10. Cell cycle and cancer Flashcards
What is endoderm? What are pancreas progenitors?
Endoderm prefers to primitive tissue from which the pancreas develops. Pancreas progenitors are the cells that will differentiate to become alpha cells (glucagon secreting cells) and beta cells (insulin secreting cells)
What is directed differentiation?
Directed differentiation refers to protocols that provide mixtures of growth factors, cytokines and other molecules to activate or inhibit particular developmental pathways to direct the differentiation of primitive cells to particular desired cells.
Where does the cell cycle end?
In mitosis - cell divides
The rest of the time is spent in interphase (G1, G2)
What are telomeres?
Found at tip of chromosomes, is the repeat of a TEL nucleobase sequence.
Less telomeres mean less cell division possible
What are growth factors?
- There are mitogens (Proteins, hormones, signals, etc)
- Tells cells to produce transcription factors for cells to divide
Fun fact: Cancer cells produce their own growth factors
What is CdK and Cyclin complex?
CdK (cyclin dependent kinase) adds phosphate
CdK is activated by binding to cyclin
The cyclin-Cdk complex acts as a protein kinase (adds a phosphate to a substrate) and triggers transition from one stage to next.
What is the restriction point? What role does RB play?
The restriction point is a decision point past which the rest of the cycle must continue.
Progress past the restriction point depends on retinoblastoma (RB) protein aka tumor suppressors.
Normally RB blocks the cell cycle
Phosphorylated RB is inactive it no longer blocks restriction point
What are two ways cells die?
- Necrosis - death due to external event (ex: starvation)
2. Apoptosis - programmed cell death (ex: remove unnecessary cells, remove genetically damaged cells)
What is cancer, what causes it?
- Cancer is a result of inappropriate cell division (cyclin-CdK controls are disrupted)
- proto-oncogenes become oncogenes (excessively active)
- tumor supressor genes become inactive
ex:
- Over half of human cancer cells have defective p53. Protein p53 stimulates synthesis of p21 which inhibits CdK and prevents normal cells from dividing
ex: Carcinoma – epithelial cell tumours
Sarcoma – mesoderm (muscle, connective tissue)
What are some functions of oncogenes?
- Code for growth factors
- Code for growth factor receptors
- Code for transcription factors that can activate genes involved in cell division
- Code for proteins that participate in the transduction of signals for cell division
What are some tumor supressor gene functions?
- Code for cell adhesion proteins
- Code for enzymes involved in DNA repair
- Code for proteins that stop the cell cycle at end G1
How does cancer treatment work?
- Some drugs block M phase, inhibit growth factor stimulation at restriction point, block DNA replication, radiation damages DNA and causes apoptosis at the S and G2 checkpoints
What can stem cells do?
They can self-renew and also differentiate
What’s the difference between totipotent, pluripotent and Multipotent?
Totipotent: fertilized egg
progenitors
Pluripotent: embryonic stem cells
Multipotent: can go into different tissue/functions
What are two ways to obtain pluripotent stem cells?
- Embryonic stem cells
2. Induced pluripotent stem cells (from skin cells)
What is Flow cytometry used for?
To identify and separate cells by cell size and granularity
Explain this graph and what the quadrants mean?
Each dot is a different cell.
38% of cells have high of NKX6-1 expression and C-peptide expression (these are markers)
How are transcription factors induced?
- A cell produces an inducer protein that will bind to receptors on nearby cells
- inducer binding results in transcription factor activation
Explain french flag model.
There is a higher transcription factor concentration produced near a signal source, and so cells spaced further away will develop differently.
–> Gradient signalling
Ex: Hand
