Presentation Title

BV6, an IAP antagonist, potentiates glucocorticoid-evoked apoptosis of CEM human leukemia cells.

Start Date

November 2016

End Date

November 2016

Location

HUB 302-152

Type of Presentation

Poster

Abstract

Glucocorticoids (GCs) are effective therapeutic agents because of their capability to activate apoptosis in human acute lymphoblastic leukemia (ALL) cells. GCs trigger intrinsic and extrinsic apoptotic pathways through a gene regulatory effect on key pro- and anti-apoptotic genes that promote cytochrome c and Smac (Second Mitochondrial Activator of Caspase) mediated activation of caspases. Our laboratory is investigating molecular pathways that regulate apoptosis using a set of CCRF-CEM human derived ALL cell lines. CEMC7-14 and CEMC1-15 mE#3(ectopic expression of the transcriptional regulator E4BP4) are sensitive, and CEMC1-15 are resistant to GC-evoked apoptosis. In the sensitive cells, dexamethasone (Dex), a synthetic GC, upregulates proapoptotic genes, but paradoxically, also upregulates the anti-apoptotic gene BIRC3 (aka inhibitor of apoptosis protein, cIAP-2), which inhibits Smac and caspase activation. We are testing the hypothesis that Dex-mediated BIRC3 upregulation is a rescue mechanism of cells to escape apoptosis. The IAP antagonist BV6 is a Smac mimetic that can override IAP-mediated inhibition of apoptosis. We tested whether treatment with BV6 facilitated basal or Dex-mediated apoptosis. To investigate the potential of BV6 to affect cell viability, MTT assays were performed. BV6 alone evoked cell death on all three cell lines. Co-treatment of BV6 and Dexpotentiated cell death by more than 50% in sensitive and resistant leukemia cells. To test the ability of BV6 to affect apoptosis, Annexin V labeling was visualized by epifluorescence microscopy. BV6 enhanced Annexin V labeling in control and Dex-treated cells, suggesting that inhibition of BIRC3 potentiated the apoptotic pathway. Our data support the hypothesis that Dex-mediated up-regulation of BIRC3 may be an anti-apoptotic rescue mechanism activated in parallel to the proapoptotic response in leukemia cells. The synergistic combination of GCs and Smac mimetics is relevant for the future of combined therapies for leukemia.

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BV6, an IAP antagonist, potentiates glucocorticoid-evoked apoptosis of CEM human leukemia cells.

HUB 302-152

Glucocorticoids (GCs) are effective therapeutic agents because of their capability to activate apoptosis in human acute lymphoblastic leukemia (ALL) cells. GCs trigger intrinsic and extrinsic apoptotic pathways through a gene regulatory effect on key pro- and anti-apoptotic genes that promote cytochrome c and Smac (Second Mitochondrial Activator of Caspase) mediated activation of caspases. Our laboratory is investigating molecular pathways that regulate apoptosis using a set of CCRF-CEM human derived ALL cell lines. CEMC7-14 and CEMC1-15 mE#3(ectopic expression of the transcriptional regulator E4BP4) are sensitive, and CEMC1-15 are resistant to GC-evoked apoptosis. In the sensitive cells, dexamethasone (Dex), a synthetic GC, upregulates proapoptotic genes, but paradoxically, also upregulates the anti-apoptotic gene BIRC3 (aka inhibitor of apoptosis protein, cIAP-2), which inhibits Smac and caspase activation. We are testing the hypothesis that Dex-mediated BIRC3 upregulation is a rescue mechanism of cells to escape apoptosis. The IAP antagonist BV6 is a Smac mimetic that can override IAP-mediated inhibition of apoptosis. We tested whether treatment with BV6 facilitated basal or Dex-mediated apoptosis. To investigate the potential of BV6 to affect cell viability, MTT assays were performed. BV6 alone evoked cell death on all three cell lines. Co-treatment of BV6 and Dexpotentiated cell death by more than 50% in sensitive and resistant leukemia cells. To test the ability of BV6 to affect apoptosis, Annexin V labeling was visualized by epifluorescence microscopy. BV6 enhanced Annexin V labeling in control and Dex-treated cells, suggesting that inhibition of BIRC3 potentiated the apoptotic pathway. Our data support the hypothesis that Dex-mediated up-regulation of BIRC3 may be an anti-apoptotic rescue mechanism activated in parallel to the proapoptotic response in leukemia cells. The synergistic combination of GCs and Smac mimetics is relevant for the future of combined therapies for leukemia.