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Women suffering from breast cancer.

The two diseases may appear unrelated, but the Princeton-based biotech company Advaxis Inc. is eager to exploit the connection: Dogs with bone cancer express the same antigen — a harmful substance that causes the body to produce antibodies — as women with certain forms of breast cancer.

Encouraging data with the canine experiment is among several milestones that have Advaxis, which is also developing therapies to treat cancers associated with human papillomavirus, excited about its prospects. The early-stage company’s technology is based on stimulating the body’s own immune system to fight cancer, part of a growing field called immunotherapy.

“We’ve built product candidates for multiple different types of cancers,” Advaxis CEO Daniel O’Connor said. “That’s the real colossal opportunity.”

The ongoing canine experiment, funded by Advaxis and conducted at the University of Pennsylvania School of Veterinary Medicine, was the brainchild of professor Nicola Mason. It is based on an Advaxis immunotherapy designed to harness the immune system to attack cancer cells that express the HER-2/neu molecule, a genetic marker also expressed in breast cancer.

“She scientifically reasoned that dogs with bone cancer express the same antigen; therefore, she wanted to use our immunotherapy to see if it could have an effect on treating dogs with bone cancer,” O’Connor said.

Results showed the pet dogs that received the immunotherapy are living significantly longer than dogs with owners who chose not to participate in the study.

Of 11 dogs enrolled, about 80 percent lived at least 600 days. Dogs with osteosarcoma receiving standard treatment, including chemotherapy, have a median survival rate of nine months to a year. The lead bulldog treated in the Penn study has survived more than 650 days.

Based on that success, Advaxis plans to explore the use of its immunotherapy to treat dogs with canine lymphoma, which affects up to 5 million dogs, compared with the 20,000 dogs a year in the United States that develop bone cancer.

“We are not a veterinary company, but we will opportunistically license that technology so that it can be fully exploited and explored in the hands of a veterinarian medicine company,” O’Connor said.