Metabolite-driven dysfunction of intratumoral tertiary lymphoid structures: single-cell and spatial omics...

Intratumoral tertiary lymphoid structures (TLSs) are increasingly recognized as spatially organized immune niches associated with favorable prognosis and improved responses to immune checkpoint blockade. Yet TLS positivity is not synonymous with durable antitumor immunity. Many tumors contain lymphoid aggregates that are anatomically visible but developmentally arrested, poorly vascularized, depleted of germinal center-like activity, or uncoupled from effective plasma-cell and T-cell output. This discrepancy has shifted the field from a binary TLS-positive/TLS-negative view toward a state-based interpretation of TLS competence. Here, we propose that metabolite-driven remodeling of the tumor microenvironment is a major cause of intratumoral TLS failure. However, the current literature lacks a cell-type- and spatially resolved framework linking individual metabolites to disruption of defined TLS modules and distinguishing early developmental deviation from later functional collapse. Single-cell and spatial omics now show that productive TLSs depend on coordinated interactions among stromal organizer cells, HEV-like endothelium, mature dendritic cells, T follicular helper-like cells, B-cell lineages, plasma cells, and stem-like or progenitor exhausted T cells. These cellular modules are vulnerable to oxygen limitation, nutrient competition, lactate accumulation, extracellular adenosine, tryptophan catabolism, vascular stress, and suppressive B-cell states. A central goal of this review is to establish a hierarchy of mechanistic certainty across the metabolic drivers of TLS dysfunction. Tryptophan metabolism currently has the strongest direct TLS-specific spatial and perturbational evidence, whereas lactate, adenosine, hypoxia-associated vascular stress, lipid stress, and nucleotide metabolism are supported mainly by convergent immunometabolic and spatial evidence. On this basis, we outline biomarker-guided strategies to restore TLS competence, including inhibition of tumor-derived tryptophan metabolism to promote TLS maturation and enhance anti-PD-1 efficacy.