CCL19-producing fibroblasts promote tertiary lymphoid structure formation enhancing anti-tumor IgG response in colorectal cancer liver metastasis

Tertiary lymphoid structures (TLSs) are associated with enhanced immunity in tumors. However, their formation and functions in colorectal cancer liver metastasis (CRLM) remain unclear. Here, we reveal that intra- and peri-tumor mature TLSs (TLS+) are associated with improved clinical outcomes than TLS− tumors. Using single-cell-RNA-sequencing and spatial-enhanced-resolution-omics-sequencing (Stereo-seq), we reveal that TLS+ tumors are enriched with IgG+ plasma cells (PCs), while TLS− tumors are characterized with IgA+ PCs. By generating TLS-associated PC-derived monoclonal antibodies in vitro, we show that TLS-PCs secrete tumor-targeting antibodies. As the proof-of-concept, we demonstrate the anti-tumor activities of TLS-PC-mAb6 antibody in humanized mouse model of colorectal cancer. We identify a fibroblast lineage secreting CCL19 that facilitates lymphocyte trafficking to TLSs. CCL19 treatment promotes TLS neogenesis and prevents tumor growth in mice. Our data uncover the central role of CCL19+ fibroblasts in TLS formation, which in turn generates therapeutic antibodies to restrict CRLM. [Display omitted] •Both intra- and peri-tumor TLSs predict better outcomes of CRLM after surgery•TLSs are associated with enhanced local anti-tumor IgG response in CRLM•TLS-associated mAb6 antibody inhibits human CRC growth in humanized mice•Fibroblast-derived CCL19 promotes B cell recruitment and TLS formation in CRLM Zhang et al. uncover the landscape of TLSs in CRLM using single-cell multi-omics sequencing approaches. They show that CCL19-producing fibroblasts promote TLS formation, which in turn generates tumor reactive IgG antibodies in situ to restrict CRLM, providing potential therapeutic targets.