What Is Cancer? Flashcards
What is cancer ?
Cancer arises from abnormal, purposeless & uncontrolled division of cells that then invade + destroy surrounding tissues. Aka grp of diseases caused by normal cells changing so that they grow in an uncontrolled way
What is meant by the term malignant tumour
Normal cells need signals to survive. How about cancer cells?
Normal cells need signals to survive. Cancer cells can survive without them
What is telomerase, we know mutations in telomerase can cause cancer.
Telomerase= enzyme responsible for maintenance of length of telomeres by addition of guanine-rich repetitive sequences i.e. it protects the ends of chromosomes
Telomeres maintain genomic integrity in normal cells, and their progressive shortening during successive cell divisions induces chromosomal instability. In the large majority of cancer cells, telomere length is maintained by telomerase. Thus, telomere length and telomerase activity are crucial for cancer initiation and the survival of tumors i.e. we must
Describe interrupted life cycle of cancer cells
Compare normal cells to cancer cells
Define angiogenesis and why it’s seen in cancer cells
What effect do growth inhibitory signals have on cancer cells
Cancer cells are unresponsive to growth inhibitory signals
Define METASTASIS
Spread of a malignant tumour from its site of origin. This occurs 3 ways;
• through bloodstream (haematogenous)
•through lymphatic system
• across body cavities (through peritoneum)
- carcinomas generally metastasise via lymphatics, sarcomas via bloodstream
Define proto- oncogenes
How do proto-oncogenes become oncogenes
Define oncogenes
What happens when we get a mutation in the HER2 receptor (member of a tyrosine kinase receptor) on the transmembrane protein. After growth factor binds to a receptor and activates a signalling pathway
• a signalling protein e.g. epidermal growth factor binds and activates growth factor receptor
•if we have mutation in HER2, when the growth factor binds there’s an initiation: autophosphorylation of tyrosine, 20 different tyrosines on receptor will be phosphorylated (depending on growth factor, what other signalling proteins there are)
• tyrosine kinase HER2 receptor changes shape = activated= enhance kinase activity
=leads to uncontrolled cell growth, excess cell division leading to TUMOUR
What does enhanced kinase activity lead to
Enhanced kinase activity leads to uncontrolled signalling~> tumour formation ~> excess cell division + uncontrolled cell growth
List the 5 types of ONCOGENES
• growth factors (signalling proteins)
• receptors (e.g. tyrosine kinase receptors)
• intracellular signalling proteins e.g. kinases
• transcription factors
• anti-apoptotic proteins
What is an ‘abnormal’ cell
A cell that carries mutations
Define oncogenesis
Development of new or abnormal growth (benign or malignant tumour)
What do tumour suppressor genes do when switched on
When switched on TSGs restrict cell proliferation by:
• restricting/ controlling cell cycle + division
• inducing apoptosis in cells w mutations (when other mechanisms e.g. DNA repair have failed)
• they encode proteins which INHIBIT cell growth
What do tumour suppressor genes require to cause cancer
Both copies of a specific tumor suppressor gene pair need to be mutated to cause a change in cell growth and tumor formation to happen
TSGs are deactivated as a result of _____ which leads to _______
TSGs are deactivated as a result of mutation which leads to cell dividing uncontrollably = may drive cell into oncogenesis
Mutations in tumour suppressor genes
• mutations act recessively (both copies of TSG pair mutated) to release cells from growth control = increases probability mutant cells will become tumour cells
• increase probability of mutations in other genes
• may prevent apoptosis or allow cell devision of mutant cells
• this means cells can become immortal = cancer as DNA damage is not repaired n cell is dividing
Unlike proto- oncogenes, where _________ mutated copy of proto-oncogene can have dominant, growth promoting effect on a cell) in tumour suppressor genes_______________
Unlike proto- oncogenes, where SINGLE mutated copy of proto-oncogene can have dominant, growth promoting effect on a cell) in tumour suppressor genes 2 COPIES OF MUTATED GENE RESULTS IN LOSS OF FUNCTION (I.e. both copies of gene need to be mutated for effect of mutation to be seen in TSG)
2 types of tumour suppressor genes
1)CARE TAKERS = maintain genetic stability. Encode proteins involved in the repair of DNA
2) GATE KEEPERS= induce APOPTOSIS or inhibit cell proliferation by restricting cell cycle + division = encode proteins that inhibit cell growth. Check point control genes
Define proliferation (in terms of cancer)
rapid increase in the number of cells
