MCT4-Associated Lactate Export Defines Myeloid Metabolic Reprogramming during Head and Neck Cancer Progression

Head and neck squamous cell carcinoma (HNSCC) develops within a metabolically remodeled tumor microenvironment, yet how metabolic programs evolve across specific cell populations during tumor progression remains poorly understood. We integrated single-cell RNA-sequencing data from five HNSCC cohorts comprising 645,351 cells from 114 patients and inferred metabolic flux using single-cell Flux Estimation Analysis (scFEA). Myeloid cells showed the highest and most consistent metabolic allocation to lactate export among major cell types. In ten patients with paired normal mucosa and carcinoma, myeloid lactate-export allocation increased from 1.72% to 3.31% of total inferred metabolic flux, with an increase in every patient. SPP1+ macrophages showed the highest lactate-export allocation in carcinoma. Lactate export was predominantly associated with MCT4/SLC16A3. In carcinoma, myeloid SLC16A3 expression exceeded SLC16A1 by 17-fold, and CPTAC-HNSCC confirmed tumor enrichment of MCT4 protein. Together, these findings identify increased MCT4-associated lactate export as a prominent feature of myeloid metabolic reprogramming during HNSCC progression.