Biomedical Engineering Reference
In-Depth Information
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Figure 1.4
Heterogeneity in vascular permeability. Tumor heterogeneity affects the
vessel density and permeability that EPR is dependent on. Among others,
extravasation varies with (a) location inside tumor, (b) cell type, and (c)
location of the tumor in the body. (A) Image of extravasated liposomes
showing permeability varies with location inside the tumor (Reproduced
from Yuan et al.
32
with permission from the American Association for
Cancer Research). (B) Vascular permeability also varies with different cell
lines or hosts (Adapted from Yuan et al.
69
with permission from the
American Association for Cancer Research). (c) The same tumor line
(LS174T) was grown in two different sites and resulted in differences in
vessel density and permeability; *P , 0.05 when compared against values
for skin group (Reproduced from Fukumura et al.
70
with permission
from Elsevier).
unique challenge in cancer therapy. They contribute to pro-survival signaling
pathways, are able to differentiate into other cells, and are more tumorigenic
when injected into a new host—which may imply metastatic potential.
91-93
Cancer stem-like cells seem always to be present and in equilibrium with other
cancer cells.
94
While the source of these cells is debated (they may come from a
mutated stem cell or a normal cancer cell mutates to become stem cell-like), the
fact
remains
that
they
have
characteristics
that
make
them
capable
of
resistance and renewal.
95,96
Efforts to categorize and target cancer stem cells
