Vaccine for skin cancer on the horizon?

Scientists have created a vaccine that has successfully eradicated skin cancer in some mice, the Mayo Clinic reported Monday. Results from early studies have shown that 60 percent of mice with melanoma were cured in fewer than three months with minimal side effects, thanks to the treatment.

The vaccine was made up of a combination of human DNA from melanoma cells and a cousin of the rabies virus called vesicular stomatitis virus (VSV).  Known as cancer immunotherapy, the treatment used the genetically-engineered version of VSV, which is symptomless in humans, to help target the cancer genes in the body.

Cancer can hide from a normal immune system, but the introduction of an outside virus can help highlight the cancer cells. When the proteins from melanoma skin cancer cells were expressed through the VSV, the immune system was then able to ‘see’ the cancer cells and create T-cell antibodies to target and destroy them.

The new technique may help identify an entirely new set of genes that can stimulate the immune system to reject cancer cells, according to researchers.

“One of the major problems in patients with melanoma and several other types of cancer is that cancer grows over long periods of time, and the immune system becomes subverted by the cancer – so it no longer sees cancer cells as something that should be rejected or fought off,” Dr. Richard Vile, a Mayo Clinic researcher in the Department of Molecular Medicine and a coauthor of the study, told

“In contrast, with viruses or bacteria, the immune system works very well against invading agents - so by associating the proteins from cancer cells and expressing them through viruses, the immune system sees the cancer cells as foreign and invading pathogens,” Vile explained  --  adding that the treatment essentially re-educated the immune system, rather than altering the existing cancer in the body.

“We didn’t have to get to the tumor itself,” Vile said.  “One of the attractions of using the immune system is that it can patrol the whole body to find metastatic disease in the liver, lung and other areas, as opposed to merely being a local therapy.”

The treatment even worked in mice with systemic disease, where the cancer had spread throughout their bodies, according to Vile.

This latest research adds to other successes with experimental cancer vaccines, including a current clinical trial with vesicular stomatitis vaccines for liver cancer.  Researchers also hope to test vaccines for more aggressive cancers, such as lung, brain and pancreatic cancers.

"I do believe we can create vaccines that will knock them off one by one," Vile said. "By vaccinating against multiple proteins at once, we hope that we will be able to treat both the primary tumor and also protect against recurrence."

The next step, he said, was to narrow down which proteins were key in the treatment, and then move toward an FDA-approved clinical trial in humans, which he and his colleagues hope will happen within the next two years.

If proven effective, in its first stage, the vaccine would hypothetically be used in conjunction with existing cancer treatments such as chemotherapy and radiation.

“Hypothetically, the chemotherapy or radiation would be used with the aim of reducing the size of tumors, so the immune system would have a better shot of clearing it,” Vile explained.  “In time, we would hope that this vaccine would be able to treat small tumors before they became large and dangerous.”

The study was published in the journal Nature Biotechnology.