molecular pathology of tumours

Question 1

what is an oncogene?

Answer 1

a mutated form of a protooncogene, the effect of the mutated gene means that the cell undergoes excessive cell survival and proliferation (only one form of the gene needs to be mutated) - proto oncogenes are ACTIVATED

Question 2

what is a tumour suppressor gene?

Answer 2

a gene which usually prevents cells from undergoing abnormal proliferation - mutation needs to happen in both forms of the gene for control to be lost - tumour suppressor genes are INACTIVATED

Question 3

what happens when the protein coded for by the TUMOUR SUPPRESSOR GENE for retinoblastoma (Rb) is mutated?

Answer 3

the cell cycle passes the ‘R’ checkpoint without inhibitoon. The active form of the Rb protein usually prevents transcription of the genes for entry into S phase of the cell cycle

Question 4

what are gatekeeper genes?

Answer 4

genes which inhibit proliferation or promote the death of cells, especially those with DNA damage

Question 5

what are caretaker genes?

Answer 5

maintain the integrity of the genome by promoting DNA repair

Question 6

is p53 a gatekeeper or caretaker gene?

Answer 6

both!

Question 7

what does telomerase do for tumours?

Answer 7

allows limitless replication of cells - usually cells reach a ‘crisis’ point when it can’t replicate anymore because it doesn’t have any telomeres on its chromosomes by telomerase overrides this point

Question 8

what is the signalling molecule that results in the angiogenesis signalling cascade?

Answer 8

VEGF

Question 9

what are the four steps that allow cancer cells to migrate through the basement membrane?

Answer 9

detach from each other (maybe due to reduced adhesiveness)
they then attach to the BM via laminin and laminin receptors
the secrete proteolytic enzymes
degradation of the BM follows and tumour cells migrate