Cancer, Stem Cells and Cancer Stem Cells Flashcards
What is a stem cell?
A cell which can self-renew and differentiate
What does totipotent mean?
can make everything
What does pluripotent mean?
Can make all somatic cells
What does multipotent mean?
can make many different cell types
What was bi-/tri- etc. potent mean?
can make 2/3 etc. cell types
What does unipotent mean?
Can only differentiate into one cell type
What is potency?
A cell characteristic, not a stem cell characteristic - every cell can differentiate, divide or stay as it is
What is the most potent (totipotent) cell?
A zygote
Describe embryonic stem cells
Cultured in vitro from cells of the early embryo
Pluripotent
Immortal
Describe adult stem cells
Exist in many tissues
Normally contribute the tissue maintenance
Numbers, properties and functions vary
Describe somatic stem cell characteristics
Rare Slow cell cycle Symmetric or asymmetric cell division Unspecialised Present in many adult tissues Usually respect germ layer boundaries
What is symmetric division?
Where they either make two new stem cells or two differentiated cells
What is asymmetric division?
They make one new stem cell and one differentiated cell
What is the most common type of division?
Asymmetric division (80%)
How have stem cells developed so they divide asymmetrically?
The stem cell will only be a stem cell if one cell self renews and stays anchored to the niche and one cell differentiates and leaves
OR
Feedback mechanisms, if you have too many differentiated cells it will send a strong negative feedback which inhibits the cell from dividing or differentiating. Or if there isn’t enough differentiated cells it will send a week negative signal
How do stem cells induce symmetrical division?
Through the feedback loops since sometimes you need more or less of something
What is a stem cell niche typically made up of?
A basement membrane for the stem cell to bind to
A bone for mechanical support
Blood vessels for nutrients
Specialised cell next to it which provides the signal
What happens during injury?
The negative feedback is removed, causes them to increase their divisions and does so in such a way that it expands itself so it produces progenitors -> increase the rate of new tissue production
What are progenitors?
Fast dividing cells
Transit amplifying cells
Why do stem cells not want to undergo too much division?
It is error prone so they are more likely to get a mutation and since these cells live forever you do not want a mutation in them
What is regeneration?
Homeostasis + Repair
How do cancer stem cells arise?
A stem cell can start to proliferate too much or there is a block in differentiation, causes a loss of mature cell types
OR
Progenitor cells will proliferate a lot and you will have a reduced mature cell compartment
Why is knowing the origin of the tumour important?
For those cancers which can’t be treated by surgery, targeting the origin is critical for long term cancer removal
What do testicular teratomas contain?
Derivatives of all germ layers
What are embryonal carcinoma cells?
Where you take the undifferentiated cell from the original tumour, this is the cancer stem cell, inject it into a new mouse and the new mouse gets the same cancer
What is a cancer stem cell?
A cancer cell with stem cell properties
Not always derived from a stem cell
Are differentiated tumour cells tumourigenic?
No
In acute myeloid leukaemia, what cell develops the cancer to become the cancer stem cell and how is it known?
Progenitor
Only the CD34+CD38- cells were able to develop new tumours
These are similar to haematopoietic stem cells but they were CD90+ when HSCs are CD90-, progenitor cells are CD90+
Why doesn’t chemotherapy cure cancer?
Cancer stem cells are slow proliferating and therefore the chemotherapy doesn’t target the origin
The cancer stem cells have efflux pumps and therefore the drug concentration in them are lower
How do stem cells save patients from chemotherapy?
Since they proliferate slowly, they aren’t targeted and restore the normal cells which have been
