Limengmeng Wang

Association between DNMT3A Mutations and Prognosis of Adults with De Novo Acute Myeloid Leukemia: A Systematic Review and Meta-Analysis

Background DNA methyltransferase 3A (DNMT3A) mutations were considered to be independently associated with unfavorable prognosis in adults with de novo acute myeloid leukemia (AML), however, there are still debates on this topic. Here, we aim to further investigate the association between DNMT3A mutations and prognosis of patients with AML. Methods Eligible studies were identified from several data bases including PubMed, Embase, Web of Science, ClinicalTrials and the Cochrane Library (up to June 2013). The primary endpoint was overall survival (OS), while relapse-free survival (RFS) and event-free survival (EFS) were chosen as secondary endpoints. If possible, we would pool estimate effects (hazard ratio [HR] with 95% confidence interval[CI]) of outcomes in random and fixed effects models respectively. Results That twelve cohort studies with 6377 patients exploring the potential significance of DNMT3A mutations on prognosis were included. Patients with DNMT3A mutations had slightly shorter OS (HR = 1.60; 95% CI, 1.31–1.95; P<0.001), as compared to wild-type carriers. Among the patients younger than 60 years of age, DNMT3A mutations predicted a worse OS (HR = 1.84; 95% CI, 1.36–2.50; P<0.001). In addition, mutant DNMT3A predicted inferior OS (HR = 2.30; 95% CI, 1.78–2.97; P = 0.862) in patients with unfavorable genotype abnormalities. Similar results were also found in some other subgroups. However, no significant prognostic value was found on OS (HR = 1.40; 95% CI, 0.98–1.99; P = 0.798) in the favorable genotype subgroup. Similar results were found on RFS and EFS under different conditions. Conclusions DNMT3A mutations have slightly but significantly poor prognostic impact on OS, RFS and EFS of adults with de novo AML in total population and some specific subgroups.

The role of telomeres and telomerase in hematologic malignancies and hematopoietic stem cell transplantation

Telomeres are specific nucleoprotein structures at the ends of eukaryotic chromosomes. Telomeres and telomere-associated proteins maintain genome stability by protecting the ends of chromosomes from fusion and degradation. In normal somatic cells, the length of the telomeres gradually becomes shortened with cell division. In tumor cells, the shortening of telomeres length is accelerated under the increased proliferation pressure. However, it will be maintained at an extremely short length as the result of activation of telomerase. Significantly shortened telomeres, activation of telomerase, and altered expression of telomere-associated proteins are common features of various hematologic malignancies and are related with progression or chemotherapy resistance in these diseases. In patients who have received hematopoietic stem cell transplantation (HSCT), the telomere length and the telomerase activity of the engrafted donor cells have a significant influence on HSCT outcomes. Transplantation-related factors should be taken into consideration because of their impacts on telomere homeostasis. As activation of telomerase is widespread in tumor cells, it has been employed as a target point in the treatment of neoplastic hematologic disorders. In this review, the characteristics and roles of telomeres and telomerase both in hematologic malignancies and in HSCT will be summarized. The current status of telomerase-targeted therapies utilized in the treatment of hematologic malignancies will also be reviewed.

Mutations in epigenetic regulators are involved in acute lymphoblastic leukemia relapse following allogeneic hematopoietic stem cell transplantation

Although steady improvements to chemotherapeutic treatments has helped cure 80% of childhood acute lymphoblastic leukemia (ALL) cases, chemotherapy has proven to be less effective in treating the majority of adult patients, leaving allogeneic hematopoietic stem cell transplantation (allo-HSCT) as the primary adult treatment option. Nevertheless relapse are the leading cause of death following allo-HSCT. The genetic pathogenesis of relapse following allo-HSCT in Philadelphia chromosome- negative ALL (Ph− ALL) remains unexplored. We performed longitudinal whole-exome sequencing analysis in three adult patients with Ph− B-cell ALL (Ph− B-ALL) on samples collected from diagnosis to relapse after allo-HSCT. Based on these data, we performed target gene sequencing on 23 selected genes in 58 adult patients undergoing allo-HSCT with Ph− B-ALL. Our results revealed a significant enrichment of mutations in epigenetic regulators from relapsed samples, with recurrent somatic mutations in SETD2, CREBBP, KDM6A and NR3C1. The relapsed samples were also enriched in signaling factor mutations, including KRAS, PTPN21, MYC and USP54. Furthermore, we are the first to reveal the clonal evolution patterns during leukemia relapse after allo-HSCT. Cells present in relapsed specimens were genetically related to the diagnosed tumor, these cells therefore arose from either an existing subclone that was not eradicated by allo-HSCT therapy, or from the same progenitor that acquired new mutations. In some cases, however, it is possible that leukemia recurrence following allo-HSCT could result from a secondary malignancy with a distinct set of mutations. We identified novel genetic causes of leukemia relapse after allo-HSCT using the largest generated data set to date from adult patients with Ph− B-ALL.

Mutations in tyrosine kinase and tyrosine phosphatase and their relevance to the target therapy in hematologic malignancies

Protein tyrosine kinases and protein tyrosine phosphatases play pivotal roles in regulation of cellular phosphorylation and signal transduction with opposite functions. Accumulating evidences have uncovered the relevance of genetic alterations in these two family members to hematologic malignancies. This review underlines progress in understanding the pathogenesis of these genetic alterations including mutations and aberrant expression and the evolving protein tyrosine kinases and protein tyrosine phosphatases targeted therapeutic strategies in hematologic neoplasms.

Hydroxychloroquine sensitizes chronic myeloid leukemia cells to Vγ9Vδ2 T cell-mediated lysis independent of autophagy

Hydroxychloroquine (HCQ) is the only autophagy inhibitor in clinical use and it has shown great potential in treating chronic myeloid leukemia (CML). By inhibiting autophagy, HCQ enhances the anti-CML efficiency of chemotherapy. In the present study, we demonstrated that HCQ sensitized CML cells to Vγ9Vδ2 T cell-mediated lysis. HCQ inhibited autophagy in CML cells, but the sensitizing effects of HCQ were autophagy-independent. Since the sensitization was not mimicked by ATG7 knockdown and even occurred in the absence of ATG7. We revealed that in a time-dependent manner HCQ induced the expression of NKG2D ligand ULBP4 on the surface of CML cells. This marks the leukemia cell for recognition by Vγ9Vδ2 T cells. Blocking the interaction of NKG2D with its ligands deleted the sensitizing effects of HCQ. In addition, we showed that HCQ did not affect the synthesis or degradation of ULBP4, but induced the translocation of ULBP4 from the cytoplasm to the cell membrane. Our results uncovered a previously unknown mechanism for HCQ in CML treatment that underlines the ability of HCQ to modulate the immune visibility of CML cells, and pave the way to the development of new combination treatments with HCQ and Vγ9Vδ2 T cells.

mTOR inhibitor rapamycin induce polymorphonuclear myeloid-derived suppressor cells mobilization and function in protecting against acute graft-versus-host disease after bone marrow transplantation

The mammalian target of rapamycin (mTOR) inhibitor rapamycin (RAPA) has been shown to be an effective immunosuppressor in the management of acute graft-versus-host disease (aGVHD) after bone marrow transplantation. Myeloid-derived suppressor cells (MDSCs) also have a protective effect in aGVHD regulation. However, the relationship between RAPA and MDSCs in aGVHD models is unclear. Meanwhile, the effect of RAPA on different subgroups of MDSCs is also less well described. In this study, we demonstrate that in vivo administration of RAPA results in the expansion and functional enhancement of polymorphonuclear MDSCs (PMN-MDSCs) in a murine model of aGVHD. RAPA treatment can enhance the suppressive function of PMN-MDSCs via up-regulation of arginase1 (Arg1) and induced nitric oxide synthase (iNOS) at later time points. Moreover, RAPA can also induce a strong immunosuppressive function in PMN-MDSCs from murine bone marrow in vitro, but has a contrary effect on monocytic MDSCs (M-MDSCs). We found that RAPA-treated PMN-MDSCs can restrain the differentiation of Th1/Th2 cells and promote induction of regulatory T cells in in vitro studies.

Restoration of CCAAT enhancer binding protein α P42 induces myeloid differentiation and overcomes all-trans retinoic acid resistance in human acute promyelocytic leukemia NB4-R1 cells

All-trans retinoic acid (ATRA) is one of the first line agents in differentiation therapy for acute promyelocytic leukemia (APL). However, drug resistance is a major problem influencing the efficacy of ATRA. Identification of mechanisms of ATRA resistance are urgenly needed. In the present study, we found that expression of C/EBPα, an important transcription factor for myeloid differentiation, was significantly suppressed in ATRA resistant APL cell line NB4-R1 compared with ATRA sensitive NB4 cells. Moreover, two forms of C/EBPα were unequally suppressed in NB4-R1 cells. Suppression of the full-length form P42 was more pronounced than the truncated form P30. Inhibition of PI3K/Akt/mTOR pathway was also observed in NB4-R1 cells. Moreover, C/EBPα expression was reduced by PI3K inhibitor LY294002 and mTOR inhibitor RAD001 in NB4 cells, suggesting that inactivation of the PI3K/Akt/mTOR pathway was responsible for C/EBPα suppression in APL cells. We restored C/EBPα P42 and P30 by lentivirus vectors in NB4-R1 cells, respectively, and found C/EBPα P42, but not P30, could increase CD11b, CD14, G-CSFR and GM-CSFR expression, which indicated the occurrence of myeloid differentiation. Further upregulating of CD11b expression and differential morphological changes were found in NB4-R1 cells with restored C/EBPα P42 after ATRA treatment. However, CD11b expression and differential morphological changes could not be induced by ATRA in NB4-R1 cells infected with P30 expressing or control vector. Thus, we inferred that ATRA sensitivity of NB4-R1 cells was enhanced by restoration of C/EBPα P42. In addition, we used histone deacetylase inhibitor trichostatin (TSA) to restore C/EBPα expression in NB4-R1 cells. Similar enhancement of myeloid differentiation and cell growth arrest were detected. Together, the present study demonstrated that suppression of C/EBPα P42 induced by PI3K/Akt/mTOR inhibition impaired the differentiation and ATRA sensitivity of APL cells. Restoring C/EBPα P42 is an attractive approach for differentiation therapy in ATRA resistant APL.