The common flu shot could do more than just protect you from the flu, say researchers and scientists from Rush University Medical Center in the United States.
Changing the microenvironment in which tumours grow can kickstart your immune system’s response to fight them.
Most cancer patients have tumours that are ‘cold’. Cold tumours are those that don’t contain many immune cells or have cells that oppress the immune system’s ability to fight them.
Changing tumours from cold to hot makes them more recognisable by your immune system and easier to fight, increasing your chance of survival as a result.
Finding a stable way to effect this change in environment has long been a goal in medical research.
A new study, published in Proceedings of the National Academy of Sciences, revealed that injecting tumours with influenza vaccines and seasonal flu shots, can turn cold tumours to hot, which could lead to an immunotherapy to treat cancer.
Usually, immunotherapies consist of live pathogens (disease-causing organisms), but they work only on a limited number of patients and cancer types.
“We wanted to understand how our strong immune responses against pathogens like influenza and their components could improve our much weaker immune response against some tumours,” said senior study author Assistant Professor Andrew Zloza.
The study started when scientists noticed how people with lung cancer who also had influenza actually lived longer than lung cancer patients with no influenza.
They found similar results in mice with tumours and influenza infection in the lung.
“However, there are many factors we do not understand about live infections, and this effect does not repeat in tumours where influenza infections do not naturally occur, like skin,” said Ass. Prof. Zloza.
So, researchers inactivated the influenza virus, essentially creating a flu vaccine, which they injected directly into a melanoma. The injection made the tumour hot, leading to an increase in the cells that recognise and kill tumour cells, which led to reduced growth of the injected tumour. It also led to reduced growth of a second tumour that had not been injected on the other side of the mouse.
Similar results have been achieved in a mouse model of metastatic triple-negative breast cancer, where both primary tumour growth and the natural spread of the breast tumour to the lungs were reduced after injection only into the primary tumour.
“Based on this result, we hope that in patients, injecting one tumour with an influenza vaccine will lead to immune responses in their other tumours as well,” said Ass. Prof. Zloza.
“Our successes with a flu vaccine that we created made us wonder if seasonal flu vaccines that are already FDA-approved could be repurposed as treatments for cancer. Since these have been used in millions of people and have already been shown to be safe, we thought using flu shots to treat cancer could be brought to patients quickly.”
To determine if similar results could be obtained with tumours from patients, researchers developed a mouse model in which they implanted a piece of tumour and immune cells from a patient with cancer into a mouse that does not have a functioning immune system of its own.
“Such transplant allows us to utilise patient-grade drugs in a living system. This is as close as we can get to testing something ahead of a clinical trial,” said Ass. Prof. Zloza.
The flu shot into these patient-derived tumours also caused them to shrink, while untreated tumours continued to grow.
Researchers have also combined this treatment with immunotherapy and found even greater reductions in tumour growth.
“These results propose that eventually both patients who respond and who do not respond to other immunotherapies might benefit from the injection of influenza vaccines into the tumour, and it may increase the small proportion of patients that are now long-term responders to immunotherapies,” said Ass. Prof. Zloza.
“Since humans and mice are about 95 per cent genetically identical, the hope is that this approach will work in patients. The next step planned is to conduct clinical trials to test various factors.”
Do you already get a flu shot each year? Will this research add extra incentive to keep this up?
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