"When we use these two agents together, we see the elimination of tumors all over the body," said lead author Ronald Levy, MD, professor of oncology, whose lab developed Rituximab, a widely-used form of chemotherapy.
"This approach bypasses the need to identify tumour-specific immune targets and doesn't require wholesale activation of the immune system or customization of a patient's immune cells."
According to the team, the shot could work for many different types of cancer.
It holds a unique place in the field of immunotherapy.
While some approaches stimulate the entire immune system, others target certain areas to block the cancer from straying, and others (like the newly-approved CAR T-cell therapy) removed immune cells from the body to genetically-engineer them.
All have been hailed a success.
But all have caveats, be they arduous to prepare, lengthy to administer, or excruciating in their side effects.
'All of these immunotherapy advances are changing medical practice,' Levy said.
'Our approach uses a one-time application of very small amounts of two agents to stimulate the immune cells only within the tumour itself. In the mice, we saw amazing, bodywide effects, including the elimination of tumours all over the animal.'
The method works to reactivate the cancer-specific T cells by injecting microgram (a millionth of a gram) amounts of two agents directly into the tumor site.
The first, a short stretch of DNA, works with nearby immune cells to heighten the expression of an activating receptor on the surface of the T cells.
The second, an antibody that binds to the receptor, activates the T cells to attack the cancer cells.
By injecting it direct into the tumour, it is specifically training T cells which already recognize cancer because they are already inside it.
"This is a very targeted approach," Levy said.
"Only the tumour that shares the protein targets displayed by the treated site is affected. We're attacking specific targets without having to identify exactly what proteins the T cells are recognizing."
For the trial, Levy plans to recruit 15 patients with low-grade lymphoma.
If successful, Levy believes the treatment could be useful for many tumour types.
Down the line, he believes oncologists could inject both into solid tumours in humans before surgery as a way to prevent recurrence from stray tumours that spread but weren't detected.
"I don't think there's a limit to the type of tumour we could potentially treat, as long as it has been infiltrated by the immune system," Levy said.
