Chronic myeloid leukemia: cytogenetic methods and applications for diagnosis and treatment

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.

Assessing Measurable Residual Disease in Chronic Myeloid Leukemia. BCR-ABL1 IS in the Avant-Garde of Molecular Hematology

Chronic myelogenous leukemia (CML) is a malignancy of the myeloid cell lineage characterized by a recurrent chromosomal abnormality: the Philadelphia chromosome, which results from the reciprocal translocation of the chromosomes 9 and 22. The Philadelphia chromosome contains a fusion gene called BCR-ABL1. The BCR-ABL1 codes for an aberrantly functioning tyrosine kinase that drives the malignant proliferation of the founding clone. The advent of tyrosine kinase inhibitors (TKI) represents a landmark in the treatment of CML, that has led to tremendous improvement in the remission and survival rates. Since the introduction of imatinib, the first TKI, several other TKI have been approved that further broadened the arsenal against CML. Patients treated with TKIs require sensitive monitoring of BCR-ABL1 transcripts with quantitative real-time polymerase chain reaction (qRT-PCT), which has become an essential part of managing patients with CML. In this review, we discuss the importance of the BCR-ABL1 assay, and we highlight the growing importance of BCR-ABL1 dynamics. We also introduce a mathematical correction for the BCR-ABL1 assay that could help homogenizing the use of the ABL1 as a control gene. Finally, we discuss the growing body of evidence concerning treatment-free remission. Along with the continuous improvement in the therapeutic arsenal against CML, the molecular monitoring of CML represents the avant-garde in the struggle to make CML a curable disease.

Recurrent chronic myeloid leukemia with t (9;22;16) (q34; q11; p13) treated by nilotinib: A case report

RATIONALE

Variant Philadelphia chromosome translocations involving chromosomes other than chromosomes 9 and 22 have been reported in 5% to 10% of patients with chronic myeloid leukemia (CML). Here, a case of CML with a t (9, 22, 16) (q34; q11; p13) translocation, which has never been described, is reported.

PATIENT CONCERNS

A 59-year-old female with dry cough, referred to our hospital, exhibited hepatosplenomegaly, high basophil count, and high platelet count at admission without any other known chronic diseases.

DIAGNOSES

The patient was diagnosed with CML with the translocation t (9;22;16) (q34; q11; p13). The patient was treated with imatinib, a first-generation tyrosine kinase inhibitor (TKI), discontinuously, achieving a complete hematological response for 7 years. Since November 8, 2017, the patient had recurrent fever, and her platelet count rose to 1422 × 10/L. Subsequently, the E279K mutation in the BCR-ABL kinase region was detected.

OUTCOMES

According to a previous report, this mutation confers sensitivity to nilotinib, a second-generation TKI. In the end, the patient received treatment with nilotinib and showed a complete hematological response.

LESSONS

The present study reports a rare case of CML with Ph chromosome and a t (9;22;16) (q34; q11; p13) translocation. For such cases about CML with variant Philadelphia chromosome translocations or BCR-ABL kinase region mutation, TKI may still be valuable.

miRNAs in chronic myeloid leukemia: small molecules, essential function

Chronic myeloid leukemia (CML) is a myeloproliferative disorder associated with clonal expansion of cancerous bone marrow stem cells. Tyrosine kinase inhibitors (TKIs) targeting Bcr-Abl oncoprotein are the first-line therapy for most CML patients, however, some are unresponsive to it or develop resistance. Recently, microRNAs (miRNAs) have been implicated in the progression of CML and the development of TKI resistance based on their important regulatory function in cell homeostasis. MicroRNAs are small noncoding RNAs that post-transcriptionally regulate gene expression. Since microRNAs can function either as oncogenes or tumor suppressor genes in leukemogenesis, the potential of using them as therapeutic targets by inhibiting or amplifying their activity, opens up new opportunities for leukemia therapy. In this review, we focus on recent studies on the important roles of microRNAs in the pathogenesis of CML and their relevance as biomarkers for diagnosis, monitoring disease progression, and treatment response.

Epigenetic-based companion diagnostics

In current medical practice, when a patient is diagnosed with cancer the treating physician generally follows a standard protocol, assigning the treatment that gives a favorable response in the largest proportion of patients. However, in many individual instances this approach may not be the most effective solution and, typically, treatment is only initiated or altered once the cancer has actually started progressing. During this process, patients will lose treatment time waiting to start chemotherapy or will endure severe side effects associated with toxic chemotherapeutic treatments. While some patients are undertreated because current diagnostic methods cannot provide accurate enough information regarding the aggressiveness or drug response of their disease, others with nonaggressive forms of cancer are overtreated and unnecessarily undergo the side effects associated with chemotherapeutic treatment. Epigenetic markers have been widely investigated and are considered key regulators of cellular transcription. Histone modifications and DNA methylation have been demonstrated to play key roles in maintaining stem-cell-like states, cellular differentiation and cancer. In particular, DNA methylation is a frequent, abundant and stable cancer mark, with an inherent role in oncogenesis and tumor progression. In this article, the potential of DNA methylation as a companion diagnostic is assessed, illustrated by exploring some development paths. Epigenetic silencing of MGMT is a key example of how biomarker development, biological pathways and clinical utility come together, serving as a hallmark of epigenetic companion diagnostics.