genetic causes Flashcards
carcinogenesis
multistep process, carcinogens don’t immediately produce tumours. The carcinogen induces the initiation step
initiator promotor experiment
when painted with initiator then promotor then more initiator on the papilloma, carcinoma formed
examples of initiators (5)
- chemical carcinogens
- viruses
- Radiation, UV
- replication errors
- unknown factors
what is the sequence of events for initiators and promotors
initiation is rapid and when it takes place the cell can persist for long periods of time, initiated cells are latent until acted upon by promotor.
examples of promotors (3)
- inflammation
- hormones
- normal growth promotors
Foulds 1957
tumour progression occurs in a stepwise fashion. This is due to mutations, loss or activation of genes
what is a polyclonal tumour
tumour originating from multiple cells
what does it mean to say that a tumour is monoclonal
all the cells in a tumour distend from a single cell
what causes polyclonal tumours
rapidly transforming RNA tumour viruses, hereditary syndromes
what type of tumours are most spontaneous
monoclonal
what does it mean to say that tumours are heterogenous?
they continue to evolve
how do many tumours evolve?
branching evolution, this creates extensive intra- and inter-tumour genetic heterogeneity
why are properties of tumour cells clonally inherited
they result from genetic alterations within a cell
what else can underlie some of the changes in malignant cells
epigenetic changes
what type of process is the growth of tumours
Darwinian
