Since CD44- Epi_C1 clusters were located closer to the interior of the tumor, away from infiltrated immune cells and stromal cells, compared to CD44+ Epi_C1 clusters (Fig. 6d and Supplementary Fig S3b), we speculated that PTN from CD44- Epi_C1 may interact with other cell clusters rather than TANs or CAFs at the tumor leading edge. The gene discussed is CD44; the disease is neoplasm.