Page 130 - 2014 Printable Abstract Book
P. 130
HMy2.CIR (mp53) to different LET irradiations. It was found that the mitochondrial dysfunction, p66
activation and ROS were enhanced in TK6 but not in HMy2.CIR cells after γ-ray irradiation, but all of them
were increased in both cell lines after carbon and iron irradiation. Consistently, the bystander effect of
MN formation in HL-7702 cells was only triggered by γ-irradiated TK6 cells but not by γ-irradiated
HMy2.CIR cells; but these bystander effects were induced by both lymphocyte cell lines after heavy ion
irradiations. PFT-m, an inhibitor of p53, only partly inhibited ROS generation and bystander effect induced
by 30 keV/mm carbon-irradiated TK6 cells but failed to suppress the bystander effect triggered by both
70 keV/mm carbon and 180 keV/mm iron irradiations. The mitochondrial inhibitors of rotenone and
oligomycin eliminated heavy ion induced ROS generation in TK6 and HMy2.CIR cells and hence diminished
the bystander effect on HL-7702 cells. These results clearly demonstrate that the bystander effect is p53-
dependent for low LET irradiation but is independent of p53 of the targeted cells for high LET irradiation
because of a p53-independent ROS generation via mitochondrial dysfunction.
(PS1-51) The role of the TGF-β1-miR21-ROS pathway in radiation-induced bystander responses. Youqin
Jiang; Xian Chen; Wenqian Tian; Xiaoming Yin; Jingdong Wang; Hongying Yang, PhD, Soochow University,
Suzhou, China
With the accumulation of evidence for radiation-induced bystander effects (RIBEs) in normal and
cancer cells in vitro and in vivo, it is more urgent than ever to elucidate the underlying mechanisms in
terms of their impact on radiation risk assessment and potential implications in radiotherapy. Although
some factors, such as intercellular gap junctions, reactive oxygen species (ROS), and cytokines, have been
demonstrated to mediate RIBEs, the detailed signaling pathways are poorly understood. In this study, we
found that while radiation-conditioned medium (RCM) harvested from irradiated H1299 human non-
small-cell lung cancer cells 1 h post-radiation (1 h RCM) caused oxidative stress and DNA damage in
bystander cells, RCM harvested 18 h after irradiation (18 h RCM) induced cell cycle delay and proliferation
inhibition. This indicates that irradiated cells release different bystander signals at different times after
irradiation. Moreover, when a specific inhibitor of the TGF-β1 signaling pathway, SB 431542, was added
to irradiated cells prior to irradiation or into RCM, all bystander responses were eliminated, suggesting
that the TGF-β1 pathway in both irradiated and bystander cells is critical to the induction of RIBEs. More
interestingly, 1 h RCM and 18 h RCM induced up-regulation and down-regulation of miR-21 expression in
bystander cells, respectively. Additionally, miR-21 dysregulation was attenuated by SB 431542, suggesting
that miR-21 in bystander cells is dependent on the TGF-β1 pathway. Furthermore, transfection of a miR-
21 inhibitor into bystander cells abolished the increase in the intracellular ROS level and DNA damage
caused by 1 h RCM, and transfection of a miR-21 mimic eliminated proliferation inhibition caused by 18 h
RCM. The results indicate that miR-21 is not only a manifestation of RIBEs, but also an important mediator
of RIBEs. Taken together, the results reveal an important mediating role of the TGF-β1-miR-21-ROS
pathway of bystander cells in bystander signaling.
128 | P a g e
activation and ROS were enhanced in TK6 but not in HMy2.CIR cells after γ-ray irradiation, but all of them
were increased in both cell lines after carbon and iron irradiation. Consistently, the bystander effect of
MN formation in HL-7702 cells was only triggered by γ-irradiated TK6 cells but not by γ-irradiated
HMy2.CIR cells; but these bystander effects were induced by both lymphocyte cell lines after heavy ion
irradiations. PFT-m, an inhibitor of p53, only partly inhibited ROS generation and bystander effect induced
by 30 keV/mm carbon-irradiated TK6 cells but failed to suppress the bystander effect triggered by both
70 keV/mm carbon and 180 keV/mm iron irradiations. The mitochondrial inhibitors of rotenone and
oligomycin eliminated heavy ion induced ROS generation in TK6 and HMy2.CIR cells and hence diminished
the bystander effect on HL-7702 cells. These results clearly demonstrate that the bystander effect is p53-
dependent for low LET irradiation but is independent of p53 of the targeted cells for high LET irradiation
because of a p53-independent ROS generation via mitochondrial dysfunction.
(PS1-51) The role of the TGF-β1-miR21-ROS pathway in radiation-induced bystander responses. Youqin
Jiang; Xian Chen; Wenqian Tian; Xiaoming Yin; Jingdong Wang; Hongying Yang, PhD, Soochow University,
Suzhou, China
With the accumulation of evidence for radiation-induced bystander effects (RIBEs) in normal and
cancer cells in vitro and in vivo, it is more urgent than ever to elucidate the underlying mechanisms in
terms of their impact on radiation risk assessment and potential implications in radiotherapy. Although
some factors, such as intercellular gap junctions, reactive oxygen species (ROS), and cytokines, have been
demonstrated to mediate RIBEs, the detailed signaling pathways are poorly understood. In this study, we
found that while radiation-conditioned medium (RCM) harvested from irradiated H1299 human non-
small-cell lung cancer cells 1 h post-radiation (1 h RCM) caused oxidative stress and DNA damage in
bystander cells, RCM harvested 18 h after irradiation (18 h RCM) induced cell cycle delay and proliferation
inhibition. This indicates that irradiated cells release different bystander signals at different times after
irradiation. Moreover, when a specific inhibitor of the TGF-β1 signaling pathway, SB 431542, was added
to irradiated cells prior to irradiation or into RCM, all bystander responses were eliminated, suggesting
that the TGF-β1 pathway in both irradiated and bystander cells is critical to the induction of RIBEs. More
interestingly, 1 h RCM and 18 h RCM induced up-regulation and down-regulation of miR-21 expression in
bystander cells, respectively. Additionally, miR-21 dysregulation was attenuated by SB 431542, suggesting
that miR-21 in bystander cells is dependent on the TGF-β1 pathway. Furthermore, transfection of a miR-
21 inhibitor into bystander cells abolished the increase in the intracellular ROS level and DNA damage
caused by 1 h RCM, and transfection of a miR-21 mimic eliminated proliferation inhibition caused by 18 h
RCM. The results indicate that miR-21 is not only a manifestation of RIBEs, but also an important mediator
of RIBEs. Taken together, the results reveal an important mediating role of the TGF-β1-miR-21-ROS
pathway of bystander cells in bystander signaling.
128 | P a g e
