Chronic myelogenous leukemia: laboratory diagnosis and monitoring

Integrated Chemical Characterization, Network Pharmacology and Transcriptomics to Explore the Mechanism of Sesquiterpenoids Isolated from Gynura divaricata (L.) DC. against Chronic Myelogenous Leukemia

Chronic myelogenous leukemia (CML) is a serious threat to human health, while drugs for CML are limited. Herbal medicines with structural diversity, low toxicity and low drug resistance are always the most important source for drug discoveries. Gynura divaricata (L.) DC. is a well-known herbal medicine whose non-alkaline ingredients (GD-NAIs) were isolated. The GD-NAIs demonstrated potential anti-CML activity in our preliminary screening tests. However, the chemical components and underlying mechanism are still unknown. In this study, GD-NAIs were tentatively characterized using UHPLC-HRMS combined with molecular networking, which were composed of 75 sesquiterpenoids. Then, the anti-CML activities of GD-NAIs were evaluated and demonstrated significant suppression of proliferation and promotion of apoptosis in K562 cells. Furthermore, the mechanism of GD-NAIs against CML were elucidated using network pharmacology combined with RNA sequencing. Four sesquiterpenoids would be the main active ingredients of GD-NAIs against CML, which could regulate PD-L1 expression and the PD-1 checkpoint pathway in cancer, PI3K/AKT, JAK/STAT, TGF-β, estrogen, Notch and Wnt signaling pathways. In conclusion, our study reveals the composition of GD-NAIs, confirms its anti-CML activity and elucidates their underlying mechanism, which is a potential countermeasure for the treatment of CML.

Chronic myeloid leukemia-from the Philadelphia chromosome to specific target drugs: A literature review

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm and was the first neoplastic disease associated with a well-defined genotypic anomaly - the presence of the Philadelphia chromosome. The advances in cytogenetic and molecular assays are of great importance to the diagnosis, prognosis, treatment, and monitoring of CML. The discovery of the breakpoint cluster region (BCR)-Abelson murine leukemia (ABL) 1 fusion oncogene has revolutionized the treatment of CML patients by allowing the development of targeted drugs that inhibit the tyrosine kinase activity of the BCR-ABL oncoprotein. Tyrosine kinase inhibitors (known as TKIs) are the standard therapy for CML and greatly increase the survival rates, despite adverse effects and the odds of residual disease after discontinuation of treatment. As therapeutic alternatives, the subsequent TKIs lead to faster and deeper molecular remissions; however, with the emergence of resistance to these drugs, immunotherapy appears as an alternative, which may have a cure potential in these patients. Against this background, this article aims at providing an overview on CML clinical management and a summary on the main targeted drugs available in that context.

MYC-driven aggressive B-cell lymphomas: biology, entity, differential diagnosis and clinical management

MYC, a potent oncogene located at chromosome locus 8q24.21, was identified initially by its involvement in Burkitt lymphoma with t(8;14)(q24;q32). MYC encodes a helix-loop-helix transcription factor that accentuates many cellular functions including proliferation, growth and apoptosis. MYC alterations also have been identified in other mature B-cell neoplasms and are associated with aggressive clinical behavior. There are several regulatory factors and dysregulated signaling that lead to MYC up-regulation in B-cell lymphomas. One typical example is the failure of physiological repressors such as Bcl6 or BLIMP1 to suppress MYC over-expression. In addition, MYC alterations are often developed concurrently with other genetic alterations that counteract the proapoptotic function of MYC. In this review, we discuss the physiologic function of MYC and the role that MYC likely plays in the pathogenesis of B-cell lymphomas. We also summarize the role MYC plays in the diagnosis, prognostication and various strategies to detect MYC rearrangement and expression.

Chronic myeloid leukemia: Relevance of cytogenetic and molecular assays

Chronic myeloid leukemia (CML) is the prototype cytogenetic malignancy. Even before the development of basic G- and R-banding techniques, CML was found to be associated with a persistent chromosomal abnormality, the Philadelphia (Ph) chromosome. Banding technology later showed the marker chromosome to be a translocation between the breakpoint cluster region (BCR) on chromosome 22q11.2 and the Abelson proto-oncogene (ABL) on chromosome 9q34. Further advances in cytogenetic and molecular biology have also contributed to the understanding, diagnosis, and treatment of CML. Fluorescent in situ hybridization (FISH) has revealed cryptic translocations in most cases of Ph-negative CML. Additional rare chromosomal variant translocations have been discovered as well. The understanding of cytogenetic and molecular physiopathology of CML has led to the use of tyrosine kinase inhibitors as treatment for this disease with spectacular success. Over the 40 years since being identified as the first cytogenetic disease, CML has become the greatest success in translating the basic science of oncology into the treatment of patients with cancer. In this review we will not only summarize the biology of CML, recent progress in the delineation of mechanisms and treatment strategies, but also we will discuss the laboratory tools used for diagnosing CML, for monitoring during treatment and for revealing point mutations and additional chromosomal abnormalities. In doing so, we will describe in detail our individual research on CML, identifying why and how these tests were performed to help to explain CML subgroups and clinical significance of additional chromosomal abnormalities.

Evaluation of a novel multiplex RT-qPCR assay for the quantification of leukemia-associated BCR-ABL1 translocation

Although monitoring of BCR-ABL1 translocation has become an established practice in the management of chronic myeloid leukemia (CML), the detection limit of the BCR-ABL1 transcripts needs more standardization. The aim of the present study was to evaluate the clinical performances of a novel assay for the quantification of BCR-ABL1 fusion transcripts (e13a2 and e14a2) and ABL1 in a single reaction. This assay is based on the real-time reverse transcription polymerase chain reaction (RT-qPCR) in multiplex format. In a retrospective comparative clinical study performed in a reference laboratory, RNA was extracted from 48 CML patient blood samples with various BCR-ABL1/ABL1 ratios and RT-qPCR was performed using either MAScIR assay or the RT-qPCR simplex reference assay used in routine clinical testing. The comparative clinical results showed high qualitative and quantitative concordance (correlation coefficient >0.95) between MAScIR and the reference assays. The present study illustrates the utility of MAScIR assay as a sensitive, rapid, and cost-effective quantitative device to monitor the BCR-ABL1 ratios by RT-qPCR on whole blood of diagnosed Philadelphia chromosome-positive (Ph+) leukemia patients. This test could be used as an aid in the assessment of molecular response to available treatments.

Molecular monitoring of chronic myeloid leukemia: international standardization of BCR-ABL1 quantitation

The BCR-ABL1 translocation is a hallmark of chronic myeloid leukemia. Because patients treated with imatinib and other tyrosine kinase inhibitors achieve lower levels of detectable disease, quantitation of BCR-ABL1 transcripts with quantitative RT-PCR has become an essential tool in chronic myeloid leukemia monitoring. The prognostic significance of molecular responses was recently established by large-scale clinical trials. Achieving defined levels of BCR-ABL1 on the International Scale within specific time frames is an important measure for assessing patient response and probability for relapse and progression. However, extensive variation in quantitative RT-PCR procedures and reporting makes it difficult to interpret these results. More important, lack of standardization, particularly in the United States, prevents the comparison of individual patient results to the data from the clinical trials, which thereby prohibits the meaningful use of such results in the direction of patient care. In this article, we will present an overview of the clinical trial discoveries that drive the need for standardization, review the most updated monitoring guidelines by the National Comprehensive Cancer Network, and highlight recommendations for laboratory practice regarding internal controls and reference materials. Finally, we will provide an update on the recent efforts in the standardization of quantitative RT-PCR reporting using the International Scale.

Acquired mutation of the tyrosine kinase JAK2V617F in Egyptian patients with myeloid disorders

Janus Kinase 2 (JAK2) is a member of a family of four Janus Kinases, 2, and 3 and tyrosine kinase 2. Mutated JAK2 (V617F) has the ability to activate downstream signal transducer and activator of transcription (STAT)-mediated transcription in the absence of the ligand erythropoietin. The autoinhibitory activity of JAK2 is disrupted by the presence of the V617F mutation. Somatic mutation in JAK2 (V617F) gene has been reported in myeloid disorders. This study reports the prevalence of JAK2V617F using amplification refractory mutation system (ARMS)-polymerase chain reaction in 246 Egyptian patients with different myeloid disorders and studied the relationship between the JAK2V617F mutation and parameters in peripheral blood. The mutation was detected among 88 patients (35.8%) with different myeloid disorders. JAK2V617F was found among 81.4% of polycythemia vera (PV), 50% of essential thrombocythemia, 46.1% of primary myelofibrosis (PMF), 33.3% of philadelphia (Ph)-negative chronic myeloid leukemia, 33.3% of myelodysplastic syndrome (MDS)/myeloproliferative neoplasm (MPN), and 50% of refractory anemia with ringed sideroblasts associated with marked thrombocytosis (RARS-T) patients. Hemoglobin and white blood cells were significantly higher in the mutated group of MPN including PV, essential thrombocythemia, and PMF, whereas platelet counts were higher among the mutated PV, PMF, RARS-T, and MDS/MPN group. The identification of JAK2V617F mutations has raised the prospect of developing specific JAK2V617F inhibitors to treat mutated patients.

Persistence of derivative chromosome 22 after achieving a major molecular response in chronic myeloid leukemia with a cryptic BCR-ABL1 fusion gene

We herein report the findings of a 47-year-old Japanese female with chronic myeloid leukemia (CML) with a cryptic BCR-ABL1 transcript on chromosome 9 and a derivative chromosome 22 unrelated to BCR-ABL1. Although she achieved and continued to demonstrate a major molecular response to imatinib treatment following interferon-alpha, there was persistence of a derivative chromosome 22. A detailed chromosome/molecular studies, including serial karyotyping analysis, finally resulted in the karyotyping at the disease onset to be 47,XX,+del(22)(q11.2), with two genetic evens, namely a cryptic BCR-ABL1 transcript on chromosome 9 and derivative chromosome 22 unrelated to BCR-ABL1. This CML case with these two rare genetic events thus raises diagnostic issues such as the difficulty in making a concise evaluation of the chromosomal/molecular events and an accurate disease prognosis, as well as the difficulty in determining the disease remission status after treatment.

Comparison of the cytogenetic and molecular analyses in the assessment of imatinib response in chronic myelocytic leukemia

We aimed to compare the cytogenetic and molecular analyses in the assessment of imatinib mesylate response in patients suffering the chronic phase of chronic myelocytic leukemia who were refractory to alpha-interferon treatment. A total of 117 patients in the chronic phase of chronic myelocytic leukemia were included. The patients were treated with 400 mg/day imatinib mesylate. Bone marrow samples were obtained for the cytogenetic and molecular analyses. Patients without the Ph chromosome were defined as complete cytogenetic responders. Partial cytogenetic response was determined when the Ph chromosome was detected in 1-35% of the cells. Molecular response was determined by quantitative real-time reverse transcriptase polymerase chain reaction (QR-PCR) and defined as no detection of BCR-ABL mRNA. The frequencies of complete and partial cytogenetic response were 29% (n = 34) and 15% (n = 18), respectively. No cytogenetic response was achieved in 56% (n = 65) of the patients. Molecular response was achieved in 62% (n = 21) and 33% (n = 6) of the complete and partial cytogenetic responders, respectively. All of the 65 patients with no cytogenetic response were also molecular nonresponders. We conclude that there is reasonable agreement between the cytogenetic and molecular analyses. Both methods are complementary in the assessment of response to therapy.

Molecular cytogenetic characterization of variant Philadelphia translocations in chronic myeloid leukemia: genesis and deletion of derivative chromosome 9

The mechanisms for the formation of variant Philadelphia (Ph) translocations that occur in 5-10% of patients with chronic myeloid leukemia (CML) are not fully characterized. Studies on the prognosis of these variant translocations have yielded conflicting results, especially regarding imatinib outcome and the status of deletions on the derivative chromosome 9. To shed light on these controversial subjects, we sought to analyze all variant translocation cases presented at diagnosis and identified in our institution between the years 2001 and 2008. Of 336 CML patients who presented at diagnosis and were studied by conventional cytogenetics and fluorescence in situ hybridization (FISH), 25 patients (7.44%) exhibited variant Ph-rearrangements. All chromosomes could be implicated in variant Ph rearrangements, with 32 breakpoints defined. Their distribution was located preferentially in the CG-richest regions of the genome. Deletions on der(9) were observed in 15 of the 25 cases (60%), a greater proportion in typical Ph translocations (12-15%). Both one- and two-step mechanisms were encountered in our series, as well as multiple-step mechanisms, which originate more complex rearrangements. Higher prevalence was observed for the two-step mechanism (56%). Proper assessment of the prognostic significance of variant translocations requires better categorization of these translocations based on their mechanisms of genesis and 9q34 deletion status.

Rapid detection of BCR-ABL fusion genes using a novel combined LUX primer, in-cell RT-PCR and flow cytometric method

Currently, quantitative and semiquantitative assays for minimal residual disease detection include fluorescence in situ hybridisation, multiparameter flow cytometric immunophenotyping and real-time quantitative polymerase chain reaction (RQ-PCR). We have developed a new approach to detect hybrid breakpoint cluster region and Abelson proto-oncogene (BCR-ABL) transcripts inside suspension cells using in situ RT-PCR and light upon extension (LUX) primer, followed by rapid quantitative analysis with flow cytometry. After cellular permeabilization and fixation of single cell suspension, the neoplastic mRNA was reverse transcribed and amplified by PCR with LUX primer. The results demonstrated that a strong positive yellow-green signal was observed in 99-100% cells of K562 cell line, only the red nucleus was detected in NB4 cell line and normal controls. The technique has been utilised to study 12 patients with chronic myeloid leukemia, and the results were compared with those of BCR-ABL fusion mRNA by RT-PCR and BCR-ABL fusion gene of the interphase cells by fluorescence in situ hybridization (FISH). In the five diagnosed patients, 90-98% cells were strongly positive. Four patients, including three patients treated with interferon-alpha and hydroxyurea and one patient treated with imatinib mesylate, had 26-82.5% positive cells. Three patients treated with imatinib mesylate were negative. The in situ RT-PCR results demonstrated complete concordance with the results of I-FISH and RT-PCR. A fluorescence signal was detectable at 1/10(4) cells and became negative below this threshold with flow cytometry. The results of the present study suggest that (1) LUX primers can be used to efficiently detect BCR-ABL fusion mRNA by in-cell RT-PCR; (2) the novel technique is a specific and sensitive way of detecting fusion gene with potential clinical usefulness.

Stem cell enrichment approaches

Adult somatic tissue, and the tumours that arise therein, are maintained by a small population of stem cells. In addition to the self-renewal potential and pluripotency, these stem cells express several phenotypic traits that can be used in isolation and enrichment strategies. Since most of the traits are not exclusive to the stem cells however, the resultant populations are typically heterogeneous and variable from one isolation to another. In this article, we review the strategies for isolation of stem cells, and the limitations thereof, with emphasis on mesenchymal tissue and bone tumours. The emerging evidence suggests that stem cell is not a distinct entity, but rather an indefinite state along a spectrum, characterized by phenotypic traits, epigenetic factors and the microenvironment.

Development of a D-FISH method to detect DEK/CAN fusion resulting from t(6;9)(p23;q34) in patients with acute myelogenous leukemia

The t(6;9)(p23;q34)-DEK/CAN fusion occurs with an incidence of 1-5% in adult patients with acute myelogenous leukemia (AML) and tends to have an unfavorable prognosis at diagnosis. Due to the subtle appearance of this chromosome rearrangement, both initial detection and minimal residual disease (MRD) tracking by conventional karyotyping can be difficult. Unfortunately, no commercial or previously published fluorescence in situ hybridization (FISH) strategies exist for this recurrent anomaly. We have developed a highly sensitive assay using dual-color, double-fusion FISH (D-FISH), which can be used both for initial detection and MRD monitoring. We analyzed archived bone marrow samples from 15 patients with a previously identified t(6;9)(p23;q34) and 10 corresponding post-treatment samples. The results demonstrate that our D-FISH method effectively identified all abnormal samples, including a low-level MRD sample that was considered to be normal by conventional cytogenetic analysis. Normal value ranges were established from 30 negative controls to be < 0.6% when 500 interphase nuclei were analyzed. The development of this sensitive D-FISH strategy for the detection of the t(6;9)(p23;q34) adds to the AML FISH testing repertoire, and is effective in the detection of low-level disease in post-treatment samples in these patients.

Cytogenetic testing for therapeutic indication in cancer

The association of cytogenetic abnormalities with cancer is well established. However, due to the historic lack of specific insight into the functional role of these anomalies, they have mostly served as diagnostic and/or prognostic indicators. Recent developments in chronic myelogenous leukemia and breast cancer have raised hopes for specific cytogenetic alterations to serve as therapeutic targets. This article reviews the aid provided by molecular diagnostics in these exciting developments in the cancer arena.

Assessment of the response to imatinib in chronic myeloid leukemia patients - comparison between the FISH, multiplex and RT-PCR methods

OBJECTIVE

The objective of this study was to evaluate the kinetics of molecular response in chronic myeloid leukemia (CML) patients treated with imatinib and to compare between the fluorescent in situ hybridization (FISH), multiplex and real-time quantitative RT-PCR (RQ-PCR) methods with this respect.

METHODS

Molecular follow-up was carried out on 24 CML patients treated with imatinib. FISH analysis was performed according to the standard protocol. For RT-PCR the multiplex and RQ-PCR methods were used.

RESULTS

Sixty-three percent and 52% of the patients achieved complete remission according to FISH and multiplex RT-PCR analyses, respectively. Seventy-five percent of the patients achieved remission within the first year of treatment. In 83% of the cases the FISH and RT-PCR results were concordant. RQ-PCR analysis was carried out on 32 of the 41 samples negative by multiplex RT-PCR but only nine were negative. All samples with a BCR-ABL/ABL ratio below 2% were also negative by FISH. There was an excellent correlation between the RQ-PCR and the FISH tests.

CONCLUSIONS

Molecular remission according to FISH and multiplex RT-PCR can be achieved by imatinib within 1 yr of therapy. There is a good correlation between the FISH, multiplex and RQ-PCR results in terms of the kinetics of disappearance of the BCR-ABL transcript and the predictability of each method for the other. Although RQ-PCR is the most sensitive method for molecular follow-up, FISH and multiplex RT-PCR can be used as complementary tools, at least during the early period of treatment.

Clinical implications of advanced molecular cytogenetics in cancer

The field of cytogenetics has already entered the molecular era and a rapid expansion of its contribution is seen in genomic disease management. Among the evolving advanced molecular techniques, with an impeccable balance of high specificity, sensitivity and assay rapidity, fluorescence in situ hybridization has made its home in routine clinical laboratory. Today, its clinical application is vivid in every phase of disease management of a number of malignancies. The rapid growth in the knowledge of specific associations between distinct chromosomal abnormalities and different types of cancers will necessitate simultaneous detection of multiple abnormalities using multicolor/multiplex fluorescence in situ hybridization tests more often in the near future. Also, as the human genome sequence is ascertained, genome-wide screening with microarray technology will gain eminence in the clinical scenario, yield better solutions and bring the concept of personalized medicine in cancer closer to reality than ever before.

Innovations in the management of leukemia: role of biologic therapies

Chronic myelogenous leukemia (CML) results from clonal proliferation of malignant hematologic progenitor cells and is responsible for 7% to 15% of all adult leukemias. The hallmark of CML is a genetic translocation between chromosomes 9 and 22 (the Philadelphia chromosome), which creates the abnormal bcr-abl gene and a continuously activated Bcr-Abl protein. Bcr-Abl tyrosine kinase activity leads to signal transduction and cell growth. Traditional therapies for CML include allogeneic stem cell transplantation, interferon alfa, and oral chemotherapeutic agents. However, because Bcr-Abl is the causative abnormality in CML, it represents an ideal target for rational biologic therapy. Imatinib mesylate is an orally available tyrosine kinase inhibitor that specifically blocks Bcr-Abl function. Clinical trials have demonstrated that imatinib mesylate produces rapid responses in patients with all stages of CML, including those who were resistant to interferon alfa therapy or intolerant of it. When imatinib mesylate therapy was initiated early in the course of CML, there was a complete hematologic response in 98% of the patients and a complete cytogenetic response in 72% of the patients. Although long-term safety and survival data are not yet available, imatinib mesylate is a promising new treatment option for CML that targets the molecular cause of the disease.

Multiplex RT-PCR for the detection of common BCR-ABL fusion transcripts in paraffin-embedded tissues from patients with chronic myeloid leukemia and acute lymphoblastic leukemia

Diagnosis of chronic myeloid leukemia and acute lymphoblastic leukemia requires the investigation of the Philadelphia chromosome translocation t(9;22) or the molecular detection of BCR-ABL fusion transcripts. Determination of the type of fusion transcript is crucial for quantitative molecular monitoring the course of the disease during treatment. Histopathologists, who usually use formalin-fixed tissues, may be confronted with the need to investigate the BCR-ABL rearrangement when evaluating tumor forming infiltrates and bone marrow trephines from patients presenting with chronic myeloproliferative disorders. Therefore, we have established a one-tube multiplex RT-PCR for the detection of common BCR-ABL fusion transcripts (b2a2, b3a2, e1a2) in routinely processed tissues and bone marrow trephines with respect to the inevitable fragmentation of ribonucleic acids in these specimens. RT-PCR products allow distinct and unequivocal differentiation of the underlying fusion in either the Major- or minor-breakpoint cluster region. Detection of BCR-ABL fusion transcripts by multiplex RT-PCR in routinely processed and fixed tissues is a time- and cost-sparing tool for definite diagnosis of typical chronic myeloid leukemia and Philadelphia chromosome positive acute lymphoblastic leukemia.

Clinical applications of BCR-ABL molecular testing in acute leukemia

Recent advances in molecular genetics impact the health care and outcome of patients with acute lymphoblastic leukemia (ALL). BCR-ABL, a common molecular defect in adult ALL, is a valuable tumor marker whose detection influences prognosis and clinical management decisions. Molecular methods such as fluorescence in situ hybridization (FISH), reverse-transcriptase polymerase chain reaction (rtPCR), and real-time quantitative rtPCR can be used to detect the chimeric BCR-ABL gene or its transcripts. These molecular assays improve our ability to measure residual disease and to estimate risk of relapse. On the horizon are gene expression profiles that will likely provide additional information beyond what is obtainable with current clinical and laboratory approaches.

Molecular monitoring of chronic myeloid leukemia

The tyrosine kinase inhibitor imatinib mesylate (Gleevec) (formerly STI571) has proven to be an effective and safe new therapy for patients with chronic myeloid leukemia (CML). It has induced short-term hematologic control in many patients with advanced-phase CML, with some patients achieving durable responses. In chronic-phase patients it induces significantly better cytogenetic responses and lower progression rates than interferon-alpha. However, relapse is a significant problem, especially for advanced-phase patients, and imatinib alone appears unlikely to be curative in any patient group. Real-time quantitative polymerase chain reaction (Q-PCR) provides an accurate, sensitive, and noninvasive measure of residual leukemia in patients on imatinib. Levels of BCR-ABL in the blood correlate strongly with the bone marrow cytogenetic results and early measurement can predict subsequent cytogenetic response. Complete molecular responses (no BCR-ABL detected by real-time Q-PCR) are rarely achieved. Sequential real-time Q-PCR studies should facilitate rational patient management and allow comparison of different imatinib-based treatment strategies. It may be possible to define levels of molecular response that predict long-term disease control. In addition, by defining patterns of response, an early indication of imatinib resistance may be detected.

RARA fluorescence in situ hybridization overcomes the drawback of PML/RARA fluorescence in situ hybridization in follow-up of acute promyelocytic leukemia

Determination of the remission of acute promyelocytic leukemia (APL) after chemotherapy can be difficult because many cases of APL show reverse transcription polymerase chain reaction positivity after consolidation treatment. Moreover, the discrimination of leukemic promyelocytes and regenerating promyelocytes by morphology is sometimes difficult. Although PML/RARA fluorescence in situ hybridization (FISH) can help, the major drawback of FISH is its high false positive rate, which reaches up to 5-10%. We used RARA FISH at the initial diagnosis (16 cases) and follow-up of APL patients (21 cases) with t(15;17), though RARA FISH was originally designed to detect translocations involving the RARA gene rather than t(15;17), and compared the results with those of PML/RARA FISH. A reference range for PML/RARA and RARA FISH was set using 50 normal control specimens. Using a RARA split probe, we were able to lower the reference range for RARA rearrangement down to 1.5%, which is significantly lower than that of PML/RARA (8%). Actually 74.2% (46/62 cases) of cases with positive signals of the PML/RARA rearrangement by the PML/RARA probe, showed absolutely negative results with the RARA split probe. By conducting RARA FISH, we were able to significantly resolve the difficulty in interpreting results around cut-off value in PML/RARA FISH. In conclusion, we believe that once the PML/RARA rearrangement is confirmed either by G-banding or FISH, RARA FISH is more effective than PML/RARA during the follow-up of APL after treatment.

Early reduction of BCR-ABL mRNA transcript levels predicts cytogenetic response in chronic phase CML patients treated with imatinib after failure of interferon alpha

The degree of tumor load reduction as measured by cytogenetic response is an important prognostic factor for chronic myelogenous leukemia (CML) patients on therapy. We sought to determine whether BCR-ABL transcript levels can predict chromosomal response. Residual disease was evaluated in 120 CML patients in chronic phase (CP) treated with the selective tyrosine kinase inhibitor imatinib after resistance or intolerance to interferon alpha (IFN). Median time of therapy was 401 days (range 111-704). BCR-ABL and total ABL transcripts were measured in 486 peripheral blood (PB) specimens with a real time RT-PCR approach using fluorescent-labeled hybridization probes (LightCycler technology) and results were expressed as the ratio BCR-ABL/ABL. Cytogenetic response was determined in 3-monthly intervals: From 101 evaluable patients, 42 achieved a complete (CR, 0% Philadelphia chromosome (Ph)- positive metaphases), 18 a partial (PR, 1-34% Ph+), 13 a minor (MR, 35-94% Ph+), and 26 no response (NR, >94% Ph+). All PB samples were RT-PCR positive. The proportion of Ph+ metaphases and simultaneous BCR-ABL/ABL ratios correlated with r = 0.74, P < 0.0001. In order to investigate whether early molecular analysis may predict cytogenetic response, quantitative RT-PCR data obtained after 1 and 2 months of therapy were compared with cytogenetic response at 6 months. BCR-ABL/ABL ratios after 1 month were not predictive, but results after 2 months correlated with the consecutive cytogenetic response (P = 0.0008). The probability for a major cytogenetic response was significantly higher in patients with a BCR-ABL/ABL ratio <20% after 2 months of imatinib therapy. We conclude that: (1) quantitative determination of residual disease with real time RT-PCR is a reliable and sensitive method to monitor CML patients on imatinib therapy; (2) BCR-ABL/ABL ratios correlate well with cytogenetic response; (3) in IFN-pretreated patients all complete responders to imatinib have evidence of residual disease with the limited follow-up available; and (4) cytogenetic response at 6 months of therapy in CP patients is predictable with real time RT-PCR at 2 months.