Chapter 5: 5.11 Molecular Basis for Cancer Flashcards
Cancer arises when…
Cells grow or divide out of control
What causes cancer?
Mutations in many different types of genes
Cancer is caused by mutations in genes that control…
- Cell growth
- Cell division
- Apoptosis
- DNA repair
- Growth at foreign sites
Describe:
Cell growth genes in cancer
Signals that tell the cell to stop growing are mutated
* Thus, once cells grow to a certain size, they divide
Describe:
Cell division genes in cancer
Signals that tell the cell to stop dividing are mutated
Describe:
Apoptosis genes in cancer
Signals that control cell death are mutated
* Allols an abnormal cell to evade death (immortalized)
Describe:
DNA repair genes in cancer
Mutations can arise more eaily in genetically unstable cells
When does metastic cancer occur?
Cells from the primary tumor move to another part of the body and begin to grow there
Define:
Benign cancer
Contained at the originating tissue
Define:
Malignant cancer
Spreads to other tissues
True or False:
Cancer can be inherited
True
List:
DNA damaging agents
- UV
- Chemical agents
- Radiation etc.
The more mutations that accumulate, the more likely a cell it to become…
Cancerous
True or False:
One mutation is usually enough to cause cancer
Usually not
Why does cancer risk increases with age?
Due to accumulating mutations
Define:
Proto-oncogenes
Genes that are likely to lead to cancer if mutated
Once mutated, genes correlated to cancer fall into what categories?
- Oncogenes: ACCELERATE cancer growth
- Tumor suppressors: STOP cancer growth
Give examples of:
Oncogenes
- Ras: Gene involved in cell signalling (controls cell growth, differentiation, and survival)
- Myc expression: Leads to cell proliferation
Give examples of:
Tumor suppressors
- p53: Protects genomic stability and prevents mutations
- BRCA1: Repairs DNA damage
What can mutations in Ras result in?
Disruption of signals controlling cell growth, differentiation, and survival
What can mutations in Myc expression lead to?
Over-expression results in cells proliferating out of control
What can mutations in p53 lead to?
Loss of function, means other cancer-causing mutations are likely to arise
What can BRCA1 mutations lead to?
Increase the risk of breast and ovarian cancer
What types of mutations result in cancer?
- Mutations in protein coding sequence
- Gene amplification
- Chromosomal rearrangement
Describe:
Mutations in protein coding sequence in cancer
Results in hyperactive protein
Describe:
Gene amplification in cancer
Results in too many copies of a gene which is translated into too much protein
Describe:
Chromosomal rearrangement in cancer
A gene is placed under the control of the wrong transcription factors or is fused to an actively transcribed gene
In the 1920s, what did Otto Warbug observe?
- Cancer cells use A LOT of glucose compared to the surrounding, non-cancerous tissue cells
- Cancer cells survived in the absence of oxygen as well
Define:
Aerobic glycolysis
The glucose is metabolized into lactate even in the presence of oxygen
Normal cells convert glycose into ATP via what two mechanisms?
- Oxidative phosphorylation: In the PRESENCE of oxygen, 1 glucose = 36 ATP
- Anaerobic respiration: In the ABSENCE of oxygen, 1 glucose = 2 ATP
What is the “Warburg Effect”?
The speculation why cancer cells use a LESS efficient way of generating energy even in the presence of oxygen
What are some speculated answers to the “Warburg Effect”?
- Perhaps the cancer cells need other by-products obtained from anaerobic respiration
- Perhaps cancer cells use anaerobic respiration because it is much faster than oxidative phosphorylation
- Perhaps the mitochondria is damaged and the cancer cells CANNOT use oxidative phosphorylation
- Ongoing research…
