Washington: Scientists have developed flat oblong-shaped artificial particles that can be administered directly into a patient to activate the immune system to destroy cancer cells.

In the study, researchers exploited the well-known immune system interaction between antigen-presenting cells (APC) and T-cells.

APCs “swallow” invaders and then display on their surfaces chewed-up protein pieces from the invaders along with molecular “danger signals.”

When circulating T-cells interact with APCs, they learn that those proteins come from an enemy, so that if the T-cells see those proteins again, they divide rapidly to create an army that attacks and kills the invaders.

To enhance this natural process, several laboratories, have made “artificial APCs” – tiny inanimate spheres “decorated” with pieces of tumour proteins and danger signals.

These are often used in immunotherapy techniques in which immune cells are collected from a cancer patient and mixed with the artificial APCs.

When they interact with the patient’s T-cells, the T-cells are activated, learn to recognise the tumour cell proteins and multiply over the course of several days. The immune cells can then be transferred back into the patient to seek out and kill cancer cells.

The cell-based technique has had limited success and poses risks due to growing the cells outside the body, said Jordan Green, assistant professor of biomedical engineering at the Johns Hopkins University School of Medicine.

Green and colleagues decided to improve the technique by making biodegradable artificial APCs that could be administered directly into a patient and that would better mimic the interactions of natural APCs with T-cells.

They also flattened the particles so they might mimic this interaction better than spheres and activate the T-cells more effectively.

When the particles were injected into mice with skin cancer, the T-cells that interacted with the elongated artificial APCs, versus spherical ones, were also more successful at killing tumour cells.

Jonathan Schneck, professor of pathology, medicine and oncology said that tumours in mice that were treated with round particles reduced tumour growth by half, while elongated particles reduced tumour growth by three-quarters.

Over the course of a one-month trial, 25 per cent of the mice with skin cancer being treated with elongated particles survived, while none of the mice in the other treatment groups did, he said.

“This adds an entirely new dimension to studying cellular interactions and developing new artificial APCs. Now that we know that shape matters, scientists and engineers can add this parameter to their studies,” said Green.

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