Cancer Vaccine Unlikely, but do we need one?

May 25, 2016

The genetic diversity between individual tumors makes it difficult to develop a universal cancer vaccine, but there are a lot of alternative treatments.

There’s a simple reason a universal cancer vaccine will probably never be developed.

There are too many types of cancers and they are quite different from each other.

New research published in the journal Genome Medicine provides insights into the challenges of developing such a comprehensive cancer vaccine.

“A broad or semi-universal vaccine capable of targeting many different tumors would be seen by some as the ‘Holy Grail’ of cancer therapy, as it wouldn't involve the time or cost of individualizing treatment,” Dr. Ryan Hartmaier, lead author from Foundation Medicine, said in a press release.

A successful cancer vaccine must recognize the biological molecule in a tumor that is foreign. Then it must turn the immune system against it. To do that, you have to identify the specific target.

The research team performed a comprehensive genetic analysis of more than 60,000 unique tumors. They were searching for sets of genetic alterations that could be targeted to develop a semi-universal cancer vaccine.

Their findings show how unlikely that is.

Where the research stands

“This research reveals how powerful the molecular analysis of tumors has become,” Dr. Mark Faries told Healthline.

Faries is a surgical oncologist. He’s also director of the Donald L. Morton, MD, Melanoma Research Program, and director of Therapeutic Immunology at the John Wayne Cancer Institute at Providence Saint John's Health Center in California.

He said vaccine development alternates between enthusiasm and disappointment.

Hopes were high early on. Then researchers realized the complexity of the relationship between cancer and the immune system.

“Now we have a much better understanding of how the immune system works and its interaction with cancers. There’s a lot of excitement again. Particularly with the development of immune-modulating therapies for cancers that work with the immune system,” said Faries.

“These drugs amplify the immune response. The goal of a vaccine is to create one of those responses,” he added. “There is reason to think a combination of new drugs and vaccines will be particularly effective. But they won’t work for all.”

Faries, who has long been involved in cancer vaccine development trials, expressed doubt about the feasibility of a broad cancer vaccine.

“The new research shows that there’s too much variability from patient to patient and tumor to tumor to devise something that would work for everyone,” he said.

“I’m not sure [a universal cancer vaccine] has ever been anyone’s realistic goal … We can’t even do that with the flu vaccine. I don’t think there will be a single vaccine or pill to treat all cancers. But that’s not a requirement for cancer treatment. We target therapies and vaccines for specific disease,” said Faries.

Don J. Diamond, PhD, told Healthline, “In actuality, this is a refinement of studies that have been published in numerous journals.”

Diamond is chair and professor at the Department of Experimental Therapeutics at City of Hope in California.

“Certainly, a wide variety of mutations can contribute to the development of cancer. Because those mutations are unique, the development of a generalized cancer vaccine to cover all those driver mutations is hard to envision with today’s technology,” Diamond said.

Diamond added there are a few genes, such as TP53, that are associated with a lot of cancers. But there’s another problem in coming up with a vaccine.

“What caused the mutation in the first place may have nothing do with the cancer itself, or the driving force for metastasis. At the time of therapy, the early event may no longer be responsible,” he explained.

Vaccines to treat certain types of cancer

A broad approach aside, vaccines can be used to treat specific types of cancer.

Doctors are already treating some cancers with immune checkpoint modulators. By directing the immune system toward a specific target, a vaccine may prevent recurrence. It may also enhance the effects of other immunotherapies, according to Faries.

“The HER2/neu, the mutant protein most commonly found in breast cancer, led to drugs liketrastuzumab,” said Faries.

“Efforts are underway to develop vaccines against that same protein. Not only in breast cancer, but in gastric and other cancers as well. Possibly across a broader spectrum of cancers that express that particular abnormality.”

Faries cautioned that some of the more advanced vaccine approaches would probably be too expensive to think about in a wide population.

Vaccines to prevent specific cancers

Diamond said there are obstacles to preventive vaccines for specific cancers.

“It’s very hard to predict what type of cancer someone would get, or when they would develop it. You’d have to balance the present with the future, and reward with unknown risks,” he said. “Will the side effect of trying to prevent one cancer be the acceleration of another? We don’t know enough to make those decisions ethically or morally.”

Eliminating viral-based cancers is a much safer strategy, said Diamond.

Faries agrees. “The most successful preventive vaccines are generally those that protect from causative agents,” he said.

An example of this is the hepatitis B vaccine. It helps prevent liver cancer caused by hepatitis. Another example is the HPV vaccine. It helps prevent HPV-related cancers.

Where we go from here

Study results like these can be disappointing.

That doesn’t mean cancer researchers will stop trying.

“There’s a survival benefit to understanding cancer,” said Sandra Brown, MS, LCGC, cancer genetics program manager at the Center for Cancer Prevention and Treatment at St. Joseph Hospital in California.

“Cancer is basically evolution on steroids,” she wrote in an email to Healthline.

“We consciously create a healthy environment, although aging alone can lead to the accumulation of mutations necessary for tumorigenesis. Then we treat to create a hostile environment while the cancer may evolve multiple clonal pathways in an attempt to reproduce successfully within that environment.”

She continued, “Perhaps often we win and the tumor dies. But there is always the possibility that lethally resistant random mutations will occur anytime in tumorigenesis, particularly during treatment. Genetically modified humans may someday be immune to tumorigenesis, or attenuated viruses may someday perfectly recognize tumor cells for targeted destruction.”

Preventing cancer now

Broad therapeutic or preventive cancer vaccines won’t happen anytime soon.

This makes other methods of cancer prevention that much more important.

The first step, according to Faries, is understanding the cause.

We already know what causes some cancers. But prevention is still a problem, he explained. That’s because you have to apply this knowledge to a wide population who might not be intent on following through.

“Smoking is a classic example. You can tell people until you’re blue in the face that smoking kills. But they continue to smoke,” said Faries.

His suggestion is that people should consider their family history and other risk factors. If you’re more likely to get a certain type of cancer, learn the prevention measures.

Diamond has a few words of advice for anyone trying to lower their cancer risk.

Protect yourself from the sun, don’t smoke, manage your weight, and don’t eat charcoaled foods.

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