Human acute myeloid leukemia stem cells: evolution of concept

Prognostic analysis according to European LeukemiaNet 2022 risk stratification for elderly patients with acute myeloid leukemia treated with decitabine

OBJECTIVES

This study aimed to evaluate the prognostic significance of the revised European LeukemiaNet (ELN)-2022 risk stratification model for 123 elderly acute myeloid leukemia (AML) patients treated with decitabine chemotherapy.

RESULTS

Based on the ELN-2022 risk stratification, 15 (12.2%), 51 (41.5%), and 57 (46.3%) patients were classified as having favorable, intermediate, and high-risk AML, respectively. In comparison with the ELN-2017 risk stratification, the ELN-2022 risk stratification re-assigned 26 (21.1%) and three (2.4%) patients to the adverse and favorable risk groups, respectively. Survival analysis revealed distinctive overall survival (OS) outcomes among the ELN-2022 risk groups (6-month OS rate: 73.3%, 52.9%, and 47.7% for favorable, intermediate, and adverse risk, respectively; P = 0.101), with a parallel trend observed in the event-free survival (EFS) (6-month EFS rate: 73.3%, 52.9%, and 45.6% for favorable, intermediate, and adverse risk, respectively; P = 0.049). Notably, both OS and EFS in the favorable risk group were significantly superior in comparison to that of the adverse risk group (OS: P = 0.040, EFS: P = 0.030). Although the ELN-2022 C-index (0.559) was greater than the ELN-2017 C-index (0.539), the result was not statistically significant (P = 0.059). Based on the event net reclassification index, we consistently observed significant improvements in the ELN-2022 risk stratification for overall survival (0.21 at 6 months).

CONCLUSION

In conclusion, the revised ELN-2022 risk stratification model may have improved the risk classification of elderly AML patients treated with hypomethylating agents compared to the ELN-2017 risk stratification model.

Effects of tertiary palliative care on the pattern of end-of-life care in patients with hematologic malignancies in Korea

INTRODUCTION

Patients with hematologic malignancies (HMs) often face challenges in accessing palliative care (PC) and receiving quality end-of-life (EOL) care. We examined factors associated with referrals to tertiary PC and the effects of tertiary PC on EOL care in patients with HMs.

METHOD

We included patients with HMs who were admitted to a university-affiliated hospital and died during hospitalization between January 2018 and December 2021. We investigated the receipt of PC consultations, patient characteristics, and EOL care indicators.

RESULTS

Overall, 487 patients were included in the analysis, with 156 (32%) undergoing PC consultation. Sex, residence, disease status, and admission purpose were factors associated with the likelihood of PC consultation, and there has been an increasing trend in the frequency of consultations in recent cases. A higher proportion of patients who received PC completed advance statements and life-sustaining treatment documents. Patients who received PC had lower rates of aggressive EOL care, including chemotherapy and intensive care unit admission, than those who did not receive PC. Notably, PC reduced the number of blood transfusions.

CONCLUSION

Tertiary PC aims to reduce aggressive EOL care through patient-centered goal-of-care discussions. Therefore, there is an imperative need for concerted efforts toward seamless integration of PC.

Pursuing dynamics of minimal residual leukemic subclones in relapsed and refractory acute myeloid leukemia during conventional therapy

BACKGROUND

Acute myeloid leukemia (AML) is characterized by clonal heterogeneity, leading to frequent relapses and drug resistance despite intensive clinical therapy. Although AML's clonal architecture has been addressed in many studies, practical monitoring of dynamic changes in those subclones during relapse and treatment is still understudied.

METHOD

Fifteen longitudinal bone marrow (BM) samples were collected from three relapsed and refractory (R/R) AML patients. Using droplet digital polymerase chain reaction (ddPCR), the frequencies of patient's leukemic variants were assessed in seven cell populations that were isolated from each BM sample based on cellular phenotypes. By quantifying mutant clones at the diagnosis, remission, and relapse stages, the distribution of AML subclones was sequentially monitored.

RESULTS

Minimal residual (MR) leukemic subclones exhibit heterogeneous distribution among BM cell populations, including mature leukocyte populations. During AML progression, these subclones undergo active phenotypic transitions and repopulate into distinct cell population regardless of normal hematopoiesis hierarchic order. Of these, MR subclones in progenitor populations of patient BM predominantly carry MR leukemic properties, leading to more robust expansion and stubborn persistence than those in mature populations. Moreover, a minor subset of MR leukemic subclones could be sustained at an extremely low frequency without clonal expansion during relapse.

CONCLUSIONS

In this study, we observed treatment persistent MR leukemic subclones and their phenotypic changes during the treatment process of R/R AML patients. This underscores the importance of preemptive inhibition of clonal promiscuity in R/R AML, proposing a practical method for monitoring AML MR subclones.

Enhanced Expression of Glycolytic Enzymes and Succinate Dehydrogenase Complex Flavoprotein Subunit A by Mesothelin Promotes Glycolysis and Mitochondrial Respiration in Myeloblasts of Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is an aggressive malignancy characterized by rapid growth and uncontrolled proliferation of undifferentiated myeloid cells. Metabolic reprogramming is commonly observed in the bone marrow of AML patients, as leukemia cells require increased ATP supply to support disease progression. In this study, we examined the potential role of mesothelin as a metabolic modulator in myeloid cells in AML. Mesothelin is a well-known marker of solid tumors that promotes cancer cell proliferation and survival. We initially analyzed alterations in mesothelin expression in the myeloblast subpopulations, defined as SSC-Alow/CD45dim, obtained from the bone marrow of AML patients using flow cytometry. Our results showed overexpression of mesothelin in 34.8% of AML patients. Subsequently, metabolic changes in leukemia cells were evaluated by comparing the oxygen consumption rates (OCR) of bone marrow samples derived from adult AML patients. Notably, a higher OCR was observed in the mesothelin-positive compared to the mesothelin-low and non-expressing groups. Treatment with recombinant human mesothelin protein enhanced OCR and increased the mRNA expression of glycolytic enzymes and mitochondrial complex II in KG1α AML cells. Notably, siRNA targeting mesothelin in KG1α cells led to the reduction of glycolysis-related gene expression but had no effect on the mitochondrial complex gene. The collective results demonstrate that mesothelin induces metabolic changes in leukemia cells, facilitating the acquisition of a rapid supply of ATP for proliferation in AML. Therefore, the targeting of mesothelin presents a potentially promising approach to mitigating the progression of AML through the inhibition of glycolysis and mitochondrial respiration in myeloid cells.

TP53 Mutation in Acute Myeloid Leukemia: An Old Foe Revisited

INTRODUCTION

TP53 is the most commonly mutated gene in human cancers and was the first tumor suppressor gene to be discovered in the history of medical science. Mutations in the TP53 gene occur at various genetic locations and exhibit significant heterogeneity among patients. Mutations occurring primarily within the DNA-binding domain of TP53 result in the loss of the p53 protein's DNA-binding capability. However, a complex phenotypic landscape often combines gain-of-function, dominant negative, or altered specificity features. This complexity poses a significant challenge in developing an effective treatment strategy, which eradicates TP53-mutated cancer clones. This review summarizes the current understanding of TP53 mutations in AML and their implications. TP53 mutation in AML: In patients with acute myeloid leukemia (AML), six hotspot mutations (R175H, G245S, R248Q/W, R249S, R273H/S, and R282W) within the DNA-binding domain are common. TP53 mutations are frequently associated with a complex karyotype and subgroups of therapy-related or secondary AML. The presence of TP53 mutation is considered as a poor prognostic factor. TP53-mutated AML is even classified as a distinct subgroup of AML by itself, as TP53-mutated AML exhibits a significantly distinct landscape in terms of co-mutation and gene expression profiles compared with wildtype (WT)-TP53 AML.

CLINICAL IMPLICATIONS

To better predict the prognosis in cancer patients with different TP53 mutations, several predictive scoring systems have been proposed based on screening experiments, to assess the aggressiveness of TP53-mutated cancer cells. Among those scoring systems, a relative fitness score (RFS) could be applied to AML patients with TP53 mutations in terms of overall survival (OS) and event-free survival (EFS). The current standard treatment, which includes cytotoxic chemotherapy and allogeneic hematopoietic stem cell transplantation, is largely ineffective for patients with TP53-mutated AML. Consequently, most patients with TP53-mutated AML succumb to leukemia within several months, despite active anticancer treatment. Decitabine, a hypomethylating agent, is known to be relatively effective in patients with AML. Numerous trials are ongoing to investigate the effects of novel drugs combined with hypomethylating agents, TP53-targeting agents or immunologic agents.

CONCLUSIONS

Developing an effective treatment strategy for TP53-mutated AML through innovative and multidisciplinary research is an urgent task. Directly targeting mutated TP53 holds promise as an approach to combating TP53-mutated AML, and recent developments in immunologic agents for AML offer hope in this field.

The Role of Cancer Stem Cells and Their Extracellular Vesicles in the Modulation of the Antitumor Immunity

Cancer stem cells (CSCs) are a population of tumor cells that share similar properties to normal stem cells. CSCs are able to promote tumor progression and recurrence due to their resistance to chemotherapy and ability to stimulate angiogenesis and differentiate into non-CSCs. Cancer stem cells can also create a significant immunosuppressive environment around themselves by suppressing the activity of effector immune cells and recruiting cells that support tumor escape from immune response. The immunosuppressive effect of CSCs can be mediated by receptors located on their surface, as well as by secreted molecules, which transfer immunosuppressive signals to the cells of tumor microenvironment. In this article, the ability of CSCs to regulate the antitumor immune response and a contribution of CSC-derived EVs into the avoidance of the immune response are discussed.