library_construction_protocol: Fresh primary tumors of buccal mucosa were minced, washed with serum-free DMEM (GIBCO), and dissociated using a Human Tumor Dissociation Kit (Miltenyi Biotec) according to manufacturer guidelines. Cell suspension was filtered using a 70 mm filter (ThermoFisher Scientific), and red blood cells were removed with 1× RBC Lysis Buffer (BD Biosciences). Cell suspensions were loaded on a Chromium X Instrument (10X Genomics) to generate single-cell gel beads in emulsions (GEMs). scRNA-seq libraries were prepared using Chromium Single cell 3' GEM, Library, & Gel beads kit (10X Genomics).