Computational Methods in Systems Biology

(Ann) #1
A Scheme for Adaptive Selection of Population Sizes 141

0 10000
Distance

0. 0

0. 5

1. 0

Empirical density

× 10 −^3
True
MAP
1.0

3.0
divL

True

-3.0

-1.0
divkmax

-5.0

0.0
degke

-5.0

0.0
dive

-5.0

0.0
proke

-5.0

0.0
initq

1.0Ldiv 3.0

0.0

1.2
L
init

-3.0kmaxdiv -1.0-5.0kdege 0.0-5.0ediv 0.0-5.0kproe 0.0-5.0qinit 0.00.0Linit 1.2

Generationt=40

Generationt=13 log 10 parameters

log

10

parameters

a

0 10 20
Timet(d)

250

500

750

Spheroid
radius (

μm

)

0 500
Distance to
spheroid rim (μm)

0. 0

0. 2

0. 4

Fraction ofproliferating

cells

0 500
Distance to
spheroid rim (μm)

0

1

Extracellular

matrixintensity

b c

0 40
Generationt

102

104

106

108

Acceptancethreshold



0 40
Generationt

0

200

Population size

n neff

d 1

d 2

Fig. 4. Multiscale tumor growth model. (a)Tumor growth data. 100 samples
from the reference parameters listed in [ 9 ]. The data were: (1) the spheroid radius
over time, (2) the fraction of proliferating cells over distance to the spheroid rim, and
(3) the extracellular matrix intensity over distance to the spheroid rim.(b)Posterior
distributions obtained from an adaptive population size ABC-SMC run withECV=
0 .25. Axis limits correspond to the support of the uniform prior. The purple crosses
and dashed lines “True” indicate the reference parameters. Lower triangle: distribution
of generationt= 13. Upper triangle: distribution of generationt= 40. Diagonal:
distributions across the generations: light to dark: earlier to later generations.(c)
Distribution of distances to the observed datasdatawhich was obtained as average
of 100 samples from the reference parameter values [ 9 ]. True (black): Distances of
the same 100 samples which were used to generate the observed datasdata.MAP
(orange): Distances of 100 samples from the maximum a posteriori parameters.(d)
(d 1 ) Acceptance threshold;(d 2 ) Population sizenand effective population sizeneff
for (b). At generationt,is set to the median of the observation–particle distances of
generationt−1. (Color figure online)

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