is a complex place dealing with internal and external signals that
control what they do and when they do it. Dividing cells divide
when they need to and then settle down and do their job. They
respond to chemicals released by neighboring cells, or chemicals in
the tissue fluid, or chemicals carried in from the blood. Damaged
cells have ways of checking their damage levels and refusing to
divide. Often, damaged cells activate a process called apoptosis,
during which they purposely kill themselves.
cancer, cells divide that shouldn’t, and they keep dividing. It may
be that the interplay that switches from “division” to “do your job”
malfunctions. Maybe the response process to begin a division goes
bad. Maybe a damaged cell does not kill itself, giving rise to more
damaged cells. Maybe the system that checks for damage is itself
damaged. These and many other problems can be the initial trigger
for a change to cancer.
early cancer cells try to do their jobs, but they are not very good
at it. The cells that don’t try a shift in cell chemistry, that
just plow on to another division, are doing a simpler process and
are probably more likely to survive. Over time, a tumor often loses
distinctions that identify the tissue it started as. The cells
start to look like early embryo cells, another population that is
purely in the business of making more cells. A tumor grows, using
body resources but giving nothing back.
is evidence that the immune system may be cued to recognize and
destroy cells that have become cancerous. Cells that retain the
cellular markers that the immune system recognizes get destroyed.
If a cancer cell does not express those markers, it doesn’t use
those genes, the immune system leaves it alone. That is an early
evolutionary step for a “successful” cancer.
in the mass that are the most efficient dividers are the most likely
to dominate in a growing tumor; genes that aid in division are
likely to be activated. Telomerase, an enzyme that helps in the
production of new chromosomes leading into a division, often is
produced more in these cells. As we age, lack of telomerase has
been associated with inability to divide cells to repair damage.
Anti-aging treatments that boost telomerase may help early-stage
cancers to get going.
tumor grows, the cells on the inside of the mass get isolated from
passing blood vessels. In some tumors, cells activate a gene for a
signaling molecule that causes blood vessels to grow into the
tumor; this molecule is useful during our growth phases, but as
adults we stop using it. One class of cancer drugs counteracts this
signal. However, in some tumors, the ability to survive low-oxygen,
low-nutrient conditions, features found in muscles and skin,
activates. Cells that can’t survive the conditions die.
Radiation can be aimed at local tumors. Radiation is absorbed by
DNA, shaking and breaking it. The broken DNA is often misrepaired,
strengthening the signal to resist new divisions, and when divisions
do happen, distribution of loose pieces may cause the death of the
daughter cells when they activate genes on extra or missing pieces.
Radiation at this strength also can very badly affect our normal
cells; multiple lower-strength beams are aimed to overlap at the
tumor location and have lesser effects on the cells hit on the way
in and out. Radiation is not an option for cancer that has spread
through the body.
Chemotherapy has effects mostly on the chemistry active in dividing
cells. The side effects come from how it works on our normal,
dividing cells, like those lining our digestive systems or hair
follicles. Is it possible for the molecular target in one or more
cancer cells to be unaffected? Yes, which means that unaffected
cell or cells will survive and give rise to a chemotherapy-resistant
some of the tumor cells, genes are activated that would normally be
in use in white blood cells or some repair cells, giving those cells
the ability to detach from the mass and crawl away. This is the
shift to malignancy or metastasis, probably the most dangerous
change that can happen. Loose cells move away from the original
site. Inside spaces such as an abdominal cavity, they might float
about the space and settle elsewhere; in many places, they spread
the same way that white blood cells do, moving into the lymph
drainage system as a way into the blood circulation. That creates
spreading patterns for various malignant cancers.
Spreading cancer cells settle in other sites and divide, forming new
tumors. These tumors sap the body’s resources more and more,
depleting other tissues. Do they mobilize nutrients from other
tissues from afar, the way that fetuses can commandeer nutrients
from the mother? Do nutrition-based treatments bolster the body’s
ability to resist these effects? In any case, eventually either the
treatments manage to destroy most or all of the cancer cells or the
cancer outcompetes critical body systems, starving them.