Moreover, using the single-cell metabolic flux estimation algorithm scFEA, we discovered that the metabolic flux from pyruvate to lactate in apCAFs was higher compared to other fibroblasts subpopulations in HNSCC (Figure 7G), NPC (Figure 7H), and BRCA (Figure 7I) (Supplementary Table 15). Here, NPC1 is linked to head and neck squamous cell carcinoma.