Celeste Calvello

Therapeutically targeting SELF‐reinforcing leukemic niches in acute myeloid leukemia: A worthy endeavor?

A tight relationship between the acute myeloid leukemia (AML) population and the bone marrow (BM) microenvironment has been convincingly established. The AML clone contains leukemic stem cells (LSCs) that compete with normal hematopoietic stem cells (HSCs) for niche occupancy and remodel the niche; whereas, the BM microenvironment might promote AML development and progression not only through hypoxia and homing/adhesion molecules, but also through genetic defects. Although it is still unknown whether the niche influences treatment results or contains any potential target for treatment, this dynamic AML‐niche interaction might be a promising therapeutic objective to significantly improve the AML cure rate. Am. J. Hematol. 91:507–517, 2016.

Detection of TET2 abnormalities by fluorescence in situ hybridization in 41 patients with myelodysplastic syndrome

TET2 haplo-insufficiency occurs through different molecular mechanisms and is promptly revealed by array comparative genomic hybridization, single nucleotide polymorphism (SNP) array, and next-generation sequencing (NGS). Fluorescence in situ hybridization (FISH) can effectively demonstrate TET2 deletions and is often used to validate molecular results. In the present study 41 MDS patients with and without 4q abnormalities were analyzed with a series of bacterial artificial chromosome (BAC) probes spanning the 4q22.3-q25 region. On conventional cytogenetic (CC) studies, a structural defect of the long arm of chromosome 4 (4q) was observed in seven patients. In three, one each with a t(1;4)(p21;q24), an ins(5;4)(q23;q24qter), and a t(4;17)(q31;p13) as the sole chromosomal abnormality, FISH with the RP11-356L5 and RP11-16G16 probes, which cover the TET2 locus, produced one signal only. Unexpectedly, this same result was achieved in 3 of the remaining 34 patients. Thus, a TET2 deletion was observed in a total of six patients (14.6%). TET2 deletion was not correlated with any particular clinical findings or outcome. These findings demonstrate that 1) FISH is an effective and economical method to reveal cryptic abnormalities of band 4q22-q24 resulting in TET2 deletions; 2) in these patients, TET2 deletion is the unifying genetic event; and 3) the different breakpoints within the 4q22-q25 region suggest that deletions are not mediated by repetitive sequences.

Alternative splicing of hTERT: a further mechanism for the control of active hTERT in acute myeloid leukemia

Abstract hTERT component is the key regulator of telomerase. Alternatively spliced variants of hTERT generate different telomerase activity. The goal of the study was to determine the role of different hTERT isoforms in the regulation of telomerase expression in AML patients. Among the 97 studied patients, 45 had a complex karyotype and 52 a normal karyotype. hTERT isoforms expression was determined in bone marrow samples by q-RT-PCR, using SYBR Green I. hTERT expression was lower in AML patients than controls (median 2.5 vs. 10.1, p = .003), though no difference was observed between the complex and normal karyotype (median 3.2 vs. 2.3, p = .37). High trans-dominant negative isoform expression increased the response rate by two. High expression of inactive product (–α – β) was shown to increase the risk of relapse by about three times. In conclusion, our data suggest an intriguing link between the control of hTERT isoforms expression and AML outcome.

‘Real-life’ study of imatinib therapy in chronic phase-chronic myeloid leukemia: A novel retrospective observational longitudinal analysis

Objectives: Imatinib is a cornerstone of treatment of chronic myeloid leukemia. It remains unclear whether transient treatment discontinuation or dose changes affect outcome and this approach has not yet been approved for use outside clinical trials. Methods: We conducted a retrospective single-institution observational study to evaluate factors affecting response in ‘real-life’ clinical practice in 138 chronic myeloid leukemia patients in chronic phase treated with imatinib. We used a novel longitudinal data analytical model, with a generalized estimating equation model, to study BCR–ABL variation according to continuous standard dose, change in dose or discontinuation; BCR–ABL transcript levels were recorded. Treatment history was subdivided into time periods for which treatment was given at constant dosage (total 483 time periods). Molecular and cytogenetic complete response was observed after 154 (32%) and 358 (74%) time periods, respectively. Results: After adjusting for length of time period, no association between dose and cytogenetic complete response rate was observed. There was a significantly lower molecular complete response rate after time periods at a high imatinib dosage. Discussion: This statistical approach can identify individual patient variation in longitudinal data collected over time and suggests that changes in dose or discontinuation of therapy could be considered in patients with appropriate biological characteristics.