What is cancer? Flashcards
(31 cards)
What is cancer?
uncontrolled growth of abnormal cells in a tissue, invasive and metastasising (seeded to other parts of the body)
A metastasised cancer is more challenging to treat and can only be treated systemically
What is the origin of cancers?
tumours arise from normal tissues
- can arise form nearly all specialised cell types throughout the body
- different tissues have diff combos of genes being transcribed
- even within the same tissue, diff combo of genes are transcribed at different stages of differentiation
What cell type do the majority of cancers arise from?
epithelial cells - mostly exposed to external environment e.g. GIT and lungs
What are carcinomas?
Squamous cell carcinoma=lining epithelial cells - most common
Adenocarcinoma=secreting epithelium
Other than carcinomas, what other cancer types are there?
Sarcomas=from mesenchymal cells
Leukaemias= from haemoatopoietic tissue and cells of immune system -lymphoid and myeloid tumours
What types of tumours do children appear to be more susceptible to?
Brain tumours (gliomas and neuroblastomas) and lymphocytic leukaemia
What do tumours look like?
material tends to look undifferentiated
cells in the lumen look disorientated which could be hyperplasia (not yet a tumour)
What does metaplasia mean?
Change from on differentiated form to another
What does neoplasia mean?
Doesn’t mean cancer, it just means excess growth
What are polyps?
pre-invasive adenomas- greater chance of developing as we age
What are the basic causes of cancer?
A genetic disorder at the cellular level
- chromosomes are altered in most types
- radiation can disrupt chromosomal structure leading to the cell dying
What happens in T cell prolymphocytic leukaemia?
chromosome translocations - cell survives and proliferates
- single translocation was the initial change but then more genetic changes occur over years causing damage to nearly all T-cells
What is an oncogene?
Positive regulator of cell growth - makes cell grow
even when only one allele is mutated
What happens when replicative immortality is activated?
circumvention of senescence and crisis
increased expression and activity of telomerase= an enzyme which keeps cell out of senescence
What type of disorder is cancer and what happens?
it is a genetic disorder of monoclonal growth- damage occurs in one cell initially and then this further proliferates (progeny of that one original cell)
- NO such thing as a polyclonal tumour
An individual or even an individual tissue can have multiple tumours but it is very rare and each tumour is monoclonal
When you stain a tumour with G6PD what do you expect to see?
expect the staining to be exactly the same in each cell of the tumour
Where can mutations occur?
in germline cells - inherit a mutation which predisposes you to a tumour
in somatic cells - vast majority are within these types of cells and in the elderly
What are some examples of tumour suppressor genes and oncogenes mutated in germline cells and some conditions associated with germline mutations?
TSG= Rb gene, BRCA1
Oncogene=H-ras
Costello syndrome, Rhabdomyosarcoma, ganglioneurolastoma
What are some examples of tumour suppressor genes and oncogenes mutated in somatic cells?
TSG= Rb again, APC Oncogene= cMyc, c-Abl
A defective RB1 gene causes?
Familial retinoblastoma
A defective TP53 gene causes?
Li-Fraumeni
A defective APC gene causes?
Familial adenomatous polyposis coli
Defective MLH1, MSH2, MSH6, PMS1 or PMS2 genes can cause?
Hereditary non-polyposis colorectal cancer
What happens if you inherit a mutant Rb allele?
Familial inheritance - doesn’t be you have retinoblastoma because you need both alleles to be mutated but because you’ve already inherited one mutant allele you are at increased risk of developing retinoblastoma
Whereas in sporadic retinoblastoma, you would need to lose the function of both Rb alleles in the same cell to develop the condition
