New Korean research presents a new strategy for breast cancer treatment that uses photodynamic therapy to kill cancer cells selectively, Yonsei said Monday.

Photodynamic therapy (PDT), like radiation therapy, is a treatment that uses a photosensitizer agent and a specific type of light to produce a form of “active oxygen.” The particular kind of oxygen destroys then nearby cancer cells.

However, because most photosensitizers do not selectively target cancer tissue only, the therapy often damages surrounding tissues. Cancer cells in a state of hypoxia (lacking in oxygen and nutrients) are more resistant to radiation energy than healthy cells, making immunotherapies often ineffective.

Professors Nam Ki-taek (left) and Yoon Ju-young

The new research, led by Professors Nam Ki-taek from Yonsei University and Yoon Ju-young of Ewha Womans University, aims to work around the limitations and use the nanotechnology to kill cancer cells even in hypoxic states selectively, it said.

The researchers developed a new supramolecular approach that uses uniform nanostructures (PcS-MA) to kill cancer cells selectively, according to Yonsei.

PcS-MA nanostructures are created by combining phthalocyanine photosensitizer (PcS) with anticancer drug mitoxantrone (MA).

Findings showed a significant contrast in the PcS-MA treatment versus other treatments, according to the research. The study observed the effects of three types of therapy on mice with breast cancer -- a Pcs treatment alone, an MA treatment alone, and a combination PcS-MA treatment.

Results showed the size of cancer cells increased by about 400 percent in the PcS and MA-single treatment arms. In contrast, cancer cells shrank by around 80 percent in the PcS-MA arm, the study showed. The mice also secreted PcS-MA synthetic material in their urine, proving its safety, according to the data.

“The research is a useful way to remove cancerous cells in hypoxic conditions, which are difficult to treat, and is significant in offering alternative therapies for patients who cannot get surgery or radiation therapy,” the researchers said. The newly developed technique also minimizes the effects of the treatment on surrounding healthy tissues, they added.

“In this experiment, there was almost no normal tissue damage, which was a disadvantage of conventional photodynamic therapy, and the photodynamic therapy remained in the body for several days without any signs of toxicity in the main internal organs,” Professor Yoon said.

The team will investigate the PcS-MA compound's effect on other cancers such as hepatocellular carcinoma and stomach cancer. The findings were published in the recent issue of ACS Nano.

yjc@docdocdoc.co.kr

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