Biology Reference
In-Depth Information
Another fundamental feature of embryogenesis is that, throughout its process,
there occur micro-meso correlations, because morphogenesis is ultimately
directed by the molecular sequence information encoded in DNA which is located
in the nucleus of individual cells. If this interpretation is right, it may be concluded
that embryos are physical systems at critical points at the micro-, meso-,
and macrolevels. In a sense, embryogenesis is a critical phenomenon, which
may be referred to as a
bio-critical
phenomenon in contrast to the purely
physical ones studied in condensed matter physics (Anderson 1972, Fisher 1998,
Domb 1996).
15.9 Carcinogenesis as Quorum Sensing Gone Awry
Normal cells show the phenomenon of
contact inhibition
: that is, normal cells stop
dividing when they make contact with adjacent cells. In contrast, cancer cells lose
this ability and continue dividing in the presence of neighboring cells, thereby
leading to piling up of cells on top of one another, a characteristic feature of tumor.
There appears to be the possibility that the same mechanism used by bacteria in
their quorum sensing activity may be involved in normal-to-cancer cell transfor-
mation. This idea is explained in Table
15.7
.
The key assumption underlying Table
15.7
is that the mechanisms of intercellu-
lar communication/cooperation observed in bacteria also operate in principle in
normal density-sensitive cell growth which requires cell-cell communication
through gap junctions (Evans and Martin 2002, Trosko 2007). When this cell-cell
communication is compromised (dynamically as compared to statically, as
explained below), carcinogenesis and angiogenesis may occur (Trosko 2007,
Luiza et al. 2007). It is assumed here that what passes through gap junctions
between adjacent cells is not just equilibrium structures (e.g., ions, ATP, etc.) but
dissipative structures
(or
dissipatons
), namely, the time-dependent patterns of
changes in the concentrations of equilibrium structures comparable to what is
referred to as RNA dissipatons (the patterns of distribution of RNA trajectories)
predict
that
it
is not
the differences in gap junctional structures alone that
Table 15.7 The hypothesis that carcinogenesis is a form of quorum sensing gone awry
Quorum sensing
Carcinogenesis
1. Signal
Autoinducers
Transcription signals (less than 1,000 Da)
2. Receptor
luxR
Gap junctions (connexons)
3. Gene expression
induced by
High levels of
autoinducers
detected by luxR
High levels of transcription signals accumulating
in cancer cells due to gap junction blockade
4. Intercellular
communication
Enhanced
Inhibited
5. Dissipative
structures
Concentration gradient
of autoinducers
Concentration gradient of transcription signals
(e.g., ions, ATP, NADH, etc.?)
