Development of Lymph Node-like Vasculature and Tertiary Lymphoid Structures in Tumors

The presence of lymph node-like vasculature in tumors, characterized by expression of peripheral node addressin (PNAd) and chemokine CCL21, is correlated with T cell infiltration and positive prognosis in breast cancer and melanoma patients. However, the mechanisms controlling the development of lymph node-like vasculature, and how it contributes to a beneficial outcome for cancer patients, are unknown. Here we demonstrate that lymph node-like PNAd+ CCL21+ vasculature develops in murine models of melanoma and lung carcinoma growing in multiple anatomic locations. PNAd expression on tumor-associated endothelium and CCL21 expression by tumor-associated endothelial cells and gp38+ fibroblasts did not require lymphotoxin-beta receptor (LTβR) signaling. Instead, it was controlled by a novel mechanism dependent on tumor infiltrating effector lymphocytes that secreted lymphotoxin-alpha (LTα3 ), which signaled through TNF receptors. In intraperitoneal (i.p.) tumors, CCL21 was also controlled by IFNγ. While effector CD8 T cells induced LN-like vasculature in both subcutaneous (s.c.) and i.p. tumors, NK cells only promoted its development in s.c. tumors. Portions of LN-like vasculature in i.p. but not s.c. tumors were also associated with a tertiary lymphoid structure containing large aggregates of B cells, T cells and dendritic cells that appeared to be organized by a stromal network of gp38+ fibroblasts. The gp38+ cells in i.p. tumors expressed high levels of chemokine CXCL13 and B cell survival factor APRIL, which may be important for recruiting and maintaining B cells in the tertiary lymphoid structure. Importantly, intratumoral LN-like vasculature enabled the infiltration of adoptively transferred naïve T cells. These T cells underwent activation and effector cell differentiation in the tumor, and significantly delayed s.c. tumor outgrowth. However, tertiary lymphoid structures were not required for intratumoral activation of naïve T cells. These results establish LN-like vasculature as both a consequence of and key contributor to anti-tumor immunity.