T cell egress via lymphatic vessels is tuned by antigen encounter and limits tumor control.

Antigen-specific CD8+ T cell accumulation in tumors is a prerequisite for effective immunotherapy, and yet the mechanisms of lymphocyte transit are not well defined. Here we show that tumor-associated lymphatic vessels control T cell exit from tumors via the chemokine CXCL12, and intratumoral antigen encounter tunes CXCR4 expression by effector CD8+ T cells. Only high-affinity antigen downregulates CXCR4 and upregulates the CXCL12 decoy receptor, ACKR3, thereby reducing CXCL12 sensitivity and promoting T cell retention. A diverse repertoire of functional tumor-specific CD8+ T cells, therefore, exit the tumor, which limits the pool of CD8+ T cells available to exert tumor control. CXCR4 inhibition or loss of lymphatic-specific CXCL12 boosts T cell retention and enhances tumor control. These data indicate that strategies to limit T cell egress might be an approach to boost the quantity and quality of intratumoral T cells and thereby response to immunotherapy.

The tumor-draining lymph node as a reservoir for systemic immune surveillance.

Early in solid tumor development, antigens are presented in tumor-draining lymph nodes (tdLNs), a process that is necessary to set up immune surveillance. Recent evidence indicates that tdLNs fuel systemic tumor-specific T cell responses which may halt cancer progression and facilitate future responses to immunotherapy. These protective responses, however, are subject to progressive dysfunction exacerbated by lymph node (LN) metastasis. We discuss emerging preclinical and clinical literature indicating that the tdLN is a crucial reservoir for systemic immunity that can potentiate immune surveillance. We also discuss the impact of LN metastasis and argue that a better understanding of the relationship between LN metastasis and systemic immunity will be necessary to direct regional disease management in the era of immunotherapy.

Transcriptional Isoforms of NAD+ kinase regulate oxidative stress resistance and melanoma metastasis.

Metastasizing cancer cells encounter a multitude of stresses throughout the metastatic cascade. Oxidative stress is known to be a major barrier for metastatic colonization, such that metastasizing cancer cells must rewire their metabolic pathways to increase their antioxidant capacity. NADPH is essential for regeneration of cellular antioxidants and several NADPH-regenerating pathways have been shown to play a role in metastasis. We have found that metastatic melanoma cells have increased levels of both NADPH and NADP+ suggesting increased de novo biosynthesis of NADP+. De novo biosynthesis of NADP+ occurs through a single enzymatic reaction catalyzed by NAD+ kinase (NADK). Here we show that different NADK isoforms are differentially expressed in metastatic melanoma cells, with Isoform 3 being specifically upregulated in metastasis. We find that Isoform 3 is more potent in expanding the NADP(H) pools, increasing oxidative stress resistance and promoting metastatic colonization compared to Isoform 1. We have found that Isoform 3 is transcriptionally upregulated by oxidative stress through the action of NRF2. Together, our work presents a previously uncharacterized role of NADK isoforms in oxidative stress resistance and metastasis and suggests that NADK Isoform 3 is a potential therapeutic target in metastatic disease.

Lymphatic vessel transit seeds cytotoxic resident memory T cells in skin draining lymph nodes.

Lymphatic transport shapes the homeostatic immune repertoire of lymph nodes (LNs). LN-resident memory T cells (TRMs) play an important role in site-specific immune memory, yet how LN TRMs form de novo after viral infection remains unclear. Here, we tracked the anatomical distribution of antiviral CD8+ T cells as they seeded skin and LN TRMs using a model of vaccinia virus-induced skin infection. LN TRMs localized to the draining LNs (dLNs) of infected skin, and their formation depended on the lymphatic egress of effector CD8+ T cells from the skin, already poised for residence. Effector CD8+ T cell transit through skin was required to populate LN TRMs in dLNs, a process reinforced by antigen encounter in skin. Furthermore, LN TRMs were protective against viral rechallenge in the absence of circulating memory T cells. These data suggest that a subset of tissue-infiltrating CD8+ T cells egress from tissues during viral clearance and establish a layer of regional protection in the dLN basin.

Lymphatic vessel transit seeds precursors to cytotoxic resident memory T cells in skin draining lymph nodes.

Resident memory T cells (TRM) provide rapid, localized protection in peripheral tissues to pathogens and cancer. While TRM are also found in lymph nodes (LN), how they develop during primary infection and their functional significance remains largely unknown. Here, we track the anatomical distribution of anti-viral CD8+ T cells as they simultaneously seed skin and LN TRM using a model of skin infection with restricted antigen distribution. We find exquisite localization of LN TRM to the draining LN of infected skin. LN TRM formation depends on lymphatic transport and specifically egress of effector CD8+ T cells that appear poised for residence as early as 12 days post infection. Effector CD8+ T cell transit through skin is necessary and sufficient to populate LN TRM in draining LNs, a process reinforced by antigen encounter in skin. Importantly, we demonstrate that LN TRM are sufficient to provide protection against pathogenic rechallenge. These data support a model whereby a subset of tissue infiltrating CD8+ T cells egress during viral clearance, and establish regional protection in the draining lymphatic basin as a mechanism to prevent pathogen spread.