Modulation Of Death Pathways Research Articles

Abstract 1061: Modulation of death pathways by TRAILR2 agonist antibody and NF-κB pathway by NIK inhibitor in HPV-positive head and neck squamous cell carcinomas

Abstract Head and neck squamous cell carcinomas (HNSCC) induced by human papilloma virus (HPV) have increased recently in the US, and exhibit a different prognosis and response to therapies from HPV(-) cancers. Analysis of HNSCC TCGA datasets provide evidence for distinct alterations in expression of components of the NF-κB and death pathways in HNSCC with different HPV status. Previously, we have found that birinipant, a novel SMAC mimetic that inhibits inhibitor of apoptosis proteins (IAPs), sensitizes a subset of HPV(-) HNSCC cell lines to death agonists like TNF-α and TRAIL. In this study, we have observed that birinipant also sensitizes most HPV(+) cell lines to TRAIL and TNF-α in vitro. The IC50 of birinipant was under 50nM for HPV(+) UPCI-SCC-90 and UM-SCC-47 cell lines, when combined with TNF-α or TRAIL. To explore the therapeutic potential of enhancing TRAILR mediated death signaling in HPV(+) HNSCC cells, we investigated the effects of an agonistic polyclonal TRAILR2 antibody. Treatment of cells with TRAILR2 antibody alone shows little or no inhibitory effect on UPCI-SCC-90 and UM-SCC-47 cells in vitro. However, a combination of birinipant and TRAILR2 antibody, or triple combination of birinipant, TRAIL, and TRAILR2 antibody shows additive or synergistic effects to inhibit cell proliferation and induce cell death in a dose dependent manner. In addition, our preliminary data suggested that the non-canonical NF-κB pathway is predominately activated in HPV(+) HNSCC cells, and that NF-κB inducing kinase (NIK) is a key component of this pathway. When we tested the NIK inhibitor 4H-isoquinoline-1,3-dione in UPCI-SCC-90 cells, we found it reduced cell proliferation in a dose-dependent manner (IC50 =1.5 μM). Taken together, these results indicate that TNF-α, TRAIL, and TRAILR2 agonist antibody sensitized birinipant anti-tumor activity, and triple combination exhibited synergistic effects in HPV(+) HNSCC cell lines. NIK inhibitor alone inhibits cell proliferation of HPV(+) cells, supporting the hypothesis of aberrant activation of alternative pathway in HPV(+) HNSCC cells. (Supported by NIDCD intramural projects ZIA-DC-000016, 73, 74). Citation Format: Yi An, Lillian Sun, Adeeb Derakhshan, Sophie Carlson, Rita Das, Zhong Chen, Carter Van Waes. Modulation of death pathways by TRAILR2 agonist antibody and NF-κB pathway by NIK inhibitor in HPV-positive head and neck squamous cell carcinomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1061. doi:10.1158/1538-7445.AM2017-1061

Mitochondrial VDAC and hexokinase together modulate plant programmed cell death

The voltage-dependent anion channel (VDAC) and mitochondrially located hexokinase have been implicated both in pathways leading to cell death on the one hand, and immortalization in tumor formation on the other. While both proteins have also been implicated in death processes in plants, their interaction has not been explored. We have examined cell death following heterologous expression of a rice VDAC in the tobacco cell line BY2 and in leaves of tobacco plants and show that it is ameliorated by co-expression of hexokinase. Hexokinase also abrogates death induced by H2O2. We conclude that the ratio of expression of the two proteins and their interaction play a major role in modulating death pathways in plants.

Oestrogen modulates human macrophage apoptosis via differential signalling through oestrogen receptor‐α and β

AbstractHuman macrophages express oestrogen receptors and are therefore competent to respond to the hormone present in their microenvironment, which is implicated in sexual dimorphism observed in several immune and autoimmune phenomena. An earlier study from this laboratory demonstrated 17β‐oestradiol (E2) induced apoptosis in macrophages derived from human peripheral blood monocytes and THP‐1 acute monocytic leukaemia cell line when Bcl‐2 was down‐regulated; however, the involvement of E2 receptor subtypes in the modulation of death pathways in these cells remain unknown. Using macrophages derived from THP‐1 human acute monocytic leukaemia cells as a model, we demonstrate that plasma membrane associated oestrogen receptor (ER) ‐α participate in E2 induced Bcl‐2 increase, through activation of the mitogen activated protein kinase (MAPK) pathway whereas cytosolic ER‐β transmits signals for the pro‐apoptotic event of Bax translocation. The mechanistic basis of Bax translocation comprised of ER‐β mediated increase in intracellular pH, facilitated by activation of the Na+–H+ exchanger. Intracellular alkalinization accompanied by concomitant Bcl‐2 increase and Bax migration does not cause cellular apoptosis; however, siRNA mediated down‐regulation of ER‐α during E2 exposure leads to inhibition of Bcl‐2 increase and consequently apoptosis due to the unopposed action of mitochondrial Bax. In summary, this study underscores the importance of integrative signalling modality from multiple oestrogen receptor pools in modulating oestrogen effects on human monocyte‐derived macrophage apoptotic signalling pathway, which opens new vistas to explore the use of selective oestrogen receptor modulators in apoptosis‐based therapies.

Oestrogen modulates human macrophage apoptosisviadifferential signalling through oestrogen receptor-α and β

Human macrophages express oestrogen receptors and are therefore competent to respond to the hormone present in their microenvironment, which is implicated in sexual dimorphism observed in several immune and autoimmune phenomena. An earlier study from this laboratory demonstrated 17beta-oestradiol (E2) induced apoptosis in macrophages derived from human peripheral blood monocytes and THP-1 acute monocytic leukaemia cell line when Bcl-2 was down-regulated; however, the involvement of E2 receptor subtypes in the modulation of death pathways in these cells remain unknown. Using macrophages derived from THP-1 human acute monocytic leukaemia cells as a model, we demonstrate that plasma membrane associated oestrogen receptor (ER) -alpha participate in E2 induced Bcl-2 increase, through activation of the mitogen activated protein kinase (MAPK) pathway whereas cytosolic ER-beta transmits signals for the pro-apoptotic event of Bax translocation. The mechanistic basis of Bax translocation comprised of ER-beta mediated increase in intracellular pH, facilitated by activation of the Na(+)-H(+) exchanger. Intracellular alkalinization accompanied by concomitant Bcl-2 increase and Bax migration does not cause cellular apoptosis; however, siRNA mediated down-regulation of ER-alpha during E2 exposure leads to inhibition of Bcl-2 increase and consequently apoptosis due to the unopposed action of mitochondrial Bax. In summary, this study underscores the importance of integrative signalling modality from multiple oestrogen receptor pools in modulating oestrogen effects on human monocyte-derived macrophage apoptotic signalling pathway, which opens new vistas to explore the use of selective oestrogen receptor modulators in apoptosis-based therapies.