Surprise discovery reveals severe Covid infections may shrink cancer tumours

Mice with various types of advanced stage 4 cancers, including melanoma, lung, breast and colon cancer, saw their tumours shrink after experiencing a severe COVID infection

A fascinating new study has found severe Covid infections may shrink cancerous tumours.

The findings, published in the Journal of Clinical Investigation, used mice to study complex interactions between the immune system and cancer cells. Scientists focused on a specific white blood cell called monocytes - which play a key role in the body's fight against viruses and other threats.

In cancer patients, these monocytes can sometimes turn into cancer-friendly cells that protect the tumour from the immune system. Researchers found that this special anti-cancer type of monocyte was induced when the mice were given a drug that mimicked the immune response to a severe COVID infection.

The mice had various types of advanced stage 4 cancers, including melanoma, lung, breast and colon cancer, and all saw their tumours shrink after having experienced a severe COVID infection. While regular monocytes can be converted by tumours into protective cells, the special induced monocytes retained their cancer-fighting properties.

The team found that these cells could travel to tumour sites - something most immune cells cannot do - and then trigger natural killer cells. These killer cells then attack the cancer cells, causing the tumours to shrink.

What emerged from the study was that a severe bout of COVID prompts the body to generate a distinct kind of monocyte with unique anti-cancer abilities. These "induced" monocytes, while initially primed to combat the virus, also possess the capacity to attack cancer cells.

The scientists identified that these induced monocytes are equipped with a unique receptor that has a high affinity for a particular sequence found in COVID RNA. Ankit Bharat, one of the scientists involved in this work from Northwestern University in Chicago explained the relationship using a lock-and-key analogy: "If the monocyte was a lock, and the COVID RNA was a key, then COVID RNA is the perfect fit."

The new finding is especially exciting as it offers a new approach to fighting cancer that doesn't rely on T cells, which several immunotherapy treatments focus on - but scientists have stressed that the findings do not mean people should actively try to catch COVID.