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The recent World Health Organization classification recognizes different subtypes of acute myeloid leukemia (AML) according to the presence of several recurrent genetic abnormalities. Detection of these abnormalities and other molecular changes is of increasing interest because it contributes to a refined diagnosis and prognostic assessment in AML and enables monitoring of minimal residual disease. These genetic abnormalities can be detected using single RT-PCR, although the screening is still labor intensive and costly. We have developed a novel real-time RT-PCR assay to simultaneously detect 15 AML-associated rearrangements that is a simple and easily applicable method for use in clinical diagnostic laboratories. This method showed 100% specificity and sensitivity (95% confidence interval, 91% to 100% and 92% to 100%, respectively). The procedure was validated in a series of 105 patients with AML. The method confirmed all translocations detected using standard cytogenetics and fluorescence in situ hybridization and some additional undetected rearrangements. Two patients demonstrated two molecular rearrangements simultaneously, with BCR-ABL1 implicated in both, in addition to RUNX1-MECOM in one patient and PML-RARA in another. In conclusion, this novel real-time RT-PCR assay for simultaneous detection of multiple AML-associated fusion genes is a versatile and sensitive method for reliable screening of recurrent rearrangements in AML., (Copyright © 2013 American Society for Investigative Pathology and the Association for Molecular Pathology. Published by Elsevier Inc. All rights reserved.)

We identified two patients with atypical PML-RAR(alpha) rearrangements, 53 and 13 base pairs longer than the typical bcr1 transcript. Sequence analysis revealed a new PML breakpoint at the end of exon 7a in patient 1, and a PML exon 6 breakpoint in patient 2, with an insertion of 35 nucleotides of RAR(alpha) intron 2. Patient 1 did not express RAR(alpha)-PML and patient 2 showed the RAR(alpha)-PML transcript, which corresponded to the typical bcr1. These results emphasize on the relevance of the correct identification of atypical PML-RAR(alpha) rearrangements because of the potential implications in leukemogenesis, in the response to treatment, and for the correct monitoring of minimal residual disease.

Background and Objectives: We report a new real-time reverse transcription polymerase chain reaction (RT-PCR) method for quantification of TEL-AML1 transcripts. The method is based on hybridization probe (HybProbe) chemistry applied in LightCycler equipment. The study group comprised 44 successive cases of pediatric acute lymphoblastic leukemia (P-ALL)., Design and Methods: The quantitative estimation of TEL-AML1 transcripts was performed in 10 P-ALL TEL-AML1-positive patients. The PCR was performed in capillary tubes in 10 microL final volumes using two sets of primers: M1, which detects the long (L-form) and short (S-form) transcripts, and M2, specific for the L-form. The fluorescently labeled HybProbes (TEL 3FL and TEL 5LC) hybridize to the TEL region. TEL-AML1 expression was normalized relative to the levels of AML1 transcripts. Standard curves were prepared using serial dilutions of plasmids with TEL-AML1 or AML1 inserts., Results: The sensitivity attained allowed the detection of TEL-AML1 transcripts at a 10-4 dilution of a cDNA sample from a patient at diagnosis. The within-assay coefficient of variation (CV) for TEL-AML1 was 7.0% and the between-assay CV was 13%. Levels of TEL-AML1 transcript and the TEL-AML1/AML1 ratio decreased by more than four log units (p <0.001) during or after the course of initial treatment. Most of the patients who achieved complete remission after 5-6 months of initial treatment were TEL-AML1 negative, although some positive samples with negligible amounts of TEL-AML1 transcripts were still detected., Interpretation and Conclusions: This method has the sensitivity and reliability required to monitor the presence of minimal residual disease, and could be a powerful tool in monitoring the efficacy of the response to chemotherapy.

The persistence of the AML1-ETO rearrangement performed by reverse transcription polymerase chain reaction (RT-PCR) has been reported in acute myeloid leukemia (AML) patients in long-term complete remission (CR). This persistence, which is not associated with hematological relapse, limits the clinical use of qualitative RT-PCR. Here, we present a new quantitative real-time PCR method to detect AML1-ETO rearrangement using fluorescently labeled probes. Quantitative detection of AML1-ETO was performed in capillary tubes using two fluorescently labeled probes in the LightCycler equipment. The reliability of the method was checked in twenty-two bone marrow samples and one apheresis sample from eight patients with t(8;21) collected at diagnosis and during follow-up assessment. The regression coefficients obtained for standard curves of AML1-ETO and AML were all greater than 0.98. The sensitivity attained allowed the detection of rearrangements at a dilution of 10(-5) Kasumi-1 cDNA. The intra-assay coefficient of variation was 4% for AML1-ETO, and 7% for AML. The inter-assay coefficient of variation was 19% for AML1-ETO and 12% for AML. A log reduction from two to four in the AML1-ETO/AML ratio was evident after CR. The study of the method and first results obtained in patient samples support that quantitative real-time PCR with hybridization probes is a new reliable and sensitive method to monitor minimal residual disease in AML patients. Moreover, the fluorescent probes with the Light-Cycler technology offer the advantage of a rapid detection.

Of 167 newly diagnosed acute promyelocytic leukaemia patients, 83 patients were long (L)-form (50%), eight variable (V)-form (5%) and 76 short (S)-form (45%). The V-form and S-form groups presented a significantly higher percentage of patients with white blood cell counts > 10 x 10(9)/l (P < 0.05). The S-form cases displayed a significantly higher number of cases with M3v microgranular features (P = 0.005) and CD34 expression (P < 0.0001). There were no differences between the three isoforms in complete remission (CR) rate (overall CR 90%), but the 3-year disease-free survival was lower for V-form cases than it was for L- and S-form cases (62% vs. 94% and 89%, P = 0.056). We conclude that the V-form and S-form types are associated with some negative prognostic features at diagnosis. However, our data were only able to demonstrate an association with adverse prognosis in the V-form type and, moreover, as the number of cases was limited, needs to be confirmed in large, uniformly treated series.

Background and Objectives: The detection of PML-RAR by reverse transcription (RT) polymerase chain reaction (PCR) in acute promyelocytic leukemia (APL) patients who are in hematologic remission influences therapeutic decision making in several trials. In the light of this, the Spanish group has recently designed an external quality assessment program (EQAP) of RT-PCR detection of PML-RAR, which includes a study of sensitivity of the participating laboratories., Design and Methods: Eighteen laboratories were involved in the program. Ten laboratories followed the method of Biondi et al., 5 employed that of Borrow et al. and the 3 remaining used other protocols. The sensitivity was studied in five rounds of quality control. The first two shipments consisted of dilutions of NB4 RNA into non-APL RNA. The third round consisted of serial dilutions of the NB4 cell line into HL60 cells. The fourth and five rounds consisted of plasmid dilutions containing the bcr1 and bcr3 PML-RAR isoforms., Results: The results showed that the distinct methods allow detection of the PML-RAR hybrid up to a dilution of 10(-4), and exceptionally, up to 10(-5). The laboratories following the method of Biondi et al. usually detected the 10(-3) dilution and less frequently the 10(-4) one, whereas those using other methods usually detected PML-RAR transcript in the 10(-4) dilution, and less commonly in the 10(-5) dilution. However, each of the PCR methods used by EQAP participating laboratories successfully detected at least 50 copies of PML-RAR alpha fusion transcript in plasmid dilution controls., Interpretation and Conclusions: The results point to heterogeneous sensitivity amongst participating laboratories. This may reflect differences in methodology, although variations in sample quality may also account for discrepant findings.

Background and Objectives: The detection of CBFbeta/MYH11 transcripts by RT-PCR has became a valuable and widely used technique in the accurate cytogenetic and molecular classification of acute myeloid leukemia (AML), but the clinical value of RT-PCR for monitoring minimal residual disease (MRD) during follow-up remains unclear., Design and Methods: We analyzed the factors predicting relapse and the value of MRD monitoring by RT-PCR in a series of 16 patients with CBFb/MYH11-positive AML (15 M4Eo; 1 M4). Fifteen were newly diagnosed cases (CR1) and one was studied after first relapse (CR2). Eight patients had clinical relapse at 6 to 19 months from the achievement of CR., Results: Presenting WBC count had a significant prognostic influence on disease-free survival (p=0.001). All four patients with a WBC count >100x10(9)/L relapsed, while only four additional relapses occurred among the eleven patients who had an initial WBC count below 100x10(9)/L. With regards to molecular monitoring, all relapses but one occurred in patients who showed persistent RT-PCR positivity during hematologic remission. By contrast, conversion to a repeatedly PCR-negative status was observed in the seven patients who remained in CR1 after a median follow-up of 48 months (range 31-79 months), as well as in the transplanted patient who was monitored in CR2. In these patients a PCR-positivity could be detected up to 24 months after diagnosis (median time to conversion to PCR-negative: 8 months)., Interpretation and Conclusions: In conclusion, marked hyperleukocytosis (>100x10(9)/L) confers poor prognosis to the patient with CBFbeta/MYH11-positive AML. In addition, slow kinetics of molecular remission was observed in this subset of AML, but the CBFb/MYH11 fusion transcript is no longer detectable in long-term survivors, indicating that molecular remission is an important therapeutic goal.

Background: Molecular assay commonly used to detect the PML/RAR alpha rearrangement in acute promyelocytic leukemia (APL) has the limited sensitivity in comparison with the higher sensitivity of RAR alpha/PML detection. This prompted us to perform both assays in parallel to monitor a group of APL., Patients and Methods: The study included 56 APL patients mainly treated according with the PETHEMA LPA-96 protocol. The PML/RAR alpha was detected according with Biondi's et al method and the RAR alpha/PML following the Grimwade's et al RT-PCR method (Human Press Inc.)., Results: RAR alpha/PML rearrangement was detected in 90% (20/22) of the patients at diagnosis positives for PML/RAR alpha. RAR alpha/PML was detected in 74% (14/19) of post-induction samples versus 37% (7/19) of positives for PML/RAR alpha. Likewise RAR alpha/PML rearrangement was detected in some post-consolidation samples (2/11) that all were PMI/RAR alpha negatives. In patients in maintenance regimen a greater proportion of RAR alpha/PML positives (6/28) versus PML/RAR alpha (2/28) were observed. In a patient in complete remission RAR alpha/PML preceded the positivity of PML/RAR alpha and persisted after PMI/RAR alpha negativization. The results of the patients monitored since the diagnosis showed that RAR alpha/PML revert to negative one month after PML/RAR alpha negativization., Conclusions: RAR alpha/PML rearrangement is not expressed in the totality of the APL patients, but in only a 90% of them. RAR alpha/PML rearrangement was detected in a greater proportion of samples than PML/RAR alpha. RAR alpha/PML rearrangement lasted longer than PML/RAR alpha after treatment.

The Spanish PETHEMA group designed a protocol for newly diagnosed PML/RARalpha-positive acute promyelocytic leukemia (APL) in which induction and consolidation followed the original AIDA regimen, except for the omission of cytarabine and etoposide from consolidation. Induction consisted of 45 mg/m(2) all-trans retinoic acid (ATRA) daily until complete remission (CR) and 12 mg/m(2) idarubicin on days 2, 4, 6, and 8. Patients in CR received 3 monthly chemotherapy courses: idarubicin 5 mg/m(2)/d x 4 (course no. 1), mitoxantrone 10 mg/m(2)/d x 5 (course no. 2), and idarubicin 12 mg/m(2)/d x 1 (course no. 3). Maintenance therapy consisted of 90 mg/m(2)/d mercaptopurine orally, 15 mg/m(2)/wk methotrexate intramuscularly, and, intermittently, 45 mg/m(2)/d ATRA for 15 days every 3 months. Between November 1996 and December 1998, 123 patients with newly diagnosed PML/RARalpha-positive APL from 39 centers were enrolled. A total of 109 patients achieved CR (89%; 95% confidence interval [CI], 83 to 95), 12 died of early complications, and the remaining 2 were resistant. Consolidation treatment was associated with very low toxicity and no deaths in remission were recorded. Molecular assessment of response by reverse transcriptase-polymerase chain reaction (RT-PCR) showed conversion to PCR-negative in 48 of 99 (51%) and 82 of 88 patients (93%) after induction and consolidation, respectively. The 2-year Kaplan-Meier estimates of overall survival and event-free survival were 82% +/- 4% and 79% +/- 4%, respectively. For patients who achieved CR, the 2-year disease-free survival (DFS) was 92% +/- 3%. These data indicate that a significant reduction in toxicity might be obtained in APL using a less intensive consolidation without apparently compromising the antileukemic effect. These results also suggest a minor role for cytarabine and etoposide in the treatment of newly diagnosed PML/RARalpha-positive APL patients.

To standardize the results obtained in PML/RAR alpha RT-PCR detection by laboratories of hospitals involved in the Spanish Program for Treatment of Hematological Malignancies (PETHEMA) LPA-96, designed for the treatment of acute promyelocytic leukemia (APL), cDNA samples obtained by reverse transcription of RNA from bone marrow samples of patients with APL were sent to participating laboratories. During the first year of this external quality assessment trial nine samples were tested by a maximum of 12 laboratories. The control gene was satisfactorily amplified in 90% of the samples (62 of 69 samples), supporting the adequacy of the cDNA to be used as control sample. There was an 83% concordance between laboratories for PML/RAR alpha detection with similar results for the type of PML/RR alpha rearrangements. However, 17% disagreement still remained, attributable to low sensitivity or inadequacy of methods followed. The results stressed the need for implementation of an external quality assessment scheme to ensure the standardization of the results.

Aims: This study describes a molecular method of reverse transcription polymerase chain reaction (RT-PCR) to detect the rearrangement PML/RAR alpha in acute promyelocytic leukaemia (APL) in order to assess its specificity and sensibility, and to evaluate its utility in the characterization of APL patients., Patients and Methods: Between January and June of 1995, 64 samples of bone marrow and peripheral blood stem cells (PBSC) cytapheresis were studied. There were 58 APL samples (23 patients: 10 samples obtained with disease activity, 43 samples in complete remission (CR) and 5 PBSC samples) and 6 control samples, of non-APL hematological neoplasms (3 other AML, 1 CML, 1 ALL, and 1 MDS). On the RNA obtained from the isolated mononuclear cells of each sample a conserved region of the PML/RAR alpha fusion gene was amplified by using a RT-PCR with specific primers., Results: The sensitivity assays were performed by diluting PML/RAR alpha positive RNA samples into RNA of controls. The RT-PCR assay was capable to detect the PML/RAR alpha until an 1/1000 dilution in negative control RNA. Nine out of 58 APL samples failed in the amplification of the control gene, and were considered non-evaluable. None of the 6 control samples showed PML/RAR alpha rearrangement. Nine out of 10 APL samples with disease activity were positive for the presence of PML/RAR alpha (the non-positive sample was a non-evaluable one). Six out of 43 APL samples in CR showed the rearrangement, 3 of them corresponding to 2 patients who posteriory relapsed 12 and 19 months after 1st CR. The other 3 positive samples came from other 3 APL patients (24 months in 3rd CR, 14 months in 1st CR and early CR), who remained in CR at the end of the study. No relapse could be noted in patients with negative PCR samples. PML/RAR alpha was not found in any of the 5 APL PBSC samples studied., Conclusions: The RT-PCR method described here seems to be highly specific as it only detects this rearrangement in LPA patients. Furthermore, the presence of PML/RAR alpha in CR patients could be related to relapse. For all these reasons, this molecular method shows great usefulness and can be advocated, not only for assessing diagnosis, but for as monitoring minimal residual disease in the post remission follow up.