Crosstalk Between Tumour and Draining Lymph Nodes and its Impact on Triple-Negative Breast Cancer

The human body contains ~500 bean-shaped immune organs, so-called lymph nodes, as part of the lymphatic system. When lymph nodes sense something foreign, such as cancer cells, it undergoes structural changes, signalling a location where new immune cells are produced. These patches are called germinal centres. Some immune cells derived from these germinal centres, called plasma cells, will produce markers called immunoglobulins, which they will use to label foreign molecules. This labelling tactic allows killer immune cells to easily track down and destroy cancer cells. Another type of immune cell, memory B cells, produced in the germinal centres helps the immune system to remember which molecules are foreign. So, if in future our immune system encounters these foreign molecules again, it can then act immediately to produce labels and eliminate the invader much more rapidly.

We found that the appearance of germinal centres in lymph nodes can help to identify breast cancer patients who will overall live longer. We now know that these lymph node changes carry important information especially in a subgroup of breast cancer patients with very aggressive cancers and who develop secondary cancer in distant organs soon after initial diagnosis. Our unpublished data indicate that both plasma and memory B cells might be involved at the tumour and in lymph nodes. In parallel, we have started work with mouse models in our laboratories where we found that tumour growth causes germinal center formation. This gives us now the opportunity to dissect how the tumour growth is dependent on the appearance of germinal centres in lymph nodes and whether there is a certain order of events necessary to slow down tumour growth in these high-risk patients.

We are a multi-disciplinary team of clinicians, wet-laboratory scientists and computational scientists with long-standing collaboration. In this proposal, we will leverage our expertise in combing biology, histopathology, imaging and computer programming in translational research. We will use a combination of approaches, including novel technologies called "spatial transcriptomics" which will help us to understand which molecules are present in these germinal centres and at the tumour. By using pre-clinical mouse models representative of breast cancers we will interrogate the direct role of memory B cells and plasma cells in cancer. By expanding on mouse models and utilising tissue from cancer and lymph nodes from patients who received chemotherapy before surgery, we will be able to assess the importance of our findings and test response to chemotherapy.

In summary, our work will not only contribute to understanding for the first time the role of germinal centers in lymph nodes and their related immune response in the tumour microenvironment, but also may have a major impact in predicting who might benefit from current standard-of-care therapies, and in future from the immune therapies that are currently emerging in the clinic.

The presence and extent of lymph node (LN) metastasis is associated with shorter disease-free and overall survival in triple negative breast cancer, but LNs, as well as being typically the first site of seeding of many solid tumours, also serve as immunological hubs between the tumour and the patient's systemic immunity. Work from our team showed for the first time that in triple negative breast cancer patients with low tumour infiltrating lymphocytes (TILs), time to progression of disease was prolonged when their LNs displayed formation of germinal centers. Germinal centers represent locations within LNs where different B cell populations are produced for effective adaptive immune responses.

These findings underscore our hypothesis that these patients display activation of the immune system at their LNs and these play a critical role in the immune response to the tumour. Thus, our research raises awareness of the biological and translational value to assess LNs above and beyond the presence and size of cancer cells deposits, next to the assessment of tumour infiltrating lymphocytes.

Here, we propose to use a combination of approaches, including spatial transcriptomics, single cell RNA-seq, BCR-seq, imaging and mouse models to: 1) dissect the cellular, molecular and spatial organisation similarities between tumour draining (td)-LNs, TILs and TLSs; 2) characterise td-LNs GCs properties, function and impact in the context of therapy; 3) Determine the signals mediating the crosstalk between the tumour and td-LNs. Our work will provide the first insights into the functional role of distinct B cells at the tumour and in LNs, potentially uncovering targets to develop therapeutic strategies for high-risk triple negative breast cancer patients.