PSYCHOLOGICAL or physical stress, including rigorous exercise, can sabotage cancer therapy, a study suggests.
The findings indicate that people about to undergo chemotherapy or radiation treatment should try to relax and avoid intense activity.
Scientists found that getting stressed a day or two before the start of treatment can spark a series of events that allow cancer cells to survive.
The process involves a stress-induced protein called heat shock factor-1, whose job is to help tissues and cells cope with stress.
Previous research has shown that the common protein can help heart tissue survive in a toxic environment.
But laboratory experiments revealed it also comes to the aid of breast cancer cells. Heat shock factor-1 activated another protein that kept tumour cells alive even after they were exposed to radiation and chemotherapy.
The researchers pointed out that one of the known inducers of heat shock factor-1 is exercise.
Dr Govindasamy Ilangovan, from Ohio State University in the US, was lead author of the study, which is published in the journal Molecular Cancer Research.
He said: “I am not against exercise, but the timing is critical. It looks like any intense or prolonged physical activity a couple of days before the start of cancer therapy is highly risky and has potential to reduce the benefits of the treatment.”
He suspects the wide distribution of heat shock factor-1 in the body means the protein could have an impact on many different cancers.
The research points to possible ways of preventing stress making cancer harder to treat.
A “gene silencing” molecule called siRNA restored the process of programmed cell death that kills cancer, the scientists found.
However, siRNA is not suitable for patients and no drug currently exists that mirrors its effects.
The heat shock protein activates another protein called Hsp27 that helps to block cell death. It interacts with a third protein, p21, which allows cells to repair themselves and keep dividing.
“We are doing something to kill the cell, but cells have their own compensatory action to oppose that,” said Dr Ilangovan.
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