Page 305 - 20dynamics of cancer

290 CHAPTER 14

(a) (b)

Clonal succession

Time

Clonal succession

Stem cell lineages in compartment

Figure 14.1 Stem cell lineage history in a tissue compartment. (a) All stem cells
division occur asymmetrically, maintaining each independent stem cell lineage.
(b) Rare symmetric stem cell divisions lead to occasional loss of a stem cell
lineage and replacement by another resident lineage. Over time, chance events
cause loss of all lineages but one, leading to a sequence of clonal successions.

Yatabe et al. (2001) asked: Does a colon crypt maintain distinct stem
cell lineages over time, or does a crypt proceed through a sequence
of stem lineage replacements such that only one lineage survives over
time? Figure 14.1 contrasts these alternatives. If stem cells always di-
vide asymmetrically, then each stem cell division always produces one
daughter stem cell to continue the lineage: the crypt maintains several
distinct stem cell lineages. Alternatively, if occasionally a stem lineage
failed to produce a daughter stem cell, that loss may be compensated