A new study shows that near-infrared phototherapy could be a promising treatment for individuals with pleural mesothelioma, according to a press release from Nagoya University.

The study, which tested mice and 12 human cell lines with malignant tumors, concluded that near-infrared photoimmunotherapy was a low-risk and effective method of killing cancer cells without harming surrounding cells due to the nature of near-infrared light, according to Kazuhide Sato, a researcher for the Institute for Advanced Research. There are several studies that suggest that near-infrared photoimmunotherapy is an effective cancer treatment, but little or no studies that focus on using this treatment for mesothelioma.

Malignant mesothelioma can be detected with high levels of podoplanin, a protein typically found in cancer cells. This type of treatment targets the expression of podoplanin. First, an anti-podoplanin antibody called NZ-1-IR700 was injected into the mice. This compound binds to podoplanin to both illuminate tumor cells and allow them to absorb light energy. This type of antibody is non-toxic to the body. When Sato’s team focused a near-infrared light into the chest cavity of mice, they saw the tumor cells rupture.

Sato suggested that further studies look into using a drainage device similar to the one used in patients to drain excess fluid in the lungs. The divide would help diffuse light directly into the chest cavity and cause more effective results.

diagram of pleural mesothelioma phototherapy treatment

One possible benefit of this treatment is that healthy cells are less likely to be destroyed. Sato acknowledged that NZ-1 would also bind to podoplanin on lymphatic epithelial cells, but he also suggested using CasMab, an antibody that detects the differences between cancer cells and healthy cells. With or without CasMab, the immunotherapy is regional and can help preserve the lungs. The anti-podoplanin antibodies are also not toxic to cells unless a near-infrared light is on them.

That being said, Sato said that there need to be more studies to ensure that the treatment will not unnecessarily harm the body. This study was partially performed on human cell lines with malignant tumors, but not on human beings.

Near-infrared photoimmunotherapy is a treatment that is perfect for patients with mesothelioma since it is usually localized to the lungs. Sato explained why this therapy works in the chest cavity.

"The lungs and chest cavity contain a large amount of air and are thus very good at effectively transmitting near-infrared light," says Sato. "NIR-PIT is a safe phototherapy option that can target a region of interest. The antibody-IR700 conjugate is also non-toxic to the body in the absence of near-infrared light irradiation. We thus thought that NIR-PIT could be an effective strategy for controlling localized MPM."

Currently, near-infrared photoimmunotherapy is in phase III clinical trials for head and neck cancer treatments for individuals who have failed at least two lines of therapy. The Food and Drug Administration has fast-tracked approval and this could be a possible treatment in the next few years, according to Sato.

Near-infrared light is not visible to the naked eye, but the wavelengths can penetrate the skin up to four inches. The body detects near-infrared light as heat. This type of light does not damage the skin as ultraviolet light would.

Mesothelioma is a rare type of cancer that affects the epithelial lining in the lungs, heart, and other organs. Typically mesothelioma is diagnosed in the late stage with very limited treatment options and a poor prognosis. Near-infrared photoimmunotherapy could bring hope to people with mesothelioma or their families.

For a full copy of the study, go to PubMed.

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