In a study published in Nature Neuroscience researchers at Okayama University developed a method to stimulate different types of nerves within breast tumours and found that while some nerves abetted tumour growth, some prevented it.
Autonomic nerves are messengers that carry signals from the brain to the organs in our body.
In recent years scientists have found several links between the autonomic system and cancer.
Autonomic nerves are involved in the progression of prostate cancer.
On the other hand, prostate and breast cancer patients can have a lower risk of death when given nerve-blocking drugs.
However, the direct relationship between the autonomic system and breast cancer is still unclear.
A research team led by Professor Kamiya Atsunori at Okayama University has now examined autonomic nerves found within breast tumours and unraveled their contribution to tumour growth.
Our organs are permeated by multiple nerves.
Hence, isolating and analysing any one nerve type is tough.
Additionally, targeting nerves only within the breast tumour is also difficult.
To circumvent these challenges, the research team developed a virus-based tool.
This consisted of an innocuous virus with the ability to genetically modify tissues to stimulate or suppress specific nerve types.
In this case, the two main autonomic nerves of interest were sympathetic and parasympathetic nerves.
Since the virus would have to be injected, it would only bring about these changes within the injected tissues.
The tool was first tested on breast tumours implanted into rats.
Stimulating the sympathetic nerves in these rats resulted in growth of tumours.
The tumours also spread to distant organs such as the lungs.
Conversely, stimulation of the parasympathetic nerves resulted in reduced tumour growth.
These tumours also showed a lower presence of immune checkpoint inhibitors, which are cancer-promoting proteins.
The virus was then injected to inhibit the two nerve types within the tumours.
Deactivating the sympathetic nerves suppressed the growth of tumours while deactivating parasympathetic nerves promoted their growth.
The team subsequently scrutinised the distribution of nerves within tumour samples of 29 breast cancer patients.
The patients with a high presence of sympathetic nerves were indeed the ones with lower chances of survival, while those with a high abundance of parasympathetic nerves, had better chances of survival.
The tumour samples with higher parasympathetic presence also had fewer immune checkpoint inhibitors.
This study is the first to show how stimulation of different nerves within breast tumours can determine the fate of the cancer.
“Genetic sympathetic nerve denervation and parasympathetic neurostimulation of tumours may suppress breast cancer progression and are therefore a potential novel therapeutic approach for breast cancer”, concluded the researchers.
Source: Okayama University