Injecting immune cell stimulants directly into a tumour could help the immune system spot and attack cancer cells, according to new research* in mice.
Writing in the journal Nature Medicine US researchers describe combining a series of different techniques with radiotherapy to help boost the immune system’s response in lab tests.
They say the result was a chain reaction of immune activity that teaches immune cells to attack the tumour in mice, much like how a vaccine shows parts of a virus to the immune system so it can remember and attack infected cells.
The researchers have also begun testing parts of the treatment in patients with advanced lymphoma. In a small clinical trial, 11 patients had injections of the two immune stimulants and received radiotherapy. They were not given the existing immunotherapy as part of the combination. Early results suggest that the treatment was safe and stimulated immune cells to mature and become more active.
It’s hoped the immune boost could transform certain tumours into “cancer vaccine factories” in what experts say could be part of a new approach to immunotherapy.
The multi-stage treatment combines the immune stimulant injections with radiotherapy to make cancer cells more visible to the immune system. In studies in mice the researchers also added an immunotherapy drug - known as a checkpoint inhibitor – that further harnesses the immune system’s ability to kill tumour cells.
The combination treatment starts by injecting a series of stimulants directly into the tumour, with the first stimulants recruiting important immune cells called dendritic cells. The second stimulants then activate these dendritic cells, which instruct T cells, to target and kill tumour cells. The combination led to long-term responses in eight in 10 mice with lymphoma.
Dr Joshua Brody, who led the study at the Icahn School of Medicine at Mount Sinai, said the findings had “broad implications”.
“This method could also increase the success of other immunotherapies such as checkpoint blockade,” he said.
Dr Edd James, a Cancer Research UK-funded immunology expert at the University of Southampton, said that while there was still more work to do he called the research “interesting and impressive.”
“The approach itself is not entirely new, but the idea of combining these different approaches to activate the immune system is,” he added.
Dr James said the process, called "in-situ vaccination", showed “impressive results” in the US team’s lab models of lymphoma. But he added that further work was still needed to understand how effective the approach might be in people.
“There are some questions around how durable these responses will be, and whether this will work in all patients, but these are encouraging results and highlight an alternative approach to immunotherapy treatments,” he said.
*Hammerich L, Marron TU, Upadhyay R, et al. Systemic clinical tumor regressions and potentiation of PD1 blockade with in situ vaccination. Nature Medicine(2019), DOI:10.1038/s41591-019-0410-x