Cost-Utility Analysis Comparing Pegcetacoplan to Anti-C5 Monoclonal Antibodies in the Treatment of Paroxysmal Nocturnal Hemoglobinuria

Background

Paroxysmal nocturnal hemoglobinuria is a rare, acquired disease characterized by hemolytic episodes and associated with significant clinical burden. The introduction of C5 inhibitory monoclonal antibodies (C5i) represented a major breakthrough in PNH treatment, effectively reducing intravascular hemolysis (IVH) but showing limited impact on extravascular hemolysis (EVH). In 2021, the C3 inhibitor pegcetacoplan was approved by EMA and recently reimbursed in Italy, which also has the advantages in the reduction of both IVH and EVH, increasing hemoglobin values and simultaneously improving the quality of life and fatigue of patients. A cost-utility analysis was developed to compare pegcetacoplan to C5i (eculizumab and ravulizumab) in the PNH population who remain anemic after treatment with C5i for at least 3 months.

Materials and Methods

The analysis employed a Markov model with a 5-year time horizon whereby patients can transition among 3 PNH health states, adopting the perspective of the Italian NHS. Efficacy data were sourced from the PEGASUS study, with drug prices reflecting ex-factory costs. Additionally, costs associated with resource utilization, adverse events, and complications were estimated based on outpatient and hospital care rates, excluding indirect expenses. Utility and disutility values related to transfusions were also considered, with pegcetacoplan allowing for dose escalation.

Results

The cumulative cost of treatment per individual patient at 5 years was estimated to be €1,483,454 for pegcetacoplan, €1,585,763 for eculizumab, and €1,574,826 for ravulizumab. Pegcetacoplan demonstrated a superior increase in quality-adjusted life years (QALYs) compared to both eculizumab (0.51 increase) and ravulizumab (0.27 increase). Furthermore, pegcetacoplan showed a reduction in complication management costs (€22,891 less compared to eculizumab and €22,611 less compared to ravulizumab) and lower transfusion-related expenses (€14,147 less than both C5i treatments).

Conclusion

Pegcetacoplan emerged as the dominant strategy in this analysis, being more effective, less expensive and improves quality of life in the analyzed population affected by PNH.

Oral Iptacopan Monotherapy in Paroxysmal Nocturnal Hemoglobinuria

BACKGROUND

Persistent hemolytic anemia and a lack of oral treatments are challenges for patients with paroxysmal nocturnal hemoglobinuria who have received anti-C5 therapy or have not received complement inhibitors. Iptacopan, a first-in-class oral factor B inhibitor, has been shown to improve hemoglobin levels in these patients.

METHODS

In two phase 3 trials, we assessed iptacopan monotherapy over a 24-week period in patients with hemoglobin levels of less than 10 g per deciliter. In the first, anti-C5-treated patients were randomly assigned to switch to iptacopan or to continue anti-C5 therapy. In the second, single-group trial, patients who had not received complement inhibitors and who had lactate dehydrogenase (LDH) levels more than 1.5 times the upper limit of the normal range received iptacopan. The two primary end points in the first trial were an increase in the hemoglobin level of at least 2 g per deciliter from baseline and a hemoglobin level of at least 12 g per deciliter, each without red-cell transfusion; the primary end point for the second trial was an increase in hemoglobin level of at least 2 g per deciliter from baseline without red-cell transfusion.

RESULTS

In the first trial, 51 of the 60 patients who received iptacopan had an increase in the hemoglobin level of at least 2 g per deciliter from baseline, and 42 had a hemoglobin level of at least 12 g per deciliter, each without transfusion; none of the 35 anti-C5-treated patients attained the end-point levels. In the second trial, 31 of 33 patients had an increase in the hemoglobin level of at least 2 g per deciliter from baseline without red-cell transfusion. In the first trial, 59 of the 62 patients who received iptacopan and 14 of the 35 anti-C5-treated patients did not require or receive transfusion; in the second trial, no patients required or received transfusion. Treatment with iptacopan increased hemoglobin levels, reduced fatigue, reduced reticulocyte and bilirubin levels, and resulted in mean LDH levels that were less than 1.5 times the upper limit of the normal range. Headache was the most frequent adverse event with iptacopan.

CONCLUSIONS

Iptacopan treatment improved hematologic and clinical outcomes in anti-C5-treated patients with persistent anemia - in whom iptacopan showed superiority to anti-C5 therapy - and in patients who had not received complement inhibitors. (Funded by Novartis; APPLY-PNH ClinicalTrials.gov number, NCT04558918; APPOINT-PNH ClinicalTrials.gov number, NCT04820530.).

The inhibition of several components of terminal complement pathway results in C3 binding to PNH red blood cells

C3 binding on PNH red blood cells after in vitro complement activation in normal and terminal complement depleted (∆5, ∆6, ∆9) sera: C3 binding, and the subsequent extravascular hemolysis, happens anytime there is a block of a component of the terminal complement pathway.

SNP of Aromatase Predict Long-term Survival and Aromatase Inhibitor Toxicity in Patients with Early Breast Cancer: A Biomarker Analysis of the GIM4 and GIM5 Trials

PURPOSE

In estrogen receptor-positive (ER+) breast cancer, single-nucleotide polymorphisms (SNP) in the aromatase gene might affect aromatase inhibitors (AI) metabolism and efficacy. Here, we assessed the impact of SNP on prognosis and toxicity of patients receiving adjuvant letrozole.

EXPERIMENTAL DESIGN

We enrolled 886 postmenopausal patients in the study. They were treated with letrozole for 2 to 5 years after taking tamoxifen for 2 to 6 years, continuing until they completed 5 to 10 years of therapy. Germline DNA was genotyped for SNP rs4646, rs10046, rs749292, and rs727479. Log-rank test and Cox model were used for disease-free survival (DFS) and overall survival (OS). Cumulative incidence (CI) of breast cancer metastasis was assessed through competing risk analysis, with contralateral breast cancer, second malignancies and non-breast cancer death as competing events. CI of skeletal and cardiovascular events were assessed using DFS events as competing events. Subdistribution HR (sHR) with 95% confidence intervals were calculated through Fine-Gray method.

RESULTS

No SNP was associated with DFS. Variants rs10046 [sHR 2.03, (1.04-2.94)], rs749292 [sHR 2.11, (1.12-3.94)], and rs727479 [sHR 2.62, (1.17-5.83)] were associated with breast cancer metastasis. Three groups were identified on the basis of the number of these variants (0, 1, >1). Variant-based groups were associated with breast cancer metastasis (10-year CI 2.5%, 7.6%, 10.7%, P = 0.035) and OS (10-year estimates 96.5%, 93.0%, 89.6%, P = 0.030). Co-occurrence of rs10046 and rs749292 was negatively associated with 10-year CI of skeletal events (3.2% vs. 10%, P = 0.033). A similar association emerged between rs727479 and cardiovascular events (0.3% vs. 2.1%, P = 0.026).

CONCLUSIONS

SNP of aromatase gene predict risk of metastasis and AI-related toxicity in ER+ early breast cancer, opening an opportunity for better treatment individualization.

Identification and characterization of novel ETV4 splice variants in prostate cancer

ETV4, one of ETS proteins overexpressed in prostate cancer, promotes migration, invasion, and proliferation in prostate cells. This study identifies a series of previously unknown ETV4 alternatively spliced transcripts in human prostate cell lines. Their expression has been validated using several unbiased techniques, including Nanopore sequencing. Most of these transcripts originate from an in-frame exon skipping and, thus, are expected to be translated into ETV4 protein isoforms. Functional analysis of the most abundant among these isoforms shows that they still bear an activity, namely a reduced ability to promote proliferation and a residual ability to regulate the transcription of ETV4 target genes. Alternatively spliced genes are common in cancer cells: an analysis of the TCGA dataset confirms the abundance of these novel ETV4 transcripts in prostate tumors, in contrast to peritumoral tissues. Since none of their translated isoforms have acquired a higher oncogenic potential, such abundance is likely to reflect the tumor deranged splicing machinery. However, it is also possible that their interaction with the canonical variants may contribute to the biology and the clinics of prostate cancer. Further investigations are needed to elucidate the biological role of these ETV4 transcripts and of their putative isoforms.

Management of infection in PNH patients treated with eculizumab or other complement inhibitors: Unmet clinical needs

This article presents the results of group discussion among an ad hoc constituted panel of experts aimed at identifying and addressing unmet clinical needs (UCNs) in the management of infectious risk associated with eculizumab or new terminal complement inhibitors (CIs) in paroxysmal nocturnal hemoglobinuria (PNH). With the Delphi technique, the most clinically relevant UCNs in PNH patients candidate to or on terminal CI were selected. They resulted to be: optimizing the infection prevention measures; developing non pharmacological infectious risk-mitigation strategies; improving the management of disease exacerbation during infectious complications. For each of these issues consensus opinions were provided and, when appropriate, proposals for advancement in clinical practice were addressed. The hope is that this comprehensive overview will serve to improve the practice of CIs therapy and inform the design and implementation of new studies in the field.

Abstract P3-09-03: Single nucletotide polymorphisms of aromatase gene (CYP19A1) and toxicity of adjuvant aromatase inhibitors: A translational, prospective study

Background: Extending adjuvant endocrine treatment (ET) with aromatase inhibitors (AI) to 7-10 years decreases the risk of relapse in hormone receptor-positive (HR+) breast cancer (BC). However, such benefit comes at the price of higher incidence of skeletal and cardiovascular (CV) events. Biomarkers predicting such toxicities might help clinicians in tailoring adjuvant ET to patient’s needs. We conducted a prospective study to assess whether SNPs in the gene encoding for the aromatase enzyme (CYP19A1) affect the risk of skeletal and CV events in HR+ early BC patients enrolled in the GIM4 trial. Methods: The GIM4 trial randomized HR+ BC postmenopausal patients who had been already treated with 2-3 years of adjuvant tamoxifen to either 3-2 years or 5 years of adjuvant letrozole. Four SNPs of CYP19A1 were evaluated: rs10046, rs4646, rs479292 and rs727479. SNPs were genotyped through PCR on DNA obtained from patients’ peripheral blood samples. Skeletal and CV events were assessed from randomization in the GIM4 trial to last follow-up, disease recurrence or death. Skeletal events were defined as the onset of osteoporosis or bone fractures. CV events were defined as the onset of thrombosis, embolism, stroke, myocardial infarction, hearth failure, or arrythmia. Univariate and multivariate logistic regressions were performed to evaluate the association between SNPs and skeletal and CV events. Bonferroni correction for multiplicity was used for univariate SNPs association tests, with a corrected alpha of 0.012. Only associations with an alpha level <0.012 were considered significant and included in multivariate models.Multivariate models’ covariates included: treatment arm (5 vs 3-2 years letrozole), (neo)adjuvant chemotherapy, previous hormone replacement therapy, age, BMI, previous biphosphonates, hypercholesterolemia and hypertension at baseline. SNPs were tested for Hardy–Weinberg equilibrium (HWE) and linkage disequilibrium (LD). Interaction between SNPs of interest and treatment arm was also investigated. Results: Of 2,056 patients enrolled in the GIM4 trial, 647 entered this translational study. All SNPs were in HWE. The CT and TT variants of rs10046 were less associated to skeletal events compared to variant CC, suggesting a dominant effect of the minor T allele (odds ratio [OR]: 0.47,. 95% confidence interval [CI]: 0.28-0.79, p=0.005). The association was independent from the other covariates (adjusted OR [aOR]: 0.43, p=0.002). Patients with rs10046-TT had no significant differences in the odd of skeletal events according to treatment arm. Conversely, in patients with rs10046-CC, skeletal events were more likely with 5-year letrozole (interaction p=0.043). Compared to rs10046-CC, rs10046-TT/CT was also less associated with CV events at both univariate (OR: 0.46 95% CI: 0.27-077, p=0.003) and multivariate analysis (aOR: 0.41, p<0.001).The rs727479—GG variant was associated with more CV events compared to the GT and TT variants (OR: 2.30, 95%CI: 1.27-4.15, p=0.009), suggesting a recessive effect of the minor G allele. The association remained significant at multivariate analysis (aOR: 2.30, p=0.010). No significant interaction was observed among treatment arms, rs10046 or rs272479 variants (interaction p=0.070 and 0.061). Rs10046-CC and rs727479-GG variants were in high LD (D’=0.92, haplotype-CG frequency: 39%). Hence, the association between genotype rs10046-CC/rs727479-GG and CV events was investigated. The association was significant at the multivariate analysis (aOR: 2.79, p=0.002). With such genotype, the odd of CV events was significantly increased with the 5-year letrozole (interaction p=0.046). Conclusions: SNPs of CYP19A1 could be useful biomarkers of long-term toxicity in HR+ BC patients who are candidates for adjuvant AI.

Citation Format: Benedetta Conte, Chiara Molinelli, Giancarlo Bisagni, Antonio Durando, Giovanni Sanna, Stefania Gori, Ornella Garrone, Stefano Tamberi, Sabino De Placido, Francesco Schettini, Antonio Pazzola, Riccardo Ponzone, Filippo Montemurro, Gianluigi Lunardi, Rosario Notaro, Anna Turletti, Claudia Bighin, Francesca Poggio, Giulia Buzzatti, Matteo Lambertini, Luca Boni, Lucia Del Mastro. Single nucletotide polymorphisms of aromatase gene (CYP19A1) and toxicity of adjuvant aromatase inhibitors: A translational, prospective study [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-09-03.

Danicopan: an oral complement factor D inhibitor for paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is characterised by complement-mediated intravascular hemolysis (IVH) due to absence of complement regulators CD55 and CD59 on affected erythrocytes. Danicopan is a first-in-class oral proximal, complement alternative pathway factor D (FD) inhibitor. Therapeutic FD inhibition was designed to control IVH and prevent C3-mediated extravascular hemolysis (EVH). In this open-label, phase 2, dose-finding trial, 10 untreated hemolytic PNH patients received danicopan monotherapy (100-200 mg thrice daily). Endpoints included change in lactate dehydrogenase (LDH) at day 28 (primary) and day 84 and hemoglobin. Safety, pharmacokinetics/pharmacodynamics, and patient-reported outcomes were measured. Ten patients reached the primary endpoint; two later discontinued: one for a serious adverse event (elevated aspartate aminotransferase/alanine aminotransferase coincident with breakthrough hemolysis, resolving without sequelae) and one for personal reasons unrelated to safety. Eight patients completed treatment. IVH was inhibited, demonstrated by mean decreased LDH (5.7 times upper limit of normal [ULN] at baseline vs 1.8 times ULN [day 28] and 2.2 times ULN [day 84]; both p.

ETV4 promotes late development of prostatic intraepithelial neoplasia and cell proliferation through direct and p53-mediated downregulation of p21

BACKGROUND

ETV4 is one of the ETS proteins overexpressed in prostate cancer (PC) as a result of recurrent chromosomal translocations. In human prostate cell lines, ETV4 promotes migration, invasion, and proliferation; however, its role in PC has been unclear. In this study, we have explored the effects of ETV4 expression in the prostate in a novel transgenic mouse model.

METHODS

We have created a mouse model with prostate-specific expression of ETV4 (ETV4 mice). By histochemical and molecular analysis, we have investigated in these engineered mice the expression of p21, p27, and p53. The implications of our in vivo findings have been further investigated in human cells lines by chromatin-immunoprecipitation (ChIP) and luciferase assays.

RESULTS

ETV4 mice, from two independent transgenic lines, have increased cell proliferation in their prostate and two-thirds of them, by the age of 10 months, developed mouse prostatic intraepithelial neoplasia (mPIN). In these mice, cdkn1a and its p21 protein product were reduced compared to controls; p27 protein was also reduced. By ChIP assay in human prostate cell lines, we show that ETV4 binds to a specific site (-704/-696 bp upstream of the transcription start) in the CDKN1A promoter that was proven, by luciferase assay, to be functionally competent. ETV4 further controls CDKN1A expression by downregulating p53 protein: this reduction of p53 was confirmed in vivo in ETV4 mice.

CONCLUSIONS

ETV4 overexpression results in the development of mPIN but not in progression to cancer. ETV4 increases prostate cell proliferation through multiple mechanisms, including downregulation of CDKN1A and its p21 protein product: this in turn is mediated through direct binding of ETV4 to the CDKN1A promoter and through the ETV4-mediated decrease of p53. This multi-faceted role of ETV4 in prostate cancer makes it a potential target for novel therapeutic approaches that could be explored in this ETV4 transgenic model.

Anti-complement Treatment for Paroxysmal Nocturnal Hemoglobinuria: Time for Proximal Complement Inhibition? A Position Paper From the SAAWP of the EBMT

The treatment of paroxysmal nocturnal hemoglobinuria has been revolutionized by the introduction of the anti-C5 agent eculizumab; however, eculizumab is not the cure for Paroxysmal nocturnal hemoglobinuria (PNH), and room for improvement remains. Indeed, the hematological benefit during eculizumab treatment for PNH is very heterogeneous among patients, and different response categories can be identified. Complete normalization of hemoglobin (complete and major hematological response), is seen in no more than one third of patients, while the remaining continue to experience some degree of anemia (good and partial hematological responses), in some cases requiring regular red blood cell transfusions (minor hematological response). Different factors contribute to residual anemia during eculizumab treatment: underlying bone marrow dysfunction, residual intravascular hemolysis and the emergence of C3-mediated extravascular hemolysis. These two latter pathogenic mechanisms are the target of novel strategies of anti-complement treatments, which can be split into terminal and proximal complement inhibitors. Many novel terminal complement inhibitors are now in clinical development: they all target C5 (as eculizumab), potentially paralleling the efficacy and safety profile of eculizumab. Possible advantages over eculizumab are long-lasting activity and subcutaneous self-administration. However, novel anti-C5 agents do not improve hematological response to eculizumab, even if some seem associated with a lower risk of breakthrough hemolysis caused by pharmacokinetic reasons (it remains unclear whether more effective inhibition of C5 is possible and clinically beneficial). Indeed, proximal inhibitors are designed to interfere with early phases of complement activation, eventually preventing C3-mediated extravascular hemolysis in addition to intravascular hemolysis. At the moment there are three strategies of proximal complement inhibition: anti-C3 agents, anti-factor D agents and anti-factor B agents. These agents are available either subcutaneously or orally, and have been investigated in monotherapy or in association with eculizumab in PNH patients. Preliminary data clearly demonstrate that proximal complement inhibition is pharmacologically feasible and apparently safe, and may drastically improve the hematological response to complement inhibition in PNH. Indeed, we envision a new scenario of therapeutic complement inhibition, where proximal inhibitors (either anti-C3, anti-FD or anti-FB) may prove effective for the treatment of PNH, either in monotherapy or in combination with anti-C5 agents, eventually leading to drastic improvement of hematological response.

C3-mediated extravascular hemolysis in PNH on eculizumab: Mechanism and clinical implications

The introduction of eculizumab, a human monoclonal antibody against the C5 component of complement, has changed radically the management of paroxysmal nocturnal hemoglobinuria (PNH). The blockade of the terminal complement pathway by eculizumab abrogates intravascular hemolysis, reduces the transfusion requirement and the risk of thrombosis in most of hemolytic PNH patients. However, in almost all PNH patients on eculizumab arises a fraction of PNH red cells that bind fragments of C3 and become a potential target of phagocytosis by macrophages. Eventually, this phagocytosis results in a variable degree of extravascular hemolysis that may reduce clinical benefits of eculizumab and, in fact, about one-fourth of patients remain transfusion-dependent. The treatment of the few PNH patients in which this de novo extravascular hemolysis become clinically relevant is still unsatisfactory. Nevertheless, the investigations of the mechanisms responsible of the extravascular hemolysis on eculizumab have resulted in the development of novel strategies for complement blockade that could overcome this condition.

Eculizumab treatment: stochastic occurrence of C3 binding to individual PNH erythrocytes

BACKGROUND

C5 blockade by eculizumab prevents complement-mediated intravascular hemolysis in paroxysmal nocturnal hemoglobinuria (PNH). However, C3-bound PNH red blood cells (RBCs), arising in almost all treated patients, may undergo extravascular hemolysis reducing clinical benefits. Despite the uniform deficiency of CD55 and of CD59, there are always two distinct populations of PNH RBCs, with (C3+) and without (C3-) C3 binding.

METHODS

To investigate this paradox, the phenomenon has been modeled in vitro by incubating RBCs from eculizumab untreated PNH patients with compatible sera containing eculizumab, and by assessing the C3 binding after activation of complement alternative pathway.

RESULTS

When RBCs from untreated patients were exposed in vitro to activated complement in the context of C5-blockade, there was the prompt appearance of a distinct C3+ PNH RBC population whose size increased with time and also with the rate of complement activation. Eventually, all PNH RBCs become C3+ to the same extent, without differences between old and young (reticulocytes) PNH RBCs.

CONCLUSIONS

This study indicates that the distinct (C3+ and C3-) PNH RBC populations are not intrinsically different; rather, they result from a stochastic all-or-nothing phenomenon linked to the time-dependent cumulative probability of each individual PNH red cell to be exposed to levels of complement activation able to trigger C3 binding. These findings may envision novel approaches to reduce C3 opsonization and the subsequent extravascular hemolysis in PNH patients on eculizumab.

Glucose-6-Phosphate Dehydrogenase Deficiency

G6PD is a housekeeping gene expressed in all cells. Glucose-6-phosphate dehydrogenase (G6PD) is part of the pentose phosphate pathway, and its main physiologic role is to provide NADPH. G6PD deficiency, one of the commonest inherited enzyme abnormalities in humans, arises through one of many possible mutations, most of which reduce the stability of the enzyme and its level as red cells age. G6PD-deficient persons are mostly asymptomatic, but they can develop severe jaundice during the neonatal period and acute hemolytic anemia when they ingest fava beans or when they are exposed to certain infections or drugs. G6PD deficiency is a global health issue.

Is green tea a potential trigger for autoimmune hepatitis?

A case of autoimmune liver hepatitis is reported: the onset was triggered by consumption of green tea infusion in a patient taking oral contraceptives and irbesartan. We hypothesize that our patient, carrying genetic variant of hepatic metabolism making her particularly susceptible to oxidative stress, developed an abnormal response to a mild toxic insult, afforded by a combination of agents (oral contraceptives+irbesartan+green tea) that normally would not be able to cause damage. Her particular hepatic metabolism further increased the drugs' concentration, favoring the haptenization of liver proteins, eventually leading to the development of an autoimmune hepatitis.

Polymorphism of the complement receptor 1 gene correlates with the hematologic response to eculizumab in patients with paroxysmal nocturnal hemoglobinuria

Complement blockade by eculizumab is clinically effective in hemolytic paroxysmal nocturnal hemoglobinuria. However, the response is variable and some patients remain dependent on red blood cell transfusions. In 72 patients with hemolytic paroxysmal nocturnal hemoglobinuria on eculizumab we tested the hypothesis that response may depend on genetic polymorphisms of complement-related genes. We found no correlation between the complement component C3 genotypes and the need for blood transfusions. On the other hand, we found a significant correlation with the HindIII polymorphism of a complement regulatory gene, the complement receptor 1 (CR1) gene. At this locus two co-dominant alleles are known, of which H (common) is associated with high expression, whereas L (rare) is associated with low expression of CR1 on red blood cells. Patients who still needed blood transfusion on eculizumab accounted for 18% of the H/H homozygotes, 33% of the H/L heterozygotes and 68% of the L/L homozygotes (P=0.016). Thus, patients with paroxysmal nocturnal hemoglobinuria who have the L/L genotype are seven times more likely to be sub-optimal responders to eculizumab. Both in vitro and in vivo we found that the CR1 HindIII genotype correlates with the abundance of paroxysmal nocturnal hemoglobinuria red cells that have bound C3, and with the kinetics of C3 binding. These results are consistent with the notion that by affecting C3 binding the CR1 genotype influences the response to eculizumab treatment, and this emerges as a novel example of pharmacogenetics.

The frequency of granulocytes with spontaneous somatic mutations: a wide distribution in a normal human population

Germ-line mutation rate has been regarded classically as a fundamental biological parameter, as it affects the prevalence of genetic disorders and the rate of evolution. Somatic mutation rate is also an important biological parameter, as it may influence the development and/or the course of acquired diseases, particularly of cancer. Estimates of this parameter have been previously obtained in few instances from dermal fibroblasts and lymphoblastoid cells. However, the methodology required has been laborious and did not lend itself to the analysis of large numbers of samples. We have previously shown that the X-linked gene PIG-A, since its product is required for glycosyl-phosphatidylinositol-anchored proteins to become surface bound, is a good sentinel gene for studying somatic mutations. We now show that by this approach we can accurately measure the proportion of PIG-A mutant peripheral blood granulocytes, which we call mutant frequency, ƒ. We found that the results are reproducible, with a variation coefficient (CV) of 45%. Repeat samples from 32 subjects also had a CV of 44%, indicating that ƒ is a relatively stable individual characteristic. From a study of 142 normal subjects we found that log ƒ is a normally distributed variable; ƒ variability spans a 80-fold range, from less than 1×10⁻⁶ to 37.5×10⁻⁶, with a median of 4.9×10⁻⁶. Unlike other techniques commonly employed in population studies, such as comet assay, this method can detect any kind of mutation, including point mutation, as long as it causes functional inactivation of PIG-A gene. Since the test is rapid and requires only a small sample of peripheral blood, this methodology will lend itself to investigating genetic factors that underlie the variation in the somatic mutation rate, as well as environmental factors that may affect it. It will be also possible to test whether ƒ is a determinant of the risk of cancer.

A systematic analysis of bone marrow cells by flow cytometry defines a specific phenotypic profile beyond GPI deficiency in paroxysmal nocturnal hemoglobinuria

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH) is a unique disorder caused by a PIG-A gene mutation in a stem cell clone. Its clinical picture can sometimes make challenging the distinction from other disorders, and especially from myelodysplastic syndromes (MDS), since both diseases correlate with cytopenias and morphological abnormalities of bone marrow (BM) cells. Recently, flow cytometry (FC) has been proposed to integrate the morphologic assessment of BM dysplasia, and thus to improve the diagnostics of MDS.

METHODS

In the present study, we have analyzed systematically FC data resulting from the study of BM cells from patients with PNH and MDS.

RESULTS

Our data demonstrated abnormalities in PNH beyond the deficiency of glycosylphosphatidylinositol-linked proteins and the application of a systematic approach allowed us to separate effectively MDS and PNH in a cluster analysis and to highlight disease-specific abnormalities. Indeed, the parallel evaluation of some key parameters, i.e. patterns of expression of CD45 and CD10, provided information with practical diagnostic usefulness in the distinction between PNH and MDS. Moreover, the hypo-expression of CD36 that we observed on monocytes might be related to the thrombotic tendency in PNH.

CONCLUSIONS

We investigated systematically the phenotypic profile of BM cells from patients with PNH; our data provide useful antigenic patterns to solve between PNH and MDS, sometimes morphologically overlapping. Moreover, some PNH-related phenotypic changes might be involved in the physiopathology of the disease and further studies addressing this issue are warranted.

Killer immunoglobulin-like receptors (KIR) and their HLA-ligands in Italian paroxysmal nocturnal haemoglobinuria (PNH) patients

Paroxysmal nocturnal haemoglobinuria (PNH) is a haematopoietic disorder characterized by expansion of phosphatidylinositol glycan-A-defective progenitor(s). Immune-dependent mechanisms, likely involving a deranged T cell-dependent autoimmune response, have been consistently associated with the selection/dominance of PNH precursors. Natural killer (NK) lymphocytes might participate in PNH pathogenesis, but their role is still controversial. NK activity is dependent on the balance between activating and inhibiting signals. Key component in such regulatory network is represented by killer immunoglobulin-like receptors (KIR). KIR are also involved in the regulation of adaptive cytotoxic T cell response and associated with autoimmunity. This study investigated on the frequency of KIR genes and their known human leukocyte antigen (HLA) ligands in 53 PNH Italian patients. We observed increased frequency of genotypes characterized by ≤2 activating KIR as well as by the presence of an inhibitory/activating gene ratio ≥3.5. In addition, an increased matching between KIR-3DL1 and its ligand HLA-Bw4 was found. These genotypes might be associated with lower NK-dependent recognition of stress-related self molecules; this is conceivable with the hypothesis that an increased availability of specific T cell targets, not cleared by NK cells, could be involved in PNH pathogenesis. These data may provide new insights into autoimmune PNH pathogenesis.

Eculizumab treatment modifies the immune profile of PNH patients

Paroxysmal Nocturnal Haemoglobinuria (PNH) is due to pathological expansion of a stem progenitor bearing a somatic mutation of PIG-A gene involved in the biosynthesis of the glycosyl-phosphatidyl-inositol (GPI) anchor. Numerous data suggest a role for immune-mediated mechanisms in the selection/expansion of GPI-defective clone. Haemolytic anaemia in PNH is dependent on the effect of complement against GPI-defective red cells. Eculizumab, an anti-C5 monoclonal antibody, is dramatically effective in controlling haemolysis and thrombosis, in reducing fatigue and in improving quality of life of patients. However, this therapy presents new challenges that need to be properly faced. Here, we report the decrease in B, Natural Killer (NK) and regulatory T cells (Treg), an altered cytokine profile of invariant-NKT cells (NKTi) and the increasing of C-X-C chemokine receptor type 4 (CXCR4) receptor in PNH patients before the Eculizumab therapy. Treatment significantly affects some of these alterations: after Eculizumab, the number of B lymphocytes, the cytokine secretion of NKTi and CXCR4 expression on CD8 T cells became similar to healthy donors. No effects were observed on NK and Treg. The amplitude of the GPI-defective compartment remained unchanged.

Thrombolytic therapy is effective in paroxysmal nocturnal hemoglobinuria: a series of nine patients and a review of the literature

BACKGROUND

Thrombosis is the major risk factor for death in patients with paroxysmal nocturnal hemoglobinuria. Previous case reports indicate that venous thrombosis in patients with paroxysmal nocturnal hemoglobinuria is amenable to thrombolysis.

DESIGN AND METHODS

We reviewed the outcome of thrombolytic therapy for patients with paroxysmal nocturnal hemoglobinuria who had thromboses refractory to anticoagulation at our institutions.

RESULTS

In this study of 41 patients who had at least one thrombotic event, we confirmed a very high incidence of recurrence despite anticoagulation. Nine patients with thrombosis were regarded as eligible for administration of intravenous tissue plasminogen activator, which was effective in reversing thrombi in all of 15 occasions in which it was given. Serious hemorrhagic complications developed in three cases. At last follow-up visit, of the nine patients treated, three had died, and six were in very good to excellent condition in terms of clinical outcome and radiological findings. The only patient in whom thrombolysis may have contributed to a fatal outcome also had complications of "heparin induced thrombocytopenia with thrombosis", which we diagnosed in three additional patients. In our review of the literature, nine out of 15 patients treated with thrombolysis have had a good outcome.

CONCLUSIONS

Although it is associated with a significant but manageable risk of bleeding, systemic thrombolysis is a highly effective treatment for reversing venous thromboses in patients with paroxysmal nocturnal hemoglobinuria.

Easy genotyping of complement C3 'slow' and 'fast' allotypes by tetra-primer amplification refractory mutation system PCR

Complement C3 'slow' and 'fast' allotypes are associated with immune-mediated disorders and may affect the outcome of renal transplantation. We report a tetra-primer amplification refractory mutation system PCR (T-ARMS-PCR) that provides a rapid, reproducible and cost-effective method to genotype both complement C3 'slow' and 'fast' alleles by a single tube reaction.

Excellent prognosis and prevalence of HCV infection of primary hepatic and splenic non-Hodgkin's lymphoma

BACKGROUND

Primary Hepatic (PHL) and Primary Splenic (PSL) non-Hodgkin's Lymphoma are rare entities. Small series of PHL and PSL have been reported, suggesting a non-fortuitous association with Hepatitis C Virus (HCV) infection. The prognosis is believed to be dismal, with early recurrence and short survival.

PATIENTS

We retrospectively reviewed all PHL and PSL patients diagnosed at our institution between 1990 and 2005.

RESULTS

Twenty-five adult patients were identified, six with PHL and 19 with PSL. Twenty-four patients had a B-cell lymphoma, defined as Diffuse Large B-cell lymphoma in 18. The prevalence of HCV infection was 68% among PSL and 66% among PHL. Combination chemotherapy was the mainstay of treatment for PHL and PSL; all but one patient with PSL underwent splenectomy before chemotherapy. Complete remission was achieved in all the cases after frontline therapy; only four patients relapsed but responded to additional chemotherapy courses. Most patients presented with aggressive histological subtypes; 92% were alive at a median follow up of 79 months. HCV infection did not appear to influence the results of therapy.

CONCLUSION

Our study confirms the rarity of PHL and PSL, shows a high prevalence of HCV infection, and demonstrates that the outcome of patients with PHL and PSL may be favourable.

Paroxysmal nocturnal hemoglobinuria: significant association with specific HLA-A, -B, -C, and -DR alleles in an Italian population

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by the expansion of a PIG-A mutated hematopoietic stem cell. An immune-mediated origin has been suggested for this disease. Because HLA genes represent a susceptibility factor for autoimmunity, we investigated HLA genotype in 42 Italian PNH patients compared with 301 control subjects of the same ethnic origin. A significantly increased frequency of the HLA class I alleles A*0201 (p < 0.05), B*1402 (p < 0.001), and Cw*0802 (p < 0.005), and of the HLA class II DRB1*1501 (p < 0.01) with the linked DQB1*0602 (p </= 0.05) and DRB1*01 (p </= 0.05) with the linked DQB1*0501 (p </= 0.01) alleles, has been observed. Notably, a fourfold increase of the haplotype B*1402, Cw*0802 (p < 0.0005) and a 15-fold increase of the Mediterranean haplotype A*33, B*1402, Cw*0802, DRB1*0102, DQB1*0501 (p < 0.005) was also revealed. This association may provide new insights into the autoimmune pathogenesis of PNH.

Association of -318 C/T and +49 A/G cytotoxic T lymphocyte antigen-4 (CTLA-4) gene polymorphisms with a clinical subset of Italian patients with systemic sclerosis

Systemic sclerosis (SSc) is a complex and heterogeneous autoimmune disorder with a multi-factorial pathogenesis. Like other autoimmune disorders, the possible role of specific cytotoxic T lymphocyte antigen-4 (CTLA-4) gene polymorphisms in predisposing to SSc has been hypothesized, but it remains controversial. CTLA-4 promoter (-318C/T) and exon 1 (+49 A/G) polymorphisms have been analysed in 43 Italian females with SSc and in 93 unrelated matched healthy controls by a newly designed tetra-primer amplification refractory mutation system-polymerase chain reaction (T-ARMS-PCR) method. No significant association has been found with either polymorphisms.Nevertheless, SSc patients without concomitant Hashimoto's thyroiditis (HT) were carrying both the -318T allele (P = 0.031) and the +49 G allele (P = 0.076) more frequently than SSc patients with HT [defined by positivity for anti-thyroperoxidase (TPO) and anti-thyroglobulin (TGA) autoantibodies] than controls. Haplotype analysis confirms this association (P = 0.028), and suggests the predominant role of the -318T, whereas that of the +49 G, if any, seems weak. Thus, in Italian SSc patients the CTLA-4 -318C/T promoter polymorphism appears to be associated with the susceptibility to develop SSc without thyroid involvement. Larger studies are needed to confirm these findings and to clarify whether the -318C/T polymorphism is the functional responsible or whether it reflects the presence of another linked genetic element in the same chromosomal region.

Highly homologous T-cell receptor beta sequences support a common target for autoreactive T cells in most patients with paroxysmal nocturnal hemoglobinuria

Deficiency of glycosylphosphatidylinositol (GPI)-anchored molecules on blood cells accounts for most features of paroxysmal nocturnal hemoglobinuria (PNH) but not for the expansion of PNH (GPI(-)) clone(s). A plausible model is that PNH clones expand by escaping negative selection exerted by autoreactive T cells against normal (GPI(+)) hematopoiesis. By a systematic analysis of T-cell receptor beta (TCR-beta) clonotypes of the CD8+ CD57+ T-cell population, frequently deranged in PNH, we show recurrent clonotypes in PNH patients but not in healthy controls: 11 of 16 patients shared at least 1 of 5 clonotypes, and a set of closely related clonotypes was present in 9 patients. The presence of T-cell clones bearing a set of highly homologous TCR-beta molecules in most patients with hemolytic PNH is consistent with an immune process driven by the same (or similar) antigen(s)-probably a nonpeptide antigen, because patients sharing clonotypes do not all share identical HLA alleles. These data confirm that CD8+ CD57+ T cells play a role in PNH pathogenesis and provide strong new support to the hypothesis that the expansion of the GPI(-) blood cell population in PNH is due to selective damage to normal hematopoiesis mediated by an autoimmune attack against a nonpeptide antigen(s) that could be the GPI anchor itself.

CD157 plays a pivotal role in neutrophil transendothelial migration

Paracellular diapedesis, a key step in leukocyte recruitment to the site of inflammation, occurs at endothelial junctions and is regulated by highly coordinated interactions between leukocytes and endothelium. We found that CD157, a glycosylphosphatidylinositol-anchored ectoenzyme belonging to the NADase/ADP-ribosyl cyclase family, plays a crucial role for neutrophil diapedesis, because its ligation with specific monoclonal antibodies (both on neutrophils or endothelial cells) results in altered neutrophil movement on the apical surface of endothelium and, ultimately, in loss of diapedesis. Real-time microscopy revealed that CD157 behaves as a sort of compass during the interaction between neutrophils and endothelial cells; indeed, following CD157 ligation, neutrophils appear disoriented, meandering toward junctions where they eventually stop without transmigrating. These findings are relevant in vivo because CD157-deficient neutrophils obtained from patients with paroxysmal nocturnal hemoglobinuria are characterized by a severely impaired diapedesis.

Polymorphisms in UGT1A gene family and irinotecan toxicity in patients with advanced colorectal cancer

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Background: The irinotecan active metabolite, SN38, is inactivated through glucuronidation mainly by uridine diphosphate glucuronosyltransferase (UGT) 1A1. The (TA)7 allele of a polymorphism in UGT1A1 promoter has been associated with reduced SN38-glucuronidation rate and more severe toxicity. Since other UGT1A family isoforms, the extrahepatic UGT1A7 and the hepatic UGT1A9, are involved in SN38 glucuronidation, it has been suggested that also polymorphic variants of these genes may affect irinotecan toxicity. Methods: 84 patients with advanced colorectal cancer received an irinotecan-based (180 mg/m2 q.2wks) combination treatment. Polymorphisms of UGT1A1 [(TA)6>7], UGT1A7 [387T > G, 391–2CG > AA, 622T > C] and UGT1A9 [-118(T)9>10, -87G > A, 98T > C, I152G > A] were identified by sequencing on DNA from blood samples obtained under an IRB approved protocol. Toxicity has been graded according to NCI-CT criteria. Results: Patient median age was 64 y (range: 31–82); median PS was 0 (range: 0–2). Severe toxicity (diarrhea or/and neutropenia ≥G3) has been observed in 32 patients: diarrhea in 11, neutropenia in 25 (4 patients had both). The estimated allele frequencies were as follows: UGT1A1, (TA)7 (0.35); UGT1A7, 387T and the completely linked 391–2CG (0.39), 622C (0.39); UGT1A9, -118(T)10 (0.39), -87A (0.05), T98C (0.02), I152A (0.21). Severe toxicity was significantly associated only with: (a) the UGT1A1 (TA)7 allele [severe toxicity in 25% of (TA) 6/6, in 46% of (TA) 6/7, in 55% of (TA) 7/7 (Mantel-Haenszel trend test, P < 0.03)]; and (b) the low activity UGT1A7 622C allele [severe toxicity in 26% of 622 T/T, in 39% of 622 T/C, in 67% of 622 C/C (Mantel-Haenszel, P < 0.02)]. In addition, the analysis of the combined genotypes [(TA)6>7 and 622T > C] has shown severe toxicity in 21% of patients with none of (TA)7 and of 622C alleles, in 43% of patients in which the sum of the number of (TA)7 and of 622C alleles is 1 or 2, in 57% of patients in which this sum is ≥3 (the latter includes all patients with both toxicities) (Mantel-Haenszel, P < 0.02). Conclusions: These data show that both the low activity UGT1A1 (TA)7 and UGT1A7 622C alleles are significantly associated with irinotecan severe toxicity. It is to evaluate if their combined genotype may be a better predictor of toxicity.

No significant financial relationships to disclose.

Multiplex tetra-primer amplification refractory mutation system PCR to detect 6 common germline mutations of the MUTYH gene associated with polyposis and colorectal cancer

BACKGROUND

We describe a simple tetra-primer amplification refractory mutation system PCR (T-ARMS-PCR) for detecting MUTYH mutations, which are associated with colorectal adenomas and colorectal cancer.

METHODS

We designed specific T-ARMS-PCR assays for 6 mutations (Y165C, G382D, 1395_7delGGA, Y90X, 1103delC, and R231H) selected on the basis of the frequency of their occurrence. We also designed a set of 3 multiplex T-ARMS PCR assays, each for detection of 2 mutations. We tested DNA samples from patients with attenuated or classic adenomatous polyposis coli and no detectable APC germline mutations.

RESULTS

All mutations were easily detected with both the specific and multiplex T-ARMS-PCR assays. Results were confirmed by DNA HPLC analysis in all 54 patients, and each mutation was confirmed by direct DNA sequencing.

CONCLUSIONS

T-ARMS-PCR does not require any special equipment, and it provides rapid, reproducible, and cost-effective detection of common MUTYH mutations. Multiplex T-ARMS-PCR allows the detection of 6 common MUTYH mutations with use of as few as 3 single tube PCR reactions. It could be useful to carry out large population-based epidemiologic studies.

A quantitative measurement of the human somatic mutation rate

The mutation rate (mu) is a key biological feature of somatic cells that determines risk for malignant transformation, and it has been exceedingly difficult to measure in human cells. For this purpose, a potential sentinel is the X-linked PIG-A gene, because its inactivation causes lack of glycosylphosphatidylinositol-linked membrane proteins. We previously found that the frequency (f) of PIG-A mutant cells can be measured accurately by flow cytometry, even when f is very low. Here we measure both f and mu by culturing B-lymphoblastoid cell lines and first eliminating preexisting PIG-A mutants by flow sorting. After expansion in culture, the frequency of new mutants is determined by flow cytometry using antibodies specific for glycosylphosphatidylinositol-linked proteins (e.g., CD48, CD55, and CD59). The mutation rate is then calculated by the formula mu = f/d, where d is the number of cell divisions occurring in culture. The mean mu in cells from normal donors was 10.6 x 10(-7) mutations per cell division (range 2.4 to 29.6 x 10(-7)). The mean mu was elevated >30-fold in cells from patients with Fanconi anemia (P < 0.0001), and mu varied widely in ataxia-telangiectasia with a mean 4-fold elevation (P = 0.002). In contrast, mu was not significantly different from normal in cells from patients with Nijmegen breakage syndrome. Differences in mu could not be attributed to variations in plating efficiency. The mutation rate in man can now be measured routinely in B-lymphoblastoid cell lines, and it is elevated in cancer predisposition syndromes. This system should be useful in evaluating cancer risk and in the design of preventive strategies.

Patients with paroxysmal nocturnal hemoglobinuria have a high frequency of peripheral-blood T cells expressing activating isoforms of inhibiting superfamily receptors

Patients with paroxysmal nocturnal hemoglobinuria (PNH) have a large clonal population of blood cells deriving from hematopoietic stem cells (HSCs) deficient in glycosylphosphatidylinositol (GPI)-anchored surface molecules. A current model postulates that PNH arises through negative selection against normal HSCs exerted by autoreactive T cells, whereas PNH HSCs escape damage. We have investigated the inhibitory receptor superfamily (IRS) system in 13 patients with PNH. We found a slight increase in the proportion of T cells expressing IRS. In contrast to what applies to healthy donors, the engagement of IRS molecules on T cells from patients with PNH elicited a powerful cytolytic activity in a redirected killing assay, indicating that these IRSs belong to the activating type. This was confirmed by clonal analysis: 50% of IRS+ T-cell clones in patients with PNH were of the activating type, while only 5% were of the activating type in healthy donors. Moreover, the ligation of IRS induces (1) production of tumor necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma) and (2) brisk cytolytic activity against cells bearing appropriate IRS counter-ligands. In addition, these IRS+ T cells show natural killer (NK)-like cytolytic activity to which GPI- cells were less sensitive than GPI+ cells. Thus, T cells with NK-like features, expressing the activating isoforms of IRS, may include effector cells involved in the pathogenesis of PNH.

In vivo gene marking of rhesus macaque long-term repopulating hematopoietic cells using a VSV-G pseudotyped versus amphotropic oncoretroviral vector

BACKGROUND

Gene transfer efficiency into primitive hematopoietic cells may be limited by their expression of surface receptors allowing vector entry. Vectors pseudotyped with the vesicular stomatitis virus (VSV-G) envelope do not need receptors to enter cells, and therefore may provide superior transduction efficiency.

METHODS

Using a competitive repopulation model in the rhesus macaque, we examined in vivo gene marking levels of blood cells transduced with two vectors: (i) a VSV-G pseudotyped retrovirus and (ii) a conventional amphotropic retrovirus. The VSV-G vector, containing the human glucose-6-phosphate dehydrogenase (G6PD) gene, was constructed for treatment of severe hemolytic anemia caused by G6PD deficiency. Three myeloablated animals were transplanted with peripheral blood CD34+ cells, half of which were transduced with the VSV-G vector and the other half with the amphotropic vector.

RESULTS

In all animals post-transplantation, levels of in vivo marking in circulating granulocytes and mononuclear cells were similar: 1% or less with both vectors. In one animal, the human G6PD enzyme transferred by the VSV-G vector was expressed in erythrocytes, early after transplantation, at a level of 45% of the endogenous rhesus G6PD protein.

CONCLUSIONS

In a clinically relevant animal model, we found similar in vivo marking with a VSV-G pseudotyped and a standard amphotropic oncoretroviral vector. Amphotropic receptor expression may not be a limiting factor in transduction efficiency, but VSV-G pseudotypes possess other practical advantages that may make them advantageous for clinical use.

CD157 is an important mediator of neutrophil adhesion and migration

CD157, a glycosylphosphatidylinositol (GPI)-anchored protein encoded by a member of the CD38 NADase/ADP-ribosyl cyclase gene family, is expressed on the surface of most human circulating neutrophils. This work demonstrates that CD157 is a receptor that induces reorganization of the cytoskeleton and significant changes in cell shape, and that signals mediated by CD157 act through modulation of cytosolic Ca(2+) concentration. These signals are independent of the products of CD157's enzymatic activities (ie, cyclic adenosine diphosphate [ADP]-ribose and ADP-ribose). Indeed, the enzymatic activities of CD157 in circulating neutrophils as well as in dimethyl sulfoxide (DMSO)-differentiated (CD157(+)/CD38(-)) HL-60 cells, are hardly detectable. This work also shows that the receptorial activity relies on cross-talk between CD157 and beta(2) integrin. CD157 localizes in GM1-enriched lipid rafts and, upon activation, it migrates to the uropod, a structure specialized in motility and adhesive functions. Indeed, CD157 is involved in adhesion to extracellular matrix proteins and in chemotaxis induced in vitro by formyl-methionyl-leucyl-phenylalanine (fMLP). These findings were consistent with the results obtained in neutrophils from patients with paroxysmal nocturnal hemoglobinuria (PNH), in which CD157 is deficient. These neutrophils showed constant defects in adhesion and migration. Our data attribute specific and crucial roles to CD157 in the regulation of innate immunity during inflammation.

G6PD is indispensable for erythropoiesis after the embryonic-adult hemoglobin switch

Glucose 6-phosphate dehydrogenase (G6PD) (EC 1.1.1.42) is an essential enzyme for the rapid production of NADPH, as required on exposure to oxidative stress. Mouse embryonic stem (ES) cells can produce all embryonic and fetal/adult cell types. By studying the in vitro differentiation of embryoid bodies produced from G6pdDelta ES cells that are totally unable to produce G6PD protein, we found that these cells are able to differentiate into mesodermal cells, cardiomyocytes, hepatocytes, and primitive erythroid cells. However, we show here that, after the hemoglobin switch has taken place, definitive erythrocytes die by apoptosis. This apoptotic death is delayed by reducing agents and by a caspase inhibitor, but it is prevented only by the restoration of G6PD activity. Thus, G6PD proves indispensable for definitive erythropoiesis.

Severe telomere shortening in patients with paroxysmal nocturnal hemoglobinuria affects both GPI- and GPI+ hematopoiesis

A most distinctive feature of paroxysmal nocturnal hemoglobinuria (PNH) is that in each patient glycosylphosphatidylinositol-negative (GPI-) and GPI+ hematopoietic stem cells (HSCs) coexist, and both contribute to hematopoiesis. Telomere size correlates inversely with the cell division history of HSCs. In 10 patients with hemolytic PNH the telomeres in sorted GPI- granulocytes were shorter than in sorted GPI+ granulocytes in 4 cases, comparable in 2 cases, and longer in the remaining 4 cases. Furthermore, the telomeres of both GPI- and GPI+ hematopoietic cells were markedly shortened compared with age-matched controls. The short telomeres in the GPI- cells probably reflect the large number of cell divisions required for the progeny of a single cell to contribute a large proportion of hematopoiesis. The short telomeres of the GPI+ cells indicate that the residual hematopoiesis contributed by these cells is not normal. This epigenetic change is an additional feature shared by PNH and aplastic anemia.