Biomedical Engineering Reference
In-Depth Information
tumors exhibit high death rates supports this contention (23). Most of the cells in
a tumor die because they are incapable of forming strategies that allow them to
survive in their current environment.
4.7. Complex Adaptive Systems Change How Strongly They
Interact with Others in a Way that Maximizes the Average
Fitness of the System
Tagging can, and does, occur at multiple levels within any system. At the
level of the biocircuit within the cell, a tag can represent a phosphorylated or
ubiquinated protein which signals that it should be recycled. At the level of the
immune system, tagging can represent an antigen on a cell surface that allows
white blood cells to recognize it as "self." Metastasis of a tumor can be taken as
proof that the cells comprising that tumor have altered their interactions and
connections not only with adjacent tumor cells, but also with the cells that form
the lining of blood vessels. Metastasis requires active interactions between the
cancer cells themselves and their environment. For cancer cells to enter the
bloodstream, their connection with other cancer cells must be weakened. In the
bloodstream, cancer cells bind to each other as well as platelets to survive the
ambient turbulence. To escape the bloodstream, the cancer cells must then suc-
cessfully bind to the endothelial cells of the target organ (30,37). All of these
actions occur by altering the expression of cell-cell adhesion molecules in a
dynamic fashion.
4.8. Tumor Cell Heterogeneity Provides Growth Advantages
that May Appear to Be "Anticipatory"
The word "anticipatory" carries the connotation that a complex adaptive
system is conscious of its actions. On the contrary, the strength of modeling
through a complex adaptive system is that it needs no conscious thought process
to form complicated, rule-based systems. The culmination of genetic instability
and tumor cell heterogeneity is the acquisition of mutations requisite for a robust
and lethal cancer. Cancer can do this because it can recapitulate evolution at a
rate almost beyond comprehension.
5.
CONCLUSION
:
APPLYING COMPLEXITY THEORY
TOWARD A CURE FOR CANCER
The ultimate question is whether understanding cancer in terms of evolution
and complexity theory can help us cure the disease. "Cancer" is a complicated
