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The journal article
summarizes various research regarding what is currently known about
natural killer cell function and then describes their important role in
cancer prevention and cancer removal. Written by the Department of
Immunology, Smith Kline & French Laboratories, Philadelphia, PA, this
information should be of special interest to parents of children with
brain cancer, neuroblastoma and
leukemia as
these cancers have been
found to be associated with defective natural killer cell function. The
following are direct quotes regarding major points from the article.
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"Moreover, the efficacy of
the different host defense mechanisms in destroying malignant cells
may depend upon the extent of tumor burden, immunogenicity and site of
tumore growth. For example, certain immune and nonimmune mechanisms
may prove effective in destroying circulating tumor cells even though
they might exert only a limited effect against the extravascular
primary neoplasm. This may be attributed to the observation that
unlike the cells within a solid tumor, tumor cells enter the
circulation as single cells or small clumps and are, therefore, highly
accessible and more vulnerable to destruction by immune and nonimmune
defense mechanisms." pg. 214
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Indeed, most tumor cells
that enter the circulation are destroyed during the first 24 hours and
only a few cells succeed to extravasate and develop into metastatic
foci in the organ parenchyma." pg. 214
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Also, the incidence of
spontaneous malignant lymphomas was reported to be increased in NK-deficient
mice carrying the beige mutation. In contrast, the relatively low
incidence of tumor development in athymic nude mice that exhibit high
Natural Killer cell-mediated cytotoxicity suggested that a T cell-independent
mechanism may be operative in immunosuveillance." pg. 214
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Virtually all
Natural Killer cell
activity in humans is mediated by large granular lymphocytes (LGL)
which represent 5-10% of peripheral blood mononuclear cells." pg. 215
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Natural Killer cells express
receptors to IL-2 (interleukin 2) and can proliferate in response to T
cell mitotens and IL-2." pg. 215
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Natural Killer cells originate
in the bone marrow and exhibit a characteristic organ distribution,
their activity being highest in peripheral blood and then, in
descending order, spleen, lymph nodes and bone marrow, and absent in
the thymus." pg. 215
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.....Natural Killer cells and/or their
precursors are highly sensitive to treatment in vivo with cyclophosphamide, B-estradiol and Sr. Animals treated with such agents
and the beige mouse exhibit low levels of NK cell activity and provide
valuable models for studying the in vivo role of NK cells in host
defense against neoplasms." pg. 215
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Also, depletion of Natural
Killer
cells in vivo by treatment with antiasialo-GM1 antibodies (antibodies
injected to remove natural killer cells) resulted in increased
tumorogenicity and percent takes of NK sensitive tumor cells
transplanted into syngeneic and nude mice." pg. 216
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Also, it should be
emphasized that NK-mediated resistance against tumor growth in vivo
was expressed only when a small number of tumor cells were inoculated. Therefore, it was concluded that
Natural Killer cells serve
as a rapidly acting fist-line defense mechanism that is involved in
the early destructive events following tumor implantation." pg.
216
Chem-Tox Comment:
This last statement
provides a biological explanation why cancers would develop more rapidly
in children living in proximity to chemical sources which can suppress
natural killer cell function (i.e. agriculture areas, home pesticide &
chemical use, etc.)
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Activation of Natural Killer cells may
be easily achieved by treatment with interferon, interferon inducers,
interleukin-2 and bacterial adjuvants." pg. 219
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During surgical
manipulation of the primary tumor, potential malignant cells may be
released into the circulation and develop into secondary metastatic
foci. " pg. 224
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Moreover, the suppressive
effects of surgery and anesthesia on NK cell activity may further
facilitate the survival of tumor cells released from the primary or
metastatic tumor growth and contribute to the increased incidence of
metastasis. Therefore, certain BRM, including low doses of interferon,
may prove safe and, if appropriate applied, effective in preventing
further tumor dissemination and metastasis. " pg. 226
Chem-Tox Comment:
Exposure to anesthethesia
compounds have been found to weaken immune system function which also
explains the high incidence of infection following anesthesia exposure.
Department of
Immunology, Smith Kline & French Laboratories
1500 Spring Garden
Street, Philadelphia, PA 19101
Dr See Report with NK
information and Cancer Bullets.doc
Transfer Factor increases
Natural Killer activities
effectively.
Aggressive Breast
Cancer Linked to Virus
Virus That Infects
House Mice Produces Aggressive Cancer Tumors in Humans
By Jennifer Warner
Reviewed By Brunilda Nazario, MD
WebMD Medical News on
Monday, July 12, 2004
July 12, 2004 - The rates of
breast cancer vary throughout the world and now a new study links
breast
cancer to a virus that infects a type of house mice. The findings show
that the virus may play a larger role in breast cancer in the
Mediterranean and Africa than it does in the U.S.
Researchers found that 74%
of Tunisian women with breast cancer tested positive for genes similar
to a virus that infects mice and causes breast cancer. This compares
with only about one-third of cases in people who tested positive from
women in the U.S. Viruses are known to be
involved in the development of several cancers, such as
leukemia and
lymphoma, and several animal and large human studies show that viruses
may also play a role in certain breast cancers.
Researchers say this study
provides additional evidence that a human
breast cancer virus exists and
its prevalence varies in different regions of the world. The results appear in the
Aug. 15 issue of Cancer:
New Proof of Breast
Cancer-Virus Link
Previous studies show that a
virus similar to the mouse mammary tumor virus (MMTV) is associated with
breast cancer. Researchers say the virus may be spread by a species of
house mice that is very common in North Africa but less common in U.S.
In the study, researchers
tested 38 breast cancer tumors from women treated in Tunisia and
compared the results with breast cancer tumor samples from women treated
for breast cancer in other countries. Analysis from two different
laboratories showed that a significantly higher number of tumor samples
from Tunisia tested positive for genes similar to the mouse breast
cancer virus when compared with samples from other countries. Nearly 75% of the breast
cancer tumors from Tunisia tested positive compared with 36% of those
from the U.S.; 38% from Italy; 42% from Australia, and 31% from
Argentina.
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