Topic 8- Epigenetics and cancer Flashcards
What are the two properties of cancer cells?
-Unregulated cell proliferation- growth and division
-Metastasis- ability to spread to other parts of the body
What are tumors?
Groups of abnormal cells that form lumps or growths
How can both benign and malignant (non-cancerous and cancerous tumours) cause damage to the body?
-Damaging the organ in which the tumour is located
-Causing blockages or obstructions
-Damaging other organs by exerting pressure
-Taking nutrients such as oxygen +glucose and using it for their growth
How do malignant tumours cause cancer?
Growing rapidly, then invading and destroying surrounding tissues
How can metastasis occur?
-Cells can breaks off and then travel through the bloodstream or lymphatic system
What is the formation of malignant tumours usually initiated by?
Carcinogens:
-UV or X-ray exposure
-Tobacco from cigarettes
-Asbestos
-Processed meat
What is the formation of benign tumours usually initiated by?
-Inflammation or infection
-Injury
-Diet
-Genetics
-Toxins and radiation
Give some properties of benign tumours which are also different (in comparison to malignant)
-Grow very slowly
-Cell nucleus has a relatively normal appearance
-Cells often specialised
-Produce adhesion molecules to remain within the tissue they formed in
-Surrounded by a capsule
-Localised effects on the body
-Removed by surgery alone
-Rarely reoccur
Give some properties of malignant tumours which are different (in comparison to benign)
-Grow rapidly
-Cell nucleus is often larger + appears darker due to an abundance of DNA
-Cells are unspecialised
-Do not produce adhesion molecules so can metastasise and form secondary tumours
-Not surrounded by capsule so can grow finger-like projections into surrounding tissues
-More likely to be life-threatening as abnormal tumour tissue replaces normal tissue
-Often have systematic (whole body) effects
-Removal usually involves surgery and radio/chemotherapy
-More frequently reoccur
Where do hereditary mutations exist?
In all body cells
Where do acquired mutations exist?
In the cell it occurs in and the offspring
Mutation of any genes controlling the 1.___ ____ can contribute to the devolpment of cancer
- Cell Cycle
What are the two types of cell cycle-regulating genes?
-Proto-oncogene
-Tumor supresser gene
What is the function of a proto-oncogene?
Stimulates cell division by producing proteins that will make cells divide
What is the function of tumour suppressor genes?
Slows/inhibits cell division by producing proteins (that encode for DNA repair,slowing the cell cycle by ensuring checks are made,signalling apoptosis (cell death) when the cell is faulty) that stop cells dividing /cause them to undergoe cell death (apoptosis)
How does an oncogene cause cancer?
-If a mutation occurs and the proto-oncogene is overexpressed/ cannot be transcriptionally suppressed at the correct time
(proteins that stimulate cell growth and division to be constantly activated when these proteins are activated, the cell cycle is sped up, If the proteins involved in apoptosis are also mutated, this can lead to tumour formation)
-Uncontrolled cell proliferation can occur
How does a tumor suppressor gene cause cancer?
-If a mutation occurs cells are not able to normally respond normally to cell cycle checkpoints
-Uncontrolled cell proliferation can occur
Explain how increased methylation of oncogenes stops cell division.
-Makes histone proteins wrap more tightly
around DNA
-So transcription factors (TF) cant bind and therefore cannot be transcribed
-RNA polymerase cant bind
Explain how decreased methylation of TSG can be used as a cancer treatment
-Histones are less tightly wound around DNA
-So more accessible to TF
-RNA polymerase can bind
Explain how increased acetylation of TSG can be used as a cancer treatment
-Histone proteins are not wound as tightly around DNA
-So TF can bind
-RNA polymerase can bind
Explain how decreased acetylation of oncogenes can be used as a treatment for cancer
-DNA and histones are more tightly wound
-TF cant bind
-RNA cant bind
How can acetylation and methylation of oncogenes cause cancer?
-Increased acetylation
-Decreased methylation
How can acetylation and methylation of TSG cause cancer?
-Decreased acetylation
-Increased methylation
Explain how hormone-sensitive cancer cells (eg. breast cancer) cause cancer
-Contain receptor proteins that become activated when hormones bind to them
-Activated receptor protein releases their inhibitor molecule
-Then act as a transcription factor to increase expression of specific genes
-Too much of this can lead to uncontrolled cell proliferation
Explain how drugs such as tamoxifen interfere with oestrogens ability to stimulate the growth of cancer cells
-(Tamoxifen) binds to oestrogen receptors preventing oestrogen from binding
-This inhibits transcription of genes associated with cell growth and division
