Researchers in Abu Dhabi have used tiny light-sensitive nanoparticles to destroy pancreatic cancer cells in mice, an approach that they hope could eventually be used to treat people.
While the method’s possible use in humans is a long way off, the research highlights a novel therapeutic approach against a condition that currently has low survival rates.
The work by the New York University Abu Dhabi scientists, released last month before World Cancer Day, which falls today, found that the method prolonged survival and shrank tumours in mice.
The nanoparticles contained a photothermal dye that generated heat when, in this case, near-infrared light was shone on the tissue.
After being injected into the mice, the nanoparticles migrated to the cancer cells and were heated by the near-infrared light to more than 50°C. These temperatures weakened or killed the cancer cells.
“People have used photothermal therapy for a long time, oftentimes by using a direct source to heat the tissue in question, but there are some limitations to that,” said Dr Mazin Magzoub, associate professor at NYU Abu Dhabi, who led the work.
“By using photothermal agents, we can do this much more specifically, targeting the cancer cells in the tumours and killing them while minimising damage to the healthy tissue.”
Photothermal agents often do not dissolve easily in water or blood. They are unstable and typically just a fraction arrive at the tumour site.
Turning up the heat in cancer fight
However, by encapsulating the agents in a tumour-targeting nanoparticle, the scientists prevented degradation and caused the agent to be carried to the tumour.
The micro-environmentAround tumour cells tends to be acidic because the cells are dividing rapidly, so peptides or small proteins attracted to acidity were attached to the nanoparticles. These peptides hooked to the membranes of the cancer cell membranes, which then took up the nanoparticles.
“That allows us to accumulate a sufficient amount of these photothermal agents in the tumours, where they can be taken up by the cancer cells, and we apply a laser to them to activate them, leading to the heating,” Dr Magzoub said.
“The laser system we use is near-infrared light. Near-infrared light is attractive for a number of reasons. It is scattered and absorbed less than visible light – that allows you to penetrate further into the tissue.
“At the same time, because of this lower absorption and scattering, it’s less damaging to surrounding tissue.”
The nanoparticles are made of a mineral called hydroxyapatite, which is found in teeth and bones. This is naturally broken down by the body into calcium and phosphate ions, which can be used in the formation of new bone. Also, Dr Magzoub said that the calcium ions aid the anti-cancer effects of drugs.
Human pancreatic cancer cells had previously been introduced into the mice, who developed tumours because their immune system had been weakened so that the cells would not be rejected.
Dr Magzoub said that his team was “pleasantly surprised” that the photothermal nanoparticles reduced the size of tumours and caused the mice to live significantly longer.
In addition to carrying out tests on mice, the researchers found that the nanoparticles destroyed lab-grown cancer cells.
Pancreatic cancer in focus
“Pancreatic cancer is one of the ones that we spend quite a bit of time on because it’s one of the cancers that’s increasing in incidence but it’s one of the cancers that has the worst prognosis,” he said.
“So there is a need for new effective therapeutic strategies for these types of cancers, such as pancreatic cancer, that would either supplement or supplant the current therapeutics.”
According to Cancer Research UK, about five in 100 pancreatic cancer patients in the country survive their disease for at least a decade.
The survival rate is low partly because the condition is often diagnosed late, by which time it is more difficult to treat successfully.
Although the new study, published last month in Cell Reports and Physical Science, looked at pancreatic cancer, the scientists’ approach may be widely applicable, because acidity around tumour cells is common.
Dr Magzoub cautioned that it was “a long route” from the treatment being used in the laboratory to its adoption as a therapy in people. This process would involve many further tests and clinical trials, he added.
One strategy to be looked at in future involves combining photothermal therapy with chemotherapy. This could make chemotherapy more targeted, improving effectiveness and cutting the risk of side effects.
