Researchers have been trying to locate a key mechanism triggered by chronic stress that fuels the cancer stem cells and increases their growth. More recently, this mechanism was studied by the researchers in mouse models suffering from breast cancer.
The findings of this study are present in The Journal of Clinical Investigation and depict the role of epinephrine in this mechanism.
Association of Stress with Tumor Growth
To check how stress affects the growth of cancer cells in the rodents, the researchers placed all the mice in restrictive enclosures for one week. Later on, they separated them into different groups.
One of these groups was placed in a big-sized, highly comfortable enclosure for discontinuation of stress. This group was referred to as the control group. On the other hand, the second group was placed in a small enclosure for 30 days. This group was termed as the experimental group.
Following this investigation, the scientists noticed that mice undergoing stress experienced changes in their behavior secondary to anxiety and depression. Moreover, they also developed larger cancer tumors as compared to the mice present in the control group.
The tumors were found to be growing at an extremely fast rate. On the whole, the mice exposed to stress also had an increased number of cancer stem cells as compared to the other mice.
Yet, it was unclear how stress was contributing to cancer progression at this point.
As per the experts, the direct signaling network existing between the stress pathways and the cancer-propagating system was unknown. Developing a better understanding of the biochemistry behind how stress increases cancer cell growth.
The Role of Epinephrine
The researchers looked closely into different physiological factors that changed under the effects of stress. They found that the role of a hormone called epinephrine was to be considered in this regard.
The mice under stress were found to have higher levels of epinephrine as compared to those in the control group. Moreover, the participants of the experimental group that received a drug blocking ADRB2, a type of epinephrine receptor, were found to have a smaller number of cancer cells and lower amounts of stem cells in their bodies.
Most of the people relate stress with the suppression of the immune system due to cortisol. However, in this research, the cortisol levels were found to be lowered after 30 days of stress.
So is it only epinephrine that causes cancer cells to thrive? Yes.
When epinephrine binds to ADRB2 receptor, it causes an increase in the levels of lactate dehydrogenase, an enzyme that gives the muscles energy in danger situation. This energy, in turn, allows the person to tackle the fight or flee from the situation.
Lactate is a compound produced as a byproduct of this energy group. In people suffering from cancer, the cancer cells start feeding on lactate i.e. it provides them with more energy.
This indicates that a stressed out person will have more lactate dehydrogenase in its system which will increase the levels of lactate. Lactate will, in turn, activate cancer-related genes and allow cancer cells to flourish.