Quantitative real-time reverse-transcription polymerase chain reaction for diagnosis of BCR-ABL positive leukemias and molecular monitoring following allogeneic stem cell transplantation

Myelodysplastic Syndromes Diagnosis: What Is the Role of Molecular Testing?

Diagnosing a myelodysplastic syndrome (MDS) can be challenging. Somatic mutations are common in MDS and might have diagnostic utility in patients with idiopathic cytopenias of undetermined significance (ICUS). However, using mutations to diagnose MDS is complicated by several issues: (1) no gene is mutated in most cases, (2) no mutated gene is highly specific for MDS, (3) clonal hematopoiesis is common in older individuals without disease, and (4) we lack outcome data for ICUS patients with clonal cytopenias of undetermined significance (CCUS). Despite these caveats, genetic sequencing can inform the diagnosis of MDS. CCUS patients more closely resemble patients with MDS than age matched controls with somatic mutations. Genetic testing can identify alternative diagnoses in cytopenic patients and help risk stratify those with proven MDS. While we cannot include somatic mutations in the diagnostic definition of MDS now, testing to recognize CCUS will help characterize outcomes in these diagnostically challenging patients.

Hypothesis: Artifacts, Including Spurious Chimeric RNAs with a Short Homologous Sequence, Caused by Consecutive Reverse Transcriptions and Endogenous Random Primers

Recent RNA-sequencing technology and associated bioinformatics have led to identification of tens of thousands of putative human chimeric RNAs, i.e. RNAs containing sequences from two different genes, most of which are derived from neighboring genes on the same chromosome. In this essay, we redefine "two neighboring genes" as those producing individual transcripts, and point out two known mechanisms for chimeric RNA formation, i.e. transcription from a fusion gene or trans-splicing of two RNAs. By our definition, most putative RNA chimeras derived from canonically-defined neighboring genes may either be technical artifacts or be cis-splicing products of 5'- or 3'-extended RNA of either partner that is redefined herein as an unannotated gene, whereas trans-splicing events are rare in human cells. Therefore, most authentic chimeric RNAs result from fusion genes, about 1,000 of which have been identified hitherto. We propose a hypothesis of "consecutive reverse transcriptions (RTs)", i.e. another RT reaction following the previous one, for how most spurious chimeric RNAs, especially those containing a short homologous sequence, may be generated during RT, especially in RNA-sequencing wherein RNAs are fragmented. We also point out that RNA samples contain numerous RNA and DNA shreds that can serve as endogenous random primers for RT and ensuing polymerase chain reactions (PCR), creating artifacts in RT-PCR.

Validation of chimerism in pediatric recipients of allogeneic hematopoietic stem cell transplantation (HSCT) a comparison between two methods: real-time PCR (qPCR) vs. variable number tandem repeats PCR (VNTR PCR)

Post-hematopoietic stem cell transplantation (HSCT) chimerism monitoring is important to assess relapse and therapeutic intervention. The purpose of our study is to compare two methods variable number tandem repeats (VNTR) vs. quantitative real- time polymerase chain reaction (qPCR) in terms of determining chimerism. 127 (peripheral blood n=112, bone marrow n=15) samples were simultaneously tested by VNTR using APO-B, D1S80, D1S111, D17S30, gene loci SRY and ZP3 and qPCR using 34 assays (CA001-CA034) that are designed to a bi-allelic insertion/deletion (indel) polymorphism in the human genome. Samples were separated in three subsets: total WBC, T-cell and Myeloid cells. Extraction of DNA was performed then quantified. We analyzed column statistics, paired t-test and regression analysis for both methods. There was complete correlation between the two methods. The simplicity and rapidity of the test results from the qPCR method is more efficient and accurate to assess chimerism.

How I treat newly diagnosed chronic phase CML

The progress made in the understanding of chronic myeloid leukemia (CML) since the recognition of a common chromosomal abnormality to the introduction of ever more effective tyrosine kinase inhibitors is unprecedented in cancer. The expected survival for patients diagnosed with CML today, if properly managed, is probably similar to that of the general population. When managing patients with CML the goal is to achieve the best long-term outcome and we should base the treatment decisions on the data available. The results from cytogenetic and molecular analyses have to be interpreted judiciously and all available treatment options integrated into the treatment plan properly. The availability of several treatment options in CML is an asset, but the temptation of rapid succession of treatment changes because of perceived suboptimal response or for adverse events that could be managed needs to be avoided. Any decision to change therapy needs to weigh the expected long-term outcome with the current option versus the true expectations with any new option, particularly as it relates to irreversible outcomes, such as transformation to blast phase and death. In this manuscript, we discuss the treatment approach that has helped us manage successfully a large CML population.

The immune inhibitory receptor osteoactivin is upregulated in monocyte-derived dendritic cells by BCR-ABL tyrosine kinase inhibitors

Multiple approaches presently aim to combine targeted therapies using tyrosine kinase inhibitors with immunotherapy. Ex vivo-generated dendritic cells are frequently used in such strategies due to their unique ability to initiate primary T-cell immune responses. Besides governing tumor cell growth, many kinases targeted by tyrosine kinase inhibitors are involved in the development and function of dendritic cells and thus tyrosine kinase inhibitor therapy may cause immunoinhibitory side effects. We here report that exposure of developing human monocyte-derived dendritic cells to the BCR-ABL inhibitors imatinib, dasatinib, and nilotinib results in profound upregulation of the transmembrane glycoprotein osteoactivin that has recently been characterized as a negative regulator of T-cell activation. Thus, in line with osteoactivin upregulation, exposure to tyrosine kinase inhibitors resulted in significantly reduced stimulatory capacity of dendritic cells in mixed lymphocyte reactions that could be restored by the addition of blocking anti-osteoactivin antibody. Our data demonstrate that tyrosine kinase inhibitor-mediated inhibition of dendritic cell function is, at least in great part, mediated by upregulation of the immune inhibitory molecule osteoactivin.

Proposed algorithm for the best detection of different bcr-abl gene fusion transcripts in molecular diagnostics laboratories: experience of a major referral center

AIMS

Detection of bcr-abl transcripts is important both in diagnosis as well as in prognostication and treatment modalities of different types of leukemia, both chronic and acute. However, the techniques employed are variable and different among laboratories. Our aim was to share with other labs a strategy/algorithm that we find highly useful for implementation to best detect all bcr-abl fusion transcripts for proper patient management.

METHODS

We have used two techniques for the detection of bcr-abl transcripts, an in-house developed polymerase chain reaction and a real-time quantitative commercial polymerase chain reaction (PCR) kit and tested 849 patients referred for initial screening for bcr-abl.

RESULTS

Out of 849 cases, 146 (17.2%) were positive for bcr-abl. Around 92.11% of the total bcr-abl positive cases (N=76) detected by the real-time quantitative technique were also positive by the gel-based PCR assay; however, six cases (around 7.89%) were missed by the real-time assay and detected by the other technique in chronic myelogenous leukemia-proven cases.

CONCLUSION

We highly encourage other laboratories to perform testing using a simple and inexpensive gel-based PCR screening assay followed by a real-time quantitative assay for a baseline bcr-abl expression level. This combination will enable laboratories to detect all the reported fusion transcripts in accordance with the clinical presentation of the patient as well as other laboratory tests for the best use of this genetic test in patient management and care.

Molecular pathology of myeloproliferative neoplasms

Myeloproliferative neoplasms (MPNs; formerly chronic myeloproliferative disorders) are a class of myeloid hematologic malignancies that represent a stem cell-derived expansion of 1 or more hematopoietic cell lineages. The current 2008 World Health Organization system recognizes 8 types of MPN: chronic myelogenous leukemia, chronic neutrophilic leukemia, polycythemia vera, primary myelofibrosis, essential thrombocythemia, chronic eosinophilic leukemia, mastocytosis, and myeloproliferative neoplasm, unclassifiable. This review summarizes the salient characteristics of the MPNs, with emphasis on recent developments in the molecular pathophysiology and therapeutic monitoring of these disorders.

Minimal residual disease diagnostics in myeloid malignancies in the post transplant period

Allogeneic SCT is important in myelodysplastic syndrome, the BCR-ABL-negative chronic myeloproliferative diseases (CMPDs) and in poor-risk AML. Techniques to monitor the minimal residual disease, for example, by PCR or immunophenotyping gain increasing importance in the post transplantation period as basis for improved and earlier therapeutic interventions in impending relapse. Recent markers such as the NPM1 mutations in AML or the JAK2V617F mutation in the CMPD can be exactly quantified by real-time PCR and were evaluated for their prognostic value in the post transplantation phase and for their utility to plan adoptive immunotherapy in case of molecular relapse. With respect to chimerism, new and very sensitive methods were introduced, for example, quantitative assessment of genetic polymorphisms by real-time PCR, but also methods here are still highly individualized. Only in CML, where SCT focuses now on poor-risk cases or cases of tyrosine kinase inhibitor failure, follow-up schedules are standardized. Standardization of the different diagnostic techniques and of the intervals in the post transplantation period is urgently needed also in other myeloid malignancies and should be focus of future studies.

LRP16 is fused to RUNX1 in monocytic leukemia cell line with t(11;21)(q13;q22)

OBJECTIVE

The RUNX1 (also known as AML1) gene is observed frequently as the target of chromosomal rearrangements in human acute leukemia. We describe here a previously unreported rearrangement, t(11;21)(q13;q22), that disrupts the RUNX1 gene in a patient with acute leukemia and the molecular analysis of the fusion gene.

METHODS

We have established a monocytic leukemia cell line, ELAM-1, from a patient with acute leukemia evolving from myelodysplastic syndrome (MDS). Translocation (11;21) (q13;q22) was observed in both patient leukemia cells and ELAM-1.

RESULTS

The split signal of RUNX1 was detected by fluorescence in situ hybridization and indicated the involvement of RUNX1 in ELAM-1. Using 3'- Rapid amplification of cDNA ends and reverse transcription-Polymerase chain reaction analysis, we detected both RUNX1 (exon 5)-LRP16 and RUNX1 (exon 6)-LRP16 transcripts, suggesting that the RUNX1 breakpoint lies in intron 6 and that alternative fusion splice variants are generated. Reciprocal LRP16-RUNX1 fusion was also detected.

CONCLUSIONS

We identified a novel RUNX1 fusion partner, LRP16 on 11q13 involving t(11;21)(q13;q22). Although it was reported that overexpression of LRP16 promotes human breast cancer cell proliferation, the function of LRP16 in leukemia remains to be studied. This fusion gene and cell line may provide a new research tool to investigate the mechanism of leukemogenesis generated by the RUNX1 fusion gene.

Dry-reagent disposable dipstick test for visual screening of seven leukemia-related chromosomal translocations

We report the first dry-reagent, disposable, dipstick test for molecular screening of seven chromosomal translocations associated with acute and chronic leukemia. The dipstick assay offers about 10 times higher detectability than agarose gel electrophoresis and, contrary to electrophoresis, allows confirmation of the sequence of the polymerase chain reaction (PCR) product by hybridization within a few minutes without the need of instrumentation. Biotinylated amplified DNA is hybridized with a dA-tailed probe and applied to the strip, which contains oligo(dT)-conjugated gold nanoparticles in dry form. Upon immersion of the strip in the appropriate buffer, the solution migrates and the hybrids are captured by immobilized streptavidin at the test zone generating a characteristic red line. The excess nanoparticles are captured by oligo(dA) strands immobilized at the control zone of the strip producing a second red line. We studied the: t(9;22)(q34;q11), t(15;17)(q22;q21), t(11;17)(q23;q21), t(5;17)(q32;q21), t(11;17)(q13;q21), t(8,21)(q22;q22) and inv(16)(p13;q22) that generate the BCR-ABL, PML-RARa, PLZF-RARa, NPM-RARa, NuMA-RARa, AML1-ETO and CBFβ-MYH11 fusion genes, respectively. A single K562 cell was detectable amidst 10⁶ normal leukocytes. A dipstick test was developed for actin, as a reference gene. The dipstick assay with appropriate probes can be used for identification of the fusion transcripts involved in the translocation.

beta-Glucuronidase is an optimal normalization control gene for molecular monitoring of chronic myelogenous leukemia

Quantitative monitoring of breakpoint cluster region (BCR)-Abelson kinase (ABL) transcripts has become indispensable in the clinical care of patients with chronic myelogenous leukemia. Because quantity and quality of RNA in clinical samples are highly variable, a suitable internal normalization control is required for accurate BCR-ABL quantification. However, few studies have examined suitability of the control genes using criteria relevant to residual disease testing. In this study, we evaluated a number of control genes with the application of several novel criteria, including control gene performance on serial patient sample testing and in a residual disease model. We also examined expression of the control genes in BCR-ABL-positive K562 cells in response to Gleevec treatment. We found that beta-glucuronidase is the best control gene among those studied. Importantly, ABL, a widely used control gene, generates misleading BCR-ABL changes that potentially affect the clinical management of chronic myelogenous leukemia patients.

Molecular monitoring of chronic myelogenous leukemia: identification of the most suitable internal control gene for real-time quantification of BCR-ABL transcripts

Monitoring breakpoint cluster region-Abelson kinase (BCR-ABL) levels in patients treated for chronic myelogenous leukemia (CML) has become an integral part of patient management. Real-time reverse transcriptase-polymerase chain reaction is the method of choice for this purpose because of its high analytical sensitivity and reproducibility. Given the variation of RNA quality and quantity in clinical specimens, accurate quantitative assessment of BCR-ABL depends on normalization of the BCR-ABL signal to an appropriate internal reference. However, the controls used by different laboratories vary, and there is no clear consensus on an ideal reference due to limited investigations. In this study, we compared nine commonly used control genes for three criteria: mRNA abundance, levels in CML and non-CML cells, and their degradation kinetics in comparison with BCR-ABL. We found that beta-glucuronidase (GUSB) is the most suitable among the nine genes tested. Although ABL is most widely used, our data suggest that the amount of ABL is different in CML and non-CML cells. Moreover, ABL levels are regulated by cellular stress. These findings have a direct impact on current clinical laboratory practice and patient care because the use of a proper control gene affects the reported levels of BCR-ABL transcripts used for patient management decisions.

Validation of the 2-DeltaDeltaCt calculation as an alternate method of data analysis for quantitative PCR of BCR-ABL P210 transcripts

Chronic myelogenous leukemia (CML) is a clonal myeloproliferative disorder that is characterized by the presence of a reciprocal translocation between chromosomes 9 and 22 and results in the formation of the Philadelphia (Ph1) chromosome and is present in most of CML patients. The Ph1 chromosome forms a chimeric gene that encodes an abnormal P210 mRNA transcript in most CML patients. Surveillance for minimal residual disease by detection of BCR/ABL transcripts is currently done mostly by quantitative real-time reverse transcriptase polymerase chain reaction (RT-PCR). Quantitation of BCR/ABL transcripts can monitor tumor load and the outcome of therapy. Absolute quantification determines the input copy number of the transcript of interest, usually by plotting the amount of PCR product onto a standard curve based on serial dilutions of the same product cloned in plasmids. Relative quantification describes the change in expression of the target gene in the patient sample relative to that of a control transcript by using the 2-DeltaDeltaCt calculation. The results of real-time RT-PCR for BCR/ABL transcripts are often analyzed by using plasmid DNA standard curves. In the present study, 79 BCR/ABL transcript-positive samples from CML patients who were being monitored for minimal residual disease by real-time quantitative RT-PCR were studied to determine whether the 2-DeltaDeltaCt approach was equivalent to the plasmid standard curve method. BCR/ABL P210 transcripts were quantitated using both the plasmid standard curve method and the 2-DeltaDeltaCt calculation. The comparison of both methods revealed a highly significant and linear correlation between the plasmid standard curve method and the 2-DeltaDeltaCt calculation (R2=0.98, P<0.0001). Furthermore, there was a reduction of preparation time, contamination risk, and reagent usage. The 2-DeltaDeltaCt calculation is a convenient alternative method to derive accurate quantitative information from real time PCR assays.

Distinct molecular phenotype of malignant CD34(+) hematopoietic stem and progenitor cells in chronic myelogenous leukemia

Chronic myelogenous leukemia (CML) is a malignant disorder of the hematopoietic stem cell characterized by the BCR-ABL oncogene. We examined gene expression profiles of highly enriched CD34(+) hematopoietic stem and progenitor cells from patients with CML in chronic phase using cDNA arrays covering 1.185 genes. Comparing CML CD34(+) cells with normal CD34(+) cells, we found 158 genes which were significantly differentially expressed. Gene expression patterns reflected BCR-ABL-induced functional alterations such as increased cell-cycle and proteasome activity. Detoxification enzymes and DNA repair proteins were downregulated in CML CD34(+) cells, which might contribute to genetic instability. Decreased expression of junction plakoglobulin and CXC chemokine receptor 4 (CXCR-4) might facilitate the release of immature precursors from bone marrow in CML. GATA-2 was upregulated in CML CD34(+) cells, suggesting an increased self-renewal in comparison with normal CD34(+) cells. Moreover, we found upregulation of the proto-oncogene SKI and of receptors for neuromediators such as opioid mu1 receptor, GABA B receptor, adenosine A1 receptor, orexin 1 and 2 receptors and corticotropine-releasing hormone receptor. Treatment of CML progenitor cells with the selective adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) resulted in a dose-dependent significant inhibition of clonogenic growth by 40% at a concentration of 10(-5) M, which could be reversed by the equimolar addition of the receptor agonist 2-chloro-N6-cyclopentyladenosine (P<0.05). The incubation of normal progenitor cells with DPCPX resulted in an inhibition of clonogenic growth to a significantly lesser extent in comparison with CML cells (P<0.05), suggesting that the adenosine A1 receptor is of functional relevance in CML hematopoietic progenitor cells.

Imatinib mesylate in conjunction with allogeneic hematopoietic stem cell transplantation in patients with Philadelphia chromosome positive leukemias: report of 4 cases

We described here four patients diagnosed with Philadelphia chromosome positive (Ph+) leukemia, consisting of chronic myeloid leukemia (CML) (n=2) and Ph+ acute lymphoblastic leukemia (ALL) (n=2). All patients were treated with imatinib mesylate (300-400 mg/day) for the treatment of relapsed CML after allogeneic hematopoietic stem cell transplantation (SCT) (n=2), relapsed Ph+ ALL after SCT (n=1), and Ph+ ALL preceding SCT (n=1). Significant clinical and molecular responses were observed in all patients and three of them achieved sustained molecular remission. Imatinib was well tolerated and did not induce noticeable graft versus host disease although one patient presented severe skin rash (Grade III). Notably, serum cyclosporine A concentration increased after the initiation of imatinib treatment, probably through competitive inhibition of P450 3A4 isoenzyme. Our data suggest that imatinib in conjunction with SCT for the Ph+ leukemia may be a promising treatment strategy.

Peripheral blood progenitor cell collection in chronic myeloid leukemia patients with complete cytogenetic response after treatment with imatinib mesylate

BACKGROUND

Imatinib mesylate (IM) was introduced in chronic myeloid leukemia (CML) treatment in the late 1990s and substantially changed the therapeutic approach to the disease, by inducing complete cytogenetic response (CCR) in approximately 60 percent of cases. Nevertheless, some concerns exist about the duration of response to treatment and the onset of resistance to IM.

STUDY DESIGN AND METHODS

Twenty-five chronic-phase CML patients in stable CCR (>6 months) treated for at least 1 year with IM at the standard dose (400 mg/day) were mobilized with recombinant human granulocyte-colony-stimulating factor (Filgrastim) at 10 microg per kg for 4 to 6 days, with the aim of collecting at least 2 x 10(6) CD34+ cells per kg. Standard cytogenetic analysis and first-round and/or nested polymerase chain reaction were performed in basal and postmobilization samples to examine the presence of bcr-abl transcripts.

RESULTS

CD34+ cells collection was successful in 16 patients, yielding a median of 3.01 x 10(6) +/- 1.09 x 10(6) CD34+ cells per kg at the first attempt, and in 4 of the 9 remaining patients who were remobilized after a temporary withdrawal of IM, yielding a median of 2.65 x 10(6) +/- 0.7 x 10(6) CD34+ cells per kg, with an overall 80 percent success rate. No correlation between mobilization and duration of the disease, length of IM treatment, or previous interferon-alpha and/or hydroxyurea treatment was found.

CONCLUSIONS

Autologous CD34+ cells may be mobilized and collected in most CML patients who achieve CCR after IM treatment, with a view to possible use in the event that resistance to IM occurs in patients not eligible for allogeneic peripheral blood progenitor cell transplantation or those lacking an HLA-matched donor.

Single monochrome real-time RT-PCR assay for identification, quantification, and breakpoint cluster region determination of t(9;22) transcripts

t(9;22) generates the BCR-ABL fusion gene, the hallmark of chronic myeloid leukemia (CML) but also found in acute lymphoblastic leukemia (ALL). Multiple chimeric transcripts translate to proteins of 190 or 210 kd and, rarely, 230 kd. CML typically carries p210 BCR-ABL while ALL is most often associated with p190. Detection and quantification of these fusion transcripts is useful in clinical management. We have exploited the unique melting profiles of these transcripts to design a new, simple, and cost-effective assay based on monochrome multiplex real-time RT-PCR for identification and quantification of each of these transcripts (b3-a2, b2-a2, and e1-a2) without further manipulation. The sensitivity of this assay was 10(-4) for e1-a2 and 10(-5) for b3-a2/b2-a2, which is appropriate for detection of minimal residual disease (MRD). Inter- and intra-assay variation was minimal. We applied this assay to assess the distribution of p190 and p210 in 260 childhood ALL samples from India. BCR-ABL was detected in 19 (7.3%), including one T-ALL. Eight patients (3.1%) demonstrated mBCR-ABL (p190) and 11 (4.2%) had MBCR-ABL (p210). Transcript levels varied markedly (up to 3000-fold) but e1-a2 were generally expressed at higher levels than b3/b2-a2 (P = 0.05). This simple real-time multiplex assay can thus be easily applied to monitor patients with ALL as well as CML.

Characterization of the different BCR-ABL transcripts with a single multiplex RT-PCR

The diagnosis of chronic myeloid leukemia is based on detection of the Philadelphia (Ph) chromosome or the BCR-ABL gene. The junction present in the transcript may vary according to the reciprocal translocation t(9;22)(q34;11). Identification of the transcript (p190, p210 or p230) does not reveal the type of junction but this information is very important for classification of patients in clinical trials. Most identification kits do not explore p230 transcripts and are unable to determine exotic breakpoints. We have developed a clinical molecular diagnosis assay, able to identify all of the BCR-ABL transcripts and, by single assay, to characterize all of the possible transcript junctions. This technique is based on RT-PCR and PCR-capillary electrophoresis. For each patient sample, we performed RT-PCR with three different BCR primers each coupled to a specific different fluorochrome and a unique reverse ABL primer. Depending on the transcript, only one BCR primer was used for each RT-PCR. After capillary electrophoresis and fluorescence determination, we were able to identify both the transcript and its junction at the same time.

LightCyclerR-based quantitative real-time PCR monitoring of patients with follicular lymphoma receiving rituximab in combination with conventional or high-dose cytotoxic chemotherapy

OBJECTIVES

Quantitative real-time polymerase chain reaction (qPCR) is a suitable method to measure residual disease in hematological malignancies. Our objective was to assess a LightCycler-based qPCR for t(14;18)(q32;q21)(IgH/bcl-2)-positive cells quantification in the context of clinical and morphopathological characteristics of patients with follicular lymphoma treated with rituximab (R) in combination with conventional or high-dose chemotherapy.

METHODS

A total of 270 bone marrow (BM) and peripheral blood (PB) samples collected from 52 patients with follicular lymphoma at diagnosis or at relapse before or sequentially during therapy were examined by qPCR and nested-PCR.

RESULTS

A greater amount of t(14;18)-positive cells was observed in BM in comparison with PB in 76% of paired samples. The presence and number of t(14;18)-positive cells in BM and PB correlated with lymphoma activity. Significantly higher numbers of lymphoma cells were found in patients under non-remission compared with patients in clinical remission. During non-remission, 10-fold higher numbers were measured at relapse than at diagnosis. During remission, significantly higher levels were found in partial compared with complete remission. During first-line therapy, R/cyclophosphamide/adriamycin/vincristine/prednisone (CHOP) had higher in vivo purging ability than R/fludarabine/mitoxantrone (FM). After R/high-dose cytosine-arabinoside and mitoxantrone (HAM) or R/carmustine/etoposide/cytarabine/melphalan (BEAM), the level of t(14;18)-positive cells dropped below the detection limit in 80% of patients.

CONCLUSIONS

LightCycler qPCR is a reliable method for quantitative molecular monitoring of t(14;18)-positive cells in BM and PB of patients with follicular lymphoma. It reflects the clinical characteristics of patients and allows assessment of response to different treatment regimens on a molecular level.

BCR-ABL-transduced human cord blood cells produce abnormal populations in immunodeficient mice

In this study, we describe the successful use of a gene transfer approach to demonstrate the ability of forced BCR-ABL expression to deregulate the growth and differentiation of primitive naive human hematopoietic cells after their transplantation into immunodeficient mice. Human CD34+ cord blood cells were exposed to an MSCV retrovirus containing a BCR-ABL-IRES-GFP (P210) cassette and then injected immediately into sublethally irradiated nonobese diabetic-severe combined immunodeficiency (NOD/SCID) or NOD/SCID-beta2microglobulin-/- mice. P210- and control-transduced (GFP+) human hematopoietic cells were produced in the bone marrow of the mice at similar levels until termination of the experiments 5-6 months later. However, the P210-transduced cells produced a markedly different spectrum of progeny, with an increased ratio of myeloid to B-lymphoid cells and a frequently prolonged increase in erythroid and megakaryocytic cells. After 5 months, several of the mice transplanted with P210-transduced cells developed an increased WBC count and/or splenomegaly due to an expansion of the human GFP+ population. These findings demonstrate that forced expression of BCR-ABL in primitive transplantable human hematopoietic cells is sufficient to cause a rapid and persistent deregulation of their growth and differentiation in vivo with occasional evidence after several months of progression to an early stage of disease.

Transplantation of allogeneic CD34+-selected cells followed by early T-cell add-backs: favorable results in acute and chronic myeloid leukemia

BACKGROUND

The aim of this study was to investigate preservation of anti-leukemic activity and protection from opportunistic infections after transplantation of allogeneic + cells in patients with hematologic malignancies and bad prognosis. Methods Thirty-three patients [median age 42 years, range 23-55 years, diagnosis AML/myelodysplastic syndrome (MDS) 14, ALL nine, CML seven and multiple myeloma (MM) three] received myeloablative conditioning followed by infusion of selected CD34+ cells from matched unrelated donors (31) or HLA-identical siblings (two). Early donor lymphocyte infusions (DLI; 0.5 and 1.0 x 10(6) CD3+ cells/kg) were given while patients were on immunosuppressive therapy.

RESULTS

Ninety-seven per cent of patients engrafted and 24 of 29 patients surviving more than 30 days received at least one pre-emptive DLI. Three patients (10%) developed acute (a)GvHD (two grade I-II, one grade III-IV) spontaneously, and 16 patients (67%) developed aGvHD after DLI (12 grade I-II, four grade III-IV). Eight of 24 evaluable patients developed chronic (c)GvHD (33%, six limited, two extensive). After a median follow-up of 590 days (range 138-1610 days) 18 patients were alive (55%), 16 in complete remission (CR), one in hematologic and one in molecular relapse. Seven patients died after relapse (21%) and eight died from transplantation-related causes (24%). Patients with myeloid malignancies had a significantly better survival than patients with ALL or MM (74%+/-10 vs. 30%+/-13, P<0.05).

DISCUSSION

Early pre-emptive low-dose DLI following transplantation of selected CD34+ cells from unrelated donors after myeloablative conditioning is feasible and effective without undue toxicity, especially in patients with myeloid malignancies.

Retrospective comparison of qualitative and quantitative reverse transcriptase polymerase chain reaction in diagnosing and monitoring the ALL1-AF4 fusion transcript in patients with acute lymphoblastic leukaemia

We compared quantitative reverse transcriptase polymerase chain reaction (Q-RT-PCR) to qualitative RT-PCR in determining response to therapy and predicting clinical outcome in 18 retrospectively selected patients with ALL positive for the ALL1-AF4 fusion and with frozen RNA samples collected at diagnosis and during follow-up (96 samples analysed). The ALL1-AF4 junction was detected by qualitative RT-PCR in 18 patients and by Q-RT-PCR in 17 patients (one patient harboured the rare e10-e6 ALL1-AF4 junction, which falls outside of the primer and probe location designed for the Q-RT-PCR). In three of the 12 patients negative to qualitative RT-PCR after induction therapy, a small number of ALL1-AF4 copies was detected by Q-RT-PCR. Thus nine patients were negative and eight positive. Seven of the eight positive patients suffered a relapse, including two of the three patients positive to Q-RT-PCR yet negative to qualitative RT-PCR. Moreover, we found two (5%) discordant results among the 39 follow-up tests of the nine patients who converted to a negative qualitative-quantitative PCR status. The results suggest that qualitative RT-PCR is more appropriate for the routine diagnosis of this genetic alteration. However, Q-RT-PCR is more accurate in assessing the molecular response after induction treatment and could be more useful in clinical decision-making in ALL1-AF4-positive ALL patients.

Advances in the pathogenesis, diagnosis, and treatment of thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) and the hemolytic uremic syndrome (HUS) are both characterized by thrombocytopenia, microangiopathic hemolysis, and organ dysfunction. Other disorders occasionally present with similar manifestations. Recent studies have demonstrated that deficiency in the von Willebrand factor cleaving protease ADAMTS13, due to genetic mutations or autoimmune inhibitors, causes TTP. Molecular cloning of ADAMTS13 elucidates the structure of the protease, raising the prospect for advances in diagnosis and treatment of the disease. Assay of ADAMTS13 activity distinguishes TTP from HUS and other types of thrombotic microangiopathy (TMA); therefore, the term TTP/HUS should be avoided because it obscures the known or potential differences among the various types of TMA.