Cancers can be halted by targeting protein/Worriers more prone to cancer

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Deadly spread of cancer halted

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12:21 05 June 03

 

NewScientist.com news service

 

The spread of cancers through the body could be halted by targeting a

protein that helps cells latch on to each other, reveals a new study.

 

The spreading of cancer from an initial tumour to other parts of the body -

called metastasis - frequently means there is little hope a person can be

saved. But scientists have now modified a naturally occurring human protein

to disrupt this deadly process in mouse models of human breast cancer.

 

" We were able to significantly reduce the spread of the disease and decrease

tumour growth without any evidence of toxicity, " says Gary Jarvis, a

microbiologist at the University of California in San Francisco. " If we can

stop metastasis in humans, we will have gone a long way towards successfully

treating cancer. "

 

" It's when tumours spread to essential organs, such as the liver or lung,

that they become fatal, " says colleague Constance John, a research chemist.

" There is nothing to date that has been approved by the Food and Drug

Administration for treatment of cancer that works on that process. "

 

 

Stick together

 

 

The team modified a protein that seems play an important role in helping

cells stick to each other. This ability aids metastasis by allowing

cancerous cells that enter the bloodstream to lodge themselves in other

parts of the body.

 

The team, lead by Jarvis in the US and Hakon Leffler at the University of

Lund in Sweden, singled out a human protein named galectin-3. This is from a

family of proteins called lectins that bind to sugar molecules on the

surfaces of cells.

 

Galectin-3 is known to play a role in cancer formation, particularly in

promoting cell-to-cell adhesion. " The idea was to break that contact and

inhibit secondary cancer formation, " says Jarvis. So the team removed the

key part of galectin-3 that normally allows cells to stick to each other.

The modified protein also occupies the site on a cell's surface blocking

normal galectin-3 from binding. This stops cells from adhering to each

other.

 

The modified protein more than halved the number of mice that developed

metastatic tumours. Cancer implanted into the mice spread to the lymph nodes

or other organs in 11 of the 20 control mice given sham injections, but only

four of the 20 mice given the truncated protein.

 

 

Slow growth

 

 

The growth of the implanted tumours was also significantly less in mice

treated with the modified protein compared to the control mice.

 

 

" It's not only affecting metastasis, " Leffler told New Scientist. " It's

reducing the primary tumour a lot. " Importantly, he adds, the novel

treatment did not cause any adverse reactions.

 

A drug therapy targeting galectin-3 might one day be effectively used in

combination with currently available cancer medications like chemotherapy

and radiation, say the researchers. Although, the results are " optimistic " ,

Leffler cautions that " an animal model is not human " .

 

" We're not trying to develop a cure for cancer, " says John. " What we're

trying to do is make cancer a disease that one can live with. "

 

 

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It is not the kind of news that will help matters. A study involving over

60,000 people suggests that people prone to anxiety are more likely to get

cancer.

 

The findings will add to the controversy over whether purely psychological

factors such as stress, anxiety and depression can trigger cancer. Part of

the problem with this kind of study is that it is hard to exclude with

certainty the influence of behavioural factors, such as lack of self-care,

poor diet and smoking.

 

A team of psychiatrists led by Arnstein Mykletun at the University of Bergen

in Norway followed up 62,591 people who took part in a massive medical

survey of people living in one county in Norway during 1995 to 1997. The

Norway National Cancer Registry was used to identify participants in the

survey who had developed cancers or premalignancies - abnormal cells that

can turn cancerous.

 

Those who scored highly in an anxiety test in 1995 were about 25 per cent

more likely to have premalignancies, the team told a meeting of the American

Psychiatric Association in San Francisco last week.

 

 

Inconsistent results

 

 

Previous studies of the link between mind and cancer have produced

inconsistent results, Susanne Oksbjeg Dalton's team at the Institute of

Cancer Epidemiology in Copenhagen, Denmark, concluded in the most recent

review. But two studies did find an association between psychological stress

and two specific types of tumours, lymphomas and malignant melanomas.

 

 

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These results are intriguing, as lymphomas and melanomas are linked with

immune system dysfunction. One theory is that psychological states like

stress, anxiety or depression lower immune activity, compromising the body's

constant surveillance for premalignant or cancerous cells, and thus allowing

cancers to grow.

 

Support for this theory comes from another study presented at the San

Francisco meeting. Sandra Nunes's team at the State University of Londrina

in Brazil compared 40 depressed adults who were not on medication with 34

healthy controls.

 

In the depressed patients, there were dramatic reductions in immune

functions, including white blood cell activity and antibody responses.

However, Mykletun's team did not find a statistically significant link

between depression and premalignancies in the Norwegian study, as they did

with anxiety. Dalton also points out that it is vital that factors like

smoking are adequately controlled for in research of this type. People

suffering psychological stress are more likely to smoke, greatly increasing

their risk of cancer. Mykletun's team did try to take this into account, but

screening for smokers and determining how much they smoke is difficult in

large studies like the Norwegian one.

 

The debate looks set to run and run. Until it is resolved, anxious people

will have one more thing to worry about.

 

 

Raj Persaud

 

http://www.newscientist.com/news/news.jsp?id=ns99993767

 

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