April Shamy

Targeting the Apoptotic Pathway with BCL-2 Inhibitors Sensitizes Primary Chronic Lymphocytic Leukemia Cells to Vesicular Stomatitis Virus-Induced Oncolysis

ABSTRACT Chronic lymphocytic leukemia (CLL) is characterized by clonal accumulation of CD5+ CD19+ B lymphocytes that are arrested in the G0/G1 phase of the cell cycle and fail to undergo apoptosis because of overexpression of the antiapoptotic B-cell CLL/lymphoma 2 (BCL-2) protein. Oncolytic viruses, such as vesicular stomatitis virus (VSV), have emerged as potential anticancer agents that selectively target and kill malignant cells via the intrinsic mitochondrial pathway. Although primary CLL cells are largely resistant to VSV oncolysis, we postulated that targeting the apoptotic pathway via inhibition of BCL-2 may sensitize CLL cells to VSV oncolysis. In the present study, we examined the capacity of EM20-25—a small-molecule antagonist of the BCL-2 protein—to overcome CLL resistance to VSV oncolysis. We demonstrate a synergistic effect of the two agents in primary ex vivo CLL cells (combination index of 0.5; P < 0.0001). In a direct comparison of peripheral blood mononuclear cells from healthy volunteers with primary CLL, the two agents combined showed a therapeutic index of 19-fold; furthermore, the combination of VSV and EM20-25 increased apoptotic cell death in Karpas-422 and Granta-519 B-lymphoma cell lines (P < 0.005) via the intrinsic mitochondrial pathway. Mechanistically, EM20-25 blocked the ability of the BCL-2 protein to dimerize with proapoptotic BAX protein, thus sensitizing CLL to VSV oncolytic stress. Together, these data indicate that the use of BCL-2 inhibitors may improve VSV oncolysis in treatment-resistant hematological malignancies, such as CLL, with characterized defects in the apoptotic response.

VSV Oncolysis in Combination With the BCL-2 Inhibitor Obatoclax Overcomes Apoptosis Resistance in Chronic Lymphocytic Leukemia

In chronic lymphocytic leukemia (CLL), overexpression of antiapoptotic B-cell leukemia/lymphoma 2 (BCL-2) family members contributes to leukemogenesis by interfering with apoptosis; BCL-2 expression also impairs vesicular stomatitis virus (VSV)-mediated oncolysis of primary CLL cells. In the effort to reverse resistance to VSV-mediated oncolysis, we combined VSV with obatoclax (GX15-070)-a small-molecule BCL-2 inhibitor currently in phase 2 clinical trials-and examined the molecular mechanisms governing the in vitro and in vivo antitumor efficiency of combining the two agents. In combination with VSV, obatoclax synergistically induced cell death in primary CLL samples and reduced tumor growth in severe combined immunodeficient (SCID) mice-bearing A20 lymphoma tumors. Mechanistically, the combination stimulated the mitochondrial apoptotic pathway, as reflected by caspase-3 and -9 cleavage, cytochrome c release and BAX translocation. Combination treatment triggered the release of BAX from BCL-2 and myeloid cell leukemia-1 (MCL-1) from BAK, whereas VSV infection induced NOXA expression and increased the formation of a novel BAX-NOXA heterodimer. Finally, NOXA was identified as an important inducer of VSV-obatoclax driven apoptosis via knockdown and overexpression of NOXA. These studies offer insight into the synergy between small-molecule BCL-2 inhibitors such as obatoclax and VSV as a combination strategy to overcome apoptosis resistance in CLL.

Patient-related factors independently impact overall survival in patients with myelodysplastic syndromes: an MDS-CAN prospective study.

Little is known about the effects of frailty, disability and physical functioning on the clinical outcomes for myelodysplastic syndromes (MDS). We investigated the predictive value of these factors on overall survival (OS) in 445 consecutive patients with MDS and chronic monomyelocytic leukaemia (CMML) enrolled in a multi‐centre prospective national registry. Frailty, comorbidity, instrumental activities of daily living, disability, quality of life, fatigue and physical performance measures were evaluated at baseline and were added as covariates to conventional MDS‐related factors as predictors of OS in Cox proportional hazards models. The median age was 73 years, and 79% had revised International Prognostic Scoring System (IPSS‐R) risk scores of intermediate or lower. Frailty correlated only modestly with comorbidity. OS was significantly shorter for patients with higher frailty and comorbidity scores, any disability, impaired grip strength and timed chair stand tests. By multivariate analysis, the age‐adjusted IPSS‐R, frailty (Hazard ratio 2·7 (95% confidence interval [CI] 1·7–4·2), P < 0·0001) and Charlson comorbidity score (Hazard ratio 1·8 (95% CI 1·1–2·8), P = 0·01) were independently prognostic of OS. Incorporation of frailty and comorbidity scores improved risk stratification of the IPSS‐R by 30% and 5%, respectively. These data demonstrate for the first time, the importance of considering frailty in prognostic models and a potential target for therapeutic intervention in optimizing clinical outcomes in older MDS patients.

BCL-2 Inhibitors Sensitize Therapy-resistant Chronic Lymphocytic Leukemia Cells to VSV Oncolysis

Many primary cancers including chronic lymphocytic leukemia (CLL) are resistant to vesicular stomatitis virus (VSV)-induced oncolysis due to overexpression of the antiapoptotic and antiautophagic members of the B-cell lymphoma-2 (BCL-2) family. In the present study, we investigated the mechanisms of CLL cell death induced as a consequence of VSV infection in the presence of BCL-2 inhibitors, obatoclax, and ABT-737 in primary ex vivo CLL patient samples. Microarray analysis of primary CD19⁺ CD5⁺ CLL cells treated with obatoclax and VSV revealed changes in expression of genes regulating apoptosis, the mechanistic target of rapamycin (mTOR) pathway, and cellular metabolism. A combined therapeutic effect was observed for VSV and BCL-2 inhibitors in cells from untreated patients and from patients unresponsive to standard of care therapy. In addition, combination treatment induced several markers of autophagy--LC3-II accumulation, p62 degradation, and staining of autophagic vacuoles. Inhibition of early stage autophagy using 3-methyladenine (3-MA) led to increased apoptosis in CLL samples. Mechanistically, a combination of BCL-2 inhibitors and VSV disrupted inhibitory interactions of Beclin-1 with BCL-2 and myeloid cell leukemia-1 (MCL-1), thus biasing cells toward autophagy. We propose a mechanism in which changes in cellular metabolism, coupled with pharmacologic disruption of the BCL-2-Beclin-1 interactions, facilitate induction of apoptosis and autophagy to mediate the cytolytic effect of VSV.

Overall survival in lower IPSS risk MDS by receipt of iron chelation therapy, adjusting for patient‐related factors and measuring from time of first red blood cell transfusion dependence: an MDS‐CAN analysis

Analyses suggest iron overload in red blood cell (RBC) transfusion‐dependent (TD) patients with myleodysplastic syndrome (MDS) portends inferior overall survival (OS) that is attenuated by iron chelation therapy (ICT) but may be biassed by unbalanced patient‐related factors. The Canadian MDS Registry prospectively measures frailty, comorbidity and disability. We analysed OS by receipt of ICT, adjusting for these patient‐related factors. TD International Prognostic Scoring System (IPSS) low and intermediate‐1 risk MDS, at RBC TD, were included. Predictive factors for OS were determined. A matched pair analysis considering age, revised IPSS, TD severity, time from MDS diagnosis to TD, and receipt of disease‐modifying agents was conducted. Of 239 patients, 83 received ICT; frailty, comorbidity and disability did not differ from non‐ICT patients. Median OS from TD was superior in ICT patients (5·2 vs. 2·1 years; P < 0·0001). By multivariate analysis, not receiving ICT independently predicted inferior OS, (hazard ratio for death 2·0, P = 0·03). In matched pair analysis, OS remained superior for ICT patients (P = 0·02). In this prospective, non‐randomized analysis, receiving ICT was associated with superior OS in lower IPSS risk MDS, adjusting for age, frailty, comorbidity, disability, revised IPSS, TD severity, time to TD and receiving disease‐modifying agents. This provides additional evidence that ICT may confer clinical benefit.

The immunomodulatory agents lenalidomide and thalidomide for treatment of the myelodysplastic syndromes: A clinical practice guideline

BACKGROUND Myelodysplastic syndromes (MDS) are clonal disorders that result in cytopenias and risk of acute myeloid leukemia. Incidence increases with age and more diagnoses are expected with the aging population. Treatment includes red blood cell transfusion for anemia. The immunomodulatory agents (imids) thalidomide and lenalidomide may induce transfusion independence. This guideline systematically reviews evidence on imids to treat MDS and makes evidence-based recommendations. METHODS The literature and meeting abstracts were searched for phase 2-3 clinical trials. Data on efficacy, toxicity, and which patients benefit were extracted. RESULTS 7019 citations on MDS management were identified. Thirteen publications and 9 meeting abstracts met eligibility criteria. CONCLUSIONS Lenalidomide is recommended as first line therapy in lower risk del5q MDS. There is insufficient evidence to recommend lenalidomide for treatment of higher risk del5q MDS or AML, or for any risk non-del5q MDS or AML. Combining lenalidomide with other agents is not recommended. Thalidomide is not recommended.

Iron overload in myelodysplastic syndromes: Evidence based guidelines from the Canadian consortium on MDS

In 2008 the first evidence-based Canadian consensus guideline addressing the diagnosis, monitoring and management of transfusional iron overload in patients with myelodysplastic syndromes (MDS) was published. The Canadian Consortium on MDS, comprised of hematologists from across Canada with a clinical and academic interest in MDS, reconvened to update these guidelines. A literature search was updated in 2017; topics reviewed include mechanisms of iron overload induced cellular damage, evidence for clinical endpoints impacted by iron overload including organ dysfunction, infections, marrow failure, overall survival, acute myeloid leukemia progression, and endpoints around hematopoietic stem-cell transplant. Evidence for an impact of iron reduction on the same endpoints is discussed, guidelines are updated, and areas identified where evidence is suboptimal. The guidelines address common questions around the diagnosis, workup and management of iron overload in clinical practice, and take the approach of who, when, why and how to treat iron overload in MDS. Practical recommendations for treatment and monitoring are made. Evidence levels and grading of recommendations are provided for all clinical endpoints examined.