Experimental cancer vaccine clears four in 10 pancreatic tumors and prevents disease from returning, study on mice shows

An experimental cancer vaccine has been shown to treat four out of 10 pancreatic tumors – in a ray of hope for patients with the aggressive disease.

In a study on mice, the shot ‘cleared’ 43 percent of pancreatic tumors and prevented the cancers from returning when they relapsed. 

The vaccine uses a weakened food poisoning bug to stimulate an immune response and contains a piece of the recipient’s tumor to train their body to fight their own cancer.

While the study is preliminary and on mice, the team from the University of Massachusetts hopes to start human trials in the coming years.

If approved, it could be a lifeline for patients diagnosed with pancreatic cancer, a situation that is currently a death sentence in the US. Just 8.5 percent of Americans survive longer than five years.

Relative to other cancers, pancreatic cancer is quite rare. It is the third leading cause of cancer death in the US, claiming 50,550 lives each year.

It is hard to find early because the pancreas is deep inside the body, so tumors cannot be seen or felt by healthcare providers during routine physical exams. 

Once found, it is also hard to treat because tumors are often surrounded by important tissue, making it tricky for treatments to reach the cancer directly without damaging the tissue.

Initially, the research team will use the vaccine to treat liver cancer, followed by pancreatic cancer.

Liver cancer is one of the leading causes of death in the world — accounting for more than 700,000 deaths every year.

The new vaccine is made of a molecule taken from inside a cancer cell and wrapped into a protein from a chicken egg called ovalbumin.

Vaccines for yellow fever, the flu, MMR and rabies contain small amounts of egg protein because they are grown in chicken eggs.

The molecule and protein are delivered inside a genetically altered salmonella bacteria, which is non-toxic and releases the vaccine.

When injected into the blood, the weakened salmonella bacteria sets off an immune response. 

A type of white blood cell called T cells is also triggered by the protein, which trains the immune system to attack future cancer cells.

The team tested the treatment on mice with pancreatic cancer.

Neil Forbes, professor of chemical engineering and senior author of the paper, said: ‘We had complete cure in three out of seven of the pancreatic mice models. We’re really excited about that; it dramatically extended survival.’

Then, the researchers tried to re-introduce pancreatic tumors into the vaccinated mice.

‘None of the tumors grew, meaning that the mice had developed an immunity, not just to the ovalbumin but to the cancer itself,’ Professor Forbes said.

‘The immune system has learned that the tumor is an immunogenic. I’m doing further work to figure out how that’s actually happening,’ he added.

The team plans to seek FDA approval to get clinical trials off the ground within a few years.

Before trials can start, they need to repeat the experiments on other animals and make sure the salmonella strain is safe to use in humans.

Professor Forbes, whose grandfather died of prostate cancer, said: ‘This is not just an academic exercise. I’m really trying to make a cancer therapy.’ 

The study was published last week in the journal Frontiers in Immunology.

In earlier research, the team demonstrated that injecting the altered salmonella into the blood was effective in treating liver tumors in mice. 

Professor Forbes said the new immunotherapy has the ‘potential to be effective in a broad range of cancer patients.’