To determine a cell source of ARG1 and ARG2 expression, we explored the single-cell RNA sequencing (scRNA-seq) data from 10 astrocytoma samples (33) and checked the gene expression in various cell populations from the tumors using the SingleCell data portal (https://singlecell.broadinstitute.org/). The gene discussed is ARG1; the disease is astrocytoma (excluding glioblastoma).