New York, Aug 15 (IANS): Researchers have developed a novel approach to defeat the defence mechanism of ovarian cancer cells, making it easier to permanently eliminate them.

Researchers at Oregon State University used photodynamic therapy to combat ovarian cancer in laboratory animals, using a combination of techniques that achieved complete cancer cell elimination with no re-growth of tumours.

"Cancer cells are very smart. They over express certain proteins, including one called DJ1, that help them survive attack by reactive oxygen species that otherwise might kill them," said study author, Oleh Taratula.

"We believe a key to the success of this therapy is that it takes away those defensive mechanisms," Taratula explained.

Ovarian cancer has a high mortality rate because it often has metastasised into the abdominal cavity before it is discovered.

Surgery and chemotherapy are the traditional approaches to ovarian cancer, but it is very difficult to identify all of the places where a tumour has spread.

"Photodynamic therapy is a different approach that can be used as an adjunct to surgery right during the operation, and appears to be very safe and non-toxic," Taratula said.

In the new approach, a patient is first given a photosensitising compound called phthalocyanine, which produces reactive oxygen that kills cells when they are exposed to near-infrared light.

In addition, a gene therapy is administered that lowers the cellular defence against reactive oxygen species.

Using photodynamic therapy alone, some tumours in laboratory animals began to re-grow after two weeks.

But with the addition of the combinatorial genetic therapy to weaken the cancer cell defences, there was no evidence of cancer recurrence.

"The tumours exposed to a single dose of a combinatorial therapy were completely eradicated from the mice," Taratula concluded.

During the procedures, mice receiving the gene therapy also continued to grow and gain weight, indicating a lack of side effects.

The findings were published in the journal, Nanomedicine: Nanotechnology, Biology and Medicine.