Australian scientists have discovered how the immune system can control melanoma, a mechanism which could be used to enhance cancer treatments.

Published today in Nature, Peter Doherty Institute for Infection and Immunity (Doherty Institute) and Telethon Kids Institute researchers investigated the role of a particular immune cell, tissue-resident memory T (TRM) cells, in controlling melanoma.

TRM cells were able to control the tumour in the mice for the life of the animal, which is likely to equate to decades of protection in humans.

University of Melbourne PhD student, Simone Park from the Doherty Institute, created an imaging model to study TRM cells’ and melanoma in a mouse model.

“Using a special microscope, we could see individual melanoma cells sitting in the skin of the mouse, and could watch the T cells move through the skin, find the melanoma cells and control the growth of those cells,” Ms Park explained.

One of the main issues for cancer patients is that there is always a risk that the tumour can come back years later, after surgery or chemotherapy.

Previous research has shown that small numbers of cancer cells persist in the body after treatment and that the immune system probably keeps the cancer cells under control but this study in mice could study the immune system directly. This is work that could never be done in people.

“I was able to see through moving images that these TRM cells are important for maintaining the control of the tumour cells; if you remove the TRM cells you have a break in that control and the cancer can start to grow back again,” Ms Park said.

“If you could make more of these TRM cells through immunotherapies, or enhance the activity of those that are already there in some way, you could boost anti-tumour immunity.”

Senior author on the paper, University of Melbourne Associate Professor Thomas Gebhardt, Laboratory Head at the Doherty Institute, said an increase of TRM cells has already been associated with better outcomes in cancer patients, but the way they work to suppress tumours has remained unknown.

“The principal of cutting-edge immunotherapies currently in clinical practise is that they generate a T-cell response. But if we can hone in on one type of T-cell - the TRM cells specifically, we could have an even bigger impact on stopping cancers from coming back,” Associate Professor Gebhardt said.

“We now have a much better understanding of which T-cells are important in controlling skin cancers and how those cells are working but there is still much more work to do to make these cells work even better,” Associate Professor Gebhardt said.