Increasing immunotherapy killing of prostate cancer cells

The immune system protects us by recognising and attacking things which might make us ill, such as viruses, bacteria, or unhealthy cells (like cancer cells!). Your immune system is made up of a complex system of cells, known as immune cells, and special proteins that the cells interact with. Immune cells, or white blood cells, are the key players in your immune system. They are constantly moving through your body on the patrol for things they don’t recognise. When they find a target, they activate, and begin to multiply and send signals out to other immune cells to do the same. This is how the immune system kills targets and keeps you healthy.

Immunotherapy aims to train the body’s own immune system to become better at finding and destroying tumour cells. So far, however, this approach has had limited success in prostate cancer. This team of PCR researchers wanted to investigate if they could overcome this issue by administering their immunotherapy directly into the tumour.

The team wanted to know which immune cells were responsible for killing the prostate cancer cells. They had previously found that there are two main types of immune cells activated by IL-15 in the presence of prostate cancer cells: NK cells and CD8 T cells. Both these cells are involved directly in killing cancer cells.

Figure 4A shows the increase in numbers of activated NK cells when they are mixed with different prostate cancer cells with IL-15 present, or with a combination of IL-15 & STING agonist, compared with a control.

Adapted from: Esteves, A.M., Papaevangelou, E., Dasgupta, P. and Galustian, C., 2021. Combination of Interleukin-15 with a STING agonist, ADU-S100 analog: a potential immunotherapy for prostate cancer. Frontiers in oncology, 11. https://dx.doi.org/10.3389%2Ffonc.2021.621550

They measured markers of NK cell activation and saw that they were increased when both IL-15 and the STING agonist were used. This shows that more NK cells were switched on and producing chemicals that kill cancer cells. Christine’s group also saw a lack of cancer cells being killed when NK cells were removed from the experiment, which supports their finding.