CXCL9 and CXCL13 shape endometrial cancer immune-activated microenvironment via tertiary lymphoid structure formation.

Immune checkpoint inhibitor (ICI) therapy has been successfully applied to various cancers; however, not all patients respond to ICI therapy. Tumors with an immune-activated environment are highly responsive to ICIs. To identify the cells and molecules essential to the formation of an immune-activated cancer microenvironment, we focused on the tertiary lymphoid structure (TLS) and performed histological and genomic analyses using endometrial cancer material. In the high immunogenic group, numerous TLSs were observed, and CXCL9 and CXCL13 expression was markedly increased. CXCL9-positive antigen-presenting and CXCL13-positive follicular dendritic cells were distributed in the T- and B-cell zones of TLSs, respectively. A group of molecules whose expression was upregulated along with CXCL9 and CXCL13 expression was strongly associated with cellular immunity. These results suggest that CXCL9-expressing antigen-presenting cells and CXCL13-expressing follicular dendritic cells coordinately shape the immune-activated microenvironment through TLS formation. The current findings will contribute to a better understanding of the mechanisms underlying the activated cancer immune microenvironment, thereby advancing the field of precision cancer medicine.