Diagnosing and following adult patients with acute myeloid leukaemia in the genomic age

Distinguishing myelofibrosis from polycythemia vera and essential thrombocythemia: The utility of enumerating circulating stem cells with aberrant hMICL expression by flow cytometry

INTRODUCTION

Diagnosing BCR-ABL negative myeloproliferative neoplasms (MPN) may be challenging due to overlapping features and lack of robust discriminatory parameters, especially between essential thrombocythemia (ET) and prefibrotic myelofibrosis (MF). Circulating immature hematopoietic cells are variably present in polycythemia vera (PV), ET, and MF. The C-type lectin hMICL is aberrantly expressed on hematopoietic stem cells in the majority of acute myeloid leukemia patients. However, the hMICL expression in MPN, having varying propensity of leukemic transformation, is unsettled. We hypothesized that enumeration of immature cells by flow cytometry (FCM) could be a discriminatory tool in MPN diagnostics.

METHODS

By FCM, we quantified circulating stem cells with aberrant hMICL expression in 39 MPN patients, 10 age-matched controls, and in leukapheresis products from 10 patients with lymphoproliferative neoplasms. The utility of the FCM assay for discriminating MPN entities was evaluated by applying ROC curve analysis.

RESULTS

While hMICL was absent in control samples, MF patients had significantly more hMICL+ stem cells (median 15.2%) than PV and ET (0.0%, P = .001 and 0.0%, P = .002, respectively). By ROC curve analysis, the presence of hMICL+ stem cells (>0 cells) in peripheral blood reliably discriminates MF from ET and PV with a sensitivity of 80% and a specificity of 97%.

CONCLUSION

Enumeration of circulating hMICL+ stem cells by FCM can discriminate between MPN phenotypes and holds potential for monitoring disease evolution.

Novel Antigen Targets for Immunotherapy of Acute Myeloid Leukemia

Acute myeloid leukemia (AML) was the first malignancy for which immunotherapy, in the form of allogeneic hematopoietic stem cell transplantation (allo-HSCT), was integrated into the standard of care. Allo-HSCT however is an imperfect therapy associated with significant morbidity and mortality while offering only incomplete prevention of AML clinical relapse. These limitations have motivated the search for AML-related antigens that might be used as more specific and effective targets of immunotherapy. While historically such investigations have focused on protein targets expressed uniquely in AML or at significantly higher levels than in normal tissues, this article will review recent discoveries which have identified a novel selection of potential antigen targets for AML immunotherapy, such as non-protein targets including lipids and carbohydrates, neo-antigens created from genetic somatic mutations or altered splicing and post-translational modification of protein targets, together with innovative ways to target overexpressed protein targets presented by cell surface peptide-MHC complexes. These novel antigens represent promising candidates for further development as targets of AML immunotherapy.

Genetic Association of PARP15 Polymorphisms with Clinical Outcome of Acute Myeloid Leukemia in a Korean Population

AIMS

Some members of the poly ADP-ribose polymerase (PARP) protein family have been regarded as targets for the therapeutic inhibition of cancer. Among these PARP genes, poly ADP-ribose polymerase family, member 15 (PARP15) is a candidate gene for cancer development due to its ability to regulate gene transcription and its reported association with apoptosis. The current study investigated the possible association between PARP15 single-nucleotide polymorphisms and the risk of acute myeloid leukemia (AML). In addition, we analyzed the effects of the PARP15 polymorphisms on the clinical phenotypes associated with cytosine arabinose (AraC) chemotherapy in AML patients.

METHODS

Ten PARP15 polymorphisms were genotyped via TaqMan assay in a total of 344 Korean subjects, including 103 AML patients and 241 normal controls. The genetic effects of the polymorphisms on the risk of AML and the clinical phenotypes were analyzed using Statistical Analysis System (SAS) software.

RESULTS

The results from a Cox regression analysis for overall survival revealed that two polymorphisms were associated with increased overall survival and the signal for rs17208928 was retained after correcting for multiple tests (p^corr < 0.05).

CONCLUSIONS

These results suggest the possibility that the PARP15 gene may be a potential therapeutic target in AML patients although much larger scale studies are needed for validation.

Identifying high-risk adult AML patients: epigenetic and genetic risk factors and their implications for therapy

Acute myeloid leukemia (AML) is a heterogeneous disease at molecular level, in response to therapy and prognosis. The molecular landscape of AML is evolving with new technologies revealing complex panorama of genetic abnormalities where genomic instability and aberrations of epigenetic regulators play a key role in pathogenesis. The characterization of AML diversity has led to development of new personalized therapeutic strategies to improve outcome of the patients.

The kinetics of relapse in DEK-NUP214-positive acute myeloid leukemia patients

Preemptive treatment of relapse of acute myeloid leukemia (AML) holds the promise to improve the prognosis of this currently highly lethal condition. Proposed treatment modalities applicable in preemptive cytoreduction (e.g., demethylating agents or standard chemotherapy) differ substantially in interval from administration to antileukemic effect. The t(6;9) balanced translocation, producing the DEK-NUP214 fusion protein, is seen in only 1% of patients with AML. We hypothesized that in these patients, who relapse with a very high frequency, a more detailed knowledge of leukemic relapse growth kinetics would improve the personalized decision-making regarding re-administration of chemotherapy. Based on standardized quantitative PCR data, we therefore delineated the relapse kinetics in a cohort of 27 relapsing DEK-NUP214-positive patients treated in four different European countries. The prerelapse leukemic burden increased with a median doubling time of 13 d (range: 5-51 d, median: 0.71 logs/month, range: 0.18-1.91 logs/month), with FLT3-ITD-positive patients relapsing significantly faster than FLT3-ITD-negative ones (median: 0.9 vs. 0.6 logs/month, Wilcoxon rank sum test, P = 0.041). Peripheral blood and bone marrow were equally useful for minimal residual disease (MRD) detection, and thus, we found that with sampling intervals of 2 months, 94% of relapses would be detected with a median time from MRD detection to hematological relapse of 64 d. In conclusion, this data provide algorithms for handling the rare patients with DEK-NUP214-positive AML allowing for planning of both MRD follow-up and, upon molecular relapse, the timing of cytoreduction or possibly transplant procedures.

Advancing the Minimal Residual Disease Concept in Acute Myeloid Leukemia

The criteria to evaluate response to treatment in acute myeloid leukemia (AML) have changed little in the past 60 years. It is now possible to use higher sensitivity tools to measure residual disease burden in AML. Such minimal or measurable residual disease (MRD) measurements provide a deeper understanding of current patient status and allow stratification for risk of subsequent clinical relapse. Despite these obvious advantages, and after over a decade of laboratory investigation and preclinical validation, MRD measurements are not currently routinely used for clinical decision-making or drug development in non-acute promyelocytic leukemia (non-APL) AML. We review here some potential constraints that may have delayed adoption, including a natural hesitancy of end users, economic impact concerns, misperceptions regarding the meaning of and need for assay sensitivity, the lack of one single MRD solution for all AML patients, and finally the need to involve patients in decision-making based on such correlates. It is our opinion that none of these issues represent insurmountable barriers and our hope is that by providing potential solutions we can help map a path forward to a future where our patients will be offered personalized treatment plans based on the amount of AML they have left remaining to treat.