116A WEEK 11 – Cell Proliferation and Neoplasia
Learning outcomes
1. Describe the various reactive cell changes and how tissue
homeostasis is achieved
2. Describe the common principles of cancers
3. Detail each of the six hallmarks of cancer
4. Outline some of the main factors causing cancer
We are studying cancer (dysfunction) in order to study function, not
dysfunction
What signals do stem cells in the skin receive?
- Skin stem cells sitting in a basal lamina in the epidermis
- Receives signals that keep them in a balance between proliferating
more or proliferating less (not overproducing skin but also
replenishing it)
- Most skin cells in our body live on the basal lamina – by being
attached to it, it reinforces the cell’s status as a stem cell (the cell
knows where its attached and therefore its role). When the cell
leaves the basal lamina, it knows it’s not a stem cell anymore and it
knows to differentiate
- Only immune cells are able to roam around the body – special
status. If other cells started to roam the body, it is a cancerous
nature
Endogenous signals Exogenous signals
(internal signals) (outside signals)
Small chemical Hormones i.e. insulin
or serotonin
Environmental Internal pH, oxygen Temperature signal,
levels in cells light intensity etc
Physical The signal that cells
get from their
neighbours
, Cellular
Extracellular matrix
- Cancer cells can only control endogenous signals, which allows them
to override the exogenous signals
- Cancer cells produce their own hormones (autochromes)
- Cancerous cells revert to a more stem cell-like nature
- Stem cells are more able to become cancer than normal cells as
they are exposed to different factors i.e. DNA damage
- Stem cells have more replicative potential. If these cells are
damaged, they could start the process of development to cancer
What might make these cells change their proliferation?
- Why would the cells on the left proliferate, compared
to the cells on the right?
- The cells on the right may be detecting that the petri
dish is full and that they have many neighbours
- Cells on left have anchorage dependence, cells on the right have
density-dependent inhibition and age
Hayflick limit
-
Most living cells reach a phase where they stop proliferating and have a
limit of replication potential of around 40-50 times, discovered by
Hayflick. This prevents cancer as cancerous cells override this limit
- Barriers are formed
- Anchorage dependence and anchoring is protection against cancer
- Telomeres are important in replenishment/rejuvenation of cell life –
cancer cells replenish their telomeres which allows for proliferation.
Telomere replenishment is rare in other body cells, only happens in
things like gametes and in early life
What could we do to encourage the
cells to proliferate even faster?
- By changing the temperature in
the dish
, - By providing exogenous growth factors (e.g. PDGF)
- It is not enough to just put human cells in a petri dish and allow
them to grow – they need a lot of other specific factors (they do not
proliferate and replicate easily)
- Cancer cell lines are used to study things in cells as normal body
cells do not grow outside of the body easily – culturing ordinary
body cells, e.g. heart cells, is very difficult
How can tissues react to change?
- Hyperplasia
- Hypertrophy
- Atrophy
- Metaplasia
- Anaplasia
Hyperplasia
- Hyperplasia is the increased production of
cells, primarily caused by the increased
proliferation (cell growth/rapid increase in
mass) of precursor (stem) cells
- Hyperplasia can be healthy or pathological
- Example: more red blood cells being made
after blood bank deposit/loss of a pint of
blood
- The swelling of the goitre to produce more thyroid tissue is a healthy
thing but it can get out of control
Hypertrophy
- The increase in tissue size without
increased cell number
- Common in muscles as mature muscle
fibres don’t undergo cell replication
- Also, can be healthy or pathological
- Example: muscles growing larger
- Can also be due to swelling
Atrophy
- Describes the reduced presence of cells and/or reduced size of cells
– often both
- Can be healthy and pathological
- Example: old, aged people with decreasing
muscle mass
Metaplasia
- The cellular change from one cell type to
another
- Can be healthy or pathological
- E.g. tissue specialisation
Anaplasia
Learning outcomes
1. Describe the various reactive cell changes and how tissue
homeostasis is achieved
2. Describe the common principles of cancers
3. Detail each of the six hallmarks of cancer
4. Outline some of the main factors causing cancer
We are studying cancer (dysfunction) in order to study function, not
dysfunction
What signals do stem cells in the skin receive?
- Skin stem cells sitting in a basal lamina in the epidermis
- Receives signals that keep them in a balance between proliferating
more or proliferating less (not overproducing skin but also
replenishing it)
- Most skin cells in our body live on the basal lamina – by being
attached to it, it reinforces the cell’s status as a stem cell (the cell
knows where its attached and therefore its role). When the cell
leaves the basal lamina, it knows it’s not a stem cell anymore and it
knows to differentiate
- Only immune cells are able to roam around the body – special
status. If other cells started to roam the body, it is a cancerous
nature
Endogenous signals Exogenous signals
(internal signals) (outside signals)
Small chemical Hormones i.e. insulin
or serotonin
Environmental Internal pH, oxygen Temperature signal,
levels in cells light intensity etc
Physical The signal that cells
get from their
neighbours
, Cellular
Extracellular matrix
- Cancer cells can only control endogenous signals, which allows them
to override the exogenous signals
- Cancer cells produce their own hormones (autochromes)
- Cancerous cells revert to a more stem cell-like nature
- Stem cells are more able to become cancer than normal cells as
they are exposed to different factors i.e. DNA damage
- Stem cells have more replicative potential. If these cells are
damaged, they could start the process of development to cancer
What might make these cells change their proliferation?
- Why would the cells on the left proliferate, compared
to the cells on the right?
- The cells on the right may be detecting that the petri
dish is full and that they have many neighbours
- Cells on left have anchorage dependence, cells on the right have
density-dependent inhibition and age
Hayflick limit
-
Most living cells reach a phase where they stop proliferating and have a
limit of replication potential of around 40-50 times, discovered by
Hayflick. This prevents cancer as cancerous cells override this limit
- Barriers are formed
- Anchorage dependence and anchoring is protection against cancer
- Telomeres are important in replenishment/rejuvenation of cell life –
cancer cells replenish their telomeres which allows for proliferation.
Telomere replenishment is rare in other body cells, only happens in
things like gametes and in early life
What could we do to encourage the
cells to proliferate even faster?
- By changing the temperature in
the dish
, - By providing exogenous growth factors (e.g. PDGF)
- It is not enough to just put human cells in a petri dish and allow
them to grow – they need a lot of other specific factors (they do not
proliferate and replicate easily)
- Cancer cell lines are used to study things in cells as normal body
cells do not grow outside of the body easily – culturing ordinary
body cells, e.g. heart cells, is very difficult
How can tissues react to change?
- Hyperplasia
- Hypertrophy
- Atrophy
- Metaplasia
- Anaplasia
Hyperplasia
- Hyperplasia is the increased production of
cells, primarily caused by the increased
proliferation (cell growth/rapid increase in
mass) of precursor (stem) cells
- Hyperplasia can be healthy or pathological
- Example: more red blood cells being made
after blood bank deposit/loss of a pint of
blood
- The swelling of the goitre to produce more thyroid tissue is a healthy
thing but it can get out of control
Hypertrophy
- The increase in tissue size without
increased cell number
- Common in muscles as mature muscle
fibres don’t undergo cell replication
- Also, can be healthy or pathological
- Example: muscles growing larger
- Can also be due to swelling
Atrophy
- Describes the reduced presence of cells and/or reduced size of cells
– often both
- Can be healthy and pathological
- Example: old, aged people with decreasing
muscle mass
Metaplasia
- The cellular change from one cell type to
another
- Can be healthy or pathological
- E.g. tissue specialisation
Anaplasia
