Tumor tissues were harvested and enzymatically digested with the mouse tumor dissociation kit (Miltenyi) and the subjected to agitation and rotation at 37℃ according the manufacturer's protocol. Cell suspensions were then filtered through a 70 μm filter (Falcon) and wash with FACS buffer containing 1% BSA (Sigma). For scRNAseq experiment of EP2/4 antagonists treated mice, live CD45+ cells were sorted from the dissected LLC1 tumor using BD FACS Aria3. For scRNAseq experiment of Treg-depleted mice, total cells from the dissected LLC1 tumor were used. Single cells were lysed in droplets using the 10X Chromium instrument. Reverse transcription was performed in droplet. library construction was performed according to the 10X Chromium Single Cell 3' Reagent Kits v3.1 User Guide Rev C