Cancer Flashcards
Causes of cancer
- Environmental carcinogens
- Viral infections
- Genetic instability
- Inherited factors
What was the first tumour-causing virus that was discovered?
Rous Sarcoma virus
Why is RSV tumour-causing?
The presence of DNA sequences from the chicken genome - the v-src oncogene
Which oncogene is associated with RSV?
v-src oncogene
What does v-src encode?
An abnormally hyperactive version of tyrosine kinase
What codes for a normal version of tyrosine kinase?
The c-src proto-oncogene
What does the c-src proto-oncogene code for?
A normal version of tyrosine kinase
What is chromosomal translocation?
The disruption, truncation or reassembly of genes on chromosomes
What can chromosomal translocation of proto-oncogenes lead to?
Cancer
Which chromosome is associated with chronic myeloid leukaemia?
The Philadelphia chromosome
What translocation is taking place on the philadelphia chromosome?
BCR from chromosome 22
ABL from chromosome 9
What is BCR-ABL?
Present on the translated chromosome, it encodes a hyperactive version of tyrosine kinase
What does ABL code for?
Tyrosine kinase
Examples of proto-oncogenes –> oncogene
ABL and BCR –> BCR-ABL
What is a retinoblastoma?
A rare retinal tumour that can be either hereditary or non-hereditary
When are retinoblastoma always hereditary?
When they are bilateral
Hereditary of unilateral retinoblastomas
Can be either hereditary or non-hereditary
What is retinoblastoma caused by?
Loss-of-function mutation in both alleles of a tumour suppressor gene - normally prevents cells from becoming cancerous
Why might someone be more likely to acquire a tumour?
If hereditary, already have one mutation present so only need one more sporadic mutation
What kind of mutation causes cancer from proto-oncogenes?
Dominant and gain-of-function mutations
What kind of mutation causes cancer from tumour suppressor genes?
Recessive and loss-of-function mutations
Which kind of genes do dominant, gain-of-function mutations affect?
Proto-oncogenes
Name the 4 plasias
- Neoplasia
- Hyperplasia
- Metaplasia
- Dysplasia
What is is neoplasia?
Invasive, abnormal tissue growth
What is hyperplasia?
Tissue growth containing excessive number of cells
What is metaplasia?
Tissue growth containing displaced and normal cells
A change in cell differentiation
What is dysplasia?
Tissue growth containing cells that look abnormal under a microscope
What is a benign tumour?
Tumour that is well-confined and local. Surrounded by a basement membrane so unlikely to spread
What is a malignant tumour?
Tumour that breaks through the basement membrane and can spread
What is metastasis?
The development of a secondary tumour at a distance from the primary growth
What is anaplasia?
When cells only poorly differentiate
