MCB Lecture 65 Neoplasia II Flashcards
Conventional cancer therapies are effective against …
The tumour cells, not the cancer stem cells or progenitors
Describe the paradigm of cancer
Normal cell -hit- Cancer stem cell -more hits- Progenitor cells Tumour
What is a ‘hit’?
This is genetic or epigenetic changes to the Cell
What is the effect on a cell of a ‘hit’?
Increased self renewal potential
What are the four genetic events that result in cancer?
- Activation of a proto oncogene
- Deactivation of a tumour suppressor gene
- Replication despite DNA damage
- Inhibition of apoptosis or senescence
Describe proto-oncogene activation causing cancer
Eg. KRAS
When a proto oncogene is activated, the cell undergoes increased proliferation
Why does mutation of KRAS result in cancer?
Constitutively active proliferation pathways such as MAPK
Describe mutation in tumour supressor genes resulting in cancer
Eg. APC or Rb
When APC is mutated, beta catenin is not marked for breakdown.
Beta catenin stabilises and switches on genes that result in proliferation
Which tumour suppressor genes mutate commonly to form cancer?
APC and Retinoblastoma
What does SNPs of APC cause?
Adenomatous polyposis
1000s of polyps in the small intestines
One polyp then may undergo malignant transformation, resulting in cancer
What is the function of APC?
It is an integral part of the beta catenin destruction complex
Describe replication causing genomic instability
Which gene in commonly involved?
p53
If DNA is replicated despite genomic instability, mutations in the cells are perputuated, possible resulting in cancer
Describe the function of p53 in healthy and cancerous cells
Healthy: When there is DNA damage, three things will occur: - try to repair the damage - G1 arrest - apoptosis
p53 mutation:
When there is DNA damage, p53 isn’t able to effect all these changes that would stop the perpetuation of the mutated DNA and mutation survives in the cell population
Homozygous loss of … is seen in almost every type of cancer
p53
Describe how inhibition of apoptosis or senescence results in cancer
Which genes are involved?
p53, Fas receptor, bcl-2, bcl-xL
If there is a mutation in any of these genes, apoptosis can not occur