The cancer process Flashcards
What is cancer and how many result directly from genes?
Group of diseases characterised by uncontrolled cellular growth as a result of changes in genetic information of cells - 5-10% inherited
What genes are involved in tumour formation?
Oncogenes: Promote cell division (HER 2)
Tumour suppressor genes: Prevent cell division (p53)
What are the stages of the cell cycle?
Go- Resting phase
G1- Growth and preparation of chromosomes for replication
S- Synthesis phase - DNA is copied or replicated - enzymes unwound and complementary strand is replicated
G2 - Preparation of the cell for division
M - Mitosis - Formation of two daughter cells
What is senesnce and what is it determined by?
- The point at which normal cell division stops - typically occurs after 60-70 divisions
- Determined by telomeres - when telomeres are too short cell can no longer divide and it undergoes apoptosis
What do the checking mechanisms ensure during the cell cycle?
- DNA is full copied
- Resulting DNA is not damaged
- Sufficient growth factors available to support new cell growth
If checks fail - normal cells stop dividing until conditions are corrected (cancer cells ignore these signals)
What 3 genes are involved in keeping cells cancer free?
1) Mismatch repair genes - oversee DNA replication and repair mistakes during replication process
2) Apoptisus genes - ensure cells are programmed to die
3) Telomerase genes - Responsible for telling age of normal cells and thus monitoring the ageing process
What are the six hallmarks of cancer?
1) Growth signal autonomy - Don’t need signals to instruct to divide
2) Evasion of growth inhibitory signals - Mutations mean don’t respond to antigrowth
3) Evasion of apoptosis - more mutations develop as they avoid death
4) Invasion and metastasis - Tumour cells secrete enzymes which digest membranes encapsulating organs, thus invade adjacent tissue
5) Sustained angiogenesis - acquired ability to induce angiogenesis (nutrients)
6) Unlimited replication - maintain the length of their telomeres and can therefore replicate endlessly
What ways are cancer cells produced?
1) DNA damage by agents in environment such as radiation and substances (both synthetic and natural) in our food, water, air and workplace.
2) DNA is shut down (hypermethylated) inappropriately expressed (hypometherylated) rater than damaged
3) Abnormalities in the function of DNA can result in an over or under-expression of cell growth factors or their receptors
4) More rarely, a gene that is essential to long-term stability of DNA or to proper control of cell replication can be inherited in an abnormal form from one parent
Give a brief outline of knudson two hit hypothesis
- Mutations would have to occur twice, one gene could be inherited but the other allele would have to be damaged
- Retina Blastoma Gene (RB1) is one gene that causes retinoblastoma
What are the four steps to a cell becoming cancerous?
1) Initiation - Carcinogenic agent/substance
2) Promotion - Cancerous cells are stimulated to proliferate
3) Transformation - Change normal cells undergoes as it becomes malignant - low grade tumour becomes a high grade tumour
4) Progression - Development of malignant tumour locally and possibly will travel to other sites (metastasise)
What are the characteristics of normal vs. cancer cells
Normal cells: Mortal, Normal nucleus, Under control of apoptosis gene, Controlled cell division, Controlled cell growth, Contact inhibition
Cancer cells: Immortal, Larger nucleus, Unable to apoptose, Increased cell division rate, Loss of growth control, Loss of contact inhibition, Invasive and metastatic properties, Develop their own angiogenic support system
