Cancer cells are embedded in the tumor microenvironment (TME), a complex ecosystem of stromal cells. Here, we present a 52,698-cell catalog of the TME transcriptome in human lung tumors at single-cell resolution, validated in independent samples where 40,250 additional cells were sequenced. By comparing with matching non-malignant lung samples, we reveal a highly complex TME that profoundly molds stromal cells. We identify 52 stromal cell subtypes, including novel subpopulations in cell types hitherto considered to be homogeneous, as well as transcription factors underlying their heterogeneity. For instance, we discover fibroblasts expressing different collagen sets, endothelial cells downregulating immune cell homing and genes coregulated with established immune checkpoint transcripts and correlating with T-cell activity. By assessing marker genes for these cell subtypes in bulk RNA-sequencing data from 1,572 patients, we illustrate how these correlate with survival, while immunohistochemistry for selected markers validates them as separate cellular entities in an independent series of lung tumors. Hence, in providing a comprehensive catalog of stromal cells types and by characterizing their phenotype and co-optive behavior, this resource provides deeper insights into lung cancer biology that will be helpful in advancing lung cancer diagnosis and therapy.

Summary Abnormal tumor vessels promote metastasis and impair chemotherapy. Hence, tumor vessel normalization (TVN) is emerging as anti-cancer treatment. Here, we show that tumor endothelial cells (ECs) have a hyper-glycolytic metabolism, shunting intermediates to nucleotide synthesis. EC haplo-deficiency or blockade of the glycolytic activator PFKFB3 did not affect tumor growth, but reduced cancer cell invasion, intravasation and metastasis by normalizing tumor vessels, which improved vessel maturation and perfusion. Mechanistically, PFKFB3 inhibition tightened the vascular barrier by reducing VE-cadherin endocytosis in ECs, and rendering pericytes more quiescent and adhesive (via upregulation of N-cadherin) through glycolysis reduction; it also lowered the expression of cancer cell adhesion molecules in ECs by decreasing NF-κB signaling. PFKFB3-blockade treatment also improved chemotherapy of primary and metastatic tumors.

In the original article, the surname of co-author Wouter Everaerts was spelled incorrectly as "Everaert." It appears correctly in this Correction, and the error has been corrected online.

Highlights d Single-cell RNA-seq reveals EC heterogeneity in choroidal neovascularization d ECs display metabolic transcriptome heterogeneity in the cell cycle and quiescence d Data integration with a genome-scale metabolic model identifies angiogenic targets d SQLE and ALDH18A1 are validated as metabolic angiogenic candidates

Several pathways modulating longevity and stress resistance converge on translation by targeting ribosomal proteins or initiation factors, but whether this involves modifications of ribosomal RNA is unclear. Here, we show that reduced levels of the conserved RNA methyltransferase NSUN5 increase the lifespan and stress resistance in yeast, worms and flies. Rcm1, the yeast homologue of NSUN5, methylates C2278 within a conserved region of 25S rRNA. Loss of Rcm1 alters the structural conformation of the ribosome in close proximity to C2278, as well as translational fidelity, and favours recruitment of a distinct subset of oxidative stress-responsive mRNAs into polysomes. Thus, rather than merely being a static molecular machine executing translation, the ribosome exhibits functional diversity by modification of just a single rRNA nucleotide, resulting in an alteration of organismal physiological behaviour, and linking rRNA-mediated translational regulation to modulation of lifespan, and differential stress response.

Highlights d We single-cell RNA-sequenced 56,771 endothelial cells (ECs) from human, mouse, and cultured lung tumor models d Tip ECs were resolved into migratory and basementmembrane remodeling phenotypes d Capillary and venous ECs expressed immunoregulatory gene signatures d Integrated analysis identified collagen modification as an angiogenic pathway

Immunotherapy (IO) has revolutionized the therapy landscape of non-small cell lung cancer (NSCLC), significantly prolonging the overall survival (OS) of advanced stage patients. Over the recent years IO therapy has been broadly integrated into the first-line setting of non-oncogene driven NSCLC, either in combination with chemotherapy, or in selected patients with PD-L1high expression as monotherapy. Still, a significant proportion of patients suffer from disease progression. A better understanding of resistance mechanisms depicts a central goal to avoid or overcome IO resistance and to improve patient outcome. We here review major cellular and molecular pathways within the tumor microenvironment (TME) that may impact the evolution of IO resistance. We summarize upcoming treatment options after IO resistance including novel IO targets (e.g. RIG-I, STING) as well as interesting combinational approaches such as IO combined with anti-angiogenic agents or metabolic targets (e.g. IDO-1, adenosine signaling, arginase). By discussing the fundamental mode of action of IO within the TME, we aim to understand and manage IO resistance and to seed new ideas for effective therapeutic IO concepts.

The role of phosphoglycerate dehydrogenase (PHGDH), a key enzyme of the serine synthesis pathway (SSP), in endothelial cells (ECs) remains poorly characterized. We report that mouse neonates with EC-specific PHGDH deficiency suffer lethal vascular defects within days of gene inactivation, due to reduced EC proliferation and survival. In addition to nucleotide synthesis impairment, PHGDH knockdown (PHGDH) caused oxidative stress, due not only to decreased glutathione and NADPH synthesis but also to mitochondrial dysfunction. Electron transport chain (ETC) enzyme activities were compromised upon PHGDH because of insufficient heme production due to cellular serine depletion, not observed in other cell types. As a result of heme depletion, elevated reactive oxygen species levels caused EC demise. Supplementation of hemin in PHGDH ECs restored ETC function and rescued the apoptosis and angiogenesis defects. These data argue that ECs die upon PHGDH inhibition, even without external serine deprivation, illustrating an unusual importance of serine synthesis for ECs.