Tumour pathology 4 Flashcards
What can control the cell cycle?
could be external factors - hormones
cytokines
growth factors
could be intrinsic factors - critical checkpoints
where are the three checkpoints of the cell cycle ?
G1 checkpoint - checks the cell size and nutrient supply. (may go to g0)
G2 checkpoint - just after synthesis and before mitosis, checks the DNa to make sure it is undamaged
Metaphase checkpoint - Makes sure the chromosomes have aligned right.
what two things bind at checkpoints, which form a complex that phosphorylates target proteins and causes the next stage of the cell cycle to occur?
CDKS - catalytic sub units
cyclins - regularatory sub units
What controls the binding of CDKS to cyclins?
CDK inhibitors - can prevent them for binding to cyclins - to stop the cell cycle from continuing.
E.g INK4A and KIP families
how does the prb prevent excessive cell growth ?
it binds to E2F, which is a transcription factor. E2F must be free for transcriptn to occur so this prevents transcription
when is prb activating e2f and when is it inhibiting it?
hydrophosphorylated / active prb = inactive e2f
phosphorylated / inactive prb = activated e2f
what is carcinogenesis?
production of cancer cells caused by mutation of genetic material
what two pathways are frequently disrupted, causing carcinogenesis?
cyclin prb pathway, since prb regulates the transcription factor e2f and stops cell division from occurring, if it is mutated the cell may proliferate uncontrolled
p53 - p53 is usually responsible for apoptosis, arresting the cell cycle or DNA repair, so if its mutated then DNA damaged cells may proliferate and form malignant neoplasms
what are the major aetiological causes of cancer?
inherited dispositions proto-oncogens -> oncogene mutations environmental agents - chemical - radiations oncogene viruses
what are damaged by chemical and radiation environmental agents?
Purine and pyridemine.
