Deletion of the 5'ABL region in Philadelphia chromosome positive chronic myeloid leukemia: frequency, origin and prognosis

The incidence of atypical patterns of BCR-ABL1 rearrangement and molecular-cytogenetic response to tyrosine kinase inhibitor therapy in newly diagnosed cases with chronic myeloid leukemia (CML)

Background

To analyze the frequency of atypical fluorescence in situ hybridization signal patterns and estimate the complete cytogenetic response (CCyR) and major molecular response (MMR) during 12 months of tyrosine kinase inhibitor therapy in patients with newly diagnosed chronic myeloid leukemia.

Methods

The study included bone marrow and peripheral blood samples from 122 patients with newly diagnosed chronic myeloid leukemia. Detection of the breakpoint cluster region—Abelson fusion gene (BCR-ABL1) was performed using fluorescence in situ hybridization with a dual-color dual-fusion translocation probe, and MMR analysis was performed using the real-time quantitative polymerase chain reaction method.

Results

Variant translocation was determined in 10 samples and a deletion on the derivative chromosome 9 (del/der(9)) was found in 20 samples. The rates of CCyR and MMR were similar between patients with reciprocal translocation, variant translocation, deletion of derivative BCR, or ABL1-BCR fusion gene. The Kaplan-Meier test did not show any significant differences in the rates of CCyR and MMR among those groups of patients.

Conclusion

The frequencies of variant translocation and del/der(9) in the present study agree with the results of other studies performed worldwide. No differences were observed in the rates of CCyR and MMR between patients with atypical patterns and reciprocal translocation.

Multi-agent chemotherapy overcomes glucocorticoid resistance conferred by a BIM deletion polymorphism in pediatric acute lymphoblastic leukemia

A broad range of anti-cancer agents, including glucocorticoids (GCs) and tyrosine kinase inhibitors (TKIs), kill cells by upregulating the pro-apoptotic BCL2 family member, BIM. A common germline deletion in the BIM gene was recently shown to favor the production of non-apoptotic BIM isoforms, and to predict inferior responses in TKI-treated chronic myeloid leukemia (CML) and EGFR-driven lung cancer patients. Given that both in vitro and in vivo GC resistance are predictive of adverse outcomes in acute lymphoblastic leukemia (ALL), we hypothesized that this polymorphism would mediate GC resistance, and serve as a biomarker of poor response in ALL. Accordingly, we used zinc finger nucleases to generate ALL cell lines with the BIM deletion, and confirmed the ability of the deletion to mediate GC resistance in vitro. In contrast to CML and lung cancer, the BIM deletion did not predict for poorer clinical outcome in a retrospective analysis of 411 pediatric ALL patients who were uniformly treated with GCs and chemotherapy. Underlying the lack of prognostic significance, we found that the chemotherapy agents used in our cohort (vincristine, L-asparaginase, and methotrexate) were each able to induce ALL cell death in a BIM-independent fashion, and resensitize BIM deletion-containing cells to GCs. Together, our work demonstrates how effective therapy can overcome intrinsic resistance in ALL patients, and suggests the potential of using combinations of drugs that work via divergent mechanisms of cell killing to surmount BIM deletion-mediated drug resistance in other cancers.

[An elderly case of chronic myeloid leukemia in which BCR/ABL decreased or disappeared, following imatinib therapy after each episode of blast crisis]

An elderly woman with chronic myeloid leukemia-chronic phase (CML-CP) aged at 67 underwent imatinib therapy. Ph chromosomes gradually decreased, but imatinib was discontinued after 10 months because of aggravated skin eruptions. Three months later, myeloid blast crisis (MBC) occurred. DXR+VCR+PSL chemotherapy and imatinib therapy was administered, and return to CP (RTC) was achieved with the disappearance of Ph chromosomes and a marked decrease of BCR/ABL (FISH). Although imatinib therapy was continued, a second MBC was diagnosed, 13 months after RTC. Chemotherapy, using mainly VCR+PSL was performed and imatinib was discontinued. RTC was achieved, and Ph chromosomes and BCR/ABL again disappeared. One year later, a 3rd MBC developed, and chemotherapy using Ara-C+DNR was performed. A 3rd RTC was achieved, and BCR/ABL decreased. This CML case was resistant to imatinib, but chemotherapy was effective in all 3 episodes of MBC, and BCR/ABL decreased or disappeared.

Deletion size characterization of der(9) deletions in Philadelphia-positive chronic myeloid leukemia

About 95% of the CML patients with chronic myeloid leukemia (CML) have a Philadelphia chromosome resulting from a reciprocal translocation between bands 9q34 and 22q11.2 that juxtaposes the 3' region of the ABL gene to the 5' region of BCR. Over the past few years, submicroscopic deletions due to the loss of sequences proximal to chromosome 9 breakpoint or distal to chromosome 22 breakpoint have been found using fluorescence in situ hybridization (FISH). Among 150 CML bone marrow samples analyzed by molecular cytogenetics in our laboratory, 11 had a der(9) deletion detectable by FISH (deletion of the 5'ABL region and 3'BCR region in 10 samples and deletion of the 5'ABL region solely in 1 sample). To delineate the size of the deletions, FISH mapping was performed using 22 bacterial artificial chromosomes (BACs), 11 on either side of the breakpoints, the mean distance between BACs being 0.5 Mb. The deletion size of the 5'ABL region on the der(9) extended from 2 to 5 Mb, the minimal deletion size being localized between BACs RP11-101E3 and RP11-83J21. In two patients, the deletion size of the 3'BCR region was about 500 kb (between RP11-80O7 and RP11-681C06). The poor prognosis associated with these deletions was postulated by several workers to be explained by haploinsufficiency of a tumor suppressor gene. However, in our cases, the hypothetical deletion of one or more tumor suppressor genes is not sufficient to explain the poor response to interferon therapy, but the good response to imatinib treatment. We think that there could be one or more genes coding for interferon receptors or for proteins acting directly or indirectly with these receptors in the deleted regions.

Del(5q) and MLL amplification in homogeneously staining region in acute myeloblastic leukemia: a recurrent cytogenetic association

We report here a 71 year-old female presenting with acute myeloblastic leukemia (FAB-M1) after treatment of essential thrombocythemia with Vercyte. Conventional cytogenetic techniques showed a complex karyotype, 44,XX,-5,-7,-11,add(11)(q23),-14,+mar,+r. The use of several fluorescent in situ hybridizations (FISH) lead to the identification of these complex rearrangements. The marker was found to be tricentric, with pericentromeric material of chromosome 7 inserted in the short arm of chromosome 5, resulting in monosomy 5q and 7q. The derivative chromosome 11 was dicentric and had subtelomeric sequences of 11p on both ends; several copies of the MLL gene were located in two different regions separated by a centromere of chromosome 11. Twenty-one cases, including ours, of myelodysplastic syndromes and acute myelogenous leukemia with MLL amplification present in hsr or dmin were found in the literature. Most of these patients shared some characteristics: they were old, they had de novo acute myeloid leukemia (AML) with a complex karyotype and a short survival, 90% of them having also a del(5q). Therefore, the simultaneous presence of MLL amplification and del(5q) appears to be a nonrandom association that could be the signature of AML in elderly patients with a poor prognosis.

Screening by fluorescence in situ hybridization for MLL status at diagnosis in 239 unselected patients with acute myeloblastic leukemia

A large number of abnormalities involving the MLL gene have been associated with hematological malignancies, including acute myeloblastic leukemias (AML). Given the overall unfavorable prognosis of AML with an MLL abnormality, its reliable and accurate detection is needed for informed treatment decision. We therefore investigated the occurrence of MLL abnormalities in 239 unselected consecutive AML patients, using conventional cytogenetic and fluorescent in situ hybridization (FISH) analyses. FISH analysis for MLL was performed using a commercial dual-color probe. Of the 239 patients, 30 (12.6%) showed MLL abnormalities under FISH analysis, 10 (4.2%) showed a split signal indicating the disruption of the MLL gene by translocation or insertion, and 20 (8.4%) showed overrepresentation of the MLL gene without evidence of rearrangement. MLL abnormalities were more frequently found in AML-M5 and M4, mainly as rearrangements, and in AML-M2, mainly as overrepresentation. Our results are in agreement with those reported in other studies. All M2, M4, and M5 AML patients without known recurrent translocations, such as t(8;21) and inv(16), should be investigated by FISH with an MLL probe because it allows the detection of MLL rearrangement that would go undetected by conventional cytogenetics and because it has the ability of detecting multiple copies of the MLL gene in, for example, marker chromosomes and double minutes.

Rearrangement of the MLL gene in acute myeloblastic leukemia: report of two rare translocations

Band 11q23 is known to be involved in translocations and insertions with a variety of partner chromosomes. They lead to MLL rearrangement, resulting in a fusion with numerous genes. We report here 2 male adults in whom a diagnosis of acute myelomonoblastic leukemia (FAB M4) and acute monoblastic leukemia (FAB M5) was made. Conventional cytogenetic techniques showed a 45,XY,t(1;11)(p32;q23),-7 karyotype in the first case and a 46,XY, t(11;17)(q23;q21) in the second case. Fluorescent in situ hybridization (FISH) with a specific MLL probe showed the gene to be disrupted, the 3' region being translocated on the derivative chromosomes 1 and 17, respectively. Fourteen and 24 patients, including ours, with acute myeloblastic leukemia associated with a t(1;11)(p32;q23) and a t(11;17)(q23;q21), respectively have been reported in the literature. Several patients with the latter translocation have also been identified to have acute lymphoblastic leukemia (ALL). Although both translocations are preferentially associated with monocytic differentiation, the t(11;17)(q23;q21) is more common in adults and has been reported in many patients with ALL, compared to the t(1;11)(p32;q23).