Cancer Lectures Flashcards
Which are the most common cancers?
Breast
Lung
Colon and rectum
Cancer deaths however:
Lung
Colon and rectum
Liver
What is a gene?
Section of DNA that codes for a protein
Strands of DNA that contain many genes = chromosomes
How are proteins made?
Via transcription and translation
Gene is copied into RNA (transcription). This is translated from mRNA to build a protein molecule (translation)
What are Introns and Exons on DNA?
Introns = non-coding DNA
Exons = coding sequences of DNA
What is the difference beween germline and acquired mutations?
Germline mutations - mutations to the germ cells - which means they can be inherited from parent to offspring.
Acquired mutations occur to somatic cells - are not inherited.
What is a mutation?
A change to DNA that ultimately changes the resultant protein - can impact on its structure and/or its function.
How can we test for mutations?
Gene panel testing - tests for a single gene mutation
Whole exome testing - tests the entire specific coding area
Entire coding sequence - exome plus junk DNA
What is the difference between a synonymous and a non-synonymous change to DNA
Synonymous changes to DNA don’t cause a corresponding change to an amino acid produced
Non-synonymous changes - do cause an AA change
Occurence of these can reflect the incidence of natural selection.
What are silent mutations?
Mutations that don’t cause disease and are therefore tolerated.
What are pseudogenes?
Segments of DNA that resemble a gene but are not actually capable of coding for a protein - often derived from genes that have lost their coding ability over the process of evolution.
Mutations in which genes can cause a predisposition to cancer?
Mutations in proto-oncogenes and tumour suppressor genes.
What are
- Proto-oncogenes
- Tumour Suppressor Genes
Proto-oncogenes control cell growth - gas pedal - if mutated they make the cell divide uncontrollably (become oncogenes)
Tumour suppressor genes - have a negative effect on cell growth - they turn cell growth off. If mutated they stop working, and therefore cell growth isn’t turned off.
What are SNPs?
Single nucleotide polymorphisms
Ie. genetic variation of a single nucleotide.
Can act as biological markers - can relate to genes associated with disease (inc cancer).
Can also be synonymous or benign (i.e. tolerated)
Which are the most commonly inherited cancers?
Retinoblastoma
Phaeochromocytoma
Ovarian cancer
What are Cancer Predisposition Genes?
Germline gene mutations which inc risk of cancer.
Which inherited mutation of an oncogene is strongly linked to medullary thyroid cancer?
Multiple Endocrine Neoplasia Type 2 (MEN2A)
When should you suspect MEN2A mutation?
What type of gene is mutated in MEN2A?
When 2 or + endocrine tumours occur together
A proto-oncogene calle RET (tyrosine kinase receptor)
What is a clinical example of a mutation to a tumour suppressor gene?
Retinoblastoma
How can you identify retinoblastoma clinically?
White reflex replaces the red reflex of the eye.
What is the two hit theory of cancer causation?
That you need two mutations (one to each allele of a gene) in order for a cell to become cancerous. In normal cells = this requires two “hits”/damage before this occurs.
In cells with an inherited disease that has damaged one of the alleles - you only need one hit to get disease - therefore makes it much more likely.
Name any tumour suppressor genes that you know.
TP53 (somatic mutation)
BRCA 1 &2 (germline)
MLH1 (somatic or germline) - mismatch repair gene
What can a mutation in BRCA1 or 2 lead to increased risk of?
F - inc risk of breast and ovarian cancer
M - inc risk of prostate and male breast cancer
What is Li Fraumeni Syndrome?
AD mutation of TP53 - tumour suppressor gene
Linked to high rates of osteosarcoma, soft tissue sarcoma, acute leukaemia, breast, brain and adrenal tumours
What is epigenetics used for?
Is the process of how cells control gene activity without changing the DNA sequence. Modifies the DNA chain by methylation, histone proteins modification, chromatin remodelling and mRNA mechanisms.
What factors might modify epigenetic patterns?
Diet
Obesity
Physical activity
Smoking
Alcohol
Environmental pollutants
Stress
Night shift patterns
What do the following do:
- Activated Epigenetic Modifiers
- Suppressive Epigenetic Modifiers
Which viruses are thought to be potentially carcinogenic?
Epstein Barr
Hepatitis B
HPV
What is the difference between a
- direct carcinogen
- procarcinogen
- cocarcinogen
- Directly cause cancer
- Cause cancer due to changing during metabolism
- Cause cancer by acting with another chemical
How do reactive oxygen species damage DNA?
Can cause oxidised DNA bases -> misfiring of bases -> mutations.
ROSs can also stimulate signal transduction pathways and activate key transcription factors - with altered gene expression can lead to carcinogenesis.
What are skip metastases?
Infiltration by the tumour of distant nodes, but without tumour involvement in the nodes adjacent to it.
What percentage of disseminated cancer cells successfully develop into a distant met?
<0.1%
Why can mets develop some time after the initial cancer?
Cells (micromets) can remain undetectable (in cell cycle or due to a balance between proliferation and apoptosis) before eventually developing into a detectable macro met.
Cancer cells can move individually or collectively - what is this facilitated by??
A change in cell plasticity - esp from epithelial to mesenchyme transition (EMT)
Which cytokine stimulates epithelial to mesenchymal transition and plays an important role in tumourigenesis?
TGF-β
(Transforming Growth Factor β)
Which cytokine stimulates tumour angiogenesis?
VGEF
Vascular Endothelial Growth Factors
What are immunohistochemical tests used for in cancer diagnosis?
Diagnosing the cancer type including subtypes - allows a prediction of response to therapy and helps guide treatment options.
What is the difference between TX (or NX or MX) and T0 (or N0 or M0)
X = cannot be measure
0 = not found
What is the grading of stages of T, N and M
T 0 - 4
N 0 - 3
M 0 - 1