients blocked the formation of erythroid colonies by normal bone marrow cells. The inhibition was reversed by epoetin. Antibodies from 12 of the 13 patients bound only conformational epitopes in the protein moiety of epoetin; serum from the remaining patient bound to both conformational and linear epitopes in erythropoietin. In all the patients, the antibody titer slowly decreased after the discontinuation of treatment with epoetin.CONCLUSIONSNeutralizing antierythropoietin antibodies and pure red-cell aplasia can develop in patients with the anemia of chronic renal failure during treatment with epoetin.