16 06 17 Bologna Metals and K [modalità compatibilità]

28/06/2016
From GENETICS to EPIGENETICS
.. to Primary Prevention
ERNESTO BURGIO
ISDE Scientific Committee
ECERI - European Cancer and
Environment Research Institute
Relative frequency of articles with epigenetic or epigenetics in their title
David Haig Int. J. Epidemiol. 2012;41:13-16
Foreword 1
1
28/06/2016
The rate of increase
of genome-scale
publications
addressing cancer
genetics has
become greater
than that of
publications
in the same area
focused
on selected genes
In the past 10 years, according to
PubMed, 22 277 articles with the word
obesity in the title have been published. If
the search is extended to articles with
obesity in the title or abstract, the
number triples to 66 159
Lancet (2011) 378(9793):760
Number of New York Times articles mentioning obesity and related comorbidities
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A quick search for “Microbiome” in scienctific journals online demonstrates how significantly this
field of research has been growing over the past ten years
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Published papers about endocrine disruptors
between 1993 and november 2006 (Gies)
Colborn, vom Saal, Soto (1993): EHP
endocrine disruptors
Fetal programming
3
Ontogeny
4
Developmental Plasticity
Evolutionary Medicine
Phylogeny
5
Devo-Evo
Mismatch
6
7
2
Environment
1
From Genetics
to Epigenetics
Is there a Project ?
XXI Century
Epidemiological
Transition
La transizione epidemiologica del XX
secolo: dalla genetica all'epigenetica
ERNESTO BURGIO
ISDE Scientific Committee
ECERI - European Cancer and
Environment Research Institute
4
28/06/2016
We are currently facing a paradigm shift in biomedicine
For the last 50 years it was agreed to consider DNA as the code
and the key project for the assembly of our phenotype.
In the last ten years and especially since the appearance of the first
molecular epigenetic studies we have begun to understand
that the construction of the phenotype is the result of the interaction
between the information coming from the environment
and the information deeply inscribed inside the DNA
thanks to a very complex molecular network
surrounding DNA: the epigenome
Therefore it can be argued that there is no stable change in our
phenotype (both physiological and pathological) which is not
- environmentally induced
- modulated by the epigenome
- conditioned by the DNA
Other key concepts (obviously interdependent) are:
- developmental plasticity
- fetal programming
allow ing us to understand how the fetus epigenetically program
(for life) all its cells in a predictive and adaptive way
responding to information coming from the environment
(through the mother bias )
It is important to note that in this period
incorrect information ( pollutants, endocrine disruptors ..) and /or
discrepancies between the information that the baby receives before and after
birth (mismatch)
may create epigenetically bad programmed cells (including gametes), thus
causing chronic diseases in adulthood or even in subsequent generations
This theory (DOHaD Developmental Origins of Health and Disease)
could help us to explain the current epidemiological transition ..
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28/06/2016
The first keyword: Epigenetics
Mitotic chromosome
Heterochromatin
to recognize
in the study
of
epigenetics
the most
appropriate
and
powerful
tool to build
up a new
systemic
and
molecular
model of
genome ..
finally
understood
as a
dynamic
and fluid
network
which can
interact
inside itself
and with
the
outside
Euchromatin
Interphase chromosomes
Le Dogme Central de Crick: Une fois l'information a
pénétré dans une protéine ne peut pas sortir à
nouveau (one direction-linear flow of information)
Pour citer le biologiste moléculaire Richard C. Strohmann : l'ère de Watson et Crick, qui a commencé comme
une théorie du gène a évolué à tort dans une théorie et le paradigme de la vie: c'est a dire,
dans une forme revivifiée et soigneusement moléculaire du déterminisme génétique
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28/06/2016
From directing the fate of stem cells to determining how.. we grow, the genes in our body
act in complex networks.. the whole Genome is a Complex and highly dynamic molecular
Network of interacting Genes and non-codifying sequences.. and proteins
….Genes Know How to Network…BUT...
http://news.sciencemag.org/sciencenow/2009/04/21-03.html
Strohman R. , April 2001 Beyond genetic determinism
IN FACT Genes need to be told
to switch “off” and “on”:
• Genes need to be told how much expression
(protein) is required and where.
• Genes need to be regulated – this regulation is not
performed by DNA but by many other controls
arranged in a complex network
• DNA has been called the Book of Life by the Human
Genome Project scientists, but many other biologists
consider DNA to be simply a random collection of
words from which a meaningful story of life may be
assembled…
• In order to assemble that meaningful story, a living
cell uses a second informational system. (...) The key
concept here is that these dynamic-epigenetic
networks have a life of their own —they
follow network-rules not specified by DNA
In such a fluid and systemic model the epigenome (also defined by some scientists as the
controlling software of the genome) behaves as a sort of compensation chamber - the specific
place where the flow of information that comes from outside (environment and microenvironment)
meets and interacts with the information encoded in the genes for millions years (the hardware)
Rudolf Jaenisch- Whitehead Institute and
Dept. of Biology, MIT, Cambridge, MA
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28/06/2016
EMF
The second keyword: Environment
We may represent the environment as a continuous
stream of information (simple: photons: individual
packages of E = M = Information) or complex (organic
molecules, viruses etc) interacting with our cells
[membrane /transmembrane receptors, signal
transduction proteins, nuclear receptors, genome
(DNA + Epigenome)] forcing them to adapt
TCDD
Viruses
1
SYNERGISM !!
3
2
“FLUID EPI-GENOME”
HERVs
4
Everyday levels matter
At high levels… arsenic kills people
At moderately low levels… it causes a range of diseases
At truly low levels …
it interferes with gene
activation
Many of these substances (Dioxins,
Heavy Metals, Polycyclic aromatic
Hydrocarbons) are dangerous for
humans health at very low-every daydoses (which are very difficult to be
assessed by the ordinary toxicological
studies)
Kaltreider et al. 2002
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Histone Tails
are subject to
a variety of
covalent
modifications
Histone Code” hypothesis:
modifications
of the Histone tails
act as marks read
by other proteins
to control the
expression
or replication of
chromosomal regions
E.g. generally,
Histone Acetylation
is associated with
transcriptionally
active genes
Deacetylation
is associated with
inactive genes
(= gene silencing)
The “meeting-point” between the information coming from the
environment and the information encoded in the DNA
(hardware) is the epigenome (software): mimetic molecules
(EDCs) and other pollutants or danger-signals induce the
epigenome to change
Histone Acetyltransferases;
Histone Methyltransferases
Histone Deacetylases.
Histone
Lysine
Acetylation
P
H3-K9
Nuclear Receptor
DNA Response Element
H3-S10
Many toxicants cause
rapid alterations in gene
expression by activating
protein kinase signaling
cascades.
The resulting rapid,
defensive alterations in
gene activity require the
transmission of a signal
directly to the histones
present in the chromatin
of stress response genes:
within minutes
of exposure
the phosphorylation of
serine 10 of histone H3
and the
acetylation
of lysines 9 and/or 14
take place
ATP-dependent Nucleosome
Remodeling Complex
Chromatin itself is the direct target of many toxicants *
… toxicant-induced perturbations in chromatin structure
may precipitate adverse effects.. Forcing genome to change
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DNA methylation
Covalent modification of the DNA is also important for gene silencing human cells.
Most genes have GC rich areas of DNA in their promoter regions, referred to as CpG islands.
Methylation of the C residues within the CpG islands leads to gene silencing
2
(highly unstable
base)
The presence of 5-methylcytosine leads to the silencing
of genes in that local area of the chromosome
1
2
MT = DNA methyltransferase
3
HDAC = HistoneDeacetylase
MeCP2 = Methyl-CpG-binding protein
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3
The emerging evidence indicates that microRNAs control the epigenetic states that
underpin development…animals, particularly primates, have evolved plasticity in
these RNA regulatory systems, especially in the brain. Thus, it appears that what
was dismissed as 'junk' because it was not understood holds the key to
understanding human evolution, development, and cognition (JS MATTICK)
The third key word is fetal programming
Polycyclic Aromatic
Hydrocarbons (PAH)
(Ultra)-fine
particles
Heavy Metals
Benzene
Dioxin and
Dioxin-like
molecules
MATERNAL
STRESS
ONTOGENY
this is not a generic concept,
concerning the way in which
the "genetic program"
contained in DNA is
translated, during the nine
1 months of the ontogenetic
process, in a specific
complex phenotype.
on the contrary,this is a precise
technical term that refers to
the ability, and at the same
time to the necessity, of
embryo-fetal cells to define
their epigenetic setting in
adaptive (and predictive)
response to the information
coming from the mother and,
through her, from the outer
world.
2
3
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28/06/2016
The actual genetic program of a
particular individual is actually the
product of nine months of
epigenetic adaptive-predictive
“formatting” of billions of cells)..
1
Cellular
Differentiation:
Epigentic process
The
fourth
keyword is an
developmental
plasticity
Nature 447, 425-432 (24 May 2007)
Differentiation
Fetal Programming
PLASTICITY
2
epi-mutations
This is the stage of life which is far more sensitive to
information coming from the environment
(particularly to maternal-fetal stress, to nutritional
errors, to pollutants ..)
This image clearly shows the "power" of the epigenome and the
predominant role of environmental information in the phenotypic
shaping of cells, tissues , organisms .. the huge phenotypic (morphofunctional) difference between a lymphocyte and a neuron is not due to
DNA, which is virtually identical in the two cells , but to the manner in
which the same genome has been utilized by the two cells, on the
basis of the information (positional and environmental) received
during the first months of life (for neuron in the first 2 years) and
processed by the epigenetic networks
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28/06/2016
Most studied
disease/organ
endpoints and
associated
toxicity
endpoints.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4393755/figure/F3/
Phylogenesis
of 4 billion years of molecular
coevolution * (in particular, our DNA is the
product of this long journey) ..
Mismatch
We should never
forget that we are
at the same time
the product
Devo-Evo
Ontogeny
Recapitulates
(anticipates)
Phylogeny
Ontogenesis
And of 9 months of an
individual development
our epigenome being the
product of nine months of
cellular and tissue
programming
(adaptive to an environment
that is rapidly changing)..
A major risk: the EDCs and other xenobiotics (not being the product of
molecular coevolution) can interfere at this level, acting as pseudo-morphogens
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28/06/2016
The key-term in this context is
certainly primary prevention
..recently, the fetal programming mismatch theory has been
transformed into the key-moodel theory of DOHAD..
Obesity/Metabolic Syndrome
Cardiovascular
Diseases
Obesogens
Ipertension
DOHAD
Multiorgan Effects of
Endocrine Disruptors
Pesticides
In Vitro Fertilization
Materno Fetal Stress
OBESITY
DIABESITY
PANDEMICS
Placenta: Prediction
of Future Health
Developmental Time Windows of
Vulnerability
Reproductive
Diseases/Dysfunctions
Semen Abnormalities
Asthma and allergies
Lung Development
Neurobehavioral Deficits
and Diseases
CANCER
Psychiatric Diseases
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28/06/2016
Il termine Epidemia di Cancro non andrebbe usato. Ma non
bisogna sottacere il fatto che oggi una persona su due nei paesi
più avanzati è destinata a sviluppare una patologia neoplastica..
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28/06/2016
Thousands per Annum
the significant increase in the Less Developed Countries & in young people all over
the world demonstrates the limits of the SMT ( necessary link between aging &CA)
14000
14000
12000
12000
10000
10000
8000
8000
6000
6000
4000
4000
2000
2000
00
2002
2002
2005
2005
2010
2010
2015
2015
2020
2020
LessDeveloped
Developed More
MoreDeveloped
Developed
Less
ENVIRONMENT
> GENETICS
L'ambiente sembra influenzare i tassi e il rischio di cancro molto più che non
la "predisposizione genetica". E' possibile rendersene conto confrontando i tassi
di incidenza del cancro in diversi paesi e verificando come questi cambino
quando le persone si spostano da un paese all'altro
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28/06/2016
TEN LEADING CAUSES OF DEATH
(Children aged under 15 years) U.S. 2006
CAUSE OF DEATH
RANK ALL CAUSES
1
2
3
4
5
6
7
8
9
10
Accidents (unintentional injuries)
Cancer
Congenital anomalies
Assault (homicide)
Heart diseases
Intentional self-harm(suicide)
Influenza & pneumonia
Septicemia
Chronic lower respiratory diseases
Cerebrovascular disease
All other causes
NO. OF DEATHS
%OF TOTAL DEATHS
DEATHRATE*
10780
100.0
19.0
3868
1284
859
756
414
219
193
172
158
149
2708
35.9
11.9
8.0
7.0
3.8
2.0
1.8
1.6
1.5
1.4
25.1
6.8
2.3
1.5
1.3
0.7
0.4
0.3
0.3
0.3
0.3
-
* Rates are per 100,000 population and age adjusted to the 2000 US standard population.
Based on US Mortality Data, 2006, National 33
Center for Health Statistics, Centers for Disease Control and Prevention, 2009
Bisogna sempre considerare i dati epidemiologici nel medio-lungo termine, per non
essere ingannati dalle inevitabili fluttuazioni. E 'evidente che i tassi di incidenza
sono aumentati drasticamente negli ultimi 30 anni negli USA da 130 a 170-180
nuovi casi/anno per milione di abitanti (ed è importante notare che un incremento
analogo si è verificato in molti paesi europei)
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28/06/2016
A first draft of the report, published on the Lancet in 2004, demonstrated an annual increase of 1-1,5% for
all cancers (with more marked increases in lymphomas, soft tissue sarcomas, tumours of the nervous
system…) . But the most troubling was the increase - almost the double - for all cancers in the very first
year of life (apparently due to transplacental or even trans-generational exposure)
CA incidence in childhood and adolescence IN EUROPE ( 1970-1999)
http://www-dep.iarc.fr/accis.htm
latency
mother
Steliarova-Foucher E, Stiller C, Kaatsch P, Berrino F, Coebergh
JW, Lacour B, Parkin M. Geographical patterns and time trends
of cancer incidence and survival among children and
adolescents in Europe since the 1970s (the ACCISproject): an
epidemiological study. Lancet. 2004 Dec 11-17;364(9451):2097105
..in the last 20 years (1978 e il 1997) the overall incidence rate has increased
significantly with an average annual percentage change (AAPC) of 1,1%
(> 2% in the first year; 1,3 % during adolescence).
These data
should not be
underestimated
for at least
4 reasons:
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28/06/2016
Non può essere ridotto a
fenomeno para-fisologico
(accumulo di lesioni
ossidative a carico del Dna)
Rapporto AIRTUM 2008 - Tumori infantili. Incidenza, sopravvivenza, andamenti
temporali (Epidemiologia & Prevenzione 2008; 32(3) Suppl 2: 1-112)
• Periodo di osservazione 1998-2002
• Incidenza (nuovi casi l’anno). Nell’area coperta dai registri
tumori i tassi d’incidenza della malattia sono i seguenti:
bambini 0-14 anni: 175,4 casi per milione/anno
ragazzi 15-19 anni: 270,3 casi per milione/anno
• Il tasso di incidenza per tutti i tumori pediatrici in Italia è
più alto di quello rilevato negli anni novanta negli Stati
Uniti (158) e in Europa (140).
Attualmente in Germania è 141, in Francia è 138
• Andamenti temporali (anni 0-14) tra il 1988 e il 2002 (tre quinquenni) si
è osservato un aumento della frequenza del 2% annuo, passando da
146,9 casi periodo 1988-1992 a 176,0 casi nel periodo 1998-2002
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• L’incremento più consistente riguarda i bimbi sotto l’anno
di età (+ 3,2%), seguiti da quelli tra 10 e 14 anni (+2,4%),
mentre è simile negli altri due gruppi (+1,6% nella fascia di età
1-4 anni, +1,8% tra i 5 e i 9 anni).
• I tre tumori più frequenti nei bambini sono tutti in aumento:
• leucemie + 1,6% annuo; linfomi + 4,6% annuo; tumori del sistema
nervoso centrale + 2,0% annuo
• Un fenomeno simile è stato osservato in diversi Paesi,
• ma… in Italia il cambiamento percentuale annuo risulta
più alto che in Europa:
per l’insieme di tutti i tumori (+2% vs 1,1%)
per le leucemie (+1,6% vs 0,6%)
per i tumori del sistema nervoso centrale (+2% vs 1,7%)
per i linfomi (+4,6% vs 0,9%).
• (Negli Stati Uniti il tasso per tutti i tumori non è aumentato in modo
significativo (+0,6%), l’incremento delle leucemie è dello 0,4% e i tumori
del SNC sono stabili (-0,1%))
Cancer des enfants: de la génétique
à l'épigénétique
(vers un paradigme épigénétique dans la
carcinogenèse)
ERNESTO BURGIO
ECERI - European Cancer
and Environment Research
Institute (Bruxelles)
ISDE Scientific Committee
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28/06/2016
Depuis des décennies le modèle de la cancérogenèse est
basée sur des mutations stochastiques de l'ADN (SMT)
What is Cancer ?
Foreword 1
Is cancer a
Genetic
Disease ?
Dans ce modèle les cellules somatiques d'un tissu subissent une régression (commencent
à dé-différencier) pour des raisons intrinsèques accidentelles (mutations/épi-mutations)
What is Cancer ?
Nous proposons
que le cancer
est plutôt une
maladie de
cellules souches
tissulaires (par
détournement
des mécanismes
homéostatiques
qui régissent la
réparation des
tissus et l'autorenouvellement
des cellules
souches )
après stress
épi-génomique
prolongé
Or is cancer a stem cell disease (proceeding by misappropriating homeostatic mechanisms that govern
tissue repair and stem cell self-renewal) In this case Tissue Stem Cells (TSCs) - capable of proliferation and
self-renewal - proliferate after prolonged epi-genomic stress
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The Somatic Mutation
Theory of Carcinogenesis
Nel corso della vita, le mutazioni genetiche casuali si trasmettono
da una generazione cellulare all'altra e così si accumulano Nature
What’s Cancer ?
The revolution in cancer research can be summed up
in a single sentence: cancer is, in essence, a genetic disease
Alterations in three types of genes are responsible for tumorigenesis:
oncogenes, tumor-suppressor genes and stability genes
Unlike diseases such as cystic fibrosis or muscular dystrophy,
wherein mutations in one gene can cause disease, no single gene defect
'causes' cancer. Mammalian cells have multiple safeguards to protect them
against the potentially lethal effects of cancer gene mutations,
and only when several genes are defective does an invasive cancer develop
Vogelstein B, Kinzler KW. Cancer genes and the pathways they control Nat Med. 2004 Aug;10(8):789-99.
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Darwinian Evolution Through Random Mutation
STEP 1 La delezione o la mutazione del gene APC in 5q21 è sufficiente
perché il colon venga tappezzato di polipi adenomatosi; Il DNA
diventa ipometilato ⇒nuove mutazioni
STEP 2 Le mutazioni di K-RAS (K-RAS1 in 6p12-11 e K-RAS2
in 12p12) sono spesso coinvolte nella progressione degli
adenomi da precoci a intermedi.
STEP 3 Il presunto gene soppressore dei tumori coinvolto
è DCC (“Deleted in Colon Cancer” → perdita di
eterozigosi in 18q21.3).
STEP 4 mutazioni gene oncosoppressore
p53 (localizzato in 17p12-13).
STEP 5 MutazionI del gene NM23-H1 (17q22)
rendono il CA altamente invasivo/metastatico..
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What’s Cancer ?
We suggest that the vast catalogues of cancer cell genotypes
is a manifestation of six essential alterations in cell
physiology that collectively dictate malignant growth
Tumor development proceeds via a process
formally analogous to Darwinian evolution,
in which a succession of stochastic mutations,
each conferring one or another type of growth
advantage, leads to the progressive conversion
of normal human cells into CA-cells…
1
2
3
CA-cells have defects in regulatory circuits
that govern normal cell proliferation and
homeostasis… the vast catalog of CA-cell
genotypes is a manifestation of six essential
alterations in cell physiology that collectively
dictate malignant growth:
4
5
6
Proliferazione indipendente
da segnali di crescita
Resistenza all’apoptosi
Attivazione
dell’angiogenesi
Insensibilità ai segnali inibitori
Tendenza a
metastatizzare
Riattivazione della telomerasi
(e immortalizzazione)
48
D. Hanahan, & Weinberg, R. A. (2000) The Hallmarks of Cancer, Cell, Vol. 100, pp. 57-70
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2
6
5
6
2
1
4
P
P
3a
P
3
P
3b
RTK Receptor
Tyrosine Kinases
- l'autosuffisance en signaux de croissance,
- l'insensibilité au signaux inhibiteurs de la croissance,
- la capacité à éviter l'apoptose,
- la capacité de se répliquer indéfiniment,
- l'induction de l'angiogenèse et
- la capacité à former des métastases
some benign tumours can weigh many
kilograms at the time of diagnosis
sustained angiogenesis is a feature of
both benign and malignant tumours
RB protein is deficient both in retinoblastoma, a malignant tumour
of the eye, and in retinoma, a benign tumour of this organ.
evasion of apoptosis has been implicated in the
pathogenesis of malignant and benign tumours
insensitivity to antigrowth signals and evasion of cell death also
seem to be characteristic of both benign and malignant tumours
five of the proposed hallmarks of cancer
are also characteristic of benign tumours
La seule caractéristique distinctive du cancer est la capacité à métastaser
(qui n’est pas, comme nous le verrons, le résultat des mutations, mais
la réactivation d'un programme génétique embryonnaire !!)
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28/06/2016
J Clin Invest. 2009;119(6):1438–1449.
La seule
caractéristique
fondamentale
(hallmark) du
cancer est sa
tendance à la
métastase qui n'est
pas due à des
mutations, mais
à la réactivation
d'un programme
embryonnaire,
la transition
épithélialemésenchymateuse
(EMT) qui permet
aux cellules foetales
de l'embryon de
migrer vers leur
destination finale
dans les divers
tissus
Les inducteurs de EMT sont bloqués chez l'adulte.. Mais ils sont activées
dans la fibrose d'organes et dans les fases invasives des cancers
The GWAS efforts are
certainly creating
bigger haystacks …
In a recent editorial
on Nature
Heidi Ledford stated
that the millions of
genetic sequences
and SNPs
accumulated in an
attempt to decipher
the genetics of
cancer have built
giant haystacks
in which researchers
have gone lost …
The full genome sequence of a lung cancer cell line,
for example, yielded 22,910 point mutations,
only 134 of which were in protein-coding regions
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28/06/2016
Looking for that Needle in a Haystack
Roughly 75 cancer genomes have been
sequenced to some extent and
published; researchers expect to have
several hundred completed sequences
by the end of the year.
The efforts are certainly creating bigger
haystacks.
Circa 75 genomi
neoplastici sono stati
sequenziati ...
i ricercatori si aspettano
di avere diverse
centinaia di sequenze
complete entro la fine
dell'anno.
Tali tentativi hanno
portato alla creazione di
grandi “pagliai”.
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Loeb L A Mutator Phenotype May Be Required for Multistage Carcinogenesis Cancer Res (1991) 51:3075–3079,
Loeb LA Human cancers express mutator phenotypes: origin, consequences and targeting Nature Reviews Cancer 11,
450-457 (June 2011) | doi:10.1038/nrc3063
D’autres théories (par exemple celle du mutator phénotype) démontrent plutôt
qu'un tissu dans le processus de transformation néoplasique a une tendance à
accumuler des mutations (qui ne sont pas la cause de cancer, mais la
conséquence de l'instabilité génétique acquise)
Cell 144, 27–40, January 7, 2011
8505C, a thyroid cancer cell line, shows 77
rearrangements involving chromosome 9p.
TK10, a hyperdiploid line, carries
six copies of chromosome 5.
Même les catastrophes génomiques récemment signalés dans des
différentes formes de cancer sont difficiles à concilier avec la
théorie de l'accumulation lente de mutations stochastiques
(SMT) .. et dans ce cas aussi, le parallélisme avec ce qui se passe
dans le domaine de l'évolution semble éclairante
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Giampaolo Collecchia, Arezzo 2014
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Cancer Not Just Bad Luck
Here we provide evidence
that intrinsic risk factors
contribute only modestly
(less than ~10-30% of lifetime
risk) to cancer development…
we conclude that cancer risk
is heavily influenced by
extrinsic factors.
Cancer Epidemiology
Historical Perspective
1700s: tobacco and cancer
Reports of cancer risks associated
with tobacco in the 18th century
included snuff taking and nasal
cancer, reported by Hill in 1761,
and pipe smoking and lip cancer
by von Soemmering in 1795.
Faina Linkov, PhD; Research Assistant Professor of Medicine
and Epidemiology; University of Pittsburgh Cancer Institute
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Cancer Epidemiology
Historical Perspective
1775
British surgeon,
Percival Pott reported
probably the first
description of
occupational
carcinogenesis
in the form of
scrotum cancer
among
chimney sweeps.
The actual association between this
occupational hazard and scrotum cancer
was increased incidence of squamous cell
carcinoma due to exposure to soot.
Faina Linkov, PhD; Research Assistant Professor of Medicine
and Epidemiology; University of Pittsburgh Cancer Institute
Tight corsets and cancer
1842
Rigoni-Stern, Italian physician,
observed that married women in
the city were getting cervical
cancer, but nuns in nearby
convents weren’t.
He also observed that nuns had
higher rates of breast cancer,
and suggested that the nuns’
corsets were too tight.
Faina Linkov, PhD; Research Assistant Professor of Medicine
and Epidemiology; University of Pittsburgh Cancer Institute
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28/06/2016
Nurture
Exposure to asbestos is linked to lung cancer, and exposure
to benzidine (a chemical found in some dyes) is linked to bladder cancer
Exposure to carcinogens from tobacco use is linked to several types of cancer:
cancers of the lung, bladder, mouth, lip, throat, voice box, and esophagus
Nurture
FOOD
CHAINS
?!?
About 20 ingredients in pesticides have been found to cause cancer in animals.
Studies of people with high exposure to pesticides - farmers, crop duster pilots,
pesticide manufacturers - have shown higher rates of blood and lymphatic system
cancers, melanoma and cancers of the lip, stomach, brain, lung, and prostate.
33
28/06/2016
Nurture
FOOD
CHAINS
!!
!
!
!
!
Dioxins are byproducts of paper bleaching, smelting, and waste incineration
They are widespread in the environment because they break down very slowly.
They also accumulate in fat cells. Most of our exposure to dioxins comes
from eating dairy products, fish, and meat.
Nurture
We commonly use more than
100,000 chemicals and this
doesn't take into account
mixtures or combinations
of chemicals. Plus, some
chemicals are altered by the
atmosphere, water, incineration.
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28/06/2016
Nurture
Effetti cancerogeni delle sostanze emesse da un inceneritore secondo la IARC
(Annali Istituto Superiore Sanità 2004)
agente
Grado di evidenza
IARC
Effetto cancerogeno
Arsenico
1
Pelle, polmoni, fegato, vescica, rene, colon
Berillio
1
Polmone
Cadmio
1
Polmone, prostata
Cromo
1
Polmone
Nickel
1
Polmone
Mercurio
2b
Polmone, pancreas, colon, prostata, encefalo,
rene
Piombo
2a
Polmone, vescica, rene, gastroenterica
Benzene
1
Leucemia
Idrocarburi
policiclici
2b
Fegato, polmone, leucemia
Cloroformio
2b
Vescica, rene, encefalo, linfoma
Clorofenoli
2b
Sarcomi tessuti molli, linfomi Hodgkin e non
Hodgkin
Tricloroetilene
2a
Fegato, linfomi non Hodgkin
TCDD
1
Linfomi, sarcomi non Hodgkin
35
28/06/2016
Carcinogenic mechanisms of arsenic compounds
http://www.mdpi.com/2072-6694/2/2/376/htm
The Role of Oxidative Stress in
Carcinogenesis Induced by
Metals Cancers 2010, 2(2),
376-396
Inorganic arsenic compounds and methylated metabolites display similar genotoxic properties.
Generation of oxidative stress is regarded as central mechanism in As-mediated carcinogenesis.
A mitochondria-dependent mechanism and a H2O2/hydroxy radical pathway are discussed.
In addition, arsenic affects DNA methylation and DNA repair enzymes
Carcinogenic mechanisms of chromium compounds.
The Role of Oxidative Stress in
Carcinogenesis Induced by
Metals Cancers 2010, 2(2),
376-396
Chromium (VI) compounds are internalized in cells via anionic channels. Cr(VI) is then
reduced and accumulates as trivalent ion.
Formation of Cr(III)-DNA adducts is regarded as predominant carcinogenic mechanism.
In parallel, chromium ions can engage in Fenton-like reactions, generating hydroxy radicals
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28/06/2016
Carcinogenic mechanisms of nickel.
Nickel ions can induce oxidative stress, which provides a primary genotoxic stimulus required for
carcinogenesis (red lines).
In addition, Ni(II) triggers multiple mechanisms that amplify the moderate effects of oxidative stress (+).
An interplay of enhanced proliferation and up-regulation of p53 could constitute a strong selective
pressure, favouring mutations, which may inactivate tumor suppressor genes
Cadmium and oxidative stress.
Cadmium does not belong to redox-active metals. Several mechanisms for generation of ROS have been
proposed though. Chronic Cd(II) exposure can also induce expression of metallothionin (MT) and triggers
adaption mechanisms towards oxidative stress, thus limiting the role of ROS in carcinogenesis.
Alternate carcinogenic mechanisms of cadmium, such as inhibition of DNA repair, are not shown here
37
28/06/2016
Direttiva 2004/107/CE
• Direttiva 2004/107/CE del parlamento europeo
e del Consiglio del 15 dicembre 2004 concernente
l’arsenico il cadmio, il mercurio, il nickel e gli idrocarburi
policiclici aromatici nell’aria ambiente
!
“ Dai dati scientifici disponibili risulta che
l’arsenico, il cadmio, il nickel e alcuni IPA
(Idrocarburi Policiclici Aromatici) sono agenti
genotossici e cancerogeni per l’uomo e che
non esiste una soglia identificabile al di sotto
della quale queste sostanze non comportino
un rischio per la salute umana
La Modulazione (Epi)genetica in tossicologia
1
Studi recenti hanno dimostrato che alcuni Interferenti Endocrini (IE) sono in grado di
modulare l'espressione genica e che tale effetto è trasferibile alle generazioni successive
xenobiotics
Jirtle RL and Skinner MK (2007) "Environmental
epigenomics and disease susceptibility".
Nat Rev Genet, 8(4):253-262.
38
28/06/2016
1
1
2
3
Nuclear Receptor
Nuclear Receptor
DNA Response Element
Once thought to play a largely passive, structural role, it is now
clear that chromatin plays a pivotal role in the regulation of
gene expression, chromosome replication, cell cycle
progression, and the maintenance of genome integrity by
marshalling access to the DNA template.
One of the
principle ways
in which a
eukaryotic cell
responds to
changes in its
environment
is by altering
gene expression
to change the
complement
of expressed
proteins and,
thereby, maintain
homeostasis.
Consequently,
practically all
toxic events
will result in
changes
in gene
expression.
The Nuclear Receptors, of
which there are more than
48 in mammals, are a
family of ligand-activated
transcription factors.
A growing number of
xenobiotics have been
shown to function by
directly altering the
activity of Nuclear
Receptors.
For example, peroxisome
proliferators,
dioxins, and estrogenic
chemicals act via the
Peroxisome Proliferator
Activated Receptor α
(PPAR α),
Aryl hydrocarbon receptor
(AhR), and Estrogen
Receptors (ER),
respectively
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28/06/2016
Many toxicants cause
rapid alterations in
gene expression by
activating protein
kinase signaling
cascades.
Histone Acetyltransferases;
Histone Methyltransferases
Histone Deacetylases.
Histone
Lysine
Acetylation
P
H3-K9
Nuclear Receptor
DNA Response Element
H3-S10
ATP-dependent Nucleosome
Remodeling Complex
These modifications are believed to be
essential for the full transcriptional
response to stress-inducing chemicals
The resulting rapid,
defensive alterations in
gene activity require
the transmission of a
signal directly to the
histones present in the
chromatin of stress
response genes:
within minutes
of exposure
the phosphorylation of
serine 10 of histone H3
and the acetylation
of lysines 9 and/or 14
take place
This makes DNA sequences at
the transcriptional start site accessible to RNA
polymerase II and the general transcription
machinery and facilitates the initiation of gene
transcription
(or DNA repair).
Nuclear Receptor
General Transcription Factors
and
DNA Repair
In an analogous
manner to the chromatin
decompaction that
accompanies recruitment
of RNA polymerase II
during gene activation,
DNA excision repair is
associated with increased
histone acetylation and
localized chromatin
remodeling
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28/06/2016
Histone modifications as early markers of DNA damage
P
H2A.X – S 139
P
P
Phosphorylated H2A.X is thought
to function by recruiting additional
proteins that may enhance
the accuracy or efficiency
of DNA repair.
P
Phosphorylation of
serine 139 within the
specialized variant Histone
H2A.X.
P
The sensing of
double-strand DNA breaks (e.g.,
produced by
ionizing radiation or
DNA-binding drugs)
is accompanied by the activation of
protein kinases that rapidly
phosphorylate the specialized
Histone Variant H2A.X
and also transduce signals
to additional signaling and DNA
repair proteins.
P
H2A.X functions as a
tumor suppressor gene
protecting cells from
the deleterious
effects of DNA damage
P
Phosphorylation of Serine
139 of histone H2A.X
also occurs during apoptosis
The toxic metal nickel can inhibit HAT enzymes and the inhibition of histone acetylation by nickel
compounds in vivo has been associated with the silencing of gene expression (concomitant alterations in
histone acetylation and gene expression appear to be important for nickel-induced cellular transformation)
Another carcinogenic metal, chromium, has recently been shown to perturb HAT and HDAC enzymes
occupancy on PAH–inducible genes, resulting in the inhibition of their transcription…
Chromium is known to form DNA protein cross-links, and these might be responsible for blocking the
normal function of chromatin-modifying enzymes during aryl hydrocarbon receptor AhR–mediated gene
activation
Una condizione di instabilità genomica (ipometilazione diffusa, iper-metilazione
delle sequenze promoter di geni onco-soppressori, specifiche combinazioni
del “codice istonico”) è di frequente riscontro nelle lesioni (pre)-neoplastiche e
neoplastiche (e potrebbe essere, interpretata, come reattiva/adattativa)
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28/06/2016
1
Controlling active and inactive states of
embryonic and somatic cells
2
Gene- and tissue-specific epigenetic patterns
A
Hormones
B
Mismatch Repair Enzymes
Trascription Factors
Correct organization
of chromatin
3
5
X chromosome inactivation
Genomic
imprinting
6
4
“Silencing “ mobile sequences
E’ possibile a questo punto ipotizzare che anche il cancro, al pari di
tante altre malattie cronico-degenerative e/o infiammatorie,
tutte in grande aumento nel mondo intero, sia una malattia
essenzialmente (primariamente) epigenetica a insorgenza precoce
(periodo embrio-fetale) da alterata programmazione di organi e
tessuti dovuta a esposizione precoce agli agenti inquinanti ?
Cheryl Lyn Walker UT MD Anderson Cancer Center
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28/06/2016
Notes on the epigenetic (transplacental and
transgenerational) origins of childhood cancer
ERNESTO BURGIO
ECERI - European Cancer and
Environment Research Institute
ISDE Scientific Committee
1
2
3
43
28/06/2016
CHEMICAL FALL OUT
1 ENDOCRINE DISRUPTORS
dioxin-like moleculles
The gift our mothers
never wanted to give us
2
HEAVY METALS
3
ULTRAFINE PARTICLES
attualmente molti studi in varie parti del mondo stanno valutando
il carico corporeo chimico .. soprattutto nelle donne, bambini,
embrioni / feti, fornendo risultati drammatici…
http://www.ewg.org/reports/generations/
44
28/06/2016
Metalli pesanti, diossine e altre sostanze cancerogene immesse in ecosfera, e veicolate
nei tessuti degli organismi viventi, possono bio-accumularsi in ossa e grassi e bio
magnificarsi nelle catene alimentari . Dai tessuti dove si accumulano (a volte per
decenni), il loro rilascio è generalmente lento e continuo
Biomagnificazione
What is the Global Chemical Burden..
Industrial chemicals in mothers and daughters:
the pollution we share and inherit
E’ così che nel sangue e nei tessuti di tutti gli uomini e le donne che vivono in ambienti urbani
e/o industriali e persino nel sangue cordonale e placentare e nei tessuti fetali sono presenti
questi stessi inquinanti in quantità di anno in anno, di decennio in decennio maggiori
45
28/06/2016
Monitoring Body-Burdens
700 different synthetic chemicals or
heavy metals found in human blood,
POPs
Giuseppe Giordano
“Diossina di Seveso”: sino a 10 anni negli adipociti !
Tanto più che metalli, diossine e altri inquinati lipofili accumulati nei tessuti materni possono
passare, anche a distanza di anni dal loro assorbimento, nel sangue e raggiungere il feto
Is it true that metals, dioxins and other lipophilic pollutants, accumulated in maternal tissue, may pass,
even many years after their absorption, into the blood and reach the fetus?
46
28/06/2016
XXI e siècle: transformation spectaculaire de
l'environnement et du microenvironnement utérine
DOHAD
47
28/06/2016
Bisogna in effetti distinguere varie possibilità: 1) l'esposizione fetale ad agenti fisici (raggi X),
chimici o biologici (virus) (trasmissione trans-placentare) che possono direttamente
danneggiare l'embrione/feto 2) la trasmissione potenzialmente trans-generazionale di danni
genetici o epigenetici insorti nei gameti 3) l’esposizione post-natale precoce
Trasmissione
transgenerazionale
2
3
1
(epi)mutations
in gametes
Transgenerational
Carcinogenesis
TEL-AML1 in cord blood:
1% or 0.01%?
Competing models of
TEL-AML1+
leukemogenesis.
48
28/06/2016
(5) Pro-leukemic translocations in foetuses
.. the first unambiguous evidence for a
prenatal origin of leukaemia was derived
from studies in identical twins with
leukaemia. A case of identical
(monozygotic) infant twins with
leukaemia was recorded in 1882, and,
since that time, more than 70 pairs have
been published albeit in variable detail ...
1
2
Chromosomal translocations and preleukaemic clones arise at a
substantially higher frequency (~100 X) before birth than the cumulative
incidence or risk of disease, reflecting the requirement for complementary
and secondary genetic events that occur postnatally. A consequence of the
latter is a very variable and occasionally protracted postnatal latency of
disease (1—15 years).
3
The concordance rate of leukaemia varies
according to subtype and age.
For infants with ALL, the rate is
exceedingly high (> 50%), for
“COMMON” child-ALL, is ~10%.
Adult leukaemia (ALL/ AML),
in contrast, has a very low rate
of concordance (< 1%).
~1% of newborns had TEL-AML1 positive B lineage clones…
which represents 100 times the incidence of TEL-AML1 positive ALL (~1 in 12,000).
!
MLL rearranged leukemias are associated
with poor prognosis and very brief latency
for MLL-AF4+ infant B ALL. This raises the
question of how this disease can evolve so
quickly,
Even if leukaemia fusion gene formation is
spontaneous, the risk of this occurring may be
modified by other factors, including folate
!!
availability. There is dietary and genetic
evidence that folate has an impact
on the risk of infant and childhood leukaemia ..
49
28/06/2016
Translocations typical of myeloid leukaemia, probably due to maternal exposure to some toxic compound, were shown to
be present at birth in children who developed the disease years later (while not sufficient per se to cause the disease, they might
increase the risk for leukaemia by inducing genomic instability) Tomatis L. Identification of carcinogenic agents and primary
prevention of cancer. Ann N Y Acad Sci. 2006 Sep;1076:1-14
Translocation involving
band 11q23 in AML may
occur as a result of a
deletion or trans-locations
with a number of other
chromosomes and is usually
associatedwith M4 or M5
and a poor prognosis
IN ALL AND AML, THE ALL1
(ALSO NAMED MLL) GENE
CAN FUSE WITH 1 OF MORE
THAN 50 GENES. ALL1 IS
PART OF A MULTIPROTEIN
COMPLEX. MOST OF THE
PROTEINS IN THE COMPLEX
ARE COMPONENTS OF
TRANSCRIPTION COMPLEXES;
OTHERS ARE INVOLVED IN
HISTONE METHYLATION AND
RNA PROCESSING. THE
ENTIRE COMPLEX REMODELS,
ACETYLATES, DEACETYLATES,
AND METHYLATES
NUCLEOSOMES AND
HISTONES. THE FUSION OF
ALL1 WITH 1 OF these 50
PROTEINS RESULTS IN THE
FORMATION OF THE
CHIMERIC PROTEINS THAT
UNDERLIE ALL AND AML.
ALL1 (MLL) FUSION PROTEINS
DEREGULATE HOMEOBOX
GENES (WHICH ENCODE
TRANSCRIPTIONS
FACTORS)..and microRNAs
GENES SUCH AS MIR191.
The first and most striking property of MLL fusion proteins is their incredible diversity. MLL has
been found in 73 different translocations and 54 partner genes have been cloned
(http://atlasgeneticsoncology.org/Genes/MLL.html).
Nakamura T, Mori T, Tada S, et al. ALL-1 is a histone methyltransferase that
assembles a supercomplex of proteins involved in transcriptional regulation
Cell 2002;10:1119-1128.
AF9 Location 9p22
MLL Location 11q23
histone
methyltransferase
Several lines of evidence point to a mishap in non-homologous end joining of double strand breaks as the most likely reason for 11q23 translocations.
50
28/06/2016
Our study has supported the
hypothesis that in utero exposure to
chemicals causes MLL* infant
leukemia and has generated specific
hypotheses that require further testing.
Exposure to dipyrone is widespread,
particularly in Central and South
America where it is available as an
inexpensive, nonprescription drug.
Mosquitocidals are similarly in general
use in these same settings. Propoxur
(Baygon°) is also widely used against
cockroaches, fleas, and similar pests.
Therefore, it is important that the
associations observed in this study are
reevaluated in an extended casecontrol study
Exposure to NHL-associated carcinogens,
such as dioxin or pesticides, may cause
expansion of t(14;18)-positive clones.
51
28/06/2016
Figure 2. t(14;18)+ cells in HI are actively transcribing BCL2 from the translocated allele
We can find exactly
the same (reactive)
translocation (++
expression of the antiapoptotic gene BCL-2)
in many subjects
chronically exposed
to pesticides ..
Agopian et al. Journal of Experimental Medicine 2009:206:1473-1483
52
28/06/2016
IN THE CANCEROUS B CELLS, THE PORTION OF CHROMOSOME 18 CONTAINING THE BCL-2 LOCUS HAS UNDERGONE A
RECIPROCAL TRANSLOCATION WITH THE PORTION OF CHROMOSOME 14 CONTAINING THE ANTIBODY HEAVY CHAIN
LOCUS. THIS T(14;18) TRANSLOCATION PLACES THE BCL-2 GENE CLOSE TO THE HEAVY CHAIN GENE ENHANCER.
H Chain-enhancer is very active in B cells...
53
28/06/2016
…. les mêmes
mutations génétiques
et chromosomiques,
d’ailleurs toujours
assez complexes
(aneuploïdie,
translocations,
mutations des
oncogènes et des
gènes suppresseurs) se
trouvent
non seulement dans les
cellules du clone
néoplasique primaire
(dans ce cas, les
lymphocytes), mais
dans plusieurs tissus
intéressés …
54
28/06/2016
Ces données suggèrent
que, même dans les
lymphomes, les cellules
endothéliales (telles que
les cellules du stroma
dans les tumeurs solides)
sont liées au cancer …
+
+
+
THE FIRST EVIDENCE THAT
CANCER ARISES FROM
SOMATIC GENETIC
ALTERATIONS CAME FROM
STUDIES OF BURKITT'S
LYMPHOMA, IN WHICH ONE
OF THREE DIFFERENT
TRANSLOCATIONS
JUXTAPOSES AN
ONCOGENE, MYC, ON
CHROMOSOME 8q24
TO ONE OF THE LOCI FOR
IMMUNOGLOBULIN GENES.
CHROMOSOMES 14q, 22q,
AND 2q
— THE TRANSLOCATION
PARTNERS —
EACH CARRIES ENHANCER
ELEMENTS IN THE
IMMUNOGLOBULIN LOCI,
THEREBY ACTIVATING THE
JUXTAPOSED C-MYC
ONCOGENE
Are the antibody gene loci
quite“dangerous places” for
proto-oncogenes to take up
residence ?
Croce CM. Oncogenes and Cancer. N Engl J Med 2008;358:502-11.
55
28/06/2016
22q11.2
The c-abl oncogene from the distal
tip of chromosome 9q34 has been
translocated into the bcr
(breakpoint cluster region) locus on
chromosome 22q11.2.
This t(9;22) translocation
generates a chimeric BCR-ABL
gene that expresses a
chimeric bcr-abl mRNA and
fusion protein.
The Bcr-Abl fusion protein
stimulates unregulated growth
and has been shown to be
involved in the pathogenesis of
chronic myeloid leukemia
(CML) and a subset of acute
lymphoblastic leukemia (ALL)
… in Bielorussia l’incidenza aumentò di 30 volte nel ’95 e nelle zone più vicine a
Chernobyl di 100 volte… inoltre, per dosi molto alte il rischio di CA diminuiva,
mentre aumentava il rischio di ipotiroidismo, per distruzione di tessuto tiroideo…
nella quasi totalità dei casi era implicato uno specifico oncogène (c-RET),
coinvolto in traslocazioni interpretabili come reattivo-adattative …
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28/06/2016
Towards an epigenetic model in carcinogenesis
• .. there is now ample evidence that some specific epigenetic
alterations, (primarily the hypomethylation of DNA, with
activation of oncogenes and increased mobility of mobile
sequences) ** are the result of protracted genomic stress
(eg chronic inflammation and persistent oxidative stress)
• and generally anticipate, to some extent preparing it, genetic
modification and an overall genomic instability
• Should these data change our way of representing cancer ?
** + an hypermethylation of tumor
suppressor genes promoters
57
28/06/2016
The ‘‘methylation
paradox’’ of cancer cells.
In fact cancer cells
present a gain of
methylated streches
at regions
that are usually
unmethylated
(hypermethylation)
concomitantly with
loss of methylation at
genomic loci that are
normally methylated
(global
hypomethylation),
R Villa, F De Santis, A Gutierrez, S Minucci, PG Pelicci, L Di Croce
Epigenetic gene silencing in acute promyelocytic leukemia Biochem
Pharmacol (2004) 68: 1247-54
Retrosequences
activation
Ce qui se passe, au début, ce n’est que des modifications épigénétiques produites par un stress prolongé du tissu et du génôme :
une hypométhylation de séquence d’ADN et une hypeméthylation spécifique des promoteurs des gènes suppresseurs...
1
2
3
2
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28/06/2016
In the present study, we demonstrate
how one single type of DNA alteration,
aberrant methylation of gene
promoters, can point to pathways
disrupted in every type of cancer and
can provide markers
for sensitive detection of virtually
all tumor types.
We have now analyzed a series of promoter
hypermethylation changes in 12 genes..
each rigorously characterized for association
with abnormal gene silencing in cancer…
Our results provide an unusual view
of the pervasiveness of DNA alterations, in
this case an epigenetic change, in human
cancer and a powerful set of markers to
outline the disruption of critical pathways in
tumorigenesis
NOTE ! Bien que de nombreuses tumeurs
partagent une même modification pour un
gène donné, des profils uniques existent
pour chaque type de tumeurs.
Conclusions
Our data demonstrate, using a candidate gene
approach, that promoter hypermethylation
of 12 genes involving important cellular pathways
in tumorigenesis is a feature of each of 15 major
human tumor types studied.
Moreover, although many tumors share this change
for a given gene, unique profiles do exist for the
tumor types.
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28/06/2016
ONE OR MORE OF THE GENES STUDIED IS HYPERMETHYLATED IN EVERY TUMOR TYPE. HOWEVER, THE PROFILE
OF PROMOTER HYPERMETHYLATION FOR THE GENES DIFFERS FOR EACH CANCER TYPE, PROVIDING A TUMORTYPE AND GENE-SPECIFIC PROFILE. SOME GENES, SUCH AS THE CELL CYCLE INHIBITOR P16INK4A, ARE
HYPERMETHYLATED ACROSS MANY TUMOR TYPES INCLUDING COLORECTAL, LUNG, AND BREAST CARCINOMAS
Other changes, such as for the
DNA repair gene MGMT and
DAPK, also have a wide
distribution
REMARK
• Those who adhere to the paradigm of
stochastic mutations
• and more generally to a linear and genecentric model of DNA
•
have obviously some difficulty to
accept all this…
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28/06/2016
The dynamic (epi)-genome
9
• En fait, seulement dans un modèle de génome conçu comme
un réseau moléculaire unitaire et complexe (en même temps,
dynamique et responsif) il est possible de suggérer que
• toutes les modifications : épigénétiques (hypométhylation
globale de l'ADN, hyper-méthylation des séquences
promotrices de gènes suppresseurs de tumeurs, modifications
des réseaux des ncRNAs), génétiques (instabilité génomique et
mobilisation des séquences transposables ..), et même
chromosomiques (translocations ) qui déterminent la
progression d'un cancer
• doivent être considérées comme des étapes dans un
processus (déformé) d'évolution –adaptation –défense
tissulaire
Esteller M. Cancer epigenomics: DNA methylomes and histone-modification maps Nat Rev Genet (2007);8(4):286-98;
Karpinets TV, Foy BD. Tumorigenesis: the adaptation of mammalian cells to sustained stress environment by epigenetic
alterations and succeeding matched mutations. Carcinogenesis. (2005); 26(8):1323-34; Hauptmann S., Schmitt W.D.
Transposable elements - Is there a link between evolution and cancer? Medical Hypotheses (2006), 66 (3):580-591;
Is the carcinogenic process the
ontogenic development gone awry ?
Is the main cause of cancer a block in
cell differentiation programs (just the
“hallmark”, inexplicably neglected by
major theorists of SMT) ?
The Embryonic Rest Theory and the field theories of cancer
Some Virckow’s followers (1870 ca) formulated the theory that adult tissues
contain dormant embryonic remnants that could be activated to become cancer
Perhaps the most intriguing aspect of the theory concerned the hypothesized
trigger of the process: ..a change in the environment, a “disequilibrium” in the
surrounding tissue, that would induce these embryonic remnants to resume cell
proliferation and to produce masses of cells resembling fetal tissues (field theory)
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28/06/2016
The Embryonic Rest Theory and the
field theories of cancer
From Cellular Pathology:
Development of cancer from
connective tissue in the
carcinoma of the breast
Virchow, Rudolf. Cellular Pathology as Based Upon Physiological and
Pathological Histology. London, 1860
Virchow and other well known
pathologists, on observing cancer
tissue under the microscope, noted the
similarity between embryonic tissue
and cancer, and suggested that tumors
arise from embryo-like cells [105].
On this basis, some Virckow’s followers
[106-107] formulated the theory that
adult tissues contain dormant
embryonic remnants that could be
activated to become cancer.
Perhaps the most intriguing aspect of the
theory concerned the hypothesized
trigger of the process: it would be a
change in the environment, a
“disequilibrium” in the surrounding
tissue, that would induce these
embryonic remnants to resume cell
proliferation and to produce masses of
cells that resembled fetal tissues (field
theory).
The great lesson of teratocarcinoma
and the stem cell theory of cancer
• the transplantation of pluripotent or embryonic stem cells
into adult mammals, frequently leads to the growth of
teratocarcinomas
• the microenvironment was central to this paradigm-breaking
findings: the origin of the teratoma was a “dissonance”..
• intriguingly, putting the teratocarcinoma cells into an early
mammal embryo at the blastocyst stage.. they can generate
normal tissues in viable mosaic individuals ..
• normal offspring could result from a… cancer cell
• normal germinal stem cells who became cancerous, showed
the potential to revert to normal cells if placed in embryo
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PML-RAR α as well as other leukemia-associated fusion proteins induce changes in the chromatin structure.
Specifically, aberrant recruitment of different chromatin modifying enzymes to specific promoters induces
DNA hypermethylation and heterochromatin formation leading to transcriptional silencing of that genes
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vertical arrows pointing to the position in the PML exonic
sequences of the breakpoints. The horizontal arrows point
to the location of the oligonucleotide primer pairs used
for nested PCR amplification
Schematic representation of the step-wise silencing of PML-RARα target genes
*
1
5
2
4
3
1 The oncoprotein PML-RARα recognizes a well-defined DNA sequence *
2
3
5
.. recruits repressor enzymes, such as HDACs and DNMTs leading to hypo-acetylation of histone tails, DNA methylation, and
transcriptional silencing…
Methylated CpGs are potential docking sites for MBD proteins, which can in turn recruit further repressor enzymes.
4
The progression wave.. might ‘‘close’’ the chromatin structure and could even influence neighboring genes.
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In conclusione
• Il cancro può esser visto come un “incidente
genetico” da mutazioni stocastiche del DNA
a carico di geni fondamentali (oncogeni,
oncosoppressori) in cellule somatiche di vari
tessuti (SMT)
• o come patologia di tessuto/organo dovuta a
modifiche epigenetiche e/o genetiche indotte
nelle cellule staminali da una esposizione
protratta ad agenti inquinanti destabilizzanti
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3
1
4
2
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Il “paradosso epigenetico “
delle cellule neoplastiche
In ogni caso è
importante sottolineare
che alcune modifiche
epigenetiche
– la ipometilazione
della sequenza del
DNA con attivazione
delle sequenze mobili
e la ipermetilazione
delle sequenze
promoter dei geni
oncosoppressori –
sono in genere
precoci e sembrano
poter dare avvio
avvio al processo
neoplastico
R Villa, F De Santis, A Gutierrez, S Minucci, PG Pelicci, L Di Croce
Epigenetic gene silencing in acute promyelocytic leukemia Biochem
Pharmacol (2004) 68: 1247-54
Retrosequences
activation
.. mentre è verosimile che la gran parte delle migliaia di mutazioni somatiche che
si accumulano nel DNA delle cellule neoplastiche siano la conseguenza
dell'instabilità genomica progressiva più che non la "causa" del cancro
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A new scientific truth does not
triumph by convincing its
opponents and making them
see the light,
but rather because its opponents
eventually die, and a new
generation grows up that is
familiar with it.
Max Planck (1858 - 1947)
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