Page 271 - 20dynamics of cancer

256 CHAPTER 12

Bone Marrow Blood

Pro-T
T cells
CLP Dendritic cells
Self-renewal capacity
NK cells
Pro-B
B cells
LT-HSC ST-HSC MPP

GMP
Granulocytes
Monocytes
CMP Dendritic cells

MEP
Erythrocytes
Platelets

Figure 12.3 The transit lineage of hematopoietic differentiation in adult mice.
Long-term hematopoietic stem cells (LT-HSC) renew throughout life. Short-term
hematopoietic stem cells (ST-HSC) self-renew over a 6–8 week period. Multipo-
tential progenitor (MPP) cells self-renew for less than two weeks, differentiating
into common lymphoid progenitors (CLP) and common myeloid progenitors
(CMP). Those progenitors then differentiate into another layer of precursors,
which then differentiate into the final cell types of the blood. Redrawn from
Kondo et al. (2003) and Shizuru et al. (2005).

2003). Figure 12.3 shows the differentiation hierarchy. Only the long-
term (basal) stem cell lineage survives over time. The other cell lineages
divide a limited number of times, differentiate, and die, to be replaced
by new daughter cells derived from the basal stem lineage. I could not
find any clear statement about the typical number of cell divisions from
the basal lineage to extinction of a transit lineage.
The long-term stem cells of young mice appear to divide roughly every
10–20 days. No evidence suggests different rates of division between
stem cells (Bradford et al. 1997; Cheshier et al. 1999).

GASTROINTESTINAL RENEWAL
Studies of mice and humans show that the epithelial surface of the
intestine sloughs off continually and is renewed by fresh cells (Bach et al.