Relapse after immunotherapy for cancer explained by tumour cells hiding within other cells so avoiding destruction
Cancer cells are masters of evasion, finding innovative ways to survive treatments. Researchers now investigate why tumours return after immunotherapy, a treatment using the immune system’s killer T-cells which appear to effectively target and then kill cancer cells by injecting them with toxic granules. In a mouse cancer model, where tumours have returned after initial immunotherapy, scanning electron microscopy revealed that cancer cells hid within each other – a process called cell-in-cell formation – to avoid destruction. Exposing cancer cells from the tumours, to different immune cells in a dish revealed that killer T-cells specifically triggered cell-in-cell formation, as captured here using live-cell imaging. Injecting mice with drugs that blocked a molecular pathway activated by the killer T-cell attack before cell-in-cell formation, increased the effectiveness of subsequent immunotherapy. This reveals an important cancer mechanism for evading immunotherapy and a starting point to counter it.
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