Carcinogenic
(cancer) process:
At the beginning, a
change in a target
cell, tissue
or organ
is necessary to initiate
the carcinogenic process.
This change induced
by exposure
to a carcinogen
is called 'initiation'.
Initiation is not necessarily
sufficient to develop
cancer.
A second step, called
'promotion' has
to arise. Promotion
itself is not sufficient
either and is the process
whereby an initiated
cell, tissue or organ
develops focal proliferation.
[UV radiation, for instance, is both an initiator and a promoter of skin cancers, which means it is a complete carcinogen]
The carcinogenic process
can be modulated positively
or negatively. The positive
modulation speeds up
the process, shortens
the latency period between
initiation and cancer
development, increases
the intensity or changes
the nature of the cancer.
The negative modulation
slows the process down,
prolongs the latency,
decreases the intensity
and changes the nature
of the cancer. This
negative modulation
can be considered as
cancer prevention. To
prevent cancers the
factors capable of modifying
the effect of initiation
or promotion or acting
as modulators have to
be known. |