The human immune system can use proteins from melanoma, the most serious type of
skin cancer, to kill off cancer cells, according to researchers at Tel Aviv
A small group of proteins of the Ras “family” controls a
large number of cellular functions, including cell growth, differentiation and
survival; because the protein has a hand in cellular division, mutated Ras –
which can be detected in one-third of all tumors – contributes to many human
cancers by allowing for the rapid growth of diseased cells.
Kloog of Tel Aviv University’s neurobiology department, Dr. Itamar Goldstein of
TAU’s Sackler Faculty of Medicine and the Sheba Medical Center and colleagues
have found cancer-promoting oncogenic Ras can also alert the immune system to
the presence of cancer cells. The team published their findings in the Journal
For the first time, the researchers have shown the
transfer of oncogenic Ras in human cells from melanoma cells to T cells, which
are white blood cells in the immune system.
This transfer allows the
immune cells to gather crucial intelligence on what they are fighting and
develop the necessary cytokines, or signalling molecules, to kill the melanoma
Kloog suggests that a drug that enhances the transfer of the
oncogene from the tumor to the immune cells is a potential therapy to augment
the anti-cancer immune response.
Although they found that immune cells
often exchange proteins among themselves, the discovery that melanoma cells
transfer mutated Ras is an intriguing first. And it’s this initial transfer that
begins a “positive feedback loop” – the scientists incubated T-cells from
patients with human melanoma cells that had originated from tumors. They
uncovered a circuit that runs between the cancer and immune cells. Once the
melanoma cells pass oncogenic Ras to the T-cells, the T-cells are activated and
begin to produce cytokines, which enhances their capacity to kill cancer
As these melanoma cells pass along the mutated Ras, the immune
cells become increasingly active.
Eventually, enough oncogenic material
is transferred across the immune cells’ threshold, causing the T-cells to act on
the melanoma cells from which the oncogenic Ras was derived. Ultimately, this
transfer tips the scales in favor of the immune cells, the researchers
The next step is to develop a therapy to enhance the transfer in
patients with cancers linked to oncogenic Ras.
Although their research
has so far focused on melanoma, which is known to elicit the response of the
immune system, he believes that this finding could be applicable to other types
of cancers. The researchers believe their research will lead to a better
understanding of how the immune system fights tumors.
“It’s a part of the
interaction between cancer and the immune system that is not well known,” they
“We are trying to gather more comprehensive data on all the
proteins that are being passed around and how this information impacts the
immune system’s response to cancer.”
GREEN IS BEAUTIFUL Women who drink
green tea may lower their risk of developing some digestive system cancers,
especially cancers of the stomach, esophagus and colon/rectum, according to a
study led by researchers from Vanderbilt- Ingram Cancer Center in
The study was headed by Prof. Sarah Nechuta and published in
the American Journal of Clinical Nutrition.
To determine green tea’s
impact on cancer risk, the investigators surveyed women enrolled in the Shanghai
Women’s Health Study, a populationbased study of approximately 75,000
middle-aged and older Chinese women. During the initial interview participants
were asked if they drank tea, the type of tea consumed and how much they
consumed. Most of the Chinese women reported drinking primarily green
The researchers found that regular tea consumption, defined as tea
consumption at least three times a week for more than six months, was associated
with a 17 percent reduced risk of all digestive cancers combined. A further
reduction in risk was found to be associated with an increased level of tea
drinking. Specifically, those who consumed about two to three cups per day (at
least 150 grams of tea monthly) had a 21% reduced risk of digestive system
cancers, especially stomach/esophageal and colorectal cancers.
digestive system cancers combined, the risk was reduced by 27% among women who
had been drinking tea regularly for at least 20 years,” said Nechuta. “For
colorectal cancer, risk was reduced by 29% among the long-term tea
These results suggest long-term cumulative exposure may be
Tea contains polyphenols or natural chemicals
that include catechins like EGCG and ECG. Catechins have antioxidant properties
and may inhibit cancer by reducing DNA damage and blocking tumor cell growth and
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