A near-infrared light treatment has been developed for a rare type of malignant lung cancer by scientists from Nagoya University in Japan.
A study published in the journal Cells examined how near-infrared light treatment and a cancer-targeting compound could help improve the treatment of malignant pleural mesothelioma (MPM), a rare type of lung cancer.
MPM, which affects the lung lining, rarely spreads to other parts of the body but is usually diagnosed too late, leading to a poor prognosis and very limited treatment options.
Near-infrared photoimmunotherapy
Nagoya University oncologist Kazuhide Sato and colleagues studied the effectiveness of near-infrared photoimmunotherapy (NIR-PIT) as a treatment strategy for MPM.
The US Food & Drugs Administration (FDA) has fast-tracked the approval of NIR-PIT for treatment of a type of malignant head and neck tumor.
Laboratory of Molecular Theranostics (LMT) leader Hisataka Kobayashi and colleagues found that NIR-PIT effectively killed cancer cells through necrosis and stimulating the release of antigenic intracellular contents that initiate immunity against surviving cancer cells.
NIR-PIT works by initially injecting a cancer-targeting compound, composed of an antibody, which targets a specific structure on the cancer cells, and a photoabsorber called IR700.
When near-infrared irradiation is used on the affected body part, the compound aggregates on the cancer cell membranes, causing acute cell rupture and tumor death.
Sato said: "The lungs and chest cavity contain a large amount of air and are thus very good at effectively transmitting near-infrared light."
"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," he explained.
NZ-1 and podoplanin
In order for NIR-PIT to work on MPM, they needed a compound specifically targeting MPM cancer cells. They examined an antibody called NZ-1, which targets a specific part of a transmembrane glycoprotein called podoplanin.
Podoplanin is normally found on many cell types in the human body, but is particularly abundant in some types of cancer cells, including MPM.
The researchers found that podoplanin was widely expressed in a variety of MPM cell lines and that NZ-1 conjugates well with the photoabsorber IR700. They also discovered that NZ-1-IR700 specifically bound to podoplanin on cells in the lab.
Results showed that when podoplanin-positive cells, including MPM cancer cells, were mixed with NZ-1-IR700 and then exposed to near-infrared light, the cells immediately swelled and ruptured.
The study involved injecting NZ-1-IR700 in mice with MPM tumors. The scientists observed that the compound gradually accumulated at the tumor sites and when near-infrared light is shone on the tumor sites, fluorescence from cancer-tagged cells were reduced, indicating the treatment worked well as an anti-cancer strategy.
However, Sato and the other Nagoya University researchers say that further studies are needed to find ways that ensure the treatment will not kill healthy podoplanin-positive cells.
They also concluded that a more focused dose of light could be achieved by shining it into a drainage device inserted into the chest cavity, which is normally used anyway in MPM patients to drain the chest from excess fluids.
