Early Mortality in Children and Adolescents with Acute Promyelocytic Leukemia: Experience of the Boldrini Children's Center.

INTRODUCTION: Acute promyelocytic leukemia (APL) is currently considered a highly curable disease. However, an early death (ED) remains one of the main causes of APL treatment failure. PATIENTS AND METHODS: In this retrospective study, we aimed to analyze the clinical characteristics of 91 children and adolescents with APL, who were consecutively registered at the (name of institution removed) Children's Center from January 1, 1998 to December 31, 2017. Data were assessed for age, sex, ethnicity, body mass index percentile, initial white blood cell count, peripheral blood blast count, and platelet count, hemoglobin value, partial thromboplastin time, prothrombin time, fibrinogen level, serum creatinine level, APL morphology subtype (classic vs. hypogranular variant M3v), and FLT3 gene mutations. RESULTS: ED occurred in 12 of 91 (13.1%) patients and was mainly related to cerebral thromboembolism. Overall 66% of deaths occurred in the second week after diagnosis. ED was associated with white blood cell ≥10×10 cells/L (odds ratio of 8.44; 95% confidence interval [CI]=1.48-48.26; P=0.0016), initial promyelocytes ≥20×10/L (odds ratio of 9.29; 95% CI=2.45-35.8; P=0.001), morphologic subtype M3v (odds ratio of 3.63; 95% CI=1.04-12.64; P=0.043), and creatinine serum levels >0.7 mg/dL (odds ratio of 6.78; 95% CI=1.83-25.13; P=0.004). In multivariate analyses, ED was associated with initial peripheral promyelocytes ≥20×10 blasts/L and creatinine serum levels >0.7 mg/dL. CONCLUSIONS: EDs were mainly caused by thrombohemorrhagic events and occurred within the second week after diagnosis. High peripheral promyelocytes and creatinine levels were predictors of ED in APL.

Impact of complex NOTCH1 mutations on survival in paediatric T-cell leukaemia.

BACKGROUND: Molecular alterations occur frequently in T-ALL and the potential impact of those abnormalities on outcome is still controversial. The current study aimed to test whether NOTCH1 mutations and additional molecular abnormalities would impact T-ALL outcome in a series of 138 T-ALL paediatric cases. METHODS: T-ALL subtypes, status of SIL-TAL1 fusion, ectopic expression of TLX3, and mutations in FBXW7, KRAS, PTEN and NOTCH1 were assessed as overall survival (OS) and event-free survival (EFS) prognostic factors. OS and EFS were determined using the Kaplan-Meier method and compared using the log-rank test. RESULTS: The frequencies of mutations were 43.5% for NOTCH1, while FBXW7, KRAS and PTEN exhibited frequencies of 19.1%, 9.5% and 9.4%, respectively. In 78.3% of cases, the coexistence of NOTCH1 mutations and other molecular alterations was observed. In multivariate analysis no statistical association was revealed between NOTCH1 mutations and any other variable analyzed. The mean length of the follow-up was 68.4 months and the OS was 50.7%. SIL-TAL1 was identified as an adverse prognostic factor. NOTCH1 mutation status was not associated with outcome, while the presence of NOTCH1 complex mutations (indels) were associated with a longer overall survival (p = 0.031) than point mutations. CONCLUSION: NOTCH1 mutations alone or in combination with FBXW7 did not impact T-ALL prognosis. Nevertheless, complex NOTCH1 mutations appear to have a positive impact on OS and the SIL-TAL1 fusion was validated as a negative prognostic marker in our series of T-ALL.

PTEN posttranslational inactivation and hyperactivation of the PI3K/Akt pathway sustain primary T cell leukemia viability.

Mutations in the phosphatase and tensin homolog (PTEN) gene leading to PTEN protein deletion and subsequent activation of the PI3K/Akt signaling pathway are common in cancer. Here we show that PTEN inactivation in human T cell acute lymphoblastic leukemia (T-ALL) cells is not always synonymous with PTEN gene lesions and diminished protein expression. Samples taken from patients with T-ALL at the time of diagnosis very frequently showed constitutive hyperactivation of the PI3K/Akt pathway. In contrast to immortalized cell lines, most primary T-ALL cells did not harbor PTEN gene alterations, displayed normal PTEN mRNA levels, and expressed higher PTEN protein levels than normal T cell precursors. However, PTEN overexpression was associated with decreased PTEN lipid phosphatase activity, resulting from casein kinase 2 (CK2) overexpression and hyperactivation. In addition, T-ALL cells had constitutively high levels of ROS, which can also downmodulate PTEN activity. Accordingly, both CK2 inhibitors and ROS scavengers restored PTEN activity and impaired PI3K/Akt signaling in T-ALL cells. Strikingly, inhibition of PI3K and/or CK2 promoted T-ALL cell death without affecting normal T cell precursors. Overall, our data indicate that T-ALL cells inactivate PTEN mostly in a nondeletional, posttranslational manner. Pharmacological manipulation of these mechanisms may open new avenues for T-ALL treatment.

Regulation of PTEN by CK2 and Notch1 in primary T-cell acute lymphoblastic leukemia: rationale for combined use of CK2- and gamma-secretase inhibitors.

T-cell acute lymphoblastic leukemia (T-ALL) patients frequently display NOTCH1 activating mutations and Notch can transcriptionally down-regulate the tumor suppressor PTEN. However, it is not clear whether NOTCH1 mutations associate with decreased PTEN expression in primary T-ALL. Here, we compared patients with or without NOTCH1 mutations and report that the former presented higher MYC transcript levels and decreased PTEN mRNA expression. We recently showed that T-ALL cells frequently display CK2-mediated PTEN phosphorylation, resulting in PTEN protein stabilization and concomitant functional inactivation. Accordingly, the T-ALL samples analyzed, irrespectively of their NOTCH1 mutational status, expressed significantly higher PTEN protein levels than normal controls. To evaluate the integrated functional impact of Notch transcriptional and CK2 post-translational inactivation of PTEN, we treated T-ALL cells with both the gamma-secretase inhibitor DAPT and the CK2 inhibitors DRB/TBB. Our data suggest that combined use of gamma-secretase and CK2 inhibitors may have therapeutic potential in T-ALL.