Application of Phototherapy in Cancer

Phototherapy has long been used to treat cancer, but its disadvantage is that it only applies to accessible tissues such as skin. However, in a study published in the March 9 issue of the Journal Natural Nanotechnology, researchers at the University of Washington Medical School used a mouse cancer model to design a novel phototherapy that could treat "deep" tumors.

Phototherapy has long been used to treat cancer, but its disadvantage is that it only applies to accessible tissues such as skin. However, in a study published in the March 9 issue of the Journal Natural Nanotechnology, researchers at the University of Washington Medical School used a mouse cancer model to design a novel phototherapy that could treat "deep" tumors.

In this study, scientists can transmit light directly to cancer cells and cooperate with free-radical photosensitizers (which can be activated by light) to destroy cancer cells.


Samuel Achilefu, professor of Biomedical Engineering at the University of Washington, said: "Phototherapy is very effective and has few side effects. But it has not been used for deep or metastatic tumors. In short, phototherapy is a photostimulated photosensitive material. Produce free radicals that can induce cell death. But this therapy can only work best in the presence of light and oxygen. This is the biggest obstacle to the development of phototherapy.

The light sources used by researchers depend on a phenomenon called Cherenkov radiation. This phenomenon was discovered in 1934 by Pavel Cherenkov, who won the 1958 Nobel Prize in Physics. Cherenkov radiation is short-wave electromagnetic radiation emitted by the moving velocity in the medium, which exceeds the speed of light in the medium and is characterized by blue light. This phenomenon also occurs in positron emission tomography (PET) scans used by doctors to diagnose cancer.

Achilefu and first author Nalinikanth Kotagiri have been focusing on a research technology called FDG-PET. Using this technique, patients will inject a radiolabeled sugar molecule called fluorodeoxyglucose (FDG) intravenously before PET scans. Tumors absorb sugar molecules to support their rapid growth, so radiofluoride causes tumors to glow during PET scans regardless of where they are in the body.

In this way, the addition of FDG achieves two purposes: first, to maintain the role of imaging agents; second, to provide light source for phototherapy.


"Since FDG can provide us with light sources, the next step is to find a material that can produce toxic substances under light stimulation," Achilefu said. After extensive screening, the researchers chose nanoparticles composed of titanium dioxide. When exposed to light, titanium dioxide can produce free radicals without oxygen. To ensure that free radicals improve the effectiveness of nanoparticles, researchers added a drug called titanocene to the surface of nanomaterials.

"Titanocene entered Phase 2 clinical trials as a chemotherapeutic drug," Achilefu said. It has been shown to be safe, but less effective than placebos.  It also has the characteristic of producing free radicals by reacting with low intensity light. Therefore, we decided to try to use it as an anti-cancer drug and as a phototherapy drug. "

Researchers tested different combinations of nanoparticles, Titanocene and FDG sources in mouse models of human lung tumors and fibrosarcomas: FDG + nanoparticles, FDG + Titanocene and FDG + nanoparticles + Titanocene. It was found that FDG + nanoparticles + titanocene group had the most significant anti-cancer effect. After 15 days of treatment, the tumors in this group were 8 times smaller than those in the untreated group.

The mice in the FDG + nanoparticles group lived 15 days longer than those in the untreated group. Mice in the FDG + Titanocene group also had a 30-day survival period. In contrast, the survival time of mice in the FDG + nanoparticles + titanocene group was prolonged to 50 days.

"Titanium dioxide nanoparticles can kill cancer cells when exposed to light sources, but adding titanocene can significantly improve the therapeutic effect," Azilev said. They can produce different kinds of free radicals. The dose of Titanocene is also used in our method. It is much lower than the dose used as a chemotherapeutic drug. "

Kotagiri added: "The side effects of this treatment should be minimal. It uses both light and photosensitive materials for tumors. This substance is toxic only in the presence of light sources, whereas light sources exist only in tumors. Location. "Currently, the team is planning a small clinical trial to further validate the effectiveness of combination therapy.