Translocation (3;21)(q26;q22) in therapy-related myelodysplasia following drugs targeting DNA-topoisomerase II combined with alkylating agents, and in myeloproliferative disorders undergoing spontaneous leukemic transformation

Something Old, New, Borrowed, Blue: Anthracenedione Agents for Treatment of Multiple Sclerosis

OBJECTIVE

This study aimed to present anthracenedione agents that have been used to treat multiple sclerosis (MS), problems related to their use, and knowledge gained from our experiences using these agents to develop more efficacious drugs with fewer adverse effects.

METHODS

We review preclinical and clinical data during the development mitoxantrone, an anthracycline, for the treatment of MS; benefits and potential risks; and strategies to reduce complications of anthracyclines.

RESULTS

Mitoxantrone had unacceptable and greater-than-anticipated toxicity for use in a chronic disease such as MS. Adverse effects included cardiotoxicity, treatment-associated leukemia, and amenorrhea. Toxicity was identified primarily in retrospect. Structurally related compounds include pixantrone (BBR2278) and BBR3378. Pixantrone is in clinical development in oncology. BBR3378 prevents the development of autoimmunity and experimental autoimmune encephalomyelitis and blocks experimental autoimmune encephalomyelitis even when given after the onset of autoimmunity.

CONCLUSIONS

There remains a need for effective MS treatment, particularly for nonrelapsing forms of MS. Mitoxantrone was the first nonbiologic drug approved by the Food and Drug Administration for use in MS. Chromophore modification of anthracenedione agents yielded a novel class of DNA binding agents (aza-anthracenediones such as pixantrone and aza-anthrapyrazoles such as BBR3378) with the potential for less cardiotoxicity compared with mitoxantrone. There is a need for long-term observation for delayed toxicity among humans enrolled in pixantrone trials. Preclinical toxicity studies for delayed toxicities in rodents and other models are warranted before consideration of derivatives of anthracenediones, aza-anthrazenediones, or aza-anthrapyrazoles for use in human MS clinical trials.

Myelodysplastic syndrome/acute myeloid leukemia with t(3;21)(q26.2;q22) is commonly a therapy-related disease associated with poor outcome

The t(3;21)(q26.2;q22) translocation is rare in cases of myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). We studied 17 patients with MDS/AML associated with t(3;21) and compared them with 17 patients with MDS associated with inv(3) (q21q26.2)/t(3;3)(q21;q26.2), because these entities share 3q26 locus abnormalities. The t(3;21) group included 9 men and 8 women, with a median age of 62 years (range, 13-81 years). One case was de novo AML and 16 cases were therapy-related, including 12 MDS (blasts, <15%) and 4 AML (blasts, 33%-50%). All patients had multilineage dysplasia, whereas none had thrombocytosis. Additional cytogenetic aberrations were identified in 12 cases, including -7/7q (n = 9) and a complex karyotype (n = 7). All patients died, with 1- and 2-year survival rates of 35% and 6%, respectively. Although multilineage dysplasia and frequent association with -7/7q were similar in both groups, MDS/AML cases associated with t(3;21) have a higher frequency of therapy-related disease and shorter survival times, suggesting that they are distinct from MDS/AML cases associated with inv(3)/t(3;3).

Risk of leukemic transformation in PV and ET patients

Despite a prolonged survival of around 15 years linked to a prolonged complete remission induced by myelosuppression, myeloproliferative syndromes such as polycythemia vera (PV) and essential thrombosis (ET) remain at risk of lethal adverse affects such as thrombotic events and acute transformation. The major risk at diagnosis, in the absence of treatment, is essentially thrombosis. Different therapeutic trials have shown the necessity to maintain circulating blood cells (RBC and platelets counts) near normal levels to avoid thrombosis. Phlebotomies alone in PV lead in the long run to metaplasia and increased platelet counts and should only be kept for emergency cell count reduction. Myelosuppression is thus until recently the most widely accepted effective alternative. However, the effects of long term chronic administration of myelosuppresive agents needs to be analyzed and monitored as the biological changes which appear during the course of these diseases linked or not to the intrinsic clonal haematopoietic abnormality may lead to malignant transformation. Thus, alternative therapies need to be evaluated and predisposition factors taken in account.

AML1 interconnected pathways of leukemogenesis

The AML1 transcription factor, identified by the cloning of the translocation t(8;21) breakpoint, is one of the most frequent targets for chromosomal translocations in leukemia. Furthermore, polysomies and point mutations can also alter AML1 function. AML1, also called CBF alpha 2, PEBP alpha 2 or RUNX1, is thus implicated in a great number of acute leukemias via a variety of pathogenic mechanisms and seems to act either as an oncogene or a tumor suppressor gene. Characterization of AML1 knockout mice has shown that AML1 is necessary for normal development of all hematopoietic lineages and alterations in the overal functional level of AML1 can have a profound effect on hematopoiesis. Numerous studies have shown that AML1 plays a vital role in the regulation of expression of many genes involved in hematopoietic cell development, and the impairment of AML1 function disregulates the pathways leading to cellular proliferation and differentiation. However, heterozygous AML1 mutations alone may not be sufficient for the development of leukemia. A cumulative process of mutagenesis involving additional genetic events in functionally related molecules, may be necessary for the development of leukemia and may determine the leukemic phenotype. We review the known AML1 target genes, AML1 interacting proteins, AML1 gene alterations and their effects on AML1 function, and mutations in AML1-related genes associated with leukemia. We discuss the interconnections between all these genes in cell signaling pathways and their importance for future therapeutic developments.

A unique AML1 (CBF2A) rearrangement, t(1;21)(p32;q22), observed in a patient with acute myelomonocytic leukemia

The AML1 (CBFA2) gene is the most frequent target of chromosomal rearrangements observed in human acute leukemia. These rearrangements include the commonly reported t(8;21)(q22;q22) or AML1/ETO fusion in AML-M2, the t(3;21)(q26;q22) or AML1 fusion with one of three genes, MDS1, EAP or EVI1, in therapy-related AML and MDS, as well as in blast crisis in CML and the t(12;21)(p13;q22) or TEL/AML1 fusion in B-cell ALL. In addition to the t(3;21), other AML1 translocations have also been reported in therapy-related MDS and AML, particularly after treatment with topoisomerase II inhibitors. AML1 gene rearrangements have also been observed less frequently with numerous other chromosomal partners. Here, we describe a patient with AML-M4 and a previously unreported rearrangement involving the AML1 locus and an unknown locus on the short arm of chromosome 1 at 1p32.

Secondary myelodysplastic syndrome after fludarabine therapy of a low-grade non-Hodgkin's lymphoma

We diagnosed a probable fludarabine-induced secondary MDS approximately 18 months after treatment of a low grade non-Hodgkin's lymphoma. After diagnosis of a B-cell lymphoma composed of relatively small cells, fludarabine was administered between May and October, 1997, to a 64-year-old female patient. In December 1998, a mild bicytopenia was present with a leukocyte count of 3800/microl and platelets of 142000/microl. The white cell differential count was normal. The hemoglobin level was normal, but MCV was elevated. Bone marrow cytology revealed normal cellularity with dyserythropoiesis and dysmegakaryocytopoiesis. PAS staining showed scattered positivity in early erythroid cells. In 12 of 20 mitoses, the karyotype showed complex rearrangements, described as 46,XX,t(4;11)(q23?24;q13),del(5q),del(7)(q22),+mar[8]/45,-3. A diagnosis of treatment-related MDS was made. While there was no evidence of bone marrow infiltration by the lymphoma, CT scans demonstrated paraaortic lymph nodes up to 10 cm in diameter. After one course of CHOP chemotherapy, prolonged bone marrow aplasia and septic complications occurred. Chemotherapy was abandoned and Rituximab was administered. In July and November, 1999, bilateral pneumonia and urinary tract infection, respectively, were treated with antibiotics. NHL was in complete remission, but peripheral blood counts deteriorated markedly, and transfusions of packed red cells had to be started in November, 1999. The suspicion of leukemic transformation could not be confirmed because the patient declined further bone marrow biopsies. In December, 1999, the patient died from pneumonia.

Spectral karyotyping (SKY) refinement of a complex karyotype with t(20;21) in a Ph-positive CML patient submitted to peripheral blood stem cell transplantation

A patient with a Ph-positive chronic myeloid leukaemia (CML) was submitted to allogeneic peripheral blood stem cell transplantation from an HLA-haploidentical related donor 7 years after the diagnosis. Six months later, he showed a disease relapse while cytogenetic analysis displayed a complex karyotype. To characterise the chromosomal rearrangements spectral karyotype (SKY) analysis was used. This redefined all chromosome rearrangements and revealed a t(20;21)(q11;q22). FISH analysis with a specific probe for the AML1 gene disclosed disruption of this gene which was partially translocated on to the long arm of chromosome 20. It is likely that this rearrangement, unusual for CML, was implicated in the disease evolution towards blastic crisis (BC).

Treatment-related leukaemia--a clinical and scientific challenge

The development of a second tumour, including treatment-related leukaemia (TRL), is the most devastating complication of intensive cancer chemotherapy. This is especially relevant in the paediatric population as over 70% of children diagnosed with a malignancy will now live at least 5 years. Most TRLs are myeloid leukaemias and carry an overall poor prognosis when compared with their de novo counterparts. Despite the well known association with specific cytotoxic agents, improved understanding of the pathogenesis and risk factors of TRL is ultimately essential if we are to develop successful strategies for prevention and treatment. Here we review these aspects, together with the clinical and diverse biological features of this complication and the efficacy of current therapy.

Incidence of TEL/AML1 Fusion in Children With Relapsed Acute Lymphoblastic Leukemia

The TEL/AML1 fusion associated with t(12;21)(p13;q22) is the most common gene rearrangement in childhood leukemia, occurring in approximately 25% of pediatric acute lymphoblastic leukemia (ALL), and is associated with a favorable prognosis. For example, a cohort of pediatric patients with ALL retrospectively analyzed for theTEL/AML1 fusion treated on Dana-Farber Cancer Institute (DFCI) ALL Consortium protocols between 1980 to 1991 demonstrated a 100% relapse-free survival in TEL/AML1-positive patients with a median of 8.3 years of follow-up. However, two recent studies analyzing pediatric patients with relapsed ALL have reported the same incidence of the TEL/AML1 rearrangement as in patients with newly diagnosed ALL, suggesting that TEL/AML1 positivity is not a favorable prognostic indicator. To clarify this apparent discrepancy, 48 pediatric patients treated on Dana-Farber Cancer Institute (DFCI) protocols with ALL at first or second relapse were tested forTEL/AML1 using reverse transcriptase-polymerase chain reaction (RT-PCR). The TEL/AML1 fusion was identified in only 1 of 32 analyzable relapsed ALL patients, in concordance with our previous reports of improved disease-free survival in TEL/AML1-positive patients. The low frequency of TEL/AML1-positive patients at relapse is significantly different than that reported in other studies. Although there are several potential explanations for the observed differences in TEL/AML1-positive patients at relapse, it is plausible that relapse-free survival in TEL/AML1-positive patients may be changed with different therapeutic approaches. Taken together, these results support the need for prospective analysis of prognosis in TEL/AML1-positive patients.

Incidence of TEL/AML1 Fusion in Children With Relapsed Acute Lymphoblastic Leukemia

The TEL/AML1 fusion associated with t(12;21)(p13;q22) is the most common gene rearrangement in childhood leukemia, occurring in approximately 25% of pediatric acute lymphoblastic leukemia (ALL), and is associated with a favorable prognosis. For example, a cohort of pediatric patients with ALL retrospectively analyzed for theTEL/AML1 fusion treated on Dana-Farber Cancer Institute (DFCI) ALL Consortium protocols between 1980 to 1991 demonstrated a 100% relapse-free survival in TEL/AML1-positive patients with a median of 8.3 years of follow-up. However, two recent studies analyzing pediatric patients with relapsed ALL have reported the same incidence of the TEL/AML1 rearrangement as in patients with newly diagnosed ALL, suggesting that TEL/AML1 positivity is not a favorable prognostic indicator. To clarify this apparent discrepancy, 48 pediatric patients treated on Dana-Farber Cancer Institute (DFCI) protocols with ALL at first or second relapse were tested forTEL/AML1 using reverse transcriptase-polymerase chain reaction (RT-PCR). The TEL/AML1 fusion was identified in only 1 of 32 analyzable relapsed ALL patients, in concordance with our previous reports of improved disease-free survival in TEL/AML1-positive patients. The low frequency of TEL/AML1-positive patients at relapse is significantly different than that reported in other studies. Although there are several potential explanations for the observed differences in TEL/AML1-positive patients at relapse, it is plausible that relapse-free survival in TEL/AML1-positive patients may be changed with different therapeutic approaches. Taken together, these results support the need for prospective analysis of prognosis in TEL/AML1-positive patients.

Cytogenetically unrelated clones in therapy-related myelodysplasia and acute myeloid leukemia: experience from the Copenhagen series updated to 180 consecutive cases

During the period from 1995 to 1997, we studied 19 new cases of therapy-related myelodysplasia (t-MDS) and acute myeloid leukemia (t-AML), extending our series to 180 consecutive cases: 123 patients with t-MDS and 57 patients with t-AML. Cytogenetically unrelated clones were observed in 13 patients: 11 patients with two unrelated clones, one patient with three unrelated clones, and one patient with four unrelated clones. Twelve cases of unrelated clones presented as t-MDS, whereas only one case presented as overt t-AML. Partial or complete deletions of the long arms or monosomy for chromosome 5 or chromosome 7, which are characteristic of t-MDS and t-AML, were observed in both unrelated clones in four patients and in one unrelated clone only in six patients, whereas three patients showed aberrations in both clones that were uncharacteristic of t-MDS or t-AML. Three different interpretations of the origin and significance of cytogenetically unrelated clones in t-MDS and t-AML are presented, although the disease is still considered to be monoclonal. First, patients with different defects of the long arm of chromosome 5 or chromosome 7 in two unrelated clones often seem to have acquired these aberrations as independent events. For this reason, it is possible that they may play an important role in leukemic transformation, for instance, by activating or potentiating the effect of a genetic change that is present in all cells but not disclosed as a visible chromosome abnormality. In cases with involvement of other chromosomes, unrelated clones sometimes develop by cytogenetic change in only a subclone of cells, indicating that they play a role only in tumor progression. Finally, unrelated clones in t-MDS and t-AML may represent two different monoclonal diseases: the primary tumor and t-MDS. This view is supported by the significant excess of unrelated clones observed in t-MDS following multiple myeloma (4 in 13 cases) compared with other diseases (9 in 167 cases; P = 0.02), and by results from a case with a balanced translocation that is highly characteristic of non-Hodgkin's lymphoma in one clone and a t-MDS-associated deletion of the long arm of chromosome 5 in another.

Selection of a subpopulation with fewer DNA topoisomerase II alpha gene copies in a doxorubicin-resistant cell line panel

A panel of doxorubicin-resistant sublines of the human small-cell lung carcinoma cell line GLC4 displays decreasing DNA topoisomerase II alpha (TopoII alpha) mRNA levels with increasing resistance. In the present study we describe how this decrease may be regulated. No significant differences in TopoII alpha mRNA stability or gene arrangement were found, using mRNA slot-blotting and Southern blotting, in the most resistant cell line compared with the parental cell line. To investigate if TopoII alpha gene copy loss contributed to the mRNA decrease, fluorescence in situ hybridisation using a TopoII alpha-specific probe was performed. During doxorubicin resistance development, the composition of the population in each cell line shifted with increasing resistance, from a population in which most cells contain three TopoII alpha gene copies (GLC4) to a population in which most cells contain only two copies. A partial revertant of the most resistant cell line displayed a shift back to the original situation. We conclude that the TopoII alpha gene copy number decrease per cell line is in good agreement with the decreased TopoII alpha mRNA and protein levels, and TopoII activity levels in these cell lines which were described previously.

Therapy-related myeloid leukemia

One of the most serious possible consequences of cancer therapy is the development of a second cancer, especially leukemia. Several distinct subsets of therapy-related leukemia can be distinguished currently. These include classic therapy-related myeloid leukemia, leukemia that follows treatment with agents that inhibit topoisomerase II, acute lymphoblastic leukemia, and leukemias with 21q22 rearrangements or inv(16) or t(15;17). These types of leukemia are discussed in detail in this article.

Abnormalities of 3q21 and 3q26 in myeloid malignancy: a United Kingdom Cancer Cytogenetic Group study

Cytogenetic and clinical details are presented for 66 patients with myeloid malignancy and chromosome abnormalities of 3q21 and/or 3q26 (3qabns). Bone marrow and/or peripheral blood morphology was assessed for 52 cases. 3qabns in Philadelphia negative (Ph-ve) and positive (Ph+ve) cases were inv(3)(q21q26), (21 Ph-ve, 6 Ph+ve); t(3;3)(q21;q26) (nine Ph-ve, four Ph+ve); and t(3;21)(q26;q22) (four Ph-ve, six Ph+ve). Ph-ve cases also had t(1;3)(p36;q21) (three cases), and t(3;5)(q21;q31)/(q21;q35)/(q26;q21) (five cases aged < 40 years). Three cases, aged < 30 years, had t(3;12)(q26;p13) which defines a new 3qabn subgroup. Monosomy 7 and/or 5q- accompanied inv(3) or t(3;3) in 17/30 cases. All cases had a myeloid malignancy (predominantly AML M1, M4 or M7), frequent trilineage myelodysplasia, and markedly abnormal megakaryopoiesis with micromegakaryocytes (< 30 microns). Thrombocytosis occurred in two cases only. Most Ph+ve cases were in myeloid blast crisis and in Ph+ve cases alone, micro-megakaryocytes were uniquely small (10 microns) in 7/11 cases. There were equal numbers of males and females. Seven secondary leukaemias were found in Ph-ve cases with inv(3), t(3;3), t(3;21), t(1;3) or del(3)(q21). Three cases with t(3;21) (one Ph+ve) were de novo AML or had de novo aplastic anaemia. Survival was rarely greater than 12 months from detection of the 3qabn.