Short-term stress 'boosts anti-tumour activity'

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Washington, Sep 22 (ANI): In a study on laboratory mice, researchers at the Stanford University School of Medicine have shown that bouts of relatively short-term stress can boost the immune system and protect against one type of cancer.

The researchers also said that the beneficial effects of this occasional angst could last for weeks after the stressful situation has ended.

The finding is surprising because chronic stress has the opposite effect-taxing the immune system and increasing susceptibility to disease.

"This is the first evidence that this type of short-lived stress may enhance anti-tumor activity. This is a promising new way of thinking that calls for more research. We hope that it will eventually lead to applications that help us to care for those who are ill, by maximally harnessing the body's natural defenses while also using other medical treatments," said Dr. Firdaus Dhabhar.

The researchers studied a particular type of skin cancer called squamous cell carcinoma that is known to be vulnerable to attack by the immune system.

Certain types of stress, such as the so-called fight-or-flight response to an immediate but temporary threat, has been shown to increase the recruitment of immune cells to the surface of the skin and the surrounding lymph nodes-presumably in preparation for imminent injury.

"Acute stress galvanizes an organism's protective systems. But although it's one of nature's fundamental survival systems, thus far it's been rather underappreciated," said Dhabhar.

The researchers focussed on understanding the physiological effects of both acute and chronic stress.

They investigated the effect of short-term, or acute, stress on 30 laboratory mice exposed for 10 weeks to thrice-weekly doses of cancer-causing ultraviolet light.

They found that fewer of the mice that had been acutely stressed developed skin cancer during weeks 11 through 21, and that those that did exhibited a lower total amount of tumours (a measurement called tumor burden) than the non-stressed mice.

The stressed mice weren't protected indefinitely-almost 90 percent of the mice in both groups developed cancer after week 22, though the stressed group continued to have fewer tumours until week 26.

"It's possible that the pre-tumour cells were eliminated more efficiently in the group that was stressed.

There may also have been a longer-term enhancement of immunity as we have seen in our non-cancer-related studies. However, acute stress did not lower tumour burden beyond week 26. We are in the process of determining why," said Dhabhar.

However, other stress-induced changes lingered for weeks.

The researchers found that, during the same time period, the skin of the stressed mice had higher levels of immune-activating genes than did the control group, almost as if the mice were preparing for battle.

He compared the effect to how drug-makers often increase the potency of vaccines by including generic immune-activating molecules called adjuvants.

But he is convinced that acute stress may be better for us than most of us think, and that bio-behavioural interventions are worth investigating.

The study will be published in the journal Brain, Behavior, and Immunity. (ANI)

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