Scientists say cancer vaccine 'blocks' tumour growth if given 'at right time'

A cancer vaccine could block tumour progression if given at an early stage of the treatment cycle, a new scientific study has found.

The vaccine had little success in clinical trials for patients with advanced tumours but the new research concluded that it could achieve its intended result if administered earlier - when the lesions are at an early stage.

The study by Vanderbilt University, in Nashville, Tennessee, differed from most cancer vaccine studies, which have focused on patients with advanced tumours. Results of the research, published in the Journal for ImmunoTherapy of Cancer, revealed that tumour-specific T cell populations are present in mice with early-stage lesions and can be therapeutically exploited by vaccination, ecancer reports. Mice with advanced tumours do not retain these cells, the study found.

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T cells, a type of white blood cell, develop from stem cells in the bone marrow and are part of the immune system. They help protect the body from infection and may help fight cancer.

With the development and widespread use of mRNA vaccines for COVID-19, there is increasing excitement about the use of personalised vaccines to treat and prevent cancer. The new study’s senior author Mary Philip, MD, PhD, associate director of the Vanderbilt Institute for Infection, Immunology and Inflammation, said the findings supported further vaccine investigation to make long-term, progression-free survival a reality for more cancer patients.

“Our study suggests that the timing of vaccination is important,” said Philip. “A unique feature of our study is that these mice are at high, essentially 100% risk of developing cancers, so the fact that a single immunisation at the right time can give lifelong protection is pretty striking.

“There are not many cancer studies where mice have been followed so long after vaccination and remain tumour-free for two years.”

The study also revealed that early treatment with a cancer vaccine blocked tumour progression when immune checkpoint blockade (ICB) therapies did not work. ICB therapies are approved for treating advanced cancers but only a subset of patients with certain types of cancer achieve durable remission with them.

“ICB works by taking the brakes off T cells, but if the T cells have never been properly activated, they are like cars without gas, and ICB doesn’t work,” Philip said. “The vaccination boosts the T cells into a functional state so that they can eliminate early cancer cells.”

Philip and colleagues investigated a vaccine previously tested in human clinical trials for advanced cancers. This vaccine uses a gramme-positive intracellular bacterium that induces strong CD4 and CD8 T cell responses.

All mice that received vaccination at an early stage remained tumour free. However, the vaccine failed to slow liver tumour progression when administered at a later point (age 100 days).