Session 11 - Neoplase III Flashcards
What is carcinogenisis?
Study of causes of cancer
Three intrinsic factors which lead to canc
Age
Sex
Heredity
What two factors account for cancer risk?
A combination of intrinsic host factors such as heredity, age and gender (especially hormonal),and extrinsicfactors related to the environment and behaviour
What are extrinsic causes of cancer?
Environment and lifestyle
What are the three main categories of extrinsic cancer risk?
Chemicals, radiation and infection
What are the five leading behavuioural and dietary risks
High BMI Low fruit and vegetable intake Tobbaco use Alcohol use Lack of physical activity
What are the two factors which are key to carcinogenesis?
The prescence of initators and promoters
What are initators?
Mutagens/carcinogens
What are promoters?
Substance which cause prolonged proliferation in target tissues
What does initiator and promoter action culminate in?
Amonoclonal expansion of mutant cells, and then become fully malignant via progression
Give three examples of inherited susceptibilty to the development of tumours
Retinitis (Xeroderma) Pigmentosum
Ataxia Telangiectasia
Fanconi’s Anaemia
What is retinitis (Xeroderma) pigmentosum
Increased risk of skin cancers when exposed to UV rays in sunlight
What is ataxia telangiectasia?
Defective response to radiation damage, profound susceptibility to lymphoid malignancies, usually die before age 20
What is fanconi’s anaemia?
Sensitivity to DNA cross-linking agents, marrow hypo function and multiple congenital anomalies, predisposition to cancer
Give three cancers and the genes they’re associated with
Familial Adenomatous Polyposis - APC
Breast Cancer - BRCA1/2
Li Fraumeni Syndrome - p53
What is a proto-oncogene?
A normal gene that can become an oncogene due to mutations or increased expression
What are the normal roles of proto-oncogene, and what about their DNA sequence makes them suspicous
Proto-oncogenes are present in all normal cells, and are involved in normal growth and differentiation.
They have a DNA sequence identical to viral oncogenes.
How can proto-oncogenes be modified to become oncogenes?
Mutation, amplification, translocation
What is the name of oncogene products?
Oncoproteins
What do oncoproteins from oncogenes allow the cell to do
To escape normal growth control, becoming self sufficient without external signals required to grow
Why are proto-oncogenes easily mutated to neoplasia? `
Only one allele of a proto-oncogene needs to be mutated to cause neoplasia
What is a tumour supressor gene?
A gene that encodes proteins that suppress growth and therefore cancer
What do tumour supressor genes do in cells?
Produce proteins which supress growth
What does loss or alteration of tumour supressor gene cuase to happen?
Loss of growth supression
What has to happen to tumour supressor genes in order to produce neoplasia?
Both alleles need to be mutated (2 hit hypothesis)
What is the two hit hypothesis?
Both alleles of a tumour supressor gene to be mutated in order for neoplasia to develop (suprresion rather than production)