Page 364 - 2014 Printable Abstract Book
P. 364
lpa2 transcript showed a time- and dose-dependent up-regulation in response to γ-irradiation. Promoter
analysis of the lpa2 gene revealed the presence of an NF-κB binding site in the promoter region. The
radiation-induced upregulation was abolished by mutation of the NF-κB site. Pharmacological inhibition
of ATM/ATR kinases by CGK-733 also abrogated lpa2 upregulation, suggesting that lpa2 is a DNA damage
response gene, upregulated by ATM via NF-kB activation. To study the role of LPA2 activation in DNA
damage repair γH2AX level was monitored at different postradiation time points in IEC-6 cells. The level
of γH2AX peaked at 15-30 min after radiation, and showed a significantly faster resolution in LPA treated
cells compared to vehicle. The treatment of IEC-6 cells with an LPA2 specific antagonist inhibited the
resolution of γH2AX, suggesting that among the different LPA receptor subtypes expressed in IEC-6 cells
LPA2 is required for radiation induced DNA damage repair. To dissect the pathway downstream of LPA2
we used mouse embryonic fibroblasts (MEF) derived from LPA1&2 double knockout mice reconstituted
with the human LPA2 or an empty vector to perform a time course analysis of γH2AX following γ-
irradiation with or without LPA treatment. In the LPA2-MEF the levels of γH2AX decreased rapidly,
whereas in the vector-MEF high γH2AX level was sustained. Disrupting the LPA2/ERK1/2 and LPA2/AKT
signaling axis by the MEK1 inhibitor PD-98059 and the PI3K inhibitor LY-294002 respectively, abrogated
the augmentative effect of LPA on DNA-damage repair. These findings indicate that activation of AKT and
ERK1/2 are required for LPA2 facilitatation of DNA damage repair. In summary, radiation-induced
upregulation of LPA2 in gut epithelial cells inhibits cell death, promotes cell survival and DNA damage
repair making the LPA2 receptor a highly effective radiomitigator drug target. Supported by NIAD grant
AI-080405.
(PS7-21) Low dose radiation mitigates the malignant properties of breast cancer cells. Ki Moon Seong,
1
1
1
1
1
PhD ; Min-Jeong Kim, PhD ; Songwon Seo, MS ; Seong Bum Lee, PhD ; Won-Suk Jang, MS ; Su-Jae Lee,
1
1
1
2
PhD ; Sunhoo Park, MD, PhD ; Seung-Sook Lee, MD, PhD ; and Young Woo Jin, MD, PhD
National Radiation Emergency Medical Center, Korea Institute of Radiological & Medical Sciences, Seoul,
Korea, Republic of and Hanyang University, Seoul, Korea, Republic of
1
2
Insufficient understanding of the molecular effects of low levels of radiation exposure has leaded
to a great uncertainty regarding its health effects. Although there is an accumulating body of experimental
data less than 100 mSv, the cellular effects of low dose radiation (LDR) in normal cells shows a small
difference with much variation in each experimental sample, except for some specific cases. In order to
increase the consistency and coherence in LDR experimental data, lots of cellular and biochemical
approaches have been attempted. Here, we investigated the fractionated and single irradiated LDR effects
on the malignant properties of breast cancer cells. LDR irradiated cells were subjected to the conventional
Boyden chamber assay for migration and invasion analysis. Considering the importance of
microenvironment in cancer cells physiology, we also examined the malignancy of LDR irradiated cells
with the three dimensional (3D) culture systems, which is known to possess many features mimicking the
in vivo biological entities. In addition, LDR irradiated cells were evaluated the sensitivity to several anti-
cancer drugs. As a result, we found that both fractionated and single LDR irradiation decreased malignant
properties of breast cancer cells. For further characterization of these phenomena at the molecular level,
we performed the genome profile analysis through microarray. This study will be contributed to the
expansion of spectrum in biological phenotypes of LDR and suggest the possible physiological pathways
related to the LDR induced mitigated malignancy of breast cancer cells.
362 | P a g e
analysis of the lpa2 gene revealed the presence of an NF-κB binding site in the promoter region. The
radiation-induced upregulation was abolished by mutation of the NF-κB site. Pharmacological inhibition
of ATM/ATR kinases by CGK-733 also abrogated lpa2 upregulation, suggesting that lpa2 is a DNA damage
response gene, upregulated by ATM via NF-kB activation. To study the role of LPA2 activation in DNA
damage repair γH2AX level was monitored at different postradiation time points in IEC-6 cells. The level
of γH2AX peaked at 15-30 min after radiation, and showed a significantly faster resolution in LPA treated
cells compared to vehicle. The treatment of IEC-6 cells with an LPA2 specific antagonist inhibited the
resolution of γH2AX, suggesting that among the different LPA receptor subtypes expressed in IEC-6 cells
LPA2 is required for radiation induced DNA damage repair. To dissect the pathway downstream of LPA2
we used mouse embryonic fibroblasts (MEF) derived from LPA1&2 double knockout mice reconstituted
with the human LPA2 or an empty vector to perform a time course analysis of γH2AX following γ-
irradiation with or without LPA treatment. In the LPA2-MEF the levels of γH2AX decreased rapidly,
whereas in the vector-MEF high γH2AX level was sustained. Disrupting the LPA2/ERK1/2 and LPA2/AKT
signaling axis by the MEK1 inhibitor PD-98059 and the PI3K inhibitor LY-294002 respectively, abrogated
the augmentative effect of LPA on DNA-damage repair. These findings indicate that activation of AKT and
ERK1/2 are required for LPA2 facilitatation of DNA damage repair. In summary, radiation-induced
upregulation of LPA2 in gut epithelial cells inhibits cell death, promotes cell survival and DNA damage
repair making the LPA2 receptor a highly effective radiomitigator drug target. Supported by NIAD grant
AI-080405.
(PS7-21) Low dose radiation mitigates the malignant properties of breast cancer cells. Ki Moon Seong,
1
1
1
1
1
PhD ; Min-Jeong Kim, PhD ; Songwon Seo, MS ; Seong Bum Lee, PhD ; Won-Suk Jang, MS ; Su-Jae Lee,
1
1
1
2
PhD ; Sunhoo Park, MD, PhD ; Seung-Sook Lee, MD, PhD ; and Young Woo Jin, MD, PhD
National Radiation Emergency Medical Center, Korea Institute of Radiological & Medical Sciences, Seoul,
Korea, Republic of and Hanyang University, Seoul, Korea, Republic of
1
2
Insufficient understanding of the molecular effects of low levels of radiation exposure has leaded
to a great uncertainty regarding its health effects. Although there is an accumulating body of experimental
data less than 100 mSv, the cellular effects of low dose radiation (LDR) in normal cells shows a small
difference with much variation in each experimental sample, except for some specific cases. In order to
increase the consistency and coherence in LDR experimental data, lots of cellular and biochemical
approaches have been attempted. Here, we investigated the fractionated and single irradiated LDR effects
on the malignant properties of breast cancer cells. LDR irradiated cells were subjected to the conventional
Boyden chamber assay for migration and invasion analysis. Considering the importance of
microenvironment in cancer cells physiology, we also examined the malignancy of LDR irradiated cells
with the three dimensional (3D) culture systems, which is known to possess many features mimicking the
in vivo biological entities. In addition, LDR irradiated cells were evaluated the sensitivity to several anti-
cancer drugs. As a result, we found that both fractionated and single LDR irradiation decreased malignant
properties of breast cancer cells. For further characterization of these phenomena at the molecular level,
we performed the genome profile analysis through microarray. This study will be contributed to the
expansion of spectrum in biological phenotypes of LDR and suggest the possible physiological pathways
related to the LDR induced mitigated malignancy of breast cancer cells.
362 | P a g e
