Research uncovers potential new target for breast cancer therapy

Targeting CD1d altered immune cells slowed tumour growth and improved immunotherapy responses in mouse models of breast cancer, researchers found.

The findings suggest blocking the molecule could make the environment around breast tumours more favourable to anti-cancer immune responses.

Further work is needed to understand how these immune changes occur and how the approach could be safely used in patients.

Researchers from King’s College London, the Francis Crick Institute and University College London investigated how immune cells inside breast tumours influence cancer growth.

They focused on myeloid cells, a group of immune cells found in large numbers within tumours that can either support an immune attack against cancer or contribute to tumour growth and immune evasion.

The team examined CD1d, a molecule found on the surface of myeloid and other immune and tissue cells that helps regulate immune responses.

When CD1d was genetically removed from cells in a mouse model of breast cancer, the mice were more resistant to tumour growth. Researchers also saw changes in myeloid cell populations, including increased activity among cells that can help attack cancer.

The team then blocked CD1d using an antibody and again observed changes in myeloid cells and slower tumour growth. Blocking CD1d also improved responses to immunotherapy in the mouse model.

Researchers used single-cell RNA sequencing, a technique that examines gene activity in individual cells, to investigate the immune changes in more detail.

They identified a population of myeloid cells called monocytes that expressed genes associated with inflammation, an important part of the immune response. These cells were particularly important in restricting tumour growth in the mouse models.

A similar pattern of gene activity was identified in data from human breast cancer tumours. Its presence in myeloid cells was associated with positive responses to immunotherapy in breast cancer patients.

However, the findings in people were based on gene expression data and did not test CD1d-targeting treatment in patients.

Professor Patricia Barral, professor of immunobiology at King’s College London and senior author of the study, said: “Many breast cancers do not respond well to current immunotherapies.

“Our findings reveal a previously unrecognised mechanism by which immune cells within tumours are regulated.

“While CD1d is best known for helping immune cells recognise lipid molecules, we found that it also plays a role in shaping the behaviour of myeloid cells within tumours.

“These findings suggest that targeting the immune cells that surround and support tumours could boost anti-cancer immunity and potentially improve treatment responses in the future.”

Researchers now plan to investigate how the immune changes occur and how they can be safely harnessed in patients.

They also want to examine whether targeting CD1d could enhance existing treatments and influence treatment responses in different cancer types.

The work was supported by UKRI BBSRC, Breast Cancer Now and the Cancer Research UK City of London Centre.