Cancer Flashcards
What two factors can cause cancer?
Environment
Genetics
What are somatic mutations?
Mutations in nongermline tissues
Noninheritable
What are germline mutations?
Mutation in germline mutations
Heritable
What are proto-oncogenes?
Normal genes that code for proteins that regulate cell growth and differentiation
What are oncogenes? When do these genes cause cancer?
Proto-oncogenes with a mutation
Accelerate cell division
Cancer arises when the oncogenes are stuck in ‘on’ mode
How many ‘hits’ are needed for oncogenes to cause cancer?
One mutation
As they are dominant in effect
What are tumour suppressor genes? When do these genes cause cancer?
Genes that regulate a cell during cell division and replication. They regulate cell division by either inhibiting the cell cycle or promoting apoptosis.
Cancer arises when the genes are mutated, as this means cell division and replication won’t be regulated and the cells will grow uncontrollably
How many ‘hits’ are needed for tumour suppressor genes to cause cancer?
Two mutations
As they are recessive in effect. Therefore they fit the “two hit” hypothesis
What are DNA damage-response genes? When do these genes cause cancer?
DNA damage response genes are the genes that are involved in coding for key enzymes involved in repairing DNA when it is damaged.
Cancer arises when the genes are mutated in a way that results in the proteins not being formed or having no function. This results in there being an accumulation of mutation in other critical genes
What are monoclonal cancers?
Cancers that arise from a single cell
What is a carcinoma?
Type of cancer that starts off from the disorderly growth of epithelial cells in the skin or tissue lining organs.
These epithelial cells can then invade adjacent tissues and spread by the lymphatic and blood vessels to other parts of the body.
Describe the features of normal cells.
Normal cells are spaced out in a uniform manner
A few of the cells are mitoses, which means that few cells are going through the cell cycle
Oncogene expression is rare within normal cells and there is a presence of tumour suppressor genes
Normal cells also secrete growth factors, which is done in a co-ordinated manner.
Describe the features of cancerous cells.
Loss of contact inhibitor and are not uniformed
A lot of cells are dividing, which means that there are frequent mitoses and a lot of the cells are in their unstable state
There is also an increase in oncogene expression and a loss of tumour suppressor genes.
They also secrete growth factors at an increased rate
Lots of blood vessels surroundings the cancerous cells as they require a lot of oxygen and nutrients in order to grow and divide as frequently as they do
Describe the multi-step process of tumour formation.
Initiation - mutation occurs within a single cell that results in its ability to no longer respond to normal cell signals.
Promotion - the cell divides to form a number of other abnormal cells.
Tumour growth - Which is when the abnormal cells stick together to form mass of abnormal cells
The above stages are pre-clinical stage
Progression - tumour metastasises and spreads to other parts within the Boyd.
The above stage is the mass can now be detected.
What is the diagnostic threshold?
The number of cancer cells it takes in order for the cell to be clinically detectable.
Ideally, we want to detect the cancer as close to the diagnostic threshold as possible.
What causes the initiation stage?
Chemically, physically or virally caused.
What causes promotion?
Growth factor or oncogenes.
What are growth factors?
Growth factors are polypeptide molecules that regulate cell growth and function.
They do this binding to cell membranes and receptors and stimulating the activation of intracellular signal transduction pathways.
What two ways are growth factors stimulated?
Autocrine
Paracrine
What is autocrine stimulation?
When a cell secretes a hormone or chemical messenger that binds to autocrine receptors on that same cell. This leads to the secretion of the growth factor.
What is paracrine stimulation?
When a cell produces a signal to induce changes in nearby cells, causing them to secrete growth factor
What is the most common tumour suppressor gene?
p53 gene
What two things commonly mutate tumour suppressor genes?
DNA damage
Hypoxia
What causes progression? What does this step involve?
Metastasis
When the cancerous cells spread from the blood vessels to a tissue and start to divide, forming a secondary tumour
What step occurs before metastasis? What does this step involve?
Invasion
When the cancerous cells invade through the basement membrane, which allows them to move into the surrounding tissue. They then invade blood vessels
What three enzymes are involved in the invasion of cancerous cells?
Matrix metalloproteinases
Plasmin
Cathespin
What are the role of the enzymes involved in the invasion of cancerous cells?
Destroying cell adhesions in the extracellular matrix so that the cancerous cells can move between them
What three enzymes are involved in the cells adhering onto another organ?
Cadherins
Integrins
CD44
What is angiogenesis? How does it occur?
The formation of new blood vessels
The degradation of the extracellular matrix, which means that there is space for the blood vessels to grow
When does angiogenesis occur? Why?
After progression
Supplies the cancerous cells with the nutrients it needs to grow
What is VEGF? What is its role?
Vascular endothelial growth factor
Massive role in the promotion of cancer cells