Could cold temperatures inhibit cancer growth?

A promising study carried out by researchers at the Karolinska Institutet shows potential to provide therapeutic care to prevent tumour growth.

The study

The study, published in the journal Nature, compared tumour growth and survival rates in mice with various types of cancer including fibrosarcoma, breast cancer, melanoma and pancreatic ductal adenocarcinoma. Mice that were exposed to temperatures of 4 degrees Celsius had a significantly slower tumour growth when compared to mice held in rooms that were 30 degrees Celsius.

The mice kept at 4 degrees Celsius showed a robust effect on tumour growth and approximately 80% inhibition was recorded on day 20. The mice kept at 30 degrees Celsius showed no similar anti-cancer effects and the tumour grew at a normal rate. Due to this, the overall survival of tumour-bearing mice exposed to 4 °C was almost doubled when compared to the mice kept at 30 degrees Celsius. After the mice held at cold temperatures were returned to a normal room temperature they inhibition of tumour growth stopped and the tumours grew as normal, showing the effect was only beneficial whilst kept at that temperature.

The study suggests that due to the activation of heat-producing brown fat, also known as brown adipose tissue (BAT), the tumours were starved of the glucose they need to increase in size. It is well-known amongst medical groups that grow through "glycolysis" or glucose uptake. The researchers proved this as when they provided the mice held at 4 degrees Celsius with a 15% glucose water drink this counteracted the effects of the cold environment and the tumours grew as normal. By starving the cancer cells of the glucose it requires to grow, the tumour growth is severely hindered and, alongside other interventions, could be used as a cancer treatment.

Controls

The researchers also measured the internal body temperatures of both groups of mice and there was no difference in subcutaneous body temperatures, meaning that the effect couldn't have been caused by changes to internal body temperature.

By surgically removing the BAT from the mice, they confirmed that it was the BAT that was responsible for using up all available glucose, thus preventing glucose entering the tumours providing energy for them to grow.

Further to this, studies have shown that exposure of white fat cells, which is by far the most common type, causes a browning of the white fat into what's called "beige" fat. This beige fat behaves similarly to brown fat in that it consumes glucose to warm the body. So extended periods of cold could affect the bodies immune system and increase its ability to fight off tumours although there is no evidence to confirm how long beige fat stays within the body.

Human applications

To study the human relevance of their findings, the researchers performed tolerable cold exposures on healthy humans and in one patient with cancer. The healthy volunteers (3 males and 3 females between 22 and 25 years) were exposed to a mildly cold ambient temperature at 16 degrees Celsius for 2–6 hours per day for 14 consecutive days. PET scan analysis showed that both males and females exhibited marked activation of BAT around the shoulders and neck, where brown fat is stored on the body.

To prove that cancer didn't hinder BAT activation, they exposed the cancer patient (who had hodgkins lymphoma) to a mildly cold 22 degrees Celsius for 7 days. This activated the BAT, but not by as much as the volunteers held at 16 degrees Celsius and slowed the growth of the tumour, but not by as much as the mice held at 4 degrees Celsius. When returned to a warm 28 degrees Celsius the tumours growth returned to normal levels.

The researchers then suggest that as the human body can stand temperatures of 16 degrees Celsius with no adverse side effects that this should be considered as a possible therapeutic treatment for cancer patients.

Summary

The research has proven that a suitably cold environment activates brown adipose tissue in humans and that brown adipose tissue starves tumours of the glucose they need to grow. I am not a medical professional but reflecting on the work of medical professionals it seems that cold stress therapy is a viable addition to the treatments that have shown effectiveness in slowing tumour growth in several cancers.