Part 4 - oncogenes!!!! Flashcards
What are the two gene types affected in cancer?
Oncogenes and tumour-supressors
Three things that cause cancer:
Chemical carcinogens - damage to DNA!
Harmful irradiation - DNA damage!
Tumourigenic viruses - integration of viral genome into our cells
What may happen if there is a lot of DNA damage?
Cell may rush to repair the damage, thus making mistakes which introduces mutations.
What are oncogenes?
A gene that has the potential to cause cancer. Cause a gain of function.
What are proto-oncogenes?
A normal gene that could become an oncogene with mutations/increased expression. Code for proteins that regulate cell growth and differentiation.
What are four examples of oncogenes?
c-erbB2, Ras, PI3-K, Myc
Three examples of tumour-suppressors?
p53, Rb, APC
What does heterogeneity mean when refering to a tumour?
There are different cell types that make up the tumour (this links to chemotherapy - one mutated cell type may respond, but not another)
What are Ras/PI3-K?
Ras - small GTPase, involved in oncogenesis
PI3K - main effector pathway - regulates cell growth/cell survival
What is telomerase and what does it have to do with cancer?
An enzyme that adds DNA onto the ends of telomeres. In cancer, telomerase is over-expressed.
What are driver and passenger mutations?
A driver mutation defines what type of cancer it is. A passenger mutation does not define the cancer but it contributes to malignant growth (and metastases!)
What cell type is cancer defined to?
Epithelial cells (GIT, resp T). Apical and basal membranes.
What happens when there is no space for cancer cells to grow?
They grow in a ‘clump’. Those cells lacking access to nutrients/oxygen secrete growth factors - this results in neovascularisation.
Eventually, the cells break off and produce enzymes to break through the membranes of other organs –> metastases.
Main classes of oncogenes:
Growth factor receptors
Nuclear proteins (myc, MDM)
Cytoplasmic Ser/Thr/Tyr
G proteins etc.
What are common properties of tissue stem cells and cancer stem cells
Self renewal Proliferative quiescence Multipotency Persistance Drug resistance Infrequent
