Physical and Psychological Stress could Thwart Cancer Treatment

2010-09-21 13:09

Researchers say a stress sensitive protein helps cancer cells survive chemotherapy and radiation treatments. The findings are important for patients undergoing cancer therapy.

According to the research, stress induces a series of events that releases a protein that helps cancer cells survive. Even rigorous exercise, one to two days before cancer treatment, could render treatment less effective.

The findings likely apply to all types of cancer treatment, though the study was done on breast cancer cell cultures. Ohio state researchers say heat shock factor-1 releases a protein that helps heart cells survive even in a toxic environment. They suspected the protein might also help cancer cells survive the toxicity of chemotherapy and radiation.

How Stress Helps Cancer Cells Survive

Heat shock factor 1 releases the protein Hsp27. In experiments, the researchers found that the presence of Hsp27 was also associated with lower levels of other proteins that induce cell death. When they found a way to block the protein with siRNA, a molecule that interferes with the protein, cell death occurred again.

The study authors warn against rigorous exercise before starting cancer treatment. According to Govindasamy Ilangovan, lead author of the study and associate professor of internal medicine at Ohio State, exercise is known to release heat shock factor-1. “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”.

Even the stress of UV radiation was enough to induce the release of the protein, in turn aiding cancer cell survival. In experiments, the researchers noted the behavior of Hsp27 after UV-C radiation that damages DNA. In each experiment, the presence of Hsp27 was found to reduce the death of cancer cells.

Blocking the protein reversed the effect of heat shock factor-1. “We clearly showed that a reduction in the level of the Hsp27 protein made the cancer cells more susceptible to both treatments,” Ilangovan said.

The scientists also noted a relationship between Hsp27 and a protein called p21 that allowed cells to repair themselves, even when cancer cell DNA is damaged. “It looks like a compensatory act. We are doing something to kill the cell, but cells have their own compensatory action to oppose that,” Ilangovan said.

In the studies, the scientists also found that Hsp27 levels peak within 48 hours after stress that activates heat shock factor-1. “The process that sets these activities in motion takes a couple of days,” Ilangovan said. “It is not proven in a clinical setting, but our hypothesis leads us to strongly caution cancer patients about avoiding stress because that stress might trigger recurrence of cancer cell growth.”

Cancer patients who exercise vigorously before chemotherapy or radiation may unwittingly be sabotaging the effectiveness of treatment. The series of experiments from researchers shows the presence of the protein released by heat factor-1, in response to stress, plays an important role in helping cancer cells survive treatment. The protein peaks at 48 hours, and may be an important consideration for patients undergoing cancer therapy.

Ohio State University

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