Once inside, the zinc then put the brakes on further activity in the NF-kB pathway, slowing down the immune response and limiting the amount of inflammation, the study, in Cell Reports, indicated.

BBC: Zinc 'keeps immune system in check'

What scientists have been looking for are proteins which are found on the tumour cells - but not on every other cell of the body - which provoke some sort of immune response.

BBC: Find boosts cancer vaccine hopes

The team, at the Gray Institute for Radiation Oncology and Biology at Oxford University, were looking for a protein, called gamma-H2AX, which is produced in response to damaged DNA. This tends to be one of the first steps on the road to a cell becoming cancerous.

BBC: One test may 'find many cancers'

Researchers can only use dead cells or pieces of a cell and can only test for one response at a time, such as enzyme activity or the binding of a compound to a receptor.

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