library_construction_protocol: Total RNA was extracted from frozen B16-OVA tumors lysed by TissueLyser II (QIAGEN) using phenol-chloroform extraction method with Trizol (Invitrogen) and Isopropanol (XILONG). The quality of the total RNA and the sample RNA concentration were determined by using the Bioanalyzer 2100 (Agilent). 1 µg of total RNA was used to build mRNA libraries using MGIEasy RNA Library Prep kit (MGI, China) following the manufacturers' instructions.