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In the earlier lecture,
I described the fact
that one can describe
the hierarchical
organization of cells
within a carcinoma
in terms of self-renewing,
tumor-initiating
cancer stem cells,
indicated here in this
first slide with the blue cells,
which are self-renewing
stem-like cells.
And the bulk of cells in a tumor
indicated here in the gray
and the red,
which differ from one another
in that the gray and red cells
have undergone
a measure of differentiation
which takes them out
of the stem-like state
and places them in a state
where they no longer
have stem-like properties
and they no longer,
therefore, have the ability
to serve
as tumor-initiating cells.
I argued in the earlier lecture
that, in fact,
cells that have lost
this tumor initiating ability
are poor candidates
for serving as the founders
of new metastatic colonies,
because they no longer have this
tumor initiating capability.
Still, this diagram,
as pleasing as it might be,
required some
critical examination.
Among other questions
was the following one.
Given the fact
that the blue stem-like cells
can differentiate
into gray cells,
is this process,
of an arrow leading straight
down from the stem-like cells,
to the non-stem cells,
irreversible?
Or are there more complexities
that operate
in governing the interactions
and the interconversions
between, for example,
the gray cells
and the blue cells?
And this caused
Christine Chaffer
to begin to examine what happens
when one, for example,
isolates
the non stem-like cells,
transit-amplifying cells,
as they're depicted here.
What happens
when one places them
in culture
or in a living animal?
How do they behave
thereafter?
And her evidence
began to accumulate
that the diagram
that I show you here
needs to be revised.
