Flashcards in Food and Cancer -L9 Deck (45)
How many different types of cancers are there?
cancer is a collection of related diseases of about >200
Why do most cancers start in epithelial cells ?
because this cell type divides more often
What are the important aspects of cancer?
requires multiple mutations - within DNA
uncontrolled cell division as cells dont respond to stop signals
may damage surrounding organs- this is when tumours start being a problem
metastasis- causes serious problems
process of initiation of tumours in an organism
tissue composed of cells that deviate from normal program of cell division and differentiation
define benign tumour:
tumour cells remain in a single mass and do not invade or disrupt surrounding tissues
define malignant tumour:
tumour cells invade and disrupt surrounding tissues
spread of malignant tumour cells throughout the body - normally through blood and lymphatic system
What does it mean by cancer cells are defined by their origin ?
they will act like the cell type from their origin wherever they appear
e.g. breast cancer cells act like breast cancer cells wherever they are
What pathway can lead to cancer ?
1) mutation inactivates TSG
2) cell proliferates
3) mutations inactivates DNA repair gene
4) mutation of proto-oncogene creates an oncogene
5) mutation inactivates several more TSG
What mutations most commonly occur in cancers?
most cancers result from mutations in cellular genes
other cancers are caused by viruses - viruses can insert their DNA into our DNA
- mutations occur in genes involved in cell division
What are cancers of epithelial cells, bones and muscle cells?
bone and muscle= sarcomas
How much of cancers are sporadic ?
- only a small proportion are genetically related
What does cell differentiation correlate with ?
loss of ability to proliferate - highly specialised cells are terminally differentiated
What is required for a cell to undergo differentiation ?
it has to divide and during this it alters itself, altering the proteins it is going to produce
but once a cell is terminally differentiated then it will no longer divide because it is highly specialised - they are replaced by new cells
What signalling molecules control normal cell cycle ?
growth factors- stimulate cell division
growth-inhibiting factors- inhibit cell division
What signals are cancer cells unable to respond to ?
unable to respond normally to intra-cellular and/or extracellular signals that control cell proliferation, differentiation and ultimately cell death
What are the frequency of genetic mutations that can occur in different types of cancer ?
can be as few as 2 to at least 6 mutations - likely that more occur during the disease to increase malignancy
Why do not all mutations lead to cancer?
sometimes mutations can be fixed, may not cause a change, some are beneficial (evolution), majority of DNA is not involved in cell division
What are the 6 stages of cancer progression ?
1) loss of growth signal automomy
2) evasion of growth inhibitory signals
3) evasion of apoptosis
4) unlimited replicative potential
5) angiogenesis- tumours develop blood supply which is a key part to tumours being successful
6) invasion and metastasis
According to the IARC how many factors are there that are carcinogenic to humans ?
- many are related to occupation
- many are unavoidable
Not all mutations will lead to cancer because...
-mutation is repaired
-mutation is not repaired but it is not in a "bad" place
-mutation is in a bad place is not recognised but is dealt with and recognised by defines systems
How many mutations occur in our DNA everyday ?
10,000 mutations per day in human
1 in 1000 in these changes survives because they are repaired by one of a number of different DNA repair enzymes - these are critical
What would a a really bad thing associated with DNA repair systems?
if they suffered mutations and their efficiency was reduced- defects or inefficiencies of the DNA repair system will increase the number of mutations increasing the likelihood of cancer
HOWEVER stimulating their efficiency would be a good thing
What is one of the most common inherited cancer syndromes?
hereditary non-polyposis colon cancer
results from defects in mis-match repair- with at least 5 different mismatch repair genes involved
- it develops at an early ages
What 3 types of genes are frequently mutated in cancer?
1) proto-oncogenes to oncogenes
2) Tumour suppressor genes
3) genes linked to mutation rate- any gene that increases mutations occurring
How many different oncogenes have been discovered and what is their purpose?
about 100 different oncogenes
all proto-oncogenes are involved in positive control of cell growth and division
What are the 2 classes of proto-oncogenes?
growth factors= regulatory genes involved in the control of cell multiplication
protein kinases= add phosphate groups to target proteins, important in signal transduction pathways
How were oncogenes originally discovered?
discovered in tumour-causing viruses but then found to be similar to or derived from genes present in animal host cells called proto-oncogenes