A group of researchers from the National Cancer Center and other entities have worked out a method to sharply curb the growth of breast cancer by inhibiting a gene that makes cancerous cells resistant to a chemotherapy drug.

The method has proven effective in an experiment with mice and will be announced at a meeting of the Japanese Cancer Association in Yokohama on Sept. 30, the researchers said. It could contribute to developing a treatment to surmount drug resistance, which affects the majority of breast-cancer patients, the researchers said.

The group, including Takahiro Ochiya, head of the section for studies on metastasis at the center's Research Institute in Tokyo, found that a gene called RPN2 regulates the working of a protein that pumps out a chemotherapy drug from cancerous cells.

They inhibited RPN2 by using a technique called RNA interference in a mouse transplanted with breast cancer found resistant to a chemotherapy drug. The drug, docetaxel, proved to be effective in fighting cancer in the mouse, reducing a tumor with a diameter of 5 mm to less than 1 mm in seven days.

"After confirming the safety for humans, we would like to aim at establishing a treatment for various forms of cancer," Ochiya said. "We can expect a merit of alleviating the side effects of an anticancer drug by reducing its dose, and in some patients, surgery may become unnecessary."