e19a2 BCR-ABL fusion transcript in typical chronic myeloid leukaemia: a report of two cases

P190 BCR-ABL1 in a Patient with Philadelphia Chromosome Positive T-Cell Acute Lymphoblastic Leukemia: A Rare Case Report and Review of Literature

T-acute lymphoblastic leukemia/lymphoblastic lymphoma (T-ALL/LBL) is rare and aggressive leukemia. Philadelphia chromosome positive (Ph+) is the most common cytogenetic abnormality in chronic myeloid leukemia (CML) and B-acute lymphoblastic leukemia (B-ALL). Ph+ T-ALL is exceeding rare and has a therapeutic and prognostic significance. The incidence and outcome of Ph+ T-ALL are unknown. Differentiation between Ph+ T-ALL/LBL and T-cell lymphoblastic crises of CML may be difficult. We report a rare case of adult de novo T-ALL with significant monocytosis, having Ph+ with (P190 BCR-ABL1) as a cytogenetic abnormality. He was treated with ALL induction chemotherapy and imatinib and achieved complete remission, then relapsed twice and expired shortly after the last CNS relapse.

Prognostic Significance of Transcript-Type BCR - ABL1 in Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is characterized by the presence of the BCR-ABL1 fusion gene. In more than 95% of CML patients, the typical BCR-ABL1 transcript subtypes are e13a2 (b2a2), e14a2 (b3a2), or the simultaneous expression of both. Other less frequent transcript subtypes, such as e1a2, e2a2, e6a2, e19a2, e1a3, e13a3, and e14a3, have been sporadically reported. The main purpose of this review is to assess the possible impact of different transcripts on the response rate to tyrosine kinase inhibitors (TKIs), the achievement of stable deep molecular responses (s-DMR), the potential maintenance of treatment-free remission (TFR), and long-term outcome of CML patients treated with TKIs. According to the majority of published studies, patients with e13a2 transcript treated with imatinib have lower and slower cytogenetic and molecular responses than those with e14a2 transcript. They should be considered a high-risk group that would most benefit from frontline treatment with second-generation TKIs (2GTIKIs). Although few studies have been published, similar significant differences in response rates to 2GTKIs have been not reported. The e14a2 transcript seems to be a favorable prognostic factor for obtaining s-DMR, irrespective of the TKI received, and is also associated with a very high rate of TFR maintenance. Indeed, patients with e13a2 transcript achieve a lower rate of s-DMR and experience a higher probability of TFR failure. According to most reported data in the literature, the type of transcript does not seem to affect long-term outcomes of CML patients treated with TKIs. In TFR, the e14a2 transcript appears to be related to favorable responses. 2GTKIs as frontline therapy might be a convenient approach in patients with e13a2 transcript to achieve optimal long-term outcomes.

Dual transcripts of BCR-ABL & different polymorphisms in chronic myeloid leukaemia patients

Background & objectives:

Chronic myeloid leukaemia is (CML) characterized by the presence of a hallmark chromosomal translocation, the Philadelphia chromosome. Although there are many reports available regarding the different variants of BCR-ABL in CML, we studied the co-expression of e13a2 and e14a2 transcripts and a few polymorphisms in CML patients.

Methods:

Molecular genetics approach was adapted to screen for polymorphisms, mutation and translocation in BCR, ABL kinase domain and BCR-ABL breakpoint region in 73 CML patients.

Results:

All eight patients with dual transcripts were found to harbour an exonic polymorphism (c.2700 T>C) and an intronic polymorphism (g.109366A>G) that were earlier reported to be associated with co-expression of both the transcripts. We also observed c.763G>A mutation in ABL kinase domain and two polymorphisms, c.2387 A>G and c.2736A>G in the BCR gene.

Interpretation & conclusions:

Though our data support the previous findings that co-expression of BCR-ABL transcripts is due to the occurrence of exonic and intronic polymorphisms in the BCR gene, it also shows that the intronic polymorphism can arise without the linked exonic polymorphism. The occurrence of ABL kinase domain mutation is less frequent in Indian population.

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.

Rapid Evolution to Blast Crisis Associated with a Q252H ABL1 Kinase Domain Mutation in e19a2 BCR-ABL1 Chronic Myeloid Leukaemia

A minority of chronic myeloid leukaemia (CML) patients express variant transcripts of which the e19a2 BCR-ABL1 fusion is the most common. Instances of tyrosine kinase inhibitor (TKI) resistance in e19a2 BCR-ABL1 CML patients have rarely been reported. A case of e19a2 BCR-ABL1 CML is described in whom imatinib resistance, associated with a Q252H ABL1 kinase domain mutation, became apparent soon after initiation of TKI therapy. The patient rapidly transformed to myeloid blast crisis (BC) with considerable bone marrow fibrosis and no significant molecular response to a second generation TKI. The clinical course was complicated by comorbidities with the patient rapidly succumbing to advanced disease. This scenario of Q252H-associated TKI resistance with rapid BC transformation has not been previously documented in e19a2 BCR-ABL1 CML. This case highlights the considerable challenges remaining in the management of TKI-resistant BC CML, particularly in the elderly patient.

Early Complete Molecular Response to First-Line Nilotinib in Two Patients with Chronic Myeloid Leukemia Carrying the p230 Transcript

Chronic myeloid leukemia (CML) with the rare fusion gene e19a2, encoding a p230 protein, has been described in patients with typical or rather aggressive clinical course. Although tyrosine kinase inhibitors (TKIs) induce a substantial cytogenetic and molecular response in all phases of CML, a minority of p230 positive patients have been treated with TKIs. We report two cases of CML patients carrying the p230 transcript, who achieved fast and deep complete molecular response (CMR) after frontline treatment with nilotinib. Our results suggest the use of nilotinib as frontline agent for the treatment of this CML variant.

Chronic Myeloid Leukemia with e19a2 BCR-ABL1 Transcripts and Marked Thrombocytosis: The Role of Molecular Monitoring

While most patients with chronic myeloid leukemia (CML) express either e13a2 or e14a2 BCR-ABL1 transcripts, a significant minority expresses variant transcripts, of which e19a2 is the most common. Although considered to have a relatively favourable outcome, reported responses to tyrosine kinase inhibitor (TKI) therapy are variable with molecular monitoring in CML patients with e19a2 BCR-ABL1 transcripts rarely reported. A case of e19a2 BCR-ABL1 CML with marked thrombocytosis is described in which the value of molecular monitoring is emphasised during treatment interruptions, dose reductions, and changes. This case serves to demonstrate the requirement for prospective real-time quantitative PCR (RQ-PCR) assays for patients with variant BCR-ABL1 transcript types and standardisation of such assays to enable modern patient management.

Identification of potential drug targets implicated in Parkinson's disease from human genome: insights of using fused domains in hypothetical proteins as probes

High-throughput genome sequencing has led to data explosion in sequence databanks, with an imbalance of sequence-structure-function relationships, resulting in a substantial fraction of proteins known as hypothetical proteins. Functions of such proteins can be assigned based on the analysis and characterization of the domains that they are made up of. Domains are basic evolutionary units of proteins and most proteins contain multiple domains. A subset of multidomain proteins is fused domains (overlapping domains), wherein sequence overlaps between two or more domains occur. These fused domains are a result of gene fusion events and their implication in diseases is well established. Hence, an attempt has been made in this paper to identify the fused domain containing hypothetical proteins from human genome homologous to parkinsonian targets present in KEGG database. The results of this research identified 18 hypothetical proteins, with domains fused with ubiquitin domains and having homology with targets present in parkinsonian pathway.

E355G mutation appearing in a patient with e19a2 chronic myeloid leukaemia resistant to imatinib

The development of imatinib is a milestone in the treatment of chronic myeloid leukaemia (CML), and its therapeutic effect has been extensively investigated in patients with CML who carry M-bcr and m-bcr BCR-ABL fusion transcripts. However, knowledge about its therapeutic effect on patients with CML who have the rare BCR-ABL fusion transcript e19a2 (mu-bcr) remains sparse. This report describes a patient with Philadelphia-positive chronic myeloid leukaemia with e19a2 rearrangement, in whom E355G mutation had been acquired. The patient was resistant to imatinib treatment based on conventional cytogenetic and fluorescence in situ hybridisation analysis.

Targeted therapy of chronic myeloid leukemia

Inhibition of BCR-ABL with kinase inhibitors has become a well-accepted strategy for targeted therapy of Philadelphia-positive (Ph(+)) chronic myeloid leukemia (CML) and has been shown to be highly effective in controlling the disease. However, BCR-ABL kinase inhibitors do not efficiently kill leukemic stem cells (LSCs), indicating that this therapeutic strategy does not lead to a cure of CML. Development of curative therapies of CML require the identification of genes/pathways that play critical roles in survival and self-renewal of LSCs. Targeting of these key BCR-ABL downstream genes provides an opportunity to eradicate LSCs, as shown in our work that identifies the Alox5 gene as a key regulator of the function of CML LSCs. Immediate clinical trials are necessary to test the effectiveness of targeting a key BCR-ABL downstream gene in eradicating LSCs in CML patients. In this review, we will discuss current targeted therapies of CML using BCR-ABL kinase inhibitors, with a focus on the importance of developing a targeted therapy of CML through identification of target genes in CML LSCs.

A report of early cytogenetic response to imatinib in two patients with chronic myeloid leukemia at accelerated phase and carrying the e19a2 BCR-ABL transcript

The development of imatinib is a milestone in the treatment of chronic myeloid leukemia (CML), and its therapeutic effect has been extensively investigated in CML patients carrying M-bcr and m-bcr BCR/ABL fusion transcripts. However, our knowledge about its therapeutic effect on CML patients with rare BCR/ABL fusion transcripts e19a2(u-bcr) remains sparse. Here, we report on two CML patients with e19a2 transcripts who rapidly progressed into the accelerated phase, further confirming the possibility that 19a2 might be associated with an unfavorable prognosis in CML. Moreover, these patients showed early response to imatinib treatment. Our study highlights the clinical potential of imatinib for this patient subgroup.