How chronic stress fuels cancer

Scientists say they now have a better understanding of how chronic (long-term, sustained) stress can accelerate the growth of cancer cells, and how this damage could be avoided.

While the correlation between stress and health issues – such as gut health, heart problems and cognitive impairment – is well-established, researchers have now located a key mechanism, which chronic stress triggers, that fuels the growth of cancer stem cells that tumours originate from.

The report, published in The Journal of Clinical Investigation, is one of the first to link chronic stress specifically with the growth of breast cancer stem cells in mice.

Principal investigator Quentin Liu, from the Institute of Cancer Stem Cell at Dalian Medical University told Medical News Today that while the direct signalling network between stress pathways and a cancer propagating system still remains “almost completely unknown”, a better understanding of the biochemistry that causes stress to increase the growth of cancer cells “could lead us toward targeted drug interventions”.

In these findings, researchers found the hormone epinephrine was responsible for the tumour growth, not cortisol. This hormone, when binding with ADRB2 cells, boosted levels of lactate dehydrogenase, an enzyme that normally gives muscles an “injection” of energy in a danger situation as part of a fight or flight mechanism. As a result, this led to an energy boost in the production of lactate, which feeds the harmful cancer cells and allows them to acquire more energy.

This means a person with chronic stress will have too much lactate dehydrogenase in the system which in turn will activate genes related to cancer growth and allow those cancer cells to thrive.

“When most people think of stress they think it’s cortisol that’s suppressing the immune system,” says Keith kelley, the co-author of the report. However cortisol was actually lower after a month of stress, while epinephrine was much higher, he notes.

Researchers confirmed these results by studying the blood epinephrine levels in 83 people with breast cancer, and found people with higher levels of the stress hormone also had higher levels of lactate dehydrogenase in cancer tumours and were more likely to have poorer outcomes following treatment.

Researchers also considered how they could block epinephrine’s effect on the system and found vitamin C to be the most promising substance. When tested on mice, scientists found stressed mice injected with vitamin C experienced tumour shrinkage.