Overview on Aneuploidy in Childhood B-Cell Acute Lymphoblastic Leukemia

Recent years have brought significant progress in the treatment of B-cell acute lymphoblastic leukemia (ALL). This was influenced by both the improved schemes of conventionally used therapy, as well as the development of new forms of treatment. As a consequence, 5-year survival rates have increased and now exceed 90% in pediatric patients. For this reason, it would seem that everything has already been explored in the context of ALL. However, delving into its pathogenesis at the molecular level shows that there are many variations that still need to be analyzed in more detail. One of them is aneuploidy, which is among the most common genetic changes in B-cell ALL. It includes both hyperdiploidy and hypodiploidy. Knowledge of the genetic background is important already at the time of diagnosis, because the first of these forms of aneuploidy is characterized by a good prognosis, in contrast to the second, which is in favor of an unfavorable course. In our work, we will focus on summarizing the current state of knowledge on aneuploidy, along with an indication of all the consequences that may be correlated with it in the context of the treatment of patients with B-cell ALL.

The poor prognosis of low hypodiploidy in adults with B-cell precursor acute lymphoblastic leukaemia is restricted to older adults and elderly patients

The prognostic significance of low-hypodiploidy has not been extensively evaluated in minimal residual disease (MRD)-oriented protocols for adult acute lymphoblastic leukaemia (ALL). We analysed the outcome of hypodiploid adult ALL patients treated within Programa Español de Tratamientos en Hematología (PETHEMA) protocols. The 5-year cumulative incidence of relapse (CIR) of low-hypodiploid B-cell precursor (BCP)-ALL was significantly higher than that of high-hypodiploids (52% vs. 12%, P = 0.013). Low-hypodiploid BCP-ALL patients aged ≤35 years showed superior survival (71% vs. 21%, P = 0.026) and lower 5-year CIR (17% vs. 66%, P = 0.090) than low-hypodiploids aged >35 years. Older adults and elderly low-hypodiploid BCP-ALL patients show dismal prognosis although achieving an end-induction good MRD response.

Genetic and epigenetic characterization of hypodiploid acute lymphoblastic leukemia

Purpose

To investigate the genetic and epigenetic landscape of hypodiploid (<45 chromosomes) acute lymphoblastic leukemia (ALL).

Methods

Single nucleotide polymorphism array, whole exome sequencing, RNA sequencing, and methylation array analyses were performed on eleven hypodiploid ALL cases.

Results

In line with previous studies, mutations in IKZF3 and FLT3 were detected in near-haploid (25–30 chromosomes) cases. Low hypodiploidy (31–39 chromosomes) was associated with somatic TP53 mutations. Notably, mutations of this gene were also found in 3/3 high hypodiploid (40–44 chromosomes) cases, suggesting that the mutational patterns are similar in low hypodiploid and high hypodiploid ALL. The high hypodiploid ALLs frequently displayed substantial cell-to-cell variability in chromosomal content, indicative of chromosomal instability; a rare phenomenon in ALL. Gene expression analysis showed that genes on heterodisomic chromosomes were more highly expressed in hypodiploid cases. Cases clustered according to hypodiploid subtype in the unsupervised methylation analyses, but there was no association between chromosomal copy number and methylation levels. A comparison between samples obtained at diagnosis and relapse showed that the relapse did not arise from the major diagnostic clone in 3/4 cases.

Conclusion

Taken together, our data support the conclusion that near-haploid and low hypodiploid ALL are different with regard to mutational profiles and also suggest that ALL cases with high hypodiploidy may harbor chromosomal instability.

Prognostic impact of pretreatment cytogenetics in adult Philadelphia chromosome-negative acute lymphoblastic leukemia in the era of minimal residual disease

BACKGROUND

The introduction of novel prognostic factors such as minimal residual disease (MRD) and genomic profiling has led to the reevaluation of the role of cytogenetics and other conventional factors in risk stratification for acute lymphoblastic leukemia (ALL).

METHODS

This study assessed the impact of baseline cytogenetics on the outcomes of 428 adult patients with Philadelphia chromosome-negative ALL who were receiving frontline chemotherapy. Three hundred thirty patients (77%) were treated with hyperfractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone-based regimens, and 98 (23%) were treated with the augmented Berlin-Frankfurt-Munster regimen.

RESULTS

The median age was 40 years (range, 13-86 years). One hundred eighty-six patients (43%) had diploid cytogenetics, 32 (7%) had complex cytogenetics (defined as ≥ 5 chromosomal abnormalities), 27 (6%) had low hypodiploidy/near-triploidy (Ho-Tr), 24 (6%) had high hyperdiploidy, and 24 (6%) had a mixed-lineage leukemia (MLL) rearrangement. Patients with an MLL rearrangement, Ho-Tr, or a complex karyotype had significantly worse relapse-free survival (RFS) and overall survival (OS) than the diploid group. According to a multivariate analysis including all the baseline characteristics and MRD status, Ho-Tr and a complex karyotype were independent predictive factors for worse RFS and OS. Furthermore, survival among all cytogenetic groups was similar, regardless of the treatment received.

CONCLUSIONS

A complex karyotype and Ho-Tr are adverse prognostic factors for adults with ALL independently of the MRD status. These findings suggest that pretreatment cytogenetics remain a valuable prognostic tool in this population. Cancer 2017;123:459-467. © 2016 American Cancer Society.

Mixed Phenotype Acute Leukemia with Low Hypodiploidy in a Pediatric Patient

We describe the case of a 16 year-old female with mixed phenotype acute leukemia B/myeloid, NOS (formerly biphenotypic leukemia) with masked hypodiploidy and somatic TP53 and CDKN2A/B deletions. She achieved morphologic remission with lymphoid-directed multi-agent chemotherapy, but experienced an early medullary relapse 11 months from initial diagnosis. Her case details the unusual finding of hypodiploidy in a patient with ambiguous lineage leukemia and highlights the complexity of therapy selection for these high-risk patients.