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Deregulated cellular energetics is formally incorporated as an emerging hallmark of cancer, however little is known about its processes in myelodysplastic syndromes (MDS). Using transcriptomic data of CD34+ cells from 159 MDS patients and 17 healthy donors, we selected 37 genes involved in cellular energetics and interrogated about its clinical and prognostic functions. Based on the low expression of ACLY, ANPEP, and PANK1, as well as high expression of PKM and SLC25A5, we constructed our Molecular-Based Score (MBS), that efficiently discriminated patients at three risks groups: favourable risk (n = 28; 3-year overall survival (OS): 100%); intermediate (n = 60; 76% [62–93%]) and adverse (n = 71; 35% [17–61%]). Adverse MBS risk was independently associated with inferior OS (HR = 10.1 [95% CI 1.26–81]; P = 0.029) in multivariable analysis using age, gender and the revised international prognostic score system as confounders. Transcriptional signature revealed that Favourable- and intermediate-risk patients presented enriched molecular programs related to mature myeloid progenitors, cell cycle progression, and oxidative phosphorylation, indicating that this cells differs in their origin, metabolic state, and cell cycle regulation, in comparison to the adverse-risk. Our study provides the first evidence that cellular energetics is transcriptionally deregulated in MDS CD34+ cells and establishes a new useful prognostic score based on the expression of five genes. [ABSTRACT FROM AUTHOR]

Simple Summary: In solid tumors, the altered expression of embryonic genes such as the SLIT-ROBO family has been associated with poor prognosis, while little is known about their role in acute myeloid leukemia (AML). Previous studies reported frequent hypermethylation of SLIT2 mediated by the methyltransferase enzyme EZH2 and more recently the PML protein, which are commonly found to be aberrantly expressed in AML. Here, we aim to assess retrospectively the clinical relevance of the SLIT2 gene in acute promyelocytic leukemia, a homogenous subtype of AML. We demonstrated that reduced SLIT2 expression was associated with high leukocyte counts and reduced overall survival in different APL cohorts. STLI2 treatment decreased APL growth, while SLIT2 knockdown accelerated cell cycle progression and proliferation. Finally, reduced expression of SLIT2 in murine APL blasts resulted in fatal leukemia associated with increased leukocyte counts in vivo. These findings demonstrate that SLIT2 can be considered as a prognostic marker in APL, and a potential candidate for clinical studies of a more heterogeneous disease, such as AML. The SLIT-ROBO axis plays an important role in normal stem-cell biology, with possible repercussions on cancer stem cell emergence. Although the Promyelocytic Leukemia (PML) protein can regulate SLIT2 expression in the central nervous system, little is known about SLIT2 in acute promyelocytic leukemia. Hence, we aimed to investigate the levels of SLIT2 in acute promyelocytic leukemia (APL) and assess its biological activity in vitro and in vivo. Our analysis indicated that blasts with SLIT2high transcript levels were associated with cell cycle arrest, while SLIT2low APL blasts displayed a more stem-cell like phenotype. In a retrospective analysis using a cohort of patients treated with all-trans retinoic acid (ATRA) and anthracyclines, high SLIT2 expression was correlated with reduced leukocyte count (p = 0.024), and independently associated with improved overall survival (hazard ratio: 0.94; 95% confidence interval: 0.92–0.97; p < 0.001). Functionally, SLIT2-knockdown in primary APL blasts and cell lines led to increased cell proliferation and resistance to arsenic trioxide induced apoptosis. Finally, in vivo transplant of Slit2-silenced primary APL blasts promoted increased leukocyte count (p = 0.001) and decreased overall survival (p = 0.002) compared with the control. In summary, our data highlight the tumor suppressive function of SLIT2 in APL and its deteriorating effects on disease progression when downregulated. [ABSTRACT FROM AUTHOR]