Identification and surveillance of rare relapse-initiating stem cells during complete remission after transplantation

ABSTRACT

Relapse after complete remission (CR) remains the main cause of mortality after allogeneic stem cell transplantation for hematological malignancies and, therefore, improved biomarkers for early prediction of relapse remains a critical goal toward development and assessment of preemptive relapse treatment. Because the significance of cancer stem cells as a source of relapses remains unclear, we investigated whether mutational screening for persistence of rare cancer stem cells would enhance measurable residual disease (MRD) and early relapse prediction after transplantation. In a retrospective study of patients who relapsed and patients who achieved continuous-CR with myelodysplastic syndromes and related myeloid malignancies, combined flow cytometric cell sorting and mutational screening for persistence of rare relapse-initiating stem cells was performed in the bone marrow at multiple CR time points after transplantation. In 25 CR samples from 15 patients that later relapsed, only 9 samples were MRD-positive in mononuclear cells (MNCs) whereas flowcytometric-sorted hematopoietic stem and progenitor cells (HSPCs) were MRD-positive in all samples, and always with a higher variant allele frequency than in MNCs (mean, 97-fold). MRD-positivity in HSPCs preceded MNCs in multiple sequential samples, in some cases preceding relapse by >2 years. In contrast, in 13 patients in long-term continuous-CR, HSPCs remained MRD-negative. Enhanced MRD sensitivity was also observed in total CD34+ cells, but HSPCs were always more clonally involved (mean, 8-fold). In conclusion, identification of relapse-initiating cancer stem cells and mutational MRD screening for their persistence consistently enhances MRD sensitivity and earlier prediction of relapse after allogeneic stem cell transplantation.

A T cell receptor targeting a recurrent driver mutation in FLT3 mediates elimination of primary human acute myeloid leukemia in vivo

Acute myeloid leukemia (AML), the most frequent leukemia in adults, is driven by recurrent somatically acquired genetic lesions in a restricted number of genes. Treatment with tyrosine kinase inhibitors has demonstrated that targeting of prevalent FMS-related receptor tyrosine kinase 3 (FLT3) gain-of-function mutations can provide significant survival benefits for patients, although the efficacy of FLT3 inhibitors in eliminating FLT3-mutated clones is variable. We identified a T cell receptor (TCR) reactive to the recurrent D835Y driver mutation in the FLT3 tyrosine kinase domain (TCRFLT3D/Y). TCRFLT3D/Y-redirected T cells selectively eliminated primary human AML cells harboring the FLT3D835Y mutation in vitro and in vivo. TCRFLT3D/Y cells rejected both CD34+ and CD34- AML in mice engrafted with primary leukemia from patients, reaching minimal residual disease-negative levels, and eliminated primary CD34+ AML leukemia-propagating cells in vivo. Thus, T cells targeting a single shared mutation can provide efficient immunotherapy toward selective elimination of clonally involved primary AML cells in vivo.

Perivascular niche cells sense thrombocytopenia and activate hematopoietic stem cells in an IL-1 dependent manner

Hematopoietic stem cells (HSCs) residing in specialized niches in the bone marrow are responsible for the balanced output of multiple short-lived blood cell lineages in steady-state and in response to different challenges. However, feedback mechanisms by which HSCs, through their niches, sense acute losses of specific blood cell lineages remain to be established. While all HSCs replenish platelets, previous studies have shown that a large fraction of HSCs are molecularly primed for the megakaryocyte-platelet lineage and are rapidly recruited into proliferation upon platelet depletion. Platelets normally turnover in an activation-dependent manner, herein mimicked by antibodies inducing platelet activation and depletion. Antibody-mediated platelet activation upregulates expression of Interleukin-1 (IL-1) in platelets, and in bone marrow extracellular fluid in vivo. Genetic experiments demonstrate that rather than IL-1 directly activating HSCs, activation of bone marrow Lepr+ perivascular niche cells expressing IL-1 receptor is critical for the optimal activation of quiescent HSCs upon platelet activation and depletion. These findings identify a feedback mechanism by which activation-induced depletion of a mature blood cell lineage leads to a niche-dependent activation of HSCs to reinstate its homeostasis.

A model of non-Maxwellian electron distribution function for the analysis of ECE data in JET discharges

Recent experiments performed in JET at high level of plasma heating, in preparation of, and during the DT campaign have shown significant discrepancies between electron temperature measurements by Thomson Scattering (TS) and Electron Cyclotron Emission (ECE). In order to perform a systematic analysis of this phenomenon, a simple model of bipolar distortion of the electron distribution function has been developed, allowing analytic calculation of the EC emission and absorption coefficients. Extensive comparisons of the modelled ECE spectra (at both the 2nd and the 3rd harmonic extraordinary mode) with experimental measurements display good agreement when bulk electron distribution distortions around 1-2 times the electron thermal velocity are used and prove useful for a first level of analysis of this effect.

Stepwise GATA1 and SMC3 mutations alter megakaryocyte differentiation in a Down syndrome leukemia model

Acute megakaryoblastic leukemia of Down syndrome (DS-AMKL) is a model of clonal evolution from a preleukemic transient myeloproliferative disorder requiring both a trisomy 21 (T21) and a GATA1s mutation to a leukemia driven by additional driver mutations. We modeled the megakaryocyte differentiation defect through stepwise gene editing of GATA1s, SMC3^+/–, and MPL^W515K, providing 20 different T21 or disomy 21 (D21) induced pluripotent stem cell (iPSC) clones. GATA1s profoundly reshaped iPSC-derived hematopoietic architecture with gradual myeloid-to-megakaryocyte shift and megakaryocyte differentiation alteration upon addition of SMC3 and MPL mutations. Transcriptional, chromatin accessibility, and GATA1-binding data showed alteration of essential megakaryocyte differentiation genes, including NFE2 downregulation that was associated with loss of GATA1s binding and functionally involved in megakaryocyte differentiation blockage. T21 enhanced the proliferative phenotype, reproducing the cellular and molecular abnormalities of DS-AMKL. Our study provides an array of human cell–based models revealing individual contributions of different mutations to DS-AMKL differentiation blockage, a major determinant of leukemic progression.

Genetic Alterations of the Thrombopoietin/MPL/JAK2 Axis Impacting Megakaryopoiesis

Megakaryopoiesis is an original and complex cell process which leads to the formation of platelets. The homeostatic production of platelets is mainly regulated and controlled by thrombopoietin (TPO) and the TPO receptor (MPL)/JAK2 axis. Therefore, any hereditary or acquired abnormality affecting this signaling axis can result in thrombocytosis or thrombocytopenia. Thrombocytosis can be due to genetic alterations that affect either the intrinsic MPL signaling through gain-of-function (GOF) activity (MPL, JAK2, CALR) and loss-of-function (LOF) activity of negative regulators (CBL, LNK) or the extrinsic MPL signaling by THPO GOF mutations leading to increased TPO synthesis. Alternatively, thrombocytosis may paradoxically result from mutations of MPL leading to an abnormal MPL trafficking, inducing increased TPO levels by alteration of its clearance. In contrast, thrombocytopenia can also result from LOF THPO or MPL mutations, which cause a complete defect in MPL trafficking to the cell membrane, impaired MPL signaling or stability, defects in the TPO/MPL interaction, or an absence of TPO production.

Proton pump inhibitors in acute treatment of reflux oesophagitis : a cost-effectiveness analysis

BACKGROUND AND AIM

Gastro-oesophageal reflux disease is a common medical problem that places a significant financial burden on outpatient pharmaceutical expenditure. A substantial proportion of this expenditure can be attributed to the use of proton pump inhibitors (PPIs). The aim of this analysis was to evaluate the cost-effectiveness of PPIs currently licensed in Italy in the acute treatment of reflux oesophagitis.

METHODS

A decision analysis model that simulated the sequential management of reflux oesophagitis over the course of 8 weeks was constructed. Healing rates were derived from a published meta-analysis of PPIs for reflux oesophagitis. Costs of PPIs were based on retail prices in Italy, endoscopies and specialist (outpatient) visits were costed on the basis of public tariffs, and opportunity costs were calculated for general practitioner visits. The clinical effectiveness of a PPI was measured in terms of the proportion of patients healed at 8 weeks. An incremental cost-effectiveness analysis was performed, using omeprazole, the recognised 'gold standard' PPI in Italy, as the common comparator. The perspective of the analysis was the Italian National Health System (NHS). A sensitivity analysis was conducted in which the key parameters in the model were varied according to a Monte Carlo simulation of 1000 patients.

RESULTS

Esomeprazole 40 mg/day was a dominant treatment option compared with omeprazole 20 mg/day (88.8% patients healed vs 82.2%, respectively; total treatment cost euro164.85 vs euro169.56, respectively (year of costing, 2002). Furthermore, on the basis of the 95% CIs generated by the Monte Carlo simulation, esomeprazole 40 mg/day appears to be more cost-effective than both lansoprazole 30 mg/day and pantoprazole 40 mg/day.

CONCLUSIONS

Esomeprazole 40 mg/day can be considered a cost-effective treatment option for the acute treatment of reflux oesophagitis in Italy.

GOLD severity stratification and risk of hospitalisation for COPD exacerbations

BACKGROUND AND AIM

The Italian Costs for Exacerbations in COPD ("ICE") study, following a pharmacoeconomic assessment of costs due to COPD exacerbations (primary endpoint), aimed also at evaluating (secondary endpoint) which clinical factors, among those considered for cost-analysis, may, at follow up, present a risk of new exacerbations and re-admission to hospital.

MATERIALS AND METHODS

A prospective, multicentre study was carried out on COPD patients admitted to 25 Hospital Centres as a result of an exacerbation from October-December 2002. Following discharge, a 6-month follow-up was performed in each patient via three bi-monthly telephone interviews with a questionnaire administered by an investigator clinician.

RESULTS

570 patients were eligible for data processing, mean age 70.6 years (+/- 9.5 standard deviation, SD), males 69.2%. According to GOLD, severity stratification was as follows: moderate 36.4%; severe 31.3%; very severe 32.3%. 282 patients experienced at least one exacerbation at follow up, 42% of exacerbations requiring hospitalisation. No significant association was seen between exacerbations and GOLD stage or co-morbidities or treatments except LTOT. Conversely, COPD functional severity influenced hospitalisations very significantly, with relative risks 2.6 (95% Confidence Interval, CI 1.8-3.8) and 2.0 (CI 1.3-2.8) (GOLD very severe versus moderate and severe, respectively), and 1.3 (CI 0.85-2.1) (GOLD severe versus moderate). Hospitalisations were also significantly associated with treatments denoting more severe conditions (oral corticosteroids, oral theophylline, and LTOT).

CONCLUSIONS

Severity stratification of COPD patients according to respiratory function classes as outlined in GOLD guidelines and need for LTOT are confirmed as important predictors of hospitalisation for an exacerbation.

Il costo di una neutropenia febbrile

Febrile neutropenia (FN) is one of the most common and severe complications of chemotherapy, particularly when used for the treatment of hematological malignancies and bone marrow transplantation. Estimating its cost for the National Health service (NHS) is difficult, in that the cost of FN is included in the overall reimbursement, which is based on the main DRG declared at discharge. Aim of the present survey, conducted on the patient population treated in two oncology centers in Milan in the years 2001- 2002, was to evaluate the most frequent DRGs associated with neutropenia, with the objective to estimate the mean cost per patient hospitalized with FN. As expected, oncology patients with NF are spread through a wide range of DRGs, but the mean cost per patient resulted comparable in the two considered hospitals ( ~ 9500 euro), as well as the overall distribution among DRGs. The single most frequent DRG was 398 (diseases of reticuloendothelial and immune systems, with complications) which appears to be appropriate, being the closest to the clinical definition of FN available.

Utilisation Pattern of Nonspecific Nonsteroidal Anti-Inflammatory Drugs and COX-2 Inhibitors in a Local Health Service Unit in Northeast Italy

BACKGROUND AND OBJECTIVE

Nonsteroidal anti-inflammatory drugs (NSAIDs) are prescribed widely in Italy. They include nonspecific NSAIDs (NS-NSAIDs) and the newly marketed cyclo-oxygenase (COX)-2 specific inhibitors (COXIBs) celecoxib and rofecoxib. The objective of this study was to describe the prescribing patterns for NS-NSAIDs and COXIBs in a local Italian area, analysing an administrative database.

PATIENTS AND METHODS

We extracted from the database information on subjects who had received at least one reimbursed prescription of an NSAID during the period between 1 January 2001 and 31 December 2001, including age, sex, patient identification code, Anatomical Therapeutic Chemical (ATC) classification system code, strength, formulation, number of packs prescribed, prescription date, and prescription of gastroprotective agents (GPAs) on the same day as the prescription of the NSAID. On the basis of the type of NSAID received, we divided the patients into five cohorts: oral NS-NSAIDs only during the observed year, injectable NS-NSAIDs only, celecoxib only, rofecoxib only, and a combination. For descriptive purposes, we defined three age groups: <40 years, 40-64 years, and >64 years. The duration of exposure to NSAID therapy was calculated using the most commonly prescribed dose for the different drugs. Subjects receiving >/=30 doses per year were defined as "regular users". Analyses included mean age, mean duration of exposure, percentage of regular users, and percentage of GPAs co-prescribed in the different cohorts.

RESULTS

NSAIDs were prescribed to 62 059 subjects from a resident population of 365 321 inhabitants; 43.8% received oral NS-NSAIDs only, 22.6% injectable NS-NSAIDs only, 7.2% celecoxib only, 5.2% rofecoxib only, and 22% different regimens of different types of NSAIDs. The mean duration of treatment increased with age in all cohorts; the mean age was 56 years in the NS-NSAID cohort, 61 years in the celecoxib cohort, and 62 years in the rofecoxib cohort (p = 0.01, COXIBs vs NS-NSAIDs). The mean duration of therapy was 11.4 days/year for injectable NS-NSAIDs, 43.8 days/year for rofecoxib, 50.5 days/year for oral NS-NSAIDs, and 53.7 days/year for celecoxib. Fifty-four percent of subjects in the oral NS-NSAID cohort were regular users versus 64% in the rofecoxib and 70% in the celecoxib groups (p = 0.001, COXIBs vs NS-NSAIDs). Co-prescription with GPAs was 9.5% for NS-NSAIDs, 8.4% for rofecoxib, and 7.7% for celecoxib.

CONCLUSIONS

Analysis of an administrative database in Italy showed a trend suggesting that COXIBs are prescribed to an older population and for a longer period of time than NS-NSAIDs, and that their use is less frequently associated with GPAs.

Epidemiology and cost analysis of varicella in Italy: results of a sentinel study in the pediatric practice. Italian Sentinel Group on Pediatric Infectious Diseases

BACKGROUND

Describing the epidemiology of varicella is relevant to the development of specific prevention strategies and to building up of economic models evaluating the cost:efficiency ratios of these strategies.

AIM

Our study was designed to describe the epidemiology of chickenpox among Italian children and to assess the resulting economic and health burden on the country.

METHODS

Thirty-nine Italian pediatricians participated in a sentinel network on pediatric infectious diseases representing a total pediatric population of 30 168 children. Each case of varicella observed from January through December, 1997, was recorded. Economic analysis was conducted from the societal point of view. All costs were broken down into two groups: direct and indirect costs.

RESULTS

A total of 1599 cases of varicella were reported among children 0 to 14 years old. There were 1266 primary cases (mean age, 4.5 +/- 2 years) and 333 secondary cases (mean age, 3.6 +/- 3.2 years). The global incidence of chickenpox was 51.01/1000/year. Complications were seen in 56 cases (3.5%). Drugs were prescribed in 672 cases. A group of adults (364 susceptible and 193 with uncertain status) were exposed to primary cases. Seventy (12.5%) were eventually infected among whom there were 4 pregnant women. For pediatric patients an average cost of $146.90 (250 400 lire) was estimated; this is largely accounted for by indirect costs.

CONCLUSIONS

The epidemiology of varicella in Italy is consistent with that found in previous studies in industrialized countries. Severe complications did not occur in our population. We believe that the health arguments in favor of universal vaccination of children > 18 months of age do not differ in our own country from those of other industrialized nations. Our data could now be incorporated into pharmacoeconomic models to establish cost-efficient strategies for Italy.

Cost of an outbreak of hepatitis A in Puglia, Italy

In total, 5889 cases of hepatitis A virus infection were reported during an outbreak in Puglia, a region of Southern Italy, in 1996. The primary cause of the outbreak was consumption of contaminated food (raw shellfish, vegetables, etc.), with a contributory risk factor of person-to-person transmission. A detailed questionnaire was completed by 250 randomly selected patients to obtain information sufficient to calculate the direct and indirect costs of the outbreak for the individual patient, the National Health Service (NHS) and society as a whole. A conversion rate of $US1 = 1530 Italian lire (L) has been used throughout the study since this was the average exchange rate in 1996. For the individual patient with hepatitis A virus infection, the mean cost was L1.013 million ($US662), which was equivalent to 6.6% of the mean annual income of the employed patients. The total cost of the outbreak to the NHS was L23.98 billion ($US15.67 million), which was equivalent to 0.4% of the total public health expenditure in the region in 1996. The total cost of the outbreak to society (individual patient, NHS and third parties combined) was L37.406 billion ($US24.45 million), corresponding to 0.04% of the gross domestic product of the entire region in 1996, with a mean cost per patient of L6.35 million ($US4150) from a societal perspective. The majority of patients (86.3%) were 11 to 30 years of age, reflecting the increasing susceptibility of younger patients to hepatitis A virus infection in recent decades. These economic and demographic data provide important information for the evaluation of preventive strategies including public education, sanitation and immunisation, so as to optimise the use of local health resources.