Page 98 - 2014 Printable Abstract Book
P. 98
S29 NF-kB SIGNALING NETWORK IN RADIATION RESPONSE
(S2901) Regulation of cell death and autophagy. Alex Almasan, Cleveland Clinic, Cleveland, OH
The activation of NF-kB plays a central role in cell survival, while its inhibition makes various
cytotoxic effects, such as that triggered by TNFa, possible. Several genes that are upregulated by NF-kB,
such as IAPs, play cytoprotective roles by avoiding apoptosis through different mechanisms, including
inhibition of caspase activation. NF-kB-mediated expression of cytokines and interferons (IFN) mediates
virus-triggered host defense mechanisms. However, we showed that at later stages of poliovirus
replication the p65-RelA component of the NF-kB complex undergoes a specific cleavage mediated by
poliovirus protease 3C. Cleavage of p65-RelA occurs during replication of other picornaviruses, thus
suggesting that inactivation of NF-kB function by proteolytic cleavage of p65-RelA is the common
mechanism for their suppression of the innate immune response (Neznanov N, JBC, 2005). Our
biochemical and genetic analyses revealed the requirement of NF-kB for the induction of Apo2L/TRAIL by
INFb (Rani MR, JICR, 2007). Transcriptional activation of Apo2L/TRAIL, a tumor-specific cell death ligand,
by IFNs is also involved in the activation of natural killer cells, cytotoxic T lymphocytes, and dendritic cells
(Almasan A, CGFR, 2003). Receptor-mediated apoptosis in response to Apo2L/TRAIL is antagonized by NF-
kB-dependent cell survival pathways. Suppression of NF-kB survival signaling, as we have shown for No-
Cbl, sensitizes melanoma but not normal cell lines to Apo2L/TRAIL (Chawla-Sarkar M, JBC, 2003). NO-Cbl
inhibited IKK activation, characterized by decreased phosphorylation of IkBα and inhibition of NF-kB DNA
binding activity. Of the anti-apoptotic Bcl-2 family members, the most compelling evidence is for Bcl-xL
upregulation, that we find to be critical in treatment-resistant chronic lymphocytic leukemia and in cells
chronically resistant to Bcl-2 family inhibitors; these can also activate autophagy by displacing BECN1 from
Bcl-2, Bcl-xL, or Mcl-1. Autophagy is a mechanism involved in therapy resistance in a variety of tumor cells.
We have shown that autophagy can be activated by cytoplasmic ATM (cATM), through AMPK and ULK1
(Singh K, Autophagy, 2012). cATM also activates TAK1 and IKK, positive regulators of NF-kB. How NF-kB
regulates expression of key autophagy regulatory genes has yet to be determined.
(S2902) Blocking the formation of radiation-induced breast cancer stem cells through targeting of the
NF-kB-stemness gene pathway. Xinhui Wang, Harvard Medical School, Boston, MA
The goal of adjuvant (post-surgery) radiation therapy (RT) for breast cancer (BC) is to eliminate
residual cancer cells, leading to better local tumor control and thus improving patient survival. However,
radioresistance increases the risk of tumor recurrence and negatively affects survival. Recent evidence
shows that breast cancer stem cells (BCSCs) are radiation-resistant and that relatively differentiated BC
cells can be reprogrammed into induced BCSCs (iBCSCs) via radiation-induced re-expression of the
stemness genes. Here we show that in radiation (IR)-treated mice bearing syngeneic mammary tumors,
IR-induced stemness correlated with increased spontaneous lung metastasis (51.7%). However, IR-
induced stemness was blocked by targeting the NF-κB- stemness gene pathway with disulfiram (DSF) and
2+
Copper (Cu ). DSF is an inhibitor of aldehyde dehydrogenase (ALDH) and an FDA-approved drug for
2+
treating alcoholism. DSF binds to Cu to form DSF-Cu complexes (DSF/Cu), which act as a potent apoptosis
inducer and an effective proteasome inhibitor, which, in turn, inhibits NF-κB activation. Treatment of mice
with RT and DSF significantly inhibited mammary primary tumor growth (79.4%) and spontaneous lung
96 | P a g e
(S2901) Regulation of cell death and autophagy. Alex Almasan, Cleveland Clinic, Cleveland, OH
The activation of NF-kB plays a central role in cell survival, while its inhibition makes various
cytotoxic effects, such as that triggered by TNFa, possible. Several genes that are upregulated by NF-kB,
such as IAPs, play cytoprotective roles by avoiding apoptosis through different mechanisms, including
inhibition of caspase activation. NF-kB-mediated expression of cytokines and interferons (IFN) mediates
virus-triggered host defense mechanisms. However, we showed that at later stages of poliovirus
replication the p65-RelA component of the NF-kB complex undergoes a specific cleavage mediated by
poliovirus protease 3C. Cleavage of p65-RelA occurs during replication of other picornaviruses, thus
suggesting that inactivation of NF-kB function by proteolytic cleavage of p65-RelA is the common
mechanism for their suppression of the innate immune response (Neznanov N, JBC, 2005). Our
biochemical and genetic analyses revealed the requirement of NF-kB for the induction of Apo2L/TRAIL by
INFb (Rani MR, JICR, 2007). Transcriptional activation of Apo2L/TRAIL, a tumor-specific cell death ligand,
by IFNs is also involved in the activation of natural killer cells, cytotoxic T lymphocytes, and dendritic cells
(Almasan A, CGFR, 2003). Receptor-mediated apoptosis in response to Apo2L/TRAIL is antagonized by NF-
kB-dependent cell survival pathways. Suppression of NF-kB survival signaling, as we have shown for No-
Cbl, sensitizes melanoma but not normal cell lines to Apo2L/TRAIL (Chawla-Sarkar M, JBC, 2003). NO-Cbl
inhibited IKK activation, characterized by decreased phosphorylation of IkBα and inhibition of NF-kB DNA
binding activity. Of the anti-apoptotic Bcl-2 family members, the most compelling evidence is for Bcl-xL
upregulation, that we find to be critical in treatment-resistant chronic lymphocytic leukemia and in cells
chronically resistant to Bcl-2 family inhibitors; these can also activate autophagy by displacing BECN1 from
Bcl-2, Bcl-xL, or Mcl-1. Autophagy is a mechanism involved in therapy resistance in a variety of tumor cells.
We have shown that autophagy can be activated by cytoplasmic ATM (cATM), through AMPK and ULK1
(Singh K, Autophagy, 2012). cATM also activates TAK1 and IKK, positive regulators of NF-kB. How NF-kB
regulates expression of key autophagy regulatory genes has yet to be determined.
(S2902) Blocking the formation of radiation-induced breast cancer stem cells through targeting of the
NF-kB-stemness gene pathway. Xinhui Wang, Harvard Medical School, Boston, MA
The goal of adjuvant (post-surgery) radiation therapy (RT) for breast cancer (BC) is to eliminate
residual cancer cells, leading to better local tumor control and thus improving patient survival. However,
radioresistance increases the risk of tumor recurrence and negatively affects survival. Recent evidence
shows that breast cancer stem cells (BCSCs) are radiation-resistant and that relatively differentiated BC
cells can be reprogrammed into induced BCSCs (iBCSCs) via radiation-induced re-expression of the
stemness genes. Here we show that in radiation (IR)-treated mice bearing syngeneic mammary tumors,
IR-induced stemness correlated with increased spontaneous lung metastasis (51.7%). However, IR-
induced stemness was blocked by targeting the NF-κB- stemness gene pathway with disulfiram (DSF) and
2+
Copper (Cu ). DSF is an inhibitor of aldehyde dehydrogenase (ALDH) and an FDA-approved drug for
2+
treating alcoholism. DSF binds to Cu to form DSF-Cu complexes (DSF/Cu), which act as a potent apoptosis
inducer and an effective proteasome inhibitor, which, in turn, inhibits NF-κB activation. Treatment of mice
with RT and DSF significantly inhibited mammary primary tumor growth (79.4%) and spontaneous lung
96 | P a g e
