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Tumor-derived lactic acid modulates activation and metabolic status of draining lymph node stroma

ABSTRACT: Communication between tumors and the stroma of tumor draining lymph nodes (TDLNs) exists before metastasis arises, altering structure and function of the TDLN niche. Transcriptional profiling of fibroblastic reticular cells (FRCs), the dominant stromal population of the LN, revealed reprogramming of these cells in immune related pathways, but also in fibroblast activation and mitochondrial function. However, tumor derived factors driving the changes in FRCs remained to be identified. Taking an unbiased approach, we show that lactic acid (LA), a metabolite released by cancer cells, is not only secreted by B16.F10 and 4T1 tumors in high amounts, but that it is also enriched in TDLNs. LA supports an upregulation of Pdpn and Thy1 and downregulation of Il7 in FRCs of TDLNs, making them akin to activated fibroblasts found at the primary tumor site. Furthermore, we show that tumor-derived LA alters mitochondrial function of FRCs of TDLNs. Thus, our results demonstrate a novel mechanism by which a tumor-derived metabolite connected with a low pH environment modulate the function of fibroblasts in TDLNs.

ORGANISM(S): Mus musculus

PROVIDER: GSE184300 | GEO | 2022/01/11

REPOSITORIES: GEO

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Project description:Background: While much progress has been accomplished in the understanding of radiation-induced immune effects in tumors, little is known regarding the mechanisms involved at the tumor draining lymph node (TDLN) level following tumor irradiation. The objective of this retrospective study was to assess the immune and biological changes arising in TDLN upon concurrent chemoradiotherapy of primary non-small cell lung cancer (NSCLC) tumors. Methods: Patients with proved localized (cN0M0) NSCLC, treated by radical surgery plus lymph node dissection with (CRT+) or without (CRT-) neoadjuvant chemoradiotherapy, whereby radiotherapy was targeted on the primary tumor with no significant incidental irradiation of the TDLN station (stations XI or X), were identified. Bulk RNA-Seq of TDLNs was performed and data were analyzed based on differential gene expression (DEG) and gene sets enrichment. Results: Sixteen patients were included and 25 TDLNs were analyzed: 6 patients in the CRT+ group (12 samples) and 10 patients in the CRT- group (13 samples). Overall, 1001 genes were differentially expressed between the two groups (CRT+ and CRT-). Analysis with g-profiler revealed that gene sets associated with antitumor immune response, inflammatory response, hypoxia, angiogenesis, epithelial mesenchymal transition and extra-cellular matrix remodeling were enriched in the CRT+ group, whereas only gene sets associated with B cells and B-cell receptor signaling were enriched in the CRT- group. Unsupervised dimensionality reduction identified two clusters of TDLNs from CRT+ patients, of which one cluster (cluster 1) exhibited higher expression of pathways identified as enriched in the overall CRT+ group in comparison to the CRT- group. In CRT+ cluster 1, 3 out of 3 patients had pathological complete response (pCR) or major complete response (MPR) to neoadjuvant CRT, whereas only 1 out of 3 patients in the other CRT+ cluster (cluster 2) experienced MPR and none exhibited pCR. Finally, pathway comparison to published data from pre-metastatic TDLNs uncovered similarities with CRT+ cluster 1. Conclusion: Neoadjuvant concurrent chemoradiotherapy of the primary tumor in N0 NSCLC patients is associated with distinct microenvironment and immunological patterns in TDLNs as compared to TDLNs from patients with non-irradiated tumors. Our data are in line with studies showing superiority of lymph node sparing irradiation of the primary tumor in the induction of systemic antitumor immunity.

Project description:Regulatory T (Treg) cells are vital for maintaining immune homeostasis and preventing autoimmunity, but represent a major barrier to robust cancer immunity as the tumor microenvironment (TME) actively recruits, activates, and promotes their differentiation1,2. Tumor cells have deregulated cellular metabolism leading to a metabolite-depleted, hypoxic, and acidic TME3. Highly glycolytic tumor infiltrating CD8 T cells are in direct competition with the tumor for glucose and oxygen which impairs their effector function4–6. In contrast, Treg cells maintain their high suppressive function within the TME7,8. Further, studies of in vitro induced and directly ex vivo Treg cells reveal a distinct metabolic profile compared to effector T cells9–11. Thus, we hypothesized that the altered metabolic landscape of the TME and the increased activity of intratumoral Treg cells are linked. Here we show Treg cells display heterogeneity in terms of their glucose metabolism and can engage an alternative metabolic pathway to maintain their high suppressive function and proliferation within the TME and other tissues. Tissue derived Treg cells (both at the steady state and under inflammatory conditions) show broad heterogeneity in their ability to take up glucose. However, glucose uptake correlates with poorer suppressive function and long-term functional stability, and culture of Treg cells in high glucose conditions decreased suppressive function. Treg cells under low glucose conditions upregulate genes associated with the uptake and metabolism of the glycolytic end-product lactic acid. Treg cells withstand high lactate conditions, and lactate treatment prevents the destabilizing effects of high glucose culture. Treg cells utilize lactate within the TCA cycle and generate phosphoenolpyruvate (PEP), a critical intermediate that can fuel intratumoral Treg cell proliferation in vivo. Using mice with a Treg cell-restricted deletion of lactate transporter Slc16a1 (MCT1) we show MCT1 is dispensable for peripheral Treg cell function but required intratumorally, resulting in slowed tumor growth and prolonged survival. These data support a model in which Treg cells are metabolically flexible such that they can utilize ‘alternative’ metabolites present in the TME to maintain their suppressive identity. Further, our studies support the notion that tumors avoid immune destruction not only by depriving effector T cells of essential nutrients, but also by metabolically supporting regulatory T cells.

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Tumor-derived lactic acid modulates activation and metabolic status of draining lymph node stroma

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