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Epigenetics and Breast cancer- Evening Session -
Transcript of Epigenetics and Breast cancer- Evening Session -
and Breast Cancer
From the Greek word “epigenesis” - the influence of genetic processes on development
Many cancers are a result of inactivation of a tumour suppressor genes
Suppressor genes can be inactivated by DNA methylation.
Two basic models for how tumour suppressor genes can be methylated:
the stochastic model and
the instructive model
Epigenetics and Cancer
Can cause epigenetic changes
Results might be seen decades after exposure
Epigenetics changes could be inherited by children
Examples include smoking, dietary factors as obesity, hyperglycemia, inflammation, hypoxia and oxidative stress
Interestingly, social factors e.g. stress, parental neglect, can also play a role.
Genetics brought order within the field of biology.
Every physical aspect of a person was summarized and guided by a simple code embedded in every cell of the body.
The Genetic Dogma
But was that all?
Clearly not as otherwise we should not have this:
Environmental and lifestyle factors can twist, adjust, and move the DNA to express it in different ways even through the same genes
Epigenetic changes can switch genes on or off and determine which proteins are translated.
DNA damage repaired?
Is all DNA replicated?
Is the environment favourable?
Are all chromosomes attached to the spindle?
Continue dividing or stop and differentiate?
Genes Involved in Tumour Transformation
3 types of Genes
3. DNA Repair Genes
1. Tumour Suppressor Gene
A natural occuring derivative of Folic Acid
Folic acid requires transformation in the body - not always possible.
Lack of folate, reduces total DNA methylation but can result in a paradoxical methylation of specific genes.
Genes are switched off when methylated and switched on when demethylated.
spinach, asparagus, broccoli, cauliflower, corn, carrots, celery, beans, peas, lentils, squash, citrus fruit, grapes, banana, avocado, seeds, nuts
An essential amino acid
Major effects of these three agents:
Results in demethylation -
1 alcohol drink per day increase risk by about 7%
Moderation is the key word - one drink a day has health benefits e.g lowers risk of heart disease and hypertension
> 1 drink a day - no benefits
Diagnosis, prognosis and
prediction of treatment outcome
Currently no ideal screening test for young (20-40) women at moderate risk of breast cancer/
Identifying a biomarker for the early detection of breast cancer would be ideal
Study published in 2010 had identified over 700 genes that were either upregulated or downregulated in breast cancer.
Sensitivity (actual positives correctly identified ) = 80.6%
Specificity (negatives correctly identified) = 78.3%.
Mammography - Sensitivity 83 - 95% (lower in younger women, and very low <35 years)
Specificity - >80%
So why not implement it?
Mostly lack of expertise, cost and sensitive material (RNA)
Methylation patterns in cell free DNA
The methylation status of a number genes has already been shown to be able to identify early breast cancer.
One shall be able to identify the presence, type and most probably even spread of breast cancer through a blood test
With this information one can then identify the best way towards and which treatment to give.
Methylation of Tumour Suppressor Gene (TSG) occurs by chance (environmental)
Presence of oncoprotein and suppressed TSG, favours growth of tumour cells.
Oncoprotein targets methylation of TSG
Environment plays a minor role in methylation but would play a major role in oncogene activation
Sources of Folate
or better known as alcoholic drinks
Antagonist to methylation agents e.g folate
Induces global hypomethylation including genes involved in initiation of cell invasion and metastasis
Paradoxical hypermethylation of specific genes in particular genes involved in:
Reduction of cell invasion
Cell cycle regulation
Once cancer has occurred, they can also help in the methylation of estrogen receptor (ER) genes that transform the cancer from ER +ve (better prognosis and responds to anti-hormonal therapy) to ER -ve)
Other important epigenetic changes:
One survival ploy in cancer tissue is Angiogenesis
Switching off angiogenetic genes - reduces cancer risk. Beta-carotene
(= carrots) has this effects as it helps methylate these genes
All tissues require oxygenation but cancer tissue requires more!
Biomarkers for tailored treatment and response
BMRS1 - correlated with poor prognosis
serum RASSF1A DNA methylation shows good response to tamoxifen treatment and favourable prognosis
Patients with methylated PITX2 are less likely to develop distant metastasis - a possibility to spare them adjuvant chemotherapy.
DNA methylation modification as therapeutic target
DNMT inhibitor and demethylating agents e.g. zebularine - inhibits methylation and activates cell stabilising genes (arrests cells in the S-phase)
Old drugs with new applications:
Procaine (local anesthetic) and procainamide, (antiarrhythmic drug), - demethylating activity in cancer cells, leading to the reexpression of silenced tumor-suppressor genes.
EGCG, the main polyphenol compound in
- increases tumour suppressor gene activity.
The distant past was the era of curses and witches,
The present is the era of genetics
The near future shall be the era of epigenetics
Both based on Shakespeare
Totally different films
Obesity and High Fat Diet
In postmenopausal women, adipose tissue is the main tissue producing estrogens.
Estrogens induce the growth of breast cancer.
High level of fat cells (obesity) increases a substance called Leptin.
Leptin stimulates tumour growth
Obesity has been shown to upregulate inflammatory substances that induces growth and angiogenesis
Apart from inducing chronic inflammation, the pro-inflammatory chemicals, switch on of various genes involved in growth and invasiveness of (breast) cancer
Obesity and High Fat Diet