Optimal Response in a Patient With CML Expressing BCR-ABL1 E6A2 Fusion Transcript With Nilotinib Therapy: A Case Report

The Many Faces of Philadelphia: A Mature T-Cell Lymphoma with Variant Philadelphia-Translocation and Duplication of the Philadelphia Chromosome

Background: T-cell prolymphocytic leukemia (T-PLL) is a rare mature T-cell lymphoma that is usually associated with poor prognosis and short overall survival. Methods: We present a case of a 61-year-old woman presenting with T-PLL and the leukemic cells harboring BCR::ABL1 (BCR-breakpoint cluster region; ABL1-ABL protooncogene 1) fusion transcripts as the result of a variant of t(9;22)(q34;q11) called Philadelphia translocation: t(9;22;18)(q34;q11;q21). Sequencing revealed a rare BCR transcript with an exon 6 breakpoint corresponding to e6a2 transcripts, which has thus far been reported in only 26 cases of leukemias. Results: After 9 months of follow-up, the disease progressed and required treatment. Following alemtuzumab and chemotherapy, a short course of imatinib therapy stabilized the disease for six months, which was followed by progression and the demise of the patient. Conclusions: To the best of our knowledge, this is the first report of a mature T-cell lymphoma with a variant Philadelphia-translocation and a very rare type of BCR::ABL1 transcript. This case highlights the importance of comprehensive genetic testing of malignancies, as abnormal molecular pathways may be uncovered that may be specifically targeted by drugs.

Chronic myelogenous leukemia coexpressing V-e16a2, V-e13a2, e13a2, and e14a2 BCR::ABL1 fusion transcripts: a case report and review of the literature

The coexistence of three or more transcripts in one patient with chronic myeloid leukemia (CML) is rarely reported. Thus, the disease progression and drug response are still unknown. This case report aimed to explore the drug response of CML with variant transcripts and to enrich the clinical treatment of rare types of CML. A 66-year-old Chinese female patient was diagnosed with chronic myeloid leukemia-chronic phase (CML-CP) expressing four BCR::ABL1 transcripts, including variant e16a2(V-e16a2), variant e13a2(V-e13a2), classical e13a2, and e14a2 transcripts. The patient was treated with flumatinib, a tyrosine kinase inhibitor (TKI).The variant transcripts reported exhibited a favorable response to TKI, and attention should be directed toward monitoring variant transcripts.

[Chronic myeloid leukemia with e6a2 fusion gene: a case report and literature review]

Chronic myeloid leukemia (CML) with e6a2 transcript type is very rare in clinic,which is usually related to disease aggressiveness. Its clinical characteristics and relationship with tyrosine kinase inhibitor efficacy are still unclear. In this paper, the clinical characteristics and related laboratory tests of a patient with e6a2 fusion gene positive CML characterized by multiple osteolytic bone destruction throughout the body and eosinophil infiltration in gastrointestinal tract, lymph nodes and other organs were retrospectively analyzed, and the relevant literature was reviewed. The patient was Ph chromosome positive with chromosome +8, and the common BCR::ABL1 transcript of CML was negative, but e6a2 transcript was positive detected by RT-PCR. The patient was treated with dasatinib 100 mg/d. Three months later, the patients achieved CHR, CCyR and MR4.0. However, the e6a2 transcript is very rare in clinical practice, and more cases of e6a2 transcript need to be studied to clarify its clinical characteristics and improve the treatment effect of these rare cases.

Atypical presentation of patients with chronic myeloid leukemia in chronic phase—Case report

The presence of the translocation t(9;22)(q34;q11), leading to the BCR::ABL1 fusion transcript, is the hallmark of chronic myeloid leukemia (CML). Nevertheless, atypical presentation at diagnosis can be challenging. However, although most patients with CML are diagnosed with the e13a2 or e14a2 BCR::ABL1 fusion transcripts, about 5% of them carry rare BCR::ABL1 fusion transcripts, such as e19a2, e8a2, e13a3, e14a3, e1a3, and e6a2. In particular, the e6a2 fusion transcript has been associated with clinically aggressive disease frequently presenting in accelerated or blast crisis phases. To date, there is limited evidence on the efficacy of front-line second-generation tyrosine kinase inhibitors for this genotype. Here, we report two patients, in whom the diagnosis of CML was challenging. The use of primers recognizing more distant exons from the common BCR::ABL1 breakpoint region correctly identified the atypical BCR::ABL1 e6a2 fusion transcript. Treatment with the second-generation tyrosine kinase inhibitor nilotinib was effective in our patient expressing the atypical e6a2 BCR::ABL1 fusion transcript.

Aleukemic Extramedullary Blast Crisis as an Initial Presentation of Chronic Myeloid Leukemia with E1A3 BCR-ABL1 Fusion Transcript

Right neck swelling and pain occurred in a 49-year-old man. A Blood count showed a slight increase in platelet count without leukemoid reaction. After a biopsy of the cervical mass and bone marrow aspiration, a diagnosis of extramedullary blast crisis (EBC) of chronic myeloid leukemia (CML) was made. Fluorescence in situ hybridization (FISH) analysis showed a BCR-ABL1 fusion signal, but results of real-time polymerase chain reaction (RT-PCR) for major and minor BCR-ABL1 transcripts were negative. We identified a rare e1a3 BCR-ABL1 fusion transcript. Administration of dasatinib resulted in disappearance of the extramedullary tumor. This is the first reported case of CML-EBC with e1a3 transcript. An aleukemic extramedullary tumor can be the initial presentation of CML.

Impact of the Breakpoint Region on the Leukemogenic Potential and the TKI Responsiveness of Atypical BCR-ABL1 Transcripts

Chronic Myeloid Leukemia (CML) is a hematological disorder characterized by the clonal expansion of a hematopoietic stem cell carrying the Philadelphia chromosome that juxtaposes the BCR and ABL1 genes. The ensuing BCR-ABL1 chimeric oncogene is characterized by a breakpoint region that generally involves exons 1, 13 or 14 in BCR and exon 2 in ABL1. Additional breakpoint regions, generating uncommon BCR-ABL1 fusion transcripts, have been detected in various CML patients. However, to date, the impact of these infrequent transcripts on BCR-ABL1-dependent leukemogenesis and sensitivity to tyrosine kinase inhibitors (TKIs) remain unclear. We analyzed the transforming potential and TKIs responsiveness of three atypical BCR-ABL1 fusions identified in CML patients, and of two additional BCR-ABL1 constructs with lab-engineered breakpoints. We observed that modifications in the DC2 domain of BCR and SH3 region of ABL1 affect BCR-ABL1 catalytic efficiency and leukemogenic ability. Moreover, employing immortalized cell lines and primary CD34-positive progenitors, we demonstrate that these modifications lead to reduced BCR-ABL1 sensitivity to imatinib, dasatinib and ponatinib but not nilotinib. We conclude that BCR-ABL1 oncoproteins displaying uncommon breakpoints involving the DC2 and SH3 domains are successfully inhibited by nilotinib treatment.