|
Tumors require an extensive network of
blood vessels to supply the nutrients for its excessive cell growth.
Thus, the tumor calls on many of the body mechanisms to acquire those
needed blood vessels. If the tumor can be denied this continuing supply
of new blood vessels, tumor growth will be inhibited or halted.
Treatment to block angiogenesis is properly termed antiangiogenesis
(AA). It must be emphasized that antiangiogenesis will most likely not
“cure” cancer. It will slow or halt growth, which in turn will allow
more time and opportunity for other cancer treatments to become
effective. Endothelial
cells line blood vessels, The tumor produces angiogenic substances to
initiate endothelial cell growth, which in turn initiates capillary
growth. These substances may be growth factors particularly VEGF-
vascular endothelial growth factor, proteases, oncogenes, signal
transduction
enzymes, cytokines, endogenous modulators,
etc.
Many natural and alternative medicines are
proposed to have AA activity, which may explain in part, why they show
anticancer activity. The mechanisms of activity remain to be elucidated.
Some of the products claimed to have AA activity are: alpha lipoic acid,
bindweed, butcher’s broom, curcumin, genistein, green tea, honeylocust
fruit, quercetin, selenium, shark cartilage, and silimarin.
There are two general approaches to
antiangiogenetic therapy. One is to block these growth factors; there
are several such blocking agents, such as Avastin, being developed by
various drug companies. They are in clinical trial and show promise, and
also promise to be expensive if and when available. Further, as with
many new drugs, adverse effects are being found, which may not outweigh
their potential in cancer therapy. These drugs are currently for
clinical trial only, and access requires participation in such trials.
A second approach is to deny a tumor the
one component absolutely required for blood vessel growth - copper.
Tumors hoard copper containing about three times the normal tissue
levels of this mineral. Normal tissue function remains intact when the
copper levels are only lowered but a tumor’s abnormal needs are denied.
Unlike the first approach , there is already a drug available. An agent
with orphan drug status for the treatment of Wilson’s disease is
available and works by decreasing body copper levels. Tetrathiomolybdate
(TM) selectively chelates copper and has been safely used for many years
in the treatment of Wilson’s disease. Initial studies indicate that it
can decrease cancer cell growth. There are at least nine clinical trials
of TM in progress, and these trials will attempt to prove activity in
several cancer types.
Tetrathiomolybdate treatment requires a
month or more to reduce copper levels; then the patient must be
maintained at this low copper level for several months. As with all
cancer treatment, the sooner treatment starts the more likely there will
be success. The treatment procedure is rigorous with regard to dosage
timing, diet, and other restrictions. This is not a treatment to be
individually undertaken. We cannot over stress the absolute need for
patients using TM therapy to be in the care of a physician and be
continually monitored for the duration of the treatment. Drug
adjustments will likely be required over time to maintain the desired
effect. As adjuvants to TM treatment, both vitamin C and zinc,if taken
with meals, will decrease copper uptake.
We feel that TM will become a major
component of successful cancer therapy in both conventional and
alternative medicine. However, we also feel that TM’s potential will
only be realized when TM is rationally combined with other modalities,
both while copper levels are being lowered, and later when the low
copper level is being maintained. Time is never on the side of the
cancer patient. If cancer growth can be slowed or halted, this offers
more time as well as opportunity for other therapies to actually kill
the cancer. We feel that immune therapy will be greatly improved when
combined with antiangiogenesis. It is also likely that some alternative
treatments will show sufficient activity under these conditions to
demand they be recognized.
Natural Killer Cells and Cellular Immunobiology
Proponents of immune
treatments for cancer have long anticipated the increased use of
cellular immune therapy. The ability to use cellular immune components
to directly attack the cancer cell is what immune therapy is about.
The current treatments indirectly approach this by correcting immune
imbalance and stimulating the immune system to produce those cellular
components which attack cancer, such as T-cells, macrophages, etc.
Actually giving the patient T-cells from an outside source is a major
goal of emerging immune therapy.
This concept is not new.
It has had to await refinements and control which is now becoming
possible. In the 1980s Rosenberg did pioneer studies with lymphocytes,
removing them from patients, activating them and returning them to the
patients, the so-called LAK cell (Lymphocyte Activated Killer cell).
It is a useful treatment, though sometimes unreliable and ineffective.
Newer refinements have greatly improved the treatment since Rosenberg,
but it still does not give the degree of activity that we expect from
immune therapy.
Dendritic cells are another
approach which has shown some success, but not to the degree we know
should be possible. Dendritic cells recognize cancer cells and take that
information to the immune system stimulating the production of tumor
specific T-cells (cytotoxic T-cells), which in turn attack the cancer
cells. Dendritic cells can be cultured from the patient’s blood, grown
in tissue culture and activated with cancer antigens. When they are
then reintroduced into the patient they can elicit an augmented immune
response to the cancer. Dendritic cells from tissue culture do not
produce as robust a response as native cells, indicating an area for
improvement. Dendritic cells are also proving to be major adjuvants in
cancer vaccine research.
Natural killer cells (NK
cells) are a type of cytotoxic T-cell that are not specific for one
cancer cell type, as are the tumor specific cells produced in response
to dendritic cells. Originally NK cells were thought to simply attack
cancer cells when they find them and not require activation by finding a
specific cancer cell marker, hence the name natural killer cells. We now
know that they are activated by lack of a cell marker that identifies
the cell as “self” that is normal to the body. They are also activated
by interleukin-2 and recent research has identified other activating
factors. NK cell are considered to be an initial line of defense while
the immune system makes tumor specific T-cells. However, due to the
intensity of NK cell attack, they are receiving interest as the most
promising of immune cell therapies. NK cells grown in tissue culture do
not exhibit the decreased activity as tissue culture dendritic cells.
Some research groups claim to have methods of further activating NK
cells before reintroducing them into patients.
Recent reports of complete
remissions of some cancers with NK cells has fueled the public’s
interest in NK cells and generated over optimism for the treatment. Will
all patients receiving NK cell therapy have a complete remission? Not in
the near future. Will NK cell therapy become a major breakthrough in
cancer? We believe this to be the case.
At
present both dendritic and NK cell therapy offers promise, with NK cell
currently having some advantage. Here at the Immune Recovery Centers of
America we believe that a combined approach with both cellular therapies
merits consideration. As the IRCs have found with other immune
therapies, combined therapies in the proper sequence can improve
response. We also believe that immune reconstitution before NK or
dendritic cell therapy will enhance the ability of the immune system to
maintain the NK and/or dendritic cell effect. Unfortunately such
treatments in the US are classified as “clinical research” leaving
patients with little option other than to go offshore. The Immune
Recovery Centers maintain contact with groups researching cellular
immunotherapy, and is developing strategic alliances with several
laboratories to allow our patients access to such therapies. Because
cellular immunotherapy offers such promise for cancer patients and is an
intense area of research, we feel that treatment standards will develop
which will allow more routine use in the US.
|