Monte Carlo Simulation of the Effects of
Radiation Quality and Oxygen on
Clustered DNA Lesions
Robert D. Stewart,, Ph.D.
Associate Professor, Medical Physics
University of Washington Medical Center
Department of Radiation Oncology
1959 NE P
Pacific
ifi S
Street
Seattle, WA 98195-6043
206-598-7951 office
206-598-6218 fax
trawets@uw.edu
Presented at the 2011 Joint AAPM/COMP Meeting in Vancouver, Canada
Symposium: Predicting and Exploiting the Effects of Radiation Quality in Ion Therapy
Date : Tuesday August 2, 2011
Time: 4:30-6:00
4:30 6:00 pm
Location: Ballroom A
© University of Washington Department of Radiation Oncology
© University of Washington Department of Radiation Oncology
Learning Objectives
ƒ To review,
review understand and quantify the effects of
radiation quality and oxygen on the induction of
clustered DNA lesions by ionizing radiation
ƒ Highlight the close relationship between Double Strand
B k (DSB) Induction
Break
I d ti andd Reproductive
R
d ti Cell
C ll Death
D th
Presenter has no conflicts of interest to disclose
Slide 2
Slide 3
© University of Washington Department of Radiation Oncology
Clustered DNA lesions
Groups of several DNA lesions within one or two turns of the
DNA are termed clustered DNA lesions*
lesions*
+
=
lesion = damage to the sugar, base or phosphate
group of a single nucleotide
* Clustered DNA lesions are also referred to as locally multiply damaged sites
(LMDS), multiply damaged sites (MDS) or just “clusters
clusters”
Interesting Trivia: Over 1012 (!) possible types of clustered DNA lesion, i.e., the number of possible ways a 10 bp segment of DNA (20 nucleotides)
nucleotides)
20
12
single- and
can be damaged is on the order of 4 = 10 possible types of cluster. Most of the DNA clusters formed by ionizing radiation, including singledouble--strand breaks, are composed of 3 or more individual lesions.
double
© University of Washington Department of Radiation Oncology
Monte Carlo Damage Simulation (MCDS)
Developed to simulate number and smallsmall-scale spatial distribution of
lesions forming clusters (“nucleotide-level
(“
maps”)
”)
R.D.
R
D Stewart
Stewart, V.K.
V K Yu,
Yu A.G.
A G Georgakilas,
Georgakilas C.
C Koumenis,
Koumenis J.H.
J H Park,
Park D.J.
D J Carlson,
Carlson Monte Carlo Simulation of the Effects of
Radiation Quality and Oxygen Concentration on Clustered DNA Lesions. Accepted Radiat. Res. July 6, 2011.
Y Hsiao and R.D. Stewart, Monte Carlo Simulation of DNA Damage Induction by X-rays and Selected Radioisotopes.
Phys. Med. Biol. 53, 233-244 (2008)
V.A. Semenenko
k and
d R.D. Stewart. Fast Monte Carlo
l simulation
i l i off DNA damage
d
formed
f
d by
b electrons
l
andd light
li h ions.
i
Phys.
h
Med. Biol. 51(7), 1693-1706 (2006).
V.A. Semenenko and R.D. Stewart. A fast Monte Carlo algorithm to simulate the spectrum of DNA damages formed by
ionizing radiation. Radiat Res. 161(4), 451-457 (2004).
As of January 2011, the MCDS has been cited or used in at
least 28 peer
peer-reviewed
reviewed studies.
studies
Additional Information and Software Available at
http://faculty.washington.edu/trawets/mcds/
“trawets” = “stewart” backwards
Slide 4
Slide 5
© University of Washington Department of Radiation Oncology
Physics → Chemistry → Biology
Chemical
10-3 s Repair
1 Gy ~ 1 in 106
O2 fixation
Ionization
Excitation
Radiation
Correct
Repair
102 s
104 s
Enzymatic Repair
(BER, NER, NHEJ, …))
10-6 s
10-18 to 10-10 s
DNA
A damage
103 s
105 s
Incorrect or
Incomplete Repair
Cell Death
O2 fixation and chemical repair occur
on very (!
(!) different time scales than
biochemical repair and cell death
104 s
105 s
Small-- and largeSmall
large-scale mutations
(point mutations and chromosomal aberrations))
Slide 6
© University of Washington Department of Radiation Oncology
MCDS – General Features and Capabilities (1)
ƒ Spatial maps of the nucleotides forming many types of
clustered DNA lesion
• SSB, DSB, and individual or clustered base damages
• Information about cluster complexity
Simple DSB (2
( lesions))
C
Complex
l DSB (5
( llesions)
i
)
ƒ Individual particles or arbitrary mixtures of charged
particles up to and including 56Fe (new in 2011)
• Simulate damage from neutral particles using the distribution of secondary
charged particles (e.g., see Hsaio and Stewart, PMB 53, 233-244, 2008)
Slide 7
© University of Washington Department of Radiation Oncology
MCDS – General Features and Capabilities (2)
ƒ Simulates the effects on cluster formation of O2 fixation
and chemical repair (new in 2011) – “oxygen effects””
10-3
Chemical
s Repair
1 Gy ~ 1 in 106
O2 fixation
fi ti
Ionization
Excitation
Radiation
10-18 to 10-10 s
10-6 s
DNA damage
Slide 8
© University of Washington Department of Radiation Oncology
MCDS – General Features and Capabilities (3)
ƒ Particle and Dosimetric Information (new in 2011)
• Stopping power in water, CSDA range, absorbed dose per unit fluence, mean specific
energy, energy imparted per radiation event, and lineal energy
Particle
Type
e
-
1
H
4
2+
He
12 6+
C
16
MeV
MeV/u
S - S rad
(keV/μ m)
21.13
CSDA
Range
(μm)
2.56 x 10
-5
−
6.47 x 10
0.294
14.8
.8
-3
6.47 x 10
-2
7.35 x 10
1.23
. 3
34 2
34.2
2 x 10
0 28
0.28
186
6612
-3
-3
zF (Gy)
MCDS
Analytic
-11
0.17
-4
0 29
0.29
2.70
21.13
. 3
< 10
0.14
5.32
5.3
< 10
1.53
5.08
8+
38.1
2.38
711
42.03
6.01
5.86
10+
78.4
1750
3.92
31.3
792
1148
73.14
963.7
6.60
9.35
6.50
9.34
O
20
Kinetic Energy
Ne
56
26+
Fe
Analytic Formula: z F
= 0.204 [ S − Srad ] / ρ d 2
© University of Washington Department of Radiation Oncology
Chemical Basis of the Oxygen Effect
Competition between oxygen fixation and chemical repair is the
prevailing hypothesis (von
(
Sonntag 2006))
(1)) DNA + ionizing radiation → DNA lesion (biochemical
(
repair required))
(2)) DNA + ionizing radiation → DNA
DNA⋅⋅ (various))
Lesions and DNA radicals formed through direct and indirect interaction mechanisms
(3)) DNA
DNA⋅⋅ + O2 → DNA
DNA--O2 (“oxygen
oxygen fixation”
fixation – biochemical repair required))
(4)) DNA
DNA⋅⋅ + RSH → DNA (“chemical
(
repair” – restoration of the DNA*)
(5)) DNA
DNA⋅⋅ → DNA lesion (biochemical
(
repair required))
* Von Sonntag notes that donation of a proton to a DNA radical may or may not restore the original chemical structure
of the DNA. But, the chemical repair process evidently converts the DNA radical (or
( cluster of radicals?)) into a form that
is more amenable to biochemical repair and reduces the number of strand breaks.
Clemens von Sonntag, Free-Radical-Induced DNA Damage and its Repair – A chemical perspective. Springer-Verlag, New York, NY (2006)
Slide 9
Slide 10
© University of Washington Department of Radiation Oncology
RBE,, HRF and LQ Survival Parameters
RBE
Relative Biological
g
Effectiveness
(RBE
RBE)) for the ith type of cluster
Σi ( q )
RBEi ( q) =
Σi ( q0 )
Hypoxia Reduction Factor (HRF
(HRF)) for
the ith type of cluster
Σi ((100% O2 )
HRFi ([O2 ]) =
Σi ([O2 ])
Σi = Measured
M
d or MC simulated
i l t d number
b off th
the ith type
t
off cluster
l t Gy
G -1 Gbp
Gb -1 (or per cellll)
Trends in DSB induction with radiation quality and oxygen concentration are
closely related and predictive of general trends in LinearLinear-Quadratic (LQ) survival
parameters α and α/β (e.g., Carlson et al. 2008))
α ( q,[[O2 ]) = [θ + κ intra zF Σ dsb ( q,[[O2 ])] Σ dsb ( q,[[O2 ])
⎛ α ⎞ θ + κ intra zF ( q) Σ dsb ( q,[[O2 ])
⎜β ⎟ =
κ inter Σ dsb ( q,[O2 ])
⎝ ⎠q
D.J. Carlson, R.D. Stewart, V.A. Semenenko and G.A. Sandison, Combined use of Monte Carlo DNA damage simulations and deterministic repair models to examine putative mechanisms of cell killing. Rad. Res. 169, 447-459 (2008)
Slide 11
© University of Washington Department of Radiation Oncology
RBE for DSB Induction
3.5
3.5
3.0
RBE for DSB Induction
n
High LET
Electron
1 +
H
4
He2+
Photon
1 +
H
3
2+
4
2+
He and He
12 6+
C
56
Fe26+
2.5
Photons and electrons
1 +
H
4
He2+
12 6+
C
14 7+
N
16 8+
O
20
Ne10+
56
Fe26+
3.0
2.5
20
2.0
20
2.0
1.5
1.5
Low LET
1.0
1.0
C
Comparison
i
to
t ttrack
k structure
t t
simulations
i l ti
C
Comparison
i
to
t PFGE measurements
t
0.5
0.5
100
101
102
(Zeff /β)2
103
104 100
101
102
103
(Zeff /β)2
Many of the published experimental studies (symbols, right panel) detect a subset of
the total number of DSB because not all DNA fragments counted
104
Slide 12
© University of Washington Department of Radiation Oncology
HRF for DSB Induction
4.0
For low LET radiations, DSB
induction is about 33-fold lower under
maximallyy hypoxic
yp
conditions than in
well oxygenated cells (i.e.,
(
HRF ≅ 3).
).
HRF for DSB Indu
uction
3.5
3.0
25
2.5
HRF decreases towards unity
(O2 concentration has no effect))
as particle LET increases.
Low LET
2.0
1.5
Filled symbols are data from PFGE
experiments. Solid line is the MCDS
predicted HRF for a range of particle
types and energies.
1.0
High LET
0.5
Hypoxic (0.9-3% O2)
Maximally hypoxic (< 10-3% O2)
0.0
100
101
102
103
2
(Zeff/β)
104
Slide 13
© University of Washington Department of Radiation Oncology
HRF for Cell Survival and DSB Induction
4.0
Low LET
Solid Black Line: HRF for DSB
induction predicted by the MCDS (0%
O2 concentration)
i )
RT with 12C
(RBE < 3 to 9)
3.5
HRF
3.0
Symbols: HRF derived from published
clonogenic survival data (negligible O2
concentration)
2.5
Proton RT
(RBE < 1.3 to 1.5)
2.0
α H = α A / HRFα
(α / β ) H = (α / β ) A ⋅ HRFα / β
Photons
Ions
3
He - V79
3
He - HSG
12
C - V79
12
C - HSG
20
Ne - V79
20
Ne - HSG
1.5
1.0
HRFα ≅ HRFα / β
High LET
0.5
100
101
102
(Zeff/β)2
103
104
Slide 14
© University of Washington Department of Radiation Oncology
Effect of Oxygen Concentration on the HRF
40
4.0
60
Co and 10/15 MV X-rays
10 MV X-rays
60
Co
137
Cs
200 280 kV
200-280
kVp X
X-rays
50 kVp X-rays
3.5
60Co
HRF
3.0
Symbols:
S
b l HRF derived
d i d from
f
published clonogenic survival data
29 kVp
x-ray
2.5
Solid, dotted and dashed black
lines: HRF for DSB induction
ppredicted byy the MCDS for selected
particle types
0.76 MeV p
2.0
8.3 MeV α
1.5
146.4 MeV 12C
1.0
0.5
10-4
10-3
10-2
10-1
100
101
Oxygen Concentration (%)
102
© University of Washington Department of Radiation Oncology
Conclusions
ƒ For the first time
time,, possible to determine nucleotidenucleotide-level
maps of cluster induction under reduced oxygen
conditions
• Good agreement with data from other published studies for a wide range
of oxygen concentrations and ion types (e- to 56Fe) – (Zeff/β)2 in range
from 1 to 10,000
ƒ RBE and HRF derived from clonogenic survival data in
good
d agreementt with
ith RBE andd HRF for
f DSB induction
i d ti
• Additional, albeit indirect, evidence to support the hypothesis that DSB
are one of the most biologically
g
y significant
g
forms of clustered DNA lesion
ƒ
12C
ions much more effective at overcoming effects of
hypoxia
yp
in RT than p
protons ((or pphotons))
Slide 15
© University of Washington Department of Radiation Oncology
Acknowledgements
ƒ David J.
J Carlson,
Carlson Ph.D.
Ph D Assistant Professor
Professor, Department of
Therapeutic Radiology, Yale School of Medicine
ƒ Alexandros Georgakilas,
g
Ph.D. Associate Professor, Department
Ph.D.,
p
of
Biology, East Carolina University
ƒ Costas Koumenis, Ph.D.,
Ph.D. Associate Professor, Department of
R di ti Oncology,
Radiation
O l
University
U i
it off Pennsylvania
P
l i School
S h l off Medicine
M di i
ƒ Vladimir A. Semenenko, Ph.D.,
Ph.D. Instructor, Medical College of
Wisconsin Department of Radiation Oncology,
Wisconsin,
Oncology Milwaukee,
Milwaukee WI
ƒ Anshuman Panda
Panda,, Ph.D. Student,, Purdue 2011
ƒ Joo Han Park,
Park Ph.D. Student, Purdue 2011
ƒ Victor Yu – MS student, Purdue 2010
Slide 16