Cancer Flashcards
What is cancer the result of?
Mutations in the genes that regulate mitosis
If mitosis is not regulated, what does this lead to?
uncontrollable cell division/ growth thus creating a tumour
What is a benign tumour?
non-cancerous
What is a malignant tumour?
cancerous
What makes a benign tumour non-cancerous?
Adhesion molecules produced so they stick and to a particular tissue –> do not move
Capsule - remain compact, do not spread and can often be removed by surgery –> rarely return
So the impact of the tumour is localised and is often not life-threatening.
Explain the growth of a benign tumour?
They can grow large but they grow at a very slow rate.
What are the properties of malignant tumours?
They are cancerous
Grow large rapidly
The cell nucleus becomes large and the cells can become unspecialised again
They do not produce adhesive, so the tumour can metastasise which means that the tumour can break off and spread to other parts of the body
Not contained within a capsule/membrane
So they can grow projections into surrounding tissues and develop its own blood supply
Can be lifethreatening and removal requires surgery and supplementary treatment e.g. radio/chemotherapy
Recurrence is more likely
What are oncogenes?
The mutated version of a proto-oncogene. Proto-oncogenes create a protein which initiates DNA replication during interphase of the cell cycle so that mitosis can occur when the body needs to make new cells, however the mutation of proto-oncogenes can result in this process being permanently activated so cells continually divide.
What two genes control mitosis?
Proto-oncogenes
Tumour suppressor genes
What do tumour suppressor genes do? (TSG)
They produce a protein which slows down cell division and causes cell death (apoptosis) if DNA copying errors are detected.
What happens if aTSG becomes mutated?
Mutation leads to the transcription of the TSG becoming inhibited so the TSG will not produce the protein which slows down cell division - so it continues and mutated cells would not be identified and destroyed so leads to uncontrolled cell division.
Describe how abnormal methylation leads to the TSG to be turned off?
Hypermethylation - increased number of methyl groups are added to the TSG resulting in the gene becoming inactivated and turned OFF.
Describe how abnormal methylation leads to proto-oncogenes being turned off?
Hypomethylation occurs - a reduced number of methyl groups are added to the oncogenes which results in the gene being permamnently switched ON. So lots of proteins being made which initiate the cell cycle
Why is oestrogen produced and what produces it?
Produced by the ovaries to regulate the menstrual cycle but stops getting produced after the menopause
After the menopause, what produces oestrogen?
Fat cells in the breast tissue - this has been linked with causing breast cancer in women post-menopause
