Physicians have used vaccines for centuries to prime the immune system to recognise and combat specific pathogens, such as viruses and bacteria, before they cause illness. As medical science's understanding of the immune system has evolved, new possibilities for vaccine use have emerged.

Today, cancer researchers are exploring vaccines' potential to treat and prevent certain types of cancer, including lung cancer, which continues to be the leading cause of cancer death worldwide despite reduced rates of tobacco use.

What is a cancer vaccine?

Cancer vaccines are a type of immunotherapy, which is a treatment that can use the immune system to destroy cancer cells. They can be preventive or therapeutic. Therapeutic cancer vaccines can treat cancer or reduce cancer recurrence, and physicians are using them for some patients in clinical trials.

“A cancer vaccine is similar to an infectious disease vaccine,” says Dr Knutson. “It's a medicine we give to stimulate the immune system with antigens derived from cancer.” Antigens are any substance that activates an immune response in the body. Dr Knutson says that sometimes, physicians can use these antigens to train the immune system to fight cancer.

The immune system can often recognise cancer cells and destroy them before they can grow and spread. However, cancer cells have mechanisms that help them evade the immune system. Cancer vaccines can help the immune system overcome these mechanisms and attack cancer cells.

A personalised lung cancer vaccine

Each type of cancer varies based on the type of tissue in which it originated, the changes or mutations to the DNA within its cells, and from person to person. Cancer experts sometimes use these individual cancer traits to provide more targeted treatment.

“Because cancer grows so rapidly, there are lots of defects in cancer cells. They don't repair their DNA or RNA well enough, and they accumulate mutations,” says Dr Knutson. DNA contains the genetic instructions for cell function, and RNA conveys those instructions to produce proteins with distinct roles in the cell. Errors in the genetic instructions, called mutations, represent unique targets for therapy.

This targeted approach is the foundation for one of the vaccines in development at Mayo Clinic.

Dr Knutson says Mayo Clinic researchers are exploring two ways to use this vaccine: to prevent recurrence and to reduce cancer spread.

“Even when the tumour is gone, patients have a high risk of their cancer coming back. After the tumour has been removed with conventional therapies, we can train the immune system by stimulating it to prevent that type of cancer from returning,” he says.

In addition to recurrence prevention, Mayo Clinic researchers hope to understand how well the vaccine can reduce cancer spread in advanced lung cancer.

A preventive vaccine for lung cancers with specific genetic characteristics

Mayo Clinic will soon begin investigating the use of a primary prevention vaccine for breast cancer that can also be used to stop some types of lung cancer from developing. Unlike a personalised vaccine, which relies on genetic information from existing cancer, this vaccine uses antigens for some of the common oncogenes overexpressed in breast cancer, which can also be found in some lung cancers. Oncogenes are mutated genes with the potential to cause cancer. When they are overexpressed, they make too many copies of themselves, which can promote cancer growth.

Mayo Clinic will soon begin investigating the use of a primary prevention vaccine for breast cancer that can also be used to stop some types of lung cancer from developing

One antigen included in this vaccine targets human epidermal growth factor receptor 2 (HER2) overexpression. HER2 is responsible for cell growth and division and is overexpressed in about 13% to 20% of non-small cell lung cancers (NSCLC), the most common type of lung cancer. The vaccine also includes several other antigens, including one for MUC1 overexpression found in 80% of NSCLCs.

Dr Knutson says researchers could use this technology to prevent other types of cancer. “HER2 for example, is overexpressed in ovarian cancer. So, if we had a vaccine that prevented breast and lung cancer by targeting HER2, it has the potential to treat or prevent other types of cancer with that overexpression.

“Over the next 20 years, we're going to see some great improvements in how we use vaccines to activate the immune system to suppress cancer development, treat cancer, and prevent it from coming back.”