Fifteen cases of t(1;19)(q23;p13.3) identified in an Australian series of 122 children and 80 adults with acute lymphoblastic leukemia

Incidence and Prognostic Impact of TCF3-PBX1 Fusion in Childhood Acute Lymphoblastic Leukemia: A Single Centre Experience

Molecular abnormalities in leukemic cells are important determinants of risk stratification in Pediatric acute lymphoblastic leukemia (ALL). TCF3-PBX1 fusion is one of the common aberrations in ALL with doubtful prognostic significance. Therefore, aim of our study is to revisit the clinical characteristics and outcome of this abnormality in children with ALL treated at our institute.Demographic, Clinical and treatment related characteristics of 539 newly diagnosed ALL patients from January 2009 and December 2018, < 18 years of age treated on BFM-95 protocol, was abstracted from the medical records. Clinical characteristics and outcome of children with and without TCF3-PBX1 fusion was compared.Incidence of TCF3-PBX1 fusion was observed in 24/539(4.4%) patients with a median age of 4 years (range 1-17). None of the patients in TCF3-PBX1 group had CNS or testicular disease at presentation. Day -8 prednisolone response and morphological remission at the end of induction was similar in both study groups. 5-year overall and event free survival for those with and without fusion was 75%, 70.1% and 79.5%, 69.5% respectively.The incidence of TCF3-PBX1 fusion in the present study was 4.4% and it does not have an independent prognostic significance.

Hidden Aberrations Diagnosed by Interphase FluorescenceIn SituHybridisation and Spectral Karyotyping in Childhood Acute Lymphoblastic Leukaemia

Acute lymphoblastic leukaemia (ALL) is the most common oncologic disease in childhood, accounting for approximately 25% of all paediatric malignancies. Based on clinical risk criteria and modern laboratory investigations including immunophenotyping, cytogenetics and molecular genetics, patients can be divided into prognostic groups and assigned to risk-adjusted treatment protocols. The karyotype is an independent prognostic indicator and has for some aberrations that are associated with a poor outcome a direct impact on the choice of treatment. Cytogenetic analysis in ALL is often hampered by poor chromosome morphology, few malignant metaphases, undetectable chromosomal rearrangements due to regions of a similar size and banding pattern and sometimes only normal metaphases derived from normal cells are found after cell culture. Structural as well as numerical aberrations may therefore remain undetected using conventional G-banding. The application of modern molecular cytogenetic techniques including a broad set of fluorescence in situ hybridisation (FISH) methods and recent developments in comparative genomic hybridisation to DNA microarrays, together with molecular methods such as Southern blotting and RT-PCR has greatly improved the detection rate of genetic changes in ALL. This review emphasises the value of increasing the resolving power of the cytogenetic investigation by spectral karyotyping (SKY) and interphase FISH in identifying prognostically important and novel chromosomal rearrangements as a complement to conventional banding analysis. The results of investigations performed on cases with ALL have shown that interphase FISH is valuable and in many cases even mandatory for the detection of prognostically important genetic abnormalities and should therefore consistently be employed in the routine cytogenetic investigations in ALL. Likewise, SKY is a valuable tool for the cytogenetic analysis. Thus, the results of several different investigations described in this review revealed that SKY yielded additional information in 97/157 (62%) cases with chromosomal aberrations detected by G-banding, and in 10/66 (15%) cases with normal G-banding.

Clinical features and prognostic implications of TCF3-PBX1 and ETV6-RUNX1 in adult acute lymphoblastic leukemia

BACKGROUND

The t(9;22) and t(4;11) chromosomal translocations, which generate the BCR-ABL and MLL-AF4 fusion genes, define high-risk subtypes of acute lymphoblastic leukemia in adults. However, the prognostic impact of other rarer fusion genes is less well established in adult acute lymphoblastic leukemia than in the childhood form.

DESIGN AND METHODS

In the context of the German Multicenter Therapy Study Group for Adult Acute Lymphoblastic Leukemia (GMALL) we used reverse transcriptase polymerase chain reaction to investigate 441 cases of BCR-ABL- and MLL-AF4-negative B-precursor acute lymphoblastic leukemia for the TCF3-PBX1 (E2A-PBX1) and ETV6-RUNX1 (TEL-AML1) fusion transcripts generated by the t(1;19)(q23;p13.3) and t(12;21)(p13;q22) translocations. Both are well-known molecular alterations in pediatric acute lymphoblastic leukemia in which they have favorable prognostic implications.

RESULTS

We identified 23 adult patients with TCF3-PBX1 and ten with ETV6-RUNX1. In contrast to previous reports we found no significant difference in overall survival between TCF3-PBX1-positive and -negative patients. At 2 years after diagnosis all the ETV6-RUNX1-positive patients were alive and in continuous complete remission, but their long-term outcome was negatively affected by late relapses. TCF3-PBX1-positive patients exhibited a characteristic CD34(-)/CD33(-) and mostly cyIg(+) immunophenotype. ETV6-RUNX1 only occurred in patients under 35 years old and was associated with a significantly lower white blood count.

CONCLUSIONS

In contrast to previous suggestions, adult patients with TCF3-PBX1-positive acute lymphoblastic leukemia do not appear to have a worse outcome than their negative counterparts. ETV6-RUNX1-positive patients had a very favorable performance status during the first few years but their long-term survival was negatively affected by late relapses. Both groups of patients are characterized by distinct clinicobiological features which facilitate their diagnostic identification.

Constitutional chromosome aberrations as pathogenetic events in hematologic malignancies

A predisposition to tumor development is associated with some constitutional chromosomal abnormalities. Investigations of families with an apparent hereditary cancer and constitutional chromosome rearrangements have led to the molecular identification of tumor suppressor genes. Under the somatic mutation theory for the development of cancer, two mutational events are required. The first step may be a constitutional event and the second an acquired genetic mutation. Cytogenetic studies were performed on 5633 bone marrow specimens from patients with hematologic malignancies from a single institution. Fifty cases of constitutional chromosome aberrations were detected. Data collected from the literature and from our series are reviewed and compared with the incidence of specific constitutional chromosome aberrations in the newborn population. Possible mechanisms that may predispose individuals with constitutional chromosome aberrations to the development of a hematologic malignancy are reviewed.

Hypodiploidy of 37 chromosomes in an adult patient with acute lymphoblastic leukemia

We present a 42-year-old man with acute lymphoblastic leukemia and hypodiploidy at diagnosis. Chromosome count was 37, with a mixture of numerical and structural abnormalities. The patient died 9 months post diagnosis, during which time three further cytogenetic tests were performed. The core abnormalities seen upon diagnosis were present at 7 and 9 months after diagnosis, with a duplication of the abnormal hypodiploid karyotype on the last specimen. While considerable imbalances were present as a result of whole chromosome aneuploidy, no region was obviously nullisomic.