Nicole D. Vincelette

Emerging understanding of Bcl-2 biology: Implications for neoplastic progression and treatment

Bcl-2, the founding member of a family of apoptotic regulators, was initially identified as the protein product of a gene that is translocated and overexpressed in greater than 85% of follicular lymphomas (FLs). Thirty years later we now understand that anti-apoptotic Bcl-2 family members modulate the intrinsic apoptotic pathway by binding and neutralizing the mitochondrial permeabilizers Bax and Bak as well as a variety of pro-apoptotic proteins, including the cellular stress sensors Bim, Bid, Puma, Bad, Bmf and Noxa. Despite extensive investigation of all of these proteins, important questions remain. For example, how Bax and Bak breach the outer mitochondrial membrane remains poorly understood. Likewise, how the functions of anti-apoptotic Bcl-2 family members such as eponymous Bcl-2 are affected by phosphorylation or cancer-associated mutations has been incompletely defined. Finally, whether Bcl-2 family members can be successfully targeted for therapeutic advantage is only now being investigated in the clinic. Here we review recent advances in understanding Bcl-2 family biology and biochemistry that begin to address these questions.

CHK1 and WEE1 inhibition combine synergistically to enhance therapeutic efficacy in acute myeloid leukemia ex vivo.

Novel combinations targeting new molecular vulnerabilities are needed to improve the outcome of patients with acute myeloid leukemia. We recently identified WEE1 kinase as a novel target in leukemias. To identify genes that are synthetically lethal with WEE1 inhibition, we performed a short interfering RNA screen directed against cell cycle and DNA repair genes during concurrent treatment with the WEE1 inhibitor MK1775. CHK1 and ATR, genes encoding two replication checkpoint kinases, were among the genes whose silencing enhanced the effects of WEE1 inhibition most, whereas CDK2 short interfering RNA antagonized MK1775 effects. Building on this observation, we examined the impact of combining MK1775 with selective small molecule inhibitors of CHK1, ATR and cyclin-dependent kinases. The CHK1 inhibitor MK8776 sensitized acute myeloid leukemia cell lines and primary leukemia specimens to MK1775 ex vivo, whereas smaller effects were observed with the MK1775/MK8776 combination in normal myeloid progenitors. The ATR inhibitor VE-821 likewise enhanced the antiproliferative effects of MK1775, whereas the cyclin-dependent kinase inhibitor roscovitine antagonized MK1775. Further studies showed that MK8776 enhanced MK1775-mediated activation of the ATR/CHK1 pathway in acute leukemia cell lines and ex vivo. These results indicate that combined cell cycle checkpoint interference with MK1775/MK8776 warrants further investigation as a potential treatment for acute myeloid leukemia.

Targeting immune checkpoints in unresectable metastatic cutaneous melanoma: a systematic review and meta‐analysis of anti‐CTLA‐4 and anti‐PD‐1 agents trials

Anti‐cytotoxic T lymphocyte‐associated antigen‐4 (CTLA‐4) and anti‐programmed cell death‐1 (PD‐1) inhibitors have been shown to significantly improve survival in patients with metastatic cutaneous melanoma. However, there was some heterogeneity as well as some variation in the degree of benefit across studies. We reviewed randomized trials and performed a meta‐analysis to determine the efficacy and safety of immune checkpoint inhibitors in comparison with conventional regimens. Eligible studies were limited to randomized controlled trials comparing anti‐CTLA‐4 or anti‐PD‐1 inhibitors to chemotherapy or vaccination treatment in adult patients with unresectable cutaneous metastatic melanoma. Progression‐free survival (PFS) rate at 6 months was 28.5% versus 17.7% (RR: 0.84, 95% CI: 0.76–0.93), overall survival (OS) rate at 1 year was 51.2% versus 38.8% (RR: 0.72, 95% CI: 0.59–0.88), and overall response rate (ORR) at 6 months was 29.6% versus 17.7% (RR: 0.85, 95% CI: 0.76–0.95) favoring immune check point inhibitors over chemotherapies or vaccination. Immune check point inhibitors were associated with more frequent immune‐related adverse events at 13.7% versus 2.4% of treated patients (RR: 6.74, 95% CI: 4.65–9.75). Subgroup analyses demonstrated significant PFS (RR: 0.92 vs. 0.74, P < 0.00001) and ORR (RR: 0.95 vs. 0.76, P = 0.0004) improvement with anti‐PD‐1 treatment compared to anti‐CTLA‐4 when each of them was compared to control treatments. Collectively, these results demonstrate that immune checkpoint inhibitors have superior outcomes compared to conventional chemotherapies or vaccination, and support the results of recent randomized trials that showed superior outcomes with anti‐PD‐1 agents over ipilimumab in unresectable metastatic cutaneous melanoma patients.

Risk of Atrial Fibrillation and Bleeding Diathesis Associated With Ibrutinib Treatment: A Systematic Review and Pooled Analysis of Four Randomized Controlled Trials

Micro‐Abstract The goal of the present study was to precisely assess the risk of atrial fibrillation/flutter (Afib/Aflutter) and bleeding associated with ibrutinib compared to other treatments. The risks of Afib/Aflutter and all‐grade bleeding were significantly higher in the ibrutinib group. Background: Clinical trials raised concern that ibrutinib may increase the risk of atrial fibrillation/flutter (Afib/Aflutter) and major bleeding. However, the association has not been statistically validated, and there is no consensus regarding optimal management of anticoagulation among patients receiving ibrutinib who develop Afib/Aflutter. We performed a systematic review and pooled analysis to precisely assess the risk of Afib/Aflutter and bleeding associated with ibrutinib treatment in patients with hematologic malignancies. Patients and Methods: We searched PubMed, EMBASE, Cochrane Database, and meeting abstracts up to May 15, 2016, for randomized controlled trials comparing ibrutinib to chemotherapy, monoclonal antibody, or a combination. Primary outcomes were serious Afib/Aflutter and major bleeding. Secondary outcomes were all‐grade Afib/Aflutter and bleeding. We calculated the Mantel‐Haenszel risk ratio (RR) and estimated the effect of the treatments using a fixed‐effects model. Results: Ibrutinib treatment was associated with a significantly higher incidence of serious Afib/Aflutter (3.03% vs. 0.80%, RR = 3.80, 95% confidence interval [CI] = 1.56‐9.29, P = .003), all‐grade Afib/Aflutter (8.18% vs. 0.93%, RR = 8.81, 95% CI = 2.70‐28.75, P = .0003), and all‐grade bleeding (4.85% vs. 1.55%, RR = 2.93, 95% CI = 1.14‐7.52, P = .03) compared to control treatments. The observed between‐treatment difference in major bleeding rates was not statistically significant (3.69% vs. 2.13%, RR = 1.72, 95% CI = 0.95‐3.11, P = .07). The risk of these adverse events was not different between subgroups on the basis of pathology, treatment setting, dose, and duration of ibrutinib exposure. Conclusion: The risks of Afib/Aflutter and all‐grade bleeding were significantly higher in the ibrutinib group. These results indicate the need for vigilant monitoring while the patient is receiving ibrutinib therapy, and careful assessment of the risks and benefits of anticoagulation is required.

Cardioprotective role of β-blockers and angiotensin antagonists in early-onset anthracyclines-induced cardiotoxicity in adult patients: a systematic review and meta-analysis

Background Anthracyclines are commonly used chemotherapeutic agents with proven efficacy in such malignancies as breast cancer, Hodgkin and non-Hodgkin lymphomas. These agents are associated with irreversible accumulative dose-related cardiomyopathy. Many agents have been examined to reduce cardiotoxicity risk. Aims We performed a systematic review and meta-analysis to determine the efficacy of β-blockers and angiotensin antagonists to prevent early-onset anthracyclines-induced left ventricular dysfunction and cardiac events. Methods Relevant articles were searched in PubMed, EMBASE and Cochrane database of systematic reviews up to July 2015. Eligible studies were limited to randomised controlled trials comparing the efficacy of cardioprotective agents (β-blocker and angiotensin antagonist) with control (either no treatment or placebo) in adult patients (age >18 years) treated with anthracyclines-based regimens. Results Pooled analysis showed an association of β-blockers and/or angiotensin antagonists treatment with higher post-chemotherapy left ventricular ejection fraction (LVEF) of 64.03% compared with 57.48% for control treatment. The mean difference estimate (95% CI) was 6.06% (0.54 to 11.58), p=0.03, with significant heterogeneity, I2 (95% CI)=96% (82.7 to 109.3). Though the point estimate for the relative rate of cardiac events was lower in the experimental arm, the difference was not statistically significant. In an exploratory subgroup analysis, the benefit of experimental agents on LVEF preservation was prominent in patients treated with higher accumulative dose of anthracyclines, but not in the lower dose group. Conclusions β-Blockers and angiotensin antagonists treatments were associated with better LVEF preservation, and the benefit was prominent in patients treated with higher anthracyclines accumulative dose. Unexplained heterogeneity remains, indicating the need for more controlled studies. This analysis provides some support for the routine use of β-blockers or angiotensin antagonists in patients undergoing anthracyclines treatment, especially when higher accumulative dose is expected.

Update on iron metabolism and molecular perspective of common genetic and acquired disorder, hemochromatosis.

Iron is an essential component of erythropoiesis and its metabolism is tightly regulated by a variety of internal and external cues including iron storage, tissue hypoxia, inflammation and degree of erythropoiesis. There has been remarkable improvement in our understanding of the molecular mechanisms of iron metabolism past decades. The classical model of iron metabolism with iron response element/iron response protein (IRE/IRP) is now extended to include hepcidin model. Endogenous and exogenous signals funnel down to hepcidin via wide range of signaling pathways including Janus Kinase/Signal Transducer and Activator of Transcription 3 (JAK/STAT3), Bone Morphogenetic Protein/Hemojuvelin/Mothers Against Decapentaplegic Homolog (BMP/HJV/SMAD), and Von Hippel Lindau/Hypoxia-inducible factor/Erythropoietin (VHL/HIF/EPO), then relay to ferroportin, which directly regulates intra- and extracellular iron levels. The successful molecular delineation of iron metabolism further enhanced our understanding of common genetic and acquired disorder, hemochromatosis. The majority of the hereditary hemochromatosis (HH) patients are now shown to have mutations in the genes coding either upstream or downstream proteins of hepcidin, resulting in iron overload. The update on hepcidin centered mechanisms of iron metabolism and their clinical perspective in hemochromatosis will be discussed in this review.

Late onset ipilimumab-induced pericarditis and pericardial effusion: a rare but life threatening complication.

Metastatic cutaneous melanoma has poor prognosis with 2-year survival rate of 10–20%. Melanoma cells express various antigens including gp100, melanoma antigen recognized by T cells 1 (MART-1), and tyrosinase, which can induce immune-mediated anticancer response via T cell activation. Cytotoxic T-lymphocyte associated antigen-4 (CTLA-4) is an immune check point molecule that negatively regulates T cell activation and proliferation. Accordingly, recent phase III clinical trials demonstrated significant survival benefit with ipilimumab, a human monoclonal antibody (IgG1) that blocks the interaction of CTLA-4 with its ligands. Since the efficacy of ipilimumab depends on T cell activation, it is associated with substantial risk of immune mediated adverse reactions such as colitis, hepatitis, thyroiditis, and hypophysitis. We report the first case of late onset pericarditis and cardiac tamponade associated with ipilimumab treatment in patient with metastatic cutaneous melanoma.

4EBP1/c-MYC/PUMA and NF-κB/EGR1/BIM pathways underlie cytotoxicity of mTOR dual inhibitors in malignant lymphoid cells

The mammalian target of rapamycin (mTOR), a kinase that regulates proliferation and apoptosis, has been extensively evaluated as a therapeutic target in multiple malignancies. Rapamycin analogs, which partially inhibit mTOR complex 1 (mTORC1), exhibit immunosuppressive and limited antitumor activity, but sometimes activate survival pathways through feedback mechanisms involving mTORC2. Thus, attention has turned to agents targeting both mTOR complexes by binding the mTOR active site. Here we show that disruption of either mTOR-containing complex is toxic to acute lymphocytic leukemia (ALL) cells and identify 2 previously unrecognized pathways leading to this cell death. Inhibition of mTORC1-mediated 4EBP1 phosphorylation leads to decreased expression of c-MYC and subsequent upregulation of the proapoptotic BCL2 family member PUMA, whereas inhibition of mTORC2 results in nuclear factor-κB-mediated expression of the Early Growth Response 1 (EGR1) gene, which encodes a transcription factor that binds and transactivates the proapoptotic BCL2L11 locus encoding BIM. Importantly, 1 or both pathways contribute to death of malignant lymphoid cells after treatment with dual mTORC1/mTORC2 inhibitors. Collectively, these observations not only provide new insight into the survival roles of mTOR in lymphoid malignancies, but also identify alterations that potentially modulate the action of mTOR dual inhibitors in ALL.

WSB1 promotes tumor metastasis by inducing pVHL degradation.

The von Hippel-Lindau tumor suppressor pVHL is an E3 ligase that targets hypoxia-inducible factors (HIFs). Mutation of VHL results in HIF up-regulation and contributes to processes related to tumor progression such as invasion, metastasis, and angiogenesis. However, very little is known with regard to post-transcriptional regulation of pVHL. Here we show that WD repeat and SOCS box-containing protein 1 (WSB1) is a negative regulator of pVHL through WSB1s E3 ligase activity. Mechanistically, WSB1 promotes pVHL ubiquitination and proteasomal degradation, thereby stabilizing HIF under both normoxic and hypoxic conditions. As a consequence, WSB1 up-regulates the expression of HIF-1αs target genes and promotes cancer invasion and metastasis through its effect on pVHL. Consistent with this, WSB1 protein level negatively correlates with pVHL level and metastasis-free survival in clinical samples. This work reveals a new mechanism of pVHLs regulation by which cancer acquires invasiveness and metastatic tendency.

Dasatinib-induced pulmonary hypertension in chronic myelogenous leukaemia

A previously healthy 46-year-old woman presented to the outpatient clinic with chronic general weakness for a month. Physical examination showed splenomegaly and complete blood count showed white cell count 346 000/μL, haemoglobin 11.2 g/dL, platelets 336 000/μL with a differential of neutrophils 21%, bands 32%, lymphocytes 8%, monocytes 5%, promyelocytes 22%, myelocytes 11% and blasts 9%. Subsequent bone marrow biopsy showed cellularity of 100% with marked myeloid hyperplasia and blasts of 21%. Cytogenetics demonstrated BCR-ABL1 translocation confirming the diagnosis of chronic myelogenous leukaemia (CML).1 Imatinib was started as an initial treatment, however the patient developed …