Minor breakpoint cluster region (m-BCR) positive chronic myeloid leukaemia with an acute lymphoblastic leukaemia onset: a case report

Coexistence of P190 and P210 BCR/ABL transcripts in chronic myeloid leukemia blast crisis resistant to imatinib

INTRODUCTION

Philadelphia chromosome (Ph) is a hallmark of chronic myeloid leukemia (CML), which exists in more than 90% CML and in 3% to 40% acute lymphoblastic leukemia (ALL).

CASE DESCRIPTION

A 25-year-old man was diagnosed with CML in chronic phase. He first received treatment with hydroxyurea, achieving hematological remission and following imatinib mesylate for main treatment. A year later, he began to appear unexplained high fever with ineffective antibiotic treatment and bone morrow and blood tests indicated blast crisis. Both BCR/ABL 210 and BCR/ABL 190 fusion transcript were positive. Imatinib resistance was confirmed by a screening for ABL kinase domain E255K mutations, and dasatinib was administered. After two months, the patient went on to hematological remission.

DISCUSSION AND EVALUATION

During medical treatment for CML, we experienced a relatively rare case with co-expression of the p210 and p190 encoding BCR-ABL transcripts in blastic phase. Imatinib resistance was confirmed and remission wasn't easily obtained, yet dasatinib was helpful. When resistance emerges, the treatment options include increasing the daily dose of imatinib, or combining imatinib with other agents. Of course, dasatinib, nilotinib and bone marrow transplantation are good choice as well.

CONCLUSIONS

The presence of p-190 transcript in CML may be related to progression of the disease. Thus monitoring the resistance of imatinib in CML patients, especially for advanced phase CML and BCR-ABL ALL, may be meaningful to guide clinical treatment and predict the prognosis.

Molecular drug targets in myeloproliferative neoplasms: mutant ABL1, JAK2, MPL, KIT, PDGFRA, PDGFRB and FGFR1

Therapeutically validated oncoproteins in myeloproliferative neoplasms (MPN) include BCR-ABL1 and rearranged PDGFR proteins. The latter are products of intra- (e.g. FIP1L1-PDGFRA) or inter-chromosomal (e.g.ETV6-PDGFRB) gene fusions. BCR-ABL1 is associated with chronic myelogenous leukaemia (CML) and mutant PDGFR with an MPN phenotype characterized by eosinophilia and in addition, in case of FIP1L1-PDGFRA, bone marrow mastocytosis. These genotype-phenotype associations have been effectively exploited in the development of highly accurate diagnostic assays and molecular targeted therapy. It is hoped that the same will happen in other MPN with specific genetic alterations: polycythemia vera (JAK2V617F and other JAK2 mutations), essential thrombocythemia (JAK2V617F and MPL515 mutations), primary myelofibrosis (JAK2V617F and MPL515 mutations), systemic mastocytosis (KITD816V and other KIT mutations) and stem cell leukaemia/lymphoma (ZNF198-FGFR1 and other FGFR1 fusion genes). The current review discusses the above-listed mutant molecules in the context of their value as drug targets.

Chronic myeloid leukemia: current application of cytogenetics and molecular testing for diagnosis and treatment

Chronic myeloid leukemia provides an illustrative disease model for both molecular pathogenesis of cancer and rational drug therapy. Chronic myeloid leukemia is a clonal stem cell disease caused by an acquired somatic mutation that fuses, through chromosomal translocation, the abl and bcr genes on chromosomes 9 and 22, respectively. The bcr/abl gene product is an oncogenic protein that localizes to the cytoskeleton and displays an up-regulated tyrosine kinase activity that leads to the recruitment of downstream effectors of cell proliferation and cell survival and consequently cell transformation. Such molecular information on pathogenesis has facilitated accurate diagnosis, the development of pathogenesis-targeted drug therapy, and most recently the application of molecular techniques for monitoring minimal residual disease after successful therapy. These issues are discussed within the context of clinical practice.

A child with Philadelphia positive (Ph+)-acute leukemia with myeloid morphology: one case of stem cell origin

Philadelphia positive (Ph+) acute myeloid leukemia (AML) is a rare and heterogeneous condition, mainly reported in adults, associated to poor prognosis and unfavorable response to therapy. Here we report clinical and laboratory findings in an 8-year-old patient diagnosed with Ph+ acute leukemia with myeloid (FAB M4) morphology. The patient consistently expressed variable levels of m-bcr, e1a2 transcripts during a 42-month follow-up after two different stem cell transplantation protocols. An immunophenotypic switch was documented, from a mixed, myeloid-lymphoid lineage to a full lymphoid phenotype following stem cell transplants, in association with an immature B-cell gene rearrangement profile and clonal instability during clinical progression. This report indicates a stem cell origin as previously suggested for Ph+ AML.

Chronic myeloid leukemia with expression of ALL-type BCR/ABL transcript: a case-report and review of the literature

CML with exclusive expression of ALL-type bcr/abl has only been rarely described. In some cases, the presence of this fusion gene has been associated to a differentiated subtype of CML that share some features with CMML, while in another case this molecular hallmark has been associated to a bad prognosis of the disease with a blast phase as clinical presentation or an early transformation to blast phase. We report a case of a 30-year-old woman who was diagnosed of CML in chronic phase in May 1989. She received treatment first with busulfan, achieving hematological remission and afterwards with interferon and Hydroxiurea. In February 1998, she was admitted at our hospital for an ABSCT. Then, molecular studies were performed. Multiplex PCR revealed the presence of a 481 bp product identified as the ela2 bcr/abl transcript and confirmed by sequencing. After 9 years from diagnosis, the patient remains in hematological remission and in good clinical condition.

p190 BCR-ABL rearrangement in chronic myeloid leukemia and acute lymphoblastic leukemia

A minority of chronic myeloid leukemia (CML) cases have breakpoint in the minor cluster region (m-bcr) of the BCR-ABL fusion gene. We report a patient with Ph-positive acute lymphoblastic leukemia and m-bcr breakpoint at diagnosis. The patient was treated with chemotherapy followed by an autologous peripheral blood stem cell transplantation, achieving a clinical and hematological complete remission but with persistence of the Philadelphia chromosome. One year later, she developed leukocytosis with a blood picture consistent with CML. She was treated with hydroxyurea and interferon alpha with no response. This is the second case of m-bcr CML reported presenting with features of lymphoid blast crisis or acute lymphoblastic leukemia.

[Chronic myeloid leukemia, biological aspects]

Chronic myeloid leukemia (CML) is a clonal myeloproliferative disorder of a stem cell, involving myeloid, erythroid, megacaryocyte, lymphoid B-cells and "natural killer" cells. The hallmark of CML is the Philadelphia (Ph) chromosome which is a shortened chromosome 22 (22q-) resulting from a reciprocal translocation involving chromosome 9 and chromosome 22, designed t (9;22) (q34;q11). This translocation juxtaposes parts of two genes; ABL on chromosome 9 and BCR (breakpoint cluster region) on chromosome 22. Transcription of the BCR/ABL fusion gene results in an hybrid mRNA that is translated into a 210 kDa or 190 kDa protein, depending on the location of the breakpoint in the bcr region. This protein plays a key role in CML: its tyrosine-kinase activity, that differs from the normal ABL product, may be involved in leukemic cell growth. Nonetheless, the loss of the negative cell growth regulation by c-ABL, or BCR/ABL fusion protein interaction with other cellular genes (such as RAS or c-MYC) could also be involved in CML pathophysiology. A better understanding of the molecular mecanisms of CML could lead to specific treatment, such as tyrosine-kinase inhibitors, synthetic oligodeoxynucleotides, or site-specific DNA-binding proteins designed against BCR/ABL oncogenic fusion sequence.