Page 253 - 2014 Printable Abstract Book
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chemotherapy in conjunction with radiation was thus observed to be more efficacious in disrupting the
integrity, more specifically the extracellular matrix of TES. The ability of nanoliposomal TPT to release the
active drug over time contributes to the therapeutic efficacy in combinatorial treat-ment. Efforts are
underway to implant TES in dorsal skin fold window chamber and monitor the radiosensitizing potential
of NTPT on neo-vascularization of the tumor by intravital imaging. Support: NCI R25CA153954 & NCI
R21CA173609.
(PS4-30) Akt inhibitor mk-2206 is an effective radio-sensitizer of p53 deficient triple (tnbc) cells through
supression of dna-pkcs and atm protein expression. Youping Sun, PhD; Hongning Zhou, MPH; Clifford K.S.
Chao, MD; Tom K. Hei, PhD; and Eileen P. Connolly, MD; PhD, Columbia University Medical Center, New
York, NY
Purpose: Triple negative breast cancer (TNBC) is an aggressive tumor with a higher locoregional
recurrence. Mutations in the PI3K/Akt/mTOR pathway leading to up-regulation of Akt occur with high
frequency in TNBC. Hyperactive Akt is associated with increase radiation resistance. p53 plays a key role
in mediating G1 cell cycle arrest and G2/M arrest following genotoxic stress such as radiation; p53-
deficient cells however must rely on alternate mechanisms for cell cycle arrest in G2/M-phases. Inhibition
of Akt therefore would be expected to act in a synthetic lethal fashion to radiosensitize p53 deficient TNBC
cells by increasing mitotic cell arrest. Given that p53 mutations occur in 80% of TNBC this may be an
effective strategy for radiosensitizing TNBC. Methods: Experiments were conducted using BT-549 and
SUM-149 cells, both well-established models for p53-deficient TNBC. Cells were treated with MK-2206, a
potent allosteric Akt inhibitor, alone or in combination with increasing doses of radiation from 0-8 Gy. In
vitro studies performed included; cell survival assays, immunoblot analysis of key proteins, FACS analysis
for cell cycle, apoptosis, and γH2AX staining. Results: We found that the combination of IR and Akt
inhibition by MK-2206 led to synergistic effects. As expected, MK-2206 inhibited both endogenous and
radiation-induced Akt activation and that of its downstream targets. Decreased clonogenic survival was
seen after 2 or 24 hours pretreatment with MK-2206. Evaluation of the DNA damage response pathway
demonstrated decreased levels of total DNA-PK and ATM transcriptionally and translationally dependent
on p53 status, as well as a delayed DNA damage response. Analysis of the promoter of DNA-PKcs suggests
that E2F1, E2F3 is suppressed by MK-2206 and may be directly involved in the reduction of DNA-PKcs
mRNA and protein expression. Conclusions: These studies demonstrate that targeted inhibition of Akt
effectively radiosensitizes p53 deficient TNBC cells lines, possibly through suppression of DNA repair gene
expression, DNA-PKcs and ATM. E2F1 and E2F3 suppression by MK-2206 may be involved in the reduction
of DNA-PKcs mRNA and protein.
(PS4-31) Effects of heavy ion particle irradiation on human endothelial barrier structure and function.
2
1
1
1
Preety Sharma, PhD ; Peter Guida ; and Peter Grabham, PhD, Columbia University, New York, NY and
2
Brookhaven National Laboratory, Upton, NY
Space travel involves exposure to biologically effective heavy ion radiation and is consequently a
concern for possible degenerative disorders in humans. A significant target for radiation effects is the
vascular system, which is crucial to healthy functioning of the tissues. Its pathology is linked to disrupted
endothelial barrier function and is not only a primary event in a range of degenerative diseases but also
251 | P a g e
integrity, more specifically the extracellular matrix of TES. The ability of nanoliposomal TPT to release the
active drug over time contributes to the therapeutic efficacy in combinatorial treat-ment. Efforts are
underway to implant TES in dorsal skin fold window chamber and monitor the radiosensitizing potential
of NTPT on neo-vascularization of the tumor by intravital imaging. Support: NCI R25CA153954 & NCI
R21CA173609.
(PS4-30) Akt inhibitor mk-2206 is an effective radio-sensitizer of p53 deficient triple (tnbc) cells through
supression of dna-pkcs and atm protein expression. Youping Sun, PhD; Hongning Zhou, MPH; Clifford K.S.
Chao, MD; Tom K. Hei, PhD; and Eileen P. Connolly, MD; PhD, Columbia University Medical Center, New
York, NY
Purpose: Triple negative breast cancer (TNBC) is an aggressive tumor with a higher locoregional
recurrence. Mutations in the PI3K/Akt/mTOR pathway leading to up-regulation of Akt occur with high
frequency in TNBC. Hyperactive Akt is associated with increase radiation resistance. p53 plays a key role
in mediating G1 cell cycle arrest and G2/M arrest following genotoxic stress such as radiation; p53-
deficient cells however must rely on alternate mechanisms for cell cycle arrest in G2/M-phases. Inhibition
of Akt therefore would be expected to act in a synthetic lethal fashion to radiosensitize p53 deficient TNBC
cells by increasing mitotic cell arrest. Given that p53 mutations occur in 80% of TNBC this may be an
effective strategy for radiosensitizing TNBC. Methods: Experiments were conducted using BT-549 and
SUM-149 cells, both well-established models for p53-deficient TNBC. Cells were treated with MK-2206, a
potent allosteric Akt inhibitor, alone or in combination with increasing doses of radiation from 0-8 Gy. In
vitro studies performed included; cell survival assays, immunoblot analysis of key proteins, FACS analysis
for cell cycle, apoptosis, and γH2AX staining. Results: We found that the combination of IR and Akt
inhibition by MK-2206 led to synergistic effects. As expected, MK-2206 inhibited both endogenous and
radiation-induced Akt activation and that of its downstream targets. Decreased clonogenic survival was
seen after 2 or 24 hours pretreatment with MK-2206. Evaluation of the DNA damage response pathway
demonstrated decreased levels of total DNA-PK and ATM transcriptionally and translationally dependent
on p53 status, as well as a delayed DNA damage response. Analysis of the promoter of DNA-PKcs suggests
that E2F1, E2F3 is suppressed by MK-2206 and may be directly involved in the reduction of DNA-PKcs
mRNA and protein expression. Conclusions: These studies demonstrate that targeted inhibition of Akt
effectively radiosensitizes p53 deficient TNBC cells lines, possibly through suppression of DNA repair gene
expression, DNA-PKcs and ATM. E2F1 and E2F3 suppression by MK-2206 may be involved in the reduction
of DNA-PKcs mRNA and protein.
(PS4-31) Effects of heavy ion particle irradiation on human endothelial barrier structure and function.
2
1
1
1
Preety Sharma, PhD ; Peter Guida ; and Peter Grabham, PhD, Columbia University, New York, NY and
2
Brookhaven National Laboratory, Upton, NY
Space travel involves exposure to biologically effective heavy ion radiation and is consequently a
concern for possible degenerative disorders in humans. A significant target for radiation effects is the
vascular system, which is crucial to healthy functioning of the tissues. Its pathology is linked to disrupted
endothelial barrier function and is not only a primary event in a range of degenerative diseases but also
251 | P a g e
