18 - Cancer

Question 1

Cancer

Answer 1

Cancer is Deregulation

Uncontrolled growth can arise from upsetting the balance between the activity of gene products that promote cell cycling vs. those products that supress cell cycling.

Question 2

four most common types of cancer in Canada

Answer 2

1. Breast cancer
2. Prostate cancer
3. Lung cancer
4. Colon cancer

Question 3

likely factors contributing to cancer incidence in Canada

Answer 3

• Men are at a higher risk of getting cancer
• 40% of women and 45% of men will develop cancer
• 25% of Canadians can expect to die of cancer
• Rates among youth are rising
• The heritability of cancer depends on the types of cancer, but it is 0.27 - 0.42

Question 4

Role of cyclin/CDK complexes in cell cycle regulation

Answer 4

• G1 check point prevents cells from replicating DNA
• It is monitored by the complex CDK (cyclin dependent kinase)
• CDKs are prtein kinases, enzymes that add phosphate groups to target proteins
• Switch on only when combined with another protein called a cyclin, they are called this way because its concentration rises and falls during the cell cycle
• it is produced early in the cycle and binds to CDK, then phosphorylated target proteins and releases the G1 checkpoint
• post translational regulation, another set is used to get through the next checkpoint (S)

Question 5

role of proto-oncogenes, tumor suppressor genes and oncomirs in caner

Answer 5

• Cells need to be responsive to the environment, with EGFR (epidermal growth factor receptor) protein, when there is this factor it binds to receptor there is this internal signaling machine in cell
• It is an embryo gene (oncogenes)
• With tumors the EGFR is always on so there is a lot of division, when it is deregulated and is on too much
• When the receptor is inactive and working properly it is called proto-oncogenes, when they get deregulated they are called oncogenes, there are many kinds of oncogenes
• It is a huge network and really complex
• There are so many ways to mess up regulation
• Oncomirs - cancer causing miRNA, miRNA are the ones that are diagnostic. miRNA are over expressed in tumors

Question 6

role of p53 gene

Answer 6

• Involved in shutting down rapid cell division during embryo geneticists, embryo suppressors
• Increased DNA repair
• Cell cycle arrest by blocking cyclin/CDK
• Apoptosis
• If they are mutated they will stop, stopping cell division, which will make tumors

Question 7

explanation for why increased cancer risk can be inherited

Answer 7

• BRCA 1 is a breast cancer tumor suppressor gene. Its function is to put the bricks in cell division
• You might have inherited normal alleles of the gene, throughout the course of your life you might have had mutations to both alleles of this gene and now you have lost the tumor suppressor function of that gene. This means that the cells can now divide out of control.
• If you inherited from your dad the mutated allele, then you only have the good working allele from your mom. This means you are at a higher risk of being homozygous for the mutant allele and developing a tumor on a tissue. Also you need one mutation instead of 2.

Question 8

explanation for why cancer incidence tends to increase with age

Answer 8

• Most mutations require several changes at a time to actually develop into a nasty tumor
• It takes time for this
• Incidence are high because it occurs more in old people

Question 9

role of stem cells in tumor growth

Answer 9

• Probably all tissues have pluipotent stem cells
• When they divide to make two daughter cells, one continues being a stem cell and the other one is a progenitor, which goes on and differentiates into something, the stem cell divides again and makes another progenitor cell and stem cell.
• Stem, progenitor, and differentiated cells can all suffer mutations, and become cancer stem cells
• You have to get the cancer stem cell in order to get the tumor
• Mouse: Tumor cell nuclei can be re-programmed
  
  • The nucleus of a mouse egg is removed and it is replace with the nucleus of the tumor cell, it is then given an electric shock and starts to divide with a nucleus tumor cell, which makes a mouse not a tumor, it is reprogrammed

Question 10

evidence that epigenetic regulation may be relevant in cancer

Answer 10

• Mouse: Tumor cell nuclei can be re-programmed
  
  • The nucleus of a mouse egg is removed and it is replace with the nucleus of the tumor cell, it is then given an electric shock and starts to divide with a nucleus tumor cell, which makes a mouse not a tumor, it is reprogrammed
• Maybe this egg cell is epigenetically reprogramming this nucleus
• Cancer is epigenetic which can be reversible, but then maybe mutations happen that can be less reversible