Lymphatic Vessels Limits the Intratumoral T cell Repertoire in Melanoma

CD8⁺ T cell accumulation in tumors is essential for effective immunotherapy. However, the mechanisms of lymphocyte transit are still unclear. This study examined lymphatic vessel-mediated effector CD8⁺ T cell egress limits the accumulation of a broad repertoire of functional CD8⁺ T cells. To investigate the transcriptional changes in lymphatic endothelial cells (LECs) during tumor development, RNA was extracted from LECs sorted from naive skin and BPC murine (Tyr::Cre-ER, BRafV600E) melanomas and bulk RNA sequencing was performed. Naive skin LECs were collected from 3 mice and tumor-associated LECs were collected from 4 mice.

Comparative gene expression profiling of RNA sequencing was performed for tumor-retained, tumor-egressed, and circulating effector CD44⁺CD8⁺ T cells. YUMMER1.7 tumors were implanted into Kaede-Tg mice. On day 11, tumors were photoconverted, and on day 12, YUMMER1.7 tumors, draining lymph nodes, and spleens were harvested. Kaede red⁺ CD44⁺CD8⁺ T cells were sorted from YUMMER1.7 tumors (tumor-retained) and draining lymph nodes (tumor-egressed) along with CD44⁺CD8⁺ T cells from the spleens (circulating effector CD8⁺ T cells). These tissues were harvested and sorted from 4 mice. In addition, to further resolve the signals that direct T cell retention and egress, single-cell RNA sequencing analysis was performed on sorted, intratumoral CD44⁺CD8⁺ T cells. This dataset includes LEC and CD8⁺ T cell bulk RNA sequencing data, and CD8⁺ T cell single-cell RNA sequencing data.