Photodynamic therapy (PDT) has been used for many years to treat certain types of skin and bladder cancers. The treatment works by introducing light-sensitive chemicals into the patient’s body, which accumulate in cancer cells. When exposed to light, these chemicals are activated and destroy the cancerous cells. The light prompts the chemicals to produce highly reactive oxygen molecules, which act like tiny biochemical firecrackers, breaking down cancer cells from within while leaving healthy cells unharmed. While PDT is an effective treatment, it has several limitations, including prolonged light sensitivity, poor tissue penetration, and off-target toxicity. These issues can hinder complete tumor destruction and may contribute to cancer recurrence. Researchers have now developed new light-sensitive chemicals that promise to significantly enhance the treatment of aggressive cancers with fewer side effects. In mouse studies, this new therapy completely eliminated metastatic breast cancer tumors. These innovative chemicals, known as cyanine-carborane salts, and their potential in advancing cancer treatment, are discussed in a recent article published in Angewandte Chemie.

Current FDA-approved PDT chemicals tend to remain in the body for extended periods. Following treatment, patients must avoid light for two to three months, as even low levels of light can cause blisters and burns. In contrast, a multidisciplinary team of scientists from the University of California, Riverside (Riverside, CA, USA) and Michigan State University (MSU, East Lansing, MI, USA) discovered that cyanine-carborane salts are eliminated from the body more quickly, staying only in the cancer cells that require treatment. Unlike traditional PDT agents, the salts take advantage of a natural weakness in cancer cells. They are absorbed by proteins called OATPs, which are overexpressed in tumor cells. This mechanism allows for precise targeting without the need for costly additional chemicals that are typically used in PDT to direct the therapy to the cancer cells.

Traditional PDT is also limited when it comes to treating deep-seated tumors because it relies on light wavelengths that only penetrate a few millimeters into the body. However, once inside cancer cells, cyanine-carborane salts can be activated by near-infrared light, which can penetrate more deeply into tissues. This could significantly broaden the range of cancers that can be treated. Given the promising results, researchers are encouraged to continue their work and explore additional cancer therapies that could benefit from these salts. It may even be possible to modify the salts so they can be activated by energy sources other than light, allowing for deeper penetration into the body.

“Our work offers a targeted, safe, and cost-effective treatment for aggressive breast cancers with limited treatment options,” said Amir Roshanzadeh, paper first author and MSU cell & molecular biology graduate student. “It also opens the door to breakthroughs in other approaches for cancer therapy and targeted drug delivery.” 

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