Wednesday August 13 2014
Getting sodium chloride into cells will kill them
“Salt injection ‘kills cancer cells’ by causing them to self-destruct,” reports the Mail Online.
Despite this headline, there is no new treatment for cancer using salt. The Mail Online reports on an early phase of experiments in laboratories that have worked out how increasing the amount of sodium chloride (salt) within a cell causes it to die.
The researchers did not inject cancer with salt, although they did create a way of getting salt inside cells (but not with a needle and syringe, as you may imagine from the headlines). In fact, they made two new molecules that bind to chloride and take it into cells. This increase in chloride also causes sodium to move into the cell, leading to an increase in sodium chloride.
Scientists already knew that increasing the level of salt within a cell would cause the cell to die, but wanted to know why.
The researchers found that increasing the salt level within normal and cancer cells in the laboratory caused cell death through one of the natural mechanisms, called the “caspase-dependent pathway”. This is a different pathway for cell death than the ones currently triggered by cancer drugs. The researchers hope this knowledge can be used to develop new drugs to treat cancer.
Where did the story come from?
The study was carried out by researchers from South Korea, the US, UK and Saudi Arabia. It was funded by the National Creative Research Initiative programme in South Korea, the US Department of Energy, the Engineering and Physical Sciences Research Council and a European Union Marie Curie Career Integration grant.
The study was published in the peer-reviewed journal Nature Chemistry.
Although most of the Mail Online’s coverage of this study was accurate, the headlines implied that cancer can be killed by injecting cells with salt. This is not the case. Researchers have found out how cells (both healthy cells and cancerous cells) die when there are increased levels of salt inside them. It is important to note that they have only done this in cells in a laboratory, not in any humans or other living creatures.
What kind of research was this?
This was a series of laboratory experiments designed to test compounds that the researchers designed as chloride transporters. They also wanted to better understand how cell death occurs when there is increased sodium chloride within the cell. Understanding the mechanism means that future research can look at ways of targeting it in cancer cells, but avoiding their healthy counterparts.
What did the research involve?
A number of molecular experiments, using cell membranes, were carried out to test compounds that the researchers designed as chloride transporters. After this, they worked out the underlying mechanisms behind cell death by increasing the salt level in cancer cells.
The researchers studied the effect the compounds had on the amount of sodium that then entered the cells through sodium channels, and whether it affected other positive ions, such as potassium and calcium.
The researchers then studied normal human cells from the prostate and lung, as well as rat kidney cells and human cancer cells from the lung, pancreas, colon and cervix, in the lab. These studies aimed to determine how increasing the amount of sodium chloride (salt) within the cells caused them to die.
Further experiments involved reducing the amount of sodium or chloride outside the cells to see what effect this would have on the ability of the cell to increase the level of salt. The drug amiloride (used to treat high blood pressure and heart failure) was used to test the effect of blocking the sodium channels.
What were the basic results?
The researchers made two new molecules, which attach to chloride and increase the amount that enters cells. The increased amount of chloride in the cells caused more sodium to enter. This excess sodium chloride triggered cell death through the “caspase-dependent pathway” (a different pathway to the ones usually induced by cancer drugs). Cell death occurred in all types of cells used – both healthy and cancerous cells.
The molecules were found to have no effect on the levels of potassium or calcium in the cells.
Cell death from this pathway did not occur when the concentration of sodium or chloride outside of the cells was low. Nor did it occur when cells were soaked in amiloride, which prevents increased sodium from entering the cells. These experiments indicated that increased levels of both chloride and sodium (in other words, salt) were required inside the cell to trigger cell death from the caspase-dependent pathway.
How did the researchers interpret the results?
The researchers conclude that, “synthetic transporters can be used to induce an influx of Cl- [chloride] as well as Na+ [sodium], and that this leads to an increased level of reactive oxygen species (ROS), the release of cytochrome c from the mitochondria and induction of apoptotic cell death via the caspase-dependent pathway”. They go on to say that “ion transporters, therefore, represent an attractive approach for regulating cellular processes that are normally controlled tightly by homeostasis”.
This is an early phase in the development of new drugs to combat cancer, and it should be stressed that these experiments did not involve humans or injecting cancer with salt. There is no new treatment for cancer using salt.
This research has, however, shed light on how increasing the salt level in cells can trigger the activation of one of the cell’s pathways for causing cell death.
Two different molecules were developed that transported chloride. The increased amount of chloride within the cells caused more sodium to enter. This caused cell death in a variety of different types of cancer cells in the lab, including healthy cells.
Understanding these underlying mechanisms will help pave the way for new drug developments. However, new drugs based on this science are a long way off, largely because there needs to be a way to use the technology to target only cancer cells, and not damage healthy ones.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.