Scientists are developing a “golden bullet against breast cancer”, the Daily Mail has reported. It says that the new research has tested the use of tiny shards of gold to heat up and destroy the deadly cells that help tumours grow.
The story is based on a laboratory study using lasers to heat tiny gold “nano-shells” injected into breast cancer tissue extracted from humans and mice. It specifically looked at using the technique to fight cancer stem cells, a type of resilient cancer cell thought to cause relapses and spreading of cancer. Combining this heating, known as ‘hyperthermia’, with radiotherapy reduced the stem cells’ growth compared to when radiotherapy was used alone.
Although this particular treatment shows promise, it is some way from being usable as a treatment for women with breast cancer. Before it could be tested in humans, this type of new treatment would have to undergo the usual sequence of pre-clinical trials to demonstrate its safety and effectiveness. However, the authors report that similar types of heat are currently being trialled as treatments for other types of cancer, and they may soon inform us of the technique’s potential.
The study was carried out by researchers from Baylor College of Medicine and the M.D. Anderson Cancer Center in Houston, Texas. It was supported by grants from several research foundations, including the US National Cancer Institute and National Institutes for Health. The study was published in the peer-reviewed journal Science Translational Medicine.
It was accurately covered by the Daily Mail, which highlighted that this research is still at a developmental stage.
This was an experimental, early-stage laboratory study, using both mice and human breast cancer cells to explore the behaviour of breast cancer stem cells, in particular when they were exposed to radiotherapy and an experimental form of heat treatment (called hyperthermia).
The researchers say that “residual” cancer stem cells are thought to be resistant to conventional cancer treatments and, as a type of stem cell, can renew themselves over long periods of time. They could therefore be responsible for breast cancer recurring or spreading to other sites in the body, even some years after treatment.
The researchers say that clinical trials of heat treatment (called hyperthermia) have shown that it can damage breast cancer cells, either by killing them directly or by making them more sensitive to radiation treatment. Advances in technology also mean that heat can now be directed to specific locations, such as cancer cells, using safe and non-invasive delivery methods.
The researchers used two laboratory models to test the use of heat therapy. These models used specially cultured breast cancer tumours either grown in genetically engineered mice or grown as tissue taken from human breast cancers. For their experiments, they chose a cancer type that is more aggressive and less responsive to standard treatments.
From both types of tissue, the researchers grew populations of cancer stem cells to test the effects of radiation treatment, both alone and when combined with heat treatment. Heat treatment was performed using gold nano-shells - microscopic particles made of silica coated with an ultra-thin layer of gold. These are designed to settle near cancer cells, where they could then be heated to 42ºC using a laser, transferring heat to the cancer cells to damage them.
The cancer cells were first identified using special staining techniques. One group of cells was injected with the gold nano-shells, treated with radiotherapy, then immediately given 20 minutes of heat treatment. Other groups of cells were exposed to radiotherapy alone, heat treatment alone and mock heat treatment (where the gold was injected but the heat was not applied).
To determine whether heat treatment had any effect on how tumours behaved, the treated cells were transplanted into mice, and the number of cells, the tumour size and cancer markers were measured up to 96 hours after treatment.
The researchers found that in both sets of breast cancer tissue, the cancer stem cells were more resistant to radiotherapy than other tumour cells, increasing in number 48-72 hours after treatment.
However, they found that where cancer cells had been treated with heat after radiotherapy, the tumour size was reduced and the percentage of stem cells had not increased.
Forty-eight hours after treatment, the cells from tumours treated with both radiation and heat were less able to reproduce than cells treated with radiation alone.
The researchers say their study confirms that cancer stem cells are resistant to radiotherapy alone, and that they continue to divide and grow after treatment. They conclude that localised heat treatment using gold nano-shells can reduce this resistance to radiotherapy.
This laboratory study using mice and human breast cancer cells appears to demonstrate that localised heat treatment can reduce breast cancer stem cells’ resistance to radiotherapy. This is of particular note as these are the type of cells that are thought to be responsible for relapses of the disease. As such, this novel technique holds some promise for the future.
However, this was an early, experimental test of the technology in isolated tissue. Far more research is needed before we can determine the efficacy and safety of this treatment or use it to treat women with breast cancer. The technology is reportedly being trialled for the treatment of neck and head cancers, which may soon give a clearer picture of its potential.