[Diagnosis and therapy of polycythemia vera in the era of JAK2]

This review gives an overview on relevant topics of pathogenesis and diagnosis of polycythemia vera (PV). The presently available treatment options in PV are discussed and recommendations for the clinical management are given.The JAK2V617F mutation, a point mutation in the tyrosine kinase gene JAK2 (Janus Kinase 2), has emerged as a central feature in the pathogenesis of the myeloproliferative neoplasms (MPN). Subsequently, the identification of several other mutated genes in MPN has shown that the pathogenesis is complex and that the JAK2V617F mutation is a critical, but not the only step leading to the uncontrolled proliferation in MPN including PV.The diagnostic criteria of PV have been revised in 2008 and include the JAK2V617F mutation as one of the two major criteria of the disease. This molecular diagnostic marker proves the clonality and facilitates the diagnosis of early and uncertain cases which remained sometimes undiagnosed in the past.Main treatment aims are the reduction of thromboembolic events and the minimization of the risk of myelofibrosis and of acute leukemia. PV patients with low risk of vascular complications should be treated with phlebotomy and low dose acetylsalicylic acid. High risk patients should receive cytoreductive therapy with hydroxyurea or interferon alpha. Studies with JAK inhibitors are presently ongoing.

Peg-filgrastim (Peg-F) on day 4 of (R-)CHOP-14 chemotherapy compared to day 2 in elderly patients with diffuse large B-cell lymphoma (DLBCL): Results of a randomized trial of the German high-grade non-Hodgkin’s lymphoma study group (DSHNHL)

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Background: Application of peg-f is recommended on day 2 of chemotherapy, but later application has not been studied. Objective: To compare the effects of peg-f given on day 4 instead of day 2 on the endpoints feasibility, leukocyte counts, rate of infections and therapy-associated deaths after CHOP-14 with and without rituximab (R). Methods: Intention-to-treat-analysis of 109 elderly patients (median 69 years) with DLBCL receiving CHOP-14 or R-CHOP-14 randomized to peg-f on day 2 or day 4 (D4). Results: Of 103 evaluable pats., 51 received peg-f on day 2 (D2) and 52 on day 4 (D4). D2 and D4 populations were well balanced for known risk factors, and there was no difference between pats. receiving CHOP-14 and R-CHOP-14 with respect to the above mentioned endpoints. Both D2 and D4 allowed for an excellent adherence to (R)-CHOP-14 protocol, with a median relative dose of myelosuppressive drugs of 98% (D2) and 99% (D4), respectively. Leukocytopenia <2,000/mm3lasted for 3 (day 8 to 10) after D2 and 1 day (day 9) after D4. Grade 4 leukocytopenia (<1,000/mm3) occurred in 47% of all cycles after D2 and in 20.5% after D4 (p<0.001). Grade 3 and 4 infections occurred in 9.4% of D2 and 6.0% of D4 cycles (p=0.118). There were 4 therapy-associated deaths (all infection-associated) in the D2 and 1 (none infection-associated) in the D4 group (p=0.205 for all and p=0.057 for infection-associated deaths). Conclusions: Peg-f allows for excellent adherence of elderly patients to (R)-CHOP-14. Peg-f should be given on day 4 instead of day 2, because D4 results in less leukocytopenia, less infections and less therapy-associated deaths.

No significant financial relationships to disclose.

A unified definition of clinical resistance/intolerance to hydroxyurea in essential thrombocythemia: results of a consensus process by an international working group

A widely accepted definition of resistance or intolerance to hydroxyurea (HU) in patients with essential thrombocythemia (ET) is lacking. An international working group (WG) was convened to develop a consensus formulation of clinically significant criteria for defining resistance/intolerance to HU in ET. To this aim, an analytic hierarchy process (AHP), a multiple-attribute decision-making technique, was used. The steps consisted of selecting the candidate criteria for defining resistance/intolerance; identifying the motivations that could influence the preference of the WG for any individual criterion; comparing the candidate criteria in a pair-wise manner; and grading them according their ability to fulfill the motivations. Every step in the model was derived by questionnaires or group discussion. The WG proposed that the definition of resistance/intolerance should require the fulfillment of at least one of the following criteria: platelet count greater than 600,000/micro l after 3 months of at least 2 g/day of HU (2.5 g/day in patients with a body weight over 80 kg); platelet count greater than 400,000/micro l and WBC less than 2500/micro l or Hb less than 10 g/dl at any dose of HU; presence of leg ulcers or other unacceptable muco-cutaneous manifestations at any dose of HU; HU-related fever.

Bi-weekly dosing preserves the efficacy of rituximab in elderly patients with poor-prognosis DLBCL: Results from the RICOVER-60 trial of the German High-Grade Non-Hodgkin Lymphoma Study group (DSHNHL)

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Background: The addition of rituximab (R) to 3-weekly CHOP-21 improved overall results in elderly patients with DLBCL, but was more effective in good-prognosis (g-p: IPI = 1,2) than poor-prognosis (p-p: IPI = 3,4,5) patients (JCO 23:4117, 2005). Similarly, addition of R to bi-weekly CHOP-14 in the RICOVER-60 trial resulted in improved time to treatment failure (TTF) in 828 elderly (61–80 years) DLBCL patients (Blood 106:9a, 2005). To study the effects of R when combined with CHOP-14 in different subgroups of elderly DLBCL patients. Methods: Intention-to-treat-analysis of the primary endpoint time-to-treatment-failure (TTF) and the secondary endpoint overall survival (OS) in the subgroup of g-p and p-p patients treated within the RICOVER trial which compared 6 and 8 cycles of CHOP-14, both with and without R. Results: Of 828 evaluable patients (61–80 years, stage I-IV), 503 had g-p (CHOP-14 = 252; R-CHOP-14 = 251) and 325 p-p (CHOP-14 = 161; R-CHOP-14 = 163). After a median observation of 26 months, there was no difference between 6 and 8 cycles in either subgroup. In contrast, addition of R resulted in a similar improvement of TTF in both g-p (67% vs. 81%, p = 0.001) and p-p (36% vs. 52%, p = 0.004) patients. The improvement of survival is not yet different in either group: g-p: 82% (CHOP-14) vs. 88% (R-CHOP-14), p = 0.458; p-p: 58% (CHOP-14) vs. 64% (R-CHOP-14), p = 0.146. Pharmacokinetic studies show a pronounced nadir of R levels after the first R-CHOP-14, with R levels increasing after each subsequent cycle. The R nadir after the first R-CHOP is expected to be even more pronounced in a 3-weekly schedule and might explain the small improvement reproted for 3-weekly R in elderly patients with p-p DLBCL. Conclusions: Our subgroup and pharmacokinetic analysis indicate that not only dose-dense chemotherapy, but also dose-dense rituximab contribute to the excellent results of the RICOVER-60 trial. Supported by Deutsche Krebshilfe.

[Table: see text]

The Elbmarsch leukemia cluster: are there conceptual limitations in controlling immission from nuclear establishments in Germany?

The childhood leukemia cluster in the proximity of the German nuclear establishments of Geesthacht is unique in its spatial and temporal concentration. After a steep increase in cases in 1990, the cluster continues to show a significant increase up to the present. Early investigations of blood samples from a casual sample of local residents showed an increase in dicentric chromosomes in lymphocytes, indicating exposure exceeding dose limits. Analyses of the immission data revealed several unexpected deliveries of fission and activation products in the environment but provided no explanation of the source. Because of the observed overdispersion of dicentric chromosomes in cells, the idea of a contribution by densely ionizing emitters was compelling. The routine programs, however, do not include alpha emitters. These were measured in specific studies that proved contamination by transuranic nuclides. As shown in the present investigation, routine environmental surveillance programs support the occurrence of an accidental event near Geesthacht in September 1986. Until now, neither the cause nor the complete scenario of the activity release could be established. The ongoing discussion highlights limitations in the immission-control concept, which is predominantly based on gamma-radiation monitoring.

[Chronic myeloproliferative diseases. Diagnosis and therapy]

Chronic myeloproliferative disorders (CMPD) are neoplastic disorders of the hematopoietic stem cell. Four different entities are defined: chronic myeloid leukemia (CML), polycythemia vers, essential thrombocythaemia, and idiopathic myelofibrosis. In addition, overlapping entities within the CMPDs and between CMPDs and myelodysplastic syndrome have been described. Diagnostic measures are performed to classify the subtype exactly and to assess risk factors and prognosis. Cytogenetic and molecular analyses are mandatory for the characterization of the malignant clone. Hydroxyurea and interferon-alpha have proven effective in all CMPE. In CML, specific inhibition of the elevated ABL tyrosine kinase activity with imatinib is associated with high response rates. Allogeneic stem cell transplantation is the only curative treatment option for all entities. In CML, the decision-making analysis should be based on established scores. In BCR-ABL negative CMPDs an allogeneic stem cell transplantation should only be performed in patients with unfavorable prognosis.

Spontaneous remission in adult acute myeloid leukemia in association with systemic bacterial infection-case report and review of the literature

Spontaneous remission of acute myeloid leukemia in the adult is a rare event. We report on a 31-year-old male patient suffering from acute myeloid leukemia (AML) M5a according to the French-American-British (FAB) classification with biphenotypic features in flow cytometric examination and severe bacterial infection with group G streptococci at the time of diagnosis. Because of sepsis and stable clinical conditions, chemotherapy was delayed and antibiotics were administered intravenously. Within 6 weeks a spontaneous remission of AML occurred. Remission lasted for about 2 months. At the time of relapse, a change in phenotype of the leukemic blasts with a loss of B-lymphoid markers could be demonstrated by flow cytometry. The patient was treated with an induction therapy according to the multicentric German AMLCG 2000 schedule. To our knowledge, this is the first report of a spontaneous remission in an AML FAB M5a associated with coexpression of myeloid- and lymphoid-associated antigens on the leukemic blasts. Possible mechanisms of this phenomenon are discussed with a review of the literature.

Treatment of relapsed acute promyelocytic leukemia

By all-trans retinoic acid (ATRA) and chemotherapy over 70% of patients with newly diagnosed acute promyelocytic leukemia (APL) may be cured; 20-30% of patients still relapse and require salvage therapy. For relapsed or refractory APL, a standard treatment has not yet been defined. However, several effective drugs and approaches have been described. Treatment options for relapsed APL include chemotherapy regimens used in the treatment of relapsed acute myeloid leukemia usually combined with ATRA or of other differentiating agents such as liposomal ATRA or synthetic retinoids. Presently, allogeneic peripheral stem cell or bone marrow transplantation is the treatment of choice for younger patients who have a histocompatible donor, as it gives the chance of cure in second or further relapse. For patients without a donor or for those who are not suitable for allogeneic transplantation, autologous stem cell or bone marrow transplantation may offer at least the possibility of a prolongation of remission, if the harvested cells are negative in the RT-PCR of PML/RAR alpha. Arsenic compounds have a high antileukemic effectiveness on APL cells. Arsenic trioxide has recently been approved for relapsed or refractory APL. With this drug, complete hematologic remission rates of 80-92% and long-lasting molecular remissions were achieved in relapsed patients. For patients who do not qualify for these treatment options, monoclonal anti-CD33 antibodies may represent further treatment options.

A novel type of RET rearrangement (PTC8) in childhood papillary thyroid carcinomas and characterization of the involved gene (RFG8)

As part of ongoing studies on the RET rearrangement frequency in children with papillary thyroid carcinoma (PTC) after their exposure to radioactive iodine after the Chernobyl reactor accident, new methods for the detection of novel types of RET rearrangements are being developed. In this study, an improved reverse transcription-PCR strategy is used successfully to identify a new type of RET rearrangement. This rearrangement is designated PTC8 and the involved RET-fused gene (RFG) as RFG8. The identification of two reciprocal transcripts coding for the RFG8/RET and RET/RFG8 fusions suggests that the PTC8 rearrangement results from a balanced chromosomal translocation. With a view to clarify its role in tumor induction, we compared the fusion products with those of previously described RET rearrangements. We therefore sequenced and characterized the RFG8 cDNA, which showed no significant similarity to any functional protein described as yet. RFG8 is located on chromosome 18q21-22 and is expressed ubiquitously. Bioinformatic analysis predicts with a high probability that the corresponding rfg8 protein is located in the cytoplasm and is involved putatively in intracellular transport processes. Furthermore, we identified coiled-coil structures upstream of the breakpoint with one of the coiled-coils showing dimerization capability. Thus the rfg8/ret fusion protein exhibits structures for oncogenic activation that are similar to those observed in previously described RET fusions.

Double induction strategy including high dose cytarabine in combination with all-trans retinoic acid: effects in patients with newly diagnosed acute promyelocytic leukemia. German AML Cooperative Group

A prospective multicenter study was performed to investigate the clinical and molecular results of intensified double induction therapy including high-dose cytarabine (ara-C) in combination with ATRA in newly diagnosed acute promyelocytic leukemia (APL), followed by consolidation and 3 years maintenance therapy. Fifty-one patients, diagnosed and monitored from December 1994 to June 1999, were evaluated. The median age was 43 (16-60) years. The morphologic diagnosis was M3 in 40 (78%) and M3v in 11 (22%) patients. In 15 (30%) patients the initial white blood cell counts were > or =5 x 10(9)/l. The cytogenetic or molecular proof of the translocation t(15;17) was a mandatory prerequisite for eligibility. The diagnosis was confirmed by karyotyping in 46 and by RT-PCR of the PML/RARalpha transcript in 45 cases. The rate of complete hematological remission was 92% and the early death rate 8%. Monitoring of minimal residual disease by RT-PCR of PML/RARalpha (sensitivity 10(-4)) showed negativity in 29 of 32 (91%) evaluable cases after induction, in 23 of 25 (92%) after consolidation, and in 27 of 30 (90%) during maintenance, after a median time of 2, 4 and of 18 months after diagnosis, respectively. After a median follow-up of 27 months, the estimated actuarial 2 years overall and event-free survival were both 88% (79, 97), and the 2 years relapse-free survival 96% (90, 100). The high antileukemic efficacy of this treatment strategy is demonstrated by a rapid and extensive reduction of the malignant clone and by a low relapse rate. The results suggest that the intensity of the induction chemotherapy combined with ATRA is one of the factors which may have a critical influence on the outcome of APL. A randomized trial should assess the value of an induction therapy including ATRA and high-dose ara-C in comparison to standard-dose ara-C.

Translocation t(10;14)(q11.2:q22.1) fusing the kinetin to the RET gene creates a novel rearranged form (PTC8) of the RET proto-oncogene in radiation-induced childhood papillary thyroid carcinoma

Evaluation of 20 cases of radiation-induced childhood papillary thyroid carcinoma using fluorescence in situ hybridization demonstrated the presence of clonal translocations affecting the RET locus. Semiquantitative reverse transcription-PCR indicated overexpression of the RET tyrosine kinase (TK) domain in four cases. In two cases, the RET rearrangements PTC6 and PTC7 were identified and assigned to balanced translocations t(7;10)(q32;q11.2) and t(1;10)(p13;q11.2), respectively. In one case with a balanced translocation t(10;14)(q11.2;q22.1), 5' rapid amplification of cDNA ends revealed a novel type of RET oncogenic activation (PTC8), arising from a fusion of the 5' part of the kinectin (KTN1) gene to the TK domain of the RET gene. The presence of coiled-coil domains in the resulting ktn1/ret fusion protein suggests ligand-independent dimerization and thus constitutive activation of the ret TK domain.

Pattern of radiation-induced RET and NTRK1 rearrangements in 191 post-chernobyl papillary thyroid carcinomas: biological, phenotypic, and clinical implications

Molecular genetic aberrations and the related phenotypes were investigated in 191 papillary thyroid carcinomas (PTCs) from patients exposed at young age to radioiodine released from the Chernobyl reactor. A high prevalence of RET gene rearrangements (62.3%) with a significant predominance of ELE1/RET (PTC3) over H4/RET (PTC1) rearrangements was found in PTCs of the first post-Chernobyl decade. NTRK1 rearrangements were rare (3.3%). In 3.3%, we observed novel types of RET rearrangements: GOLGA5/ RET (PTC5), HTIF/RET (PTC6), RFG7/RET (PTC7), and an as yet undefined RFGX/RET.RET rearrangements, preferentially ELE1/RET, are related to rapid tumor development. At longer intervals after exposure to ionizing radiation, the prevalence of RET rearrangements declines with a shift from ELE1/RET to H4/RET, most significantly in female patients. The prevalence of specific types of rearrangements is independent of age at irradiation. A significantly higher prevalence of ELE1/RET was observed in the most heavily contaminated Oblasts, Gomel and Brest, suggesting a preferential formation of this type of rearrangement after high thyroid doses. RET rearrangement is related to aggressive growth: Rearrangement-positive PTCs were in a more advanced pT category and more frequently in the pN1 category at presentation than rearrangement-negative PTCs. ELE1/RET is related to the solid variant of PTC, H4/RET more frequently to typical papillary structures. The genotype/phenotype evaluation of post-Chernobyl PTCs reveals a characteristic spectrum of gene rearrangements that lead to typical phenotypes with important biological and clinical implications.

Interferon alpha in the treatment of polycythemia vera

Interferon alpha (IFN) inhibits the growth of the abnormal clone in patients with myeloproliferative disorders, leading to a reduction of the clinical and laboratory signs of the pathologic myeloproliferation. The therapeutic efficacy of IFN in polycythemia vera (PV) is demonstrated by the summarized treatment results of 279 patients participating in 16 prospective nonrandomized studies and in three case reports. The initial IFN dose ranged from 3 to 35 million IU/week. In 82% of the patients the frequency of phlebotomies was reduced. In 50% a complete remission was achieved, defined as a stable hematocrit of 45% without concomitant phlebotomies. Reduction of splenomegaly was seen in 77% and control of pruritus in 81% of the patients. The median observation time of the studies was 13 months (ranging from 3 to 84 months). Individual cases were followed for up to 126 months. In 21% of the patients IFN was terminated, owing mostly to side effects. The selective suppression of the malignant clone by IFN was demonstrated by the induction of cytogenetic remissions in sporadic cases with a chromosomal marker and by the observation of unmaintained remissions that lasted up to 4.8 years. IFN has no known mutagenic or teratogenic effects. The data presently available demonstrate that IFN is an effective alternative to the present forms of treatment in PV. Controlled prospective studies are essential to clarify whether the favorable biologic properties are also reflected by a benefit in clinical course and survival, and whether IFN may reduce the rates of acute leukemia and myelofibrosis. A randomized study that compares IFN and hydroxyurea in patients with PV has recently been initiated by the Suddeutsche Hamoblastosegruppe (SHG) in Germany.

Microsatellite instability and loss of heterozygosity in radiation-associated thyroid carcinomas of Belarussian children and adults

DNA from 129 paired thyroid tumorous and non-tumorous tissue samples of Belarussian children (102 patients; age at surgery </=18 years) and adults (27 patients; age at surgery 19-35 years), who had been exposed to radioactive fallout from the Chernobyl reactor accident in 1986, was examined for microsatellite instability (MSI) and loss of heterozygosity (LOH). Twenty-eight microsatellite markers were chosen because of their vicinity to DNA repair genes or genes involved in tumorigenesis as well as regions of chromosomal breakpoints in thyroid tumours. In 40 patients (31% of 129) we detected a total of 73 alterations, 80% of which were classified as LOH and only 20% as MSI. Amongst these 40 patients we identified a subgroup of 11, mainly young female patients (8.5% of 129), exhibiting alterations in at least two microsatellite markers. For comparison we examined samples from spontaneous thyroid carcinomas without radiation history from 20 adult patients from Munich (mean age at surgery 56 +/- 13 years). None of the tumour samples investigated showed evidence of alterations in the 28 microsatellite markers tested. Taken together our data indicate an increased instability of microsatellite markers in thyroid cancers from Belarussian patients. At present, it is uncertain whether the increased genome instability observed in Belarussian patients is the result of the exposure to radioactive iodine from the Chernobyl reactor accident or due to the young age of the patients.

Double induction strategy for acute myeloid leukemia: the effect of high-dose cytarabine with mitoxantrone instead of standard-dose cytarabine with daunorubicin and 6-thioguanine: a randomized trial by the German AML Cooperative Group

Early intensification of chemotherapy with high-dose cytarabine either in the postremission or remission induction phase has recently been shown to improve long-term relapse-free survival (RFS) in patients with acute myeloid leukemia (AML). Comparable results have been produced with the double induction strategy. The present trial evaluated the contribution of high-dose versus standard-dose cytarabine to this strategy. Between March 1985 and November 1992, 725 eligible patients 16 to 60 years of age with newly diagnosed primary AML entered the trial. Before treatment started, patients were randomized between two versions of double induction: 2 courses of standard-dose cytarabine (ara-C) with daunorubicin and 6-thioguanine (TAD) were compared with 1 course of TAD followed by high-dose cytarabine (3 g/m2 every 12 hours for 6 times) with mitoxantrone (HAM). Second courses started on day 21 before remission criteria were reached, regardless of the presence or absence of blast cells in the bone marrow. Patients in remission received consolidation by TAD and monthly maintenance with reduced TAD courses for 3 years. The complete remission (CR) rate in the TAD-TAD compared with the TAD-HAM arm was 65% versus 71% (not significant [NS]), and the early and hypoplastic death rate was 18% versus 14% (NS). The corresponding RFS after 5 years was 29% versus 35% (NS). An explorative analysis identified a subgroup of 286 patients with a poor prognosis representing 39% of the entire population; they included patients with more than 40% residual blasts in the day-16 bone marrow, patients with unfavorable karyotype, and those with high levels of serum lactate dehydrogenase. Their CR rate was 65% versus 49% (p =.004) in favor of TAD-HAM and was associated with a superior event-free survival (median, 7 v 3 months; 5 years, 17% v 12%; P =.012) and overall survival (median, 13 v 8 months; 5 years, 24% v 18%; P =.009). This suggests that the incorporation of high-dose cytarabine with mitoxantrone may contribute a specific benefit to poor-risk patients that, however, requires further substantiation. Double induction, followed by consolidation and maintenance, proved a safe and effective strategy and a new way of delivering early intensification treatment for AML.

Diagnosis, pathogenesis and treatment of the myeloproliferative disorders essential thrombocythemia, polycythemia vera and essential megakaryocytic granulocytic metaplasia and myelofibrosis

According to strict clinical, hematological and morphological criteria, the Philadelphia (Ph) chromosome negative chronic myeloproliferative disorders essential thrombocythemia (ET), polycythemia vera (PV), and agnogenic myeloid (megakaryocytic/granulocytic) metaplasia (AMM) or idiopathic myelofibrosis (IMF) are three distinct disease entities with regard to clinical manifestations, natural history and outcome in terms of life expectancy. As clonality studies have clearly demonstrated that fibroblast proliferation in AMM, as well as in many other conditions such as advanced stages of Ph(+)-essential thrombocythemia, Ph(+)-granulocytic leukemia, and Ph(-)-polycythemia vera, is polyclonal indicating that myelofibrosis is secondary to the megakaryocytic granulocytic metaplasia in these various conditions, AMM is illogically labeled as IMF. As abnormal megakaryocytic granulocytic metaplasia is the essential feature preceding the early prefibrotic stage of AMM, the term essential megakaryocytic granulocytic metaplasia (EMGM) can readily be used to characterize this condition more appropriately at the biological level. Clinical, hematological and morphological characteristics, in particular megakaryocytopoiesis and bone marrow cellularity, reveal diagnostic features, which enable a clear-cut distinction between ET, PV and EMGM or classical IMF. The characteristic increase and clustering of enlarged megakaryocytes with mature cytoplasm and multilobulated nuclei and their tendency to cluster in a normal or only slightly increased cellular bone marrow represent the hallmark of ET. The characteristic increase and clustering of enlarged mature and pleiomorphic megakaryocytes with multilobulated nuclei and proliferation of erythropoiesis in a moderate to marked hypercellular bone marrow with hyperplasia of dilated sinuses are the specific diagnostic features of untreated PV. EMGM, including the early prefibrotic stages as well as the various myelofibrotic stages of classical IMF appear to be a distinct neoplastic dual proliferation of abnormal megakaryopoiesis and granulopoiesis. The histopathology of the bone marrow in prefibrotic EMGM and in classical IMF is dominated by atypical, enlarged and immature megakaryocytes with cloud-like immature nuclei, which are not seen in ET and PV at diagnosis and during follow-up. Myelofibrosis in ET, PV and EMGM is graded into: no reticulin fibrosis (MF0), early reticulin fibrosis (MF1), advanced reticulin sclerosis with minor or moderate collagen fibrosis (MF2) and advanced collagen fibrosis with osteosclerosis (MF3). Myelofibrosis is not a feature of ET at diagnosis and during long-term follow-up. Myelofibrosis may be present in a minority of PV-patients at diagnosis and usually becomes apparent during long-term follow-up in the majority of PV-patients. Myelofibrosis secondary to the abnormal megakaryocytic and granulocytic myeloproliferation constitutes a prominent feature in the majority of EMGM/IMF at time of diagnosis and usually progresses more or less rapidly during the natural history of the disease. Life expectancy is normal in ET, normal during the 1st ten years and compromised during the 2nd ten years follow-up in PV, but significantly shortened in the prefibrotic stage of EMGM as well as in the various myelosclerotic stages of classical IMF. First line treatment options in prospective randomized clinical trials of newly diagnosed MPD-patients are control of platelet function with low-dose aspirin versus reduction of platelet count with anagrelide, interferon or hydroxyurea in ET; control of platelet and erythrocyte counts by interferon alone versus bloodletting plus hydroxyurea on indication in PV; interferon versus no treatment in the early stages of EMGM; a wait and see strategy in the fibrotic stages of EMGM or classical IMF with favorable prognostic factors, and bone marrow transplantation in classical IMF with poor prognostic factors at presentation or during short-term follow-up.

NTRK1 re-arrangement in papillary thyroid carcinomas of children after the Chernobyl reactor accident

The prevalence of NTRK1 re-arrangement was determined in papillary thyroid carcinomas (PTCs) of children from Belarus who had been exposed to radioactive iodine after the Chernobyl reactor accident; 81 tumors were included, all of which were devoid of RET re-arrangement as analyzed in a current study on genomic alterations in PTC. Oncogenic fusion of the NTRK1 tyrosine kinase domain with the amino-terminal part of the tropomyosin gene (TPM3/NTRK1, trk) was observed in 5 tumors. A single tumor exhibited a TPR/NTRK1 fusion (TRK-T2). Reciprocal NTRK1/TPM3 transcripts were found in 4 of 5 tumors with TPM3/NTRK1 re-arrangement, indicating an intra-chromosomal balanced reciprocal inversion. No phenotypic differences from other post-Chernobyl childhood PTCs were detected. As compared with the high prevalence of RET re-arrangements reported for thyroid carcinomas of children after the Chernobyl reactor accident, NTRK1 re-arrangements appear rare. Our results confirm that activation of receptor tyrosine kinase genes plays the predominant role in post-Chernobyl childhood thyroid carcinogenesis.

Diagnosis, pathogenesis and treatment of the myeloproliferative disorders essential thrombocythemia, polycythemia vera and essential megakaryocytic granulocytic metaplasia and myelofibrosis

According to strict clinical, hematological and morphological criteria, the Philadelphia (Ph) chromosome negative chronic myeloproliferative disorders essential thrombocythemia (ET), polycythemia vera (PV), and agnogenic myeloid (megakaryocytic/granulocytic) metaplasia (AMM) or idiopathic myelofibrosis (IMF) are three distinct disease entities with regard to clinical manifestations, natural history and outcome in terms of life expectancy. As clonality studies have clearly demonstrated that fibroblast proliferation in AMM, as well as in many other conditions such as advanced stages of Ph(+)-essential thrombocythemia, Ph(+)-granulocytic leukemia, and Ph(-)-polycythemia vera, is polyclonal indicating that myelofibrosis is secondary to the megakaryocytic granulocytic metaplasia in these various conditions, AMM is illogically labeled as IMF. As abnormal megakaryocytic granulocytic metaplasia is the essential feature preceding the early prefibrotic stage of AMM, the term essential megakaryocytic granulocytic metaplasia (EMGM) can readily be used to characterize this condition more appropriately at the biological level. Clinical, hematological and morphological characteristics, in particular megakaryocytopoiesis and bone marrow cellularity, reveal diagnostic features, which enable a clear-cut distinction between ET, PV and EMGM or classical IMF. The characteristic increase and clustering of enlarged megakaryocytes with mature cytoplasm and multilobulated nuclei and their tendency to cluster in a normal or only slightly increased cellular bone marrow represent the hallmark of ET. The characteristic increase and clustering of enlarged mature and pleiomorphic megakaryocytes with multilobulated nuclei and proliferation of erythropoiesis in a moderate to marked hypercellular bone marrow with hyperplasia of dilated sinuses are the specific diagnostic features of untreated PV. EMGM, including the early prefibrotic stages as well as the various myelofibrotic stages of classical IMF appear to be a distinct neoplastic dual proliferation of abnormal megakaryopoiesis and granulopoiesis. The histopathology of the bone marrow in prefibrotic EMGM and in classical IMF is dominated by atypical, enlarged and immature megakaryocytes with cloud-like immature nuclei, which are not seen in ET and PV at diagnosis and during follow-up. Myelofibrosis in ET, PV and EMGM is graded into: no reticulin fibrosis (MF0), early reticulin fibrosis (MF1), advanced reticulin sclerosis with minor or moderate collagen fibrosis (MF2) and advanced collagen fibrosis with osteosclerosis (MF3). Myelofibrosis is not a feature of ET at diagnosis and during long-term follow-up. Myelofibrosis may be present in a minority of PV-patients at diagnosis and usually becomes apparent during long-term follow-up in the majority of PV-patients. Myelofibrosis secondary to the abnormal megakaryocytic and granulocytic myeloproliferation constitutes a prominent feature in the majority of EMGM/IMF at time of diagnosis and usually progresses more or less rapidly during the natural history of the disease. Life expectancy is normal in ET, normal during the 1st ten years and compromised during the 2nd ten years follow-up in PV, but significantly shortened in the prefibrotic stage of EMGM as well as in the various myelosclerotic stages of classical IMF. First line treatment options in prospective randomized clinical trials of newly diagnosed MPD-patients are control of platelet function with low-dose aspirin versus reduction of platelet count with anagrelide, interferon or hydroxyurea in ET; control of platelet and erythrocyte counts by interferon alone versus bloodletting plus hydroxyurea on indication in PV; interferon versus no treatment in the early stages of EMGM; a wait and see strategy in the fibrotic stages of EMGM or classical IMF with favorable prognostic factors, and bone marrow transplantation in classical IMF with poor prognostic factors at presentation or during short-term follow-up.

Distinct frequency of ret rearrangements in papillary thyroid carcinomas of children and adults from Belarus

Rearrangements of the ret oncogene were investigated in papillary thyroid carcinomas (PTC) from 51 Belarussian children with a mean age of 3 years at the time of the Chernobyl radiation accident. For comparison, 16 PTC from exposed Belarussian adults and 16 PTC from German patients without radiation history were included in the study. ret rearrangements were detected and specified by RT-PCR and direct sequencing using specific primers for ret/PTC1, 2 and 3. Only ret/PTC1, and no ret/PTC3, was found in the adult patients, with a frequency of 69% for the Belarussian cases, but of only 19% in the German patients. In contrast, 13 ret/PTC3 (25.5%) and 12 ret/PTC1 (23.5%) rearrangements were present in PTC from Belarussian children. Thus, our study reveals about a 1:1 ratio of ret/PTC3 and ret/PTC1, in contrast to earlier studies with lower numbers of cases and exhibiting a high predominance of ret/PTC3 (ratio about 3:1). A ratio (2.5:1) similar to that in earlier investigations (diagnosed 1991-94) was obtained for cases included in our study that were diagnosed in 1993/94. The present data suggest that ret/PTC3 may be typical for radiation-associated childhood PTC with a short latency period, whereas ret/PTC1 may be a marker for later-occurring PTC of radiation-exposed adults and children.

Cytogenetic changes in radiation-induced tumors of the thyroid

Thyroid carcinoma incidence is increased significantly after ionizing irradiation; however, the possible mechanisms have not yet been identified. To provide clues for an understanding of the radiation-induced transformation of thyroid epithelium, we analyzed the karyotypes of 56 childhood thyroid tumors that appeared in Belarus after the Chernobyl nuclear accident in 1986. We also studied eight secondary thyroid tumors that developed after radiotherapy. Metaphase preparations obtained from primary cultures were analyzed by G-banding. Clonal structural aberrations were found in 13 of 56 Belarussian cases and in 6 of 8 secondary tumors that developed after radiotherapy. Furthermore, we detected multiple chromosomal aberrations as well as complex rearrangements in some of these tumors and performed a detailed analysis of marker chromosomes from a single case using spectral karyotyping and comparative genomic hybridization in a childhood tumor from Belarus with a near-triploid karyotype. Both comparative genomic hybridization and spectral karyotyping analysis revealed structural alterations affecting identical chromosomes 1, 2, 9, and 13, among others. In addition to the known hot spots of alterations in papillary thyroid carcinomas on chromosomes 1q and 10q, a comprehensive breakpoint analysis in the pooled data set revealed novel breakpoints on chromosomes 4q, 5q, 6p, 12q, 13q, and 14q. The chromosomal aberrations in these tumors may provide suitable starting points for the positional cloning of genes involved in radiation-induced tumorigenesis.

Correlation of cytogenetic, molecular cytogenetic, and clinical findings in 59 patients with ANLL or MDS and abnormalities of the short arm of chromosome 12

Abnormalities of the short arm of chromosome 12 (12p) are found in about 5% of acute nonlymphocytic leukaemias (ANLL) and myelodysplastic syndromes (MDS). They are described to be characteristic of secondary leukaemias, especially after prior mutagenic exposure, and to be associated with a poor prognosis. In our series of 59 patients with 12p abnormalities and ANLL or MDS, exposure to genotoxic agents was proven only in five patients, but in 13/44 patients ANLL evolved from an MDS. Patients with a small deletion del(12)(p11.2p13) having a mild clinical course were distinguished from those with a large del(12)(p11.2), additional chromosomal anomalies, and a poor clinical course. Among the 31 patients with translocations or dicentric chromosomes involving 12p, a group of eight with t/dic(12;13) was the most frequent and was associated with a poor prognosis. The clinical outcome was adverse in the majority of patients with complex karyotype abnormalities, but in some patients a milder clinical course seems likely. A new, hitherto undescribed, abnormality in an MDS case with a duplication dup(12)(p11.2p13) was the amplification of the signal of the yeast artificial chromosome (YAC) clone 964c10 (D12S736). In 38 cases with deletions or unbalanced translocations/dicentrics one YAC signal was lost. Five patients with balanced translocations demonstrated breakpoints within the YAC, containing the ETV6 (TEL) gene. The breakpoints were telomeric to the YAC 964c10 in seven cases and centromeric in one patient.

Molecular analysis of new subtypes of ELE/RET rearrangements, their reciprocal transcripts and breakpoints in papillary thyroid carcinomas of children after Chernobyl

A high prevalence of RET rearrangements is found in papillary thyroid carcinomas (PTC) of children from Belarus after the Chernobyl reactor accident. The ELE/RET rearrangement (PTC3) is prevailing. Aberrant types of ELE/RET rearrangement have been found with a truncated ELE1 gene: As compared with the common form (PTC3r1) one aberrant type is shorter by one 144 bp exon (PTC3r2) (three cases); in the second atypic form (PTC3r3) the ELE1 part is 18 bp shorter than in PTC3r1. In agreement with the observation that the oncogenic RET is generated by a paracentric inversion at chromosome 10, we found not only ELE/RET, but also RET/ELE transcripts in these tumors. Sequencing of the breakpoint regions at the genomic DNA level revealed DNA modifications that might be relevant for illegitimate recombination after DNA doublestrand breaks. The high prevalence of ELE/RET rearrangements and various subtypes appears to be typical for radiation-induced thyroid carcinomas of children after the Chernobyl reactor accident.

Detection of a novel type of RET rearrangement (PTC5) in thyroid carcinomas after Chernobyl and analysis of the involved RET-fused gene RFG5

A novel type of RET rearrangement, PTC5, was detected in papillary thyroid carcinomas of two patients exposed to radioactive fallout after Chernobyl. Reverse transcription-PCR and rapid amplification of 5'-cDNA ends revealed a fusion of the ret tyrosine kinase (TK) domain with a sequence identical to that described previously as ret-II. Ret-II is a transfection artifact in NIH3T3 cells and has not yet been detected in any human tumor. Overlapping sequences found in the expressed sequence tag databases enabled us to sequence the COOH terminus of the ret-fused gene 5 (RFG5). The combined data made it possible to assemble a full-length rfg5 protein sequence. Computer-assisted analysis of this sequence reveals four putative coiled-coil structures, possibly involved in dimerization, but no membrane-binding sequences. Northern blots show a ubiquitous RFG5 expression in various normal tissues, including the thyroid gland. In addition to the RFG5/RET, we also detected the reciprocal RET/RFG5 transcript in both tumor samples, suggesting that the rearrangement is based on a balanced reciprocal translocation. In agreement with other rearranged TKs, it is concluded that the transforming action of the new fusion protein rfg5/ret in thyroid tumors may be due to an activation of the ret TK by constitutive expression and dimerization potential of the 5'-fused rfg5 protein. Ret immunohistochemistry indicates that the fusion protein is expressed in all cells of PTC5 tumors, suggesting that RFG5/RET rearrangement is an early event in thyroid carcinogenesis.

Should a platelet limit of 600 x 10(9)/l be used as a diagnostic criterion in essential thrombocythaemia? An analysis of the natural course including early stages

In order to evaluate the natural history of essential thrombocythaemia (ET), clinical data and prognostic factors of 143 patients with ET were retrospectively analysed (mean observation time 6.1 +/- 4.6 years). In 42 patients the early phase of the disease with initial platelet counts between 250 and 600 x 10(9)/l was assessed. In most early cases, ET was suggested by clinical symptoms (79%) and increased megakaryopoiesis (95%) with abnormal megakaryocytes in bone marrow histology (n = 34) and cytology (n = 5). Other myeloproliferative disorders and reactive thrombocytosis were excluded according to the diagnostic criteria of the Polycythemia Vera Study Group. During follow-up of the 38 early cases not treated cytoreductively at diagnosis, the platelet counts increased to >600 x 10(9)/l in 28 patients (74%) and remained between 450 and 600 x 10(9)/l in 10 patients (26%). In primarily asymptomatic patients (n = 46) with initial platelet counts above (n = 37) and below 600 x 10(9)/l (n = 9) the rates of increase of symptomatic patients were similar at about 7% per year. No influence of the initial platelet count on survival was seen in multivariate analysis of prognostic factors which included all 143 cases. Survival was mainly influenced by the rate of ET-related complications during follow-up (P = 0.002). Analysing the influence of cytoreductive therapy on symptom-free survival, platelet reduction benefited patients under 60 years (19 cytoreductively treated v 65 untreated patients, P = 0.075). The results demonstrate the possible clinical relevance of the early stages of ET and suggest that the features of pathologic megakaryopoiesis in the bone marrow are a more reliable diagnostic criterion than a definite platelet limit. Therefore, further therapeutic studies should include all stages of the disease and all age groups.

p53 mutations in childhood thyroid tumours from Belarus and in thyroid tumours without radiation history

Mutations in the p53 tumour-suppressor gene (exons 5-8) were investigated in 31 Belarussian childhood thyroid tumours (24 cases of papillary thyroid carcinoma, 3 benign tumours and 2 cases each of thyroiditis and goiter); 33 thyroid tumours from juveniles and adults without radiation exposures (25 carcinomas of various histological types, including 11 papillary carcinomas and 8 adenomas) and 6 tumours from adults (4 papillary carcinomas, 1 adenoma, 1 goiter) served as controls. The mutational spectrum of p53 differed greatly between the childhood thyroid carcinomas from Belarus and the control groups. In the control groups of 29 malignant thyroid tumours, 7 different mutations were detected on exons 5-8, none of which occurred among the 15 papillary carcinomas in this group. Five mutations were found in tissue samples of the 24 childhood papillary carcinomas, and they were all the same p53 point mutation (CGA --> CGG) on codon 213 of exon 6. To determine whether this mutation is simply a polymorphism or whether it is specific to the tumour cells, laser-assisted microdissection was applied to collect various areas of tumorous and non-tumorous cells (10-20 cells per sample) from each paraffin-embedded tissue section of 8 of the papillary thyroid carcinomas. Using PCR-SSCP and sequence analysis on these cells, the very same p53 mutation on codon 213 was detected in various microdissected tumour samples of 2 cases, but it was not found in any microdissected non-tumorous sample. The exclusive occurrence of this p53 mutation in selective microdissected samples of tumour cells, even as homozygous mutation in 1 case, reflects a distinct tumour heterogeneity within papillary childhood thyroid carcinomas.

Randomized studies with interferon in chronic myelogenous leukemia (CML) and comparative molecular aspects. German CML Study Group

Four randomized prospective studies on interferon alpha (IFN) in CML report varying degrees of prolongation of the chronic phase of CML and of survival as compared to conventional therapies. There is agreement that IFN prolongs survival as compared to standard busulfan. There is disagreement, however, as to which degree IFN is superior to hydroxyurea. Whereas the randomized studies of the Italian cooperative group and of the British MRC find a statistically significant survival advantage of IFN over hydroxyurea of about 20 months, this difference is only 10 months in the German randomized study and not significant. One reason for this difference might be the more intensive treatment schedule for the hydroxyurea control group in the German study. Other reasons might be differences in risk profiles between the patient groups studied and in strategies of IFN therapy. About 1% of the human genome consists of retroviral or retroviral-like sequences. By analogy to animal models, endogenous retroviruses might also have pathogenic potential in human disease. The transposon-like structure of retroviruses that enables them to integrate at almost any position in the host genome and the capability of retroviruses to serve as efficient vehicles of cellular genes are in support of a pathogenic potential. Furthermore, particles resembling retroviruses have been observed long ago in human embryonic and malignant tissues and cell lines. Sequence information and the transcriptional activity of the endogenous sequences argue against the possibility that these sequences are only fossil relics of early evolutionary periods. Most of the sequences appear to be inactivated by stop codons or frameshifts, making the genomic localization of open reading frames with biological activity difficult. Up to now, mutagenesis by insertion of retroviral-like sequences in sporadic cases of human disease appears to be the only example of pathogenic relevance of retroviruses in man.

Chromosome translocations in thyroid tissues from Belarussian children exposed to radioiodine from the Chernobyl accident, measured by FISH-painting

Chromosome painting of chromosomes 1, 4 and 12 was performed on metaphase preparations of cultured thyroid cells to analyse the frequency of radiation-induced stable chromosome translocations in papillary thyroid carcinomas from 40 Belarussian children exposed to radioiodine from the Chernobyl accident, and from 31 reference case. As expected, we found the highest translocation frequencies in secondary thyroid tumours after radiotherapy, but there were also high frequencies in tumour tissues as well as in non-tumourous tissues from childhood papillary carcinoma samples from Belarus. Among the Belarussian tumours the cases from the Gomel region exhibited the highest frequency of translocations and five cases lie within the range of frequencies observed in secondary thyroid tumours after radiotherapy. The findings support the assumption that radiation was the principal cause of the tumours in Belarus, but they indicate also that only a minority of the Belarus cases, which have developed papillary carcinomas, were exposed to very high doses of radioiodine.

A new form of RET rearrangement in thyroid carcinomas of children after the Chernobyl reactor accident

Intrachromosomal rearrangements involving the RET and the adjacent H4 or ELE1 gene are very frequent events in thyroid cancer of children from Belarus after the Chernobyl reactor accident (Klugbauer et al., 1995). The fusion product between ELE1 and RET (RET/ PTC3) seems to be the prevailing type of rearrangement as shown in a recently published study using a novel RT multiplex PCR approach in combination with the identification of the rearrangement type by RT-PCR and direct sequencing. Now we found a new type of RET rearrangement: By the 5'RACE method we demonstrated in cDNA the fusion of the tyrosine kinase domain of RET with a truncated ELE1 gene shorter than the ELE1 in RET/PTC3. Sequencing of genomic DNA revealed a rearrangement breakpoint at position 41 of a new ELE1 intron (522 bp in length). The new oncogene RET/ delta PTC3 is shortened by one ELE1 exon of 144 bp in length. Structural considerations of the ele1 amino terminal of RET/ delta PTC3 suggest that the transforming activity of the fusion protein is apparently not affected by this truncation. The exon lacking in RET/ delta PTC3 was found to code in the reciprocal transcript RET/ delta ELE1 and increased its size by 144 bp. Obviously the new and possibly additional ELE/RET fusion molecules might even increase the high prevalence of ELE1/RET rearrangements in thyroid carcinomas of children after the Chernobyl reactor accident.

Incidence and implication of additional chromosome aberrations in acute promyelocytic leukaemia with translocation t(15;17)(q22;q21): a report on 50 patients

Acute promyelocytic leukaemia (APL) is characterized by the translocation t(15;17)(q22;q21). Usually t(15;17) is the sole cytogenetic abnormality, but some patients show other chromosome aberrations in addition to t(15;17). The influence of additional chromosome aberrations on the clinical outcome of patients with t(15;17) is unclear. We have analysed 50 cases of APL carrying the translocation t(15;17). Additional chromosome aberrations were observed in 17/47 patients (36%) studied at initial diagnosis and in all three patients studied at relapse. In nine cases (18%) an additional chromosome 8 and in six cases (12%) an isochromosome of the long arm of the derivative chromosome 17 was observed. Various structural rearrangements in addition to t(15;17) were detected in nine patients (18%). Clinical follow-up data were available for 44 patients studied at diagnosis. A complete remission (CR) was achieved in 34 patients (77%). 10 patients (23%) died within 1 month after diagnosis due to infection or bleeding, eight (24%) relapsed within 10-18 months after initial diagnosis. 28 patients are alive 2-93 months after diagnosis (25 in first CR, two in second and one in third CR) (median follow-up 18.5 months). Bone marrow transplantation was performed in six patients (three in first CR, two in second CR, one in third CR), all are alive and in CR. An influence of secondary chromosome anomalies on prognosis was not observed. However, if a higher rate of long-term remission can be reached, specific secondary chromosome aberrations might turn out to be of prognostic value.

Interferon-alpha in the treatment of essential thrombocythemia

Interferon alpha (IFN) inhibits the growth of megakaryocytic progenitors in normal hematopoiesis and in patients with essential thrombocythemia (ET) leading to a reduction of peripheral platelet counts. The effectiveness in the induction therapy of patients with ET is demonstrated in 11 international studies including 212 patients. With an average dose of about 3 mill IU IFN daily, the response rate was about 90%. Further studies investigated the practicability and the success of IFN maintenance therapy. The results show that IFN can effectively control platelet counts over a period of several years. During maintenance the IFN dose could be reduced in the majority of patients. However, sustained unmaintained complete remissions were obtained in only 12% of the patients. Side effects were frequently the limiting factors in treatment with IFN especially in older patients. Analyzing a total of 273 patients, IFN therapy was terminated in 25% against the primary treatment plan. Of the currently effective drugs in controlling the platelet counts in ET, IFN is the only antiproliferative agent with immuno-modulating properties. Thus far, no leukemogenic or significant gonadotoxic effects have been observed. In a subset of the patients off all therapy, the sustained remissions support a long-term tumor load reduction effect by IFN. Thus, IFN is a promising agent in cytoreductive treatment of ET especially in younger patients.

Fifty-one patients with acute myeloid leukemia and translocation t(8;21)(q22;q22): an additional deletion in 9q is an adverse prognostic factor

The translocation t(8;21)(q22;q22) occurs in 6 to 12 percent of patients with AML, and usually predicts a good response to chemotherapy with a high remission rate and a relatively long median survival. The influence of additional chromosome aberrations on the clinical outcome of patients with t(8;21) is unclear. We analyzed 51 cases of acute myeloid leukemia carrying a translocation t(8;21)(q22;q22); 23 female and 28 male patients. The complete remission rate was 92 percent and median overall survival was 52.4 months. The median overall survival of female patients was significantly worse than of male patients (37.2 months vs not reached, P = 0.025). Additional chromosome aberrations were detected in 41 patients at diagnosis (80 percent), 31 (61 percent) had lost a sex chromosome, seven (14 percent) showed a partial deletion of the long arm of chromosome 9 and in three patients (6 percent) a gain of chromosome 8 was observed. Whereas the loss of a sex chromosome had no influence on prognosis, a partial deletion of the long arm of chromosome 9 was an unfavorable prognostic factor. The median overall survival of the seven patients with del(9q) was only 12.5 months and thus significantly shorter than in patients with only t(8;21) or with t(8;21) and additional sex chromosome loss (median survival not reached: P = 0.0010).

The superoxide dismutase-mimic copper-putrescine-pyridine suppresses lipid peroxidation in CHO cells. Implications for its prooxidative and antioxidative mechanisms of action

Copper-Putrescine-Pyridine (Cu-PuPy) is a membrane-permeable complex which efficiently dismutates superoxide. In excess of 0.1 mM it is highly cytotoxic and oxidizes cellular GSH with concomitant production of H2O2. Here we show that treatment of CHO cells with 0.2 mM Cu-PuPy (0-200 min) leads to an accumulation of H2O2. Organic hydroperoxides which are also formed at low levels in the present of Cu-PuPy, increase significantly after removal of the copper complex. We conclude that Cu-PuPy acts as an oxidant until cellular GSH is depleted. However, by interfering with radical chain propagation reactions, it suppresses lipid peroxidation and thus substitutes for consumed physiological antioxidants in a later stage of treatment. This consistently explains our previous, seemingly paradox, finding that longer Cu-PuPy treatments may be significantly les toxic than shorter ones.