Transcript 11.45-12.30 Exploring ENP Effects in Animal Cancer Models and

Håkan Wallin
Håkan Wallin
Carcinogenic and mutagenic effects of engineered
nanomaterials
Exposure to insoluble particles is a cause
of serious lung disease
• Because cancer takes decades to develop, we wish to
remove carcinogens before we detect human cancer
• It is notoriously insensitive
• Confounders are all over
What is the problem with insoluble
particles?
What is the problem with insoluble
particles?
-Thorotrast, 3-10 nm thorium dioxide
nanoparticles, was used as a radiographic
contrast agent in the 1930s to the 1950s
What is the problem with insoluble
particles?
-Thorotrast, 3-10 nm thorium dioxide
nanoparticles, was used as a radiographic
contrast agent in the 1930s to the 1950s
- The accumulated liver cancer incidence in
patients injected with Thorotrast was 80%
What is the problem with insoluble
particles?
-Thorotrast, 3-10 nm thorium dioxide
nanoparticles, was used as a radiographic
contrast agent in the 1930s to the 1950s
- The accumulated liver cancer incidence in
patients injected with Thorotrast was 80%
The problem with Thorotrast was that it
-was extremely insoluble particles that
were not excreted
-it was accumulated in phagocytic cells in
the liver and spleen
-it consisted of α-emmitting 232Th
One nanoparticle is not another
nanoparticle
We need to be observant on
chemicals that are
persistant (in the body and
noparticle
environment) and
accumulate in food chains
We need to be observant on
chemicals that are
Onepersistant
nanoparticle
is body
not another
(in the
and
environment)
and
nanoparticle
accumulate in food chains
We need to be observant on
chemicals that are
persistant (in the body and
noparticle
environment) and
accumulate in food chains
We
need
to
be
observant
on
We need to be observant on
chemicals
that
are
chemicals that are
persistant
(in
the
body
and
persistant
(in the body and
noparticle
environment)
and
environment) and
accumulate
in
food
chains
accumulate in food chains
We need to be observant on
chemicals that are
Onepersistant
nanoparticle
is body
not another
(in the
and
environment)
and
nanoparticle
accumulate in food chains
Our understanding of cancer risk
Epidemiology
Long-term animal testing
Cancer epidemiology
..1,2,3,4…
Problems with cancer epidemiology
• Because cancer takes decades to develop, we wish to
remove carcinogens before we detect human cancer
• It is notoriously insensitive
• Confounders are all over
Animal cancer tests
..1,2,3,4…
Rational for doing animal tests
All human carcinogens are rodent
carcinogens when tested
appropriately
Public acceptance
Problems with cancer rodent tests
• Is man a mouse?
• Animals are given high doses/Man is
exposed at low
• Man is exposed to many things/
Mouse to few
• Mouse is inbred/Man not (usually)
Chemical Carcinogenesis Rodent Models
Most common strains used include
• Rats: Fischer 344; SpragueDawley; Charles River CD; Wistar;
Nobel
• Mice: B6C3F1; C57Bl6; ICR Swiss
albino; Charles River CD-1
General Experimental Bioassay
Conditions
National Toxicology Program
Species/Strain
Rats
Mice
Numbers/Group
Fischer 344/N
B6C3F1
50-60
Exposures
Gavage
Vehicle
Inhalation
Feed
MTD + 2-3, controls
5 per week
Corn oil
6 hrs/d/5d/wk
continuous
Age at start
Duration
6 - 8 weeks
104 weeks
Two-Year Chemical Carcinogenesis
Bioassays
Year
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
Chemicals
24
44
55
43
15
9
21
8
6
8
9
14
Year
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Chemicals
10
4
9
4
4
13
7
10
9
8
7
7
• In the eighties diesel exhaust was
tested for carcinogenic effects in
Germany and USA
• Carbon black was used as an inert
control exposure
Oh yea, -but
I’m in the
fresh air
control group
• Carbon black was nearly as
effective in causing lung cancer
despite carbon black i virtually
devoid of extractable
chemicals
No conclusive
and heavy metals
epidemiologic evidence
for carcinogenicity
Carbon black
• World production in 2006 - 8.1 million
tonnes
• Rubber
• Pigment in paints and printing inks
• Typical exposures in industry 0.2-1
mg/m3
Toxicity=surface area×particle
specific activity
Despite workers in the industry
have been highly exposed (some
to mean of 5 mg/m3 for over
many y)
-no excess cancer incidence has
Despite workers in the industry
One
nanoparticle
is
not
another
have been highly exposed (some
nanoparticle
to mean of 5 mg/m3 for over
many y)
-no excess cancer incidence has
Mechanisms of carcinogenesis
Mutagens are carcinogens
Carcinogens are mutagens (most of
the time)
100% with tumor
50%
Risk estimate
0%
Dose (mg/kg/day)
FE1 lung epithelial cell
line established from
the Mutamouse
Test setup
Total exposure time (8x72h) 24d;
Length of experiment (9x96h) 36h; Total dose either 6 or 8 mg;
300
200
100
0
CB
DEP
SiO2 SWCNT/C60
C60 SWCNT SiO2
100 100
100
DEP DEP CB
37,5 75
75 μg/ml
Promotion
Toxicity
Fiber carcinogenesis
Immunosuppression
Inflammation
Fiber carcinogenesis
Foreign body carcinogenesis
Promotion
Toxicity
Fiber carcinogenesis
Immunosuppression
Inflammation
Fiber carcinogenesis
Foreign body carcinogenesis
Already in 1863, Virschow proposed that cancer
develops at sites of chronic inflammation.
This was based on observations that some
tissue irritants, tissue damage and ensuing
inflammation enhance tissue proliferation
Chronic inflammatory conditions associated
with neoplasms
Bronchitis
Lung carcinoma
Crohn’s- disease
inflammatory
bowel disease, ulcerative
colitis
Colorectal cancer
Hepatitis
Liver cancer
Carcinogenic infections agents
Hepatitis B and C virus
Liver cancer
Helicobacter pyloris
Gastric cancer
Schistosoma heamotobium
Bladder cancer
Poorly soluble-low toxicity particles such as TiO2
Carbon black
Is genotoxicity dependent of inflammation
Or is an independent particle effect
Proliferation alone is not a requisite for cells
to cause cancer
Inflammation may be directly genotoxic e.g. ROS
derived from inflammatory cells
An environment rich in inflammatory cells, growth
factors, and activated stroma may foster
carcinogenesis
Inflammation may change the microenvironment
around initiated cells to promote proliferation,
invasion, angiogenesis, apoptosis and metastasis
Promotion
Toxicity
Fiber carcinogenesis
Immunosuppression
Inflammation
Fiber carcinogenesis
Foreign body carcinogenesis
Foreign bodies sometimes induce
cancer in humans.
Examples are prostetic, reconstructive,
cosmetic materials implanted
Accidental: bullets scrapnels at war
Animal experiments
plastic materials
metallic
ceramic
Tumor induction of imnplant affected by
-size
-shape
-porosity
-hardness
-surface charge
Mechanims
Cells i new tissues around are
transformed
Scar tissue secrete signalling
molecules that stimulate local
carcinogenesis
•Common ground nano micro
macro
-Persistent inflammation
-Granulomas
-Fibrosis (scarring) –
Giant cells (large
multinucleated macrophages)
Promotion
Toxicity
Fiber carcinogenesis
Immunosuppression
Inflammation
Fiber carcinogenesis
Foreign body carcinogenesis
Fiber length >5 μm
Aspect ratio >3/1
Dustiness
Another aspect of
nanoparticles
Schneider & Jensen et al., 2008
Dustiness
Schneider & Jensen et al., 2008
Dustiness
Schneider & Jensen et al., 2008
What is the problem with
nanoparticles?
–
–
–
–
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62
Deposition
Surface area
Clearence
Translocation
Dustiness
Der Spiegel 18/2009 page 133
Thanks to….
National Research Centre for the Working
Environment: Nicklas Raun Jacobsen, Anne T. Saber,
Corey Cohn, Alstrup Jensen, Asger W. Nørgaard,
Thomas Schneider,
Health Canada:
Paul White, John Gingerich
University of Copenhagen:
Peter Møller, Steffen Loft
Danish Food Research
Ulla Vogel
University of Venice:
Giulio Pojana, Antonio Marcomini
Questions
Possible mechanisms:
1. Less access to
microvasculature
2. Poorer diffusional supply of
materials
3. Reduced cell contact
inhibition
4. Difference in chemical and
electrical environments
Risk assessment
(1)
(2)
(3)
(4)
Hazard identification
Dose-response assessment
Exposure assessment
Risk characterization
Pulmonary deposition of fibers in man as a
function of physical dimensions
Mast et al. Inhalation Toxicol 12:359-399