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pro-B cells from healthy donors (Zwollo et al, 1997; Sekine et al, 2007).In conclusion, our data show an association between PAX5 aberrant splicing and BCP-ALL. We also provide, for the first time, evidence of imbalance between the full-length and PAX5D2 isoforms as a common event in BCP-ALL. Given the well-documented role of this gene in the development of BCP, the cumulative effect of point mutations and post-transcriptional regulation of alternative splicing of PAX5 pre-mRNA may suggest its primary pathogenic role in BCP-ALL of both children and adults.

Chronic lymphocytic leukemia (CLL) is an incurable B-cell neoplasm characterized by highly variable clinical outcomes. In recent years, genomic and molecular studies revealed a remarkable heterogeneity in CLL, which mirrored the clinical diversity of this disease. These studies profoundly enhanced our understanding of leukemia cell biology and led to the identification of new biomarkers with potential prognostic and therapeutic significance. Accumulating evidence indicates a key role of deregulated NOTCH1 signaling and NOTCH1 mutations in CLL. This review highlights recent discoveries that improve our understanding of the pathophysiological NOTCH1 signaling in CLL and the clinical impact of NOTCH1 mutations in retrospective and prospective trials. In addition, we discuss the rationale for a therapeutic strategy aiming at inhibiting NOTCH1 signaling in CLL, along with an overview on the currently available NOTCH1-directed approaches.

Notch1 signaling is involved in regulatory T (Treg)-cell differentiation. We previously demonstrated that, when cocultured with CD3 + cells, mesenchymal stem cells (MSCs) induced a T-cell population with a regulatory phenotype. Here, we investigated the molecular mechanism underlying MSC induction of human Treg cells. We show that the Notch1 pathway is activated in CD4can be recruited by MSCs from CD4 + T cells either indirectly, by means of tolerogenic DCs [3,4], or directly by MSC T-cell interactions requiring cell contact [4,5] and soluble factors such as prostaglandin E2, IL-6, IL-10, indoleamine 2.3 dioxygenase (IDO), transforming growth factor (TGF-β1) [3,4,6], and heme oxygenase-1 [7]. In vivo and in vitro studies indicated that Treg-cell induction from conventional CD4 + T cells is important in MSCs-mediated immunomodulation [4,8,9]. * These authors contributed equally to this work. Results and discussionMSC/CD4 + cocultures significantly increased the percentage of CD4 + CD25 high (5.28 ± 0.44% versus 1.65 ± 0.36% p < 0.001), CD4 + FOXP3 + (9.16 ± 3.09% versus 3.6 ± 0.95% p < 0.05), CD25 + FOXP3 + (7.49 ± 2.6% versus 2.16 ± 0.0775% p < 0.001), and CD4 + CD25 high GITR + cells (34.01 ± 5.2% versus 11.5 ± 4.5% p < 0.05) compared with CD4 + control cells (Supporting Information Fig. 1). FOXP3 mRNA expression was increased 3.8 ± 0.92-fold (p < 0.01). CD4 + CD25 + -enriched cells significantly reduced CD4 + CD25 − cell proliferation by up to 83 ± 18%.As MSC/CD4 + cells cocultures induced a Treg-cell population with suppressive capacity we then investigated whether the Notch1 pathway was involved in the induction of Treg cells by MSCs. MSCs expressed the Notch1 ligands Jagged1, Jagged2, and DLL 1,3-4 mRNAs, with Jagged1 being prevalent (Fig. 1A). Western blot analysis confirmed Jagged1 expression (Fig. 1B and Supporting Information Fig. 4) After a 4-day CD4 + cell coculture with MSCs we analyzed whether Notch1 signaling was activated by assessing expression of Notch1, its downstream target HES1, and the negative regulator FBW7. Compared with control CD4 + cells, Notch1 and HES1-mRNA expression increased 2.07 ± 0.94-and 4.65 ± 2.7-fold, while FBW7 decreased by up to 0.5 ± 0.21-fold (Fig. 1C). Western blot analysis revealed significant over-expression of the Notch1 intracellular (IC) domain and the transmembrane/cytoplasmic portion (Fig. 1E). These data clearly demonstrated the Notch1 pathway was activated in CD4 + cells that were cocultured with MSCs and excluded potential autocrine Notch signaling in CD4 + cells that was able to induce Treg cells.After CD4 + cell-MSC cocultures, iTreg cells were purified by CD25 cell enrichment. Compared with CD25 negative cells (nonTreg cells), the Notch1 signaling was upregulated in the iTreg cells, the FOXP3 mRNA expression was doubled, Notch1 and HES1 were upregulated, and FBW7 was significantly downregulated, suggesting the MSC effects are specific to Treg cells (Fig. 1D).In order to assess the Notch1 signaling contribution to MSCsrelated Treg-cell induction, we used GS...