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Leukemias bearing CRLF2 and JAK2 gene alterations are characterized by aberrant JAK/STAT signaling and poor prognosis. The HDAC inhibitor givinostat/ITF2357 has been shown to exert anti-neoplastic activity against both systemic juvenile idiopathic arthritis and myeloproliferative neoplasms through inhibition of the JAK/STAT pathway. These findings led us to hypothesize that givinostat might also act against CRLF2-rearranged BCP-ALL, which lack effective therapies. Here, we found that givinostat inhibited proliferation and induced apoptosis of BCP-ALL CRLF2- rearranged cell lines, positive for exon 16 JAK2 mutations. Likewise, givinostat killed primary cells, but not their normal hematopoietic counterparts, from patients carrying CRLF2 rearrangements. At low doses, givinostat downregulated the expression of genes belonging to the JAK/STAT pathway and inhibited STAT5 phosphorylation. In vivo , givinostat significantly reduced engraftment of human blasts in patient-derived xenograft models of CRLF2-positive BCP-ALL. Importantly, givinostat killed ruxolitinib-resistant cells and potentiated the effect of current chemotherapy. Thus, givinostat in combination with conventional chemotherapy may represent an effective therapeutic option for these difficult–to-treat subsets of ALL. Lastly, the selective killing of cancer cells by givinostat may allow the design of reduced intensity regimens in CRLF2-rearranged Down syndrome-associated BCP-ALL patients with an overall benefit in terms of both toxicity and related complications.

Cell states in hematopoiesis are controlled by master regulators and by complex circuits of a growing family of RNA species impacting cell phenotype maintenance and plasticity. Circular RNAs (circRNAs) are rapidly gaining the status of particularly stable transcriptome members with distinctive qualities. RNA-seq identified thousands of circRNAs with developmental stage- and tissue-specific expression corroborating earlier suggestions that circular isoforms are a natural feature of the cell expression program. CircRNAs are abundantly expressed also in the hematopoietic compartment. There are a number of studies on circRNAs in blood cells, a specific overview is however lacking. In this review we first present current insight in circRNA biogenesis discussing the relevance for hematopoiesis of the highly interleaved processes of splicing and circRNA biogenesis. Regarding molecular functions circRNAs modulate host gene expression, but also compete for binding of microRNAs, RNA-binding proteins or translation initiation and participate in regulatory circuits. We examine circRNA expression in the hematopoietic compartment and in hematologic malignancies and review the recent breakthrough study that identified pathogenic circRNAs derived from leukemia fusion genes. CircRNA high and regulated expression in blood cell types indicate that further studies are warranted to inform the position of these regulators in normal and malignant hematopoiesis.

The serine/threonine kinase AMP-activated protein kinase (AMPK) and its downstream effectors, including endothelial nitric oxide synthase and BCL-2, are hyperactivated in B-cell precursor-acute lymphoblastic leukemia (BCP-ALL) cells with MLL gene rearrangements. We investigated the role of activated AMPK in supporting leukemic cell survival and evaluated AMPK as a potential drug target. Exposure of leukemic cells to the commercial AMPK inhibitor compound C resulted in massive apoptosis only in cells with MLL gene rearrangements. These results were confirmed by targeting AMPK with specific short hairpin RNAs. Compound C-induced apoptosis was associated with mitochondrial membrane depolarization, reactive oxygen species production, cytochrome c release and caspases cleavage, indicating intrinsic apoptosis pathway activation. Treatment with low concentrations of compound C resulted in a strong antileukemic activity, together with cytochrome c release and cleavage of caspases and poly(ADP-ribose) polymerase, also in MLL-rearranged primary BCP-ALL samples. Moreover, AMPK inhibition in MLL-rearranged cell lines synergistically enhanced the antiproliferative effects of vincristine, daunorubicin, cytarabine, dexamethasone and L -asparaginase in most of the evaluated conditions. Taken together, these results indicate that the activation of the AMPK pathway directly contributes to the survival of MLL-rearranged BCP-ALL cells and AMPK inhibitors could represent a new therapeutic strategy for this high-risk leukemia.

Chromosomal rearrangements of the human MLL gene are associated with high-risk pediatric, adult and therapy-associated acute leukemias. These patients need to be identified, treated appropriately and minimal residual disease was monitored by quantitative PCR techniques. Genomic DNA was isolated from individual acute leukemia patients to identify and characterize chromosomal rearrangements involving the human MLL gene. A total of 760 MLL -rearranged biopsy samples obtained from 384 pediatric and 376 adult leukemia patients were characterized at the molecular level. The distribution of MLL breakpoints for clinical subtypes (acute lymphoblastic leukemia, acute myeloid leukemia, pediatric and adult) and fused translocation partner genes (TPGs) will be presented, including novel MLL fusion genes. Combined data of our study and recently published data revealed 104 different MLL rearrangements of which 64 TPGs are now characterized on the molecular level. Nine TPGs seem to be predominantly involved in genetic recombinations of MLL : AFF1/AF4 , MLLT3/AF9 , MLLT1/ENL , MLLT10/AF10 , MLLT4/AF6 , ELL , EPS15/AF1P , MLLT6/AF17 and SEPT6 , respectively. Moreover, we describe for the first time the genetic network of reciprocal MLL gene fusions deriving from complex rearrangements.

Pediatric B-cell precursor acute lymphoblastic leukemia (BCP-ALL) has achieved an 80% cure rate as a result of a risk-adapted therapy largely based on minimal residual disease (MRD) monitoring. However, relapse is still the most frequent adverse event, occurring mainly in the patients with intermediate MRD levels (intermediate risk, IR), emphasizing the need for new prognostic markers. We analyzed the prognostic impact of cytokine receptor-like factor 2 ( CRLF2 ) over-expression and P2RY8-CRLF2 fusion in 464 BCP-ALL patients (not affected by Down syndrome and BCR-ABL negative) enrolled in the AIEOP-BFM ALL2000 study in Italy. In 22/464 (4.7%) samples, RQ-PCR showed CRLF2 over-expression (⩾20 times higher than the overall median). P2RY8-CRLF2 fusion was detected in 22/365 (6%) cases, with 10/22 cases also showing CRLF2 over-expression. P2RY8-CRLF2 fusion was the most relevant prognostic factor independent of CRLF2 over-expression with a threefold increase in risk of relapse. Significantly, the cumulative incidence of relapse of the P2RY8-CRLF2+ patients in the IR group was high (61.1%±12.9 vs 17.6%±2.6, P <0.0001), similar to high-risk patients in AIEOP-BFM ALL2000 study. These results were confirmed in a cohort of patients treated in Germany. In conclusion, P2RY8-CRLF2 identifies a subset of BCP-ALL patients currently stratified as IR that could be considered for treatment intensification.

One of the biggest challenges in tumour research is the possibility to reprogram cancer cells towards less aggressive phenotypes. In this study, we reprogrammed primary Glioblastoma multiforme (GBM)-derived cells towards a more differentiated and less oncogenic phenotype by activating the Wnt pathway in a hypoxic microenvironment. Hypoxia usually correlates with malignant behaviours in cancer cells, but it has been recently involved, together with Wnt signalling, in the differentiation of embryonic and neural stem cells. Here, we demonstrate that treatment with Wnt ligands, or overexpression of β -catenin, mediate neuronal differentiation and halt proliferation in primary GBM cells. An hypoxic environment cooperates with Wnt-induced differentiation, in line with our finding that hypoxia inducible factor-1 α (HIF-1 α ) is instrumental and required to sustain the expression of β -catenin transcriptional partners TCF-1 and LEF-1. In addition, we also found that Wnt-induced GBM cell differentiation inhibits Notch signalling, and thus gain of Wnt and loss of Notch cooperate in the activation of a pro-neuronal differentiation program. Intriguingly, the GBM sub-population enriched of cancer stem cells (CD133 + fraction) is the primary target of the pro-differentiating effects mediated by the crosstalk between HIF-1 α , Wnt, and Notch signalling. By using zebrafish transgenics and mutants as model systems to visualize and manipulate in vivo the Wnt pathway, we confirm that Wnt pathway activation is able to promote neuronal differentiation and inhibit Notch signalling of primary human GBM cells also in this in vivo set-up. In conclusion, these findings shed light on an unsuspected crosstalk between hypoxia, Wnt and Notch signalling in GBM, and suggest the potential to manipulate these microenvironmental signals to blunt GBM malignancy.