PROJECT SUMMARY/ABSTRACT
Breast cancer is the leading cause of cancer-related death in women. Triple negative breast cancer (TNBC) has
the poorest prognosis of all major subtypes of breast cancer. The anticipated success of immunotherapy has not
been seen in TNBC. The role of T-cells in TNBC and immunotherapy has been well-studied but the role of tumor-
infiltrating B-cells (TIL-B) is less well-known. Present in up to 60% of breast cancers, TIL-B are associated with
improved prognosis and response to chemotherapy. Evidence suggests that TIL-B respond directly to tumor
antigens in TNBC. Utilizing single-cell sequencing of tumor-infiltrating lymphocytes in TNBC, we have identified
high expression of a low diversity of paired heavy and light chain B-cell receptor segments which is definitive
evidence of clonal selection, suggesting B-cells have undergone affinity maturation and can recognize antigens.
In order to clone antibodies and identify their targets in TNBC, we have successfully sequenced the B-cell
receptors of the most abundant B-cell clones we have identified thus far. Pre-clinical data also suggests an
important role for B-cell antibody production in immunotherapy efficacy. Based on these data, we hypothesize
that B-cells in TNBC recognize tumor-associated antigens and produce biologically relevant tumor-specific
antibodies. To test our hypothesis, we propose the following aims: 1) Discover the role of clonally selected B-
cells/plasmablasts in human TNBC, 2) Characterize the endogenous antibody response against TNBC, and 3)
Evaluate the impact of immune checkpoint inhibition on B-cell receptor diversity and phenotype in human TNBC.
Successful execution of these aims will support a role for B-cells in the anti-tumor immune response and lay the
foundation for development of novel B-cell based therapies and/or biomarkers in TNBC. In addition to advancing
scientific knowledge, this proposal provides training to a physician-scientist. Dr. Downs-Canner is a practicing
breast-surgical oncologist with a background in cellular immunology. Her long-term goal is to combine her clinical
and research expertise to develop an independently-funded research program focused on immunotherapy in
breast cancer. She benefits from two well-established mentors with track records of training clinician-scientists
and an extremely supportive research and practice environment. In order to achieve her long-term goals, the
candidate's proposal includes a structured career development plan and training in: 1) bioinformatics 2) antibody
cloning techniques and development of expertise in: 1) B-cell biology and 2) increasingly complex hypothesis
driven experimental design, execution, and analysis. The proposed plan includes mentored experiential learning,
course work and conference participation, frequent mentor meetings and a gradual increase in research
independence. At the completion of the award period, the candidate will be prepared to apply for independent
funding for her research program.