New insights into the clinical characteristics of SETD2-mutated acute myeloid leukaemia.

As reported, SETD2 is recurrently mutated in acute myeloid leukaemia (AML), but knowledge about the specifics is limited. We enrolled 530 consecutive newly diagnosed AML patients in our study, and we analysed the distribution pattern and prognostic role of SETD2 mutation in AML. SETD2 mutation was found to affect 6.3% of AML patients, and it frequently co-occurred with IDH2, NRAS and CEBPA mutations. SETD2-mutated patients saw excellent therapeutic responses but failed to gain better survival time than other patients. This could be because of the high recurrence and mortality in SETD2-mutated patients who have additional mutations, such as NRAS mutation.

Current views on the genetic landscape and management of variant acute promyelocytic leukemia.

Acute promyelocytic leukemia (APL) is characterized by the accumulation of promyelocytes in bone marrow. More than 95% of patients with this disease belong to typical APL, which express PML-RARA and are sensitive to differentiation induction therapy containing all-trans retinoic acid (ATRA) and arsenic trioxide (ATO), and they exhibit an excellent clinical outcome. Compared to typical APL, variant APL showed quite different aspects, and how to recognize, diagnose, and treat variant APL remained still challenged at present. Herein, we drew the genetic landscape of variant APL according to recent progresses, then discussed how they contributed to generate APL, and further shared our clinical experiences about variant APL treatment. In practice, when APL phenotype was exhibited but PML-RARA and t(15;17) were negative, variant APL needed to be considered, and fusion gene screen as well as RNA-sequencing should be displayed for making the diagnosis as soon as possible. Strikingly, we found that besides of RARA rearrangements, RARB or RARG rearrangements also generated the phenotype of APL. In addition, some MLL rearrangements, NPM1 rearrangements or others could also drove variant APL in absence of RARA/RARB/RARG rearrangements. These results indicated that one great heterogeneity existed in the genetics of variant APL. Among them, only NPM1-RARA, NUMA-RARA, FIP1L1-RARA, IRF2BP2-RARA, and TFG-RARA have been demonstrated to be sensitive to ATRA, so combined chemotherapy rather than differentiation induction therapy was the standard care for variant APL and these patients would benefit from the quick switch between them. If ATRA-sensitive RARA rearrangement was identified, ATRA could be added back for re-induction of differentiation. Through this review, we hoped to provide one integrated view on the genetic landscape of variant APL and helped to remove the barriers for managing this type of disease.

Recurrent SETD2 mutation in NPM1-mutated acute myeloid leukemia.

SETD2 is the only methyltransferase for H3K36me3, and our previous study has firstly demonstrated that it functioned as one tumor suppressor in hematopoiesis. Consistent with it, SETD2 mutation, which led to its loss of function, was identified in AML. However, the distribution and function of SETD2 mutation in AML remained largely unknown. Herein, we integrated SETD2-mutated AML cases from our center and literature reports, and found that NPM1 mutation was the most common concomitant genetic alteration with SETD2 mutation in AML, with its frequency even higher than MLL rearrangement and AML1-ETO. Though this result indicated the cooperation of SETD2 and NPM1 mutations in leukemogenesis, our functional study showed that SETD2 was required for the proliferation of NPM1-mutated AML cell line OCI-AML3, but not MLL-rearranged AML cell line THP-1, via maintaining its direct target NPM1 expression, which was just opposite to its role of tumor suppressor. Therefore, we speculated that SETD2 possibly had two different faces in distinct subtypes and stages of AML.

New perspectives in genetics and targeted therapy for blastic plasmacytoid dendritic cell neoplasm.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is one rare but clinically aggressive hematological malignancy, and it is typically characterized by skin lesion and bone marrow involvement. Diagnosis of BPDCN relies on the immunophenotype positive for four of CD4, CD56, CD123, TCL1 and BDCA-2, and commonly without the expression of MPO, cytoplasmic CD3, CD13, CD64, cytoplasmic CD79a, CD19 and CD20. Commonly, BPDCN is characterized by high CD123 expression, aberrant NF-κB activation, dependence on TCF4-/BRD4-network, and deregulated cholesterol metabolism. Under conventional therapy, the survival duration is only improved in a small number of BPDCN patients. Therefore, targeted therapy should be developed. Up to now, tagraxofusp is the leading edge and has been approved for BPDCN treatment. However, most of other targeted therapy agents were still not pushed to clinical trials for BPDCN. In this review, we emphatically discuss recent perspectives on BPDCN genetic features and developments of its targeted therapy.

Setd2 deficiency impairs hematopoietic stem cell self-renewal and causes malignant transformation.

The histone H3 lysine 36 methyltransferase SETD2 is frequently mutated in various cancers, including leukemia. However, there has not been any functional model to show the contribution of SETD2 in hematopoiesis or the causal role of SETD2 mutation in tumorigenesis. In this study, using a conditional Setd2 knockout mouse model, we show that Setd2 deficiency skews hematopoietic differentiation and reduces the number of multipotent progenitors; although the number of phenotypic hematopoietic stem cells (HSCs) in Setd2-deleted mice is unchanged, functional assays, including serial BM transplantation, reveal that the self-renewal and competitiveness of HSCs are impaired. Intriguingly, Setd2-deleted HSCs, through a latency period, can acquire abilities to overcome the growth disadvantage and eventually give rise to hematopoietic malignancy characteristic of myelodysplastic syndrome. Gene expression profile of Setd2-deleted hematopoietic stem/progenitor cells (HSPCs) partially resembles that of Dnmt3a/Tet2 double knockout HSPCs, showing activation of the erythroid transcription factor Klf1-related pathway, which plays an important role in hematopoietic malignant transformation. Setd2 deficiency also induces DNA replication stress in HSCs, as reflected by an activated E2F gene regulatory network and repressed expression of the ribonucleotide reductase subunit Rrm2b, which results in proliferation and cell cycle abnormalities and genomic instability, allowing accumulation of secondary mutation(s) that synergistically contributes to tumorigenesis. Thus, our results demonstrate that Setd2 is required for HSC self-renewal, and provide evidence supporting the causal role of Setd2 deficiency in tumorigenesis. The underlying mechanism shall advance our understanding of epigenetic regulation of cancer and provide potential new therapeutic targets.

Sensitizing leukemia stem cells to NF-κB inhibitor treatment in vivo by inactivation of both TNF and IL-1 signaling.

We previously reported that autocrine TNF-α (TNF) is responsible for JNK pathway activation in a subset of acute myeloid leukemia (AML) patient samples, providing a survival/proliferation signaling parallel to NF-κB in AML stem cells (LSCs). In this study, we report that most TNF-expressing AML cells (LCs) also express another pro-inflammatory cytokine, IL1ß, which acts in a parallel manner. TNF was produced primarily by LSCs and leukemic progenitors (LPs), whereas IL1ß was mainly produced by partially differentiated leukemic blasts (LBs). IL1ß also stimulates an NF-κB-independent pro-survival and proliferation signal through activation of the JNK pathway. We determined that co-inhibition of signaling stimulated by both TNF and IL1ß synergizes with NF-κB inhibition in eliminating LSCs both ex vivo and in vivo. Our studies show that such treatments are most effective in M4/5 subtypes of AML.

Hematopoietic Stem Cell Activity Is Regulated by Pten Phosphorylation Through a Niche-Dependent Mechanism.

The phosphorylated form of Pten (p-Pten) is highly expressed in >70% of acute myeloid leukemia samples. However, the role of p-Pten in normal and abnormal hematopoiesis has not been studied. We found that Pten protein levels are comparable among long-term (LT) hematopoietic stem cells (HSCs), short-term (ST) HSCs, and multipotent progenitors (MPPs); however, the levels of p-Pten are elevated during the HSC-to-MPP transition. To study whether p-Pten is involved in regulating self-renewal and differentiation in HSCs, we compared the effects of overexpression of p-Pten and nonphosphorylated Pten (non-p-Pten) on the hematopoietic reconstitutive capacity (HRC) of HSCs. We found that overexpression of non-p-Pten enhances the LT-HRC of HSCs, whereas overexpression of p-Pten promotes myeloid differentiation and compromises the LT-HRC of HSCs. Such phosphorylation-regulated Pten functioning is mediated by repressing the cell:cell contact-induced activation of Fak/p38 signaling independent of Pten's lipid phosphatase activity because both p-Pten and non-p-Pten have comparable activity in repressing PI3K/Akt signaling. Our studies suggest that, in addition to repressing PI3K/Akt/mTor signaling, non-p-Pten maintains HSCs in bone marrow niches via a cell-contact inhibitory mechanism by inhibiting Fak/p38 signaling-mediated proliferation and differentiation. In contrast, p-Pten promotes the proliferation and differentiation of HSCs by enhancing the cell contact-dependent activation of Src/Fak/p38 signaling. Stem Cells 2016;34:2130-2144.

Effect of absorption rate on pharmacokinetics of ibuprofen in relation to chiral inversion in humans.

The effect of absorption rate on the pharmacokinetics of ibuprofen enantiomers was investigated in 12 healthy Han Chinese male volunteers following oral administration of immediate-release (IR) and sustained-release (SR) preparations containing racemic ibuprofen (rac-ibuprofen). The area under the curve of the plasma concentration-time curve (AUC; (mean+/-s.d.) values for rac-ibuprofen were 192.90+/-43.47 for the SR preparation and 195.90+/-31.69 microg h mL(-1) for the IR preparation. AUC values for the enantiomers after administration of the SR formulation were 55.38+/-17.79 and 92.51+/-30.68 microg h mL(-1) for R- and S-ibuprofen, respectively, and were 65.94+/-20.06 and 100.81+/-32.28 microg h mL(-1) for R- and S-ibuprofen after administration of the IR preparation. These values did not differ significantly. C(max) values were significantly decreased with the SR preparation: 25.11+/-5.71, 12.24+/-3.79 and 12.38+/-3.55 microg h mL(-1) for rac-, R-, and S-ibuprofen, respectively, after administration of the SR preparation, vs 46.21+/-8.20, 20.82+/-5.90 and 23.46+/-7.30 microg h mL(-1) for rac-, R-, and S-ibuprofen, respectively, after administration of the IR preparation. Mean residence time was significantly increased: 7.01+/-1.29, 5.52+/-1.25 and 7.04+/-1.30 h for rac-, R-, and S-ibuprofen, respectively, after administration of the SR preparation vs 4.34+/-0.89, 3.43+/-0.64 and 4.51+/-0.79 h for rac-, R-, and S-ibuprofen, respectively, after administration of the IR preparation. AUC values for S-ibuprofen were significantly larger than those for R-ibuprofen in both preparations, indicating unidirectional chiral inversion. The S/R ratio of serum concentrations of enantiomers was 1.78-fold higher at 6 h after administration of the SR preparation compared with the IR preparation (P<0.01). These results indicate that ibuprofen undergoes pre-systemic chiral inversion in parallel with a systemic process and that the clinical effects of rac-ibuprofen in humans depend on the absorption rate.