Sunday, May 18, 2025
5/18/2025
Elucidate the role of B/T cell-enriched immune aggregates in immune surveillance against TNBC - It is widely believed that immune surveillance destroys precursors of cancers before they turn malignant, although the detailed mechanisms remain elusive. Furthermore, the fact that many cancers eventually form implies a failure of immune surveillance. Therefore, to harness the power of immune surveillance to fight cancer, one must first understand how it works. To study immune surveillance, one would need to study the immune responses during pre-malignant progression of cancer. Our lab has created a mouse genetic system called MADM (Mosaic Analysis with Double Markers) that reveals cancer initiation and pre-malignant progression by generating sporadic tumor suppressor gene (TSG) mutated cells with unequivocal GFP labeling. Using MADM, we established a model for triple-negative breast cancer (TNBC) with p53 and BRCA1 mutations, which forms tumors at ~12 months of age. Taking advantage of the long latency and spatial resolution, we observed gradual expansion of mutant cells that resulted in GFP+, hyper-alveolarized but otherwise normal-looking mammary ducts at ~6 months of age. Serendipitously, we noticed prominent CD45+ immune aggregates in close proximity to hyper-alveolarized mutant ducts. Closer examination revealed that the enrichment of T and B cells within these immune aggregates, forming well-organized structures. Importantly, these B and T cell-enriched immune aggregates lack both B cell germinal centers and obvious T cell zones, suggesting that they are not classic tertiary lymphoid structures (TLS) and most likely are a novel type of immune aggregates. Furthermore, at the tumor stage, T/B cell-enriched immune aggregates were absent in the tumor core and infrequent at the tumor boundary, indicating a faltering of immune responses prior to malignancy. Finally, we performed a pilot GeoMx-based spatial profiling experiment, revealing that T cells in these aggregates displayed TCR activation and interferon-gamma signaling; B cells upregulated genes related to antigen-presentation; and both T and B cells upregulated immune-adhesion proteins. Taken together, all our preliminary data suggest that these T/B cell-aggregates play an important role in immune surveillance during the pre-malignant stage of TNBC. Therefore, we hypothesize that T and B cells form these aggregates through the upregulation of immune-adhesion proteins, and that B cells promote T cell responses by acting as antigen- presenting cells to control pre-malignant progression of TNBC. To test this hypothesis, in Specific Aim 1, we plan to perform hypothesis-driven spatial profiling, flow analysis, and multiplexed immunofluorescence staining to comprehensively understand the functional state of B + T cells and mutant/tumor cells in the MADM TNBC model at both pre-malignant and malignant stages; and in Specific Aim 2, we plan to gain functional insights of immune aggregates in controlling pre-malignant cells by disrupting the T/B aggregates in the MADM model. Findings from our proposed work will enable follow-up studies to functionally enhance immune surveillance to prevent TNBC before it turns malignant, and shed light on immunoprevention strategies for other cancer types.
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