Page 273 - 2014 Printable Abstract Book
P. 273
(PS4-65) An age-associated metabolic-shift from glycolysis to mitochondrial respiration controls
radiation injury in normal cells. Jyungmean Son; Wusheng Xiao; Ehab H. Sarsour; Brett A. Wagner; Garry
R. Buettner; and Prabhat C. Goswami, University of Iowa, Iowa city, IA
Aging is a critical risk factor for numerous health issues and positive therapeutic outcomes. The
redox stress hypothesis of aging postulates that age-associated functional losses are primarily caused by
a progressive shift to a more oxidized redox environment of cells, which leads to the over-oxidation of
redox-sensitive protein thiols and subsequent disruption of redox-regulated signaling mechanisms. In this
study we investigated the role of cellular metabolism in the response of normal human fibroblasts (NHF)
to age-associated oxidative stress. We show that NHF representative of older (61-year) individuals are
more sensitive to oxidative stress induced by ionizing radiation compared to NHF representative of
younger (3-day) individuals. Examination of cellular metabolism using a Seahorse XF96 instrument
revealed a decreased extracellular acidification rate (ECAR, glycolysis) and increased oxygen consumption
(OCR, mitochondrial respiration) in old compared to young NHF. Results obtained from RT2 Profiler
Human Glucose Metabolism PCR Arrays and quantitative RT-PCR assays showed significant decreases in
the levels of mRNA of genes involved in the rate-limiting steps of glycolysis and the pentose phosphate
pathway (PPP) in old compared to young NHF: hexokinase 2 (HK2; 2-fold), phos-phofructokinase 1 (PFK1;
4.5-fold), and glucose-6-phosphate dehydrogenase (G6PD; 2-fold). Because G6PD regulates the rate-
limiting step of the PPP and the PPP supports a reducing environment (increased glutathione levels and/or
more reduced redox status), our results suggest that a decrease in G6PD expression combined with an
increase in mitochondrial respiration contributes to the age-associated oxidative stress response of
normal human fibroblasts. (Supported by NIH 2R01CA111365.)
(PS4-66) Response of canine tumor cells to perfusion deficit-related hypoxia following single fraction,
1
1
1
high dose irradiation. Katy L. Swancutt, BS ; James T. Custis, D.V.M., MS ; Howard L. Liber, PhD ; Richard
1
2
1
Kolesnick, MD ; and Susan M. LaRue, D.V.M., PhD, Colorado State University, Fort Collins, CO and
2
Memorial Sloan-Kettering Cancer Center, New York, NY
Stereotactic radiation therapy (SRT, a.k.a. stereotactic radiosurgery, stereotactic body radiation
therapy, or stereotactic ablative radiation therapy), in which one to five high-dose fractions of ionizing
radiation are utilized with high precision to treat a variety of tumor types, has become an increasingly
common therapeutic modality. The use of single/few fractions of high doses deviates strongly from the
established, Coutard-era paradigm utilizing numerous fractions of small doses. The surprisingly successful
clinical outcomes arising from SRT have initiated debate regarding the role of classical radiobiological
modeling as well as potential mechanistic differences in single fraction, high-dose irradiation. Recent
studies by the Kolesnick lab indicated that exposure to a single fraction of high-dose ionizing radiation
induces a significant decrease in perfusion in human tumor xenografts on mice. We are currently studying
such perfusion changes in spontaneously occurring tumors in dogs, which have inherent characteristics
such as increased heterogeneity that make canine tumors superior models for human cancers. Such a
perfusion deficit could inevitably increase the severity of hypoxia within a tumor, possibly leading to
impaired repair of radiation-induced double-strand breaks in tumor cell DNA. In order to study the effects
of such a perfusion deficit on tumor parenchyma, we developed an in vitro model in which single fractions
of high dose radiation combined with subsequent (not concurrent hypoxia, for which the science is well
established) induction of severe hypoxia were used to mimic the conditions described in previous work
271 | P a g e
radiation injury in normal cells. Jyungmean Son; Wusheng Xiao; Ehab H. Sarsour; Brett A. Wagner; Garry
R. Buettner; and Prabhat C. Goswami, University of Iowa, Iowa city, IA
Aging is a critical risk factor for numerous health issues and positive therapeutic outcomes. The
redox stress hypothesis of aging postulates that age-associated functional losses are primarily caused by
a progressive shift to a more oxidized redox environment of cells, which leads to the over-oxidation of
redox-sensitive protein thiols and subsequent disruption of redox-regulated signaling mechanisms. In this
study we investigated the role of cellular metabolism in the response of normal human fibroblasts (NHF)
to age-associated oxidative stress. We show that NHF representative of older (61-year) individuals are
more sensitive to oxidative stress induced by ionizing radiation compared to NHF representative of
younger (3-day) individuals. Examination of cellular metabolism using a Seahorse XF96 instrument
revealed a decreased extracellular acidification rate (ECAR, glycolysis) and increased oxygen consumption
(OCR, mitochondrial respiration) in old compared to young NHF. Results obtained from RT2 Profiler
Human Glucose Metabolism PCR Arrays and quantitative RT-PCR assays showed significant decreases in
the levels of mRNA of genes involved in the rate-limiting steps of glycolysis and the pentose phosphate
pathway (PPP) in old compared to young NHF: hexokinase 2 (HK2; 2-fold), phos-phofructokinase 1 (PFK1;
4.5-fold), and glucose-6-phosphate dehydrogenase (G6PD; 2-fold). Because G6PD regulates the rate-
limiting step of the PPP and the PPP supports a reducing environment (increased glutathione levels and/or
more reduced redox status), our results suggest that a decrease in G6PD expression combined with an
increase in mitochondrial respiration contributes to the age-associated oxidative stress response of
normal human fibroblasts. (Supported by NIH 2R01CA111365.)
(PS4-66) Response of canine tumor cells to perfusion deficit-related hypoxia following single fraction,
1
1
1
high dose irradiation. Katy L. Swancutt, BS ; James T. Custis, D.V.M., MS ; Howard L. Liber, PhD ; Richard
1
2
1
Kolesnick, MD ; and Susan M. LaRue, D.V.M., PhD, Colorado State University, Fort Collins, CO and
2
Memorial Sloan-Kettering Cancer Center, New York, NY
Stereotactic radiation therapy (SRT, a.k.a. stereotactic radiosurgery, stereotactic body radiation
therapy, or stereotactic ablative radiation therapy), in which one to five high-dose fractions of ionizing
radiation are utilized with high precision to treat a variety of tumor types, has become an increasingly
common therapeutic modality. The use of single/few fractions of high doses deviates strongly from the
established, Coutard-era paradigm utilizing numerous fractions of small doses. The surprisingly successful
clinical outcomes arising from SRT have initiated debate regarding the role of classical radiobiological
modeling as well as potential mechanistic differences in single fraction, high-dose irradiation. Recent
studies by the Kolesnick lab indicated that exposure to a single fraction of high-dose ionizing radiation
induces a significant decrease in perfusion in human tumor xenografts on mice. We are currently studying
such perfusion changes in spontaneously occurring tumors in dogs, which have inherent characteristics
such as increased heterogeneity that make canine tumors superior models for human cancers. Such a
perfusion deficit could inevitably increase the severity of hypoxia within a tumor, possibly leading to
impaired repair of radiation-induced double-strand breaks in tumor cell DNA. In order to study the effects
of such a perfusion deficit on tumor parenchyma, we developed an in vitro model in which single fractions
of high dose radiation combined with subsequent (not concurrent hypoxia, for which the science is well
established) induction of severe hypoxia were used to mimic the conditions described in previous work
271 | P a g e
